PERFORMANCE OF ANHYDROUS AMMONIA AS A SPARK IGNITION ENGINE FUEL

Ammonia can be used successfully as a spark ignition engine fuel and at presently existing compression ratios, if introduced as a vapor and if first partly dissociated to hydrogen and nitrogen. Under such circumstances little engine modification is necessary other than a means for flow control of the ammonia and adjustment of the spark timing. Maximum experimental power output for ammonia was 72 per cent of that for iso-octane. This result compares favorably with a theoretically predicted output, when adjusted for 5 per cent hydrogen dissociation, of 75 per cent. Specific fuel consumption using ammonia is increased by a factor of 2 over that of hydrocarbon when compared at peak power and 2-12 times when compared at maximum economy. Hydrogen concentration in the fuel feed is a critical factor for successful operation on ammonia as fuel. Minimum concentrations appear to be 4 to 5 per cent by weight at intermediate engine speeds of 1800 rpm. Engine performance rapidly falls if less than minimum concentrations of hydrogen are used. This seems to relate to the self-generating character of the ammonia decomposition during the compression and combustion processes. Performance factors such as are influenced by engine speed, spark timing and manifold pressure are not far different with ammonia than with hydrocarbons as long as minimum amounts of hydrogen are inducted as a part of the fuel flow.