Exergy analysis of hydrogen-fueled spark ignition engine based on numerical investigations

Abstract

Hydrogen fuelled IC engines (H2ICEs) have been considered as one of the most promising systems for pollution free transportations and their performance and combustion merits have been extensively discussed in the literature. However, studies related to these discussions have largely been linked to first-law analysis. On other hand, second-law of thermodynamics coupled with first-law, also known as exergy analysis, can give better insight into the engine performances. Bearing it in mind, this work presents second-law quantification of hydrogen engine processes and sub-processes, which helps to understand its true potential to deliver the output and simultaneously estimates various losses. This study quantifies different process inefficiencies in terms of irreversibilities thereby identifying the gaps to be addressed for further improvements. A computational fluid dynamics model has been prepared to simulate hydrogen-fueled spark-ignition engine (H2SIE) operations and second-law equations have been coupled to ascertain different exergy terms. Present study shows that combustion process is the biggest source of irreversibility in IC engines. It has also been found that the level of irreversibility for a hydrogen-operated engine is substantially lesser as compared to that with gasoline engine under identical ranges of operating conditions. Combustion irreversibilities for H2SIE and gasoline engine were found to be 15% and 23.6% of the total input fuel exergy respectively. Moreover, significant increase in second-law efficiency for H2SIE as 44.4% compared to 36.8% that for gasoline engines has been found. Another important conclusion from this work includes exergy distribution for H2SIE, which is considerably diverse from gasoline engine operation. It indicates that optimization and improvements of different H2SIE processes require specific attentions; nevertheless, show much better ability to deliver.