Search Results

The effect of combustion time and combustion variability on performance and emissions was investigated with a single cylinder CFR spark ignition engine using gaseous fuel (propane). A system was developed which allowed the collection of the products of combustion of individual engine cycles. This system consisted of an alectrically operated gas sampling valve drawing gas from immediately behind the exhaust valve, and an electronic discriminator/valve driver system. Engine cycles were selected for sampling according to the time for flame propagation to a point in the combustion chamber diametrically opposite the spark site, this being a strong indicator of total combustion time. Flame arrival was detected with an ionisation probe. A Gas Chromatograph and a modified Chemiluminiscent NOX analyser were used for gas analysis. For any particular engine operating point, flame propagation time varies randomly from cycle to cycle (cycle by cycle variability).