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1
Fu, Ping, Hong Lei Zhang i Chuan Sheng Wang. "Finite-Element Analysis of Rotor in the Rubber Continuous Plasticator". Key Engineering Materials 561 (lipiec 2013): 174–77. http://dx.doi.org/10.4028/www.scientific.net/kem.561.174.
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The three-dimensional flow fields produced by the modular dual-rotor of rubber continuous plasticator were numerically simulated and analyzed by using ADINA, the FEM simulation software. So the velocity field distribution of each rotor element was shown by the simulations. Through the analysis, the double rotors rotated inward had high efficiency of pumping and plasticization. The rubber compound was subjected to the strong shearing action; squeezing action and stretch effect in the rubber plasticate process. The simulation calculation had great significance for the rotor optimizing design.
2
Pacholczyk, Michał, i Dariusz Karkosiński. "Parametric Study on a Performance of a Small Counter-Rotating Wind Turbine". Energies 13, nr 15 (29.07.2020): 3880. http://dx.doi.org/10.3390/en13153880.
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A small Counter-Rotating Wind Turbine (CRWT) has been proposed and its performance has been investigated numerically. Results of a parametric study have been presented in this paper. As parameters, the axial distance between rotors and a tip speed ratio of each rotor have been selected. Performance parameters have been compared with reference to a Single Rotor Wind Turbine (SRWT). Simulations were carried out with Computational Fluids Dynamics (CFD) solver and a Large Eddy Scale approach to model turbulences. An Actuator Line Model has been chosen to represent rotors in the computational domain. Summing up the results of simulation tests, it can be stated that when constructing a CRWT turbine, rotors should be placed at a distance of at least 0.5 D (where D is rotor outer diameter) or more. One can then expect a noticeable power increase compared to a single rotor turbine. Placing the second rotor closer than 0.5 D guarantees a significant increase in power, but in such configurations, dynamic interactions between the rotors are visible, resulting in fluctuations in torque and power. Dynamic interactions between rotor blades above 0.5 D are invisible.
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Huang, Yong Yu, Qiu Yun Mo, Xu Zhang i Zu Peng Zhou. "Numerical Simulations of Spherical Vertical-Axis Wind Rotor". Applied Mechanics and Materials 291-294 (luty 2013): 456–60. http://dx.doi.org/10.4028/www.scientific.net/amm.291-294.456.
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In this paper, the effects of the shape of three types of the blade on power coefficient of Savonius rotors are studied by simulating the model using numerical simulation under the same conditions. For this purpose, three spherical rotors with different configurations but identical number of stages and blades, aspect ratio and overlap keeping the identical projected area of each rotor are constructed. The geometries of blade of the three rotors are a plane, a semi-circle and a quarter of sphere. The building data are calculated on the basis of the nominal wind velocity V= 10m/s and the speed ratio λ= 0.3 with an industrial flow simulation code (ANSYS-Fluent). The result shows that the rotor with semicircular blades has a higher value of power coefficient in comparison with other rotors.
4
Mao, Xiaochen, i Bo Liu. "Numerical investigation of tip clearance size effect on the performance and tip leakage flow in a dual-stage counter-rotating axial compressor". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, nr 3 (15.02.2017): 474–84. http://dx.doi.org/10.1177/0954410016638878.
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Based on a validation of the numerical methods with an experiment, numerical simulations are carried out to study the effect of tip clearance size on the performance and tip leakage flow in a dual-stage counter-rotating axial compressor. The predicted results showed that the variation of the tip clearance size in rotor2 has a more significant impact on the overall performance and stall margin of the compressor. In addition, the impact of the tip clearance size effect is mainly on the rotor with the tip clearance size variation. The variation of the tip clearance size in rotor2 almost has no influence on the performance of rotor1, while the performance of rotor2 is increased about 1.37% at near-stall point when the tip clearance size of rotor1 is increased to 1.0 mm from 0.5 mm. At peak efficiency condition, the tip clearance size variation in rotor1 has remarkable influence on the tip leakage vortex intensity, onset point and trajectory in rotor1, but has little influence on those in rotor2. However, the tip clearance size variation in rotor2 has remarkable effect on those in both rotors. Different tip clearance size combination schemes can impact the stall-free characteristic in the counter-rotating axial compressor.
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Fletcher, T. M., i R. E. Brown. "Modelling the interaction of helicopter main rotor and tail rotor wakes". Aeronautical Journal 111, nr 1124 (październik 2007): 637–43. http://dx.doi.org/10.1017/s0001924000004814.
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Abstract The mutual interaction between the main rotor and tail rotor wakes is central to some of the most problematic dynamic phenomena experienced by helicopters. Yet achieving the ability to model the growth and propagation of helicopter rotor wakes with sufficient realism to capture the details of this interaction has been a significant challenge to rotorcraft aerodynamicists for many decades. A novel computational fluid dynamics code tailored specifically for rotorcraft applications, the vorticity transport model, has been used to simulate the interaction of the rotors of a helicopter with a single main rotor and tail rotor in both hover and low-speed quartering flight, and with the tail rotor rotating both top-forward and top-aft. The simulations indicate a significant level of unsteadiness in the performance of both main and tail rotors, especially in quartering flight, and a sensitivity to the direction of rotation of the tail rotor. Although the model thus captures behaviour that is similar to that observed in practice, the challenge still remains to integrate the information from high fidelity simulations such as these into routine calculations of the flight dynamics of helicopters.
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Lei, Yao, i Rongzhao Lin. "Effect of wind disturbance on the aerodynamic performance of coaxial rotors during hovering". Measurement and Control 52, nr 5-6 (25.04.2019): 665–74. http://dx.doi.org/10.1177/0020294019834961.
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The ability to resist the effect of wind disturbance is vital for micro air vehicles. As the most compact rotor configuration for micro air vehicles, coaxial rotors will be the preferred choice for this type of devices. In this paper, the aerodynamic performance of the coaxial rotors considering the wind gust is presented with both experiments and simulations. First, effect of wind disturbances on the micro air vehicles flight was introduced. Then, low-speed wind tunnel tests were performed on a coaxial rotor with a spacing 0.39 R to obtain the performance in both horizontal and vertical wind of 0–5 m/s with the revolutions per minute ranging from 1500 to 2400. Finally, computational fluid dynamics simulations, as a means of visualizing the flow field to compensate the intuition of the experimental data, were applied by using the sliding mesh to capture the detailed interference of flow field with the distributions of streamline and velocity vector. Compared with wind tunnel tests, simulation results were highly consistent with experiments that allow to capture the flow details around the rotor tip effectively. In addition, the aerodynamic performance was deteriorated by vortices moving or deforming around the blade tip. Also, coaxial rotors can effectively resist the wind disturbance in the horizontal direction while the rotor performance was found to be declined in the vertical wind.
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Lei, Yao, Yiqiang Ye i Zhiyong Chen. "Horizontal Wind Effect on the Aerodynamic Performance of Coaxial Tri-Rotor MAV". Applied Sciences 10, nr 23 (1.12.2020): 8612. http://dx.doi.org/10.3390/app10238612.
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The coaxial Tri-rotor micro air vehicle (MAV) is composed of three coaxial rotors where the aerodynamic characteristics of is complicated in flight especially when the wind effect is introduced. In this paper, the hovering performance of a full-scale coaxial Tri-rotor MAV is analyzed with both the simulations and wind tunnel experiments. Firstly, the wind effect on the aerodynamic performance of coaxial Tri-rotor MAV is established with different rotor speed (1500–2300 rpm) and horizontal wind (0–4 m/s). Secondly, the thrust and power consumption of coaxial Tri-rotor (L/D = 1.6) were obtained with low-speed wind tunnel experiments. Furthermore, the streamline distribution, pressure distribution, velocity contour and vortex distribution with different horizontal wind conditions are obtained by numerical simulations. Finally, combining the experiment results and simulation results, it is noted that the horizontal wind may accelerate the aerodynamic coupling, which resulting in the greater thrust variation up to 9% of the coaxial Tri-rotor MAV at a lower rotor speed. Moreover, the aerodynamic performance is decreased with more power consumption at higher rotor speed where the wind and the downwash flow are interacted with each other. Compared with no wind flow, the shape of the downwash flow and the deformation of the vortex affect the power loading and figure of metric accordingly.
