The Influence Of Variable Diffuser On Compressor Performance And Noise

As the requirements for power and economy increase with marine turbochargers,centrifugal compressors are gradually developing towards high pressure ratio direction.However,the stable operating range and aerodynamic noise performance of centrifugal compressors will deteriorate with the increase of pressure ratio,which greatly limits the application of high pressure ratio centrifugal compressors.To broaden the stable operating range of compressors under high pressure ratio conditions,variable blade diffusers are applied to turbochargers.This article studies the impact of variable blade diffusers on compressor performance and aerodynamic noise through numerical calculations,and the main contents are as follows:Based on computational fluid dynamics,the internal flow field of the compressor at the most efficient operating point and near stall condition under different speeds was calculated by an analysis method.The Mach number,flow angle,turbulence kinetic energy,and velocity distribution law inside the compressor under the near stall condition were studied and analyzed.Using a hybrid CAA method and a design speed of 23500r/min,the aerodynamic noise of the compressor was calculated under the most efficient operating point and near stall condition,and the frequency spectrum characteristics of the aerodynamic noise under the two operating conditions were analyzed.The results showed that the average sound pressure level of the compressor’s aerodynamic noise increased by 1.5d B under near stall conditions.The influence of different numbers of diffuser blades on the compressor characteristic curve was analyzed,and an 18-blade diffuser was selected as the research object,studying the influence of the inlet radius ratio of the diffuser blade on the compressor performance,flow field,and aerodynamic noise.The results showed that as the radius ratio increased from 1.11to 1.17,the blocked flow rate of the compressor increased from 9.92m~3/s to 10.23m~3/s,the flow separation phenomenon in the diffuser channel was significantly weakened,and the average sound pressure level of the aerodynamic noise was reduced by 1.4d B.Eight numerical models of non-uniform distribution of diffuser blades were designed and constructed,and their influence on compressor performance,flow field,and aerodynamic noise was calculated and analyzed.It was found that the non-uniform distribution of diffuser blades would greatly reduce the stable operation range of the compressor.To achieve variable selection of diffuser blades,the front edge,middle,and tail of the diffuser blades were used as the rotation center to rotate the blades,and the influence and mechanism of blade rotation on compressor flow and noise were numerically calculated at different rotating angles.It was found that no matter where the rotation center was,when the blade rotating angle was controlled within 0-5°,the flow rate range of the compressor under near stall conditions could be expanded,and the flow separation in the diffuser channel could be weakened,but it would aggravate the flow separation in the impeller channel and increase the compressor’s aerodynamic noise.