防爆柴油机废气再循环冷却系统研究

Research on exhaust gas recirculation cooling system for explosion-proof diesel engine

针对煤矿井下矿用防爆柴油机的排放污染问题,根据MT 990-2006《矿用防爆柴油机通用技术条件》对防爆柴油机表面温度不超过150℃的要求,对防爆废气再循环(EGR)冷却系统进行设计,通过对防爆文丘里管原理的分析、防爆电动水泵的选型及冷却系统散热量的计算,设计了符合要求的EGR冷却系统。并按照标准对防爆柴油机及EGR冷却系统进行台架试验,研究了防爆柴油机EGR温度对尾气排放中NOx、HC、CO和烟度等成分的影响,试验结果表明:在额定转速下随着EGR冷却系统温度的降低,NOx排放降低,CO排放增加,HC排放增加,烟度降低;在同一EGR温度下负荷降低,NOx、CO、HC、烟度排放均降低;随着EGR温度的降低,NOx排放降幅最大为7.4%,降幅最小为3.3%,CO增幅最大为100%,增幅最小为0,HC排放增幅最大为20%,增幅最小为2.7%,烟度排放降幅最大为20%,降幅最小为0;确定了防爆柴油机工作时取得尾气排放综合性能最好状态下防爆EGR最佳冷却温度范围为70~100℃。

The explosion-proof EGR cooling system and the explosion-proof Venturi tube are designed according to the principles of heat transfer and hydrodynamics,and the pump is selected.Then the diesel engine is tested on the bench according to the standard,and the rules of NO_x,HC,CO and smoke varying with exhaust gas recirculation(EGR)temperature under different working conditions are studied.In view of the emission pollution problem of coal mine underground mine explosion-proof diesel engine,according to the requirements of MT 990-2006 "general technical conditions for mine explosion-proof diesel engine",the surface temperature of explosion-proof diesel engine should not exceed 150℃,the explosion-proof(EGR)cooling system is carried out.Through the analysis of the principle of explosion-proof venturi tube,the selection of explosion-proof electric water pump and the calculation of the heat dissipation of the cooling system,the EGR cooling system was designed to meet the requirements.Then the bench test of the explosion-proof diesel engine and the EGR cooling system were carried out according to the standard,and the effects of NO_x,HC,CO and smoke varying with EGR temperature under different working conditions are studied.The results show that with the decrease of EGR temperature at rated speed,NO_xemission decreases,CO emission increases,HC emission increases and smoke decreases;load decreases at the same EGR temperature,NO,CO,HC and smoke emission decreases.With the decrease of EGR temperature,NO_xemission decreases by 7.4%,3.3%,the CO increase is 100%,the minimum increase is 0,the HC emission increase is 20%,the minimum increase is 2.7%,and the smoke emission reduction is 20%,the minimum decrease is 0;It is determined that the optimal cooling performance range of the explosion-proof EGR is 70~100℃under the best condition of the exhaust gas emission when the explosion-proof diesel engine is working.