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The paper presents novel studies on the impact of different ignition control parameters on combustion stability and spark plug wear. First, experimental results from a 32.4-liter biogas fueled large bore single cylinder spark ignition engine are discussed. Two different ignition systems were considered in the experiment: a DC inductive and an AC capacitive. The spark plugs used in the experiment were of dual-iridium standard J-gap design of different electrode gaps. Test results show the importance of different degrees of freedom to control a spark. A robust ignition is found to be achieved by using a very short spark duration, which in turn reduces total energy discharge at the gap. Further observations reveal that once a stable and self-propagating flame kernel is developed, it becomes independent of the spark energy further added to the gap. Finally, results from the spark plug wear tests using a pressurized rig chamber are discussed. It is found that an excessive spark energy discharge at the gap contributes to high erosion of spark plug electrodes, which is not desirable. However, spark energy is not the only factor affecting spark plug erosion. It is also the type of spark discharge (DC/AC) that governs the electrode wear over time. Therefore, the advantage of an AC spark discharge over a DC spark has been well established through the experimental results. The inherent property of an AC spark is found to be significantly slowing down electrode wear over time, hence increasing the service life of a spark plug.

The impact of different spark designs on the ignition and combustion stability is studied using a 13-liter CNG fueled heavy duty spark ignited engine to search for the “optimal” spark design. Experimental results show that robust ignition can be achieved using a significantly shorter spark duration and lower energy than expected. A capacitive discharge ignition (CDI) system enabled to separately control the available spark voltage, current and duration (FlexiSpark®CDI) was compared to a standard CDI system without spark control and an inductive discharge (IDI) ignition system. Typically, a robust ignition can be provided using only 5% of the spark duration and 17% of the spark energy compared to that required by an IDI system to accomplish an equivalent ignition and combustion stability. By applying control of the spark, a robust ignition can be provided which is optimized for the fuel, the engine design, the engine operating condition, and the condition of the spark plugs. This offers a potential to significantly reduce the spark-plug wear and the total cost of ownership without compromising engine performance.The results are especially interesting in the view of Hydrogen fueled SI-ICE, where the required available spark voltage is high, but the required spark energy is low. It is desirable to use a spark design with just enough voltage and power to initiate a sustainable combustion, but with minimal energy not to excessively wear and heat the spark plug electrodes to avoid pre-ignition.