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Sun, Zhenye, Wei Jun Zhu, Wen Zhong Shen, Wei Zhong, Jiufa Cao i Qiuhan Tao. "Aerodynamic Analysis of Coning Effects on the DTU 10 MW Wind Turbine Rotor". Energies 13, nr 21 (3.11.2020): 5753. http://dx.doi.org/10.3390/en13215753.
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The size of wind turbine rotors is still rapidly increasing, though many technical challenges emerge. Novel rotor designs emerge to satisfy this up-scale trend, such as downwind load-aligned concepts, which orients the loads along the blade spanwise to greatly decrease the bending moments at the root. As the studies on the aerodynamics of these rotor concepts using 3D body-fitted mesh are very limited, this paper establishes different cone configurations based on the DTU 10 MW reference rotor and conducts a series of simulations. It is found that the cone angle and the distance from the blade section to the tip vortex are two deterministic factors on conning. Upwind rotors have larger power output, less thrust, smaller wake deficit, and smaller influencing area than downwind rotors of the same size, which provides superior aerodynamic priority and benefits wind farm design. The largest upwind cone angle of 14.03°, among the cases studied, leads to the highest torque to thrust ratio which is 3.63% higher than the baseline rotor. The downwind load-aligned rotor, designed to reduce the blade root bending moments at large wind speed, performs worse at the present simulation conditions than an upwind rotor of the same size.
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Benti, Gudeta Berhanu, Rolf Gustavsson i Jan-Olov Aidanpää. "Speed-Dependent Bearing Models for Dynamic Simulations of Vertical Rotors". Machines 10, nr 7 (10.07.2022): 556. http://dx.doi.org/10.3390/machines10070556.
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Many dynamic simulations of a rotor with a journal bearing employ non-linear fluid-film lubrication models and calculate the bearing coefficients at each time step. However, calculating such a simulation is tedious and computationally expensive. This paper presents a simplified dynamic simulation model of a vertical rotor with tilting pad journal bearings under constant and variable (transient) rotor spin speed. The dynamics of a four-shoes tilting pad journal bearing are predefined using polynomial equations prior to the unbalance response simulations of the rotor-bearing system. The Navier–Stokes lubrication model is solved numerically, with the bearing coefficients calculated for six different rotor speeds and nine different eccentricity amplitudes. Using a MATLAB inbuilt function (poly53), the stiffness and damping coefficients are fitted by a two-dimensional polynomial regression and the model is qualitatively evaluated for goodness-of-fit. The percentage relative error (RMSE%) is less than 10%, and the adjusted R-square (Radj2) is greater than 0.99. Prior to the unbalance response simulations, the bearing parameters are defined as a function of rotor speed and journal location. The simulation models are validated with an experiment based on the displacements of the rotor and the forces acting on the bearings. Similar patterns have been observed for both simulated and measured orbits and forces. The resultant response amplitudes increase with the rotor speed and unbalanced magnitude. Both simulation and experimental results follow a similar trend, and the amplitudes agree with slight deviations. The frequency content of the responses from the simulations is similar to those from the experiments. Amplitude peaks, which are associated with the unbalance force (1 × Ω) and the number of pads (3 × Ω and 5 × Ω), appeared in the responses from both simulations and experiments. Furthermore, the suggested simulation model is found to be at least three times faster than a classical simulation procedure that used FEM to solve the Reynolds equation at each time step.
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Lei, Yao, i Mingxin Cheng. "Aerodynamic performance of a Hex-rotor unmanned aerial vehicle with different rotor spacing". Measurement and Control 53, nr 3-4 (31.01.2020): 711–18. http://dx.doi.org/10.1177/0020294019901313.
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In this paper, an attempt was made to obtain the aerodynamic performance of a Hex-rotor unmanned aerial vehicle with different rotor spacing. The hover efficiency of the Hex-rotor unmanned aerial vehicle is analyzed by both experimental tests and numerical simulations. First, a series of index to characterize the aerodynamic performance of the Hex-rotor unmanned aerial vehicle are analyzed theoretically, and then both tests and simulations on a Hex-rotor unmanned aerial vehicle with different rotor spacing ratio ( i = 0.50, 0.56, 0.63, 0.71, 0.83) were presented in details. For a custom-designed test platform, the thrust, power loading and hover efficiency of the Hex-rotor unmanned aerial vehicle were obtained in this paper. Finally, computational fluid dynamics simulations are performed to obtain the streamline distributions of the flow field, pressure and velocity contour of the Hex-rotor unmanned aerial vehicle. Results show that the aerodynamic performance of the Hex-rotor unmanned aerial vehicle is varied by changing the rotor spacing. Specifically, the smaller rotor spacing may improve the aerodynamic performance of the Hex-rotor unmanned aerial vehicle by increasing the rotor interferences. In the meantime, the effects of mutual interference between the rotors are gradually reduced with the increase of the rotor spacing. Moreover, the uniformity of the streamline distribution, the shape and the symmetry of the vortex are necessary conditions for the Hex-rotor unmanned aerial vehicle to generate a larger thrust. It was also noted that the thrust increased by 5.61% and the overall efficiency increased by about 8.37% at i = 0.63 for the working mode (2200 r/min), which indicated that the rotor spacing ratio at i = 0.63 obtained a best aerodynamic performance.
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Allen, C. B. "Multigrid multiblock hovering rotor solutions". Aeronautical Journal 108, nr 1083 (maj 2004): 255–61. http://dx.doi.org/10.1017/s000192400000511x.
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AbstractThe effect of multigrid acceleration implemented within an upwind-biased Euler method for hovering rotor flows is presented. Previous work has considered multigrid convergence for structured single block rotor solutions. However, for forward flight simulation a multiblock approach is essential and, hence, the flow-solver has been extended to include multigrid acceleration within a multiblock solver. The requirement to capture the vortical wake development over several turns means a long numerical integration time is required for hovering rotors, and the solution (wake) away from the blade is significant. Hence, the solution evolution and convergence is different to a fixed wing case where convergence depends primarily on propagating errors away from the surface as quickly as possible, and multigrid acceleration is shown here to be less effective for hovering rotor flows. Previous single block simulations demonstrated that a simple multigridV-cycle was the most effective, smoothing in the decreasing mesh density direction only, with a relaxed trilinear prolongation operator. This is also shown to be the case for multiblock simulations. Results are presented for multigrid computations with 2, 3, and 4, mesh levels, and a CPU reduction of approximately 80% is demonstrated for 4 mesh levels.
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Liu, Cong, Baiqing Li, Zhiqiang Wei, Zongwei Zhang, Zezhong Shan i Yu Wang. "Effects of Wake Separation on Aerodynamic Interference Between Rotors in Urban Low-Altitude UAV Formation Flight". Aerospace 11, nr 11 (22.10.2024): 865. http://dx.doi.org/10.3390/aerospace11110865.
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In recent years, unmanned aerial vehicle (UAV) formation flight has become an effective strategy for urban air mobility (UAM). However, close rotor separation during formation flight leads to complex aerodynamic interference between rotors, significantly affecting UAV flight performance and operational safety. This study systematically examines the effects of axial and lateral rotor separation on the rotor’s thrust performance through wind tunnel experiments. The tests simulate horizontal, vertical, and hovering states by generating relative airflow in the wind tunnel, focusing primarily on the thrust coefficient changes of the bottom rotor at various separations. The results are compared with a single rotor operating under the same conditions without wake interference. Additionally, computational fluid dynamics (CFD) simulations using the Fluent software were conducted to investigate the effect of wake interactions by analyzing the velocity flow field between the two rotors in different separations. Both the experimental and simulation results demonstrate that rotor aerodynamic performance is notably influenced by wake interactions. Under hovering and vertical states, substantial aerodynamic interference occurs in the region directly beneath the top rotor, within 1D ≤ Z ≤ 3D. This interference gradually diminishes as the rotor separation increases. Additionally, the thrust coefficient of the bottom rotor decreases with increasing flight speed due to the wake, and at higher flight speeds, the wake tends to contract. When the lateral separation is X = 0D, the mid-sectional flow field of the two rotors exhibits symmetry; however, with lateral separation, the symmetry of the bottom rotor’s wake velocity field is disrupted. During the horizontal flight, the rotor wake tilts backward due to the relative airflow, and the extent of this influence is governed by both rotor rotational speed and flight velocity. Therefore, when UAVs operate in formation, it is crucial to account for these factors affecting aerodynamic performance, and rotor separation must be optimized to enhance flight safety and efficiency.
