Journal articles: 'Axial turbine stage'

1

Goodisman, M. I., M. L. G. Oldfield, R. C. Kingcombe, T. V. Jones, R. W. Ainsworth, and A. J. Brooks. "An Axial Turbobrake." Journal of Turbomachinery 114, no. 2 (April 1, 1992): 419–25. http://dx.doi.org/10.1115/1.2929160.

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The “Axial Turbobrake” (patent applied for) is a novel turbomachine that can be used to absorb power generated by test turbines. Unlike a compressor, there is no pressure recovery through the turbobrake. This simplifies the aerodynamic design and enables high-stage loadings to be achieved. The blades used have high-turning two-dimensional profiles. This paper describes a single-stage axial turbobrake, which is driven by the exhaust gas of the test turbine and is isolated from the turbine by a choked throat. In this configuration no fast-acting controls are necessary as the turbobrake operates automatically with the turbine flow. Tests on a 0.17 scale model show that the performance is close to that predicted by a simple two-dimensional theory, and demonstrate that the turbobrake power absorption can be controlled and hence matched to that typically produced by the first stage of a modern highly loaded transonic turbine. A full-size axial turbobrake will be used in a short-duration rotating turbine experiment in an Isentropic Light Piston Tunnel at RAE Pyestock.

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Klimko, Marek, Pavel Žitek, and Richard Lenhard. "Measurement on Axial Reaction Turbine Stage." MATEC Web of Conferences 328 (2020): 03013. http://dx.doi.org/10.1051/matecconf/202032803013.

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This article describes a measuring methods and evaluating measured data on a single-stage axial turbine with reaction (~ 50 %). One turbine operating mode was selected, in which the traversing behind the nozzle and bucket with two 5-hole pneumatic probes took place. The results are distributions of flow angles, reactions, or losses distribution/efficiencies along the blades.

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Touil, Kaddour, and Adel Ghenaiet. "Blade stacking and clocking effects in two-stage high-pressure axial turbine." Aircraft Engineering and Aerospace Technology 91, no. 8 (September 2, 2019): 1133–46. http://dx.doi.org/10.1108/aeat-03-2018-0110.

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Purpose The purpose of this paper is to characterize the blade–row interaction and investigate the effects of axial spacing and clocking in a two-stage high-pressure axial turbine. Design/methodology/approach Flow simulations were performed by means of Ansys-CFX code. First, the effects of blade–row stacking on the expansion performance were investigated by considering the stage interface. Second the axial spacing and the clocking positions between successive blade–rows were varied, the flow field considering the frozen interface was solved, and the flow interaction was assessed. Findings The axial spacing seems affecting the turbine isentropic efficiency in both design and off-design operating conditions. Besides, there are differences in aerodynamic loading and isentropic efficiency between the maximum efficiency clocking positions where the wakes of the first-stage vanes impinge around the leading edge of the second-stage vanes, compared to the clocking position of minimum efficiency where the ingested wakes pass halfway of the second-stage vanes. Research limitations/implications Research implications include understanding the effects of stacking, axial spacing and clocking in axial turbine stages, improving the expansion properties by determining the adequate spacing and locating the leading edge of vanes and blades in both first and second stages with respect to the maximum efficiency clocking positions. Practical implications Practical implications include improving the aerodynamic design of high-pressure axial turbine stages. Originality/value The expansion process in a two-stage high-pressure axial turbine and the effects of blade–row spacing and clocking are elucidated thoroughly.

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Gregory, Brent A. "How Many Turbine Stages?" Mechanical Engineering 139, no. 05 (May 1, 2017): 56–57. http://dx.doi.org/10.1115/1.2017-may-5.

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This article discusses various stages of turbines and the importance of having more stages in turbine design. The article also highlights reasons that determine the designer’s choice to select the number of turbine stages for a given design of gas turbine. The highest performance turbines are defined by lower work requirements and slower velocities in the gas path. The fundamental factors determining performance might be relegated to only two factors: demand on the turbine and axial velocity. Aircraft engine technologies drive new initiatives because of the need to increase firing temperature and dramatically improve efficiency for substantially less weight. Also, the expansion across each stage determined the annulus area so that the optimums implied by the Pearson chart were largely ignored in the article. Developments in aircraft engine gas turbines have forced heavy frame gas turbines’ original equipment manufacturers to rethink many historical paradigms.

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Koprowski, Arkadiusz, and Romuald Rządkowski. "Optimization of Curtis stage in 1 MW steam turbine." E3S Web of Conferences 137 (2019): 01039. http://dx.doi.org/10.1051/e3sconf/201913701039.

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When operating at 3000 rpm, small turbines do not require a gear box and the generator does not require complex electronic software. This paper analyses the various geometries of the Curtis stage, comprising two rotor and stator blades with and without an outlet, from the efficiency point of view. Presented are 3D steady viscous flows. The results were compared with the performance of an axial turbine.

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Agbadede, Roupa, Dennis Uwakwe, and Isaiah Allison. "Preliminary Re-design of an Axial Turbine in an Existing Engine to Meet the Increased Load Demand." European Journal of Engineering Research and Science 5, no. 11 (November 24, 2020): 1360–64. http://dx.doi.org/10.24018/ejers.2020.5.11.2141.

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This work presents a preliminary design of an axial turbine section in an industrial gas turbine. The design was necessitated following the need to provide a gas turbine of a power output in the range of 48 to 60MW for a mini-city harbouring an oil rig, which was not possible with the old engine. The turbine section is designed to produce a power capable of driving the compressor as well as produce a useful power for electricity. Using proprietary gas turbine performance simulation software called TURBOMATCH and a computer program written in Microsoft Excel, a redesign of the axial turbine component was achieved. Consequent upon redesigning the axial turbine, a preliminary analysis was carried out to ascertain the new turbine stages introduced. The analysis revealed that when one or two turbine stage(s) was used for new engine, it proved unsatisfactory as the blade loading coefficient and the flow efficiency were both beyond the limit acceptable for an optimum performance. A three stage turbine was finally employed having provided a loading coefficient of 2.1, 1.9 and 1.7 for the first, second and the last stages respectively.

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Agbadede, Roupa, Dennis Uwakwe, and Isaiah Allison. "Preliminary Re-design of an Axial Turbine in an Existing Engine to Meet the Increased Load Demand." European Journal of Engineering and Technology Research 5, no. 11 (November 24, 2020): 1360–64. http://dx.doi.org/10.24018/ejeng.2020.5.11.2141.

