Turbomachinery Aero Design; Getting It Right the First Time

Many papers have been written showing that Computational Fluid Dynamics (CFD) codes can yield results that match experimental data. These papers are presenting results which are post-diction. By this it is meant that the CFD results were obtained after the experimental data was acquired. The true test of the predictive capability of a CFD code is being able to predict what will be observed prior to the test being run. In particular predicting the aero-performance of the initial build of a turbomachine whose aero design parameters lie outside the range of previous machinery. This paper addresses our ability to successful execute such simulations and also of equal importance calling attention to sensitivities of aero performance parameters to geometrical features as well as poorly understood inflow and outflow leakages. Thus the title ‘Turbomachinery Aero Design; Getting It Right the First Time’. A short discussion is presented which identifies geometrical features whose neglect can compromise the accuracy of a simulation. This is followed by a short discussion of the uncertainties in accounting for flow leakages both inflow and outflow. Three examples of sensitivity studies are presented and their results discussed. Finally a series of conclusions are drawn based on the material presented.