柴油机尾气余热回收系统的能分析和火用分析

Energy and exergy analysis of an exhaust energy recovery system for a diesel engine

采用R245fa作为循环工质,利用有机朗肯循环回收柴油机尾气余热,从而提高柴油机的燃油经济性。对不同蒸发压力下的朗肯循环热效率和发动机不同工况下余热回收系统的火用效率以及系统各组件的火用损失率进行了计算和分析。研究结果表明,蒸发压力越高则朗肯循环效率越高,工质和尾气之间传热的不可逆损失和蒸发器出口较高的尾气温度使得蒸发器的火用损失率最大,采用余热回收系统回收发动机尾气余热,系统输出净功最高可达18.7 kW。

Exhaust energy of a diesel engine was recovered with organic Rankine cycle for improving fuel economy.R245fa was used as the working fluid in the Rankine cycle.Thermal efficiency of Rankine cycle was calculated under different evaporation pressures.Exergy efficiency of exhaust energy recovery system and exergy loss percentage of every component was carried out under various engine conditions.The results show that the Rankine cycle efficiency was increased with the increase of evaporation pressure.It was also found that the boiler had the maximum exergy loss percentage in the system which was caused by the high outlet temperature of exhaust gases in boiler and irreversible loss of heat transfer between cycle fluid and the exhaust gases.The net power output value of waste heat recovery system was up to 18.7 kW.