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Blended fuels of turpentine oil and castor oil, palm oil, and sunflower oil have been used as alternative fuels in compression ignition, pre-combustion chamber CI engines. The effect of these blended fuels on engine performance, exhaust emissions, and combustion process have also been investigated. Here, the effect of higher injection valve opening pressures with blended fuels was investigated, and the behavior of the fuel spray at the higher injection valve opening pressure were observed by a Liquid-Liquid Injection Technique. The fuel injection rate at the higher injection valve opening pressure was measured by the Bosch method.

The engine performance, combustion characteristics and the effect of injection timing differences of a prechamber-type diesel engine operated by Diesel-fuel and methanol were investigated. When the Diesel-fuel is used as a pilot fuel, the ignition lag was mainly controlled by the Diesel-fuel. The maximum thermal efficiency occurs with the optimum main methanol injection timing. The optimum methanol injection timing is about 2 to 3 degrees crank angle before the ignition, as methanol vapor is required for smooth combustion. This was determined from results showing that the methanol combustion was initiated by flame propagation from the combustion of Diesel-fuel. It is advantageous that parts of the Diesel-fuel and methanol sprays be mixed.

A direct fuel-injection two-stroke cycle engine operated with neat methanol was investigated. The engine performance, combustion and exhaust-gas characteristics were analyzed experimentally and compared for operation with a carburetor, EFI injection at the intake manifold, and EFI injection at the scavenging port. The power and the brake thermal efficiency of the direct fuel-injection engine were higher than those of engines operated with a carburetor and either of the two EFI methods. The exhausted unburnt fuel of the direct fuel-injection engine was lower than that for operation with a carburetor, and formaldehyde and the CO concentration were of the same level as for operation with the carburetor and EFI methods. The NOx concentration of the direct fuel-injection was half the level of the result of carburetor operation.

The impact of minutely oxygen-enriched air on spark-ignition (SI) engine combustion was studied by obtaining engine performance measurements and investigating in-cylinder reactions. This study was initiated to determine if development of a new air-cleaner method, which may employ molecular sieve or membrane technology to slightly increase the oxygen concentration in the inducted air, is beneficial for engine operations. The air introduced into a single-cylinder SI engine was added with oxygen to produce oxygen concentrations of 21, 22 and 23%. Some results from engine tests performed with the oxygen enrichment are: The heat release lag, cycle variation and combustion period decreased; substantial reduction of emissions of unburned hydrocarbon emission and noticeable decrease of carbon monoxide were observed; and the brake thermal efficiency and engine output increased.

A water/Oil type emulsified fuel has been demonstrated to decrease the harmful exhaust emissions and increase a thermal efficiency of internal combustion engine experimentally(1)*. However, an emulsified fuel is not currently used for internal combustion engines. When we try to use an emulsified fuel for the internal combustion engines, especially for a compression ignition engine, we should clear the physical properties of emulsified fuel. Because the viscosity of the emulsified fuel affects the spray characteristics and following combustion characteristics. It is commonly recognized that the viscosity of emulsified fuel is much higher than that of the base fuels. However, there are no data which show the viscosity increase of emulsified fuel. We proposed an newly introduced specific surface area Sp/Se to estimate the viscosity of the emulsified fuel.

Under accelerating or decelerating operation, it is demanded to improve the performance and to reduce the exhaust smoke of diesel engines. Regarding the exhaust smoke regulation for a vehicle engine under transitional operation, the so-called free or controlled accelerating operation, are adopted as the simple measuring method. And the engine applied the construction or agricultural use is always operating under the load conditions of stepwise or periodical changes. For two-stroke cycle engines, in particular, the effects of operating conditions on the engine performance and the smoke character are unclear. In order to meet such demand, it is necessary to make clear the transitional character of each transfer element, i.e., the fuel injection system, the combustion process and the frictional loss.

