Aerodynamic Performance Research On Ultra High Expansion Ratio Turbine

Ultra-high expansion ratio special turbines are of great researchingsignificance since they have relatively high expansion ratio to achieve largeenthalpy drops, small size and light weight. Due to the large expansion ratio of thistype of turbines, the internal flow field reaches supersonic flow, leading toextremely complex internal flow conditions.The paper conducted three-dimension structural design of an ultra-highexpansion ratio special turbine. The stator and rotor of the turbine are Laval nozzleand impulsive high-load blade, respectively, using partial-admission method.Numerical simulation method was adapted to reserch the internal air flow conditionof the turbine. The research focused on air flow characteristics of different nozzlesin the turbine, the circumferential inhomogeneity of air flow, the characteristics ofshock and loss distribution in rotor blade cascade, and the load distribution andcapacity for doing work of each blade.Analog modeling method was used to conduct static analog experiment ofsupersonic nozzle and high-load rotor blades. By measuring the static pressure ofthe wall of nozzle and surface of rotor blades under different operating conditions,the shock characteristics of in supersonic nozzle and rotor blade cascade wereanalyzed. And by comparing the results of numerical simulation with the results ofexperiment, the accuracy and the reliability of numerical simulation was examined.Variable operating characteristic investigation in the turbine was investigatedby theoretical analysis. By utilizing a calculation procedure for Off-designOperating Condition of high-pressure turbine stage and combination of three-dimensional numerical simulation, when total pressure of the inlet, static pressureof the outlet and rotational speed were altered, the variation law of turbine powerand efficiency was obtained.