Energy Flow Analysis and Modeling of Plasma-Enhanced Thermocatalytic Ammonia Reforming for On-Board Hydrogen Production

The plasma-enhanced thermocatalytic reforming system effectively reduces the high-temperature dependence of the single thermocatalytic mode, but its high energy consumption limits on-board use in ammonia engines. Building an energy flow analysis system to identify reforming losses or developing an engineering-level hydrogen production model to determine operational boundaries can accelerate the deployment of on-board plasma reforming. Nevertheless, there are currently insufficient research reports in these regards. In this study, a closely coupled reforming system was developed to enable systematic experimental investigation under low energy input conditions. Concurrently, a comprehensive energy flow analysis system was erected to delineate the variation law of the efficiency and precisely discriminate the influences of each effect under the closely coupled mode on the ammonia reforming process. Ultimately, based on the Temkin–Pyzhev rate formula, an engineering hydrogen production model with high predictive capability was developed. Overall, the closely coupled mode demonstrates superior reforming performance, particularly under low-temperature conditions. Specifically, it achieved an ammonia conversion rate of 19% at an operating temperature of 593 K and an input plasma power of 40 W. This is mainly ascribed to the fact that, in the low-temperature condition, the ammonia decomposition system is predominantly governed by both the chemical and thermal effects of plasma. Although the thermal catalytic effect regains the dominant position as the temperature rises, the positive effect by the introduction of plasma reveals its high potential to broaden the operational temperature boundary. The energy flow analysis indicates that the efficiency improves with the increase in space velocity, yet the overall efficiency is somewhat impacted due to the high energy consumption resulting from the introduction of plasma. Furthermore, the optimized Temkin–Pyzhev model demonstrates a high accuracy in predicting the ammonia reforming process, thereby providing a robust foundation for subsequent engine-integrated simulation studies.