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This work presents a preliminary design of an axial turbine section in an industrial gas turbine. The design was necessitated following the need to provide a gas turbine of a power output in the range of 48 to 60MW for a mini-city harbouring an oil rig, which was not possible with the old engine. The turbine section is designed to produce a power capable of driving the compressor as well as produce a useful power for electricity. Using proprietary gas turbine performance simulation software called TURBOMATCH and a computer program written in Microsoft Excel, a redesign of the axial turbine component was achieved. Consequent upon redesigning the axial turbine, a preliminary analysis was carried out to ascertain the new turbine stages introduced. The analysis revealed that when one or two turbine stage(s) was used for new engine, it proved unsatisfactory as the blade loading coefficient and the flow efficiency were both beyond the limit acceptable for an optimum performance. A three stage turbine was finally employed having provided a loading coefficient of 2.1, 1.9 and 1.7 for the first, second and the last stages respectively.

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8

Salah, Salma I., Mahmoud A. Khader, Martin T. White, and Abdulnaser I. Sayma. "Mean-Line Design of a Supercritical CO2 Micro Axial Turbine." Applied Sciences 10, no. 15 (July 23, 2020): 5069. http://dx.doi.org/10.3390/app10155069.

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Supercritical carbon dioxide (sCO2) power cycles are promising candidates for concentrated-solar power and waste-heat recovery applications, having advantages of compact turbomachinery and high cycle efficiencies at heat-source temperature in the range of 400 to 800 ∘C. However, for distributed-scale systems (0.1–1.0 MW) the choice of turbomachinery type is unclear. Radial turbines are known to be an effective machine for micro-scale applications. Alternatively, feasible single-stage axial turbine designs could be achieved allowing for better heat transfer control and improved bearing life. Thus, the aim of this study is to investigate the design of a single-stage 100 kW sCO2 axial turbine through the identification of optimal turbine design parameters from both mechanical and aerodynamic performance perspectives. For this purpose, a preliminary design tool has been developed and refined by accounting for passage losses using loss models that are widely used for the design of turbomachinery operating with fluids such as air or steam. The designs were assessed for a turbine that runs at inlet conditions of 923 K, 170 bar, expansion ratio of 3 and shaft speeds of 150k, 200k and 250k RPM respectively. It was found that feasible single-stage designs could be achieved if the turbine is designed with a high loading coefficient and low flow coefficient. Moreover, a turbine with the lowest degree of reaction, over a specified range from 0 to 0.5, was found to achieve the highest efficiency and highest inlet rotor angles.

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Němec, Martin, and Tomáš Jelínek. "Adaptable test rig for two-stage axial turbine." MATEC Web of Conferences 345 (2021): 00022. http://dx.doi.org/10.1051/matecconf/202134500022.

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This contribution describes a new test rig for a two-stage axial turbine built in the VZLÚ. The test rig has replaced an original facility used for a full stage aerodynamics investigation. The motivation for the design of the new test facility was the limitations of the original one. The design is briefly discussed, and then the first measurement results are presented. The first operation was performed with a turbine stage already measured in the original facility. This allows the comparison of the most important quantities.

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Jelínek, Tomáš, and Martin Němec. "Investigation of unsteady flow in axial turbine stage." EPJ Web of Conferences 25 (2012): 01035. http://dx.doi.org/10.1051/epjconf/20122501035.

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11

Tournier, Jean-Michel, and Mohamed S. El-Genk. "Axial flow, multi-stage turbine and compressor models." Energy Conversion and Management 51, no. 1 (January 2010): 16–29. http://dx.doi.org/10.1016/j.enconman.2009.08.005.

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12

Benvenuti, Erio. "Design and Test of a New Axial Compressor for the Nuovo Pignone Heavy-Duty Gas Turbines." Journal of Engineering for Gas Turbines and Power 119, no. 3 (July 1, 1997): 633–39. http://dx.doi.org/10.1115/1.2817031.

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This axial compressor design was primarily focused to increase the power rating of the current Nuovo Pignone PGT10 Heavy-Duty gas turbine by 10 percent. In addition, the new 11-stage design favorably compares with the existing 17-stage compressor in terms of simplicity and cost. By scaling the flowpath and blade geometry, the new aerodynamic design can be applied to gas turbines with different power ratings as well. The reduction in the stage number was achieved primarily through the meridional flowpath redesign. The resulting higher blade peripheral speeds achieve larger stage pressure ratios without increasing the aerodynamic loadings. Wide chord blades keep the overall length unchanged thus assuring easy integration with other existing components. The compressor performance map was extensively checked over the speed range required for two-shaft gas turbines. The prototype unit was installed on a special PGT10 gas turbine setup, that permitted the control of pressure ratio independently from the turbine matching requirements. The flowpath instrumentation included strain gages, dynamic pressure transducers, and stator vane leading edge aerodynamic probes to determine individual stage characteristics. The general blading vibratory behavior was proved fully satisfactory. With minor adjustments to the variable stator settings, the front stage aerodynamic matching was optimized and the design performance was achieved.

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13

Jiang, Liu, Guo Zhiping, Miao Shujing, He Xiangxin, and Zhu Xinyu. "Research on aerodynamic characteristics of two-stage axial micro air turbine spindle for small parts machining." Advances in Mechanical Engineering 12, no. 12 (December 2020): 168781402098437. http://dx.doi.org/10.1177/1687814020984373.

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In order to meet the requirements of output torque, efficiency and compact shape of micro-spindles for small parts machining, a two-stage axial micro air turbine spindle with an axial inlet and outlet is proposed. Based on the k-ω turbulence model of SST, the flow field and operation characteristics of the two-stage axial micro air turbine spindle were studied using computational fluid dynamics (CFD) combined with an experimental study. We obtained the air turbine spindle under different working conditions of the loss and torque characteristics. When the inlet pressure was 300 KPa, the output speed of the two-stage turbine was 100,000 rpm, 9% higher than that of a single-stage turbine output torque. The total torque reached 6.39 N·mm, and the maximum efficiency of the turbine and the spindle were 42.2% and 32.3%, respectively. Through the research on the innovative structure of the two-stage axial micro air turbine spindle, the overall performance of the principle prototype has been significantly improved and the problems of insufficient output torque and low working efficiency in high-speed micro-machining can be solved practically, which laid a solid foundation for improving the machining efficiency of small parts and reducing the size of micro machine tool.

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14

Peng, Ningjian, Enhua Wang, and Hongguang Zhang. "Preliminary Design of an Axial-Flow Turbine for Small-Scale Supercritical Organic Rankine Cycle." Energies 14, no. 17 (August 25, 2021): 5277. http://dx.doi.org/10.3390/en14175277.

