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In recent years, trans-esterified vegetable oils have been widely applied to diesel engine in order to suppress greenhouse gas emissions. However, “neat” vegetable oils are expected to be directly used to resolve some difficulties faced in their use, such high viscosity and slightly high fuel consumption. In this study neat linseed oil has been investigated as a neat vegetable oil. It was found to show higher fuel consumption than diesel fuel, however at the same time it showed lower indicated fuel consumption than diesel fuel. These results suggest some increase in engine friction loss in a neat biofuel diesel engine. Studies have been extensively investigated the difference in friction loss and a newly developed “improved deceleration method” has been applied.

In order to achieve a sustainable society, vegetable oil derived from solar energy is a major topic of interest. Vegetable oils are can potentially be utilized as fuel in applications such as engines, gas turbines, furnaces, boilers and steam power plants. In this paper, rapeseed oil as a fuel for diesel engine was studied. There are seven refinement processes that improve the quality of the oil because the rapeseed oil is mainly produced for food. Rapeseed oil is produced from the raw material through compression, solvent extraction, degumming, deoxidation, bleaching, deodorization and a final-refinement process. However, all of these refinement processes are not necessary if the oil is to be used for diesel fuel. The performance of the engines operated by the tested fuels, which were extracted at the end of each of the seven refinement stages, was investigated. The major findings of this study are as follows.

Investigation has been carried out for the effect of the idling stop for a short time when stopping by the traffic signal. The amount of the fuel consumption by the idling stop is formulated by the following equations. Where Fs Saved fuel consumption (cc), I Fuel consumption during idling (cc/s), Tis Period during the idling stop (s), S2 Additional fuel consumption by restarting the engine (cc), S3 Energy consumption at the battery for starting, in fuel consumption equivalence (cc), Nis Frequency of idling stop.

The “idling stop” of the vehicle, which is defined as no rotation of the engine when it stops, theoretically brings to reduce the fuel consumption (i.e. carbon dioxide) and the exhaust emissions. However, the idling stop practically has weak points as follows: 1. When the engine is restarted, much fuel is consumed. 2. When the engine is restarted, much the exhaust emissions are discharged. 3. While various electric devices work, the load of the battery is high. 4. The deterioration of the lubricating oil proceeds due to repeating start and stop. In order to overcome the above weak points the authors propose the new system called IISS.

This study focuses on the time history of the concentration of unburnt HC in an exhaust system of spark ignition engine. A mathematical model which can estimate gas temperature, and degree of oxidation in an exhaust system for given engine specifications and operating conditions is developed. This model is confirmed by experiment in which instantaneous HC concentrations are measured by using a fast sampling valve, and measurement of HC emissions in an exhaust pipe of a methane fueled engine.

The art of supplementary-fueling diesel engines by feeding certain gaseous fuel is well-known technique for improving the engine's smoke limited output. The thermal efficiency of these engines strongly depend on the combustion limit of the gaseous fuel around the gasoil spray. In this paper the lean limit of the gaseous fuel around the gasoil sprays in the diesel engine is measured by OFT technique. The measured combustion limit agrees with the estimated value from the numerical model developed by the authors.

In both spark ignition engines and diesel engines, exhaust gas recirculation system (EGR) is well known as an effective technique to reduce nitrogen oxides emissions. However, wear of piston rings and cylinder liners are sharply increased by EGR. It is widely considered that sulfur oxides contained in exhaust gas strongly relate to wear. In order to clarify the pure effect of sulfur oxides on piston ring wear, we experimented by adding sulfur dioxide positively to induction air. Furthermore, we compared the measured amount of wear with the amount of sulfur dioxide absorbed into a lubricating oil film, which was estimated by a numerical model. Consequently, it is confirmed that sulfur dioxide absorbed into a lubricating oil film played an important role on piston ring wear.

In this paper, to reveal behavior of SO2 gas which is recirculated from the exhaust gas on wear of piston rings and cylinder liner in diesel engines, a numerical model to estimate the amount of SO2 in oil layer on the cylinder wall is developed. The experimental fact that increase of wear of the piston rings and the cylinder liner due to EGR can be explained by the increase of the calculated SO2 concentration in the oil layer.

Unreacted fuel in ring crevice volumes is a significant source of hydrocarbon emissions from spark ignition engines. If the ring crevice is designed with a wider clearance into which the flame will propagate, the unreacted fuel can be reduced. In this paper, the conditions of flame propagation into the ring crevice are investigated by using ionization probes imbedded in the moving piston of a four-stroke spark ignition engine. It is found that the flame propagates into the ring crevice if the quenching distance when the flame reaches the crevice is narrower than the piston top land clearance.

A dual fueled diesel engine system with diesel fuel and reformed methanol has been investigated. Methanol can be reformed to reformed methanol (hydrogen 67% + carbon monoxide 33%) over suitable catalyst. The reformed methanol contains 20% more energy than methanol. Fundamental data of an electric heated reformer, performance of the dual fueled diesel engine to which hydrogen and carbon monoxide fed from gas bombs as a preliminary experiment, and then performance of the diesel engine with an onboard reformer were tested. In consequence, the feed of the reformed methanol improves the diesel engine performance.