Contributions to the study of turbomachinery aerodynamics: Part I. Design of a fish-tail diffuser test section. Part II. Computations of the effects of AVDR on transonic turbine cascades.

摘要

All gas turbine engines manufactured by Pratt and Whitney Canada today use fish-tail or pipe diffusers to guide and decelerate the flow from the exit of the centrifugal impeller to the inlet of the combustion chamber. Very little experimental analysis has been conducted on the flow through these diffusers. Part I of this thesis deals with the design and manufacture of a large scale fish-tail diffuser test section. The test section will be used for measuring the mean flow and turbulence quantities in the diffuser thus allowing a clearer understanding of the complex flow patterns present in such ducts.;There exists a lack of information in the literature regarding the effects of flow convergence and divergence on the performance of transonic turbine cascades. One measure of flow convergence and divergence is the axial velocity-density ratio (AVDR), or simply the axial velocity ratio (AVR) for incompressible flows. Rodger (1992) experimentally studied the effects of AVR on a cascade of turbine blades for low speed flow. Part II of this thesis deals with the computational investigation of the effects of AVDR on turbine blades operating at transonic conditions.;The computations were performed with a three-dimensional Navier-Stokes solver developed by Dawes (1988). An extensive survey of the code has been undertaken and a detailed description of the code is presented. The code was validated against Rodger's (1992) measurements, and although quantitative predictions were not very accurate the basic trends were predicted reasonably well.