This work describes the inherent restrictions of natural gas engines regarding poor flame propagation velocity and poor lean-burn capability. A systematic research analysis was performed to explore the combustion behavior, performance benefits, and emissions changes with varying degrees of hydrogen enrichment. Experimental validation was performed using a six-cylinder Spark Ignition natural gas engine with varying levels of hydrogen enrichment (between 0% and 30%). Experimental validation included systematic changes in engine speed, load conditions, and equivalence ratios. The results clearly identified 20% hydrogen enrichment as optimal. Compared with natural gas operation, with 20% hydrogen enrichment, an 8.6% improvement in BTE efficiency, 29% reduction in combustion duration, and 45% reduction in cycle-to-cycle variations were achieved. Carbon dioxide emissions were found to reduce by 18.5%, largely aided by the substitution effect and efficiency gains. Sizable reductions in emissions of carbon monoxide (36%) and unburned hydrocarbons (42%) were also observed. An increase in nitrogen oxide emissions due to combustion at stoichiometric conditions with enriched mixes was effectively managed with proper operation at a lean ratio of 1.35. This ensured no increase in emissions while maintaining the achieved efficiency gains.
Wan Huang (Fri,) studied this question.
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