Scaling effect on transonic rotor aerodynamic performances and loss mechanisms

It is difficult to conduct the full-scale testing for J-class heavy-duty gas turbine transonic compressors (with an inlet design mass-flow rate of roughly 1000 kg/s), the diameter of the first stage compressor was nearly 3 m, the turbomachinery designers scaled-down the geometry to meet thepower limitation, which is a convenient method based on similarity principle. This work performed comparative investigations of scaling effects on the aerodynamic performance and loss mechanisms based on the numerical simulation. The results showed that the larger model operated at a higher isentropic efficiency condition. The Casey’s prediction models had a deviation of less than 0.5%. The shock/tip leakage vortex loss and shock-boundary layer interaction loss of the larger model were stronger than those in the prototype model, while the profile boundary loss and wake mixing loss of the prototype model were stronger than the larger model. The profile losses (boundary layer and wake mixing loss) were the main loss source causing the difference in the isentropic efficiency between the prototype and scaled-up compressor rotor, meanwhile, the difference caused by tip secondary flow loss was not the main source. This investigation is intended to provide suggestions for industrial preliminary design stages of the heavy-duty gas turbine compressors.