Comparative energy, exergy, exergoeconomic, and exergoenvironmental economic analyses of hydrogen enrichment via port injection in a propane-operated SI engine under partial load conditions

This study comparatively investigates the energy, exergy, exergoeconomic, exergoenviroeconomic, and environmental impact analyses of a hydrogen-enriched propane spark-ignition (SI) engine. While propane fuel is used as the primary fuel in the SI engine, hydrogen enrichment is achieved via the port injection method at different flow rates. The experiments are conducted at a constant engine speed under lean combustion conditions (from λ = 1.0 to λ = 1.4) under partial load conditions. The aim of this study is to comparatively examine the low performance of propane fuel, which is commercially used in many countries, under lean combustion conditions, with respect to performance, exergy efficiency, power cost, environmental costs, and sustainability as a result of hydrogen enrichment. The results indicate that the highest exergy efficiency of 23.64% is obtained at λ = 1.4 with a hydrogen flow rate of 21 L/min, and that the increase in exergy efficiency exceeds 90% compared to propane combustion under the same conditions. In addition, at λ = 1.4 and a hydrogen flow rate of 21 L/min, the lowest power cost of 86.48 $/GJ is recorded, corresponding to a 51.1% reduction in power cost compared to propane. The results of the exergy-based enviroeconomic analysis show that hydrogen reduces the environmental and enviroeconomic impacts under stoichiometric conditions, and although environmental impacts increase with mixture leaning, the obtained results are still lower than the environmental impact of propane under stoichiometric conditions.