A study of trailing-edge losses in organic Rankine cycle turbines
More Info
In this paper, vane trailing-edge losses which occur in organic rankine cycle (ORC) turbines are investigated. Experiments are performed to study the influence of dense gas effects on trailing-edge loss in supersonic flows using a novel Ludwieg tube facility for the study of dense-gas flows. The data is also used to validate a computational fluid dynamics (CFD) flow solver. The computational simulations are then used to determine the contributions to loss from shocks and viscous effects which occur at the vane trailing edge. The results show that dense gas effects play a vital role in the structure of the trailing-edge flow, and control the extent of shock and viscous losses
Direct Numerical Simulations of a High-Pressure Turbine Vane
More Info
In this paper, we establish a benchmark data set of a generic high-pressure (HP) turbine vane generated by direct numerical simulation (DNS) to resolve fully the flow. The test conditions for this case are a Reynolds number of 0.57 x 10(6) and an exit Mach number of 0.9, which is representative of a modern transonic HP turbine vane. In this study, we first compare the simulation results with previously published experimental data. We then investigate how turbulence affects the surface flow physics and heat transfer. An analysis of the development of loss through the vane passage is also performed. The results indicate that freestream turbulence tends to induce streaks within the near-wall flow, which augment the surface heat transfer. Turbulent breakdown is observed over the late suction surface, and this occurs via the growth of two-dimensional Kelvin-Helmholtz spanwise roll-ups, which then develop into lambda vortices creating large local peaks in the surface heat transfer. Turbulent
Stall, Surge, and 75 Years of Research
More Info
Work on rotating stall and its related disturbances have been in progress since the Second World War. During this period, certain "hot topics" have come to the fore-mostly in response to pressing problems associated with new engine designs. This paper will take a semihistorical look at some of these fields of study (stall, surge, active control, rotating instabilities, etc.) and will examine the ideas which underpin each topic. Good progress can be reported, but the paper will not be an unrestricted celebration of our successes because, after 75 years of research, we are still unable to predict the stalling behavior of a new compressor or to contribute much to the design of a more stall-resistant machine. Looking forward from where we are today, it is clear that future developments will come from CFD in the form of better performance predictions, better flow modeling, and improved interpretation of experimental results. It is also clear that future experimental work will be most effect