Thermodynamic Characteristics And Experimental Investigation Of Scroll Expander

At present,Organic Rankine Cycle(ORC)system is not only one of the most commonly used ways to improve energy efficiency,but also can make full use of sol ar energy,low-temperature waste heat and other renewable energy without causing environmental pollution.As the core component of ORC power generation system,the performance of scroll expander determines the performance characteristics of the whole ORC system.In this paper,a geometric model and a thermodynamic model are established for the operation of a scroll expander for low temperature waste heat.This paper focuses on the following aspects:(1)First,the basic theory of scroll profile and the basic conditions for meshing are briefly described.Then,the asymmetric double-arc-tooth head modification used in the research and test prototype is described in detail,and the changes of the tooth head area before and after modification are obtained by ana lytical method.The change of content volume of working chamber is simulated by integral method,and the inspiratory volume before and after correction is compared and analyzed.(2)Based on the geometric model of the constant section scroll expander,the heat transfer and leakage model of the entire working process of the scroll expander has been established based on the thermodynamics and energy conservation laws of the variable mass system.By solving the thermodynamic model,many things has been obtained such as the change rules of the volume,mass and pressure of the working medium in the working chamber of the scroll expander with the spindle angle.The parameters like the calculation methods of volumetric efficiency and isentropic efficiency,the performance evaluation indexes of scroll expander are given.The input power,output shaft work and full efficiency of scroll expander are numerically simulated by force analysis of moving scroll disk.The thermodynamic model of constant section scroll expander is analyzed quantitatively,and it is found that its geometric parameters have a very important influence on the performance of the scroll expander.(3)A test platform for the performance of scroll expander driven by compressed air was built.The accuracy of the thermodynamic model was tested and verified by means of the test platform,and the pressure in the working chamber of scroll expander was measured.The results show that with the increase of inlet pressure,the rotational speed,outlet pressure and volumetric flow rate of scroll expander also increase.By comparing the measured output power with the theoretical output power,it is found that the maximum deviation between the measured value and the ideal value of the output power is 46 W,and the minimum deviation is 15 W.The measured result of the output power of the maximum deviation within 3.9%,which verifies the accuracy of the thermodynamic model built.By monitoring the pressure inside the chamber,the curve of the pressure inside the working chamber changing with the angle of rotation under the same inlet pressure and different rotating speed is obtained.