A generic multistage compressor design for multiphase code and model benchmark

Authors

Silvio Geist - Helmut Schmidt University, Germany
Markus Schatz - Helmut Schmidt University, Germany

Abstract

In order to evaluate the impact of high-fogging on the behavior of the compressor in stationary gas turbines, multiphase flow fields consisting of a carrier gas, liquid droplets and vapor phase need to be considered. In CFD-simulations, the momentum transfer between droplets and the gas phase, mass and heat transfer through evaporation as well as interaction between the droplets and the blading, casing or hub must be accounted for in some way through modelling. As there is a multitude of models for each of these phenomena, it is difficult to assess computational results of effects such as erosion, impact of injection location or the change of stage characteristics with injection, especially because different compressor designs are used in these studies. Moreover, geometries of multistage compressors are most often confidential and not accessible for other researchers. Hence it is impossible to assess different modeling approaches. This publication provides a generic multistage compressor design for multiphase code and model benchmark and comparison. For this purpose, a ten-stage subsonic compressor including an IGV was designed using the open source turbomachinery design system MULTALL and was analyzed over a wide range of boundary conditions. Multiphase simulations with dry and humid air and using different sprays have been carried out using ANSYS CFX. These simulations included mass, momentum and heat transfer between the droplets and the carrier gas and splashing at all surfaces. The therefrom-deposited water is not yet further considered in the simulations since this would involve complex and computationally expensive film modelling. The results include compressor and efficiency maps, state variables and, where applicable, the amount of deposited water for all blade rows. The entire compressor geometry is available online together with the MULTALL data. Based on this generic compressor geometry, a comprehensive database of models available for the description of the complex multiphase flows in multistage compressors can be established, allowing to assess the performance of the various models used.