Rodrigo Rodriguez Erdmenger

Impact of Main and Splitter Blade Leading Edge Contour on the Performance of High Pressure Ratio Centrifugal Compressors

The impact of leading edge sweep in an attempt to reduce shock losses and extend the stall margin on axial compressors has been extensively studied, however only a few studies have looked at understanding the impact of leading edge contouring on the performance of centrifugal compressors. The present work studies the impact of forward and aft sweep on the main and splitter blade leading edge of a generic high flow coefficient and high pressure ratio centrifugal compressor design and the impact on its overall peak efficiency, pressure ratio and operating range. The usage of aft sweep on the main blade led to an increase of the pressure ratio and efficiency, however it also led to a reduction of the stable operating range of the impeller analyzed. The forward sweep cases analyzed where the tip leading edge was displaced axially forward showed a slight increase in pressure ratio, and a significant increase on operating range. The impact of leading edge sweep on the sensitivity of the impeller performance to tip clearance was also studied. The impeller efficiency was found to be less sensitive to an increase of tip clearance for both aft and forward sweep cases studied. The forward sweep cases studied also showed a reduced sensitivity from operating range to tip clearance.The studies conducted on the splitter leading edge profile indicate that aft sweep may help to increase the operating range of the impeller analyzed by up to 16% while maintaining similar pressure ratio and efficiency characteristics of the impeller. The improvement of operating range obtained with the leading edge forward sweep and splitter aft sweep was caused by a reduction of the interaction of the tip vortex of the main blade with the splitter tip, and a reduction of the blockage caused by this interaction.Copyright

Influence of Tandem Inducers on the Performance of High Pressure Ratio Centrifugal Compressors

The uses of tandem inducers has been proposed in the past in an attempt to reduce the inducer shock losses and to improve the performance and operating range of centrifugal compressors. However throughout the literature the benefits/penalties of this type of compressor design are still unclear, with contradictory conclusions and very few studies attempting to understand the causes of the observed benefits/penalties. Additionally none of the cases reported for centrifugal compressors has looked into the impact of overlap between the inducer and the main blade. The current study looks into the different aspects of the design of centrifugal compressors with tandem inducers and their effect on the performance of a high flow coefficient, high pressure ratio centrifugal compressor. Aspects such as clocking, axial gap between the inducer and the compressor main blade, axial overlap, and the performance in combination with a vaned diffuser are discussed. Overall the results indicate that it is possible to design centrifugal compressors with tandem inducers that provide similar or even a slight performance benefit at design point, and that tandem inducers can provide significant performance benefits at off design conditions by improving the flow conditions along the main blade suction side, and by improving the inlet conditions to a vaned diffuser. The results also indicate that the impact of the axial gap between the inducer and the main blade has little impact on the compressor performance, that clocking will have a significant impact on the performance of the compressor and that the best performance will be obtained when the tandem inducer is almost aligned with the main blade of the compressor, since this avoids the blockage and losses incurred by other clocking arrangements.© 2015 ASME