Pre-chamber spark-ignition (PCSI) is a leading advanced ignition concept for internal combustion engines with the potential to enable diesel-like efficiency in medium-duty/heavy-duty (MD/HD) natural gas (NG) engines. By leveraging distributed ignition sources from multiple turbulent jets, the PCSI technology can deliver extremely short combustion duration in ultra-lean mixtures and significantly improve the engine thermal efficiency. However, in the automotive industry there is a lack of adequate science base and predictive simulation tools required for commercial development of PCSI engines. In this study, Reynolds-Average Navier-Stokes simulations are carried out to describe the combustion process in lean-burn NG engines, focusing on the combustion modeling approach. Two combustion models, multi-zone well-stirred reactor (MZ-WSR) and G-equation, are used to simulate the combustion process in an MD NG engine equipped with a fueled-PCSI system for four operating conditions close to the lean operating limit. A skeletal chemical mechanism and a laminar flame speed tabulation are used to compute the combustion accurately. Simulation results are compared with experimental data regarding measured cylinder pressure, heat release rate, and combustion duration. By dividing the PCSI combustion process into four distinct phases, the difference between the two models’ results for each phase is analyzed in detail. The MZ-WSR model overestimates the combustion duration for early flame kernel growth in the pre-chamber due to the lack of a specific formulation to take turbulence-chemistry interaction into account. Despite the prolonged combustion duration and low pressure built-up inside the pre-chamber, the model matches the combustion rate in the main-chamber. In contrast, the G-equation model delivers good agreements for the pre-chamber combustion and turbulent jet-driven combustion processes. However, the model starts to underestimate the combustion rate in the main-chamber, especially under ultra-lean mixture conditions. Finally, improvements are needed for both models to simulate the later combustion stage that occurred in the near-wall regions.

室前火花点火（PCSI）是内燃机的一种先进的高级点火概念，具有在中型/重型（MD / HD）天然气（NG）发动机中实现类似柴油的效率的潜力。通过利用来自多个湍流喷嘴的分布式点火源，PCSI技术可以在超稀薄混合物中提供极短的燃烧持续时间，并显着提高发动机的热效率。但是，在汽车工业中，缺少用于PCSI引擎商业开发的足够的科学基础和预测性仿真工具。在这项研究中，进行了雷诺平均Navier-Stokes仿真来描述稀薄NG发动机的燃烧过程，重点是燃烧建模方法。两种燃烧模型，多区搅拌式反应堆（MZ-WSR）和G方程，用于模拟配备燃油PCSI系统的MD NG发动机在接近稀薄运行极限的四个工况下的燃烧过程。骨骼化学机理和层流火焰速度制表用于精确计算燃烧。将模拟结果与有关测得的气缸压力，放热率和燃烧持续时间的实验数据进行比较。通过将PCSI燃烧过程分为四个不同的阶段，详细分析了每个阶段两个模型的结果之间的差异。MZ-WSR模型高估了预燃室中早期火焰核生长的燃烧持续时间，这是因为缺少考虑湍流-化学相互作用的特定公式所致。尽管延长了燃烧持续时间，并且预燃室内部积聚了低压，该模型与主室中的燃烧速率匹配。相反，G方程模型为燃烧室前燃烧和湍流射流驱动的燃烧过程提供了良好的协议。但是，该模型开始低估了主腔室内的燃烧速率，尤其是在超稀薄混合气条件下。最后，两个模型都需要改进，以模拟在近壁区域发生的后期燃烧阶段。