The Mathematical Model Analysis And Transient Simulation Of Scroll Expander

As the energy and environmental pressure becoming more and more prominent,people have been paying much more attention to the value of the low grade renewable energy gradually.Utilizing Organic Rankine Cycle(ORC)to recover the industrial waste heat,solar heat,geothermal heat,engine exhaust heat is one of the effective technological approaches to realize energy conservation,emission reduction and environmental protection.Expander is a key component of the ORC,its performance has a significant effect on the overall ORC system.This paper presented a mathematical model for scroll expander and analyses the working processes,the numerical simulation analysis of internal flow field of scroll expander based on the previous research.The main content is as follows.(1)The meshing theory for scroll profiles was introduced,and the basic criteria of meshing was illustrated.The modification of scroll pro file based on the geometry of the circle involute is discussed.The analytical method is used to calculate the area change of scroll wrap for EA-SAL.The volume and derivative volume of the working chambers with respect to the crank angle are gotten by int egral method.The modification of the scroll wrap has little effect on the suction volume but the profile stiffness obviously increases compared with the volume of the suction chamber for modification profile and no modification profile;(2)The change of the working chamber volume for constant thickness and variable thickness scroll expander with respect to the orbiting angle based on the geometric modeling is derived.A mathematical modeling based on energy and mass balance is established.Temperature,pressure,and mass of working chamber are investigated by solving the mathematical modeling.The relation between the geometric parameters and performance has been revealed through quantitative analysis on mathematical modeling of the scroll expander;(3)The CFD based 3D unsteady flow numerical simulations were performed on scroll expanders,the flow characteristics,mechanical properties and output torque and power at different speeds of the scroll expander are analyzed in detail and combined local reconfiguration with dynamic mesh technology and working fluid R134 a.The analysis shows that the mass flow rate of inlet and outlet increases with the raise of spindle speed,the output torque of expander decreases with the raise of spindle speed,and the output power increases gradually.When the expander speed and outlet pressure is constant,the output torque and output power increase with the increase of inlet pressure.The result is in good agreement with the numerical solution.