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A small-scale organic Rankine cycle (ORC) with kW-class power output has a wide application prospect in industrial low-grade energy utilization. Increasing the expansion pressure ratio of small-scale ORC is an effective approach to improve the energy efficiency. However, there is a lack of suitable expander for small-scale ORC that can operate with a high efficiency under the condition of large expansion pressure ratio and small mass flow rate. Aiming at the design of high-efficiency axial-flow turbine in small ORC system, this paper investigates the performance of a kW-class axial-flow turbine and proposes a method for efficiency improvement. First, the preliminary design of an axial-flow turbine is conducted to optimize the geometric parameters and aerodynamic parameters. Then, the effects of tip clearance and trailing edge thickness on turbine performance are analyzed under design and off-design conditions. The results show that the efficiency of the two-stage or three-stage turbine is evidently better than that of the single-stage one. The output power and efficiency of the three-stage turbine are close to that of the two-stage turbine while the speed is lower. Meanwhile, the trailing edge loss and leakage loss can be significantly reduced via reducing the trailing edge thickness and tip clearance, and thus the turbine efficiency can be improved significantly. The estimated efficiency arrives at 0.82, which is 33% higher than that of the conventional turbine. Considering the limitation of turbine speed, three-stage axial-flow turbine is a feasible choice to improve turbine efficiency in a small-scale ORC.

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Klimko, Marek, Richard Lenhard, Pavel Žitek, and Katarína Kaduchová. "Experimental Evaluation of Axial Reaction Turbine Stage Bucket Losses." Processes 9, no. 10 (October 13, 2021): 1816. http://dx.doi.org/10.3390/pr9101816.

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The article describes the measurement methods and data evaluation from a single-stage axial turbine with high reaction (50%). Four operating modes of the turbine were selected, in which the wake traversing behind nozzle and bucket with five-hole pneumatic probes took place. The article further focuses on the evaluation of bucket losses for all four measured operating modes, including the analysis of measurement uncertainties.

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Klimko, Marek, Richard Lenhard, Pavel Žitek, and Katarína Kaduchová. "Experimental Evaluation of Axial Reaction Turbine Stage Bucket Losses." Processes 9, no. 10 (October 13, 2021): 1816. http://dx.doi.org/10.3390/pr9101816.

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The article describes the measurement methods and data evaluation from a single-stage axial turbine with high reaction (50%). Four operating modes of the turbine were selected, in which the wake traversing behind nozzle and bucket with five-hole pneumatic probes took place. The article further focuses on the evaluation of bucket losses for all four measured operating modes, including the analysis of measurement uncertainties.

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17

Rao, K. V. J., S. Kolla, Ch Penchalayya, M. Ananda Rao, and J. Srinivas. "Optimum stage design in axial-flow gas turbines." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 216, no. 6 (September 1, 2002): 433–45. http://dx.doi.org/10.1243/095765002761034203.

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This paper proposes the formulation and solution procedures in the stage optimization of the effective dimensions of an axial-flow gas turbine. Increasing the stage efficiency and minimizing the overall mass of components per stage are the common objectives in gas turbine design. This multiple objective function, with important constraints like natural frequency limits, root stress values, and tip deflection in blades, constitutes the overall optimization problem. The problem is solved by using a modified nonlinear simplex method with a built-in user interactive program that helps in on-line modifications of parameters other than variables in the problem. Results are presented with single objective and multiple objective criteria, including sensitivity analyses about the optimum point.

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Panayides, Pesyridis, and Saravi. "Design of a Sequential Axial Turbocharger for Automotive Application." Energies 12, no. 23 (November 21, 2019): 4433. http://dx.doi.org/10.3390/en12234433.

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In the last few years, the perspective of climate change, energy, competitiveness, and fuel consumption in the transportation sector has become one of the most significant public policy issues of our time. As different methods are being adapted into light-duty vehicles like engine downsizing, on the other hand, the increase in carbon emissions of heavy-duty trucks is becoming a major concern. Although previous researches have studied the methodology for selecting optimized turbocharger performance, still further investigation is needed to create a method for achieving the highest performance for a sequential axial turbocharger. Therefore, in this study, the design of a two-stage turbocharger system that consists of a radial turbine connected in series to an axial turbine is considered. The specific two-stage turbine was designed specifically and will be tested on a MAN 6.9 L diesel truck engine. With the engine already equipped with a radial type turbine, the newly designed two-stage turbine will be adapted to the engine to give more efficiency and power to it. Firstly, the modelling and simulation of the engine were done in Gt-Power, to achieve the same power and torque curves presented in the MAN engine specification sheet. Once that was achieved, the second task was to design and optimise a radial and axial turbine, which will form part of a two-stage system, through Computational Fluid Dynamics (CFD) analysis. Necessary data were gathered from the engine’s output conditions, for the ability to design the new turbo system. Lastly, the new turbine data were entered into the new two-stage turbo GT-Power model, and a comparison of the results was made. The CFD analysis, executed in ANSYS, for the radial turbine gave an 83.4% efficiency at 85,000 rpm, and for the axial turbine, the efficiency achieved was 81.74% at 78,500 rpm.

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Němec, Martin, Tomáš Jelínek, and Petr Milčák. "Clocking of stators in one and half stage of axial steam turbine." EPJ Web of Conferences 180 (2018): 02071. http://dx.doi.org/10.1051/epjconf/201818002071.

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An investigation of one and half axial turbine stage configuration was carried out in a closed-loop wind tunnel. The investigation was addressed to that impact how the previous stage outlet flow field influences the flow structures in the next stator in steam multistage turbines. The stage - stator interaction has been studied in this work. The detailed measurement with a pneumatic probes and fast response pressure probes behind the rotor and the second stator were performed to gain the useful data to analyze the impact. The detailed flow field measurement was carried out in the nominal stage regime (given by the stage isentropic Mach number 0.3 and velocity ratio u/c 0.68). The clocking effect of the stators is discussed and detailed unsteady flow analysis is shown.

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Rodgers, C., and R. Geiser. "Performance of a High-Efficiency Radial/Axial Turbine." Journal of Turbomachinery 109, no. 2 (April 1, 1987): 151–54. http://dx.doi.org/10.1115/1.3262077.

