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| Optical Diagnostics Study of Ammonia-Diesel Dual-Fuel Engine Combustion |
| DOI：10.13949/j.cnki.nrjgc.2024.03.001 |
| Key Words:ammonia replacement rate dual fuel injection strategy flame development internal combustion engine |
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| Abstract:In order to solve the problem of unstable combustion of ammonia fuel in engines， optical diagnosis research on combustion process of an ammonia-diesel dual-fuel engine was carried out to obtain combustion and flame development characteristics of ammonia-diesel induced ammonia， and the influence of ammonia-diesel dual-fuel on in-cylinder combustion and flame development characteristics at different ammonia replacement rates and different diesel injection times was studied. The results indicate that with increasing ammonia substitution rates， the peak cylinder pressure and heat release rate initially increase and then decrease. The combustion phase continuously shifts later， and the ignition delay and combustion duration prolong. Compared to a 40% ammonia substitution rate， the peak heat release rate decreases by 41.7% and 58.8% at 70% and 80% ammonia substitution rates， respectively. The flame intensity and flame area both decrease gradually with increasing ammonia substitution rates. When the ammonia replacement rate is 80%， the flame diffusion to the center of the combustion chamber slows down， and the peak flame area is 612.5 mm2， accounting for about 19% of the total area of the combustion chamber， indicating poor combustion performance. As the diesel injection timing is delayed， the peak cylinder pressure and heat release rate follow a similar trend， with the combustion phase shifting later. The combustion duration initially decreases and then increases， while flame luminosity and flame area show an initial increase followed by a decrease. At -25° direct injection timing， the peak cylinder pressure and heat release rate are 4.28 MPa and 115.4 J/（°）， respectively， exhibiting superior heat release performance compared to other timings. Compared to -20° direct injection timing， flame luminosity and flame area increase by 15% and 42.5%， respectively， indicating improved ignition efficiency in the combustion chamber center， with the smallest unburned region， demonstrating favorable ignition effects with ammonia. |
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