Investigation On The Performance Of Variable Thickness Scroll Expander

Scroll expander is the key equipment of the organic Rankine cycle(ORC).The performance of scroll expander has a decisive influence on the whole system.The structure of variable thickness scroll expander is special,and the change of medium condition is more complicated in the working process.So it is very important to investigate the performance of variable thickness scroll expander.In the paper,the research object of this paper is the variable thickness scroll expander.A detail mathematical modeling including geometric modeling,leakage modeling,heat transfer modeling and dynamic modeling is established.The mathematical modeling has been implemented into Matlab and FORTRAN computer code.The performance of variable thickness scroll expander is studied.The main research work is as follows:(1)The variable thickness combination profile consists of circle involute I,high order curve and circle involute II.The double arcs and the transition straight line are selected as modification profile of the tooth head.According to the continuous meshing principle of scroll tooth surface,contact condition of the conjugate surface and the establishment method of variable thickness combination profile baseline,the profile equation of variable thickness scroll expander is developed.The detailed change of the working chamber volume(suction,expansion and discharge)with respect to the orbiting angle has been derived based on geometrical modeling.The change of the working chamber volume for the variable thickness and constant thickness scroll expanders is compared under different condition.(2)The leakage modeling is established and the variation of the leakage line length for the variable thickness and constant thickness scroll expanders is analyzed and compared.The change of the gas forces acting on of the orbiting scroll with respect to the orbiting angle has been derived.The calculating method of the output power is given.Based on the established thermodynamic modeling,the variation of the pressure and mass in the working chamber with respect to the orbiting angle is analyzed and calculated.(6)According to the developed mathematical modeling,the performance of variable thickness scroll expander is investigated under the influence of leakage and heat transfer.The experiment rig for variable thickness scroll compressor is set up.The displacement and power are tested under different suction pressure.The results prove that the proposed mathematical modeling can accurately describe all the suction,expansion and discharge processes for variable thickness scroll expander.