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This paper presents the test performance of a lightly loaded, combination radial/axial turbine for a 420-hp, two-shaft gas turbine. This two-stage turbine configuration, which included an interstage duct and an exhaust duct discharging vertically to ambient pressure conditions, was shown to be capable of attaining an overall isentropic efficiency of 89.7 percent. The influence of exhaust diffuser struts on the turbine performance under stalled power turbine conditions was shown to significantly affect compressor and turbine matching.

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Liu, Yu Jen, Yen Chang Chen, Pei Hsiu Lan, and Tsang Pin Chang. "Power Quality Measurements of a Horizontal Axial Small Wind Turbine." Applied Mechanics and Materials 870 (September 2017): 329–34. http://dx.doi.org/10.4028/www.scientific.net/amm.870.329.

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As small wind turbines are increasingly used, the assessments of power quality may thus become paramount. Unlike the large-scale wind turbines which are optional required to perform power quality measurements during production certification stage; however the power quality measurements are often neglected in small wind turbines since they are not requested on the certain of national grid codes at low-voltage distribution system level. Considering the high penetrations of small wind turbines may be connected to the future urban electric network, the paper performs the power quality on-site measurements of a horizontal axle small wind turbines. The issues may include the discussion of measurement system structure, the description of measurement method, and the analysis of wind turbine power characteristic, voltage/current trends, harmonics and flicker phenomena. The measured data collected in the study will valuable for the further analysis of power systems connected with the small wind turbines.

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Gaetani, Paolo, and Giacomo Persico. "Hot Streak Evolution in an Axial HP Turbine Stage." International Journal of Turbomachinery, Propulsion and Power 2, no. 2 (April 27, 2017): 6. http://dx.doi.org/10.3390/ijtpp2020006.

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Straka, Petr, Jaroslav Pelant, Martin Němec, Tomáš Jelínek, and Petr Milčák. "Investigation of flow in axial stage of experimental turbine." EPJ Web of Conferences 143 (2017): 02117. http://dx.doi.org/10.1051/epjconf/201714302117.

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Ghenaiet, Adel, and Kaddour Touil. "Characterization of component interactions in two-stage axial turbine." Chinese Journal of Aeronautics 29, no. 4 (August 2016): 893–913. http://dx.doi.org/10.1016/j.cja.2016.06.007.

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Talluri, Lorenzo, and Giacomo Lombardi. "Simulation and Design Tool for ORC Axial Turbine Stage." Energy Procedia 129 (September 2017): 277–84. http://dx.doi.org/10.1016/j.egypro.2017.09.154.

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Porreca, Luca, Anestis I. Kalfas, Reza S. Abhari, Yong Il Yun, and Seung Jin Song. "Stereoscopic PIV measurements in a two-stage axial turbine." E3S Web of Conferences 345 (2022): 01013. http://dx.doi.org/10.1051/e3sconf/202234501013.

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In the present work, the three-dimensional flow field in the interstage region of a twostage axial turbine has been measured by a stereoscopic PIV system. The stereoscopic method is used to compensate for perspective as well as to observe the highly threedimensional flows. The digital images are recorded with a set of two cameras positioned perpendicularly to the measurement plane and inclined by an angle varying between 22° and 30° to allow stereoscopic measurements. The laser beam is delivered to a laser endoscope able to access the measurement areas. By traversing radially, several blade-to-blade planes can be illuminated with the laser endoscope from 66 to 96% blade span. To compensate for the perspective distortion of the field of view due to the tilt angle of camera B as well as the optical distortion through the double-curvature windows, a threedimensional calibration method is used. In the current investigation, a Monte Carlo simulation has been conducted to evaluate measurement errors of PIV. Results of these measurements are compared with velocities derived from time resolved pressure measurements using fast aerodynamic response probe (FRAP). A good agreement is found at the exit of the second rotor. The present work present a unique set of steady and unsteady data measured in a two-stage axial turbine. Measured data in a volume can be used for numerical tool validation as well as improve existing kinematic model of vortex transport and dissipation.

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Abbasi, Sarallah, and Afshin Gholamalipour. "Parametric study of injection from the casing in an axial turbine." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 234, no. 5 (September 27, 2019): 582–93. http://dx.doi.org/10.1177/0957650919877276.

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Tip leakage flow reduces both efficiency and performance of axial turbines and damages turbine blades as well. Therefore, it is of great importance to identify and control tip leakage flow. This study investigated the effect of flow injection (from the casing), alongside flow structure, on turbine performance. Additionally, the effect of different injection parameters, including injection mass flow rate, angle, location, and diameter on the turbine performance are evaluated. A numerical analysis of the flow in a two-stage axial turbine was employed by using CFX software. To ensure the accuracy of the results, turbine performance curves were compared with the experimental results, which are in good agreement. Analyses revealed that active control method reduces tip leakage flow, improves turbine performance, and increases the efficiency by 1% to 5% as well. A parametric investigation of the tip injection has sought to identify how various parameters affect the turbine performance. The cross-section diameter and the angle of injection had no significant increase on efficiency. Additionally, results showed that at a point 9 mm further from the leading edge, the injection degree of effectiveness is optimum. Finally, analysis of the flow structure in the tip clearance region supported the tip leakage flow reduction.

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Feng, Zi-Ming, Chenhao Guo, Bingkun Wei, Wei Cui, Huibin Gu, and Jindong Zhang. "Axial-Swept Influence on Inner Flow Performance of HP Steam Turbine Based on CFD." Mathematical Problems in Engineering 2019 (July 25, 2019): 1–13. http://dx.doi.org/10.1155/2019/5363496.

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Swept blade technology was used to redesign the supercritical steam turbine sets that could improve the inner-efficiency of turbine sets and decrease the consumption of coal the noxious gas such as NOx. The eighth high-pressure stages, including static and rotor cascades, were selected as tested prototypes that were blew in the low-velocity wind tunnel. We used the five-hole ball head needle to measure the aerodynamic parameters distribution along the width and span direction of the high-pressure stage cascades. With the inkblot display technology, the limit flow spectrums were displaced in the blade surface and the endwalls. These tested data could be used to check the simulation results of CFD software. To improve the efficiency of the steam turbine high-pressure (HP) stage, we selected the supercritical steam turbine HP stage cascade blade as the prototype to research into its inner flow performance of the axial-swept blade by the CFD software. Two different redesigned blades, with ±20°, swept angle, and 30% swept height, named axial fore-swept and axial aft-swept, were built up. The stage passages flow field of the prototype blade, and the two redesigned swept blades were simulated using CFD software with stage interface planes between the stages. The CFD simulation results indicated that the leading edge of swept blades influenced the inlet flow field; the pressure in aft-swept blade stage in both endwalls was higher than in the middle and was beneficial to improve the passage flow properties of HP stage. But for the fore-swept HP stage, its pressure distribution was lower in both endwalls than in the middle and not beneficial to passage flow.

