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1
Tan, J., X. Wang, D. Qi i R. Wang. "The effects of radial inlet with splitters on the performance of variable inlet guide vanes in a centrifugal compressor stage". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, nr 9 (28.06.2011): 2089–105. http://dx.doi.org/10.1177/0954406211407799.
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Variable inlet guide vanes (VIGVs) can regulate pressure ratio and mass flow at constant rotational speed in centrifugal compressors as a result of inducing a controlled prewhirl in front of impellers. Radial inlets and VIGVs are typical upstream components in front of the first-stage impellers in many industrial centrifugal compressors. However, previous investigations on VIGVs in centrifugal compressors were mostly conducted under the condition of axial inlets, and this study aims to focus on the effects of radial inlet on the VIGVs performance of a centrifugal compressor stage. The axial inlet stage model is compared with the radial inlet stage model with splitters using numerical flow simulation. The flow from the radial inlet was non-uniform in both circumferential and radial directions; thus, the VIGVs, the impeller, the vaneless diffuser, and the return vane channel are modelled with fully 360° passages. The three-dimensional (3D) flow field is numerically simulated at VIGVs setting angles ranging from - 20° to 60°. The overall stage performance parameters are obtained by integrating the field quantities. Though the splitters are equipped in the radial inlet, the overall stage polytropic efficiency decreases by an average of 4 per cent and total pressure ratio decreases by an average of 3.3per cent in comparison with the axial stage model. This can be attributed to the effect of both flow non-uniformity induced by radial inlet and flow loss in the radial inlet at different VIGV setting angles. The flow loss in the radial inlet with splitters is the main reason of the stage performance decrease compared with the flow non-uniformity. The simulation results show that the performance of VIGVs is degraded by its inlet flow distortions resulting from a radial inlet. The results in this study can be applied to centrifugal compressor design and optimization.
2
Bozza, F., A. Senatore i R. Tuccillo. "Thermal Cycle Analysis and Component Aerodesign for Gas Turbine Concept in Low-Range Cogenerating Systems". Journal of Engineering for Gas Turbines and Power 118, nr 4 (1.10.1996): 792–802. http://dx.doi.org/10.1115/1.2816995.
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The authors link together their previous experiences in gas turbine plant analysis and aerodynamic design of radial flow compressors. In recent papers they have introduced a method for the performance estimation of gas turbine engines, based on the prediction of the matching conditions among the several components in the whole operating range. On the other hand they have expressly paid attention to the problem of optimal design of radial flow compressors for satisfactory operation within an assigned operating range. In this paper, the authors present an integrated method, which aims to define the optimal characteristics of a low-power gas turbine engine (i.e., in the range 500–2000 kW). In this case, the radial compressor performance plays an important role as regards gas turbine operation for both power generation and cogeneration applications. The analysis proceeds with the optimization of rotating components (i.e., radial compressor and axial flow turbine) for given thermal cycle parameters. The prescribed objectives of the optimizing procedure are related to performance levels not only at the reference design conditions but also throughout the operating field. A particular emphasis is given to the extension of the field of satisfactory performance for cogeneration applications, with best fitting of mechanical and thermal power requirements. The aerodynamic design of radial flow compressor utilizes a method based on genetic algorithms.
3
Berezin, A. V., A. F. Kuftov i I. B. Shkurikhin. "Blading impellers of radial-flow compressors". Journal of Machinery Manufacture and Reliability 44, nr 7 (grudzień 2015): 616–25. http://dx.doi.org/10.3103/s1052618815070055.
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Prata, A. T., J. R. S. Fernandes i F. Fagotti. "PISTON LUBRICATION IN RECIPROCATING COMPRESSORS". Revista de Engenharia Térmica 1, nr 1 (30.06.2001): 56. http://dx.doi.org/10.5380/reterm.v1i1.3501.
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Piston dynamics plays a fundamental role in two critical processes related to fluid flow in reciprocating compressors. The first is the refrigerant leakage through the radial clearance, which may cause considerable loss in the pumping efficiency of the compressor. The second process is the viscous friction associated with the lubricant film in the radial clearance; certainly a significant factor in the compressor energy consumption. In the present contribution a numerical simulation of the piston movement inside the cylinder of a reciprocating compressor is performed. The compressor considered here is a small hermetic compressor employed in domestic refrigerators. For the problem formulation both the axial and the radial piston motion is considered. In operation, the piston moves up and down along the axis of the cylinder, but the radial oscillatory motion in the cylinder bore, despite being usually small, plays a very important role on the compressor performance and reliability. The compromise between sealing of the gas leakage through the piston-cylinder clearance and the friction losses requires a detailed analysis of the oscillatory motion for a good design. The forces acting on the piston are the hydrodynamic force due to the pressure build up in the oil film (lubrication effects), the force due to the connecting rod, the viscous force associated with the relative motion between the piston and oil, and the force exerted by the gas on the top of the piston. All corresponding moments are also included in the problem formulation of the piston dynamics, in order to determine the piston trajectory, velocity and acceleration at each time step. The hydrodynamic force is obtained from the integration of the pressure distribution on the piston skirt, which, in turn, is determined from a finite volume solution of the time dependent equation that governs the oil flow. A Newton-Raphson procedure was employed in solving the equations of the piston dynamics. The results explored the effects of some design parameters and operating conditions on the stability of the piston, its sealing performance and friction losses. Emphasis was placed on investigating the influence of the pin location, radial clearance and oil viscosity on the piston dynamics. The complexity of the piston movement in reciprocating compressors was demonstrated and the detailed model presented can be employed as an useful tool for engineering design.
5
Eriksson, Lars-Erik. "Simulation of transonic flow in radial compressors". Computer Methods in Applied Mechanics and Engineering 64, nr 1-3 (październik 1987): 95–111. http://dx.doi.org/10.1016/0045-7825(87)90035-1.
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Song, J. W., M. Raheel i A. Engeda. "A compressible flow theory for regenerative compressors with aerofoil blades". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 217, nr 11 (1.11.2003): 1241–57. http://dx.doi.org/10.1243/095440603771665269.
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Regenerative flow compressors (RFCs) are rotodynamic machines capable of producing high heads at very low flowrates. They have very low specific speed and share some of the characteristics of positive displacement machines such as a roots blower, but without the problems of lubrication and wear. They can produce heads equivalent to that of several centrifugal stages from a single rotor with comparable tip speed. The compression process is usually not regarded as efficient. Typically they produce efficiency of less than 50 per cent but still they have found many applications because they allow the use of fluid dynamic compressors in place of positive displacement compressors for duties requiring high heads at low flowrates. There are very few mathematical models in the literature that explain the behaviour of regenerative turbomachines and predict the performance. Most of these models assumed incompressible flow, thus limiting their use to only pumps and blowers. Moreover, they needed extensive experimental support for performance prediction. Hence, it is very interesting from an industrial point of view to find efficient theoretical means that are able to forecast regenerative compressor performances, using easy to find geometric and fluid dynamic parameters. A compressible flow theory is thus presented for the first time in this paper to describe complex three-dimensional corkscrew flow patterns in regenerative compressors. Conventional RFC were designed with radial, non-radial or semicircular impeller blades. In the present investigation, the authors have discussed RFCs with aerofoil blades and an annular flow channel containing a core to direct circulating flow to the blades with a minimum amount of losses. The effects of various geometric elements on the performance of RFCs are studied. All the major sources of losses in blade and channel region are identified. Governing equations for the flow in the compressor are derived and a performance prediction code based on governing equations and loss models is developed. Theoretical performance results are compared with published test data on aerofoil blade RFCs. Based on sensitivity analysis from the code, design changes are suggested for performance improvement.
7
Dutton, J. C., P. Piemsomboon i P. E. Jenkins. "Flowfield and Performance Measurements in a Vaned Radial Diffuser". Journal of Fluids Engineering 108, nr 2 (1.06.1986): 141–47. http://dx.doi.org/10.1115/1.3242553.
