Research On Influence Of Pump-turbo Gap On Performance Of Adjustable Hydraulic Torque Converter

Hydraulic speed control device plays an important role in the power transmission system of pump and wind turbine.Double-turbo adjustable hydraulic torque converter has advantages such as high power capacity,broad high-efficienfy zone,relatively big starting torque and absorbing vibration/impact,e.t.c.This paper does a research on the influence to performance parameters,inner flow field and pressure pulsation from pump-turbo gap in adjustable hydraulic torque converter by CFD simulation.Specifically,the researched object is the type Y615 double-turbo-double-vane hydraulic torque converter,by using Blade Gen for 3D modeling,Turbo Grid for meshing,and CFX for steady and transient simulation and post-result analysis.Since hydraulic torque converter has many types and complicated inner structure,some design principle still remain unclear.In some types,the pump and the turbo locate side by side.With the difference in rotating speed and small distance between them,their interference to each other has a big influence on the whole torque converter in many aspects,like effiency and pressure pulsation.This paper mainly focuses on the difference on these aspects caused by changing pump-turbo gap.While keeping the leaf angle constant,adjust pump-turbo gap by changing the radius of centrifugal turbo's front edge.By calculating different pump-turbo gap conditions,analyze and compare their performance,flow field and pressure pulsation.As for the analsis result,among all neighbouring impeller pairs,the pump and the centrifugal turbo have the greatest interference.Other can be mostly put out of consideration.The outflow from the pump is very uneven circumferentially,making turbo blade suffering period impact.And because of the impact between fluid and turbo blade,there is a high-pressure zone before turbo blade,which do a pressure pulsation to pump when sweeping over it.Besides,there is a low-speed-low-pressure turbulent flow at the back side of pump,which produces inregular flow field,absorbs outer pressure pulsation,and generating a pressure pulsation with different frequency.The most important factor for setting pump-turbo gap is the size of high-pressure zone in front of turbo blade.The pump-turbo gap has influence on the performance parameters of torque converter,i.e.efficiency curve and torque parameter.It also decides the strength of the pressure pulsation.The smaller the pump-turbo gap is,the stronger the rotor-stator interference is.Conversely,when the pump-turbo gap is bigger,the pressure of outflow from pump impeller spread uniform periodicly during no-blade passage,weakening the pressure pulsation phenomenon and rising efficiency.However,if the pump-turbo gap is too large,the torque parameter decreases.As a summary,every possible aspect should be taken into consideration to choose a reasonable pump-turbo gap.