Optimization On Organic Rankine Cycle Based On Radial Turbine For Waste Heat Power From Internal Combustion Engine

In the study of waste heat recovery from internal combustion engine, OrganicRankine Cycle (ORC) was getting more and more attentions. In the existing ORCoptimization, due to the lack of structure size and isentropic efficiency variation ofexpander with different working fluids and operating conditions, researchers generallyspecified the isentropic efficiency as a constant, which may affect the results ofworking fluid selection and cycle parameters optimization. To solve this problem, thispaper studied the structure size and isentropic efficiency variation of single-stageradial turbine and the ORC optimization method with optimal isentropic efficiency.Non-dimensional thermal design of single-stage radial turbine was carried out.Structural size and isentropic efficiency variation with the working fluids andoperating conditions was studied. The results show that, in case A (adiabatic indexrange1.1-1.5), isentropic efficiency variation with pressure ratio is similar, which ismainly affected by clearance losses. The meridional channel is stubby. In case B(adiabatic index range1.6-2.3), the higher the adiabatic index is, the lower theisentropic efficiency is. The meridional channel becomes slimmer with the increase ofadiabatic index. The higher secondary flow losses and clearance losses are the mainreasons lead to the lower isentropic efficiency.Under the specified operating condition of internal combustion engine, workingfluid selection and cycle parameters optimization of ORC was carried out, which wasbased on single-stage radial turbine. The optimal isentropic efficiency with differentworking fluids and operating conditions was used in the study, which is the maininnovation to the existing method only using a constant isentropic efficiency. Theresults of the new optimization method, including the optimal working fluid and themaximum net output power, are different from the existing method. The newoptimization method helps to ensure the right design of ORC.