增压稀燃天然气发动机排放特性

Emission Characteristic of Turbocharged Lean Burn CNG Engine

为了研究增压稀燃天然气发动机的排放特性,对发动机进行了空燃比和点火提前角调整试验、十三工况排放等试验,并在增加氧化型催化转化器后进行了相关试验,对试验结果进行研究分析,获得了天然气发动机的排放规律。结果表明：NMHC排放随空燃比增大先减少后增加,NOx排放随空燃比增大先增加后减少,在空燃比19～21左右达到最大值。NMHC比排放随转速升高略有降低,NOx排放随转速升高先减小后增加,发动机最低NOx排放点所对应的发动机转速为1600～1800 r/min。定MAP下,NMHC排放随点火提前角增大先降低后增加,NOx排放随点火提前角增大而增大。加I型氧化催化器后发动机NOx、CH4、CO、NMHC排放值分别减少了15%、97%、78%6、0%。试验结果表明,增压稀燃和氧化型催化转化器相结合是天然气发动机一种有效方案。

In order to study emission characteristic of turbocharged lean burn CNG engine, an experimental research was conducted to examine the influence of the air fuel ratio, ignition timing and the oxidation catalyst converter on the emission characteristic. The result shows that NOx emissions increase initially and then decrease, but NMHC emissions decrease initially and increase as the air fuel ratio increases. Additionally the NOx emissions decrease initially and then increase as the engine speed increases. The lowest NOx emission value occures for 1 600- 1 800 r/min. Under the constant manifold absolute pressure, with increase of ignition advanced angle, NMHC emissions decrease initially and then increase, NOx emissions increase. After installing the I type oxidation catalyst converter, NOx, CH4 , CO and NMHC emissions are reduced by 15 %, 97 %, 78 % and 60 % respectively. The result shows turbocharging lean burn in combination of oxidation catalyst converter is an effective technical way for CNG engine.