Entropy Generation in Three-dimensional, Swirling Flows

Entropy generation in a transonic, highly loaded, axial turbine stage has been investigated via application of the entropy transport equation. The use of a RANS simulation required additional consideration of entropy transport associated with the time-averaging of products of fluctuating quantities. Analysis of the RANS entropy transport equation allowed the investigators to calculate the volumetric distribution of $\overline{D}\overline{s}/\overline{Dt}$; that is, the time rate of change of mean entropy of a material particle. The quantity $\overline{D}\overline{s}/\overline{Dt}$ revealed localized regions of entropy increases and decreases of material particles. It was discovered that regions of large +$\overline{D}\overline{s}/\overline{Dt}$ occur primarily on the blade suction surface. Additionally, it was found that the passage vortex core, typically associated with high entropy fluid, corresponded with regions of $\overline{D}\overline{s}/\overline{Dt}$ $\approx$ 0. This result suggests that entropy is generated on the blade suction surface and then collected and convected by the blade passage vortex.