Experimental Determination of a Four Stage Axial Compressor Map Operating in Wet Compression

Abstract

Injecting water in the air upstream of an axial compressor intake is an effective method to increase the efficiency and the power output of a gas turbine application especially at hot days. Reasoned by their complex two phase flow axial compressors which operate in wet compression mode are in the focus of present thermodynamic analysis, numerical investigations and experimental research. Recently the evaporation process of water droplets, especially at high temperature and pressure levels has been investigated with the laser based measurement technique Phase Doppler Particle Analyzer (PDPA) in detail in a stationary test rig at the University of Duisburg-Essen. The focus of these investigations has been laid on the analysis of the evaporation process in a free stream or cross flow behavior without droplet wall interaction. In this paper the first results of the novel four stage axial compressor test rig are published. This test rig is arranged for high amount of water injection with special optical access for laser based measurements. The first part of the paper outlines the general design, geometric facts and aerodynamic reference parameters of the test rig and gives an introduction to the installed conventional measurement technique. Discrete measurement results from dry runs are compared with CFD results to validate the gathered experimental data. In the second part of the paper the previously discussed dry runs are compared with measurement results of runs with water injection. The amount of water to air ratio is varied and the effects on the operating behavior of the four stage axial compressor are pointed out in detail. Furthermore results from the laser based PDPA measurements at the inlet and at the outlet of the compressor outline the impact on the water droplets moving through the compressor in wet compression mode.

Aero engine compressor cooling by water injection - Part 1: Evaporative compressor model

“…These droplets usually begin to evaporate in the initial/front stages of the compressor that brings about the cooling of the air flow (drop in temperature), increased density and moisture content. This procedure has been studied extensively through compressor analytical methods [11][12][13][14], through-flow approach, CFD approach [8,[15][16][17][18], and experimental investigations [9,[19][20][21] that have mostly focused on stationary gas turbines. For the analytical methods, Kim et al [22] categorise the models into: natural convection model, diffusion model and Stokes model.…”