| The utilization of residual heat by ORC(Organic Rankine Cycle)is one of the ways to alleviate the energy crisis and environmental problems.In this paper,modeled and analyzed the variable wall thickness scroll expander which can be used in ORC system.The research contents are as follows:(1)Firstly,the meshing theory of plane curve is introduced.The conditions for realizing the meshing of scroll profile are obtained.The basic requirements for forming the scroll profile are described,and the basic structural parameters of the scroll profile are introduced.Two kinds of tooth head correction methods,double arc correction and double arc and straight line correction,are constructed.The corrected tooth area of two kinds of tooth head correction is deduced.(2)The geometric models of the combined profile of circular involute-high degree curve,circular involute-arc and variable base circle radius vortex are established respectively.In this paper,the occupation ratio model of high-order curve combined profile and circular arc combined profile is constructed;the volume calculation of scroll profile with variable base circle radius is deduced.At the same time,the mathematical model of leakage is established.(3)According to the established geometric model and mathematical model of each variable wall thickness scroll profile,the initial parameters of each variable wall thickness profile are obtained.The influence of the corresponding initial parameters on the modified tooth area and the modified area coefficient of the two kinds of tooth head correction is analyzed.It is concluded that the modified tooth area is directly proportional to the occurrence angle,the correction angle and the radius of the base circle of the involute,and the corrected area coefficient is inversely proportional to the occurrence angle of the involute,and is directly proportional to the correction angle.By analyzing the influence of initial parameters on the proportion of product of high-order curve combination profile and arc combination profile,it is concluded that the area of both profile is proportional to the radius of base circle and terminal involute angle,the proportion of product is inversely proportional to the radius of base circle and terminal involute angle.The results show that the volume of the vortex profile with variable radius of the base circle decreases with the increase of the control coefficient of the base circle,and the leakage increases with the increase of the control coefficient of the base circle.It provides a reference for the optimization analysis.(4)Introduced the theory of single objective and multi-objective optimization,as well as the optimization methods of genetic algorithm and particle swarm optimization.Genetic algorithm is used to optimize the modified area and the modified area coefficient of the two kinds of tooth heads,and the area and the proportion of product of the combined high-order curve and the combined arc curve are analyzed.Particle swarm optimization(PSO)is used to optimize the disk diameter and expansion ratio of the scroll profile with variable base circle radius.The value of the initial parameters of each optimization objective under single objective optimization and the value of the initial parameters corresponding to the non-inferior solution set of each optimization objective under multi-objective optimization are obtained.(5)Through the establishment of the test platform of the scroll expander,the test of the expander with the combination of the circular involute scroll and the high-order curve was carried out.The voltage,current and power of the two kinds of expanders are measured with the change of the intake pressure,and the comparison shows that the performance of the high-order curvilinear scroll expander increases obviously in the range of the intake pressure.The changes of exhaust pressure,mass flow rate and rotation speed of the combined high-order curve with the intake pressure are tested,and the direct ratio among them is obtained. |
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