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The flow characteristics of a vaned diffuser typical of those currently used in centrifugal compressors have been determined experimentally by using a static diffuser test rig. The vortex test vehicle (VTV) portion of this rig was used to simulate the essential features of the flow leaving the impeller of an actual compressor. The mean flow phenomena at the diffuser entrance and the static pressure recovery along the diffuser passage have been determined. In addition, the flow angle and Mach number distributions at several key locations throughout the diffuser channel have been obtained. The most notable feature of the diffuser flowfield is the high degree of nonuniformity in the inlet/leading edge region.
8
Prata, A. T., J. R. S. Fernandes i F. Fagotti. "Dynamic Analysis of Piston Secondary Motion for Small Reciprocating Compressors". Journal of Tribology 122, nr 4 (4.04.2000): 752–60. http://dx.doi.org/10.1115/1.1314603.
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Piston dynamics plays a fundamental role in two critical processes related to fluid flow in reciprocating compressors. The first is the gas leakage through the radial clearance, which may cause considerable loss in the pumping efficiency of the compressor. The second process is the viscous friction associated with the lubricant film in the radial clearance. In the present contribution a numerical simulation is performed for a ringless piston inside the cylinder of a reciprocating compressor, including both the axial and the radial piston motion. The compressor considered here is a small hermetic compressor employed in domestic refrigerators, with the radial clearance between piston and cylinder filled with lubricant oil. In operation, the piston moves up and down along the axis of the cylinder, but the radial oscillatory motion in the cylinder bore, despite being usually small, plays a very important role on the compressor performance and reliability. The compromise between oil leakage through the piston-cylinder clearance and the friction losses requires a detailed analysis of the oscillatory motion for a good design. All corresponding forces and moments are included in the problem formulation of the piston dynamics in order to determine the piston trajectory, velocity and acceleration at each time step. The hydrodynamic force is obtained from the integration of the pressure distribution on the piston skirt, which, in turn, is determined from a finite volume solution of the time dependent equation that governs the oil flow. A Newton-Raphson procedure was employed in solving the equations of the piston dynamics. The results explored the effects of some design parameters and operating conditions on the stability of the piston, the oil leakage, and friction losses. Emphasis was placed on investigating the influence of the pin location, radial clearance and oil viscosity on the piston dynamics. [S0742-4787(11)00301-8]
9
Rodgers, C. "Impingement Starting and Power Boosting of Small Gas Turbines". Journal of Engineering for Gas Turbines and Power 107, nr 4 (1.10.1985): 821–27. http://dx.doi.org/10.1115/1.3239817.
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The technology of high-pressure air or hot-gas impingement from stationary shroud supplementary nozzles onto radial outflow compressors and radial inflow turbines to permit rapid gas turbine starting or power boosting is discussed. Data are presented on the equivalent turbine component performance for convergent/divergent shroud impingement nozzles, which reveal the sensitivity of nozzle velocity coefficient with Mach number and turbine efficiency with impingement nozzle admission arc. Compressor and turbine matching is addressed in the transient turbine start mode with the possibility of operating these components in braking or reverse flow regimes when impingement flow rates exceed design.
10
Han, Fenghui, Zhe Wang, Yijun Mao, Jiajian Tan i Wenhua Li. "Flow Control of Radial Inlet Chamber and Downstream Effects on a Centrifugal Compressor Stage". Applied Sciences 11, nr 5 (1.03.2021): 2168. http://dx.doi.org/10.3390/app11052168.
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Radial inlet chambers are widely used in various multistage centrifugal compressors, although they induce extra flow loss and inlet distortions. In this paper, the detailed flow characteristics inside the radial inlet chamber of an industrial centrifugal compressor have been numerically investigated for flow control and performance improvement. First, the numerical results are validated against the experimental data, and flow conditions inside the inlet chambers with different structures are compared. They indicate that, in the non-guide vane scheme, sudden expansions, tangential flows and flow separations in the spiral and annular convergent channels are the major causes of flow loss and distortions, while using guide vanes could introduce additional flow impacts, separations and wakes. Based on the flow analysis, structure improvements have been carried out on the radial inlet chamber, and an average increase of 4.97% has been achieved in the inlet chamber efficiencies over different operating conditions. However, the results further reveal that the increases in the performance and overall flow uniformity just in the radial inlet chamber do not necessarily mean a performance improvement in the downstream components, and the distribution of the positive tangential velocity at the impeller inlet might be a more essential factor for the efficiency of the whole compressor.
11
Sundström, Elias, Bernhard Semlitsch i Mihai Mihăescu. "Acoustic signature of flow instabilities in radial compressors". Journal of Sound and Vibration 434 (listopad 2018): 221–36. http://dx.doi.org/10.1016/j.jsv.2018.07.040.
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Sato, T., J. M. Oh i A. Engeda. "Experimental and Numerical Investigation of the Flow in a Vaneless Diffuser of a Centrifugal Compressor Stage. Part 1: Experimental Investigation". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 219, nr 10 (1.10.2005): 1053–59. http://dx.doi.org/10.1243/095440605x31904.
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The flow in a radial vaneless diffuser downstream of a centrifugal compressor is highly complex, as the flow is turbulent, unsteady, viscous, and three-dimensional. Depending on the initial state of the end-wall boundary layers and the diffuser length, the flow may become fully developed or may separate from one of the walls. Therefore, to improve the diffuser performance, it is important to understand the flow field in the diffuser in detail. As the diffuser width is generally very small for most radial stages and an adverse pressure gradient exists, secondary flows are generated, making the flow fields more complicated. In addition, skewed boundary layers form on the wall surfaces. As flowrate is reduced, the flow field becomes more complicated and leads to rotating stall. This article presents detailed flow measurements in a vaneless diffuser of a centrifugal compressor stage with a very high flow coefficient radial impeller. Usually, centrifugal compressors with radial impellers are designed in the flow coefficient (ϕ) range ϕ = 0.01 - 0.16. Often, the need arises to design higher flow coefficient, ϕ, radial stages. Detailed measurements were carried out in the vaneless diffuser at seven radial positions downstream of a radial impeller designed for a very high flow coefficient of ϕ = 0.2. The experimental investigation was carried at four rotational speeds 13 000, 15 500, 18 000, and 20 500 r/min, but only the result of 20 500 r/min at near-design-point flowrate (5.11 kg/s) is reported in this article.
13
Han, Fenghui, Zhe Wang, Yijun Mao, Jiajian Tan i Wenhua Li. "Experimental and numerical studies on the influence of inlet guide vanes of centrifugal compressor on the flow field characteristics of inlet chamber". Advances in Mechanical Engineering 12, nr 11 (listopad 2020): 168781402097490. http://dx.doi.org/10.1177/1687814020974909.
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Inlet chambers (IC) are the typical upstream component of centrifugal compressors, and inlet guide vanes in the IC have a great impact on its internal flow and aerodynamic loss, which will significantly influence the performance of the downstream compressor stages. In this paper, an experimental study was carried out on the flow characteristics inside a radial IC of an industrial centrifugal compressor, including five testing sections and 968 measuring points for two schemes with and without guide vanes. Detailed distributions of flow parameters on each section were obtained as well as the overall performance of the radial IC, and the causes of the flow loss inside the IC and the non-uniformity of flow parameters at the outlet section were investigated. Besides, numerical simulations were performed to further analyze the flow characteristics inside the radial IC. The experimental and numerical results indicate that, in the scheme without guide vanes, sudden expansions in the spiral channel and flow separations in the annular convergence channel are the major sources of flow loss and distortions generated in the radial IC; while in the scheme with guide vanes, the flow impacts, separations and wakes caused by the inappropriate design of guide vanes are the main reasons for the flow loss of the IC itself and the uneven flow distributions at the IC outlet.
14
Gallimore, S. J., i N. A. Cumpsty. "Spanwise Mixing in Multistage Axial Flow Compressors: Part I—Experimental Investigation". Journal of Turbomachinery 108, nr 1 (1.07.1986): 2–9. http://dx.doi.org/10.1115/1.3262019.
