Examination of the Oil Combustion in a S.I. Hydrogen Engine

Carbon monoxide (CO), carbon dioxide (CO₂) and unburned hydrocarbon (UHC) are present in the exhaust gases of S.I. engines operated on pure hydrogen. These carbon-bearing species result from the oxidation of the lubricating oil and can be considered conveniently as natural tracers for indicating the lubricating oil consumption by combustion. Accordingly, such a novel approach can be employed to examine factors that affect engine oil consumption without the need to resort to more complex approaches. This contribution presents experimental results of oil combustion in a variable compression ratio single cylinder CFR engine when fueled with pure hydrogen established by determining the concentrations of CO and CO₂ in the exhaust gas. The effects of changes in key operating variables that include equivalence and compression ratios, spark timing and the onset of knock on oil combustion are examined. It is to be shown that the oil consumption rates increase with increasing equivalence ratio, and hence load, while the effect of changes in compression ratio is relatively weak for non-knocking operation. These rates increase suddenly and rapidly once knocking is encountered. The oil combustion rates also correlates well with changes in the average values of the combustion duration, overall quenching distance, and the calculated maximum averaged burned products temperature.