Abstract

Statistics based models have been developed previously to predict a priori the performance of new radial flow compressors and pumps and to model test data of previously designed and tested machines. Unfortunately, critical dynamics in the inlet region of the machines were neglected. Consequently, room for improvement in the previous modeling exists. Historical practice has placed a static pressure tap on the shroud just upstream of the impeller leading edge for experimental characterization. The previously developed statistics based models rely on this measured data. However, the location of the tap may be vulnerable to high gradients which would decrease the dependability of the developed models. Full Computational Fluid Dynamics (CFD) and Multi-Stream Tube (MST) analysis were performed to test the appropriateness of the historically placed static pressure tap location and to characterize the inlet flow of typical radial flow turbomachines. All designs and test data were provided by ConceptsNREC and have been collected for over 40 years. Eleven machines were chosen for investigation to provide a wide variety of inlet geometric and flow conditions. The results derived from the Computational Fluid Dynamics and Multi-Stream Tube analysis suggest that the historically placed static pressure tap location is an inappropriate anchor point for model development. Steep gradients in the static pressure indicate that a relatively minor movement of the static pressure tap would significantly alter the experimental results and generate noise in statistical modeling. While large variations in the pressure field are apparent near the impeller leading edge for all machines considered, the study results show that the flow field is uniform and very predictable when well upstream of the impeller leading edge. Specifically, a point 3 blade height upstream from the impeller leading edge appears to be a sound location to anchor model development. The model is highly dependent upon the flow parameters in the inlet passage. Thus it is important to ensure that the model is anchored at a location where the flow conditions are known to be stable and good. Future anchoring of the model upstream of the impeller leading edge will lead to a more accurate prediction and modeling of the design performance for radial flow turbomachines.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

Rights

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