基于一台主动预燃室甲醇射流点火发动机，利用CONVERGE仿真软件建立仿真平台，在原有预燃室结构的基础上，将预燃室喉部截面积沿着轴线方向进行缩小或扩大，将预燃室结构分为喉部渐缩型（P1）、正常结构（P2）和喉部渐扩型（P3），对在不同预燃室喉部结构下的火焰射流和发动机燃烧特性等进行了研究。研究结果表明，3种结构的混合气均在喉部呈现出了明显的浓度梯度变化，其中喉部渐扩型预燃室由于速度梯度小更利于扩散，混合气在预燃室内分布更加均匀。而渐缩型的预燃室结构设计燃烧约束作用更强，射流方向更集中，预燃室和主燃室压差最大，从而火焰传播速度更快，射流能量更高，进一步优化了主燃室混合气燃烧，使得主燃室峰值缸内压力相较于P2型，P3型预燃室分别增大了0.129 MPa和0.912 MPa，峰值放热率显著提升，燃烧相位提前。

Based on an active pre-chamber methanol jet ignition engine, a simulation platform was developed using CONVERGE software.Building upon the original pre-chamber geometry, the cross-sectional area of throat  was modified along the axial direction to create three distinct configurations: a gradually constricting throat (P1), a conventional uniform throat (P2) and a gradually expanding throat (P3). The flame jet dynamics and engine combustion characteristics were systematically studied across these different throat geometries. The results show that the gradually expanding throat promotes more uniform reactant distribution within the pre-chambe due to its lower velocity gradient, thereby enchancing mixture homogeneity-although all three configurations exhibit a pronounced concentration gradient at the throat region. In contrast, the gradually constricting throat design imposes stronger combustion confinement and produces a more focused jet with a higher momentum discharge, resulting from the largest pressure difference between the pre-chamber and the main combustion chamber. Consequently, this configuration acheieves faster flame propagation and greater jet kinetic energy, which further enhances turbulent mixing and combustion efficiently in the main combustion chamber. As a result, the peak cylinder pressure increases by 0.129 MPa and 0.912 MPa compared to the P2 and P3 designs respectively, while the peak heat release rate significantly increases and the combustion phase advances.