Working Process Analysis And Experimental Research Of Scroll Expander For Organic Rankine Cycle System

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. Organic Rankine Cycle(ORC) system is a much effective, environmental technique which can generate power from low grade energy. That makes it a hot spot of low grade energy technology research. The research of the expander is a key point of the study of ORC. Scroll expander is compact and inexpensive. Because of its potential superior performance, many researchers choose it as the expansion components of the ORC system. This paper analyses the working processes and does experimental research of scroll expander based on the previous research and the actual geometrical theory of scroll expander.The method of composition of scroll profiles is studied. The general method of composition for scroll profiles based on the general geometrical theory of the scroll compressor has been deduced. The profile of the experimental scroll expander is measured. Basing on the accurate parameters of the profile, the working processes of the scroll expander is drawn. In order to examine the performances of the expander, Matlab is used to make a thermodynamic calculation and simulation of the scroll expander with NIST software, R245fa as working fluid.Two basic parameters to the performance evaluation of the expander is studied—volume efficiency and isentropic efficiency—together with the influence factors and the calculation method of them. After determining that internal leakage is the main factor affecting the volume efficiency, the defects of the general leakage models is discussed and a new leakage model is proposed. After investigating the general calculation method of isentropic efficiency, the result shows that general calculation method for isentropic efficiency can’t represent the actual performance of the expander perfectly, therefor it is necessary to propose an concept of internal isentropic efficiency to represent the real performance of the expander.The torque output characteristics and influence factors of the scroll expander is studied. With the Combination of experiment and isentropic inflation process simulation, the average leakage factor L Fis provided. But experimental result showed that the error of the new leakage model is too large to use. The error is due to the big fluctuation of the working fluid. With the comparison between experimental data and simulation data, internal- isentropic efficiency is provided. The result shows that the external-isentropic efficiency can’t be used to evaluate the performance of the expander because of the great fluctuation.