To examine the effects of exhaust gas recirculation (EGR) on the exhaust emissions and on the cycle-by-cycle variation of combustion process in a methanol engine, the authors have tried to measure the emissions of total hydrocarbon, carbon monoxides, nitric oxides and formaldehyde and to record the cylinder pressure development histories of 1000 cycles duration. Moreover, the standard deviation of peak pressure Pmax, the heat release rate and the averaged pressure history are analyzed. The results are compared with those of gasoline fueled operation.

The engine performance, combustion characteristics and exhaust emission of pre-chamber type compression ignition engine operated by various biomass fuels were investigated experimentally. The biomass fuel investigated in this report are an emulsified fuel made with gas oil and hydrous ethanol or hydrous methanol, an emulsified fuel made with hydrous methanol and rape-seed oil, and neat rape-seed oil, and gas oil. There are small deviations of the experimental results between the biomass fuels, however, the general tendencies of the engine performances and exhaust gas characteristics operated by biomass fuels are as follows: The brake thermal efficiency during biomass fuel operation becomes maximum at a certain injection timing as well as those of the gas oil operation. And this injection timing is advanced with increasing the biomass content in the fuel.

Under the accelerating or decelerating operation, it is demanded to improve the performance and reduce the exhaust smoke of diesel engines. Regarding the exhaust smoke regulation for a vehicle engine under transitional operation, the so-called free or controlled accelerating operation, are adopted as the simple measuring method. And the engine applied for the construction or agriculture is always operating under the load conditions of stepwise or periodical changes. For two-stroke engines, in particular, the effects of operating conditions on the engine performance and the smoke character are unclear. In order to meet such demand, it is necessary to make clear the transitional character of each transfer element, i.e., the fuel injection system, the combustion process and the frictional loss.

Reduction of soot and NOx emissions from a prechamber-type diesel engine is studied by employing both chemical and physical aspects of the fuel and induction method. Fuel modification was performed to produce several forms of composite fuel: solution of alcohol and gas oil (JIS No. 1); emulsification and mixture of methyl alcohol-gas oil prepared by off- and in-line fuel systems; and separate injection of fuels into the pre- and main-chamber.

A two-stroke engine has various advantages. It is simple in structure, light in weight, high in mechanical efficiency, superior in accelerating ability, etc. However, its fuel consumption is bad, its combustibility under partial load is poor and it is usually accepted that its exhaust gas is problematic. With increasing traffic flow volume, it has become recently necessary to operate transiently each vehicle with frequent stops and starts, as well as decelerations and accelerations. From this standpoint, the authors have formed a simple dynamic model of two-stroke engine, and by means of simulation investigated how its performance can be improved while it is transiently operated, in combination with experiment. The results confirm that the calculations from the model coincide approximately with experiment. The influences of various factors on the performance have been revealed.

In this study, accordingly, methanol fuel was supplied in suction pipe with carburetor and with electronically-controlled fuel injector (EFI), which located in front of the suction valve, to clear experimentally the influence of various factors, such as the methanol-gasoline ratio (M/F), the difference in fuel feed system, the number of times of injection [ni], the injection timing (θinj), the engine speed (N), the volumetric efficiency (η v), the suction pipe wall temperature (tw), the water content in fuel (yw) etc., on the engine performance (the output and the thermal efficiency), the exhaust characteristics (NOx, CO, UBF and HCHO concentrations) and combustion variation as well as obtaining a guideline to establish the optimum condition. The authors will be report about the results of above-mentioned.

Many studies on the Cyclic variation of combustion process are made with a spark ignition engine. However, there are scarcely such studies with a diesel engine. Because, in general, the combustion of diesel engine is believed very stable. However, there exist some combustion variations in a diesel engine. As it is universally known, the combustion in a diesel engineis the series of a pre-mixed and a diffusion combustion, which is completely different from the combustion of a spark ignition engine. Therefore, it is impossible to determine the combustion variation of diesel engine by a direct application of the results of spark ignition engine. In this report, we discuss the several factors which indicate the combustion variation with a pre-chamber type diesel engine. The maximum pressure Pmax, the maximum rate of pressure rise (dP/dθ )max, the combustion pressure at each crank angle, etc. are analyzed from the continuous five handred of combustion pressure histories statistically.

