采用中温有机朗肯循环回收重型柴油机排气余热的模拟

Simulation of Waste Heat Recovery from a Heavy-Duty Diesel Engine with a Medium Temperature ORC System

为有效利用重型柴油机的排气余热,设计了中温有机朗肯循环(ORC)系统。在该循环中,采用有机流体R123(CF3CHCl2)作为工质,针对不同循环压力和工质流量以及不同柴油机排气温度,通过模拟计算研究了系统效率的变化规律。研究结果显示,循环压力越高则系统回收效率越高,超临界朗肯循环因为其高的循环压力从而有利于余热的回收。不同循环压力下,工质流量范围发生变化;在固定循环压力下,可用流量范围内存在最高效率点,且循环压力越高最高效率点对应工质流量越低。循环压力不变条件下,不同排气温度下的最高效率值接近,但是最高效率点对应的工质流量随着排气温度的降低而减小。

A medium temperature organic-fluid Rankine cycle （ORC） system was designed to recover the waste heat from a heavy-duty diesel engine. R123 （CF3 CHCl2） is used as the working fluid in the ORC system. Efficiency simulation was carried out under different circulating pressures, mass flow rates of R123 and engine exhaust temperature. The results show that the system efficiency increase with increasing circulating pressure, and supercritieal Rankine cycle is better for waste heat recovery due to its higher circulating pressure. The ranges of mass flow rate of working fluid vary with circulating pressure. There is a maximum efficiency within the mass flow rate range under a fixed circulating pressure. The mass flow rate corresponding maximum efficiency decreases as circulating pressure increases. The maximum efficiency with different exhaust temperature is similar under the fixed circulating pressure. The mass flow rate under most efficient conditions reduces as the exhaust temperature decreases.