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Spanwise mixing has been shown to be an essential feature of multistage compressor aerodynamics. The cause of spanwise mixing in multistage axial flow compressors has been investigated directly by using an ethylene tracer gas technique in two low-speed, four-stage machines. The results show that the dominant mechanism is that of turbulent type diffusion and not the radial convection of flow properties as has been previously suggested. The mixing was also found to be substantially uniform in magnitude all the way across the span with levels similar to those found in two-dimensional turbulent wakes.
15
Ehrich, F. "Rotor Whirl Forces Induced by the Tip Clearance Effect in Axial Flow Compressors". Journal of Vibration and Acoustics 115, nr 4 (1.10.1993): 509–15. http://dx.doi.org/10.1115/1.2930379.
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It is now widely recognized that destabilizing forces, tending to generate forward rotor whirl, are generated in axial flow turbines as a result of the nonuniform torque induced by the nonuniform tip-clearance in a deflected rotor—the so called Thomas/Alford force (Thomas, 1958, and Alford, 1965). It is also recognized that there will be a similar effect in axial flow compressors, but qualitative considerations cannot definitively establish the magnitude or even the direction of the induced whirling forces—that is, if they will tend to forward or backward whirl. Applying a “parallel compressor” model to simulate the operation of a compressor rotor deflected radially in its clearance, it is possible to derive a quantitative estimate of the proportionality factor β which relates the Thomas/Alford force in axial flow compressors (i.e., the tangential force generated by a radial deflection of the rotor) to the torque level in the compressor. The analysis makes use of experimental data from the GE Aircraft Engines Low Speed Research Compressor facility comparing the performance of three different axial flow compressors, each with four stages (typical of a mid-block of an aircraft gas turbine compressor) at two different clearances (expressed as a percent of blade length)—CL/L = 1.4 percent and CL/L = 2.8 percent. It is found that the value of β is in the range of +0.27 to −0.71 in the vicinity of the stages’ nominal operating line and +0.08 to −1.25 in the vicinity of the stages’ operation at peak efficiency. The value of β reaches a level of between −1.16 and −3.36 as the compressor is operated near its stalled condition. The final result bears a very strong resemblance to the correlation obtained by improvising a normalization of the experimental data of Vance and Laudadio (1984) and a generic relationship to the analytic results of Colding-Jorgensen (1990).
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Moukalled, F., N. Naim i I. Lakkis. "Computer-Aided Analysis of Centrifugal Compressors". International Journal of Mechanical Engineering Education 22, nr 4 (październik 1994): 245–58. http://dx.doi.org/10.1177/030641909402200402.
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This paper describes computer-aided analysis of centrifugal compressors (CAACC), a micro-computer-based, interactive, and menu-driven software package for use as an educational tool by mechanical engineering students studying radial flow compressors. CAACC is written in the Pascal computer language and runs on IBM PC, or compatible, computers. In addition to solving for any unknown variables, the graphical utilities of the package allow the user to display a diagrammatic sketch of the compressor and to draw velocity diagrams at several locations. Furthermore, the program allows the investigation and plotting of the variation of any parameter versus any other parameter. Through this option, the package guides the student in learning the basics of centrifugal compressors by the various performance studies that can be undertaken and graphically displayed. The comprehensive example presented demonstrates the capabilities of the package as a teaching tool.
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Leylek, J. H., i D. C. Wisler. "Mixing in Axial-Flow Compressors: Conclusions Drawn From Three-Dimensional Navier–Stokes Analyses and Experiments". Journal of Turbomachinery 113, nr 2 (1.04.1991): 139–56. http://dx.doi.org/10.1115/1.2929069.
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Extensive numerical analyses and experiments have been conducted to understand mixing phenomena in multistage, axial-flow compressors. For the first time in the literature the following are documented: Detailed three-dimensional Navier–Stokes solutions, with high order turbulence modeling, are presented for flow through a compressor vane row at both design and off-design (increased) loading; comparison of these computations with detailed experimental data show excellent agreement at both loading levels; the results are then used to explain important aspects of mixing in compressors. The three-dimensional analyses show the development of spanwise (radial) and circumferential flows in the stator and the change in location and extent of separated flow regions as loading increases. The numerical solutions support previous interpretations of experimental data obtained on the same blading using the ethylene tracer-gas technique and hot-wire anemometry. These results, plus new tracer-gas data, show that both secondary flow and turbulent diffusion are mechanisms responsible for both spanwise and circumferential mixing in axial-flow compressors. The relative importance of the two mechanisms depends upon the configuration and loading levels. It appears that using the correct spanwise distributions of time-averaged inlet boundary conditions for three-dimensional Navier–Stokes computations enables one to explain much of the flow physics for this stator.
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Ziegler, Kai U., Heinz E. Gallus i Reinhard Niehuis. "A Study on Impeller-Diffuser Interaction—Part I: Influence on the Performance". Journal of Turbomachinery 125, nr 1 (1.01.2003): 173–82. http://dx.doi.org/10.1115/1.1516814.
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The interaction between impeller and diffuser is considered to have strong influence on the flow in centrifugal compressors. However, the knowledge about this influence is still not satisfying. This two-part paper presents an experimental investigation of the effect of impeller-diffuser interaction on the unsteady and the time averaged flow field configuration in impeller and diffuser and the performance of these components. The flat wedge vaned diffuser of the investigated compressor allows an independent adjustment of diffuser vane angle and radial gap between impeller exit and diffuser vane inlet. Attention is mainly directed to the radial gap, as it determines the intensity of the impeller-diffuser interaction. Part I deals with the integral flow losses and the diffusion in impeller, diffuser and the entire compressor. An extensive test series with steady probe measurements at impeller exit and diffuser exit was performed at 10 different diffuser geometries and different operating points. The results show that in most cases smaller radial gaps are leading to a more homogeneous flow field at diffuser vane exit and to a higher diffuser pressure recovery resulting in a higher compressor efficiency. On the other hand, impeller efficiency is hardly affected by the radial gap. In Part II, measurements with a laser-2-focus velocimeter are presented illuminating the reasons for the effects found. The experimental results are published as an open CFD test case under the name “Radiver.”
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Zhao, Wenfeng, Qun Zheng, Bin Jiang i Aqiang Lin. "A Passive Control Method of Hub Corner Stall in a 1.5-Stage Axial Compressor under Low-Speed Conditions". Energies 13, nr 11 (27.05.2020): 2691. http://dx.doi.org/10.3390/en13112691.
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Since the use of the compressor of a ship gas turbine is unavoidable at a low-speed operation, the flow field characteristics and stall mechanism at off-design speeds are important aspects for compressor designers. In this study, the first 1.5 stages of an eight-stage compressor are numerically simulated. The mechanism of compressor rotor instability at lower speeds is identified. The characteristic lines of compressors with various partial clearance are calculated at low speed (0.6 N). The flow field of the same outlet pressure (near stall point of the original compressor without clearance) is compared and analyzed. The results show that, at the near stall point, the suction surface separation and backflow occur in the main flow of the rotor top. It develops along the blade span and finally blocks the flow passage of the rotor, which results in the compressor stall. At the same time, the stall also occurs at the corner of the stator hub. In this paper, the characteristics of partial clearance in four different positions of the stator hub are analyzed. The near stall point and the working point are selected for the flow field analysis. It is concluded that the radial development of the stall vortex on the suction surface of the stator can be restrained by the partial clearance at the stator. In this paper, a passive control method by partial clearance is used in the real compressors, which is different from previous studies on cascades. The margin increases at low speeds.
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Motriuk, R. W., i D. P. Harvey. "Centrifugal Compressor Modifications and Their Effect on High-Frequency Pipe Wall Vibration". Journal of Pressure Vessel Technology 120, nr 3 (1.08.1998): 276–82. http://dx.doi.org/10.1115/1.2842058.
