柴油机富氧进气燃用乳化柴油的循环变动与燃烧特性

Cycle-by-cycle Variations of a DI Engine Fueled with Water Emulsion Diesel and Oxygen Enriched Intake Air

在直喷柴油机上采用进气增氧(氧气在进气中的体积分数为21%、23%、25%和30%)技术,对燃用不同掺水比乳化柴油(水在乳化柴油中的体积分数为0%、10%、20%和30%)的循环变动及燃烧特性进行研究;实验工况为发动机经济转速、中等负荷,采集20个连续循环,取最大爆发压力值,计算循环变动率。研究结果表明:在纯柴油条件下,随氧含量的增加,缸内最大爆发压力增加,循环变动率降低,燃烧始点提前;在使用乳化柴油时,着火点随水乳化率的增加而推后,但其依然遵循随进气O2体积分数增加而提前的规律;含水率达30%时,着火延迟加大,燃烧组织恶化,循环变动加大。

The combustion characteristic and cycle-to-cycle variations of a DI engine using oxygen-enriched intake air（the volume fraction of oxygen as follows：21%,23%,25% and 30%） and water-diesel fuel emulsions（the amount of water was 0%,10%,20%and 30% by volume） were investigated.In-cylinder pressures of 20 combustion cycles and maximum pressures under economic speed and medium load operation were recorded.Consequently,cycle-to-cycle variations of maximum pressures and combustion characteristic were analyzed.The results reveal that,under the conditions of pure diesel,with the increase of oxygen concentration,the maximum cylinder pressures increase,and the cyclic variability of the maximum cylinder pressures and the ignition timing decrease.Using water emulsion diesel,with the increase of volume fraction of water,the ignition timing increases,but it still decreases with the oxygen concentration increasing.When the fraction of water is over 30%,the ignition delay increases dramatically,the in-cylinder burning deteriorates,and the variations of maximum pressure grow.