Effects Of Volute Tongue Bioinspired By Leading Edge Of Owl Wing On Aerodynamic Performance And Internal Flow Characteristics

Double-suction multi-blade centrifugal fan is widely used and has a compact structure..The airflow impact induced by the volute tongue of the multi-blade centrifugal fan is vital in the operation of machines.The shape and installation angle of the volute tongue affect the energy loss around the volute tongue and the internal flow circulation of the volute directly,thus affecting the aerodynamic performance of the fan.Through numerical simulation,the internal flow of the fan under different flow conditions is observed.It is found that the impeller-volute tongue interaction has distinctly influence on the internal flow field of the fan.In the off-design flow conditions,the inflow condition is complicated,and the pressure pulsation is not only affected by the impeller passing frequency,but also a large period and evident fluctuation caused by the stall.Therefore,in term of the improved design,it is necessary to consider the aerodynamic performance of the fan under off-design conditions.The profile of the leading edge of the owl wing is applied to the volute tongue of multi-blade centrifugal fan to improve the aerodynamic performance of the fan.The fan models with different volute tongue installation angles are numerically simulated under different flow conditions.The research show that,there is the very designed fan model with the best aerodynamic performance under each specific flow rate condition.The research show that he application of the bionic volute tongue is beneficial to reduce the area of static pressure mutation of the fan and to improve the flow stability of the volute tongue clearance.In addition,an improved method for quantitatively evaluating the level of impeller-volute tongue interaction based on the unsteady simulation result is proposed and verified effectively.Furthermore,the three evaluative parameters of internal flow circulation influenced by the installation angle of the bionic volute tongue are analyzed,namely the recirculated flow coefficient,the reversed flow coefficient,and the axial flow coefficient.Then,combined with the analysis of energy loss at the volute tongue and effective circulating flow in volute,the mechanism of variation of the aerodynamic performance of the multi-blade centrifugal fan with different volute tongue installation angles is explained.