Study On Deformation Of Scroll Expander For Vehicle Waste Heat Recovery Under Different Geometric Structures

In order to cope with the energy crisis and improve energy efficiency,the use of organic Rankine cycle(ORC)to recycle engine exhaust waste heat is an effective way.Due to its high efficiency,low noise,stable operation,compact structure,good reliability,small flow rate and high expansion ratio,the scroll expander has become the preferred work component in the current vehicle waste heat recovery system.In this paper,a scroll expander of ORC waste heat recovery system of vehicle engine is taken as the research object,and the unsteady internal flow characteristics and scroll deformation law of scroll expander under the change of key geometric structure are discussed.Firstly,the fluid-thermal-solid multi-field coupling numerical solution method and condition parameter setting suitable for the research of scroll expander are determined in this paper.On the basis of verifying the reliability of the numerical model,by changing the structure of the basic profile of the scroll expander,the structural characteristics of the fixed base circle involute profile,the variable radius base circle involute profile and the arc combination profile of various types of expanders are discussed,including the working chamber volume change rule and the leakage line length comparison.The flow field distribution differences and scroll deformation characteristics under different profile structures were studied.It is found that the length of the leakage line of the expander under the arc combination line is significantly shortened,which is 19.11 % less than that of the fixed base circle involute.The suction chamber volume of the combined arc profile is larger,the internal flow field distribution is more complex,and the pressure change range of the adjacent working chamber is larger,which causes the unstable operation and large deformation fluctuation of the expander.Secondly,the scroll tooth head is modified by two kinds of profile structure,and the influence of different tooth head modification forms on the flow field of the central cavity of the expander is discussed.The strength,stiffness change and deformation difference of the tooth head under different tooth head modification are discussed.The results show that the correction form of double arc plus straight line will effectively increase the area of the tooth head of the tooth head,thereby increasing the strength of the tooth head,and the lifting range is within 7 %.However,this combined correction form makes the curvature of the tooth head wall change greatly,resulting in a stronger non-uniform distribution of the central cavity flow field.Under the action of internal pressure,the deformation of the tooth head under the double arc plus linear correction is reduced by about 20 % compared with the arc correction.The deformation of the tooth head decreases with the decrease of the correction angle γ,so the proper reduction of the correction angle is helpful to reduce the deformation of the tooth head.Finally,by opening air inlets with different shapes and structures,the tooth head intrusion rate,air intake characteristics,effective flow area,air pulsation distribution and scroll tooth deformation law under throttling effect are discussed.It is found that the waist inlet has a shorter tooth intrusion time,a wider opening duration angle of the inlet,and a larger effective circulation area at the same rotating disk angle.The opening characteristics of the waist inlet are significantly improved compared with the circular inlet.The deformation difference of scroll teeth caused by different inlet shapes is mainly reflected in the front end of scroll tooth.The deformation under the waist inlet is greater than that under the circular inlet,and it is mainly caused by the temperature load.