Experimental analysis of main/auxiliary spark plug interactions in a direct-injection aviation H₂ICE with redundancy-compliant ignition design

Amidst global aviation's commitment to carbon neutrality by 2050, this study pioneers experimental verification of a dual-spark-plug system in a 2.0L turbocharged direct-injection hydrogen internal combustion engine. To satisfy stringent aviation redundancy mandates under Federal Aviation Regulations Part 33 and Civil Aviation Regulations of China-33-R2, an auxiliary spark plug was integrated near the combustion chamber periphery alongside the original centrally positioned main spark plug. Comprehensive testing spanned propeller-load simulations from 1300 to 4800 rpm and idle conditions, evaluating individual and coordinated ignition modes. Results demonstrate that the auxiliary spark system alone delivers full power replication at 142.5 kW and 283.49 N m torque at 4800 rpm with earlier spark timing about 8° crank angle, enabling seamless redundancy during main spark failure. At speeds exceeding 4200 rpm, auxiliary spark operation reduces nitrogen oxides emissions by 11.5 % while simultaneously lowering unburned hydrogen emissions. For idle optimization, coordinated spark timing at 16° crank angle before top dead center achieves a peak brake thermal efficiency of 22.54 %, representing a 0.88 % improvement over auxiliary spark operation and 0.24 % over main spark operation. This strategy concurrently reduces coefficient of variation to 2.62 % cycle variation and slashes hydrogen emissions by up to 23.8 % compared to single-spark operation, resolving the trade-off between idle stability and emissions in lean-burn hydrogen internal combustion engines.