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Touil, Kaddour, and Adel Ghenaiet. "Flow unsteadiness and rotor-stator interaction in a two-stage axial turbine." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 235, no. 6 (February 4, 2021): 1370–93. http://dx.doi.org/10.1177/0957650920961625.

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This paper presents an in-depth investigation of the unsteady flows through two-stage high-pressure (hp) axial turbine with analyses of the rotor-stator interaction effects on the aerothermodynamic performance. The unsteady flow structures are characterized by the formation and convection of the tip leakage vortex and the hub corner vortices from the first stage blade-row through the second stage nozzle guide vanes (NGV) and blade-row. The modal decomposition of the circumferential distributions of static pressure depicts the modulation of the potential effect in the form of lobed structure propagating in both sides. Moreover, the blade pressure field shows that the first blade-row is exposed to a periodic overpressure induced by the first NGV while in the second blade-row the linear combination of both potential effects is dominant and results in a complex unsteady blade loading. FFT analyses of unsteady turbine performance for two-stage and part stages reveal that the total-to-total isentropic efficiency, torque-based efficiency and pressure ratio of the first stage depend strongly on the first blade-row passing frequency (BPF), whereas the total-to-total isentropic efficiency in second stage and two-stage turbine is related to the second blade-row BPF while the pressure ratio and the torque-based efficiency depend on the two rotors BPFs. Finally, the torque oscillations are mainly associated with the combination of frequencies of first stage NGV with that of second stage NGV. Furthermore, the obtained results show that Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are essential in analyzing the complex wakes and vortical structures through the two-stage turbine components and may produce better estimation of the performance.

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Syverud, Elisabet, Olaf Brekke, and Lars E. Bakken. "Axial Compressor Deterioration Caused by Saltwater Ingestion." Journal of Turbomachinery 129, no. 1 (January 1, 2007): 119–26. http://dx.doi.org/10.1115/1.2219763.

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Gas turbine performance deterioration can be a major economic factor. An example is within offshore installations where a degradation of gas turbine performance can mean a reduction of oil and gas production. This paper describes the test results from a series of accelerated deterioration tests on a General Electric J85-13 jet engine. The axial compressor was deteriorated by spraying atomized droplets of saltwater into the engine intake. The paper presents the overall engine performance deterioration as well as deteriorated stage characteristics. The results of laboratory analysis of the salt deposits are presented, providing insight into the increased surface roughness and the deposit thickness and distribution. The test data show good agreement with published stage characteristics and give valuable information regarding stage-by-stage performance deterioration.

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31

Camci, Cengiz, Debashis Dey, and Levent Kavurmacioglu. "Aerodynamics of Tip Leakage Flows Near Partial Squealer Rims in an Axial Flow Turbine Stage." Journal of Turbomachinery 127, no. 1 (January 1, 2005): 14–24. http://dx.doi.org/10.1115/1.1791279.

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This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the “Axial Flow Turbine Research Facility” (AFTRF) of the Pennsylvania State University. The streamwise length of these “partial squealer tips” and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new “channel arrangement” diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of “partial squealer rims” in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers are aerodynamically superior to the pressure side squealers and the channel arrangement. The suction side partial squealers are capable of reducing the stage exit total pressure defect associated with the tip leakage flow to a significant degree.

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32

Schobeiri, T. "Thermo-Fluid Dynamic Design Study of Single and Double-Inflow Radial and Single-Stage Axial Steam Turbines for Open-Cycle Thermal Energy Conversion Net Power-Producing Experiment Facility in Hawaii." Journal of Energy Resources Technology 112, no. 1 (March 1, 1990): 41–50. http://dx.doi.org/10.1115/1.2905711.

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The results of the study of the optimum thermo-fluid dynamic design concept are presented for turbine units operating within the open-cycle ocean thermal energy conversion (OC-OTEC) systems. The concept is applied to the first OC-OTEC net power producing experiment (NPPE) facility to be installed at Hawaii’s Natural Energy Laboratory. Detailed efficiency and performance calculations were performed for the radial turbine design concept with single and double-inflow arrangements. To complete the study, the calculation results for a single-stage axial steam turbine design are also presented. In contrast to the axial flow design with a relatively low unit efficiency, higher efficiency was achieved for single-inflow turbines. Highest efficiency was calculated for a double-inflow radial design, which opens new perspectives for energy generation from OC-OTEC systems.

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33

Bohn, Dieter, Sabine Ausmeier, and Jing Ren. "Investigation of the Optimum Clocking Position in a Two-Stage Axial Turbine." International Journal of Rotating Machinery 2005, no. 3 (2005): 202–10. http://dx.doi.org/10.1155/ijrm.2005.202.

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A frozen rotor approach in a steady calculation and a sliding mesh approach in an unsteady simulation are performed in a stator clocking investigation. The clocking is executed on the second stator in a two-stage axial turbine over several circumferential positions. Flow field distributions as well as the estimated performances from two approaches are compared with each other. The optimum clocking positions are predicted based on the estimated efficiency from the two approaches. The consistence of the optimum clocking positions is discussed in the paper. The availability and the limit of the frozen rotor approach in predicting the optimum clocking position is analyzed. It is concluded that the frozen rotor approach is available to search the optimum clocking position in the preliminary design period, although it misses some features of the unsteady flow field in the multistage turbines.

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34

Song, Bum Ho, and Seung Jin Song. "Lateral Forces From Single Gland Rotor Labyrinth Seals in Turbines." Journal of Engineering for Gas Turbines and Power 126, no. 3 (July 1, 2004): 626–34. http://dx.doi.org/10.1115/1.1690771.

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Even though interest in labyrinth seal flows has increased recently, an analytical model capable of predicting turbine flow response to labyrinth seals is still lacking. Therefore, this paper presents a new model to predict flow response in an axial turbine stage with a shrouded rotor. A concentric model is first developed, and this model is used to develop an eccentric model. Basic conservation laws are used in each model, and a nonaxisymmetric sealing gap is prescribed for the eccentric model. Thus, the two models can predict the evolution of a uniform upstream flow into a nonuniform downstream flow. In turbines with concentric shrouded rotors, the seal flow is retarded in the axial direction and tangentially underturned. In turbines with eccentric shrouded rotors, flow azimuthally migrates away from and pressure reaches its peak near the maximum sealing gap region. Finally, the rotordynamic implications of such flow nonuniformities are discussed and compared against eccentric unshrouded turbine predictions.

