Blade-to-Blade Flow Effects on Mean Flow in Transonic Compressors

Abstract

This paper describes a method of introducing nonaxisymmetric effects into the axisymmetric flowfield computation for a highly-loaded compressor. The approach is centered around modeling of three important nonaxisymmetric phenomena that control the mean momentum and energy transfer processes. Apparent stresses are introduced into the mean flow momentum equations by pitchwise averaging. The concept of apparent entropy resulting from the production of fluctuation energy is introduced. An expression for mean rothalpy variation along the streamline is derived by pitchwise averaging of the energy equation. Mean-flow equations suitable for the streamline-curvature computational scheme are developed which include these three effects. An assessment of the importance of these effects and experimental verifications of the computational approach have been achieved by use of time resolved experimental measurements of the flow in the MIT Slowdown Compressor. The revised streamline-curvature procedure has been used to predict the axisymmetric (peripheral mean) flow. The agreement of predicted and measured rotor outlet tangential velocity is excellent. The results show that three-dimensional inviscid effects do not modify significantly the mean flow, and that the direct effect of apparent stresses on the mean flow is also small. The major deviations of the actual flow from the inviscid flow are due to the variations of mean rothalpy and the production of apparent entropy, both effects which are introduced in turbomachine aerodynamics for the first time here. Nomenclature F,F rv ,F Qv ,F zv = blade force, viscous body force components per unit mass in the r, 6, and z directions H, h = total enthalpy, static enthalpy / =rothalpy defined by I=h + w 2 /2-(r 2 Q 2 )/2 ( = direction of computation in the meridional plane m = meridional streamline direction P 0 ,P s ,P t = reference static, and total pressures q = total absolute velocity defined by # = t v,v',v w, w', z X p radial, radius of curvature direction entropy total temperature, static temperature time absolute velocity, fluctuation, time average relative velocity, fluctuation, time average axial coordinate mean relative flow angle defined by blade lean angle in ?-0 plane defined by tane=-r(d8/de) angle between the direction of computation (0 and the radial direction, ratio of specific heats blade thickness blockage factor density Presented as Paper 79-1515 at

Investigating Circumferential Non-Uniformities in Throughflow Calculations Using an Harmonic Reconstruction

“…equations (7) to (9). The numerical method is based on an explicit time-marching cell-centered finite-volume approach.…”