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High-frequency pulsation generated by centrifugal compressors, with pressure wavelengths much smaller than the attached pipe diameter, can cause fatigue failures of the compressor internals, impair compressor performance, and damage the attached compressor piping. There are numerous sources producing pulsation in centrifugal compressors. Some of them are discussed in literature at large (Japikse, 1995; Niese, 1976). NGTL has experienced extreme high-frequency discharge pulsation and pipe wall vibration on many of its radial inlet high-flow centrifugal gas compressor facilities. These pulsations led to several piping attachment failures and compressor internal component failures while the compressor operated within the design envelope. This paper considers severe pulsation conditions at an NGTL compression facility which resulted in unacceptable piping vibration. Significant vibration attenuation was achieved by modifying the compressor (pulsation source) through removal of the diffuser vanes and partial removal of the inlet guide vanes (IGV). Direct comparison of the changes in vibration, pulsation, and performance are made for each of the modifications. The vibration problem, probable causes, options available to address the problem, and the results of implementation are reviewed. The effects of diffuser vane removal on discharge pipe wall vibration as well as changes in compressor performance are described.
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Li, Xiaoran, Weifeng Wu, Jing Zhang, Chengqiang Guo, Feng Ke i Fuqiang Jiang. "Analysis of 3D Transient Flow in a High-Speed Scroll Refrigeration Compressor". Energies 16, nr 7 (28.03.2023): 3089. http://dx.doi.org/10.3390/en16073089.
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In mobile devices such as aircraft and electric vehicles, due to limited space, there are strict requirements on the volume and weight of the compressor mounted on the vehicle. Therefore, high-speed scroll compressors have attracted more and more attention because of their small size and light weight. In this paper, the numerical calculations and analysis of the three-dimensional (3D) transient flows in a high-speed scroll refrigeration compressor were established and validated. Circumferential gas intake was used in the simulation. According to the actual compressor size, the mesh generation accurately considers clearances. The radial and the axial clearances were both set as 0.01 mm. A dynamic and high-quality hexahedral structured mesh was generated for the working chamber, and the problem of insufficient grid density in radial clearance was solved. When the rotational speed was set as 3000 rpm, 6000 rpm, and 9000 rpm alternatively, the difference in the volume efficiency of the simulation and the experiment results was below 6.3%. The results show that the higher rotational speed contributed to the greater pressure fluctuation in the compression chamber and the discharge process, and the over-compression phenomenon was more obvious. The maximum leakage velocity was 160 m/s, and the tangential leakage velocity was higher than the radial leakage velocity. Meanwhile, radial leakage velocity will increase significantly in high-speed operation mode. With the increasing rotational speed, the position of the maximum axial and tangential leakage velocity was closer to the start of the scroll. Therefore, the seal of the scroll starting part is very important in the design of a high-speed scroll compressor.
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Carsten, Degendorfer, Reza S. Abhari, Klemens Vogel i René Hunziker. "Experimental and numerical investigation of blade resonance in a centrifugal compressor for varying gas properties". Journal of the Global Power and Propulsion Society 2 (20.09.2018): Q15CRP. http://dx.doi.org/10.22261/jgpps.q15crp.
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The blades of centrifugal compressors are exposed to unsteady forces during operation which can result in resonance response conditions and failures due to high cycle fatigue. A typical source of excitation is the unsteady fluid structure interaction between the impeller blades and the downstream vaned diffuser. Centrifugal compressors are operated with various working fluids with a wide range of applications in the power and process industry. Understanding the excitation mechanisms for different working fluids will help to design aerodynamically efficient compressors, while ensuring mechanical integrity and reducing the number of experimental design validations. A variation in working fluid properties allows investigation of the contribution of blade forcing and damping while the modal response remains unchanged. Experiments have been conducted at ETH Zurich’s radial compressor facility with a state of the art industrial compressor design. Dynamic strain gauge measurements on the impeller blades were used to determine the amplitude response, damping properties and forcing at a defined resonance condition. Two working fluids have been investigated to vary compressor flow settings while the modal response remains unchanged. Unsteady flow simulations and harmonic FSI simulations were used to complement the experiments and to investigate the local blade forcing distribution, which then were linked to flow effects. Experiments showed a change in resonance amplitude up to a factor of 4 due to a change in the applied working fluid. Estimation of the damping ratio with a single degree of freedom model found the exciting force to be the main contributor to the differences in resonant response. The unsteady flow simulations were able to identify the locations on the blade surface which are responsible for the change in forcing. It was found that the forcing depends on wave propagation effects in the flow channel and on how the pressure field matches the mode shape.
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Rakhmanina, L. A., A. V. Zuev, A. Yu Petrov, A. A. Aksenov i Minh Hai Nguyen. "The investigation of absolute flow non-uniform velocity distributions influence at the centrifugal compressor axial radial impeller inlet using numerical calculation methods in ANSYS CFX". E3S Web of Conferences 140 (2019): 05008. http://dx.doi.org/10.1051/e3sconf/201914005008.
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Currently, methods of numerical modelling are widely used. They are especially widely used in the design of turbo compressors. For the specific task of designing new flowing parts of a centrifugal compressor, it is not recommended to deviate from the canonical design techniques, but it is preferable to supplement them with numerical methods. This article is devoted to the end two-element stage investigation of a centrifugal compressor with an axial radial impeller; the stage main dimensions were obtained using the method of V.F. Rice. In order to obtain the necessary pressure characteristics and determine the dependence for the absolute velocity non-uniform distribution at the inlet to the axial radial impeller, the flow path main dimensions were optimized using numerical calculation methods. The calculation was performed using the SST turbulence model using computational gas dynamics methods in the ANSYS CFX software environment. Based on the optimization results, five compressor designs and corresponding characteristics were obtained. The absolute velocity distribution nature at the inlet to the centrifugal compressor axial radial impeller for five flow path variants is investigated. Empirical dependences are obtained for the deviation of the absolute velocity at the inlet in the hub section axial radial impeller and the absolute velocity deviation at the shroud from the absolute velocity at the average diameter based on the results of a numerical experiment. Recommendations are made for further absolute velocity distributions investigating at the inlet to the compressor impeller.
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Borovkov, A. I., Yu B. Galerkin, О. А. Solovyeva, А. А. Drozdov, A. F. Rekstin, K. V. Soldatova i A. A. Sebelev. "Methodology and Experience in the Primary Designing a Transsonic Axial Compressor". Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, nr 3 (142) (wrzesień 2022): 129–50. http://dx.doi.org/10.18698/0236-3941-2022-3-129-150.
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The article considers the basic principles underlying the program for the calculation and designing gas turbine engine axial compressors. Calculation of pressure losses and deflection ability of the cascades is based on the formulas of A. Komarov. The model involves empirical coefficients, the values of which were selected during program verification based on the results of testing multistage compressors and compressor stages. The basic equations and the algorithm for calculating pressures and velocities are given under the condition of radial balance. The application of computer programs based on these models in designing a gas turbine engine four-stage compressor of moderate power with a total pressure ratio of 3.2 and a given speed is shown. For the first compressor stage, two options with different flow rates are compared. The first option was designed according to the classic recommendation to get close to the same mechanical energy of the gas at the exit of the stage along the radius. The second option was designed for a lower flow coefficient, but ensuring the radial balance, requires introducing a significant non-uniformity of mechanical energy supply along the radius. Due to the lower kinetic energy, the stage efficiency of the second variant is 1.9 % higher, despite the fact that the loss coefficients of the blade cascades are lower in the first variant. The question remains as to how much the inevitable mixing losses in the second variant will reduce its efficiency in the process of equalizing the mechanical energy of the gas
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Dunham, J. "A New Endwall Model for Axial Compressor Throughflow Calculations". Journal of Turbomachinery 117, nr 4 (1.10.1995): 533–40. http://dx.doi.org/10.1115/1.2836565.
