Spark Ignition System for Alternative Fuels – Robust Ignition, Minimized Spark Plug Wear and Combustion Process Diagnostics

Spark ignited internal combustion engines (SI-ICE) running on alternative and/or renewable fuels are important to reduce the emission of greenhouse gases, motivated by its ability to efficiently make use of renewable fuels with low cetane numbers which are not suitable for diesel-like combustion. Examples of such fuels are natural gas (CNG, LNG), electro-methane, biogas, hydrogen, methanol, ethanol, and ammonia. The property of such fuels may vary significantly, both with respect to heat release rate and ignitability. Also, electro-methane and/or hydrogen can be used as blend-in fuel in bio and natural gas, which may increase the fuel mixture variations. SI-ICE engines can be made flexible, such that they can adapt to the property of the fuel in current use, improving drivability and fuel economy, hereby enhancing the great potential of a renewable fuels suitable for SI-ICE. The paper reviews the challenges and design trade-off’s when designing an ignition system for such SI-ICE, specifically when ion-sense based combustion diagnostics is included. Requirements on the ignition system for different engine designs and fuel properties is discussed with a focus on ignitability, and diagnostics of spark plug wear, and combustion process diagnostics using ion sense. Finally, recent advances in the development of ignitions systems and ion sense at SEM, is presented.