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Lei, Yao, i Hengda Wang. "Aerodynamic Optimization of a Micro Quadrotor Aircraft with Different Rotor Spacings in Hover". Applied Sciences 10, nr 4 (13.02.2020): 1272. http://dx.doi.org/10.3390/app10041272.
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In order to study the aerodynamic performance of the quadrotor with different rotor spacings in hover, experiments were performed together with numerical simulations. For experimental study, an experimental platform was designed to measure the thrust and power consumption of the quadrotor with different rotor spacings (L/R = 2.2, 2.6, 3.0, 3.2, 3.6, and 4.0), and to attempt to find out the optimal rotor configuration which makes the quadrotor have the best aerodynamic performance. In addition, the pressure distribution, vorticity of the blade tip, and velocity vector of quadrotor in the flow field were obtained by Computational Fluid Dynamics (CFD) method to visually analyze the aerodynamic interference between adjacent rotors. By the comparison of experimental results and numerical simulations, the final results show that the aerodynamic performance of the quadrotor varies obviously with the change of rotor spacing, and it has a negative impact on hover efficiency if rotor spacing is too much small or large. The rotors pacing at L/R = 3.6 with larger thrust and smaller power is considered to be the best aerodynamic configuration for the quadrotor with better aerodynamic characteristics. Furthermore, compared with the isolated rotor, moderate aerodynamic interference is proved to help improve the aerodynamic performance of the quadrotor with a larger thrust, especially for a rotor spacing at L/R = 3.6.
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Nalim, M. R., i D. E. Paxson. "A Numerical Investigation of Premixed Combustion in Wave Rotors". Journal of Engineering for Gas Turbines and Power 119, nr 3 (1.07.1997): 668–75. http://dx.doi.org/10.1115/1.2817036.
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Wave rotor cycles that utilize premixed combustion processes within the passages are examined numerically using a one-dimensional CFD-based simulation. Internal-combustion wave rotors are envisioned for use as pressure-gain combustors in gas turbine engines. The simulation methodology is described, including a presentation of the assumed governing equations for the flow and reaction in the channels, the numerical integration method used, and the modeling of external components such as recirculation ducts. A number of cycle simulations are then presented that illustrate both turbulent-deflagration and detonation modes of combustion. Estimates of performance and rotor wall temperatures for the various cycles are made, and the advantages and disadvantages of each are discussed.
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Franz, Daniel, Maximilian Schneider, Michael Richter i Stephan Rinderknecht. "Thermal Behavior of a Magnetically Levitated Spindle for Fatigue Testing of Fiber Reinforced Plastic". Actuators 8, nr 2 (3.05.2019): 37. http://dx.doi.org/10.3390/act8020037.
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This article discusses the critical thermal behavior of a magnetically levitated spindle for fatigue testing of cylinders made of fiber reinforced plastic. These cylinders represent the outer-rotor of a kinetic energy storage. The system operates under vacuum conditions. Hence, even small power losses in the rotor can lead to a high rotor temperature. To find the most effective way to keep the rotor temperature under a critical limit in the existing system, first, transient electromagnetic finite element simulations are evaluated for the active magnetic bearings and the electric machine. Using these simulations, the power losses of the active components in the rotor can be derived. Second, a finite element simulation characterizes the thermal behavior of the rotor. Using the power losses calculated in the electromagnetic simulation, the thermal simulation provides the temperature of the rotor. These results are compared with measurements from an experimental spindle. One effective way to reduce rotational losses without major changes in the hardware is to reduce the bias current of the magnetic bearings. Since this also changes the characteristics of the magnetic bearings, the dynamic behavior of the rotor is also considered.
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Kim, Taewung, i Taehyung Kim. "Optimization of Hammer Peening Process for Gas Turbine Rotor Straightening". Machines 10, nr 10 (19.10.2022): 950. http://dx.doi.org/10.3390/machines10100950.
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Some rotors are bent permanently due to high operating temperatures, repeated transition periods, and so on. Rotors with large deformations often require straightening processes. The goal of this study is to develop a method to determine the optimal locations and strengths of hammer peening for straightening gas turbine rotors. A set of parametric hammer peening simulations were performed for various dimensions of straight rotors and peening locations. The deformed geometries of the rotor from the parametric simulations were presented as curvature vectors. These curvature vectors were fitted using an empirical function. For a given initial geometry of the rotor and hammer peening plans, the post-peening geometry of the rotor was predicted by superimposing the initial curvature and newly induced curvature. An optimization statement was defined to determine a set of hammer peening locations and strengths. Constraints were imposed to exclude areas where hammer peening could not be performed such as locations for bearings. The proposed method provides an optimal hammer peening plan for the given runout data. The proposed method was validated against a series of hammer peening test results for a simple shaft. The developed method can be applied to other types of rotor straightening methods such as hot spotting.
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Morgan, Laurence, i William Leithead. "Aerodynamic modelling of a novel vertical axis wind turbine concept". Journal of Physics: Conference Series 2257, nr 1 (1.04.2022): 012001. http://dx.doi.org/10.1088/1742-6596/2257/1/012001.
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Abstract This paper introduces the X-Rotor, a hybrid vertical-horizontal axis turbine concept designed to lower the cost of energy in the floating offshore environment. The development of a double multiple streamtube (DMS) simulation tool is presented alongside a thorough discussion of the secondary correction factors included in the model. New corrections for streamline curvature effects applicable to an airfoil where the blade normal plane is not aligned with the rotor plane are derived. The DMS model is successfully validated against experimental data and against higher fidelity lifting line (LLT) simulations. Strong agreement is observed between the LLT simulations and the DMS simulations for both rotor averaged and azimuthally varying outputs, indicating that the DMS simulations can be used for future control simulations.
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Hsieh, C.-F. "Non-undercutting region and property evaluation of epitrochoidal gerotor geometry". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, nr 2 (1.02.2010): 473–81. http://dx.doi.org/10.1243/09544062jmes1694.
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The gerotor pump is widely used for industrial applications. In this paper, the inner rotor profile is an equidistant epitrochoidal curve, and the outer rotor is generated by the inner rotor profile. This paper discusses an undercutting analysis of the rotor profile, in which the undercutting equations are derived by the theory of gearing. The non-undercutting region is determined by the undercutting curves of the inner and the outer rotors. Numerical examples show that the non-undercutting region on the gerotor profiles only needs to consider the lower part of the undercutting curve of the inner rotor. Besides, the curvature equations of the outer and inner rotors are derived for evaluating the rotor profile properties such as assessing the sealing property and the Hertz stress forecast. The theoretical stress and software simulations proved the stress forecast. The results obtained are important for using the gerotor profile in optimum design.
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Lei, Yao, Zhicheng Feng i Chensong Ma. "Aerodynamic Performance of V8 Octorotor MAV with Different Rotor Configurations in Hover". Machines 11, nr 4 (27.03.2023): 429. http://dx.doi.org/10.3390/machines11040429.
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A new multirotor aerial vehicle with two rotor arms formed in a V-shape configuration is introduced in this paper. To figure out the aerodynamic interference effects between rotors as an implication of the control method, this paper discusses the aerodynamic performance of the V8 Octorotor MAV with different rotor spacing using both experiments and simulations. A hovering experiment platform is applied to obtain the thrust, power consumption and rotational speed. PL (power loading) is promoted to characterize the aerodynamic performance of the V8 Octorotor MAV. The velocity vector, streamline and turbulent vortices’ distribution of the V8 Octorotor MAV are presented as the simulation results, which indicates that turbulence intensity generated by the MAV dissipates faster in a large rotor spacing. Therefore, rotor vibration is reduced with an increased hovering stability, and the power loading is much improved at G3 (1.2D–1.4D–1.6D–1.8D) with a better aerodynamic performance both with a thrust increment and power decrement.
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Bustamante Alarcon, Juan Manuel, José Leonel Sánchez Marmolejo, Luis Héctor Manjarrez Muñoz, Eduardo Steed Espinoza Quesada, Antonio Osorio Cordero i Luis Rodolfo García Carrillo. "Performance Evaluation of an H-VTOL Aircraft with Distributed Electric Propulsion and Ducted-Fans Using MIL Simulation". Machines 11, nr 9 (25.08.2023): 852. http://dx.doi.org/10.3390/machines11090852.
