单螺杆膨胀机双循环系统的应用——基于柴油机尾气余热利用的方案计算

Application of Dual Cycle System with Single Screw Expander——Based on Exhaust Heat Recovery for Diesel Engine

为了提高柴油机燃料燃烧能量利用率,以某增压柴油机为例,设计了单螺杆膨胀机双循环系统来回收柴油机尾气余热能量。此系统由朗肯循环(水为工质)与有机朗肯循环(R245fa为工质)组成,由单螺杆膨胀机输出动力。建立双循环系统热力学模型,对其性能进行热力学分析计算,并确定合理的工作范围。可得出如下结论:随着柴油机尾气(水蒸发器出口处)温度升高,双循环系统的热效率降低;朗肯循环水蒸气蒸发温度在170℃到300℃时,可获得较高的热效率和较低的蒸发压力。

In order to improve the total thermal efficiency of diesel engine, a novel dual cycle system with single screw expander was presented to recover exhaust heat for turbocharged diesel engine. The dual cycle system included Rankine cycle （water was used as working fluid） and organic Rankine cycle （R245fa was used as working fluid） , power was put out by single screw expanders. Based on the thermal dynamic model of the dual cycle system, the thermal performance was discussed, and the reasonable operation range was determined. The analysis results show： Firstly, with the temperature increasing of diesel engine＇ s exhaust gas from the water evaporator exit, the thermal efficiency of dual cycle system is decreased. Secondly, when the evaporating temperature of Rankine cycle is from 170℃ to 300℃, the higher thermal efficiency and lower evaporating pressure of the dual cycle system can be obtained.