基于单螺杆膨胀机的发动机排气余热回收系统

摘要

针对发动机排气余热的特点,设计了有机朗肯循环(ORC)排气余热回收系统,采用单螺杆膨胀机作为动力输出装置,采用R245fa作为工质,提出了发动机排气余热利用率的概念和计算方法.结合发动机的试验数据,分析了ORC工质蒸发压力和发动机转速对ORC系统性能的影响,确定了适用于ORC系统的工质蒸发压力的最佳值.研究结果表明,当工质蒸发压力为3.0 MPa时,ORC系统能够在发动机全转速范围内正常工作,并且ORC系统的净输出功率最高可达12.1 kW,热力学第一定律效率最高可达11.27％,热力学第二定律效率最高可达25.8％,发动机排气余热利用率最高可达8.9％,发动机排气余热回收效果明显.%In order to make better use of waste heat energy from engine exhaust gas, the waste heat recovery system based on organic Rankine cycle (ORC) was presented, a single screw expander was used as the power output device, R245fa was used as working fluid, the concept and calculating method of waste heat recovery utilization rate was introduced. On the basis of engine test results, the effects of working fluid evaporating pressure and engine speed on the ORC system performance were analyzed and discussed, and then the optimal value of working fluid evaporating pressure was selected. According to the research results, when the working fluid evaporating pressure is 3.0 MPa, ORC waste heat recovery system can work properly over the whole range of engine speed, the maximum of net power is 12. 1 kW, the maximum of first law efficiency is 11.27% , the maximum of second law efficiency is 25.8% , the maximum of waste heat recovery utilization rate is 8. 9% , waste heat energy from engine exhaust gas can be recovered effectively.