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| Numerical Study on Pressure Oscillation Suppression of Low-Speed Marine Engine with In-Cyinder Direct Injection of Natural Gas |
| DOI：10.13949/j.cnki.nrjgc.2019.06.009 |
| Key Words:low-speed marine engine dual fuel pressure oscillation Miller cycle injection strategy CFD |
| Author Name | Affiliation | | YUAN Chengwei,LIU Bo,JIANG Xiaoxiao,ZHOU Lei,CHEN Rui,WEI Haiqiao | 1.State Key Laboratory of Engines， Tianjin University， Tianjin 300072, China
2.China Shipbuilding Power Engineering Institute Co., Ltd., Shanghai 201206, China；
3.Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough LE11 3TU, United Kingdom |
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| Abstract:Based on the computational fluid dynamics(CFD) software(CONVERGE), the simulation model of a large low-speed two-stroke marine engine in which pilot diesel and natural gas are injected directly in cylinder was established. Validated by the experimental data from the literature, the model was then applied to studying the suppression effect of the Miller cycle and natural gas two-stage injection strategy on the pressure oscillation in high pressure direct injection mode. The calculation results indicated that when the exhaust valve was closed later, the overall combustion pressure was lower, both the combustion phase and the moment of severe pressure oscillation were delayed. The intensity of pressure oscillation was reduced with smaller delay of exhaust valve closing, while it was increased instead with an excessive delay. This was primarily attributed to the competitive relation between in-cylinder thermodynamic state and auto-ignition characteristics of fuel. Adjusting the pre-injection quantity of natural gas would reduce the formation of premixed combustible mixture before combustion, thus reducing the proportion of premixed combustion in the combustion phase, which could effectively suppress pressure oscillation, but could also reduce the output power and increase the fuel consumption. Compared with the pre-injection quantity, varying injection interval has less effect on the pressure oscillation, but the excessive injection interval would affect the combustion phase, resulting in considerable power loss. A reasonable injection strategy can ensure the power output while suppressing intense pressure oscillation. |
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