Study Of The Different Outlet Angles Of Diffuser Flow And Performance Of Centrifugal Compressor Stage

Centrifugal compressor plays an important role in all sectors of the national economy,especially in the industries of metallurgy,chemical industry,gas industry,machinery,and so on.Vaned diffuser is a core stator component in centrifugal compressor,it play a key role in enhancing pressure ratio and compressor efficiency,improving the best work condition,so the research about different outlet angles of diffuser in variable condition is very meaningful.The essay is based on the first stage of centrifugal compressor,the different outlet angle of diffuser on single stage are investigated by numerical simulation.the performance curve at stage with different outlet angle are measured,analyze the flow streamline and static pressure distribution in different blade height,and the total pressure in different radius cross section to summarize the diffuser mechanism of the internal flow and losses;at the same time through the pressure recovery coefficient of different diffusers under different working condition to compare the diffuser effect;Using the concept of velocity distortion index to analyze inhomogeneity in diffuser and confirming critical value of velocity distortion when the separation generates;analyzing the shroud-hub absolute Mach number distribution in diffuser representative position.The result show that the increase of outlet angle makes the performance curve move toward the large flow rate side,and the peak stage efficiency and pressure ratio is increased firstly then decreased but their change and the maximum operating condition are not obvious;diffusion effect of vaned diffuser depend upon flow condition during different operations,when the flow is smaller than design level,the separation zone are firstly emerged in larger outlet angle at diffuser,and the vortex develop from ventral outlet to its inlet,having less effect on the total pressure losses;When the flow is larger than design level,the separation zone generates near the pressure surface and the vortex region develop in different location with different outlet angle of diffuser,the vortex develop from blade leading to trailing edge,having bigger effect on total pressure losses;diffuser in different blade height have different static pressure and flow situation,the fluid condition in shroud side is better than hub side;when velocity distortion index is lower than 0.8,diffuser generate separation losses;outlet angles of vaned diffuser have no obvious effect on inlet of diffuser flow.