Mitigating Hydrogen Internal Combustion Engine Losses and the Flow on Benefits - The paragraphs follow the requested content in the guidelines Prof Harry Watson School of Engineering, University of Melbourne. ABSTRACT Evidence suggests that the hydrogen ICE is not much different from a dedicated natural gas engine or even gasoline engines. Therefore, as green hydrogen becomes available the lower cost and lower carbon footprint of the conventional light duty vehicle derived system, compared with the fuel cell, can be beneficial in the transition to fully green transport. The purpose is to review the problems of the hydrogen vehicle based on many decades of hydrogen engine and vehicle development which began with a world record holding car exhibited at the FISITA X1X Congress. The issues begin with the hugely different properties of the fuel compared with all others. Combustion-wise, problems of backfire, surface ignition, flame speed, flammability limits, thermal conductivity and more that lead to different approaches to engine design detail from the conventional SI engine. Moreover, appropriate hybridisation of the H2ICE, as with the fuel cell, enables significant gains in efficiency already highlighted by our long-time research into the always lean burn gasoline engine, now evidenced by F1 engine technology. The review of hydrogen’s unique properties leads to answers as to why hydrogen engines respond differently to increased compression ratio as evidenced in several of our engine studies with an optimum around 11:1. Mitigation of abnormal combustion is described including the influence of surface coatings, surface finish and deposits, Quantitative evidence of the mechanisms are addressed and results presented. Moreover, ultimate solutions are proposed through detailed energy analysis of the whole of engine losses. This includes the trade off in losses through entirely quality (air-fuel ratio) governing against partial throttling (Lambda 6 and leaner is possible) and measures to compensate for the slow flame speeds that determine the technology applied for best efficiency. These trade-offs guide the described optimum path in the engine efficiency map to compliment the availability of battery energy storage. The results have diesel like similarities but without the limitations of particulate and NOx emission control compromises. Throughout the paper we draw on evidence from our extensive experiments, validated modelling and detailed analysis, and award-winning publications in this field as well as relevant complimentary literature. Even so, hydrogen engine design is still work in progress to specify an engine that can be integrated into a Renault Ecolab type concept that innovatively reduces complexity and drive train losses. This paper will rely heavily on the insight provided by our previous research, not only benefitting from the long-term perspective but adding the findings from the most recent unpublished research from the Centre in Mechanical Engineering at the University of Melbourne. It appears that the hydrogen ICE can be a complimentary, cheaper and have a lower carbon footprint way to the first use of green (and blue) hydrogen. The solution and mitigation of some of the hydrogen specific fuel delivery and combustion related issues, or strategies for their solution are described with potential peak efficiencies within a few percent of those of the fuel cell, with much less sensitivity to hydrogen contamination and therefore durability. At this critical time in history, options which build on traditional automotive engineering with much lower embodied CO2 than BEVs can provide the earliest possible transition to a renewable energy world that is so vital to implement. (564 words)

Prof. Harry Watson, Part Time Prof, University of Melbourne