Improving the accuracy of tests for centrifugal compressor stage performance prediction

A design of experiment approach was used to solve problems on the new centrifugal compressor stage development test beds at the Nuovo Pignone - GE Oil&Gas premises in Florence, Italy. The company is able to provide centrifugal compressor equipment tailored to the user's requests, with special reference to the oil & gas market. In order to provide this service, an archive of designs is available which can be adapted to different requirements: CFD is widely used to improve the turbomachinery performance, and on each new stage design extensive fluid dynamics test campaigns are routinely run, in order to confirm the expected performance. Recently inadequacy of the accuracy of the measurements became evident: the cause was traced back to thermal effects which introduced a large uncertainty in the test results, with special reference to machines having large operating Mach number, and low pressure ratio. The present work included: a) The development of a heat transfer model capable of predicting the observed trend of the experimental data b) The improvement of the accuracy of total temperature measurements, needed to confirm the results of the model. The positive results allow the company to guarantee with increased confidence the expected performance levels.