摘要
在直喷柴油机上采用体积分数21%、22%、23%和24%的进气增氧技术,燃用纯柴油与30%水乳化柴油进行燃烧及排放试验.采用CFD软件与正庚烷简化模型耦合进行数值模拟.试验结果表明,燃用纯柴油时,随进气氧体积分数的增加,燃烧始点提前;在使用30%水乳化柴油时,着火延迟加大,但其依然遵循随掺入的氧体积分数增大着火时刻提前的规律,NO和烟度的排放低于燃用纯柴油的情况.模拟计算显示:CFD与动力学模型的耦合可以较为准确地预测富氧燃烧的缸内着火时刻及燃烧状况.分析上止点后2°,CA时刻燃烧室温度场切片可知,燃用30%水乳化柴油使缸内温度下降,即使掺入体积分数24%的O2,NO生成也低于燃用纯柴油、空气助燃的情况,实现富氧条件下相对于原机的低温燃烧,减少了污染物的排放.
The oxygen-enriched intake air technology was applied to a DI diesel engine （the volume fractions of oxy- gen are 21%, 22%, 23% and 24%）. The effects of pure diesel and 30% water emulsion diesel on combustion and emission was investigated. The same engine working condition was simulated by coupling multi-dimensional compu- tational fluid dynamics （CFD） code FIRE with n-heptane simplified chemical kinetics model. The experiment and simulation were both carried out under the maximum torque point of engine. The experimental result reveals that, under the condition of pure diesel, with the increase of oxygen concentration, the ignition timing decreases. With 30% water emulsion diesel, ignition delay increases, but it still decreases with the increase of oxygen concentration. The NO emission and smoke emission of the engine fueled with 30% water emulsion diesel were lower than those of the engine fueled with pure diesel. The simulation result shows that, the cylinder pressure field, other physical quan- tities and various combustion products in combustion chamber, can be accurately predicted by the coupling method. Analysis of combustion chamber impress-cuts of 2~ CA ATDC shows that, using 30% water emulsion diesel, combustion temperature decreases. Lower combustion temperature makes the NO emission lower than the original NO emission of the engine, even though the oxygen reaches 24% in intake air. Using 30% water emulsion diesel and 24% oxygen-enriched intake air can achieve low-temperature combustion under oxygen-rich conditions.
出处
《燃烧科学与技术》
EI
CAS
CSCD
北大核心
2012年第4期344-352,共9页
Journal of Combustion Science and Technology
基金
国家自然科学基金资助项目(50976077)
关键词
直喷柴油机
富氧进气
富氧燃烧
水乳化柴油
耦合计算
燃烧特性
DI diesel engine
oxygen-enriched intake air
oxygen-enriched combustion
water emulsion diesel
coupling computation
combustion characteristic
