Predictions of the Flow in Repeating Stages of Axial Compressors Using Navier-Stokes Solvers

Abstract

In a well designed multi-stage axial flow compressor the flow quickly settles down to a repeating condition in which the flow angle and axial velocity profiles do not deteriorate further; they are more or less unchanged between entry to and exit from a deeply embedded stage.In early work, the flow in such repeating stages was studied using inviscid secondary flow analysis, coupled with empirical data on clearance flows, and also by inviscid numerical calculation. Underturning near the annulus walls was generally predicted but this was not convincingly confirmed by comparison with experimental data for repeating stage flows; it was apparent that viscous effects were important and should be taken into account.Further investigation of the flow in repeating stages has therefore been undertaken using Navier-Stokes solvers for comparison with early experimental results and improved test data more recently available. It is established that, with care, quite a good prediction of repeating stage flows can be made using steady-flow 3D viscous methods, and more general conclusions of greater validity can be drawn about over-or underturning at the annulus walls than the universal underturning predicted in the earlier inviscid approaches for moderately loaded stages.

A First-Principles Based Methodology for Design of Axial Compressor Configurations

“…In the 1990s with the significant developments in CFD, three-dimensional design and analysis of axial compressor configurations has been made possible. Bolger and Horlock 51 performed direct design analysis on a four-stage compressor and showed that the repeating stage phenomenon where the blockages increased across each row. By this time direct design concepts such as the use of bowed blades to control secondary loss in turbines and the use of sweep and bow to reduce corner separations in compressors were introduced.…”

Influence of inlet swirl on pattern factor and pressure loss in an aero engine combustor

“…Bolger et al 2 numerically investigated and experimentally verified the flow profiles including the swirl angles at each stage of a multi stage compressor of a gas turbine engine. The effect on combustor exit pattern factor with a centrifugal compressor exit swirl in a micro turbine combustor was investigated by Yong et al 3 They predicted an increase in pattern factor and pressure loss for 2 different combustor design configurations.…”

“…From the above literature review, it is clear that the compressor exit will always have some swirl [1][2][3][4] which cannot be neglected in analysing an actual combustor performance. The effect of various combustor design parameters such as fuel nozzle spray patterns, dilution hole geometry, fuel type, swirl number and different fuel injection methods on combustor exit pattern factor has been reported by authors.…”

Three-Dimensional Performance Prediction of Multistage Axial Flow Compressors With a Repeating Stage Model

“…In multistage axial flow compressors it is observed that the flow features repeat after several stages from the entry to the exit of the stage while the annular turbulent boundary layer get fully developed. This phenomenon was analysed numerically with Navier-Stokes solvers for two repeating stage compressors, Bolger and Horlock, 1995. The repeating nature of the flows within the multistage environments were well predicted by modelling closely the inlet and exit boundary conditions especially to simulate the measured static pressure fields.…”

“…The repeating nature of the flows within the multistage environments were well predicted by modelling closely the inlet and exit boundary conditions especially to simulate the measured static pressure fields. Several methods have been developed for multistage turbomachinery simulation and may be categorised as follows (Chima et al, 1998). The first one is the successive analysis of isolated blade rows where an analysis code for an isolated blade row is available.…”