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In this study, the heated fuels were provided to the diesel engine in order to activate the fuel before the injection. Two test fuels: the normal diesel fuel and cetane, which have different boiling points were used. For both normal diesel fuel and cetane, crank angles at ignition and maximum pressure are delayed and the maximum combustion pressure is decreased as the fuel temperature rises. In cases of large and middle mass flow rate of fuel injection, the brake thermal efficiency and brake mean effective pressure are decreased when the fuel temperature is higher than 570 [K]. However, in the case of small mass flow rate of fuel injection, the brake thermal efficiency is almost independent of fuel temperature. HC and CO concentrations in the exhaust gas emission show constant values regardless of fuel temperature. However, NOx concentration is gradually decreased as the fuel temperature rises.

Internal combustion engines have been required to achieve even higher efficiency in recent years in order to address environmental concerns. However, knock induced by abnormal combustion in spark-ignition engines has impeded efforts to attain higher efficiency. Knock characteristics during abnormal combustion were investigated in this study by in-cylinder visualization and spectroscopic measurements using a four-stroke air-cooled single-cylinder engine. The results revealed that knock intensity and the manner in which the autoignited flame propagated in the end gas differed depending on the engine speed.

DME is alternate fuel for diesel engines, however DME has defects such as small lower calorific value, inferior lubricity and weak fuel penetration. To compensate disadvantages, In-direct injection 2-stroke diesel engine with low pressure fuel injection system was proposed. The fuel injection timing near TDC gave good performance because the heat loss of low temperature oxidation reaction reduced. The brake torque and brake thermal efficiency of 2-stroke IDI diesel engine were lower than those of 4-stroke engine. However, the exhaust gas emissions were very low level because the intake air leaked through the exhaust port and the exhaust gas was diluted.

In-cylinder visualization of the entire bore area at an identical frame rate was used to investigate knocking conditions under spark ignition (SI) combustion and under Homogeneous Charge Compression Ignition (HCCI) combustion in the same test engine. A frequency analysis was also conducted on the measured pressure signals. The results revealed that a combustion regime accompanied by strong pressure oscillations occurred in both the SI and HCCI modes, which was presumably caused by rapid autoignition with attendant brilliant light emission that took place near the cylinder wall. It was found that the knocking timing was the dominant factor of this combustion regime accompanied by cylinder pressure oscillations in both the SI and HCCI combustion modes.

The purpose of this study is to explore an effect of the coconut oil methyl ester (CME) and vegetable oil methyl ester (VME) on a low compression ratio diesel engine performance. CME and VME were produced from coconut oil and vegetable oil with methanol, respectively. Vegetable oil was assumed to contain 60 wt.% of soybean oil and 40 wt.% rapeseed oil. The engine performance was measured in the steady operating condition at 3600 rpm of engine speed. The ignition timings of CME and VME were advanced and the maximum cylinder pressures of CME and VME were higher as compared with the diesel fuel at low compression ratio, because CME and VME consisted of medium chain fatty acid methyl esters. The ignitability of CME was superior to VME, because CME consisted of saturated fatty acid. The brake thermal efficiency of diesel fuel was slightly higher than CME and VME at any compression ratios.

The purpose of this study is to explore an effect of cooled-EGR on the diesel engine performance fueled with coconut-oil methyl ester (CME). The exhaust gas was cooled by the water at room temperature and was fed to the intake manifold, and the EGR rate was changed from 0 % to 30 % at every 10 %. The engine performances were measured at several EGR rates, fuel injection pressures and timings. Test fuels were CME and commercial diesel fuel. In the case of high EGR rate at which the compression ignition was deteriorated, the ignition timing of CME was always earlier than that of diesel fuel, therefore CME had good ignitability as compared with diesel fuel under EGR application. When the fuel injection pressure was increased at high EGR rate, the ignition delay was improved by the fuel atomization and air-fuel mixing effect.

