满足美国EPA 3排放法规的188F汽油机机内净化研究

Study on internal-purify technology of 188F gasoline engine to meet American emission standard EPA 3

为满足通用小型汽油机美国EPA 3排放法规的要求,对188F汽油机运用气道稳流试验、缸压采集试验、累计放热率计算等方法,研究气道流通系数、混合气浓度和点火提前角对汽油机CO、HC和NO_x排放的影响,分析排放特性、缸内燃烧压力、燃烧放热率、缸内温度的变化规律。结果表明:改进气道结构后,最大气门升程时进气道和排气道的流通能力分别增大39.5%和34.2%,气缸进气量增加,功率增大0.73 kW、燃油消耗率下降8.1 g/(kW·h),排放降低;点火提前角不变,改变过量空气系数φ_a大小,各工况下HC+NO_x存在一个最低值,研究得出低排放的理想混合气浓度特性,即标定工况下采用浓混合气(φ_a为0.835)以满足美国EPA 3排放法规,且过量空气系数随负荷的减小逐渐增大;其他参数不变,推迟点火提前角可以有效抑制NO_x、HC排放,但功率降低、燃油消耗率增加,综合考虑选取点火提前角为18°CA。188F汽油机经250 h劣化试验的CO和HC+NO_x排放结果为312.5 g/(kW·h)和7.1 g/(kW·h),低于美国EPA 3的610 g/(kW·h)和8.0 g/(kW·h)的限值,达到排放法规要求。研究工作为低排放通用小型汽油机研发提供了可供参考的技术路线。

To meet the American emissions standard E P A 3, the small utility gasoline engine 188F was taken to reserach the effect of flow coefficient, mixture concentration and ignition advanced timing on CO , HC and NOz emissions. T he emissions characteristics, in-cylinder pressure, heat release rate and combustion temperature were analyzed by steady flow test, test of in-cylinder pressure collection,calculation of cumulative heat release rate and so o n. Results showed that the intake flow coefficient of and exhaust port was increased by 39. 5 % and 34. 2% respectively at maximum valve lift due to improving the structure of the port; the fresh charge was increased and power was increased by 0. 73 kW ; the fuel consumption was decreased by 8. 1 g/ （ k W · h ） and emissions were reduced. B y varying the excess air ratio, there was a minimum value of H C ＋ N O x emission with the same ignition advanced timing, the ideal low emissions mixture concentration characteristics was defined. Under rated condition the rich mixture was delivered （ excess air ratio was 0. 835） for meeting the American emission regulations E P A 3 and the excess air ratio reduced with the decrease of load. B y delaying the ignition advanced timing while other parameters maintained, the NOz and HC emission could be reduced effectively, but the power decreased and fuel consumption increased,so the optimal ignition advanced timing was 18 °C A . Through 250 hours of degradation test,CO and HC ＋ N 〇x emission results were 312. 5 g/ （ kW · h ） and 7. 1 g/ （ kW · h ） respectively and was lower than 610 g/（ kW ·h ） and 8. 0 g/ （ kW ·h ） of American E P A 3 gasoline engine emissions limits. Th e 188F gasoline engine could meet the American E P A 3 emissions standard. The researching work provided referential technical route for development of low emission small utility gasoline engine.