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Diesel engines are highly potential for better fuel economy due to a high thermal efficiency and fuel diversity. They are largely expected to contribute to a low carbon society in the future. Diesel engines have been developed for the purpose of controlling global warming and improving the air quality and health effects in the world. Although particles produced by combustion in cylinders of the diesel engines are emitted to the air, they are dramatically reduced by beyond 99.9% after being trapped by a diesel particulate filter (DPF) and a diesel oxidation catalyst (DOC) of the after-treatment systems. However phenomena of the formation of the particles in the cylinders and exhaust behaviors of the particles after being trapped by the DPF are not clearly explained yet (1)-(6) and effects of the DOC on the formation and the reduction of the particles are still not clarified (7)(8).

Diesel engines have high potential for better fuel economy due to a high thermal efficiency and fuel diversity. They are largely expected to contribute to a low carbon society in the future. This paper describes how the increase of the Biodiesel Fuel (BDF) mixing ratio reduces CO, HC, smoke and engine-out particle number (PN) concentration. Most notably, the PN concentration by using BDF100 can be reduced to approximately a half of diesel fuels. Additionally, this paper shows that the PN concentration from the tail pipe is reduced by over 99.95% with a DPF. Further, this paper also introduces the relationship between fuel consumption (FC), PN concentration and engine oil.

Mankind developed and enjoyed the automobile civilization, and has lauded the prosperity that it brought about. Commercial vehicle launched the heavy duty diesel engine have been contributing by main transportation system for development of society in the world. However both the local and global environment issues appear depend on the life of mankind, in the world. Especially, global warming is the most stringent issue for our life on the earth. We human beings must lay our existence on the line, and call upon expertise to create solutions for this situation. Diesel engine has great potential for the global warming compatibility by it's high thermal efficiency and diesel vehicle is expected to conserve the environment and to improve the fuel saving for keeping resources in the world. This paper introduces the surrounding of the automobile, such as exhaust emission regulation for heavy duty diesel vehicle, amount and contribution of CO2 emission and noise.

Reduction of smoke emission from diesel engines is important in order to meet upcoming stringent exhaust gas regulations and also for improving fuel economy. In this paper, the reduction of smoke from DI diesel engines for heavy duty vehicles is discussed. A single cylinder engine test and three dimensional numerical analysis were carried out in order to obtain necessary and useful information for designing a combustion chamber and a fuel injection nozzle that could realize reduced smoke emission. This study is focused particularly on the behavior of the fuel spray which impinges on the piston cavity wall in the case of a reentrant type combustion bowl. As a result, it was found that the spray wall-impingement angle performs an important role in promoting fuel-air mixing. It is thus an important parameter which controls the main combustion region.

This study has experimentally clarified the effects the pilot injection fuel quantity and pilot injection timing have on the mode of combustion of the pilot spray and exhaust emissions. The result shows that one of the points to effectively reduce exhaust emissions by pilot injection is to reduce the emissions produced by the pilot combustion itself. For that purpose it is effective to advance the pilot injection timing and to increase of pilot quantity. In this case, dividing the pilot injection into multiple small-quantity shots is a solution to avoid cylinder wall wetting.

Investigations of Homogeneous Charge Compression Ignition (HCCI) combustion have been actively conducted as a new combustion technology to substantially and simultaneously reduce NOx and soot to comply with the future stringent exhaust emission regulations. In the past, a method of injecting fuel at the initial stage of the compression stroke has been proposed, but it is known that fuel adheres to the cylinder wall, causing a decline in combustion efficiency and oil dilution. The authors have developed Premixed Compression Ignition (PCI) combustion as a technology of solving the above problem as well as simultaneously reducing NOx and soot. In PCI combustion, fuel is injected into a combustion chamber in the vicinity of the top dead center for preventing fuel from adhering to the wall, and pre-mixture, which is formed shortly before ignition, is burnt.

In the next few years, the USA, EU, and Japan plan to introduce very stringent exhaust emissions regulations for heavy–duty diesel engines, in order to enhance the protection air quality. This builds upon the heavy–duty diesel engine exhaust emissions regulations already in effect. At the same time, improvement in fuel consumption of heavy–duty diesel engines will be very important for lowering vehicle operating costs, conserving fossil fuel resources, and reduction of CO2 (greenhouse gas) levels. This paper presents a detailed review of a quiescent combustion system for a heavy–duty diesel engine, which offers breakthrough performance in terms of the exhaust emissions – fuel consumption trade–off, compared with the more conventional swirl supported combustion system. This conclusion is supported by experimental results comparing quiescent and swirl supported versions of various combustion system configurations.

With the intention of improving engine performance and emissions, the authors examined the influence of the method of initial fuel injection quantity reduction and of the injector configuration of a common rail fuel injection system on engine performance and exhaust emissions. Results showed that decreasing the nozzle hole diameter was an effective way to reduce the initial injection quantity without increasing black smoke. Compared to a three-way type injector, it was found that a two-way type injector can greatly reduce the amount of fuel leakage from the electromagnetic injector control valve and fuel consumption could be further improved by reduction of the driving loss. Furthermore, the increase of driving losses with higher injection pressure was small, and as a result, higher pressure injection was possible.

