The turbine in an LH2/LOX rocket engine is designed as a two-stage supersonic partialadmission turbine. Three-dimensional steady and unsteady simulations were conducted to analyze turbine performance and aerodynamic f...The turbine in an LH2/LOX rocket engine is designed as a two-stage supersonic partialadmission turbine. Three-dimensional steady and unsteady simulations were conducted to analyze turbine performance and aerodynamic forces on rotor blades. Different configurations were employed to investigate the effects of the axial gap and nozzle distribution on the predicted performance and aerodynamic forces. Rotor blades experience unsteady aerodynamic forces because of the partial admission. Aerodynamic forces show periodicity in the admission region, and are close to zero after leaving the admission region. The unsteady forces in frequency domain indicate that components exist in a wide frequency region, and the admission passing frequency is dominant.Those multiples of the rotational frequency which are multiples of the nozzle number in a fulladmission turbine are notable components. Results show that the turbine efficiency decreases as the axial gap between nozzles and the 1 st stage rotor（rotor 1） increases. Fluctuation of the circumferential aerodynamic force on rotor 1 blades decreases with the axial gap increasing. The turbine efficiency decreases as the circumferential spacing between nozzles increases. Fluctuations of the circumferential and axial aerodynamic forces increase as the circumferential spacing increases. As for the non-equidistant nozzle distribution, it produces similar turbine performance and amplitudefrequency characteristics of forces to those of the normal configuration, when the mean spacing is equal to that of the normal case.展开更多
To obtain a high specific work output,the large pressure ratios across the turbine are required.This can be achieved using a supersonic turbine.When the fluid mass flow is low,the impulse kind of one or two stages sup...To obtain a high specific work output,the large pressure ratios across the turbine are required.This can be achieved using a supersonic turbine.When the fluid mass flow is low,the impulse kind of one or two stages supersonic turbine is employed.To prevent losses due to low blade aspect ratio and issues related to manufacturing and industrial problems,the turbine is used in partial admission conditions.Studies show that the turbine efficiency is highly dependent on the amount of partial admission coefficient.The turbine efficiency in full admission is high,but the use of partial admission lowers the additional losses.Therefore,there will be a degree of partial admission in which the turbine will have the highest efficiency.The aim of this work is to achieve the optimum partial admission for a special impulse turbine as a case study.Therefore,in the beginning,an appropriate model of losses is presented.Then,using a nonlinear design optimization code,the partial admission of an impulse supersonic turbine is optimized.This code is written using a genetic algorithm.Then,using three-dimensional numerical analysis,the optimal model will be selected.In the optimization problem,the turbine efficiency is the objective function.The amount of design parameters and constraints used in this process are ten and eight,respectively.After the optimization process,prototypes of designed and modified turbines are made and tested.Test results were compared and analyzed.The results showed that the turbine efficiency is improved between 2.5%and 3%depending on various operation conditions.展开更多
文摘The turbine in an LH2/LOX rocket engine is designed as a two-stage supersonic partialadmission turbine. Three-dimensional steady and unsteady simulations were conducted to analyze turbine performance and aerodynamic forces on rotor blades. Different configurations were employed to investigate the effects of the axial gap and nozzle distribution on the predicted performance and aerodynamic forces. Rotor blades experience unsteady aerodynamic forces because of the partial admission. Aerodynamic forces show periodicity in the admission region, and are close to zero after leaving the admission region. The unsteady forces in frequency domain indicate that components exist in a wide frequency region, and the admission passing frequency is dominant.Those multiples of the rotational frequency which are multiples of the nozzle number in a fulladmission turbine are notable components. Results show that the turbine efficiency decreases as the axial gap between nozzles and the 1 st stage rotor（rotor 1） increases. Fluctuation of the circumferential aerodynamic force on rotor 1 blades decreases with the axial gap increasing. The turbine efficiency decreases as the circumferential spacing between nozzles increases. Fluctuations of the circumferential and axial aerodynamic forces increase as the circumferential spacing increases. As for the non-equidistant nozzle distribution, it produces similar turbine performance and amplitudefrequency characteristics of forces to those of the normal configuration, when the mean spacing is equal to that of the normal case.
文摘To obtain a high specific work output,the large pressure ratios across the turbine are required.This can be achieved using a supersonic turbine.When the fluid mass flow is low,the impulse kind of one or two stages supersonic turbine is employed.To prevent losses due to low blade aspect ratio and issues related to manufacturing and industrial problems,the turbine is used in partial admission conditions.Studies show that the turbine efficiency is highly dependent on the amount of partial admission coefficient.The turbine efficiency in full admission is high,but the use of partial admission lowers the additional losses.Therefore,there will be a degree of partial admission in which the turbine will have the highest efficiency.The aim of this work is to achieve the optimum partial admission for a special impulse turbine as a case study.Therefore,in the beginning,an appropriate model of losses is presented.Then,using a nonlinear design optimization code,the partial admission of an impulse supersonic turbine is optimized.This code is written using a genetic algorithm.Then,using three-dimensional numerical analysis,the optimal model will be selected.In the optimization problem,the turbine efficiency is the objective function.The amount of design parameters and constraints used in this process are ten and eight,respectively.After the optimization process,prototypes of designed and modified turbines are made and tested.Test results were compared and analyzed.The results showed that the turbine efficiency is improved between 2.5%and 3%depending on various operation conditions.
