利用动力涡轮回收利用汽车柴油机的排气余热

Waste Heat Recovery from Automotive Diesel Exhaust Via Power Turbine

对在车用增压柴油机增压涡轮后串联动力涡轮以回收利用柴油机排气余热进行了数值仿真研究。计算分析了动力涡轮直径大小对余热回收的影响,以及动力涡轮对柴油机本身性能和增压涡轮的影响。结果表明,动力涡轮的大小对增压柴油机系统影响较大,动力涡轮的选型应使动力涡轮在最大效率点运行时,柴油机和动力涡轮总输出功率最大;动力涡轮转速随动力涡轮直径的增大而降低,选用较大的动力涡轮有利于为其匹配传动装置。串联耦合动力涡轮之后,在柴油机高速时可提高系统总输出功率,降低有效燃油消耗率(BSFC),但在柴油机低速时会使系统性能恶化。建议使用低速旁通装置来限定动力涡轮仅在柴油机的高速区投入运行,以避免低速时柴油机和增压涡轮性能下降,高速时回收利用柴油机排气余热,达到节能的目的。

This paper presents the simulation study on waste heat recovery of turbocharged auto- motive diesel. A downstream power turbine has been coupled to the turbocharger for the purposes to recover waste heat energy. The influence of the power turbine on the system and the subsystem were analyzed in this study. The results show that the diameter of a power turbine has significant influence on diesel engine. The compounded power turbine ensures that whole system has maximum output power when it works at maximum efficiency. When the diameter of the power turbine gets bigger, the speed of the power turbine shaft reduces effectively. Furthermore, within high speed region, the turbo - compound system achieved more output power and fewer BSFC, but the performance gets deteriorated when the diesel engine run at low speed. Thus, a bypass device is suggested to use at low diesel speed to guarantee lowspeed behavior as well as to improve high -speed behavior so as to achieve the purpose of energy saving.