柴油机全工况下抽气回热式有机朗肯循环系统分析

针对一台车用柴油机的排气能量变化规律,建立了抽气回热式有机朗肯循环(RORC)系统,分别采用纯工质R245fa和非共沸混合工质Mix(异戊烷与R245fa按照摩尔比例7∶3组成的混合工质),研究了抽气压力这一参数对RORC系统净输出功率、系统热效率、工质质量流量等性能的影响;进而确定Mix抽气压力1.15 MPa,R245fa抽气压力1.2 MPa,在柴油机全工况范围内,对比分析了采用2种工质的RORC系统的净输出功率、效率、工质质量流量等性能随柴油机转速和转矩的变化情况,结果显示,在柴油机全工况范围内,与采用R245fa的RORC系统相比,采用Mix作为工质的RORC系统的余热回收效果更佳。

Performance of Regenerative Organic Rankine Cycle over Whole Operating Range of Diesel Engine

A regenerative organic Rankine cycle (RORC) system is designed to recover the exhaust heat of diesel engine. The organic working fluids under investigation are the pure fluid R245fa and the zeotropic mixture Mix (isopentane and R245fa mixed in 7/3 mole fraction). The influence of intermediate pressure (pressures at which the steam is extracted from the expander) on the performance parameters of the RORC system, such as the net power output, the thermal efficiency, and the mass flow rate of the working fluid, are analyzed, and on the basis of the analysis results, the intermediate pressure is set to 1.15MPa for the RORC system using Mix and 1.2MPa for the RORC system using R245fa. Then the performance of the RORC system using the two different working fluids is analyzed over the whole operating range of the diesel engine, respectively. The calculation results show that Mix is the better selection for the RORC system than R245fa.