Hydrogen as an additive to methane for spark ignition engine applications

It is shown that the performance of a gas fuelled spark ignition engine can be enhanced considerably when relatively small amounts of hydrogen are present with methane. This improvement in performance which is especially pronounced at operational equivalence ratios that are much leaner than the stoichiometric value, can be attributed largely to the faster and cleaner burning characteristics of hydrogen in comparison to methane. Through analytical simulation of engine performance, the addition of hydrogen is considered through its production in-situ on board the engine by electrolysis of water with the necessary energy supplied from engine power. It is shown that when the work energy required for the production of hydrogen by electrolysis is taken into account, the range of viable operation of such an engine is very narrow. This would render the whole concept of in situ hydrogen production through water electrolysis uneconomical in conjunction with engine operation, even though the presence of additional oxygen produced with the hydrogen tends, in principle, to improve engine performance beyond that observed with hydrogen addition.