Homogenous Charge Compression Ignition (HCCI) combustion experiments were conducted in this study using a single-cylinder test engine fitted with a sapphire observation window to facilitate visualization of the entire cylinder bore area. In addition to in-cylinder visualization of combustion, spectroscopic measurements were made of light emission and absorption in the combustion chamber to investigate autoignition behavior in detail. Engine firing experiments were conducted to visualize HCCI combustion over a wide range of compression ratios from 12:1 to 22:1. The results showed that increasing the compression ratio advanced the ignition timing and increased the maximum pressure rise rate, making it necessary to moderate combustion. It was also found that autoignition can be induced even in a mixture lean enough to cause misfiring by raising the intake air temperature so as to advance the overall combustion process.

We have investigated combustion characteristics of lean gasoline-air pre-mixture ignited by gas-oil injection using a high compression D.I. diesel engine. Gasoline was supplied as an uniform lean mixture by using carburetors, and gas-oil was directly injected into the cylinder. Two different types of combustion chamber were attempted. It was confirmed that the lean mixture of air-fuel ratio between 150 and 35 could be ignited and burned by this ignition method. An engine with the re-entrant type combustion chamber had an advantage for combustion and ignition. The brake mean effective pressure increased when relatively rich mixture was provided with a small amount of the gas-oil injection. As the gas-oil injection increased, HC concentration decreased, and NO and CO concentration increased. The exhaust gas emission of pollutants could be reduced when lean mixture was ignited by an optimum gas-oil injection.

This paper deals with the steering system with conventional round steering-wheel from the view point of Steer-by-Wire system design. Steering gear ratio and control force characteristics are selected as interface variables of the steering system. The concept of ideal steering gear ratio which is derived on the basis of mapping of steering wheel angle and vehicle path angle is proposed to determine steering gear ratio. Simulator experiments are conducted to investigate the effects of interface variables on system and driver’s control performance. Validity of proposed ideal steering gear ratio would be confirmed. Candidates for objective task performance measure to define desirable control force characteristics would be determined from the test results.

One issue of downsized and supercharged engines is low-speed pre-ignition (LSPI) that occurs in the low-speed and high-load operating region. One proposed cause of LSPI is the influence of the engine oil and its additives. However, the effect of engine oil additives on pre-ignition and the mechanism involved are still not fully understood. This study investigated the influence of engine oil additives on abnormal combustion in a spark-ignition engine. A four-stroke air-cooled single-cylinder engine with a side valve arrangement was used in conducting combustion experiments. The research methods used were in-cylinder pressure analysis, in-cylinder visualization and absorption spectroscopic analysis. Engine oil additives were mixed individually at a fixed concentration into a primary reference fuel with an octane number of 50 and their effect on knocking was investigated.

Homogeneous Charge Compression Ignition (HCCI) combustion has attracted widespread interest as a combustion system that offers the advantages of high efficiency and low exhaust emissions. However, it is difficult to control the ignition timing in an HCCI combustion system owing to the lack of a physical means of initiating ignition like the spark plug in a gasoline engine or fuel injection in a diesel engine. Moreover, because the mixture ignites simultaneously at multiple locations in the cylinder, it produces an enormous amount of heat in a short period of time, which causes greater engine noise, abnormal combustion and other problems in the high load region. The purpose of this study was to expand the region of stable HCCI engine operation by finding a solution to these issues of HCCI combustion.

In this study, a spectroscopic method was used to measure the combustion characteristics of a test diesel engine when operated on dimethyl ether (DME) under a homogenous charge compression ignition (HCCI) combustion process. A numerical analysis was made of the elementary reactions using Chemkin 4.0 to perform the calculations. The results of the analysis showed that compression ratio changes and the methane additive influenced the autoignition timing in the DME-HCCI combustion process. In the experiments, reducing the compression ratio delayed the time of the peak cylinder pressure until after top dead center, thereby increasing the crankshaft output and thermal efficiency. The addition of methane enabled the DME-HCCI engine to provide crankshaft output equivalent to that seen for diesel engine operation at a low equivalence ratio. This paper discusses these effects in reference to the experimental and calculated results.

We developed a novel ignition method called laser breakdown-assisted long-distance discharge ignition (LBALDI) that combines laser breakdown with a discharge to realize lean combustion. The creation of laser breakdown plasma between electrodes for discharge enables discharges over longer distances than those of conventional sparkplug as inferred from laser-triggered lightning or laser-triggered gas switches. This method should help realize volumetric ignition through the creation of a long-distance discharge. Experiments on the fundamental discharge and ignition of methane/air mixtures were conducted. The optimum incident time of the laser prior to the application of a high voltage was found to reduce the sparkover voltage and markedly reduce the voltage required by LBALDI under pressurized air conditions. In the ignition experiment, LBALDI showed the fastest heat release rate at the lean flammable limit.

