基于轻型柴油车的柴油机氧化催化器入口温度升温特性及策略研究

选取了高、中、低负荷的3个典型工况,研究了进气节流及喷油策略对柴油机缸内燃烧过程、排放性、经济性及柴油机催化氧化器(diesel oxidation catalyst,DOC)入口温度的影响,得到全工况区域的DOC入口温度的升温策略。试验结果表明:随进气节流阀开度减小,进气流量降低,压缩压力下降,燃烧始点滞后,最高燃烧压力下降,循环指示功降低;HC排放得到抑制,其他排放恶化;DOC入口温度得到有效提升,负荷越小,温升效果越显著。喷油规律耦合进气节流发现,主喷提前角的推迟使得滞燃期缩短、后燃加重,DOC入口温度小幅度提升;近后喷油量增加可提高DOC入口温度,推迟近后喷,DOC入口温度先增大后降低,存在最佳的近后喷时刻。依据样机全工况排温分布特征,提出了不同工况区域DOC入口温度升温控制策略。

Research on Inlet Temperature Rise Characteristics of Diesel Oxidation Catalyst and its Strategy for Light-Duty Diesel Vehicles

Three typical operating conditions of high, medium and low loads were selected to experimentally investigate the effects of intake throttle and fuel injection strategies on the combustion process, emissions, fuel economy and diesel oxidation catalyst(DOC) inlet temperature of a light-duty diesel engine, obtaining a heating strategy of the DOC inlet temperature at all operating conditions. The results showed that the intake air flow declined with the decrease of the opening of the intake throttle valve, which had a significant effect on the in-cylinder working process: decreased compression pressure, delayed combustion start timing, reduced maximum combustion pressure and decreased cyclic indicated work. HC emission was suppressed and other emissions were deteriorated. The DOC inlet temperature was effectively increased, and the lighter the load, the more significant the temperature rise. A test of fuel injection pattern coupled with intake throttle was conducted. The test results show that with the delay of the main fuel injection timing, the ignition delay is shortened, the weight of the post combustion increases and the DOC inlet temperature rises slightly. The DOC inlet temperature is raised by increasing the fuel quantity of the close post-injection. The DOC inlet temperature rises first and then drops with retarding the close post-injection timing. There is an optimum close post-injection timing. According to the distribution of the engine exhaust temperature in the whole operation range, the strategy of controlling the DOC inlet temperature is proposed.