Investigation On The Internal Flow Field And Vortex Characteristics In Double Side Centrifugal Compressor

The centrifugal impeller is a very important part of the turbocharger,and the double side impeller has the advantages of downsize and good transient response.It was first used in the vehicle turbocharger in 2008.Because of the special structure of the double side centrifugal compressor,the internal flow is complex.In order to understand the internal flow characteristics of the double side centrifugal compressor more clearly,it is necessary to study the flow characteristics inside the centrifugal compressor.In this paper,the flow field structure and vortex structure characteristics of a double side centrifugal compressor under unbalanced inlet conditions are analyzed by unsteady numerical calculation of a simplified double side centrifugal compressor.The main research contents and results are as follows:Firstly,the circumferential flow field in an unbalanced inlet centrifugal compressor was studied.The static pressure distribution inside the diffuser and the unsteady characteristics of the diffuser outlet flow were analyzed.The static pressure propagation and the internal flow field distribution in the double impeller were investigated.Research shows that the circumferential static pressure inside the compressor is decided by volute,more close to the volute,the difference of static pressure inside the compressor is smaller.There is a fluctuation in the flow of diffuser outlet with time.Affected by the impeller structure and impeller rotation,the static pressure distribution at the impeller outlet will propagate downstream.In additional,the flow rate in the impeller channel of the high static pressure region is smaller and the flow rate of the impeller channel in the low static pressure region is larger.Secondly,the asymmetric flow field,vortex structure and mixing characteristics in the shared diffuser under different flow rates are analyzed.The research shows that the circumferential distortion is determined by the circumferential pressure distribution induced by the volute tongue in the large flow rate condition.The high hydrostatic pressure region at the downstream of the volute not only produces a large degree of flow from the rear side to the front side of the diffuser,but also reduces the radial size of the wake vortex and the scrape vortex at the rear impeller.Under the condition of small flow rate,the jet scrape vortex of the rear impeller inclines to the front impeller,and the tailing edge vortex appears,which leads to the phenomenon that a large degree of flow flows to the front side in the whole circumferential direction.Finally,the distribution of leakage flow inside the impeller and the structure characteristics of clearance leakage vortex under different flow conditions are analyzed.The results show that the clearance leakage flow in the high static pressure region is larger,and in the low static pressure region is smaller.Clearance leakage flow is mainly concentrated in the more than 40% relative chord length,there is leakage vortex and reverse leakage vortex in The large flow rate condition.In the small flow rate condition,the main clearance leakage flow is near the leading edge and more than 60% relative chord length in front impeller,mainly concentrated more than 60% relative chord length in the rear impeller.There is only clearance leakage vortex in the small flow rate condition,and the leakage vortex and the rear backflow vortex interacted,produced a great loss.