As indicated in the table, the displaced volume of the engine is unchanged when the conversion for natural gas is made; however, the clearance height is reduced to increase .the compression ratio.
(a) Estimate the ratio of the volumetric efficiency of the engine operating on natural gas to the volumetric efficiency with gasoline, at wide-open throttle and 2000 revlmin. Both fuels are in the gaseous state in the intake manifold.
(b) Estimate the ratio of the maximum indicated power of the engine operating with natural gas to the maximum power of the gasoline engine
(c) Estimate the ratio of the gross indicated fuel conversion efficiency of the natural gas engine to that of the gasoline engine, at the part-load conditions given.
(d) Explain whether the NO, CO, and hydrocarbon specific emissions (grams of pollutant per how, per unit indicated power) at part-load conditions of the natural gas engine will be higher, about the same, or lower than the NO, CO, and HC emissions from the gasoline engine. Explain briefly why.
You can assume that the fuel-air cycle results derived for isooctane-air mixtures are also appropriate for methane-air mixtures.