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| Influence of Ignition Strategy on Jet Combustion and Emissions of Natural Gas Direct Injection Engines |
| DOI：10.13949/j.cnki.nrjgc.2022.05.006 |
| Key Words:ignition position ignition distance high pressure direct injection natural gas combustion flame emission |
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| Abstract:The jet mixing， pilot combustion and emission generation processes of high pressure natural gas used on natural gas direct injection engines were studied based on the computational fluid dynamics（CFD） software CONVERGE. The effects of ignition mode and ignition distance on these basic processes were analyzed in detail. The results show that the high pressure direct injection natural gas jet can obviously promote the development and mixing process of pilot diesel spray， but the effect of pilot diesel injection on the development of natural gas jet is not obvious. In the center of high pressure direct injection natural gas jet flame， there is a flame recessed area with lower temperature and higher natural gas concentration. This flame recessed area is the main generation area of soot， and the high concentration area of soot is located in the middle and rear of the flame recessed area. Compared with the ignition mode， the ignition distance has a more obvious influence on the lift-off length， the flame recession length， NOx and soot emissions. As the ignition distance increases， the lift-off length and NOx emissions increase， and the flame recession length and soot emissions decrease. The ignition mode of injecting pilot diesel into natural gas jet has the highest peak heat release rate and the shortest combustion duration among the three ignition modes， and its NOx and soot emissions are the lowest while the methane escape amount is the highest. |
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