Analysis and optimization of energy conversion for an on-board methanol reforming engine with thermochemical recuperation

Methanol steam reforming (MSR) is a promising method to address the storage and safety issues of hydrogenfueled engines. This method can also significantly improve engine efficiency by recovering exhaust heat. Additionally, low temperature combustion technology can effectively mitigate the issue of excessively high NOx emissions in hydrogen internal combustion engines. However, research on the integration of low temperature combustion technology with methanol steam reforming is limited, and the design of reformers and strategies for methanol reforming remains underdeveloped. Therefore, a one-dimensional model of the methanol steam reforming engine system was established, and methanol reforming strategies were evaluated under varying engine loads. Further a multi-objective optimization of the reformer was conducted to balance system efficiency and economy. The results indicate that complete methanol reforming is unattainable at mid to high loads due to significant turbo work. A partial methanol reforming strategy, where part of the methanol is directly combusted in the cylinder and the rest is reformed to produce hydrogen, achieves the highest system efficiency. After multiobjective optimization of the reformer, this MSR engine yielded a 5.54% increase in average overall system efficiency under three loads, compared to not using thermochemical recuperation.