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The field of diesel combustion research is producing numerous reports on studies of premixed combustion, which promises simultaneous reduction of both NOx and soot, in order to meet increasingly stringent regulations on harmful emissions from automobiles. However, although premixed combustion can simultaneously reduce both NOx and soot, certain issues have been pointed out, including the fact that it emits greater quantities of unburned HC and CO gases and the fact that it limits the operating range. Furthermore, this combustion method sets the ignition delay longer with the aim of promoting the mixing of fuel and air. This raises issues with the product due to the combustion instability and sensitivity to the uneven fuel properties that are found on the market, the capability of the engine response under transient conditions, the deterioration in combustion noise, and so on.

Formula One engines, which are the pursuit of the ultimate in performance, tend to be comparatively vulnerable to durability issues. These engines sometimes run under a state of unstable combustion as compensation for improved fuel economy. To cope with these issues, there have been strong demands in the racing field for a technology that will allow constant monitoring and prompt action to be carried out on system malfunctions and failures, as well as unstable combustion. The research program described in this paper deals with an onboard technology for monitoring combustion under all the operational conditions using ionic current measurement. The technology will possibly be applied to engine management and car-to-pit communications via telemetering. The scope of the control it offers includes; detection of misfire and hesitation, detection and management of detonation, and management of lean-burn combustion.

For reduction of NOx and soot emission with conventional diesel diffusion combustion, the authors focused on enhancement of the rate of injection (hereafter referred to as RoI) to improve air availability, thus enhancing the fuel distribution and atomization. In order to increase opening ramp of the RoI (hereafter referred to as fast injection rate), a hydraulic circuit was improved and nozzle geometries were optimized to make the greatest use of the advantages of the hydraulic circuit. Two different common rail injectors were prepared for this research. One is a mass production-type injector with piezo actuator that achieved the EURO-V exhaust gas emission standards, and the other is a prototype injector equipped with the new hydraulic circuit. The nozzle needle of the prototype injector is directly actuated by high-pressure fuel from common rail to improve the RoI.

The ignition delay and combustion characteristics of hydrogen jets in an argon-oxygen atmosphere were investigated to provide fundamental data for operating an argon-circulated hydrogen internal combustion engine. Experiments were conducted in a constant-volume combustion vessel to study the effects of ambient temperature, ambient pressure, oxygen concentration and injection pressure on a pre-burning system. The hydrogen-jet penetration and flame were also investigated based on high-speed shadowgraph images. The experimental results indicated that the ignition delay (τ) increases as the ambient temperature (Ti) decreases, similar to the results obtained in an air atmosphere. The heat-release rate results also exhibited similar trends.