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It is well recognized that the endwall regions of a compressor—in which the annulus wall flow interacts with the mainstream flow—have a major influence on its efficiency and surge margin. Despite many attempts over the years to predict the very complex flow patterns in the endwall regions, current compressor design methods still rely largely on empirical estimates of the aerodynamic losses and flow angle deviations in these regions. This paper describes a new phenomenological model of the key endwall flow phenomena treated in a circumferentially averaged way. It starts from Hirsch and de Ruyck’s annulus wall boundary layer approach, but makes some important changes. The secondary vorticities arising from passage secondary flows and from tip clearance flows are calculated. Then the radial interchanges of momentum, energy, and entropy arising from both diffusion and convection are estimated. The model is incorporated into a streamline curvature program. The empirical blade force defect terms in the boundary layers are selected from cascade data. The effectiveness of the method is illustrated by comparing the predictions with experimental results on both low-speed and high-speed multistage compressors. It is found that the radial variation of flow parameters is quite well predicted, and so is the overall performance, except when significant endwall stall occurs.
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Jaeschke, Andrzej, i Grzegorz Liśkiewicz. "Sensitivity Study of Greitzer Model Based on Physical System Parameters of Radial Compressing Units". Energies 13, nr 19 (1.10.2020): 5111. http://dx.doi.org/10.3390/en13195111.
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Centrifugal compressors are key elements of energy systems and industrial installations including fluid flow. Their operating range is strictly limited by the surge phenomenon. The Greitzer model is a known way of simulating the compressor’s behaviour at the surge. In this paper, the parametric study of different versions of the Greitzer model is conducted. There are several versions of this model that include 4 to 2 equation models. The system behaviour depends on the features of the compressor itself as well as of the plenum. In this paper, all terms connected with the compressor were grouped into the “Co” parameter, while those associated with the plenum were grouped into the “Pl” parameter. The study shows how each component influences the system stability. The comparison of analytical data with experimental results allowed to draw conclusions regarding the way of choosing the model parameters that provide the best simulation of the real system behaviour. The study shows that the system is well simulated by a model with relatively large values of the Lc parameter. The length of the compressor parameter Lc=3.57 m was performing well for the machine with impeller radius 0.33 m. Possible explanations of this finding are presented and compared to the state of the art. This result may provide possible help in adjusting the model parameters for other machines and designing reliable anti-surge systems based on the Greitzer model suited to energy conversion systems.
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Galerkin, Y. B., A. F. Rekstin i O. A. Solovyeva. "Selecting the Dimensions of the Vaneless Diffuser of a Centrifugal Compressor Stage at the Primary Design Phase". Proceedings of Higher Educational Institutions. Маchine Building, nr 10 (715) (październik 2019): 43–57. http://dx.doi.org/10.18698/0536-1044-2019-10-43-57.
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The advances in the primary design method of centrifugal compressors of the Universal Modeling Method have led to the need to analyze and revise the recommendations for the optimal size and configuration selection of vaneless diffusers of centrifugal compressor stages. The results of CFD calculations of a family of vaneless diffusers with different relative width, radial length, velocity coefficients and flow angles at the inlet are used to develop new recommendations. The choice of the optimal width of the vaneless diffuser is based on ensuring a non-separable flow in it at the boundary of the surge. The optimal value of the relative radial length of the diffuser is in the range of 1.65–2.0. Considering the above, a formula for selecting the vaneless diffuser outer diameter is proposed depending on the design flow rate coefficient. The developed primary design method of vaneless diffusers is included in the software programs of the Universal Modeling Method and is used in design and research practice.
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Lakshminarayana, B., M. Zaccaria i B. Marathe. "The Structure of Tip Clearance Flow in Axial Flow Compressors". Journal of Turbomachinery 117, nr 3 (1.07.1995): 336–47. http://dx.doi.org/10.1115/1.2835667.
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Detailed measurements of the flow field in the tip region of an axial flow compressor rotor were carried out using a rotating five-hole probe. The axial, tangential, and radial components of relative velocity, as well as the static and stagnation pressures, were obtained at two axial locations, one at the rotor trailing edge, the other downstream of the rotor. The measurements were taken up to about 26 percent of the blade span from the blade tip. The data are interpreted to understand the complex nature of the flow in the tip region, which involves the interaction of the tip leakage flow, the annulus wall boundary layer and the blade wake. The experimental data show that the leakage jet does not roll up into a vortex. The leakage jet exiting from the tip gap is of high velocity and mixes quickly with the mainstream, producing intense shearing and flow separation. There are substantial differences in the structure of tip clearance observed in cascades and rotors.
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Antas, Stanisław. "Exhaust System for Radial and Axial-Centrifugal Compressor with Pipe Diffuser". International Journal of Turbo & Jet-Engines 36, nr 3 (27.08.2019): 297–304. http://dx.doi.org/10.1515/tjj-2016-0068.
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Abstract The application of radial and axial-centrifugal compressors in turboprop, turboshaft and turbofan engines may require the construction of small diameters diffuser in order to obtain lower weight and smaller frontal area. Conventional exhaust diffusers typically have large outlet diameters for exit Mach numbers lower than 0,2 and low swirl flow to the combustor, hence the design of channel of the low-diameter diffusers called controlled-contour, fishtail-shaped diffuser or diffusing trumpet is complex. The cross-sectional shape of these channels is varied from circular to oval to elliptic and to rectangular. The paper presents an original method for determining the flow parameters in the channel and at the outlet section of the downstream diffusing trumpet for a pipe diffuser, which constitutes the downstream duct of the radial or axial-centrifugal compressor with the pipe diffuser. It also illustrates a new method for determining the geometrical parameters of the diffuser. Mentioned methods (for conceptual design of a compressor with pipe diffuser) are based on Pythagorean theorem, properties of ellipse, equation of continuity, energy equation, first law of thermodynamics, Euler’s moment of momentum equation, gasdynamics functions and definitions used in theory of turbo-machines.
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Hu, Li, Fu, Gu, Ren i Lu. "Numerical Investigation of Flow and Heat Transfer in a Rotor-Stator Cavity with Centripetal Carbon Dioxide Through-Flow". Energies 12, nr 13 (7.07.2019): 2613. http://dx.doi.org/10.3390/en12132613.
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A centrifugal carbon dioxide compressor is a kind of general machine with extensive applications. The geometry of the side chambers of the compressors can be determined by studying the rotor-stator cavity with centripetal through-flow. In this paper, numerical simulations were conducted to predict the characteristics of flow and heat transfer. Three different speeds of rotation and two axial gap widths were considered. The correlations of the core swirl ratios were determined by fitting the results for two axial gap widths. The amounts of the moment coefficients of the disk were predicted. In order to better analyze the temperature field, the radial distributions of the local heat transfer coefficient were numerically investigated. According to the simulation results, the average Nusselt number was found to be dominated by the turbulent flow parameter. It also seemed to be proportional to the moment coefficient at a fixed circumferential Reynolds number.
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Calvert, W. J., i R. B. Ginder. "Transonic fan and compressor design". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 213, nr 5 (1.05.1999): 419–36. http://dx.doi.org/10.1243/0954406991522671.
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Transonic fans and compressors are now widely used in gas turbine engines because of their benefits in terms of compactness and reduced weight and cost. However, careful and precise design is essential if high levels of performance are to be achieved. In this paper, the evolution of transonic compressor designs and methods is outlined, followed by more detailed descriptions of current compressor configurations and requirements and modern aerodynamic design methods and philosophies. Current procedures employ a range of methods to allow the designer to refine a new design progressively. Overall parameters, such as specific flow and mean stage loading, the axial matching between the stages at key operating conditions and the radial matching between the blade rows are set in turn, using one- and two-dimensional techniques. Finally, detailed quasi-three-dimensional and three-dimensional computational fluid dynamics (CFD) analyses are employed to refine the design. However, it is important to appreciate that the methods all have significant limitations and designers must take this into account if successful compressors are to be produced.
