Study On Heat Transfer In The High-pressure Turbine Rotor Blade Of A Vaneless Counter-rotating Turbine

The vaneless counter-rotating turbine(VCRT),having the potential to improve the thrust-to-weight ratio,will play an important role for future high-performance propulsion systems.Determined by the aerodynamic configuration,the reaction degree and the loading for the high-pressure turbine(HPT)of the VCRT,as well as the expansion degree of the flow in the HPT rotor,are usually so high that the exit relative Mach number of the HPT rotor can reach 1.3-1.5.The over-speeding of the flow in the HPT rotor and its associated shock wave structure must have important impact on the heat transfer in the HPT rotor.Aimed to investigate the heat transfer in the HPT rotor of the VCRT,the current study develops a double-sided thin-film heat flux gauge that is suitable for rotating measurement,and a high-speed rotating dynamic measurement system,as well as the associated thin-film gauge designing and rotating measurement approach.On the basis,high-speed rotating heat transfer measurements are implemented for a full-scale VCRT test hardware on the IET short-duration turbine test rig.Combing both the experimental and the CFD effort,the heat transfer in the HPT rotor of the VCRT under different inlet Reynolds numbers is addressed.The main work and conclusion of this study are as follows:1.The effects of the thin-film thickness on the performance of the thin-film heat flux gauge are systematically analyzed.The analysis reveals the increase in the thin-film thickness can improve signal-to-noise ratio,but result in higher uncertainty in high-frequency heat flux results.A dynamic calibration approach,established on the system identification,is further presented.The approach can effectively extract the influence of the increase in the thin-film thickness on the high-frequency heat flux results.2.A double-sided thin-film heat flux gauge is developed utilizing the magnetron sputtering,together with which,a complete solution covering the designing,the manufacturing and the calibration is formed.Meanwhile,a high-speed rotating dynamic measurement system is also constructed based on the digital telemetry.On the basis,an applicable approach is addressed for implementing the rotating measurement.The practice indicates the developed rotating measurement system is stable and qualified for application requirements.3.By the results of both the full-scale high-speed rotating heat transfer measurement and CFD simulation,the steady heat transfer in the HPT rotor of the VCRT is investigated.It is shown the flow on the suction side accelerates so fast that local acceleration parameter K can exceed 3×10-6,which is the criterion of"relaminarization".In this case the boundary layer remains laminar for most part of the suction side.As the laminar boundary layer gets increasingly thick,the heat transfer persists to fall from the leading edge of the suction side.Until at the aft portion,the shock wave emanating from the adjacent blade trailing edge impinges on the suction side,and causes the boundary layer to separate and transitioned to turbulence.This situation is the so-called "separation transition",as a result of which,the heat transfer increases dramatically.Meanwhile,it is also found the overall heat transfer across the suction side is augmented as the inlet Reynolds number rises.Especially for the portion after the "separation transition",the heat transfer enhancement effect is much more significant.4.By the data of the full-scale high-speed rotating heat transfer measurement,the unsteady heat transfer in the HPT rotor of the VCRT is explored.On the first half of the suction side,the heat transfer pulsates significantly as the upstream wake passes.As the wake goes downstream,the local turbulent region induced by the wake gets wider.Consequently,the overall heat transfer for the second half of the suction side is enhanced,while the pulsations are weakened.For the aft portion of the suction side,the heat transfer is not only influenced by the upstream wake but also the downstream rotor.Besides,it is found as the inlet Reynolds number increases,the pulsations for the heat transfer of the suction side decline.