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This paper deals with the problem of increasing the energy efficiency of a hybrid vertical take-off and landing aircraft. To this end, an innovative aerial vehicle was developed, featuring a distributed electrical propulsion system with ducted-fan rotors. To compare and analyze the effectiveness of the proposed propulsion system, two configurations with a different number of ducted-fan rotors were examined: a four-rotor configuration and a six-rotor configuration. The mathematical model of the four-rotor configuration was derived using the Newton–Euler formalism, allowing the design and implementation of a control strategy for conducting model-in-the-loop simulations. These simulations enabled the evaluation and analysis of the performance of the proposed propulsion system, where the numerical results demonstrated the functionality of both designs and showed that, during the multirotor flight, the configuration with six rotors increased its energy efficiency by up to 11%, providing higher vertical lift with the same power consumption. This was achieved by distributing its weight among a higher number of engines. The incorporation of two additional ducted fans increased the weight and the drag of the six-rotor configuration, resulting in a low augmentation in power consumption of 1%. Finally, this caused a decrease in airspeed by up to 4% during the cruise speed phase.
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Ismaiel, Amr, i Shigeo Yoshida. "Aeroelastic Analysis of a Coplanar Twin-Rotor Wind Turbine". Energies 12, nr 10 (17.05.2019): 1881. http://dx.doi.org/10.3390/en12101881.
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Multi-rotor system (MRS) wind turbines can be a competitive alternative to large-scale wind turbines. In order to address the structural behavior of the turbine tower, an in-house aeroelastic tool has been developed to study the dynamic responses of a 2xNREL 5MW twin-rotor configuration wind turbine. The developed tool has been verified by comparing the results of a single-rotor configuration to a FAST analysis for the same simulation conditions. Steady flow and turbulent load cases were investigated for the twin-rotor configuration. Results of the simulations have shown that elasticity of the tower should be considered for studying tower dynamic responses. The tower loads, and deformations are not straightforward with the number of rotors added. For an equivalent tower, an additional rotor will increase the tower-top deflection, and the tower-base bending moment both in the fore-aft direction will be more than doubled. The tower torsional stiffness becomes a crucial factor in the case of a twin-rotor tower to avoid a severe torsional deflection. Tower natural frequencies are dominant over the flow conditions in regards to the loads and deflections.
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Kusano, Kazuya, Masato Furukawa, Kenichi Sakoda i Tomoya Fukui. "Aeroacoustic simulation of a cross-flow fan using lattice Boltzmann method with a RANS model". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, nr 6 (1.08.2021): 598–609. http://dx.doi.org/10.3397/in-2021-1578.
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The present study developed an unsteady RANS approach based on the lattice Boltzmann method (LBM), which can perform direct aeroacoustic simulations of low-speed fans at lower computational cost compared with the conventional LBM-LES approach. In this method, the k-ω turbulence model is incorporated into the LBM flow solver, where the transport equations of k and ω are also computed by the lattice Boltzmann method, similar to the Navier-Stokes equations. In addition, moving boundaries such as fan rotors are considered by a direct-forcing immersed boundary method. This numerical method was validated in a two-dimensional simulation of a cross-flow fan. As a result, the simulation was able to capture an eccentric vortex structure in the rotor, and the pressure rise by the work of the rotor can be reproduced. Also, the peak sound of the blade passing frequency can be successfully predicted by the present method. Furthermore, the simulation results showed that the peak sound is generated by the interaction between the rotor blade and the flow around the tongue part of the casing.
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Marchevsky, Ilia K., i Valeria V. Puzikova. "Numerical Simulation of Wind Turbine Rotors Autorotation by Using the Modified LS-STAG Immersed Boundary Method". International Journal of Rotating Machinery 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/6418108.
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A software package is developed for numerical simulation of wind turbine rotors autorotation by using the modified LS-STAG level-set/cut-cell immersed boundary method. The level-set function is used for immersed boundaries description. Algorithm of level-set function construction for complex-shaped airfoils, based on Bézier curves usage, is proposed. Also, algorithm for the level-set function recalculation at any time without reconstructing the Bézier curve for each new rotor position is described. The designed second-order Butterworth low-pass filter for aerodynamic torque filtration for simulations using coarse grids is presented. To verify the modified LS-STAG method, the flow past autorotating Savonius rotor with two blades was simulated at Re=1.96·105.
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Zhang, Lei, i Abraham Engeda. "Numerical simulation of rotating stall in a two-stage axial fan". Thermal Science 22, Suppl. 2 (2018): 655–63. http://dx.doi.org/10.2298/tsci171025050z.
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Computational fluid dynamics calculations using high-performance parallel computing were conducted to simulate the prestall flow of a two-stage axial fan. The simulations were run with a full-annulus grid that models the 3-D, viscous, unsteady blade row interaction without the need for an artificial inlet distortion to induce stall. The simulation shows the initiation and development of the stall inception in two rotors of the axial fan. The results show that the stall inception first occurs in the second stage. The spike-type stall inception occurred in the second stage, which is different from the common views. The starting positions of stall inception in both rotors are in the same circumferential direction, and the stall inceptions in both rotors turn into mature stall cells at the same time. Also, the rotation speed of the stall inception and rotating stall in the two rotors are the same. The rotating stall in the first and second stage rotor impellers are both directly induced by the blade tip leakage flow. However, the blocked flow in the second stage rotor strengthens the leakage flow in the blade tip of the first stage rotor indirectly, resulting in the formation of stall inception.
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Abdel Karim, Hazem Ali, Ahmed Reda El-Baz, Nabil Abdel Aziz Mahmoud i Ashraf Mostafa Hamed. "Numerical analysis on the performance of Dual Rotor wind turbine". International Journal of Scientific Research and Management 8, nr 03 (23.03.2020): 352–68. http://dx.doi.org/10.18535/ijsrm/v8i03.ec02.
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This study investigates the aerodynamic performance of wind turbines aiming to maximize the power extracted from the wind. The study is focusing on the effect of introducing a second rotor to the main rotor of the wind turbine in what is called a dual rotor wind turbine (DRWT). The numerical study took place on the performance of small-scale model of wind turbine of 0.9 m diameter using S826 airfoil.
Both the Co-rotating and Counter rotating configurations were investigated at different tip speed ratios (TSR) and compared with the performance of the single rotor wind turbine (SRWT). Many parameters were studied for dual rotor turbines. These include the spacing between the two rotors, the pitch angle of the rear rotor and the rotational speed of ratio rear to front rotor. Three-dimensional simulations performed and employed using CFD simulations with Multi Reference Frame (MRF) technique.
The Co Rotating Wind Turbine (CWT) and Counter Rotating Wind Turbine (CRWT) found to have better performance compared to that of the SRWT with an increase ranging from 12 to 14% in peak power coefficient. Moreover, the effect of changing the pitch angle of the rear rotor on the overall performance found to be of a negligible effect between angles 0⁰ until 2⁰ degrees tilting toward the front rotor. On the other hand, the ratio of rotational speed of the rear rotor to the front rotor found to cause a further increase in the peak performance of the CWT and CRWT ranging from 3 to 5%.
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Xia, Changfeng, Yuanwen Cai i Yuan Ren. "Steering law design for a magnetically suspended control and sensitive gyro cluster considering rotor tilt saturation". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, nr 11 (4.12.2018): 4066–76. http://dx.doi.org/10.1177/0954410018816593.
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To effectively reject the influence of rotor tilt saturation in a magnetically suspended control and sensitive gyro cluster, an adaptive nonlinear pseudo-inverse steering law is developed in this study. Based on the working principle of a Lorentz force magnetic bearing–rotor system in a single magnetically suspended control and sensitive gyro, the dynamical model of a rigid spacecraft equipped with a magnetically suspended control and sensitive gyro cluster is established. Because of the monotonicity and symmetric properties of the chosen nonlinear function, an adaptive nonlinear weighting matrix is incorporated with the pseudo-inverse steering law for the magnetically suspended control and sensitive gyro cluster. The steering law adjusts the weighting matrix elements according to saturation penalty functions so that the rotors generate control torques consistent with the limited rotor tilting domain. The effectiveness and superiority of this steering law are verified by numerical simulations. The simulation results demonstrate that the proposed steering law not only imposes control torques on the carrier spacecraft with three degrees of freedom but also avoids rotor tilt saturation, ensuring rapid attitude control of agile maneuvering spacecraft.