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35

Jo¨cker, Markus, Francois X. Hillion, Torsten H. Fransson, and Ulf Wa˚hle´n. "Numerical Unsteady Flow Analysis of a Turbine Stage With Extremely Large Blade Loads." Journal of Turbomachinery 124, no. 3 (July 1, 2002): 429–38. http://dx.doi.org/10.1115/1.1458023.

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This paper presents the detailed numerical analysis including parametric studies on the aerodynamic excitation mechanisms in a turbine stage due to the unsteady stator-rotor interaction. The work is part of the predesign study of a high-pressure subsonic turbine for a rocket engine turbopump. The pressure level in such turbines can be remarkably high (in this case 54 MPa inlet total pressure). Hence, large unsteady rotor blade loads can be expected, which impose difficult design requirements. The parameter studies are performed at midspan with the numerical flow solver UNSFLO, a 2-D/Q3-D unsteady hybrid Euler/Navier-Stokes solver. Comparisons to 2-D and steady 3-D results obtained with a fully viscous solver, VOLSOL, are made. The investigated design parameters are the axial gap (∼8–29 percent of rotor axial chord length) and the stator vane size and count (stator-rotor pitch ratio ∼1–2.75). For the nominal case the numerical solution is analyzed regarding the contributions of potential and vortical flow disturbances at the rotor inlet using rotor gust computations. It was found that gust calculations were not capable to capture the complexity of the detected excitation mechanisms, but the possibility to reduce excitations by enforcing cancellation of the vortical and potential effects has been elaborated. The potential excitation mechanism in the present turbine stage is found dominant compared to relatively small and local wake excitation effects. The parameter studies indicate design recommendations for the axial gap and the stator size regarding the unsteady rotor load.

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36

Schädler, Rainer, Anestis I. Kalfas, Reza S. Abhari, Gregor Schmid, Tilmann auf dem Kampe, and Sanjay B. Prabhu. "Novel high-pressure turbine purge control features for increased stage efficiency." Journal of the Global Power and Propulsion Society 1 (July 21, 2017): 68MK5V. http://dx.doi.org/10.22261/68mk5v.

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AbstractRim seals throttle flow and have shown to impact the aerodynamic performance of gas turbines. The results of an experimental investigation of a rim seal exit geometry variation and its impact on the high-pressure turbine flow field are presented. A one-and-a-half stage, unshrouded and highly loaded axial turbine configuration with 3-dimensionally shaped blades and non-axisymmetric end wall contouring has been tested in an axial turbine facility. The exit of the rotor upstream rim seal was equipped with novel geometrical features which are termed as purge control features (PCFs) and a baseline rim seal geometry for comparison. The time-averaged and unsteady aerodynamic effects at rotor inlet and exit have been measured with pneumatic probes and the fast-response aerodynamic probe (FRAP) for three rim seal purge flow injection rates. Measurements at rotor inlet and exit reveal the impact of the geometrical features on the rim seal exit and main annulus flow field, highlighting regions of reduced aerodynamic losses induced by the modified rim seal design. Measurements at the rotor exit with the PCFs installed show a benefit in the total-to-total stage efficiency up to 0.4% for nominal and high rim seal purge flow rates. The work shows the potential to improve the aerodynamic efficiency by means of a well-designed rim seal exit geometry without losing the potential to block hot gas ingestion from the main annulus.

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37

Dunn, Michael G. "Convective Heat Transfer and Aerodynamics in Axial Flow Turbines." Journal of Turbomachinery 123, no. 4 (February 1, 2001): 637–86. http://dx.doi.org/10.1115/1.1397776.

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The primary focus of this paper is convective heat transfer in axial flow turbines. Research activity involving heat transfer generally separates into two related areas: predictions and measurements. The problems associated with predicting heat transfer are coupled with turbine aerodynamics because proper prediction of vane and blade surface-pressure distribution is essential for predicting the corresponding heat transfer distribution. The experimental community has advanced to the point where time-averaged and time-resolved three-dimensional heat transfer data for the vanes and blades are obtained routinely by those operating full-stage rotating turbines. However, there are relatively few CFD codes capable of generating three-dimensional predictions of the heat transfer distribution, and where these codes have been applied the results suggest that additional work is required. This paper outlines the progression of work done by the heat transfer community over the last several decades as both the measurements and the predictions have improved to current levels. To frame the problem properly, the paper reviews the influence of turbine aerodynamics on heat transfer predictions. This includes a discussion of time-resolved surface-pressure measurements with predictions and the data involved in forcing function measurements. The ability of existing two-dimensional and three-dimensional Navier–Stokes codes to predict the proper trends of the time-averaged and unsteady pressure field for full-stage rotating turbines is demonstrated. Most of the codes do a reasonably good job of predicting the surface-pressure data at vane and blade midspan, but not as well near the hub or the tip region for the blade. In addition, the ability of the codes to predict surface-pressure distribution is significantly better than the corresponding heat transfer distributions. Heat transfer codes are validated against measurements of one type or another. Sometimes the measurements are performed using full rotating rigs, and other times a much simpler geometry is used. In either case, it is important to review the measurement techniques currently used. Heat transfer predictions for engine turbines are very difficult because the boundary conditions are not well known. The conditions at the exit of the combustor are generally not well known and a section of this paper discusses that problem. The majority of the discussion is devoted to external heat transfer with and without cooling, turbulence effects, and internal cooling. As the design community increases the thrust-to-weight ratio and the turbine inlet temperature, there remain many turbine-related heat transfer issues. Included are film cooling modeling, definition of combustor exit conditions, understanding of blade tip distress, definition of hot streak migration, component fatigue, loss mechanisms in the low turbine, and many others. Several suggestions are given herein for research and development areas for which there is potentially high payoff to the industry with relatively small risk.

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38

Kumar, Vikas, Keshar Patel, and Vikram P. Rathod. "Blade Stresses and CFD Analysis of Axial Gas Turbine." Applied Mechanics and Materials 592-594 (July 2014): 1011–14. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.1011.

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This work deals with study, investigation, design and analysis structure of 5 stages axial flow gas turbine with AxSTREAM software suite. AxSTREAM turbomachinery suite, with few boundary conditions generating solutions precisely and very fast in preliminary design with ideal point. For that point including losses design the streamline flow path and converging results of CFD analysis and visualization the thermodynamic parameters. Stress and FEM analysis of a single stage and study of von mises stresses distribution. Static and vibration analysis of turbine blade with difference frequency and temperature. Natural frequency, rotor speed study with operating speed and vibration mode with Campbell diagram.

