Characterization of Spark Ignition Energy Transfer at Different Phases Using Pressure-Rise Calorimetry

The paper presents novel studies on the electrical-to-thermal energy deposition to gas at different phases of a spark. The experiments utilized a 10.9 milliliter custom-built spark calorimeter. The energy transfer efficiencies across spark phases—breakdown+arc, and glow are quantified, emphasizing their importances in ensuring robust ignition. An AC capacitive ignition system was considered in the experiments. The spark plugs used in the experiments were of dual-nickel standard J-gap design of a fixed electrode gap. Test results show the breakdown+arc phases are highly efficient in converting electrical to thermal energy, crucial for ignition. The glow phase, offering control flexibility, is found to be less effective in energy transfer from spark to gas. In addition, a maximum threshold for both glow current and duration is found. Exceeding the threshold reduces the net energy deposition to the gas, indicating an increase in thermal energy losses, primarily to the spark plug electrodes. Furthermore, a positive relationship between gas pressure and glow phase efficiency is established. The energy transfer to the gas during the glow phase is found to improve with the increase in gas pressure. Based on the findings, an optimal ignition control strategy is proposed for both biogas and hydrogen fueled spark ignited internal combustion engines (SI-ICEs). It aims to maximize energy transfer to gas and reduce heat losses to spark plug electrodes. Using this approach may extend spark plug life in biogas engines and lower the risk of pre-ignition from overheated spark plug electrodes in hydrogen engines.