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Engeda, Abraham, Yunbae Kim, Ronald Aungier i Gregory Direnzi. "The Inlet Flow Structure of a Centrifugal Compressor Stage and Its Influence on the Compressor Performance". Journal of Fluids Engineering 125, nr 5 (1.09.2003): 779–85. http://dx.doi.org/10.1115/1.1601255.
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The performance of centrifugal compressors can be seriously degraded by inlet flow distortions that result from an unsatisfactory inlet configuration. In this present work, the flow is numerically simulated and the flow details are analyzed and discussed in order to understand the performance behavior of the compressor exposed to different inlet configurations. In a previous work, complementary to this present work, experimental tests were carried out for the comparison of a centrifugal compressor stage performance with two different inlet configurations: one of which was a straight pipe with constant cross-sectional area and the other a 90-deg curved pipe with nozzle shape. The comparative test results indicated significant compressor stage performance difference between the two different inlet configurations. Steady-state compressor stage simulation including the impeller and diffuser with three different inlets has been carried out to investigate the influence of each inlet type on the compressor performance. The three different inlet systems included a proposed and improved inlet model. The flow from the bend inlet is not axisymmetric in the circumferential and radial distortion, thus the diffuser and the impeller are modeled with fully 360-deg passages.
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Ziegler, Kai U., Heinz E. Gallus i Reinhard Niehuis. "A Study on Impeller-Diffuser Interaction—Part II: Detailed Flow Analysis". Journal of Turbomachinery 125, nr 1 (1.01.2003): 183–92. http://dx.doi.org/10.1115/1.1516815.
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The interaction between impeller and diffuser is considered to have strong influence on the flow in centrifugal compressors. However, the knowledge about this influence is still not satisfying. This two-part paper presents an experimental investigation of the effect of impeller-diffuser interaction on the unsteady and the time-averaged flow field in impeller and diffuser and the performance of these components. The flat wedge vaned diffuser of the investigated compressor allows an independent adjustment of diffuser vane angle and radial gap between impeller exit and diffuser vane inlet. Attention is mainly directed to the radial gap, as it determines the intensity of the impeller-diffuser interaction. In Part I it was shown that smaller radial gaps improve diffuser pressure recovery, whereas impeller efficiency is hardly affected. Part II focuses on the reasons for these effects. Measurements with a laser-2-focus velocimeter in the highly unsteady flow field between the impeller exit region and diffuser throat were performed at three different diffuser geometries allowing a detailed flow analysis. Especially the unsteady results show that for a smaller radial gap more impeller wake fluid is conveyed towards the highly loaded diffuser vane pressure side reducing its loading and leading to a better diffusion in the diffuser channel. Concerning the impeller flow, it was found that a smaller radial gap is leading to a noticeable reduction of the wake region at impeller exit. The experimental results are intended to be published as an open CFD test case under the name “Radiver.”
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Rabas, T. J., C. B. Panchal i H. C. Stevens. "Integration and Optimization of the Gas Removal System for Hybrid-Cycle OTEC Power Plants". Journal of Solar Energy Engineering 112, nr 1 (1.02.1990): 19–28. http://dx.doi.org/10.1115/1.2930753.
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A preliminary design of the noncondensible gas removal system for a 10 MWe, land-based hybrid-cycle OTEC power plant has been developed and is presented herein. This gas removal system is very different from that used for conventional power plants because of the substantially larger and continuous noncondensible gas flow rates and lower condenser pressure levels which predicate the need for higher-efficiency components. Previous OTEC studies discussed the need for multiple high-efficiency compressors with intercoolers; however, no previous design effort was devoted to (a) the details of the intercoolers, (b) integration and optimization of the intercoolers with the compressors, and (c) the practical design constraints and feasibility issues of these components. The resulting gas removal system design uses centrifugal (radial) compressors with matrix-type crossflow aluminum heat exchangers as intercoolers. Once-through boiling of ammonia is used as the heat sink for the cooling and condensing of the steam-gas mixture. A computerized calculation method was developed for the performance analysis and subsystem optimization. For a specific number of compressor units and the stream arrangement, the method is used to calculate the dimensions, speeds, power requirements, and costs of all the components.
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Shade, W. N., i D. E. Hampshire. "An Experimental Investigation of Oil-Buffered Shaft Seal Flow Rates". Journal of Engineering for Gas Turbines and Power 107, nr 1 (1.01.1985): 170–80. http://dx.doi.org/10.1115/1.3239679.
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An experimental investigation was conducted to identify an optimum oil-buffered shaft seal for use on centrifugal compressors, with the primary objective being minimal seal oil exposure to process gases that cause seal oil degradation or are toxic. Types of seals tested included smooth bore cylindrical bushings, spiral groove cylindrical bushings, radial outward-flow face seals, and radial inward-flow face seals. The influence of shaft speed, gas pressure, seal oil differential pressure, oil bypass flow rate, and oil supply temperature on process side seal oil flow rate was determined. The investigation revealed some surprising relationships between seal oil flow rates and the escape of process gas.
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Margalida, Gabriel, Pierric Joseph, Olivier Roussette i Antoine Dazin. "Comparison and Sensibility Analysis of Warning Parameters for Rotating Stall Detection in an Axial Compressor". International Journal of Turbomachinery, Propulsion and Power 5, nr 3 (7.07.2020): 16. http://dx.doi.org/10.3390/ijtpp5030016.
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The present paper aims at evaluating the surveillance parameters used for early stall warning in axial compressors, and is based on unsteady pressure measurements at the casing of a single stage axial compressor. Two parameters—Correlation and Root Mean Square (RMS)—are first compared and their relative performances discussed. The influence of sensor locations (in both radial and axial directions) is then considered, and the role of the compressor’s geometrical irregularities in the behavior of the indicators is clearly highlighted. The influence of the throttling process is also carefully analyzed. This aspect of the experiment’s process appears to have a non-negligible impact on the stall warning parameters, despite being poorly documented in the literature. This last part of this research work allow us to get a different vision of the alert parameters compared to what is classically done in the literature, as the level of irregularity that is reflected by the magnitude of the parameters appears to be an image of a given flow rate value, and not a clear indicator of the stall inception.
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Kalinkevych, M., V. Ihnatenko, O. Bolotnikova i O. Obukhov. "Design of high efficiency centrifugal compressors stages". Refrigeration Engineering and Technology 54, nr 5 (31.10.2018): 4–9. http://dx.doi.org/10.15673/ret.v54i5.1239.
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The modern trend in compressor industry is an extension of the use of multi-shaft centrifugal compressors. Multi-shaft compressors have a number of advantages over single-shaft. The design of such compressors gives opportunity to use an axial inlet for all stages and select the optimum rotational speed for each pair of impellers, which, along with the cooling of the gas after each stage, makes possible to achieve high levels of efficiency. The design of high-efficiency centrifugal compressor stages can be performed on the basis of highly effective stage elements. Such elements are: impellers with spatial blades, vaned and channel diffusers with given velocity distribution. In this paper, impellers with axial-radial blades are considered. The blade profile is determined by the specified pressure distribution along the blade. Such design improves the structure of the gas flow in the interblade channels of the impeller, which leads to an increase in its efficiency. Characteristics of loss coefficients from attack angles for impellers were obtained experimentally. Vaned and channel diffusers, the characteristics of which are given in this article, are designed with the given velocity distribution along the vane. Compared to the classic type of diffuser, such diffusers have lower losses and a wider range of economical operation. For diffusers as well as for impellers, characteristics of loss coefficients from attack angles were obtained. High efficient impellers and diffusers and obtained gas-dynamic characteristics were used in the design of a multi-shaft compressor unit for the production of liquefied natural gas. The initial pressure of the unit is 3bar. The obtained characteristics of loss coefficients from attack angles for the considered impellers and diffusers make it possible to calculate the gas-dynamic characteristics of high-efficient centrifugal compressors stages. The high-efficient centrifugal compressors stages can be designed using high-efficient elements, such as: impeller with spatial blades and vaned diffuser with given velocity distribution.