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PANG, Chao, Meng LI i Zhenghong GAO. "Study on the effect of transition process on rotor hovering simulation". Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 40, nr 2 (kwiecień 2022): 253–60. http://dx.doi.org/10.1051/jnwpu/20224020253.
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Hovering is one of important statuses to evaluate the aerodynamic performance of a rotor. With the development of the computer technology and CFD technique, the numerical methods based on the first principle are usually employed to evaluate the hovering performance of the rotor. The transition process will evidently affect the results from the RANS-based numerical simulations in some steady cases for the fixed wing aircrafts, which should be taken into consideration in the design process. But it's not clear whether the transition process would affect the numerical results for the rotor simulation. To provide the reference in designing and evaluating the rotorcraft, the effect of the transition process in the rotor simulation needs to be discussed further. The PSP rotor proposed by NASA is calculated using the in-house solver based on the overset grid in this paper. Simulations are performed with fully turbulent model as well as the transitional model and the results are compared to the experimental data. The results prove the superior ability to simulate the flow around a hovering rotor of the in-house solver. The relative errors of the numerical results are under 5%. The range of the laminar flow on the blade is proportional to the rotor thrust, which causes a higher Figure of Merit in transition simulation than the fully turbulent simulation. The sectional pressure distribution and torque distribution along the blade apparently suffer from the transition process, which doesn't affect the thrust distribution along the blade and the blade vortex wake flow under the rotor disk. An obvious flow separation on the surface of the blade can be observed in the transition simulation compared to the fully turbulent simulation.
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Stalewski, Wienczyslaw, i Wieslaw Zalewski. "Performance improvement of helicopter rotors through blade redesigning". Aircraft Engineering and Aerospace Technology 91, nr 5 (13.05.2019): 747–55. http://dx.doi.org/10.1108/aeat-01-2018-0009.
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Purpose The purpose of this paper is to determine dependencies between a rotor-blade shape and a rotor performance as well as to search for optimal shapes of blades dedicated for helicopter main and tail rotors. Design/methodology/approach The research is conducted based on computational methodology, using the parametric-design approach. The developed parametric model takes into account several typical blade-shape parameters. The rotor aerodynamic characteristics are evaluated using the unsteady Reynolds-averaged Navier–Stokes solver. Flow effects caused by rotating blades are modelled based on both simplified approach and truly 3D simulations. Findings The computational studies have shown that the helicopter-rotor performance may be significantly improved even through relatively simple aerodynamic redesigning of its blades. The research results confirm high potential of the developed methodology of rotor-blade optimisation. Developed families of helicopter-rotor-blade airfoils are competitive compared to the best airfoils cited in literature. The finally designed rotors, compared to the baselines, for the same driving power, are characterised by 5 and 32% higher thrust, in case of main and tail rotor, respectively. Practical implications The developed and implemented methodology of parametric design and optimisation of helicopter-rotor blades may be used in future studies on performance improvement of rotorcraft rotors. Some of presented results concern the redesigning of main and tail rotors of existing helicopters. These results may be used directly in modernisation processes of these helicopters. Originality/value The presented study is original in relation to the developed methodology of optimisation of helicopter-rotor blades, families of modern helicopter airfoils and innovative solutions in rotor-blade-design area.
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Van Zante, Dale E., Anthony J. Strazisar, Jerry R. Wood, Michael D. Hathaway i Theodore H. Okiishi. "Recommendations for Achieving Accurate Numerical Simulation of Tip Clearance Flows in Transonic Compressor Rotors". Journal of Turbomachinery 122, nr 4 (1.02.1999): 733–42. http://dx.doi.org/10.1115/1.1314609.
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The tip clearance flows of transonic compressor rotors are important because they have a significant impact on rotor and stage performance. A wall-bounded shear layer formed by the relative motion between the overtip leakage flow and the shroud wall is found to have a major influence on the development of the tip clearance flow field. This shear layer, which has not been recognized by earlier investigators, impacts the stable operating range of the rotor. Simulation accuracy is dependent on the ability of the numerical code to resolve this layer. While numerical simulations of these flows are quite sophisticated, they are seldom verified through rigorous comparisons of numerical and measured data because these kinds of measurements are rare in the detail necessary to be useful in high-speed machines. In this paper we compare measured tip-clearance flow details (e.g., trajectory and radial extent) with corresponding data obtained from a numerical simulation. Laser-Doppler Velocimeter (LDV) measurements acquired in a transonic compressor rotor, NASA Rotor 35, are used. The tip clearance flow field of this transonic rotor is simulated using a Navier–Stokes turbomachinery solver that incorporates an advanced k–ε turbulence model derived for flows that are not in local equilibrium. A simple method is presented for determining when the wall-bounded shear layer is an important component of the tip clearance flow field. [S0889-504X(00)02504-6]
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Kawaguchi, Natsuki, i Haruka Maruyama. "Design of an Optimal Allocator for Power Consumption Minimization in Hexarotor Drone Control Systems". Journal of Robotics and Mechatronics 36, nr 5 (20.10.2024): 1255–61. http://dx.doi.org/10.20965/jrm.2024.p1255.
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This paper presents an allocator design that considers the power consumption of rotors in the attitude and altitude control system of a hexarotor drone. Based on the power consumption model, the proposed method computes the thrust force that minimizes the total power consumption of the rotor while satisfying the control force constraints required by the controller. To obtain the rotor power consumption model, we conducted experiments on the rotor characteristics using the motors and electronic speed controllers used in the drones. Finally, numerical simulations were performed using the obtained power consumption models to compare the rotor power consumption of the proposed method with that of the conventional method, quantitatively evaluating the effectiveness of the proposed method.
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Zhong, Wei, Hongwei Tang, Tongguang Wang i Chengyong Zhu. "Accurate RANS Simulation of Wind Turbine Stall by Turbulence Coefficient Calibration". Applied Sciences 8, nr 9 (23.08.2018): 1444. http://dx.doi.org/10.3390/app8091444.
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Stall, a complex phenomenon related to flow separation, is difficult to be predicted accurately. The motivation of the present study is to propose an approach to improve the simulation accuracy of Reynolds Averaged Navier–Stokes equations (RANS) for wind turbines in stall. The approach is implemented in three steps in simulations of the S809 airfoil and the NREL (National Renewable Energy Laboratory) Phase VI rotor. The similarity between airfoil and rotor simulations is firstly investigated. It is found that the primary reason for the inaccuracy of rotor simulation is not the rotational effect or the 3-D effect, but the turbulence-related problem that already exists in airfoil simulation. Secondly, a coefficient of the SST turbulence model is calibrated in airfoil simulation, ensuring the onset and development of the light stall are predicted accurately. The lift of the airfoil in the light stall, which was overestimated about 30%, is reduced to a level consistent with experimental data. Thirdly, the calibrated coefficient is applied to rotor simulation. That makes the flow patterns on the blade properly simulated and the pressure distribution of the blade, as well as the torque of the rotor, are predicted more accurately. The relative error of the predicted maximum torque is reduced from 34.4% to 3.2%. Furthermore, the procedure of calibration is applied to the MEXICO (Model Experiments in Controlled Conditions) rotor, and the predicted pressure distributions over blade sections are better than the CFD (Computational Fluid Dynamics) results from the Mexnext project. In essence, the present study provides an approach for calibrating rotor simulation using airfoil experimental data, which enhances the potential of RANS in accurate simulation of the wind turbine aerodynamic performance.
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Ghaisas, Niranjan S., Aditya S. Ghate i Sanjiva K. Lele. "Effect of tip spacing, thrust coefficient and turbine spacing in multi-rotor wind turbines and farms". Wind Energy Science 5, nr 1 (6.01.2020): 51–72. http://dx.doi.org/10.5194/wes-5-51-2020.
