Performance of a Small Spark-Ignited Internal Combustion Engine on Producer Gas from Rice Hulls

Abstract

The performance of a small single cylinder spark ignited internal combustion engine is detailed for operation on producer gas generated from a static bed rice hull gasifier. The development of batch and alternating-batch reactor systems employing moving reaction fronts in stationary fuel beds has provided a means of generating a fuel gas of reasonably stable quality influenced only slightly by the position of the reaction front in the bed and by the speed of the engine and the concomitant change in air flowrate resulting from the varying displacement rate of the engine. Performance of stock (unmodified) L-head engines of 206 cc displacement and 6.2 compression ratio has been tested extensively on both gasoline and producer gas fuels at speeds up to 3600 rpm. Derating is substantial but adequately modeled by charge energy derating and derating of mechanical efficiency based on correlations of friction power with engine speed. Maximum brake power at optimal spark advance when fueled with producer gas is 40 to 45% that of the engine fueled with gasoline, and of the same order as the relative air capacity of the engine. Indicated thermal efficiency of the engine is nearly the same for both fuels, if not marginally elevated for producer gas. Preliminary data on the effect of increased compression ratio shows an anticipated elevation in brake power up to 7.3 compression ratio, but a decline in brake power beyond this to 8.2 compression ratio. The cause of the decline beyond 7.3 compression ratio is not yet known, but believed to be related to the shape of the combustion chamber as modified to reduce the clearance volume of the cylinder.