This paper reviews the trend in worldwide exhaust emission regulations for heavy-duty diesel engines and common key technologies that must be developed and applied in order to meet these regulations. The common key technologies are intake and exhaust system with turbocharger and intercooler, electronically controlled high-pressure fuel injection system, exhaust gas recirculation, and exhaust gas after-treatment devices. This paper also introduces test results of common key technologies, concepts for low-emission heavy-duty diesel engines, and the possibilities for meeting future exhaust emission legislation is described.

In this study three EGR methods were applied to a 12 liter turbocharged and intercooled Dl diesel engine, and the exhaust emission and fuel consumption characteristics were compared. One method is the Low Pressure Route system, in which the EGR is taken from down stream of the turbine to the compressor entrance. The other two systems are variations of the High Pressure Route system, in which the EGR is taken from the exhaust manifold to the intake manifold. One of the two High Pressure Route EGR systems is with back pressure valve located at downstream of the turbine and the other uses a variable geometry(VG) turbocharger. It was found that the High Pressure Route EGR system using VG turbocharger was the most effective and practical. With this method the EGR area could be enlarged and NOx reduced by 22% without increase in smoke or fuel consumption while maintaining an adequate excess air ratio.

In this study a new water injection system was applied to an 11 liter naturally aspirated DI diesel engine in order to reduce exhaust emissions. In this system, the water and fuel were arranged in the injection nozzle during the time between injections as fuel, water and then fuel. The fuel and water were then injected into the cylinder in that order. The tests were conducted at several engine operating conditions from the Japanese 13 mode test cycle to clarify effects of water injection on exhaust emissions and fuel consumption. The results showed that NOx reduction was directly proportional to the relative amount of water injection, regardless of engine speed and load. By using the optimal relative amount of water injection at each engine operating condition, total NOx and particulate matter (PM) in the Japanese 13 mode test cycle were reduced by 50% and 25%, respectively, without a fuel consumption penalty.

In the diesel engine industry, the growing trends are toward wider use of electronically controlled high pressure fuel injection equipment to provide better engine performance, while conforming to the stringent exhaust emission standards. Although there have been some recent announcements of a diesel engine that applies an electronically controlled common rail type fuel injection system, there is little literature published about any attempt to reduce both exhaust emissions and noise and to improve engine performance by varying injection pressure and injection timing independently and introducing pilot injection in combination. This paper describes the details of a study made on the parameters associated with injection timing, injection pressure and pilot injection and the procedures for their optimization, with an electronically controlled common rail type fuel injection system installed in an in-line 6-cylinder 6.9 liter turbocharged and intercooled DI diesel engine.

In order to reduce exhaust emission and combustion noise and to improve fuel consumption, the effects of the combustion system parameters of a diesel engine, such as injection pressure, injection nozzle hole diameter, swirl ratio, and EGR rate on exhaust emissions, combustion noise and fuel consumption are investigated and described in detail by analyzing rate of heat release, needle valve lift and injection pressure. Based on these results, reduction of exhaust emission and combustion noise and improvement of fuel consumption are described in the latter part of this paper. These results are shown as follows. The smaller nozzle hole diameter is effective for reducing smoke and PM, and by optimizing the injection timing and swirl ratio, NOx can also be reduced. In addition to the above, by applying EGR and higher injection pressure it is possible to improve the fuel consumption with the remaining low NOx and PM.

Recent global environmental problems which have come to light must be solved for ensuring the survival of the human race. And it is of the utmost importance that we give to our descendants a world full of nature and beauty. In the past years Mitsubishi Motors Corporation (MMC) has long been positive in research and the development activities so as to satisfy the demands for low emission and good fuel economy vehicles. (1) As one example of our research efforts, the technology that will meet the US '94 HDDE exhaust emission regulations, which is one of the most stringent regulations in the world, is described in this paper. The exhaust emissions were reduced by improvement of combustion, using the pre-stroke control type fuel injection pump and optimizing the combustion chamber shape. Efforts were also made to improve the oil consumption, in order to reduce PM (Particulate Matter) emission.

Protection of the Earth's environment by means of energy saving and cleaning up of air pollution on a global scale is one of the most important subjects in the world today. Because of this, the requirements for better fuel economy and cleaner exhaust emissions of internal combustion engines have been getting stronger, and, in particular, simultaneous reduction in nitrogen oxides (NOx) and particulate matter (PM) from heavy-duty diesel engines (HDDEs) without degrading fuel economy has become a major subject. Mitsubishi Motors Corporation (MM) has been selling diesel-powered heavy-duty trucks in the U.S. market since 1985 and has agressively carried out development work for meeting the 1991 model year exhaust emission standards.