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39

Amin Mobarak, Mostafa Shawky Abdel Moez, and Shady Ali. "Quasi Three-Dimensional Design for a Novel Turbo-Vapor Compressor and the Last Stage of a Low-Pressure Steam Turbine." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 85, no. 2 (August 5, 2021): 1–13. http://dx.doi.org/10.37934/arfmts.85.2.113.

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Turbo-vapor compressors (TVCs) are used to create a vacuum pressure in the evaporator of a novel combined cycle for electricity and freshwater production invented by Amin Mobarak. A novel design conceived of a TVC is introduced to increase the efficiency, allowable mass flow rate and reduce costs and losses. The system consists of a single axial compressor rotor followed by a single axial turbine rotor, which drives the upstream compressor, allowing high flow rates. A quasi-3D design is carried out for the TVC to calculate the flow velocity components and angles and ensure that the turbo-vapor turbine work is equal to the turbo-vapor compressor work. A preliminary design of the low-pressure power turbine (LPT) is done to examine the size and number of stages. The (LPT) size is twice the size of TVC at typical cycle operating conditions. A three-stage design is the most appropriate choice for the number of stages. It satisfies the accelerating relative flow condition at the last stage over a range of flow coefficients. A quasi-3D design is carried out for the LPT's last stage to ensure a multi-stage power turbine's safe design.

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40

Кондратьева, Екатерина, Ekaterina Kondrateva, Сергей Олейников, Sergey Oleynikov, Виктор Рассохин, Viktor Rassokhin, Алексей Кондратьев, Aleksey Kondratev, Александр Осипов, and Aleksandr Osipov. "STEAM TURBINE DEVELOPMENT FOR SUPERCRITICAL STEAM PARAMETERS." Bulletin of Bryansk state technical university 2017, no. 1 (March 31, 2017): 72–82. http://dx.doi.org/10.12737/24895.

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The paper reports the expediency and substantiation of the necessity for the gradual transition to power units on supercritical stream parameters in world power engineering. Basic stages in the development of steam turbine manufacturing with supercritical steam parameters are considered. The parameter increase at the input makes a profound impact upon the design of a flowing part of turbines. To operate a great difference in enthalpies in a cylinder without changing stages number one has to modernize them and sometimes to change the design completely. In the paper there is considered the expediency of the application of axial highloaded stages developed by the Polytechnics of Leningrad (LPI). There are also described the stages of designing steam turbine plants with critical and supercritical steam parameters at the input in a turbine. As an example there is analyzed SKR-100-300 steam turbine with the initial steam parameters of 29.4MPa and 650S. The results of solution computations directed to the efficiency increase of a regulatory stage of K-300-240 steam turbine with supercritical parameters of 580C and 29.0 MPa are presented. The application as a profile of an impeller the blade design of LPI allows increasing turbine plant efficiency in a wide range of mode parameters and also reducing a general number of turbine stages.

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41

Behr, T., L. Porreca, T. Mokulys, A. I. Kalfas, and R. S. Abhari. "Multistage Aspects and Unsteady Effects of Stator and Rotor Clocking in an Axial Turbine With Low Aspect Ratio Blading." Journal of Turbomachinery 128, no. 1 (June 28, 2005): 11–22. http://dx.doi.org/10.1115/1.2101855.

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This paper presents the outcome of a recent study in clocking-related flow features and multistage effects occurring in high-pressure turbine blade geometries. The current investigation deals with an experimentally based systematic analysis of the effects of both stator-stator and rotor-rotor clocking. Due to the low aspect ratio of the turbine geometry, the flow field is strongly three-dimensional and is dominated by secondary flow structures. The investigation aims to identify the flow interactions involved and the associated effects on performance improvement or degradation. Consequently a three-dimensional numerical analysis has been undertaken to provide the numerical background to the test case considered. The experimental studies were performed in a two-stage axial research turbine facility. The turbine provides a realistic multi-stage environment, in which both stator blade rows and the two rotors can be clocked relative to each other. All blade rows have the same blade number count, which tends to amplify clocking effects. Unsteady and steady measurements were obtained in the second stage using fast response aerodynamic probes and miniature pneumatic five-hole probes. The current comprehensive investigation has shown that multistage and unsteady flow effects of stator and rotor clocking in low aspect ratio turbines are combined in a nonlinear fashion caused by axial and radial redistribution of low energy fluid. The integral result of clocking on stage efficiency is compensated by competing loss generating mechanisms across the span.

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42

Nono Suprayetno, Priyono Sutikno, Nathanael P. Tandian, and Firman Hartono. "Numerical Simulation of Cascade Flow: Vortex Element Method for Inviscid Flow Analysis and Axial Turbine Blade Design." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 85, no. 2 (August 5, 2021): 14–23. http://dx.doi.org/10.37934/arfmts.85.2.1423.

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This study aims to design an axial turbine rotor blade and predict the turbine performance at preliminary design stage. Quasi three dimensional method was applied to design including blade to blade flow analysis. The blade profile uses a NACA 0015 airfoil by varying the profile thickness from hub to tip. The profile is divided into eleven segments which has different parameters. The profile was analysed using blade to blade flow/cascade flow analysis called vortex panel method to obtain lift coefficient. The analysis of cascade flow was performed in potential flow and prediction of turbine perfomance is carried out involving common best practice to give drag effect on the blade. The design of the turbine was applied on three different rotors, which also have a different discharge, head, and design rotation. The outer diameter of turbine 1 is 0.65 m, while turbine 2 and turbine 3 have an outer diameter of 0,60 m. The calculation result show that the efficiency of turbines 1, 2, and 3 were 88,32%, 89,67%, and 89,04%, respectively.

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43

Monteiro, Vinícius Guimarães, Edson Luiz Zaparoli, Cláudia Regina de Andrade, and Rosiane Cristina de Lima. "Numerical simulation of performance of an axial turbine first stage." Journal of Aerospace Technology and Management 4, no. 2 (2012): 175–84. http://dx.doi.org/10.5028/jatm.2012.04025411.

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44

Straka, Petr. "Numerical simulation of high-swirl flow in axial turbine stage." EPJ Web of Conferences 114 (2016): 02115. http://dx.doi.org/10.1051/epjconf/201611402115.

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45

Gallus, H. E., J. Zeschky, and C. Hah. "Endwall and Unsteady Flow Phenomena in an Axial Turbine Stage." Journal of Turbomachinery 117, no. 4 (October 1, 1995): 562–70. http://dx.doi.org/10.1115/1.2836568.

