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As alternative fuel, natural gas holds a dominant position with widely distributed resources in the world and a low CO2 emission rate compared with the other fuels for automobile. Natural gas should be used in liquid phase (LNG) especially in automobile use due to considerations of energy density. Research and development was conducted for a practical LNG vehicle equipped with a LNG engine and LNG supply and engine control systems. The LNG engine system was given a high compression ratio, manifold gas injection, and spark ignition for the effective use of natural gas. For the components of LNG supply system, LNG tank, vaporizer, LNG control valve and gas injector were developed. The LNG tank and the LNG control valves were given super insulation constructions to prevent gas boil off. LNG was vaporized using heat from the radiator. The gas injector is controlled by a solenoid coil for optimum fuel supply. A computer using fuzzy logic was developed in part for the engine control system.

The poor cold startability is one of the problems in using methanol as the fuel for Otto-type engines. A method for solving this problem is to mix some additives for cold start improvement. The effects of various additives and their concentrations on the improvement of cold startability were studied, and the following results were obtained: (1) The cold startability was studied using actual engines in relation to the preliminary results of cold mixture formation obtained by using an equilibrium air evaporation apparatus. It was found from this study that the cold startability of actual engines shows a high correlation with the excess air ratio of fuel mixture observed using the equilibrium air evaporation apparatus.

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.

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 authors developed a method to measure the air-fuel ratio at local points within the combustion chamber. The primary point is to obtain the pre-combustion air-fuel ratio of the mixture from the HC (vaporized fuel) and O2 concentrations. This procedure which consists of three parts, gas sampling, gas transport and gas analysis, renders it possible to perform direct quantitative HC analysis of samples. This method is carried out by either of two techniques: multi-cycle sampling (MCS) and single cycle sampling (SCS), and the average air-fuel ratio of many engine-cycles and the single engine-cycle were obtained respectively.