当量比天然气发动机氨排放特性研究

Research on Ammonia Emission from Equivalent Ratio Natural Gas Engine

采用傅里叶变换红外线光谱仪研究了当量比天然气发动机的NH 3排放,重点研究了不同工况下三元催化器(three-way catalyst,TWC)前的NO x、CO、CH 4排放特性和TWC后的NH 3排放特性。结果表明:当量比天然气发动机原始排气中无NH 3排放,发动机原始排气经过TWC后的催化反应才是当量比天然气发动机NH 3排放的根本原因;当原机CO和CH 4保持稳定,提高NO x浓度可一定程度抑制NH 3的产生;外特性下较高的废气再循环率可通过降低原机NO x排放,提高CO和CH 4的生成促进NH 3的产生;在负荷加载过程中,加载速度通过影响原机CO和CH 4排放进而影响NH 3排放,急速的加载过程能促进NH 3的产生;对于具备燃料自适应性的天然气发动机,燃料成分的差异对发动机动力性和气态污染物排放无影响;当TWC入口温度处于催化器正常工作温度范围时,较低的排气温度对NH 3的产生有促进作用。

The emission of ammonia from an equivalent ratio natural gas engine was studied by using Fourier transform infrared spectrometer.The emissions of NO x,CO and CH 4 at the upstream of the three-way catalyst(TWC)and the emission of ammonia at the downstream of the TWC in different operating conditions were analyzed.The results show that there is no ammonia emission in the original exhaust gas from the equivalent ratio natural gas engine.The catalytic reaction of engine exhaust gas in the TWC is the real reason of the ammonia emission.When the concentration of original CO and CH 4 remains stable,higher NO x concentration can restrain the ammonia emission.Higher EGR rate at full load can promote the ammonia emission by reducing the NO x emissions and increasing the CO and CH 4 emissions.Different engine loading speeds can result in different amounts of ammonia emission by affecting the original CO and CH 4 emissions,and higher loading speed can promote the production of ammonia.Difference in fuel composition has no effect on the power and gaseous emissions of the natural gas engine if it has a self-adaptability for fuel.When the TWC inlet temperature is in the range of normal operating temperature of the catalyst,a lower temperature will promote the ammonia emission.