基于 Q-POD 的脉动背压下压气机流场特性

The transient flow characteristics under pulsating backpressure conditions were investigated for an electric compressor matched with a free-piston engine generator(FPEG). The pulsating backpressure and steady backpressure conditions were analyzed to reveal the unsteady flow characteristics of different formation mechanisms inside the compressor. Then,the quadruple proper orthogonal decomposition(Q-POD) method was employed to reconstruct the unsteady flow field in reduced order. Based on the local entropy generation rate,decomposed quadruple 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 circumferential development of the large-scale vortex structure in the annular channel is the main factor contributing to the irreversible losses in the diffuser.