涡轮增压柴油机余热利用的有机郎肯循环烃类高温工质热力学分析

通过能量分析和㶲分析，对涡轮增压柴油机的不同余热源进行优选；在此基础上，对余热利用的有机朗肯循环进行了热力学分析，选取了10种烷烃类高温工质，通过建立能量平衡方程和㶲分析方程，研究了蒸发压力对不同烷烃类工质的热效率、单位质量烟气净功、㶲效率、系统㶲损和膨胀机体积流量比（VFR）的影响规律。结果表明：废气再循环余热为最佳热源；所有工质的热效率、单位质量烟气净功、㶲效率和VFR随着蒸发压力的增加而增加，㶲损随着蒸发压力的增加减少；相同蒸发压力下，直链烷烃类工质的热效率、单位质量烟气净功、㶲效率和VFR随着工质临界温度的增加而增加，㶲损随着工质临界温度的增加而减少；在保证VFR≤50的工况下，环戊烷具有最高的热效率和㶲效率。

Thermodynamic analysis of an organic Rankine cycle for waste heat recovery of a turbo-charged diesel engine based on working fluids of alkanes

An organic Rankine cycle system used in a turbo-charged diesel engine waste heat recovery was proposed and analyzed. In order to select the best waste heat source of engine,the available energy of different waste heat sources was compared based on energy analysis and exergy analysis. Then,the thermodynamic analysis of organic Rankine cycle for recovering waste heat from engine was presented. The cycle parameters based on 10 working fluids of alkane,including the thermal efficiency(η),net power output per unit mass flow rate of exhaust(P_n),exergy efficiency(η_ex),total exergy destruction rate(I_tot) and turbine volume flow ratio(VFR),were analyzed and optimized. The impacts of evaporating pressure on the parameters of the cycle were performed by establishing the energy and exergy model of the organic Rankine cycle. The results showed that the EGR waste heat was the best heat source. The η,P_n,η_ex and VFR of selected working fluids increased with the increase of evaporating pressure,while I_tot decreased. The η,P_n,η_ex and VFR of linear alkanes increased with the increase of critical temperature,while I_tot decreased under the same evaporating pressure. Cyclopentane was considered as the most suitable working fluids when taking into account of VFR ≤50,which had the highest thermal efficiency and exergy efficiency in all the selected alkane working fluids.