Flow Field Characteristics of a Compressor Under Pulsating Backpressure Based on Q-POD
The transient flow characteristics under pulsating backpressure conditions were investigated for an elec-tric compressor matched with a free-piston engine generator(FPEG).The pulsating backpressure and steady back-pressure conditions were analyzed to reveal the unsteady flow characteristics of different formation mechanisms in-side the compressor.Then,the quadruple proper orthogonal decomposition(Q-POD)method was employed to re-construct the unsteady flow field in reduced order.Based on the local entropy generation rate,decomposed quadru-ple field structure was analyzed to quantify and locate the irreversible losses in the unsteady flow.The results show that the difference in entropy generation with/without pulsating backpressure is close to 17%in the impeller and only 1%in the volute.The entropy generation rate by large-scale perturbed dissipation dominates in the impeller,and entropy generation rate by direct turbulent dissipation accounts for more than 92%in the diffuser.The pulsating backpressure affects the transient flow field structure by changing the large-scale coherent structure.The circumfer-ential development of the large-scale vortex structure in the annular channel is the main factor contributing to the irreversible losses in the diffuser.
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