重型柴油机低温起动及暖机过程的颗粒排放特性

Particle Emission Characteristics of Heavy Diesel Engine During Low-temperature Star-up and Warm-up

低温环境下重型柴油机起动过程碳烟颗粒排放较高,严重影响起动效率。柴油机的低温起动性能受冷却液和润滑油温度的影响,为揭示低温环境下柴油机起动过程的碳烟颗粒排放变化规律,通过单缸发动机台架试验,对起动和暖机过程不同初始水温油温条件下的缸内压力、碳烟烟度和颗粒物浓度排放进行测量。试验结果表明:发动机低温起动初期碳烟排放最高,随着起动和暖机过程中水温油温升高碳烟排放逐渐降低,聚集态颗粒数浓度降低,核态颗粒数浓度升高,总颗粒数浓度受核态颗粒主导而升高;低温起动时提高初始水温、油温,起动和暖机过程中碳烟排放降低,核态颗粒数浓度、粒径、表面积和质量均降低,聚集态颗粒数浓度降低,大尺寸聚集态颗粒增多使得颗粒表面积和质量升高;低温环境下提高加温锅的加热能力以升高初始水温油温,可降低起动过程的碳烟和颗粒数排放,有助于提高起动效率和减少环境污染。

The high soot particle emission during the start-up process of heavy diesel engine at low-temperature has a serious effect on the start-up efficiency.The start-up performance of diesel engine at low-temperature is influenced by the coolant and lubricating oil temperature.To reveal the soot particle emission characteristics of diesel engine during start-up process at low temperature,the in-cylinder pressures,and soot and particle emissions at different initial coolant and lubricating oil temperature conditions during start-up and warm-up are measured by single-cylinder engine bench test.The results show that the soot emission of the engine is the highest in the early stage of low-temperature start-up.With the increase of coolant and lubricating oil temperatures during warm-up,the soot emission gradually decreases,the number concentration of aggregated particles is reduced,the number concentration of nucleation mode particles is increased,and the total particle number concentration is dominated by nucleation mode particles.Increasing the initial coolant and lubricating oil temperatures under cold start-up condition reduces the soot emission during the start-up process,the number concentration,particle size,surface area and mass of nucleation mode particles decrease,the number concentration of aggregated particles decreases,and the particle surface area and mass are increased with the increase in large-sized aggregated particles.The soot and particle emissions during the start-up process can be reducedd by increasing the heating capacity of the heating pot at low temperature to increase the initial temperatures of coolant and lubricating oil,which improves the start-up efficiency and reduces environmental pollution.