Design And Numerical Analysis Of Forepart Rotation Guide Vane For A Variable Nozzle Turbine

Turbocharging technology has been widely used in vehicle engine field for its advantages such as improving engine efficiency,decreasing fuel consumption and reducing exhaust pollution.Especially the turbocharger equipped with variable mixed turbine,which could achieve a good match between the turbocharger and engine in whole operating range,has drawn the attention of many researchers at home and abroad.At present,research on adjustable guide vane mixed flow turbine is mainly about guide vane tip clearance leakage flow’s influence on turbocharger efficiency and flow capacity,but only a few about how to reduce the loss because of guide vane clearance leakage flow.Therefore,an adjustable guide vane mixed flow turbine is selected as research model.Firstly,studying the guide vane tip clearance’ influence on turbine efficiency.Then designing a forepart rotating guide vane,analyzing its interior flow characteristics.Finally,further optimizing the guide vane and studying its influence on downstream rotor.The main research results are presented as follow.Compared with guide vane without clearance,the guide vane with clearance enhances the flow capacity while efficiency declines obviously at small and middle opening condition.Forepart rotating guide vane which only has clearance on rotating part decreases the length of clearance.Compared with original one,the intensity and flow rate of tip clearance leakage flow reduces.The process of gas acceleration is more smooth in the guide vane channel,there are no large supersonic flow area also.As for efficiency,the forepart rotating guide vane is higher than original vane,particularly in small opening condition.After researching the characteristics of the turbine interior flow,similar results of circumferential velocity distribution of rotor inlet are found at small and middle opening condition.At the hub and shroud area,there are high and low speed alternating distribution because of tip clearance leakage.But in the middle span,the velocity distribution is regular.At the middle opening condition,the influence range of tip clearance leakage has been reduced compared to small opening condition.At the same time,the tip clearance leakage appear at the position which is close to suction surface of guide vane.Modifying the rear part of forepart rotating guide vane and analyzing its influence on rotor blade.The modified guide vane could effectively reduce pressure fluctuations of rotor blade which is applied by upstream gas,and improve the reliability of rotor blade.