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Alcohol fuels that can be produced from cellulose continue to become more widely used in gasoline engines. This research investigated the application of alcohol to diesel engines with the aims of improving the combustion of diesel engines and of utilizing alternative fuels. Two methods were compared, a method in which alcohol is injected into the air intake system and a method in which alcohol is blended in advance into the diesel fuel. Alcohol is an oxygenated fuel and so the amount of soot that is emitted is small. Furthermore, blended fuels have characteristics that help promote mixture formation, which can be expected to reduce the amount of soot even more, such as a low cetane number, low viscosity, low surface tension, and a low boiling point. Ethanol has a strong moisture-absorption attribute and separates easily when mixed with diesel fuel. Therefore, 1-butanol was used since it possesses a strong hydrophobic attribute and does not separate easily.

Hydrogen can be produced from various renewable energy sources, therefore it is predicted that hydrogen could play a greater role in meeting society's energy needs in the mid- to long-term. Conventional hydrogen engines have some disadvantages: higher cooling loss results in low thermal efficiency and abnormal combustion (backfire, pre-ignition, higher burning velocity) limits high load operation. Direct injection is an effective solution to overcome these disadvantages, but combustion methods that enable both high efficiency and low NOx have yet to be studied in enough detail. In this research, high-efficiency and low-NOx hydrogen combustion was investigated using a prototype high-pressure hydrogen injector (maximum 30 MPa). Experiments were carried out with a 2.2-liter 4-cylinder diesel engine equipped with a centrally mounted hydrogen injector, a toroidal shape combustion chamber, and a spark plug in the glow plug position.

A new 2.0 ℓ DOHC 4-valve direct injection (DI) gasoline engine has been developed which features new technologies such as swirl intake ports to produce an optimum swirl in the cylinder by variable controlled swirl control valve, pistons with a concave combustion chamber, and high pressure fuel injection system to provide a fine fuel-air mixture cloud in the combustion chamber. These all help to control fuel-air mixture preparation and flame propagation under ultra lean, stratified combustion at partial loads. NOx emission is reduced by using an electrically controlled EGR system and an NOx storage-reduction catalyst. At higher loads, a homogeneous mixture is obtained with direct injection during the intake stroke. A seamless output torque transition between stratified charge and homogeneous charge condition is achieved by an electronic throttle control system.