Numerical Research Of Aerodynamic And Aeroacoustic Performance Of A High Pressure Turbine Stage

As the increase of efficiency and thrust-weight ratio,the inlet temperature and pressure ratio of turbines arise constantly,and high pressure turbine(HPT)blades cooling becomes a key factor limiting its performance.Film cooling technology is widely used in gas turbines that protects the blades from the high temperature mainstream,and trailing egde blowing also affects downstream status.Stator-rotor interaction especially the interaction between the upstream wake and rotor is a kind of typical unsteady source in gas turbines flow,which has a great influence on aerodynamic performance,noise radiation and fatigue life of turbines.Trailing edge blowing affects areodynamic and aeroacoustic performance by changing the wake and interaction mentioned above.This paper firstly has used a cylinder and 3D cascades as the objects,and chosed SST model to complete the research while taking into account of accuracy and efficiency by comparing the result of k-ε,RNG k-ε,k-ω,SST,DES and LES model.The gridindependent verification has also carried out under this model.Secondly,unsteady calculations of the research objects have been carried out by using Fluent and CFX platform,and the noise radiation characteristics of these objects have been studied.It is found that the peak frequency in noise spectrum of the cylinder is consistent with the frequency of the Karman vortex shedding,while the stator-rotor interaction noise of HPT is mainly concentrated on the blade passing frequency(BPF)and its doubling.Injecting entropy waves at the inlet will affect the interaction and more obvious when using lower frequency waves.And the flow mechanism of noise is analyzed by using the vortex-sound equation.Then,the cooling structure of the stator has been simplified and modified,and series of symmetry and pressure side cutback slot trailing edge structures with 4 kinds of width have been designed.The influence of blowing on downstream under different trailing egde structures,blowing ratio and slot width has been studied by steady calculations.Results show that blowing ratio has more influence on downstream than edge structures and slot width,and the conclusion under different blowing ratio is different.There are four typical wakes when increasing blowing ratio from 0: pure wake(θ/d>0,BR=0.0%),weak wake(θ/d>0,BR≠0.0%),momentumless wake(θ/d≈0)and jet wake(θ/d<0).And in which process,the Cpt of the stator first increases then decreases and the peak shifts towards to the suction side,the β decreases,thus the layer thickness of the suction side increases,and the cooling effect at trailing edge bocomes worse.When the momentum loss thickness is 0,velocity loss of the wake is minimized and the wake has minimal impact on downstream.Finally,the effect of pure wake,momentumless wake and jet wake on flow and the noise performance have been studied by unsteady caclulations.Results prove that the momentumless trailing edge blowing can strengthen mixing between the wake and mainstream compared with the result of pure wake,it also weaken that interaction,minimize the scale of the interaction-vortex at the suction side.Moreover,the amplitude of pressure fluctuation on the surface of rotor blades and the dipole noise strength are reduced.In contrast,the flow condition deteriorates when reaching jet wake.From the result of acoustics,the sound pressure level(SPL)of momentumless wake is reduced by about 2.48 dB compared with pure wake,the SPL of jet wake is increased by about 0.96 dB.