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Abstract. Large eddy simulations (LESs) are performed to study the wakes of a multi-rotor wind turbine configuration comprising four identical rotors mounted on a single tower. The multi-rotor turbine wakes are compared to the wake of a conventional turbine comprising a single rotor per tower with the same frontal area, hub height and thrust coefficient. The multi-rotor turbine wakes are found to recover faster, while the turbulence intensity in the wake is smaller, compared to the wake of the conventional turbine. The differences with the wake of a conventional turbine increase as the spacing between the tips of the rotors in the multi-rotor configuration increases. The differences are also sensitive to the thrust coefficients used for all rotors, with more pronounced differences for larger thrust coefficients. The interaction between multiple multi-rotor turbines is contrasted with that between multiple single-rotor turbines by considering wind farms with five turbine units aligned perfectly with each other and with the wind direction. Similar to the isolated turbine results, multi-rotor wind farms show smaller wake losses and smaller turbulence intensity compared to wind farms comprised of conventional single-rotor turbines. The benefits of multi-rotor wind farms over single-rotor wind farms increase with increasing tip spacing, irrespective of the axial spacing and thrust coefficient. The mean velocity profiles and relative powers of turbines obtained from the LES results are predicted reasonably accurately by an analytical model assuming Gaussian radial profiles of the velocity deficits and a hybrid linear-quadratic model for the merging of wakes. These results show that a larger power density can be achieved without significantly increased fatigue loads by using multi-rotor turbines instead of conventional, single-rotor turbines.
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Shen, Guangyan, Zhonghui Xiao, Wen Zhang i Tiesheng Zheng. "Nonlinear Behavior Analysis of a Rotor Supported on Fluid-Film Bearings". Journal of Vibration and Acoustics 128, nr 1 (14.07.2005): 35–40. http://dx.doi.org/10.1115/1.2149394.
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A fast and accurate model to calculate the fluid-film forces of a fluid-film bearing with the Reynolds boundary condition is presented in the paper by using the free boundary theory and the variational method. The model is applied to the nonlinear dynamical behavior analysis of a rigid rotor in the elliptical bearing support. Both balanced and unbalanced rotors are taken into consideration. Numerical simulations show that the balanced rotor undergoes a supercritical Hopf bifurcation as the rotor spin speed increases. The investigation of the unbalanced rotor indicates that the motion can be a synchronous motion, subharmonic motion, quasi-period motion, or chaotic motion at different rotor spin speeds. These nonlinear phenomena are investigated in detail. Poincaré maps, bifurcation diagram and frequency spectra are utilized as diagnostic tools.
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Coppede, Daniel, Fabio da Silva Bortoli, Joao Manoel Losada Moreira, Nadja Simao Magalhaes i Carlos Frajuca. "Optimization of Flywheel Rotor Energy and Stability Using Finite Element Modelling". Energies 17, nr 12 (20.06.2024): 3042. http://dx.doi.org/10.3390/en17123042.
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An investigation on a flywheel is presented based on finite element modelling simulations for different geometries. The goal was to optimise the energy density (rotational energy-to-mass ratio) and, at the same time, the rotational energy of a flywheel rotor. The stress behaviour of flywheel rotors under the rotational speed at the maximum stress achievable by the flywheel was analysed. Under this condition, the energy density was obtained for the different geometries, as well as the rotational energy. The best energy density performance due to geometry was achieved with a flywheel rotor presenting a new Gaussian section, which is different from the known Laval disk shape. The best results using a single disk involved a rotational speed of nearly 279,000 rpm and a rotational energy density around 1584 kJ/kg (440 Wh/kg). These values still yielded low total energy; to increase its value, two or three rotors were added to the flywheel, which were analysed in regard to stability. In particular, the triple rotor energy density was ≈ 1550 kJ/kg (431 Wh/kg). As some instability was found in these rotors, a solution using reinforcement was developed to avoid such instabilities. The energy density of such a reinforced double rotor neared 1451 kJ/kg (403 Wh/kg), and the system achieved higher total energy. The material assumed for the devices was carbon fibre Hexcel UHM 12,000, a material kept constant throughout the simulations to allow comparison among the different geometries.
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Laube, Tomasz, i Janusz Piechna. "Analytical and Numerical Feasibility Analysis of a Contra-Rotary Ramjet Engine". Energies 13, nr 1 (30.12.2019): 163. http://dx.doi.org/10.3390/en13010163.
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A new idea for a contra-rotary ramjet engine is presented. To define the theoretical limits of the non-typical, contra-rotary ramjet engine configuration, its analytical model was developed. The results obtained from that model and the analytical results were compared with those received from numerical simulations. The main weakness of existing rotary ramjet engine projects is the very high rotational speed of the rotor required for achieving supersonic inlet flow. In this paper, a new idea for a contra-rotary ramjet engine (CORRE) is presented and analyzed. This paper presents the results of analytical analysis and numerical simulations of a jet engine system with two rotors rotating in opposite directions. Contra-rotating rotors generate a supersonic air velocity at the inlet to the compressor at two times slower rotor’s speed. To determine the flow characteristics, combustion process, and engine efficiency of the double-rotor engine, a numerical solution of the average Navier-Stokes equations was used with the k-eps turbulence model and the non-premixed combustion model. The results of numerical simulations of flow and the combustion process inside the contra-rotary jet engine achieving a shockwave compression are shown and compared with similar data for a single-rotor engine design and analytical data. This paper presents only the calculation results of the flow processes and the combustion process, indicating the advantages of the proposed double-rotor design. The results of the numerical analysis were presented on the contours and diagrams of the pressure and flow velocity, temperature distribution, and mass fraction of the fuel.
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Englberger, Antonia, Linus Wrba, Andreas Dörnbrack i Julie K. Lundquist. "How does the rotational direction of an upwind turbine affect its downwind neighbour?" Journal of Physics: Conference Series 2265, nr 2 (1.05.2022): 022048. http://dx.doi.org/10.1088/1742-6596/2265/2/022048.
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Abstract Wind-turbine blades rotate in clockwise direction looking downstream on the rotor. During daytime conditions of the atmospheric boundary layer, the rotational direction has no influence on the turbine wakes. In stably stratified conditions occurring during night, the atmospheric inflow is often characterized by a veering inflow describing a clockwise wind direction change with height in the Northern Hemisphere. A changing wind direction with height interacting with the rotor impacts its wake characteristics (wake elongation, width and deflection). We investigate the impact on the turbine performance (streamwise velocity for power, turbulence kinetic energy for loading) of a downwind turbine considering the four possible combinations of rotational directions of two 5 MW NREL rotors by means of large-eddy simulations. A counterclockwise rotating upwind turbine results in a 4.1% increase of the rotor averaged inflow velocity at the downwind rotor in comparison to a common clockwise rotating upwind turbine rotor. In case of two counterclockwise rotating rotors, the increase is 4.5%. This increase in streamwise velocity is accompanied by a 3.7% increase in rotor averaged turbulence kinetic energy. The performance difference of the downwind rotor (+4.8% increase of cumulative power of both wind turbines, if the upwind rotor rotates counterclockwise) results from the rotational direction dependent amplification or weakening of the spanwise and the vertical wind components, which is the result of the superposition of veering inflow and upwind rotor rotation.
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Grubišić, Vanda, Stefano Serafin, Lukas Strauss, Samuel J. Haimov, Jeffrey R. French i Larry D. Oolman. "Wave-Induced Boundary Layer Separation in the Lee of the Medicine Bow Mountains. Part II: Numerical Modeling". Journal of the Atmospheric Sciences 72, nr 12 (30.11.2015): 4865–84. http://dx.doi.org/10.1175/jas-d-14-0381.1.
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Abstract Mountain waves and rotors in the lee of the Medicine Bow Mountains in southeastern Wyoming are investigated in a two-part paper. Part I by French et al. delivers a detailed observational account of two rotor events: one displays characteristics of a hydraulic jump and the other displays characteristics of a classic lee-wave rotor. In Part II, presented here, results of high-resolution numerical simulations are conveyed and physical processes involved in the formation and dynamical evolution of these two rotor events are examined. The simulation results reveal that the origin of the observed rotors lies in boundary layer separation, induced by wave perturbations whose amplitudes reach maxima at or near the mountain top. An undular hydraulic jump that gave rise to a rotor in one of these events was found to be triggered by midtropospheric wave breaking and an ensuing strong downslope windstorm. Lee waves spawning rotors developed under conditions favoring wave energy trapping at low levels in different phases of these two events. The upstream shift of the boundary layer separation zone, documented to occur over a relatively short period of time in both events, is shown to be the manifestation of a transition in flow regimes, from downslope windstorms to trapped lee waves, in response to a rapid change in the upstream environment, related to the passage of a short-wave synoptic disturbance aloft. The model results also suggest that the secondary obstacles surrounding the Medicine Bow Mountains play a role in the dynamics of wave and rotor events by promoting lee-wave resonance in the complex terrain of southeastern Wyoming.
