采用含氧燃料和EGR同时降低直喷式柴油机碳烟和NO_x排放的试验研究

Simultaneous Reductions of Smoke and NO_x Emission from Light Duty DI Diesel Engine with Oxygenate Fuel and EGR

在一台TY1100轻型直喷式柴油机上,研究了碳酸二甲酯(DMC)作为含氧燃料添加剂对柴油机烟度和性能的影响。结果表明,在发动机燃油和燃烧系统不作变动的条件下,随着DMC在柴油中添加比例的增加,排气烟度逐步下降,热效率提高。当添加比例在10%～15%时,烟度降低40%～50%,热效率增加了6 9%,发动机功率基本不变。添加碳酸二甲酯并采用EGR可以同时降低碳烟和NOx。研究表明,柴油中添加15%DMC,在12%左右的EGR下,与原机比较,烟度降低了35%,NOx排放降低了33%。混合燃料的放热规律与纯柴油相比差异不大,但预混燃烧量增加,扩散燃烧速率快,发动机最高燃烧压力、温度和压力升高率偏高。

The paper carries out experimental studies on a TY1100 light duty DI diesel engine to investigate the effects of dimethyl carbonate (DMC) as an oxygenate additive in diesel on engine smoke and performances. Experimental results show that smoke emission decreases, thermal efficiency increases with increasing in DMC proportion in diesel fuel without modifications on fuel injection and combustion system of the engine. When the proportion of DMC in the blend fuel is 10%-15%, smoke emission is reduced by 40%-50%, thermal efficiency increases by 6.9% with less penalty on engine power output. For both DMC and EGR (exhaust gas recirculation) adopted on the engine, simultaneous reductions in smoke and NOx can be realized. Smoke emissions of the engine are reduced by 35% and NOx, reduced by 33%, as the proportion of DMC in the blend is 15% and EGR ratio is approximately 12%. The peak pressure and rate of pressure-rise of the engine with DMC in diesel is slightly higher than those of the original diesel engine due to longer ignition delay and larger amount of premixing combustion of blend fuel. The amount of diffusion combustion is smaller and the diffusion combustion velocity is faster and all of those plus higher oxygen contents in blend fuel result in lower smoke emission and higher thermal efficiency for 15% DMC operation.