Experimental investigation and energy conversion modelling of radial diffuser for centrifugal compressor

Centrifugal compressor is seen as the predominant choice in turbocharging and natural gas transportation. The energy loss measurement in centrifugal compressor is of great essence, especially under instability conditions. Based on one-dimensional model and simulations, each energy loss mechanism in diffuser was evaluated by defining the weight coefficient representing the influence of energy loss on compressor performance. The thermodynamics in the diffuser was investigated under design and stall inception conditions. Vortex transportation and synergy angle analysis was realized to identify the correlation between energy losses and stall identification. The results indicate that the skin friction loss accounts for 75.06% of the total energy loss in diffuser, while 16.96% and 7.98% for diffusion and secondary loss near stall condition, respectively. The determination of stall in vanless diffuser may be confirmed according to the combination of secondary vorticity coefficient and synergy angle. Due to small inflow angle and large width ratio of the diffuser, stall inception is the results of secondary flow sweep and momentum loss induced by diffusion. The weight function was originally modelled to quantize the influence of energy loss on flow aerodynamics. The present work may shed lights on stall identification and energy loss reduction in industrial compressor.