Mathematical Modeling And Experiment Investigation For Combined Variable Section Scroll Expander

The Organic Rankine Cycle(ORC)is one of the effective ways to efficiently recover renewable energy such as industrial waste heat and solar heat.As an important part of the ORC power generation system,the turbo expander has an impact on the performance of the organic Rankine cycle system.This paper starts with the mathematical model of the combined variable-section scroll expander and establishes the following models.It includes geometric model,leakage model and heat transfer model.The numerical simulation software is used to analyze the performance of the variable-section vortex expander.The mathematical model is verified by the established test platform.The research content of this paper is mainly described from the following points:(1)The geometric theory of the scroll expander is discussed.The meshing theory of the scroll type of the scroll expander and the conditions for meshing satisfaction are briefly introduced.The principle and determination of the scroll line are described.The line meshing principle and the meshing condition derive the analytical formula of the combined line(circular involute-high-order curve-circle involute),and the profile structure is established.According to the combined line expression,and then according to the scroll expander The running process divides its cavity and solves the volume of each working cavity.Finally,two different tooth head correction methods are introduced,and the volume change of the variable section scroll expander after the tooth head correction and the influence of the correction method on the tooth head strength are compared.The conclusion is as follows: under the same geometric parameters,the area of the wrap corresponding to the double arc plus straight line correction is larger than the area of the wrap of the double arc correction;the effect of the correction on the volume of the expander working chamber is extremely small,so For the thermodynamic analysis of the scroll expander,the corrected wrap tooth approximation can be regarded as uncorrected for the purpose of calculation and analysis.(2)Based on the laws of thermodynamics,the thermodynamic analysis of the whole expansion process of the combined variable-section scroll expander was carried out.The relationship between the mass,temperature and pressure of the working fluid in the working cavity was derived.The combined variable-section vortex was studied in detail.The leakage model of the rotary expander and the expression of the length of the leak line of two kinds of leakage(tangential leakage caused by radial clearance and radial leakage caused by axial clearance)are derived.Through the control variable method(setting the wrap height,wall thickness,internal volume ratio and suction volume),the curve of the radial leak line length of the scroll expander composed of the combined line and the single type line is obtained.(3)According to the model of the established scroll expander and the corresponding relational expressions of each model,the whole cycle operation process is simulated,and the working cavity volume,pressure,temperature and working cavity quality of the scroll expander are analyzed and solved.The curve of the parameters is added,and the performance test platform of the combined variable-section scroll expander is built to verify whether the established models meet the design criteria.