Transport of entropy waves within a HP turbine stage

This paper presents the results of an experimental study on the transport of entropy waves, representative of those generated by gas turbine burners, within an un-cooled high-pressure gas turbine stage. The prescribed entropy waves were injected in streamwise direction featuring a 7% over-temperature with respect to the main flow at the stage inlet, with a frequency of 30 Hz. The entropy waves are injected in four different circumferential positions with respect to the stator blade. Detailed time-resolved temperature measurements as well as aerodynamic measurements upstream and downstream of the blade rows were performed. Measurements showed a relevant attenuation of the entropy waves throughout their transport within the stator blade row. The temperature distribution resulted in a severe alteration depending on the injection position. Downstream of the rotor, the waves spread over the pitch above midspan and are more concentrated at the hub. Finally, a comparison with measurements performed with conventional steady hot streaks is also reported, remarking both differences and affinities. As a relevant conclusion, it is experimentally shown that entropy waves can be proficiently simulated by considering a number of hot streaks of different amplitude.