气体燃料船用主机工作过程三维数值模拟

摘要

For spark ignition gas-fuelled marine engines, in order to realize high efficiency lean combustion, there is a requirement to take the measures of“fuel/air ratio divisional controlling and turbulence stirring” to ensure reliable ignition and fast flame propagation. The combustion system of a gas-fuelled marine engine was designed. The working process of the engine was numerically simulated and analyzed by 3-D CFD. The flow field variation, fuel-air mixture formation, ignition and flame propagation processes in the cylinder were investigated, and the fuel enrichment strate-gies in pre-chamber were analyzed. The research provides initial conditions for the design of the combustion system and enrichment injection timing. The results indicate that, at the time of spark ignition, the mixture with a fuel/air e-quivalence ratio of 1.05 is formed in the pre-chamber, which is beneficial for stable ignition and rapid flame propaga-tion. After ignition, the flame jets are injected from the orifices of the pre-chamber and propagate rapidly in the main chamber. The main combustion process is finished within 50°CA.%为了实现高效稀燃，纯气体燃料船用主机需要采取预混合气的“分区控制、湍流激扰”来保证可靠点火和快速火焰传播。设计了某型号气体燃料船用主机的燃烧系统。应用三维CFD软件对其工作过程进行了数值模拟分析，研究了缸内流场变化、燃料-空气混合过程、点火和火焰传播过程，分析了预燃室内燃料加策略。研究为主机的燃烧系统设计和加浓喷射策略设计提供了初始数据支撑。研究结果表明：在点火时刻，主机预燃室内形成了当量比为1．05的稍浓混合气，有利于稳定点火和火焰快速传播；点火后，经由预燃室喷孔喷出的引燃火焰在主燃室内迅速扩展，在50° CA内即完成主燃烧。