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Wang, Aiming, Yujie Bi, Yu Feng, Jie Yang, Xiaohan Cheng i Guoying Meng. "Continuous Rotor Dynamics of Multi-Disc and Multi-Span Rotors: A Theoretical and Numerical Investigation of the Identification of Rotor Unbalance from Unbalance Responses". Applied Sciences 12, nr 8 (11.04.2022): 3865. http://dx.doi.org/10.3390/app12083865.
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Rotor unbalance identification plays a critical role in balancing rotors. In this paper, concerned with multi-disc and multi-span rotor-bearing systems, two novel algorithms called the Single Direction Algorithm (SDA) and the Two Orthogonal Direction Algorithm (TODA) are proposed for identifying rotor unbalance from unbalance responses. A matrix method is proposed to solve the problem of the equations being non-linear transcendental, there being too many unknown variables in the equations, and rotor unbalances and bearing coefficients being coupled together. The unbalance responses at all the eccentric discs are necessary for identifying their unbalances. Numerical simulations are conducted to validate the proposed methods. Moreover, an adjustment point is found, and a proper sensor resolution is suggested to achieve high identification accuracy by means of numerical studies. In addition, the identification accuracy of SDA is better than TODA, and SDA is more practical and suitable for medium-speed and high-speed rotors. The proposed algorithms have the flexibility to incorporate any number of bearings and discs and provide a technique for monitoring rotor unbalance without test runs or external exciters.
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GOJON, Romain, Emma VELLA, Nicolas DOUE, Hélène PARISOT-DUPUIS, Bertrand MELLOT i Thierry JARDIN. "Aeroacoustic modeling of a low Reynolds number rotor in the wake of a cylindrical beam". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 270, nr 8 (4.10.2024): 3125–36. http://dx.doi.org/10.3397/in_2024_3278.
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In micro air vehicles, low Reynolds number rotors operating in close proximity to the fuselage raises the question of interaction noise as a prominent acoustic source. This paper proposes to comprehensively explore the interaction noise generation mechanisms, employing numerical simulations, experimental approaches, and analytical modelling. The focus is on scenarios where a low Reynolds number rotor is located in the wake of a cylindrical beam, and oppositely when the beam is in the wake of the rotor. In both scenarios, it is observed experimentally that the amplitudes of the BPF harmonics are increased with respect to that obtained without beam. This increase is higher when the rotor is in the wake of the beam compared to when the beam is in the wake of the rotor. The numerical simulation is shown to reproduce quite well the envelope of the amplitudes of the BPF harmonics obtained experimentally in both scenarios. Interestingly, by applying Ffowcs-Williams and Hawkings analogy on elementary surfaces, and not on the whole rotor-beam surface, the main sound generation mechanism was found to be the unsteady loading on the beam in both scenarios. Finally, an analytical modeling of the noise source mechanism is compared with experimental and numerical results.
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Rimša, Vytautas, i Mykolas Liugas. "Numerical Investigation of the Vortex Ring Phenomena in Rotorcraft". Aerospace 11, nr 6 (22.05.2024): 418. http://dx.doi.org/10.3390/aerospace11060418.
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Due to their complex aerodynamics, helicopters may enter different dangerous aerodynamic conditions under certain adverse circumstances. In this paper, we examine one such phenomenon—the Vortex Ring State (VRS). We present a simulation of the formation and evolution of a vortex ring around a helicopter’s main rotor. The calculations were carried out by solving Navier–Stokes equations using the Ansys CFX code. The simulations modeled a real helicopter using the rotor wing concept, assuming that only the main rotor blade’s geometry was modeled. A sensitivity study assessed the impact of the calculation domain and mesh size on main rotor thrust and required moment parameters. Simulations were conducted to determine the VRS region by observing the transition of the helicopter from a level flight, with the main rotor blades held at a fixed pitch position, to a gradual increase in vertical descent. The VRS region was compared with experimental results obtained from other authors, revealing sufficient coincidences. The main characteristics of the identified region were then described.
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Stanisławski, Jarosław. "Simulation of Boundary States of Helicopter Flight". Journal of KONES 26, nr 2 (1.06.2019): 137–44. http://dx.doi.org/10.2478/kones-2019-0042.
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Abstract Results of simulation of main rotor blade loads and deformations, which can be generated during boundary states of helicopter flight, are presented. Concerned cases of flight envelope include hover at maximum height, level flight at high velocity, pull-up manoeuvres applying cyclic pitch and mixed collective and cyclic control. The simulation calculations were executed for data of light helicopter with three-bladed articulated rotor. For analysis, the real blades are treated as elastic axes with distributed masses of blade segments. The model of deformable blade allows for out-of-plane bending, in plane bending, and torsion. For assumed flight state of helicopter, the equations of rotor blades motion are solved applying Runge-Kutta method. According to Galerkin method, for each concerned azimuthal position of blade the parameters of its motions are assumed as a combination of considered bending and torsion eigen modes of the blade. The loads of rotor blades generated during flight depend due to velocity of flight, helicopter mass, position of rotor axis in air and deflections of swashplate that correspond to collective and cyclic pitch angle applied to rotor blades. The results of simulations presenting rotor loads and blade deformations are shown in form of time-runs and as plots of rotor-disk distributions. The simulations of helicopter flight states may be useful for prediction the conditions of flight-tests without exceeding safety boundaries or may help to define limitations for manoeuvre and control of helicopter.
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Chen, Yue, Jiwen Cui i Xun Sun. "An Unbalance Optimization Method for a Multi-Stage Rotor Based on an Assembly Error Propagation Model". Applied Sciences 11, nr 2 (19.01.2021): 887. http://dx.doi.org/10.3390/app11020887.
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For the assembly of a multi-stage rotor, such as an aero-engine or gas turbine, the parts need to be assembled optimally to avoid excessive unbalance. We propose a method to optimize the unbalance of a multi-stage rotor during assembly. First, we developed an assembly error propagation model for a multi-stage rotor. The alignment process and distribution of the screw holes of the adjacent rotors was considered for the first time. Secondly, we propose a new assembly datum for unbalance optimization to ensure consistency with the actual conditions of a dynamic balance test. Finally, the unbalance optimization of a multi-stage rotor was achieved using a genetic algorithm, and the corresponding optimal assembly orientations of rotors at different stages were also identified. The results of the simulations showed that the assembly error propagation model had high accuracy and that the genetic optimization process had good convergence. The effect of unbalance optimization was also proven with experiments.
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Grinderslev, Christian, Niels Nørmark Sørensen, Sergio González Horcas, Niels Troldborg i Frederik Zahle. "Wind turbines in atmospheric flow: fluid–structure interaction simulations with hybrid turbulence modeling". Wind Energy Science 6, nr 3 (6.05.2021): 627–43. http://dx.doi.org/10.5194/wes-6-627-2021.
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Abstract. In order to design future large wind turbines, knowledge is needed about the impact of aero-elasticity on the rotor loads and performance and about the physics of the atmospheric flow surrounding the turbines. The objective of the present work is to study both effects by means of high-fidelity rotor-resolved numerical simulations. In particular, unsteady computational fluid dynamics (CFD) simulations of a 2.3 MW wind turbine are conducted, this rotor being the largest design with relevant experimental data available to the authors. Turbulence is modeled with two different approaches. On one hand, a model using the well-established technique of improved delayed detached eddy simulation (IDDES) is employed. An additional set of simulations relies on a novel hybrid turbulence model, developed within the framework of the present work. It consists of a blend of a large-eddy simulation (LES) model by Deardorff for atmospheric flow and an IDDES model for the separated flow near the rotor geometry. In the same way, the assessment of the influence of the blade flexibility is performed by comparing two different sets of computations. The first group accounts for a structural multi-body dynamics (MBD) model of the blades. The MBD solver was coupled to the CFD solver during run time with a staggered fluid–structure interaction (FSI) scheme. The second set of simulations uses the original rotor geometry, without accounting for any structural deflection. The results of the present work show no significant difference between the IDDES and the hybrid turbulence model. In a similar manner, and due to the fact that the considered rotor was relatively stiff, the loading variation introduced by the blade flexibility was found to be negligible when compared to the influence of inflow turbulence. The simulation method validated here is considered highly relevant for future turbine designs, where the impact of blade elasticity will be significant and the detailed structure of the atmospheric inflow will be important.