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Detailed experimental and numerical studies have been performed in a subsonic, axial-flow turbine stage to investigate the secondary flow field, the aerodynamic loss generation, and the spanwise mixing under a stage environment. The experimental study includes measurements of the static pressure distribution on the rotor blade surface and the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The rotor exit flow field was measured with an unsteady hot-wire probe, which has high temporal and spatial resolution. Both steady and unsteady numerical analyses were performed with a three-dimensional Navier–Stokes code for the multiple blade rows. Special attention was focused on how well the steady multiple-blade-row calculation predicts the rotor exit flow field and how much the blade interaction affects the radial distribution of flow properties at the stage exit. Detailed comparisons between the measurement and the steady calculation indicate that the steady multiple-blade-row calculation predicts the overall time-averaged flow field very well. However, the steady calculation does not predict the secondary flow at the stage exit accurately. The current study indicates that the passage vortex near the hub of the rotor is transported toward the midspan due to the blade interaction effects. Also, the structure of the secondary flow field at the exit of the rotor is significantly modified by the unsteady effects. The time-averaged secondary flow field and the radial distribution of the flow properties, which are used for the design of the following stage, can be predicted more accurately with the unsteady flow calculation.

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46

Straka, Petr, Martin Němec, and Thomáš Jelínek. "Investigation of flow in axial turbine stage without shroud-seal." EPJ Web of Conferences 92 (2015): 02088. http://dx.doi.org/10.1051/epjconf/20159202088.

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47

Green, T., and A. B. Turner. "Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage." Journal of Turbomachinery 116, no. 2 (April 1, 1994): 327–32. http://dx.doi.org/10.1115/1.2928368.

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The upstream wheelspace of an axial air turbine stage complete with nozzle guide vanes (NGVs) and rotor blades (430 mm mean diameter) has been tested with the objective of examining the combined effect of NGVs and rotor blades on the level of mainstream ingestion for different seal flow rates. A simple axial clearance seal was used with the rotor spun up to 6650 rpm by drawing air through it from atmospheric pressure with a large centrifugal compressor. The effect of rotational speed was examined for several constant mainstream flow rates by controlling the rotor speed with an air brake. The circumferential variation in hub static pressure was measured at the trailing edge of the NGVs upstream of the seal gap and was found to affect ingestion significantly. The hub static pressure distribution on the rotor blade leading edges was rotor speed dependent and could not be measured in the experiments. The Denton three-dimensional C.F.D. computer code was used to predict the smoothed time-dependent pressure field for the rotor together with the pressure distribution downstream of the NGVs. The level and distribution of mainstream ingestion, and thus the seal effectiveness, was determined from nitrous oxide gas concentration measurements and related to static pressure measurements made throughout the wheelspace. With the axial clearance rim seal close to the rotor the presence of the blades had a complex effect. Rotor blades in connection with NGVs were found to reduce mainstream ingestion seal flow rates significantly, but a small level of ingestion existed even for very high levels of seal flow rate.

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48

Straka, Petr. "Numerical Investigation of the Hub-Seal Mass Flow Rate Effect on the Axial Turbine Stage Efficiency." EPJ Web of Conferences 213 (2019): 02080. http://dx.doi.org/10.1051/epjconf/201921302080.

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The contribution deals with numerical simulation of compressible flow through the axial turbine stage equipped with the hub-seal. The current flowing from the hub-seal has a major impact on the secondary flow in the hub-region of the blade span. The aim of this work is to found a dependency of the efficiency-drop on the hub-seal mass flow rate. Numerical simulation has been made for configuration of experimental axial single-stage reaction turbine.

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49

Dambach, R., H. P. Hodson, and I. Huntsman. "1998 Turbomachinery Committee Best Paper Award: An Experimental Study of Tip Clearance Flow in a Radial Inflow Turbine." Journal of Turbomachinery 121, no. 4 (October 1, 1999): 644–50. http://dx.doi.org/10.1115/1.2836716.

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This paper describes an experimental investigation of tip clearance flow in a radial inflow turbine. Flow visualization and static pressure measurements were performed. These were combined with hot-wire traverses into the tip gap. The experimental data indicate that the tip clearance flow in a radial turbine can be divided into three regions. The first region is located at the rotor inlet, where the influence of relative casing motion dominates the flow over the tip. The second region is located toward midchord, where the effect of relative casing motion is weakened. Finally, a third region exists in the exducer, where the effect of relative casing motion becomes small and the leakage flow resembles the tip flow behavior in an axial turbine. Integration of the velocity profiles showed that there is little tip leakage in the first part of the rotor because of the effect of scraping. It was found that the bulk of tip leakage flow in a radial turbine passes through the exducer. The mass flow rate, measured at four chordwise positions, was compared with a standard axial turbine tip leakage model. The result revealed the need for a model suited to radial turbines. The hot-wire measurements also indicated a higher tip gap loss in the exducer of the radial turbine. This explains why the stage efficiency of a radial inflow turbine is more affected by increasing the radial clearance than by increasing the axial clearance.

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Yun, Yong Il, Il Young Park, and Seung Jin Song. "Performance Degradation due to Blade Surface Roughness in a Single-Stage Axial Turbine." Journal of Turbomachinery 127, no. 1 (January 1, 2005): 137–43. http://dx.doi.org/10.1115/1.1811097.

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Turbine blades experience significant surface degradation with service. Previous studies indicate that an order-of-magnitude or greater increase in roughness height is typical, and these elevated levels of surface roughness significantly influence turbine efficiency and heat transfer. This paper presents measurement and a mean-line analysis of turbine efficiency reduction due to blade surface roughness. Performance tests have been conducted in a low-speed, single-stage, axial flow turbine with roughened blades. Sheets of sandpaper with equivalent sandgrain roughnesses of 106 and 400 μm have been used to roughen the blades. The roughness heights correspond to foreign deposits on real turbine blades measured by Bons et al. [1]. In the transitionally rough regime (106 μm), normalized efficiency decreases by approximately 4% with either roughened stator or roughened rotor and by 8% with roughness on both the stator and rotor blades. In the fully rough regime (400 μm), normalized efficiency decreases by 2% with roughness on the pressure side and by 6% with roughness on the suction side. Also, the normalized efficiency decreases by 11% with roughness only on stator vanes, 8% with roughness only on rotor blades, and 19% with roughness on both the stator and rotor blades.

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Journal articles on the topic 'Axial turbine stage'

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