混合工质和纯工质对柴油机余热回收系统性能影响的模拟

Simulation of the Effects of Mixed-Refrigerants and Pure Refrigerants on Diesel Engine Waste Heat Recovery System

通过研究一台柴油机变工况下的排气特点,设计了一套有机朗肯循环余热回收系统,根据数值计算结果,对比分析了4种纯工质、4种共沸混合工质和4种非共沸混合工质对变工况下车用柴油机有机朗肯循环余热回收系统性能的影响.结果表明,随着柴油机转速和油门开度的增加,12种有机工质的有机朗肯循环(ORC)系统净输出功率和系统及各部件()损率逐渐增加,但增幅不同.采用共沸混合工质R504的有机朗肯循环系统在柴油机变工况下的平均净输出功率最大,约为7.29,kW,比采用纯工质R227ea的ORC系统平均净输出功率提高了18%,采用混合工质的ORC系统热效率普遍高于纯工质.与纯工质相比,采用非共沸混合工质R415B的ORC系统()效率最大,最大可提高14%.

The characteristics of a vehicle diesel engine exhaust gas under various operating conditions were studied experimentally and a set of organic Rankine cycle （ORC）was designed. The effects of four kinds of pure fluids, four kinds of azeotropic mixtures and four kinds of zeotropic mixtures on the performance of ORC-engine combined system under various operating conditions were compared and analyzed by simulation. Results show that, with the increase of engine speed and accelerator opening, the net power outputs of the ORC system for these twelve organic working fluids and the exergy destruction rates of system and its components as well gradually increase, but the growth rates are different. The av- eraged net power output of the ORC system for R504 under various operating conditions of diesel engine gives its maximum value of 7.29 kW, which is 18% higher than R227ea. The ORC system thermal effi- ciency of mixed-refrigerants is generally higher than that of pure working fluids. The exergy efficiency of ORC system for zeotropic mixture increases by 14% than that of pure mixtures and R415B gives the maximum value.