【作者】

Shinji Yasueda，Luigi Tozzi，Emmanuella Sotiropoulou

【摘要】

论文已在中国上海举行的2013年CIMAC大会上发表，论文的版权归CIMAC所有。The BMEP of gas engines has been increasing for the last two decades thanks to the advancement in technology allowing for the efficiency of the latest gas engines to surpass that of diesel engines in several categories. But at the same time, the stochastic occurrence of high firing pressure resulting from abnormal combustion can be seen more in many types of premixed gas engines having higher BMEP. This situation is worse in the Japanese market where the Methane Number of gaseous fuel is much lower than typical natural gas and has negatively affected the stable operation of the engines in service. Research conducted by the authors confirmed that this type of abnormal combustion is caused by the auto ignition of lubricating oil in the cylinder. Lubricating oil existing in the cylinder undergoes auto ignition before the intentional ignition from electrical spark or injection of pilot fuel takes place. This phenomenon increases not only the firing pressure due to the advanced combustion timing but also the cyclic variation of firing pressure from the multiple ignition points created by the presence of lubricating oil mist. The trend of developing higher BMEP gas engines will continue along with the increase in variation of the Methane Number due to the expansion of utilization of LNG all over the world. Under these circumstances, the abnormal combustion caused by lubricating oil could become one of the crucial hurdles for the development of future premixed gas engines. Therefore, autoignition of lubricating oil must be carefully considered in the optimization of engine parameters required for the development of higher BMEP engines from now on. Recent developments in numerical techniques and computational processing power are now permitting time-dependent, multi-dimensional computational fluid dynamic(CFD) calculations with reduced chemical kinetic mechanisms. Tools, such as the CONVERGE CFD code, enable to predict diffusion combustion as well as premixed combustion phenomena. Further advancements in combustion CFD modeling were achieved at Prometheus as a result of abundant research with combustion visualization, accurate surface temperature boundary conditions and appropriate turbulent models coupled to an in-depth knowledge of experimental combustion physics of gas engines. Prometheus' combustion CFD modeling technology, using the CONVERGE CFD code, is capable of high fidelity simulations of ultra lean, high BMEP gas engine combustion with either spark ignited or pilot ignition systems. Even sensitive physics like ignition by electrical spark and knock phenomena, near wall or end-gas, can be accurately predicted. This capability offers the advantage to design highly optimized natural gas engine components such as pistons, intake ports, precombustion chambers, fuel systems and ignition systems. With this simulation technology, the authors have developed a CFD combustion simulation that enables to predict the auto ignition of lubricating oil that takes place prior to the intentional ignition event. This is a very useful designing tool not only to investigate more about the mechanism of this abnormal combustion and countermeasures but also to make careful optimization of engine parameters to avoid auto ignition of lubricating oil. This paper aims at describing the fundamental physics of lubricating oil autoignition by comparing the experimental observations to the results obtained with an advanced combustion modeling technology and CFD code.

【会议名称】

第27届CIMAC会议

【会议地点】

上海

【下载次数】

3

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