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| Study on Lean Combustion Characteristics of Gasoline Direct Injection Engines with Jet Ignition and Intake Water Injection Technologies |
| DOI：10.13949/j.cnki.nrjgc.2024.02.002 |
| Key Words:gasoline engine lean combustion pre-chamber jet ignition water injection |
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| Abstract:Based on a four-cylinder turbocharged gasoline engine， a pre-chamber and an intake water injection system were added. Experimental tests were conducted at the optimal fuel consumption conditions （2 500 r/min， brake mean effective pressure（BMEP）=0.8~1.2 MPa） to analyze the characteristics of the lean combustion of a gasoline engine， as well as the effects of jet ignition and intake water injection on lean combustion performance. The results show that lean combustion can increase the brake thermal efficiency（BTE） from 39.5% for stoichiometric combustion to around 42.5%. However， combustion stability and total hydrocarbon（THC） emissions deteriorate when the excess air ratio exceeds 1.4. By adopting jet ignition technology， the excess air ratio for stable combustion can be extended to above 1.7， and the BTE can increase to over 43%. The combustion duration can be reduced by a maximum of 37.6%， and the cycle of variation（COV） does not exceed 1.3%. Furthermore， with the addition of intake water injection， the knocking suppression effect is significant for loads with BMEP above 1.1 MPa. When the water injection pulse width reaches 4 ms， the knock-limited CA50 can be advanced to approximately 8° after top dead center， while achieving a maximum BTE of over 44% and COV within 3%. However， for loads with BMEP below 1.1 MPa， since knocking is not serious， water injection instead reduces the combustion rate and thermal efficiency， while worsening combustion stability and THC emissions. |
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