It is important not only to increase a thermal efficiency of a spark ignition engine, but also to decrease a driving loss of auxiliary component of engine such as a cooling system. For example, there is a limitation of cooling performance when a requirement of aerodynamics design of a motorcycle or an automobile is severe. We propose an active application of ejector pump drove by exhaust energy to the cooling system. There were several applications of ejector system to the intake or exhaust system, but there was nothing for the design of it. In this report, one of the fundamental researches conducted in our laboratory, the effects of the dimensions of the ejector on the ejector performance are discussed. The results are followings: (1) The more the engine speed decreases, the more the ejector efficiency (G2/G1: G1 is the mass of charging air in the engine, G2 is the mass of entrained air by the ejector system) increases.

So far the studies on the dynamic characteristic of internal combustion engines have been mainly carried out on the governor system and have led to development of a mathematical model more efficient for simulation and control purpose. But, there are still uncertain dynamic behaviors of the engine. The experiment and analysis on the transfer characteristic of effective torque and engine speed under a changing fuel feed quantity or brake load were carried out by using the frequency response and step response methods. Consequently, it was confirmed that the transfer response of effective torque and engine speed to the changes in fuel feed quantity or brake load comprises a response time lag and its time constant is variable with the operating condition of the engine.

If the water/gas-oil-emulsion fuel is to be used in a compression ignition engine, it is necessary not only to carry out directly engine experiment but also to determine the characteristics of so-called mixture formation process, including those of fluidity, spray mode, injection rate and evaporation in high-temperature environment and on high-temperature wall as well as the influence of these characteristics on engine performance. In this report, the authors have experimentally investigated on the physical properties and injection characteristics of water/gas oil-emulsion fuel (W/O).

Engine combustion behaviors were investigated when the mixture condition at the intake port was varied. This experimental study was performed for several engine variables including types of cylinder head (gas motions), spark plug loction and MBT timing. Among the variables for the mixture condition at induction were the fuel/air mixture ratio (excess air factor) and the portion of atomized liquid fuel out of total fuel in the mixture. The engine operation was analyzed by obtaining the mean effective pressure, thermal efficiency, heat release history, stability of combustion, and lean misfire limit.

To determine definitely the transient characteristics of smoke emission on a Diesel engine, it is necessary to know those of each power transmission elements including its fuel injection system, combustion process, engine rotating system and its friction losses. Nevertheless, have been so far studied, it is unclearly about the relations the engine performance, smoke characteristics and influence of operating conditions, especially on the two-cycle engine. Therefore, the authors carried out the experiments while stepwise changing its brake load and fuel pump rack, respectively, to examine the effects of the operating conditions on the exhaust smoke density under transient operations.

In a small-type spark ignition engine with a carburetor, the mixture strength charged into a cylinder, that is, the combustion state and the exhaust emissions are remarkable influenced by instantaneous behavior of the fuel liquid-film flow on the inner wall of intake pipe, during transient running. Accordingly, the authors carried out some experiments in order to explicate the instantaneous mixture formation in cylinder, and go a step further, they had numerically analysed on the model of fuel supply system during the transient operation as the carburetor's throttle valve is stepwise changed.

In a two-stroke cycle engine, it is impossible to except the effect of engine brake, owing to its structure. However, since the necessity of engine brake has increased with increasing the vehicle speed, and with increasing the complexity of traffic problems, it is demanded to solved. For this reason, the authors investigated the mean frictional loss pressure of engine, and the effect of releasers on the engine brake with a crankcase-compression two-stroke cycle engine. The results, one of the weak points on a two-stroke cycle engine be solved completely by the application of releaser.