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Li, Y. S., i N. A. Cumpsty. "Mixing in Axial Flow Compressors: Part II—Measurements in a Single-Stage Compressor and a Duct". Journal of Turbomachinery 113, nr 2 (1.04.1991): 166–72. http://dx.doi.org/10.1115/1.2929076.
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This paper follows directly from Part I, which contains not only the description of the facilities and the results for the C106 four-stage compressor, but also the background, list of nomenclature, acknowledgments, and references. The discussion and conclusions for Parts I and II are given here. The single-stage compressor results show the significant effects of inlet guide vane (IGV) wakes on mixing across the stage in the so-called “free-stream” region; in the casing region tip clearance flow is shown to play an important role in mixing. Explanations for these results are given. Investigations were also carried out in a two-dimensional rectangular duct flow to reveal the mixing mechanism in the corner region similar to those formed by blade surfaces and endwalls in a compressor. Turbulent diffusion has been found to be the dominant mechanism in spanwise mixing; anisotropic inhomogeneous turbulent diffusion is mainly responsible for the nonuniform mixing in the corner region. The larger spread of tracer gas in the tangential direction than in the radial direction is mainly caused by the wake dispersion and relative flow motions within the blade wakes as well as secondary flow contributions in the end-wall regions.
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Skoch, Gary J. "Experimental Investigation of Diffuser Hub Injection to Improve Centrifugal Compressor Stability". Journal of Turbomachinery 127, nr 1 (1.01.2005): 107–17. http://dx.doi.org/10.1115/1.1812779.
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Results from a series of experiments to investigate whether centrifugal compressor stability could be improved by injecting air through the diffuser hub surface are reported. The research was conducted in a 4:1 pressure ratio centrifugal compressor configured with a vane-island diffuser. Injector nozzles were located just upstream of the leading edge of the diffuser vanes. Nozzle orientations were set to produce injected streams angled at −8, 0, and +8 degrees relative to the vane mean camber line. Several injection flow rates were tested using both an external air supply and recirculation from the diffuser exit. Compressor flow range did not improve at any injection flow rate that was tested, and generally diminished as injection rate increased. Compressor flow range did improve slightly at zero injection due to the flow resistance created by injector openings on the hub surface. Resistance and flow range both increased as the injector orientation was turned toward radial. Leading edge loading and semivaneless space diffusion showed trends that are similar to those reported earlier from shroud surface experiments that did improve compressor range. Opposite trends are seen for hub injection cases where compressor flow range decreased. The hub injection data further explain the range improvement provided by shroud-side injection and suggest that stability factors cited in the discussion of shroud surface techniques are valid. The results also suggest that a different application of hub-side techniques may produce a range improvement in centrifugal compressors.
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Piesche, M., i L. Blum. "On compressible subsonic flow between impeller and casing of radial-flow compressors with superposed throughflow". Acta Mechanica 57, nr 3-4 (grudzień 1985): 159–66. http://dx.doi.org/10.1007/bf01176915.
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Dong, Y., S. J. Gallimore i H. P. Hodson. "Three-Dimensional Flows and Loss Reduction in Axial Compressors". Journal of Turbomachinery 109, nr 3 (1.07.1987): 354–61. http://dx.doi.org/10.1115/1.3262113.
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Measurements have been performed in a low-speed high-reaction single-stage axial compressor. Data obtained within and downstream of the rotor, when correlated with the results of other investigations, provide a link between the existence of suction surface–hub corner separations, their associated loss mechanisms, and blade loading. Within the stator, it has been shown that introducing a small clearance between the stator blade and the stationary hub increases the efficiency of the stator compared to the case with no clearance. Oil flow visualizaton indicated that the leakage reduced the extensive suction surface–hub corner separation that would otherwise exist. A tracer gas experiment showed that the large radial shifts of the surface streamlines indicated by the oil flow technique were only present close to the blade. The investigation demonstrates the possible advantages of including hub clearance in axial flow compressor stator blade rows.
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Dring, R. P. "Radial Transport and Momentum Exchange in an Axial Compressor". Journal of Turbomachinery 115, nr 3 (1.07.1993): 477–86. http://dx.doi.org/10.1115/1.2929278.
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The objective of this work was to examine radial transport in axial compressors from two perspectives. The first was to compare the mixing coefficient based on a secondary flow model (using measured radial velocities) with that based on a turbulent diffusion model. The second was to use measured airfoil pressure forces and momentum changes to assess the validity of the assumption of diffusive radial transport, which is common to both models. These examinations were carried out at both design and off-design conditions as well as for two rotor tip clearances. In general it was seen that radial mixing was strongest near the hub and that it increased dramatically at near-stall conditions. It was also seen that radial transport could cause large differences (≈ 100 percent) between the force on an airfoil and the change in momentum across the airfoil at the same spanwise location.
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Flete, Xavier, Nicolas Binder, Yannick Bousquet i Sandrine Cros. "Numerical Investigation of Rotating Instability Development in a Wide Tip Gap Centrifugal Compressor". International Journal of Turbomachinery, Propulsion and Power 8, nr 3 (1.08.2023): 25. http://dx.doi.org/10.3390/ijtpp8030025.
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In the current study, full-stage unsteady simulations were performed to investigate rotating instability inception mechanisms in a particularly large tip clearance centrifugal compressor with a vaneless diffuser and a volute. Four operating points along a speed line were analysed to understand the influence of the mass flow reduction on flow structures. Close to the peak efficiency, an unsteady interaction between the tip clearance vortices and splitter blades was observed. Considering other studies, the influence of the tip gap size was analysed. Then, a large-scale vortex shedding from the leading edges of the main blades was detected when the stage operated near the maximum pressure ratio. It was demonstrated that shed vortices were caused by the combination of the radial gradient of the tangential velocity under the tip vortex and the reverse backflow near the casing. Previous studies on axial compressors refer to these vortical structures as backflow vortices. These vortices cause a significant increase in the incidence angle in the tip region.
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Han, Ge, Xingen Lu, Yanfeng Zhang, Shengfeng Zhao, Chengwu Yang i Junqiang Zhu. "Investigation of two pipe diffuser configurations for a compact centrifugal compressor". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, nr 4 (5.01.2017): 716–28. http://dx.doi.org/10.1177/0954410016685585.
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Diffusers are one of the most important factors determining the centrifugal compressor performance. The present work is aimed at providing a detailed understanding of the underlying flow and loss mechanisms in three different diffusers in a compact centrifugal compressor stage. Experimental and computational studies were conducted for various diffuser configurations, e.g. two pipe diffusers and one wedge diffuser, while keeping the throat in all the three geometries. It was found that both the pipe diffuser configurations had better aerodynamic performance than the original wedge diffuser. Furthermore, the pipe diffuser with a fishtail arrangement exhibited greater performance improvement, but had more distortion outflow than the wedge diffuser and the radial pipe diffuser because of the strong jet and wake structure caused by the fishtail turn. Nevertheless, the fishtail configuration has a smaller discharge swirl angle, which would have a positive impact on the performance of the combustor. As a result, the fishtail pipe diffuser configuration was recommended in compact centrifugal compressors.
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Wennerstrom, A. J. "A Review of Predictive Efforts for Transport Phenomena in Axial Flow Compressors". Journal of Turbomachinery 113, nr 2 (1.04.1991): 175–79. http://dx.doi.org/10.1115/1.2929080.
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Transport phenomena as they apply to throughflow calculations in axial-flow compressors are reviewed. An historical background is presented. Then the debate raised by the Adkins and Smith versus the Gallimore and Cumpsty approaches to radial transport is discussed. This debate was resolved in that it was finally concluded that both turbulent transport and convective secondary flows play a role in spanwise transport. Other major related efforts mentioned are those of Hirsch and his colleagues and Papailiou and his colleagues. Readers are encouraged to reconsider exploitation of the work of Kerrebrock and Mikolajczak concerning circumferential transport. Comments on future trends are offered.
