photo: Rolls Royce Engineers from Stanford University, Honeywell International and simulation software maker ANSYS are working toge...
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photo: Rolls Royce
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As demand grows for increased gas turbine efficiency, engine manufacturers are challenged with creating designs that operate at higher temperatures. But that becomes a significant challenge as temperatures approach the melting point of some engine component material.
A well-established method for maintaining turbine blade temperatures at acceptable levels is to employ "film-cooling," a technique in which cooler, compressor-discharge air is detoured around the combustor then ejected from precisely-machined holes placed over the surface of the turbine airfoil. Excessive use of compressor air for turbine film cooling can, however, reduce engine efficiency.
Historically, film-cooling-hole-placement on turbine airfoils has been optimized by elaborate experiments, sometimes necessitating engine testing. For decades, research engineers have been developing computer simulations of film cooling geometries with the ambition of reducing – if not eliminating – the need for expensive, time-consuming rig testing.
Stanford, with support from Honeywell and ANSYS®, is performing a new type of testing with 3-D magnetic resonance velocimetry to measure the velocity and concentration field in a test section. These methods measure the turbulent interaction of crossflow jets with the main flow, for a variety of jet configurations and orientations.
These data sets provide an important benchmark against which the large available range of ANSYS turbulence models and computational methods can be compared. The objective is to develop validated models, methods and best practices for prediction of film cooling.
