回热布雷顿空气循环回收内燃机废气余热的模拟

Modeling of the Regenerated Brayton Air Cycle for IC Engine Exhaust Energy Recovery

为回收内燃机废气余热,基于回热布雷顿空气循环原理设计了一套底循环系统.针对不同的循环压力、空气流量、环境温度和内燃机排气温度,采用数值迭代的方法,对底循环传热过程和热力循环过程进行耦合计算,分析了底循环参数、排气参数和环境温度对废气余热回收效率的影响.结果表明:回热器的植入虽然回收了部分涡轮排气余热,但却抑制了换热器传热量;随着工质流量增加,回热器传热量先增后减,换热器传热量单调递增,回收效率先增后减;随着循环压力增加,回热器传热量单调递减,换热器传热量在中小流量范围递增,回收效率先增后减.排气温度越高、环境温度越低,回收效率越高.在排气温度为755,℃、环境温度为10,℃时,最大废气能量回收效率为7.2%,较标准布雷顿循环有一定提高.

To recover the IC engine exhaust gas energy,a bottom cycle system based on the regenerated Brayton air cycle was proposed.Heat transfer and thermodynamic processes of bottom cycle were calculated at different air pressures,air mass flow rates,ambient temperatures and exhaust gas temperatures by numerical method.The effects of bottom cycle parameter,exhaust parameter and ambient temperature on exhaust energy recovery efficiency were analyzed.Results show that part of turbine exhaust energy is recovered by the regenerator,but the heat transfer amount of heat exchanger is changed.With the increase of working medium flow rate,heat transfer amount of regenerator first increases and then decreases.Heat transfer amount of heat exchanger is increased.Exhaust energy recovery efficiency first increases and then decreases.With the increase of cycle pressure,heat transfer amount of regenerator is decreased.Heat transfer amount of heat exchanger increases in the low and medium flow rate range.Exhaust energy recovery efficiency first increases and then decreases.Higher exhaust temperature and lower ambient temperature give higher exhaust energy recovery efficiency.At the exhaust temperature of 755,℃ and ambient temperature of 10,℃,the maximum energy recovery efficiency is 7.2%,which is higher than that of the standard Brayton air cycle.