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To clarify the detailed structure of high pressure fuel spray, 2-D sectional images of non-evaporating fuel sprays in a high pressure vessel were observed by using the laser light sheet of a copper vapor laser. By this system, many sectional and continuous photographs of the same spray were obtained, and were very effective for the detailed observation of the spray inner structure and its developing process. The spray inner structure was very complicated, and its fuel density distribution was very heterogeneous. And for its developing process, the spray advances straight immediately after injected, then meanders, and deforms into a branch-like structure. Advancing downstream, these branches distribute complicatedly and heterogeneously with low density droplets. The heterogeneity is owing to these branches. And, the developing process is divided into four regions. Further, the effects of some parameters on this process were investigated.

The characteristics of diesel combustion with high pressure fuel injection were investigated, using a naturally aspirated single cylinder engine and a high pressure injection equipment which can produce over 250 MPa injection pressure. Observation and analysis of combustion were performed using a high speed shadowgraph technique, with different injection pressures. In the case of high injection pressure in combination with smaller nozzle hole diameter, generation of soot in the combustion field is hardly recognized. Also by increasing injection pressure, ignition points tend to shift to the downstream of spray. Analysis of flame motion and turbulence intensity in the combustion field was performed using high speed direct photographs and image analysis technique by tracing flame luminosity distribution time history. By increasing injection pressure, an increase of turbulence intensity at the early stage of diffusion burning was observed.

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.

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.