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Currently, even the small diesel engines are required to reduce CO2 emissions toward carbon-neutral society. One of the methods to realize this would be to use alternative fuels. Therefore, this research focuses on a liquid which is called MCH (Methylcyclohexane), it is expected as one of the "hydrogen carriers" that can transport hydrogen from foreign country efficiently. MCH is produced overseas by adding hydrogen to the toluene, and the hydrogen is extracted after transport to the destination. However, there is significant energy loss in extracting hydrogen process from MCH [1]. Therefore, it would be more hydrogen efficient use through MCH as fuel for the small diesel engines directly, rather than for power generation by extracting hydrogen, since it does not have that significant energy loss of MCH blended fuel in this research.

In a general-purpose small SI engine, it is required to reduce fuel consumption under the operating conditions of repeated start and stop. In other words, the energy distribution during engine start is an important indicator of 0 rpm until idling speed. The SI engine needs to be driven by the motor at startup, and its electrical energy must be minimized. However, the internal parts of the engine need to accelerate during startup, and its electrical energy is affected by both friction and moment of inertia with the internal parts of engine. The objective of this experimental research are two points. First, it is to determine the friction mean effective pressure (FMEP) under idling speed of the engine. It is important for the finding of the minimum demanded energy in startup to investigate the friction loss of each engine part. Second, it is to find the minimum demand for energy from 0 rpm until idling speed.

The supercharged spark ignition engine with direct fuel supply system in cylinder (SI engine) has a problem on abnormal combustion at low engine speed. It is called the LSPI (Low Speed Pre-Ignition)[1]. This research focuses on one of the source of abnormal combustion which is the autoignition of lubricating oil from piston crown in cylinder, here especially, frequency of autoignition in cylinder[2,3,4]. In this experiment, the test engine operates without spark ignition as motoring operation. The advantage of this method is to avoid the effect of gasoline dilution[5,6]. Namely, it is able to reveal the essence of abnormal combustion experimentally. The 2 kinds of lubricating oil are tested. The measured data show that the frequency of autoignition in this research is 1/10 of that of lubricating oil scattering from piston crown. The abnormal combustion occurs the frequency of 1 time in each 10000 cycles approximately. The special behavior of the LSPI has been measured.

The spark ignition engine with supercharger which is supplied the fuel directly in cylinder (SI engine) has a phenomenon of abnormal combustion as called Low Speed Pre-Ignition (LSPI). It has been reported that the LSPI would be related with lubricating oil and the ingredients of fuel and oil additives [1] [2]. The mechanism of LSPI does not clear sufficiently, especially, relation ignition source of LSPI with the lubricating oil additives and the fuel concentration in lubricating oil. This research focuses on the source of LSPI which is autoignition of a lubricating oil droplet in cylinder. The effect of oil additives as Zn, Mo, Mg, Ca and concentration of fuel on autoignition of a lubricating oil droplet has been investigated. This research has been tried to evaluate the degree of autoignition fundamentally by using of electric furnace which has been heated an oil droplet.

In recent years, the supercharged spark ignition engine (SI engine) is spread out in the field of passenger vehicle. However, it has a problem of abnormal combustion which is called Low Speed Pre-ignition (LSPI). It is cleared gradually that the character of lubricating oil effects on LSPI. The lubricating oil which has a tolerance for LSPI has been introduced already in the market nowadays. However, cause and mechanism of LSPI occurrence does not clear sufficiently. In previous conference SETC 2018, it was reported that the peculiar behavior of LSPI corresponded with behavior of lubricating oil from piston crown [1, 2, 3]. This paper focuses on frequency of lubricating oil scattering from piston crown. The behavior of lubricating oil from piston crown has four steps as follows, firstly, lubricating oil goes up along with piston side toward piston crown. Secondly, lubricating oil which reaches piston crown continues to accumulate against reciprocating motion.

The supercharged spark ignition engine (SI engine) has a problem of abnormal combustion. It is called Low Speed Pre-ignition (LSPI). The lubricating oil which has a tolerance for LSPI has been introduced already in automobile market nowadays. However, cause and mechanism of LSPI does not clear sufficiently. It has been reported that the peculiar behavior of LSPI corresponded with behavior of lubricating oil from piston crown [1, 2]. This paper focuses on effect of fuel ingredients on autoignition of a lubricating oil droplet about LSPI. On the ignition source point of view, it is important to clear the mechanism of a lubricating oil droplet autoignition in cylinder. This paper will be tried to clear its mechanism fundamentally by using of electric furnace which is heated an oil droplet. As a result, the activation energy E is found for quantitative evaluation of ignition sauce of LSPI.

It is expected for emulsified fuel to improve performance(1) of Diesel engine as thermal efficiency and emissions. The advantage of emulsified fuel is to use secondary atomization. The secondary atomization occurs, because of difference of boiling point between fuel and water. The water content strongly influence on timing of secondary atomization. However, water content is determined empirically as ever. In previous report(2)(3), it has been reported an engineering evaluation of emulsified fuel to determine optimal water content. Namely, an emulsified fuel droplet is adopted Weibull pots as a statistical evaluation. The experimental data show optimal water content is extremely difference between diesel fuel and neat bio fuel. This paper focuses on the cause of this difference of optimal water content. About this point in this paper, the remarkable parameter is kinematic viscosity and ingredients in fuel.

The emulsified fuel means that it is mixed fuel with water and stabilized by surfactant. The difference of boiling points between fuel and water occur the secondary atomization during heating process. The water content strongly influence on the timing of secondary atomization(1). However, the water content is determined empirically. It means that it is the doubtful of compatibility fuel and a combustor. Then the emulsified fuel is needed the engineering evaluation (not empirically) to take advantage of sure secondary atomization. This research focuses on the timing and behavior of secondary atomization with an emulsified fuel droplet and the proposal of engineering evaluation. Moreover, we propose novel test method without the suspending wire to avoid heat transfer from itself. Namely, the novel point is heating process by floating in the high temperature silicone oil. This method can reveal the atomization behavior of a fuel droplet similar to the spray combustion.

The supercharged spark ignition engine has a problem of abnormal combustion at low speed and high load operating condition. This paper focuses on the sauce and mechanism of the abnormal combustion, namely, the behavior of lubricating oil droplets in cylinder, ring crevice, piston crown and ring gap. The experimental approach and the numerical analysis have been carried out. The two experimental approaches namely direct photography by high speed camera and measurement of scattering oil quantity at low speed condition have been tried. The photographs which is in engine operation show, 1st The oil droplets from ring crevice scatter every reciprocating motion and the diameter of oil droplets is between 0.10mm and 0.30mm. 2nd The oil droplets from piston crown has three steps as follows, firstly, the lubricating oil which reaches piston crown continues to accumulate, secondly, the accumulated lubricating oil scatters by the reciprocating motion.

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 effect of oil distribution on journal bearing and piston friction and temperature was analyzed in a high-speed (CART) race engine, in order to reduce friction and improve reliability by optimizing the oil flow. Oil flow was measured with hot-wire sensors installed in actual engine oil feed lines, and piston temperatures were measured by thermistors using the electromagnetic induction method. The measurements were performed under firing conditions at engine speeds exceeding 15,000 rpm. Using the measurements, a well-balanced lubrication system specification was realized.

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.