Research On Power Generation System And Thermodynamic Calculation Of Radial Turbine For Organic Rankine Cycle

Organic Rankine Cycle(ORC) has been applied for electricity generation by recovering low temperature waste heat taking advantage of low boiling point of the organic fluids to promote turbine to work which plays an important role for conserving energy and reducing emissions if fully exploited. Most studies on ORC thermal performance focus on the cycle system itself and the influence of heat absorption is often ignored.In this paper, two systems——ORC with and without internal heat exchanger(IHE) were established with the flue gas as the heat source. Based on the heat absorption change with changing the parameter of heat source, the change regulations of inlet temperature, network, heat consumption and exergy loss in the two systems mentioned were analyzed with 11 selected fluids, and the better working fluids and their IHE matching showed up. With the selected pure working fluids collocated as different components, the change regulation of temperature and thermal performance of zeotropic mixture under different mass proportioning were obtained. The results show that every working fluid shows different IHE matching, and R123 shows the worst matching property; Under the set conditions, the comprehensive results show R236 ea, R600 a are the best choices, and R245 fa, R600 are relatively suitable fluids; For mixture working fluids, the larger difference between components' boiling points, the more thermal properties improved compared to the corresponding pure fluids, and through comparison of thermal and economical efficiency, the better working conditions are as follow: cyclohex+R236ea(2:8?4:6)?cyclohex+R245fa(4:6)?R601+R236ea(6:4)and R601+R245fa(6:4).The paper took the selected mixture working fluids into thermodynamic calculation of turbine, and the respective critical geometrical structures parameters and efficiencies could be obtained. Sieve method was used to get the reasonable range in the xa-? graph in which the best efficiency of the wheel periphery was found, and after testing the structure rationality, the results of thermodynamic design were determined. The results show that just two rational turbines were gotten.ie R601+R236ea(6:4)and R601+R245fa(6:4). The other two designs on corresponding working conditions were not successful due to the overhigh pressure ratios.Substitution of actual turbine efficiency into system calculation established a new cycle, ie actual cycle, and this paper analyzed the factors that influence the thermal efficiency of actual cycle and difference in thermal performance between actual cycle and ideal cycle of the working fluids respectively. The results show that the thermal efficiency of whole cycle will improve with higher pressure ratio although the actual turbine efficiency will get lower. And from working fluid performance prospect, it is different between the two cycles, especially in low heat absorption zone, R600, R600 a and R123 perform a lot better in actual cycle. For mixture fluids, the best mass proportioning might change in actual cycle with the same components. In addition, under the same heat absorption condition, ORC with IHE is better for its better thermal performance and lower pressure ratio which make the turbine design easier.