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Drozdov, A. A., Y. B. Galerkin i A. A. Utsekhovskiy. "Development and Implementation of a New Mathematical Model of the Tangential Exit Nozzles in Centrifugal Compressors". Proceedings of Higher Educational Institutions. Маchine Building, nr 06 (723) (czerwiec 2020): 17–35. http://dx.doi.org/10.18698/0536-1044-2020-6-17-35.
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Various engineering techniques are used for optimal gas-dynamic design of centrifugal compressors. This includes a universal modelling method that consists of software programs developed at Peter the Great St. Petersburg Polytechnic University. Tangential exit nozzles are elements of the centrifugal compressor flow path. The analysis of the results of the tangential exit nozzle calculations using the current mathematical model showed a need of improvement. The following main provisions formed a basis for a new model: the size of the passage is determined using the flow rate equation at the entrance and exit of the output unit (the calculated cross sections should be increased by 25–35% according to the recognized recommendations by Russian experts); the real nature of the flow in the output unit is taken into account by introducing an empirical coefficient in the equation of the circumferential component of velocity; the output diffuser is designed taking into account the optimal angle of expansion of an equivalent conical diffuser; the scroll tongue is shifted from a section with an angle of expansion of 0° to a section with an angle of expansion of 30°, which aids levelling the circumferential flow parameters and reduces total losses. To simplify the calculation process, a constant density along the scroll length is adopted in the mathematical model. The circumferential component of velocity is also determined approximately using the flow continuity equation without taking viscosity into account. Losses in scrolls and annular chambers are calculated in the radial and meridional planes. In the radial plane, the main losses are friction losses, whereas in the meridional plane, the main losses are due to expansion. For a trapezoid scroll, these pressure losses are determined depending on the scroll’s expansion angle. In the off-design operating modes, incidental losses due to impact flow around the scroll tongue are added. The presented model was implemented in the new version of the universal modeling method. The mathematical model was identified by the results of the commissioning test of the turboexpanders and turbochargers.
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Ma, Y., A. Engeda, M. Cave i J.-L. Di Liberti. "Improved centrifugal compressor impeller optimization with a radial basis function network and principle component analysis". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, nr 4 (1.04.2010): 935–45. http://dx.doi.org/10.1243/09544062jmes1635.
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The development of a fast and reliable computer-aided design and optimization procedure for centrifugal compressors has attracted a great deal of attention both in the industry and in academia. Artificial neural networks (ANNs) have been widely used to create an approximate performance map to substitute the direct application of flow solvers in the optimization procedure. Although ANNs greatly decrease the computational time for the optimization, their accuracies still limit their applications. Furthermore, ANNs also bring errors to the final results. In this study, principal component analysis (PCA) or independent component analysis (ICA) is applied to transform the training database and make a radial basis function network (RBFN), a type of ANN, trained in a new coordinate system. The present study compares the accuracies of three different trained ANNs: RBFN, RBFN with PCA, and RBFN with ICA. Furthermore, the total performances of the centrifugal compressor impeller optimization procedures using these three different trained ANNs are compared. Genetic algorithm (GA) is used as an optimization method in the optimization procedure and influences of GA parameters on the optimization procedure performances are also studied. All results demonstrate that the application of PCA significantly increases the accuracy of trained ANN as well as the total performance of the centrifugal compressor impeller optimization procedure.
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Schröder, Tilman, Sebastian Schuster i Dieter Brillert. "Experimental Investigation of Centrifugal Flow in Rotor–Stator Cavities at High Reynolds Numbers >108". International Journal of Turbomachinery, Propulsion and Power 6, nr 2 (26.05.2021): 13. http://dx.doi.org/10.3390/ijtpp6020013.
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The designers of radial turbomachinery need detailed information on the impact of the side chamber flow on axial thrust and torque. A previous paper investigated centripetal flow through narrow rotor–stator cavities and compared axial thrust, rotor torque and radial pressure distribution to the case without through-flow. Consequently, this paper extends the investigated range to centrifugal through-flow as it may occur in the hub side chamber of radial turbomachinery. The chosen operating conditions are representative of high-pressure centrifugal compressors used in, for example, carbon capture and storage applications as well as hydrogen compression. To date, only the Reynolds number range up to Re=2·107 has been investigated for centrifugal through-flow. This paper extends the range to Reynolds numbers of Re=2·108 and reports results of experimental and numerical investigations. It focuses on the radial pressure distribution in the rotor–stator cavity and shows the influence of the Reynolds number, cavity width and centrifugal mass flow rate. It therefore extends the range of available valid data that can be used to design radial turbomachinery. Additionally, this analysis compares the results to data and models from scientific literature, showing that in the higher Reynolds number range, a new correlation is required. Finally, the analysis of velocity profiles and wall shear delineates the switch from purely radial outflow in the cavity to outflow on the rotor and inflow on the stator at high Reynolds numbers in comparison to the results reported by others for Reynolds numbers up to Re=2·107.
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Frank, Roman G., Christian Wacker i Reinhard Niehuis. "Loss Characterization of a Conventional Variable Inlet Guide Vane". International Journal of Turbomachinery, Propulsion and Power 6, nr 3 (26.07.2021): 30. http://dx.doi.org/10.3390/ijtpp6030030.
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Variable inlet guide vanes (VIGVs) are most commonly used as the major control unit of integrally geared centrifugal compressors (IGCCs). In order to enhance the efficient operating range of the compressor, the loss mechanisms and utilization limits of state-of-the-art VIGVs need to be better understood. Field measurements in the wake of a typical, commercially used configuration were therefore conducted at the VIGV test facility of the Bundeswehr University Munich. The investigations were carried out at application oriented subsonic flow conditions and stagger angles from 50∘ to 90∘ covering the full low-loss operating range, including the limits of efficient operation. For a precise local loss characterization, an inflow correlation was developed and applied to consider total pressure inhomogeneities caused by the radial inflow velocity profile and minor circumferential velocity deviations. Contrary to previous research efforts, not only the profile losses, but also the secondary flow losses induced by the open blade tips and wall-blade interactions were resolved in full detail. For this reason, a more precise and comprehensive loss assessment of realistic VIGV cascades is acquired.
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Dragan, Valeriu, Oana Dumitrescu, Ion Malael i Adrian Daniel Azoitei. "Rake impact on turboshaft compressors, a numerical study". Aircraft Engineering and Aerospace Technology 92, nr 8 (29.06.2020): 1169–76. http://dx.doi.org/10.1108/aeat-01-2020-0022.
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Purpose Turboshaft engines usually include one centrifugal compressor due to its high-pressure ratio, stability and compactness. Many designers rely on positive raking to decrease tip gap flow and therefore losses. However recent optimization studies revealed geometries contradicting this canonic view. Hence, this paper aims to investigate how the rake angle alone can influence performance and to which extent. Design/methodology/approach A turboshaft representative impeller was chosen and altered for null and +/−30° rake angles. Menter's shear stress transport model is used for steady computational fluid dynamics simulations, sweeping the nominal speedline at various tip clearances. Backsweep distribution is identical in all cases, isolating rake influence. Findings Pressure ratio was lowered for the both positively and negatively raked blades, but through distinct aerodynamic mechanisms. Although the flow through the tip gap was lower for the positive rake, this is due to lower blade loading. Splitter comparison reveal that these effects are more pronounced in the radial regions. Practical implications Some of the findings may extend beyond turboshaft engines, into turbochargers, home appliances or industrial blowers. However, all extrapolations must consider specific differences between these applications. Turboshaft compressors designers can benefit from this study when setting up their free parameters and penalty functions in the early concept stages. Originality/value Only few similar studies can be found in the literature to date, none similar to turboshaft applications. Also, this impeller is designed to eliminate leading edge shocks and suction side boundary layer separation, which makes it easier to isolate the tip gap flow effects. The authors also provide a framework on which semi-empirical design equations can be further developed to incorporate rake into 1D design tools.