重型柴油机进气预混甲醇实现国Ⅳ排放标准研究

Realizing National Phase Ⅳ Emission Standard of Heavy-duty Diesel Engine by Using Premixed Methanol / Diesel Dual Fuel

在一台6缸重型柴油机上,进行了进气预混甲醇/柴油双燃料(PMDDF)燃烧、结合氧化催化转换器(DOC)和微粒氧化催化转换器(POC)实现国Ⅳ排放标准的研究。同时还对进气预混甲醇对发动机燃烧过程以及燃油经济性的影响进行了研究。结果表明:在发动机动力性保持不变的情况下,按照排放法规的检测方法,采用PMDDF模式,仅使用DOC+POC可以使原机的排放从国Ⅲ提升到国Ⅳ水平,且综合当量燃油消耗率相比原机基本不变。研究中还发现,随着甲醇替代率的增加,PMDDF模式的着火滞燃期延长,燃烧持续期缩短。在大负荷时,PMDDF模式的当量比油耗低于原机,而小负荷时略高于原机。

Premixed methanol diesel dual fuel（ PMDDF） is a combustion mode in which methanol is injected from the intake port and then ignited by the direct injected diesel in the cylinder. Many studies have shown that PMDDF mode has the potential to reduce NOxand PM emissions simultaneously. In this study,investigation on realizing national phase Ⅳ emission standard by using PMDDF combustion mode coupling with diesel oxidation catalyst（ DOC） and particulate oxidation catalyst（ POC） was carried out on a 6-cylinder heavy-duty diesel engine. The effects of premixed methanol on engine combustion process and fuel economy were also investigated. The experimental results showed that with the engine power keeping unchanged,the emission level of the engine was improved from national phase Ⅲ to Ⅳ by using PMDDF combustion mode and the simple aftertreatment DOC ＋ POC. And the specific fuel consumption almost remained unchanged. This technology provided a new route for the realization of national phase Ⅳemission standard. In addition,it was also found that the ignition delay of PMDDF combustion mode was prolonged and the combustion duration was shortened with the increase of premixed methanol ratio. At high engine load,the brake specific fuel consumption of PMDDF combustion mode was lower than that of baseline engine,but it was slightly higher at low engine load. Therefore,the premixed methanol ratio can be a little higher at high engine load but can not be very high at low engine load.