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Experiments have been conducted to investigate the inhibitory effect of the catalytic reaction of methane and the formation of formaldehyde in the presence of NO. With precious metal catalysts, the presence of NO showed an inhibitory effect on the methane oxidation and caused the formation of formaldehyde. In the absence of oxygen, however, formaldehyde was not produced in the catalytic reaction of methane and NO. Maximum formation of formaldehyde was about 0.6 % of NO with the Pt and Rh series catalysts. N2O formation is similar to the formaldehyde formation from the catalytic oxidation of methane in the presence of NO.

Ignition and combustion of methanol in a spark-assisted methanol diesel engine were studied for the purpose of developing such an engine that is practical for actual vehicles. It became clear through investigations on combustion of methanol in a spark-assisted methanol diesel engine that methanol combustion proceeds mainly by flame propagation. Based on this finding, effects of such parameters as the injection direction, ignition position, ignition energy, compression ratio, injection timing and ignition timing were studied to obtain optimal conditions for methanol combustion. It was found through such studies that it is effective to form the mixture upstream of the spark, plug relative to the swirling direction and increase the inductive component of the ignition energy to achieve a high ignition stability.

An automobile dissociated methanol gas fueled spark ignition engine along with a cold starter and an exhaust dissociator for the engine was developed. The engine was tested for its cold startability, performance, fuel consumption and exhaust emissions to assess its applicability to automobiles. The cold starter reforms the rich alcohol fuel mixture into dissociated methanol gas through a bubbling process at a cold start and during warmup. This starter allows to start the engine at ambient temperatures as low as −15°C, while resulting in reduced undesirable emissions. The exhaust dissociator dissociates methanol into hydrogen and carbon monoxide utilizing the waste exhaust heat. The engine fueld with liquid and dissociated methanol had a thermal efficiency better by about 20 percent than that fueled with gasoline, and gave exhaust emission levels similar to those of gasoline engines. It is clear that the engine system suggest a high potential for the use of methanol fuel in the future.

The purification performances of some kinds of catalytic converters ( Pt, Rh, Pd, Pd/Rh, Pd/Pt, Pt/Rh/Pd, Pt_Pd and Pd_Cu) were investigated to select suitable catalytic converters for natural gas fueled automotive engines. Pd series catalysts showed better performance among the noble metal catalysts for oxidation of unburned methane in exhaust gas. The optimum loading of Pd catalyst is the range of 1.6 to 3.2 g/L. The dual-bed catalyst, Pt_Pd, consisting of a Pt catalyst in the front and a Pd catalyst in the rear, showed a performance better than Pd series catalysts. When aged to an accumulated running distance of 50000 miles, the catalytic activity of the Rh catalysts is much reduced, but those of Pd and Pt catalyst are affected little by aging. The aged Pd/Rh catalyst showed superior emissions' purification performance at the stoichiometric condition, but poor at lean mixture conditions.

A dissociated methanol fueled passenger car has been developed which shows improved transient driving and exhaust emission performance. In order to improve the transient performance, a mountable engine control unit, a new exhaust dissociator and a dissociated methanol flow control valve were developed among others and examined. The new exhaust dissociator has a extended heat transfer surface area and double injector to improve transient response and heat exchange efficiency. The dissociated methanol flow control valve which is controlled by intake manifold pressure works as a compensator for delayed dissociated methanol at transient driving. The high thermal efficiency and low exhaust emission level was observed for the transient driving as well as steady state driving.