Performance Measurement of the Second Stage of a Transonic Turbine

Abstract

In November 1999 the turbine test facility at the Institute for Thermal Turbomachinery and Machine Dynamics was completed. This test stand is a cold flow transonic test turbine facility, which is a unique combination of a 2.3 MW axial test turbine and a directly-coupled compressor that generates about the half of the compressed air needed to drive the turbine. To cover the losses, additional air is provided by an electrically-driven compressor station. A 600 kW suction blower driven by a helicopter gas turbine is used to decrease the exhaust pressure, thus increasing the expansion ratio up to 4.5 (see Erhard and Gehrer “Design and Construction of a Transonic Test-Turbine Facility”, ASME Paper 2000-GT-480). Since then, flow measurements with two different transonic turbine stages have been carried out. This paper will focus on the description of the measurement system, data analysis and the newest test results that have been obtained on a turbine stage developed by Nuovo Pignone. This stage has been configured to be representative of advanced designs for medium/small land based gas turbines and is characterized by high pressure ratios and strongly transonic effects. The characteristic feature of this stage is the convergent- divergent flow channel. Basic data of this turbine stage to obtain flow similarity are: 2.2 MW shaft power at 11500 rpm, pressure ratio 4.5, mass flow 22 kg/s. The paper will contain appropriately plotted results of dimensionless stage characteristic curves over a broad range of operation points.