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Bio-ethanol can be produced from several type of biomass, and the CO2 emission of bio-ethanol is low compared with gasoline. Bio-ethanol is a high octane fuel, therefore, it has characteristics that allow it to burn at a high compression ratio condition. However, bio-ethanol is usually refined to be high purity ethanol (>99.5%). It requires much energy to refine; thus large-scale refinery plants are needed, increasing the cost of refining bio-ethanol. High purity ethanol (>99.5%) can be refined after fermentation and a distillation. If hydrous ethanol can be used as a fuel for engines, the distillation process can be simplified. As a result, the costs of refinement can be reduced. An innovated engine can be developed by using hydrous ethanol as the fuel because three highly efficient methods can be combined. First, exhaust heat can be recovered by the steam reforming of hydrous ethanol. Second, the reformed gas, which contains hydrogen, can be combusted under dilute conditions.

The internal combustion engines waste large amounts of heat energy, which account for 60% of the fuel energy. If this heat energy could be converted to the output power of engines, their thermal efficiency could be improved. The thermal efficiency of the Otto cycle increases as the compression ratio and the ratio of specific heat increase. If high octane number fuel is used in engines, their thermal efficiency could be improved. Moreover, thermal efficiency could be improved further if fuel could be combusted in dilute condition. Therefore, exhaust heat recovery, high compression combustion, and lean combustion are important methods of improving the thermal efficiency of SI engines. These three methods could be combined by using hydrous ethanol as fuel. Exhaust heat can be recovered by the steam reforming of hydrous ethanol. The reformed gas including hydrogen can be combusted in dilute condition. In addition, it is cooled by directly injecting hydrous ethanol into the engine.

Hydrogen produced from regenerative sources has the potential to be a sustainable substitute for fossil fuels. A hydrogen internal combustion engine has good combustion characteristics, such as higher flame propagation velocity, shorter quenching distance, and higher thermal conductivity compared with hydrocarbon fuel. However, storing hydrogen is problematic since the energy density is low. Hydrogen can be chemically stored as a hydrocarbon fuel. In particular, an organic hydride can easily generate hydrogen through use of a catalyst. Additionally, it has an advantage in hydrogen transportation due to its liquid form at room temperature and pressure. We examined the application of an organic hydride in a spark ignition (SI) engine. We used methylcyclohexane (MCH) as an organic hydride from which hydrogen and toluene (TOL) can be reformed. First, the theoretical thermal efficiency was examined when hydrogen and TOL were supplied to an SI engine.

In this study, the possibility of real-time HCCI control in a multi-cylinder gasoline engine was examined. Specifically, we applied a multivariate analysis based on an experimental design of quality engineering, and picked out several engine parameters which influence gasoline HCCI combustion stability. We clarified the characteristics of engine parameters in a gasoline HCCI operation area and propose the control concept: The internal EGR control is applied to multi-cylinder control by using the variable valve system, and air-fuel mixture control is applied to each-cylinder injection control while keeping the mixture homogeneous. Combustion conditions and engine out A/F need to be detected and fed back individually for each cylinder. With the proposed concept, it is possible to construct a real-time HCCI control system in a multi-cylinder gasoline engine.

This paper describes a combustion stability control using fuel injection control for a gasoline homogeneous charge compression ignition (HCCI) engine. First, using a single-cylinder engine we examined the influence that fuel injection and air/fuel mixture had on HCCI engine auto-ignition and combustion. This was achieved by visualization experiment of in-cylinder air/fuel mixture with fuel injection as a parameter. Next, the effect of the fuel injection control was evaluated by using a 4-cylinder HCCI engine. We proposed the following concept for a gasoline HCCI combustion control: internal-EGR (I-EGR) is applied to either internal EGR control of each-cylinder or a multi-cylinder control scheme using a variable valve event and timing system, and the fuel injection is applied to each cylinder control while keeping the mixture homogeneous.