Session: 32-08 Flow Control 1

Paper Number: 125712

125712 - Aerodynamic Performance of Partially Variable Geometry High-Pressure Turbine 

Variable geometry turbine (VGT) technology changes the throat width of flow path by adjusting the setting angle of turbine guide vane to control the mass flow rate of turbine and achieve the purpose of adjusting the engine operating condition. With the development of variable cycle engine, variable geometry high-pressure turbine becomes a key component of adaptive variable cycle engine to achieve large changes in mass flow rate. Therefore, the demand for variable geometry turbine technology is getting urgent. In order to overcome the technical difficulties of current variable geometry turbine technology, including large tip leakage and low adjustment accuracy at small mass flow rate changes, partially variable geometry turbine is considered as an alternative solution. In this paper, research for the aerodynamic performance of partially variable geometry turbine is conducted. Based on the original design of the General Electric Energy Efficient Engine（E³）high pressure turbine, this paper introduces a new structure with half vanes fixed and the other half adjustable, which are arranged at intervals. Numerical simulation and theoretical analysis are applied to investigate the effect of the adjustable guide vane on the flow fields, mass flow rate and efficiency of the high pressure turbine, to reveal the main factors affecting the aerodynamic performance.

The following conclusions are drawn from the study.

1) Comparing with the conventional variable geometry turbine, the partially variable geometry turbine can realize a larger rotating angle of the adjustable guide vane under the same flow regulation demand. Moreover, the flow path throat width of the stator and the opening degree of the adjustable blade have a linear relationship. The above two features guarantee the accuracy of the regulating mechanism.

2) The loss resulted from the angle of attack, the shock wave and the secondary flow is still the main component of the loss of partially variable geometry turbine. When the vane opening is getting larger, the loss of shock wave is decreasing, while the loss from the change of angle of attack increases. Under this condition, the secondary flow loss in two flow paths near the adjustable vane shows different trends: in the flow path whose throat width gets larger, the secondary flow loss increases, and in the other side, it decreases. Due to the factors mentioned above, the turbine efficiency remains unaffected when there is a little change in the mass flow rate. In addition, the turbine efficiency shows improvement under certain conditions of small pressure ratio, as compared to the original design.

3) When there are larger variations in mass flow rate, the efficiency of the turbine decreases due to deviation from the design value of the angle of attack. Specifically, the turbine efficiency decreases more when the guide vane is in a closed state rather than an open one.

4) Within the specified adjustment range for mass flow rate, there is no significant difference between the partially variable geometry turbine and the conventional variable geometry turbine in terms of aerodynamic performance and parameter uniformity at the outlet section of the guide vane. Additionally, the partially variable geometry turbine can also regulate the power distribution between the two turbine stages with the same effect as the conventional variable geometry turbine.

The above conclusions show that the partially variable geometry turbine analyzed in this paper can replace the conventional variable geometry turbine, which will provide a reference for the research of variable geometry turbine technology.

Presenting Author: Lyu You Institute for Aero Engine,Tsinghua University

Presenting Author Biography: 3rd year PhD student at Institute for Aero Engine, Tsinghua University.

Authors:

Lyu You Institute for Aero Engine,Tsinghua University
Xuezhi Dong Institute for Aero Engine, Tsinghua University
Xiyang Liu Institute for Aero Engine, Tsinghua University
Chunqing Tan Institute for Aero Engine, Tsinghua University