Effect of Prechamber Design Parameters on Combustion Characteristics, Emission, and Performance of a Methanol Engine

Turbulent jet ignition (TJI) is an efficient ignition technology, while the effects of key design parameters on engine performance remain unclear. This study investigates the effects of throat diameter and nozzle number on combustion characteristics, emission, and performance of a methanol engine with TJI. Additionally, the effect of spark timings (STs) on the characteristics of the TJI methanol engine is analyzed. Experimental results show that the in-cylinder pressure decreases, and the ignition delay significantly increases as the throat diameter increases. The engine maintains excellent combustion characteristics and achieves the lowest HC emissions when the throat diameter is 4.5 mm. A prechamber with more nozzles benefits from distributed ignition, resulting in a slightly higher in-cylinder pressure and heat release rate. As the number of nozzles increases, NO _x emissions rise, while HC emissions first decrease and then slightly increase, reaching a minimum value when n = 4. Due to the advantage of multipoint ignition, TJI cases show lower sensitivity to spark timing and achieve the best brake thermal efficiency at ST = -21 °CA ATDC. For the same prechamber, advancing the spark timing can increase the peak in-cylinder pressure by up to 56.9%. Compared with spark ignition, TJI can significantly advance the combustion phase and increase in-cylinder pressure but results in higher emissions. The results can provide valuable experimental data to support prechamber design and offer a reference for improving the performance of methanol engines.