Attention has recently been focused on homogeneous charge compression ignition (HCCI) as an effective combustion process for resolving issues inherent to the nature of combustion. Dimethyl ether (DME; CH3OCH3) has attracted interest as a potential alternative fuel for compression ignition engines. We measured the HCCI process of DME in a test diesel engine by using a spectroscopic method. Simultaneous measurements were also done on exhaust emissions of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). Based on the experimental data, this paper discusses the relationship between the equivalence ratio and the observed tendencies.

A small 2-stroke engine can be an effective power source for an electric generator mounted on a series hybrid electric vehicle. In recent years, a technology referred to as pre-chamber jet combustion has attracted attention as a means of enhancing thermal efficiency by improving mixture ignitability. In this study, experiments were conducted to investigate differences in combustion behavior between the application of spark-ignited (SI) combustion and pre-chamber jet combustion to a small, two-stroke engine. The experimental equipment used was a two-stroke, single-cylinder, optically accessible engine with a displacement of 63.3 cm3. Differences between conventional SI combustion and pre-chamber jet combustion were examined by means of in-cylinder pressure analysis, in-cylinder combustion visualization and image processing software. The diameter of the connecting orifice of the pre-chamber was varied between two types.

The uniform lean gasoline-air mixture was provided to diesel engine and was ignited by direct diesel fuel injection. The mixing region that is formed by diesel fuel penetration and entrainment of ambient mixture is regarded as combustible turbulent jet. The ignition occurs in this region and the ambient lean mixture is burned by flame propagation. The lean mixture of air-fuel ratio between 150 and 35 could be ignited and burned by this ignition method. An increase of diesel fuel injection is effective to ensure combustion and ignition. As diesel fuel injection increases, HC concentration decreases, and NOx and CO concentration increases.

The purpose of this study is to realize dual-combustion cycle for gasoline engines. For the purpose, lean combustion and direct fuel injection were applied to small diesel engine. The lean gasoline-air mixture was provided and was ignited by small amount of pilot diesel fuel injection (constant volume combustion). Then, diesel fuel was injected by main injection and was burned with the remained oxygen after the lean combustion (diffusion combustion). The equivalence ratio 0.3, 0.4 and 0.5 of mixture were used to avoid the spontaneous compression auto-ignition. The total equivalence ratio with supplied gasoline and diesel fuel was adjusted to 1.0. The base pilot injection timing was selected as the ignition of pre-mixture took place at T.D.C. and pilot injection timings were changed 2 degree before and behind of base timing. The main fuel injection timings were 50, 75 and 100% of the duration between pilot injection timing and T.D.C.

Attention has recently been focused on homogeneous charge compression ignition combustion (HCCI) as an effective combustion process for resolving the essential nature of combustion. Meanwhile, dimethylether (DME) has attracted interest as a potential alternative fuel for compression ignition engines. Authors measured the combustion process of DME HCCI by using a spectroscopic method. A diesel engine was used as the test engine. The results of these analyses showed that changes in the compression ratio, intake air temperature and equivalence ratio influenced the ignition timing in the HCCI combustion process. This paper discusses these effects in reference to the experimental and calculated results.

The purpose of this study is to elucidate the development process of hot kernel generated by the laser induced breakdown and to clarify the relationship between corona discharge application and flame propagation. The mixture can be ignited by the laser induced breakdown. Nd:YAG laser is used for the ignition and laser light is optically focused on the central part of combustion chamber by a plano convex lens. The hot kernel is observed in the absence of combustion and is rapidly developed into the laser incidence side. The homogeneous propane-air mixture is used and six equivalence ratios between 0.7 and 1.5 are tested. For generating the positive corona discharge in the combustion chamber, a non-uniform electric field is applied by the needle to plane gap. In a lean mixture, the whole flame front shifts to downward from the breakdown point and, in the rich mixture region, the combustion is strongly enhanced.