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Pätzold, Falk, André Bauknecht, Andreas Schlerf, Denis Sotomayor Zakharov, Lutz Bretschneider i Astrid Lampert. "Flight Experiments and Numerical Simulations for Investigating Multicopter Flow Field and Structure Deformation". Atmosphere 14, nr 9 (24.08.2023): 1336. http://dx.doi.org/10.3390/atmos14091336.
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The flow field induced by multirotor drones is of high interest for atmospheric research, as it locally influences the atmosphere and therefore may have an impact on the sensors installed for atmospheric measurements. Further, on-board vibrations can cause significant interference with the measurement equipment. To investigate the near flow field, an approach combining measurements of pressure and temperature distribution in-flight and in a laboratory setup together with numerical simulations was applied. Existing high-frequency measurement equipment was piggybacked during the initial flight tests with a newly developed 25 kg quadcopter system in a low-cost early-stage-error approach to obtain initial data and experience. During the flights, high resolution sensors for measuring pressure, temperature, acceleration, and deformation were applied with different setups at different locations below one of the rotor planes, respectively, at one rotor arm, to determine the multicopter’s influence on pressure and temperature measurements, to investigate rotor arm deformations, and to obtain data to compare with numerical simulations of this rotor setup. An external Schlieren-type measurement technique was tested to visualise the rotor vortices. The applied measurement techniques proved to be suitable for acquiring the state of the rotor-induced flow, but with some limitations. The comparison of measurements and simulations showed basic agreement and allowed for the identification of necessary adaptations for subsequent studies. The interaction of the rotor wakes with the rotor arms could be identified as the main source of the measured structural vibrations. The need for necessary improvements in the measurement setup, flight operation, and simulation setup is presented in detail.
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Lee, A.-C., i Y.-P. Shih. "Identification of the Unbalance Distribution and Dynamic Characteristics of Bearings in Flexible Rotors". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 210, nr 5 (wrzesień 1996): 409–32. http://dx.doi.org/10.1243/pime_proc_1996_210_216_02.
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This paper presents a new method for estimating dynamic characteristics of bearings and unbalance distribution in flexible rotors based on the transfer matrix method for analysing the steady state responses of rotor-bearing systems, in which rotary inertia, gyroscopic and transverse-shear effects are also considered. Identification can be realized from the measured response data influenced by bearing characteristics and rotor unbalance using the least-squares method. Justification of the method is presented by numerical simulations.
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Turner, M. G. "Multistage Turbine Simulations With Vortex–Blade Interaction". Journal of Turbomachinery 118, nr 4 (1.10.1996): 643–53. http://dx.doi.org/10.1115/1.2840920.
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The average passage approach of Adamczyk et al. (1990) has been used to simulate the multistage environment of the General Electric E3 low-pressure turbine. Four configurations have been analyzed and compared to test data. These include the nozzle only, the first stage, the first stage and a half, and the first two stages. A high casing slope on the first-stage nozzle causes the secondary flow vortex to separate off the casing and enter the downstream rotor. The detrimental effect on performance due to this vortex interaction has been predicted by the above approach, whereas isolated blade row calculations cannot simulate this interaction. The unsteady analysis developed by Chen et al. (1994) has also been run to understand the unsteady flow field in the first-stage rotor and compare with the average passage model and test data. Comparisons of both the steady and unsteady analyses with data are generally good, although in the region near the casing of the shrouded rotors, the predicted loss is lower than that shown by the data.
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(Henry) Jia, Zhongqi, Seongkyu Lee, Kalki Sharma i Kenneth S. Brentner. "Aeroacoustic Analysis of a Lift-Offset Coaxial Rotor Using High-Fidelity CFD/CSD Loose Coupling Simulation". Journal of the American Helicopter Society 65, nr 1 (1.01.2020): 1–15. http://dx.doi.org/10.4050/jahs.65.012011.
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This paper presents the aeroacoustic analysis of a lift-offset coaxial rotor in high-speed forward flight using the high-fidelity computational fluid dynamics/computational structural dynamics (CFD/CSD) loose coupling software Helios. Acoustic simulations are performed using the software PSU-WOPWOP at eight microphones positioned below the coaxial rotor. The total power of the three speed cases—100, 150, and 200 kt—is validated against flight-test data and shows good agreement. A series of parametric studies is also conducted to investigate the effect of lift offset, flight speed, and rotor-to-rotor separation distance on acoustics of the coaxial rotor. Strong blade-crossover and self-blade–vortex interaction events of the coaxial rotor, which are major sources of loading noise, are captured via high-fidelity CFD simulations in all speed cases. Highly impulsive acoustic pressure signals are identified in all simulation cases, and the magnitude of mid-frequency sound pressure level (SPL) increases significantly with increasing flight speed and lift offset. The strength of mid-frequency SPL, on the other hand, is reduced significantly as the rotor-to-rotor separation distance increases at 100 kt. However, the higher speed cases do not show a significant reduction in mid-frequency SPL with increasing separation distance.
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Sawicki, Jerzy T., Alberto Montilla-Bravo i Zdzislaw Gosiewski. "Thermomechanical Behavior of Rotor with Rubbing". International Journal of Rotating Machinery 9, nr 1 (2003): 41–47. http://dx.doi.org/10.1155/s1023621x03000058.
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This article presents an analytical study of the dynamics and stability of rotors subjected to rubbing due to contact with seals, taking account of associated thermal effects. The seal interaction force acting on the shaft gives rise to a friction force, which is a source of heating and can induce so-called spiral vibrations. A mathematical model that has been developed couples the heat-conduction equation with the equations for motion of the rotor. Numerical simulations have been conducted that show the thermomechanical behavior of the rotor at various operating conditions. A procedure for analyzing the stability of multibearing rotors based on the system eigenvalue analysis and the state-space approach has been proposed. Finally, the experimental data related to full annular rub have been presented.
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McVicar, J. S. G., i R. Bradley. "Efficient and robust algorithms for trim and stability analysis of advanced rotorcraft simulations". Aeronautical Journal 101, nr 1008 (październik 1997): 375–87. http://dx.doi.org/10.1017/s0001924000066082.
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AbstractThis paper derives innovative techniques for use in the trimming and stability analysis of advanced rotorcraft simulations. It begins by exploiting the symmetry of the rotor to produce an efficient definition of periodic trim which is applicable to rotorcraft simulations. This definition is then expanded to produce a trimming algorithm which is capable of concurrently ascertaining the initial conditions and control inputs necessary to trim latest generation simulation models to a specified periodic trim state. The algorithm is based on a periodic shooting approach with Newton-Raphson iteration and exploits the symmetry of the rotor to minimise computational workload. The definition of periodic trim is then further developed to produce a technique by which the stability characteristics of rotorcraft can be ascertained from advanced simulation models. This technique is based on a Floquet approach and again exploits the symmetry of the rotor to reduce computational burden. The paper concludes by presenting results obtained when the stability characteristics of a tiltrotor simulation model are investigated.
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Suder, Kenneth L., Michael D. Hathaway, Scott A. Thorp, Anthony J. Strazisar i Michelle B. Bright. "Compressor Stability Enhancement Using Discrete Tip Injection". Journal of Turbomachinery 123, nr 1 (1.02.2000): 14–23. http://dx.doi.org/10.1115/1.1330272.
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Mass injection upstream of the tip of a high-speed axial compressor rotor is a stability enhancement approach known to be effective in suppressing stall in tip-critical rotors. This process is examined in a transonic axial compressor rotor through experiments and time-averaged Navier-Stokes CFD simulations. Measurements and simulations for discrete injection are presented for a range of injection rates and distributions of injectors around the annulus. The simulations indicate that tip injection increases stability by unloading the rotor tip and that increasing injection velocity improves the effectiveness of tip injection. For the tested rotor, experimental results demonstrate that at 70 percent speed the stalling flow coefficient can be reduced by 30 percent using an injected massflow equivalent to 1 percent of the annulus flow. At design speed, the stalling flow coefficient was reduced by 6 percent using an injected massflow equivalent to 2 percent of the annulus flow. The experiments show that stability enhancement is related to the mass-averaged axial velocity at the tip. For a given injected massflow, the mass-averaged axial velocity at the tip is increased by injecting flow over discrete portions of the circumference as opposed to full-annular injection. The implications of these results on the design of recirculating casing treatments and other methods to enhance stability will be discussed.