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An experimental ultra lightweight compact vehicle named “the Waseda Future Vehicle” has been designed and developed, aiming at a simultaneous achievement of low exhaust gas emissions, high fuel economy and driving performance. The vehicle is powered by a dual-type hybrid system having a SI engine, electric motor and generator. A high performance lithium-ion battery unit is used for electricity storage. A variety of driving cycles were reproduced using the hybrid vehicle on a chassis dynamometer. By changing the logics and parameters in the electronic control unit (ECU) of the engine, a significant improvement in emissions was possible, achieving a very high fuel economy of 34 km/h at the Japanese 10-15 drive mode. At the same time, a numerical simulation model has been developed to predict fuel economy. This would be very useful in determining design factors and optimizing operating conditions in the hybrid power system.

This is the study on the vibration characteristics of the fuel-injection pump body. Recently, refinement of the fuel spray is necessary in order to reduce the toxic substance, which is included in automotive exhaust gas of diesel engine for the automobile. To jet diesel fuel in higher pressure is a method for spraying the fuel more minute into a cylinder. However, this method causes the increase in respect of engine vibration and torque nonuniformity. The fuel-injection pump body receives not only this engine vibration by the method but also impact tute by the high-pressure injection. As this result, the sufficient performance cannot be demonstrated because large vibration deformations occur at the body and the camshaft of the fuel-injection pump. The vibration characteristics of the fuel-injection pump, which can reduce these vibration deformations, are necessary in order to lead to the performance.

The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines. This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments.

An experimental and numerical study has been conducted on the emission and reduction of HCHO (formaldehyde) and other pollutants formed in the cylinder of a direct-injection diesel engine fueled by methanol. Engine tests were performed under a variety of intake conditions including throttling, heating, and EGR (exhaust gas recirculation) for the purpose of improving these emissions by changing gas compositions and combustion temperatures in the cylinder. Moreover, a detailed kinetics model was developed and applied to methanol combustion to investigate HCHO formation and the reduction mechanism influenced by associated elementary reactions and in-cylinder mixing.

A numerical model has been developed to predict the formation of NOx and formaldehyde in the combustion and post-combustion zones of a methanol DI engine. For this purpose, a methanol-air mixture model combined with a full kinetics model has been introduced, taking into account 39 species with their 157 related elementary reactions. Through these kinetic simulations, a concept is proposed for optimizing methanol combustion and reducing exhaust emissions.

An experimental study was conducted to determine combustion and exhaust emissions characteristics in an automotive direct-injection diesel engine dual-fueled with natural gas with the objective of improving exhaust emissions and thermal efficiency. Dual-fuel operation can yield a high thermal efficiency almost comparable to the diesel operation and very low smoke at higher loads. However, NOx cannot be reduced by dual-fueling. On the other hand, at lower loads, a dual-fueled engine inevitably suffers from lower thermal efficiency and higher unburned fuel. To resolve these problems, the effects of exhaust gas recirculation (EGR) were investigated. The results show that in dual-fuel operation, hot EGR can improve thermal efficiency and reduce unburned fuel emission at lower loads, While cooled EGR can considerably reduce NOx at higher loads. A Pt oxidation catalyst can be used for additional reduction in unburned fuel emitted due to dual-fueling.

Dual-fuel operation of a direct-injection diesel engine with natural gas fuel can yield a high thermal efficiency almost comparable to the diesel operation at higher loads. The dual-fuel operation, however, at lower loads inevitably suffers from lower thermal efficiency and higher unburned fuel. To improve this problem, engine tests were carried out on a variety of engine parameters including diesel fuel injection timing advance, intake throttling and hot and cooled exhaust gas recirculation (EGR). It was found that diesel injection timing advance gave little improvement in thermal efficiency and increased NOx. Intake throttling promoted better combustion and shortened its duration with a consequent improvement in efficiency at higher natural gas fractions. Hot EGR raised thermal efficiency, reduced smoke levels, and maintained low NOx levels. Cooled EGR reduced NOx emissions but lowered thermal efficiency.

A new type of fuel injection nozzle, called a “slit nozzle,” has been developed to improve poor ignitability and to stabilize combustion under low load conditions in direct-injection methanol diesel engines manufactured for medium-duty trucks. This nozzle has a single oblong vent like a slit. Engine test results indicate that the slit nozzle can improve combustion and thermal efficiency, especially at low loads and no load. This can be explained by the fact that the slit nozzle forms a more highly concentrated methanol spray around the glow-plug than do multi-hole nozzles. As a result, this nozzle improves flame propagation.

Isuzu B-series engines are direct injection diesel engine comprising 4 cylinder light duty and 6 cylinder medium duty versions. These engines have been marketed on a worldwide basis not only for vehicle use but also for industrial and marine use. The production volume in 1987 was NO.1 in the world in this class. This paper describes the general outline of B-series engines and the 6BG1TC model with turbocharger and intercooler which develops the highest maximum output of these engines. This engine was developed in 1985 for the first time for medium duty truck in the domestic market and introduced in USA market in 1988. For the moment, our engineering efforts are directed to clear USA exhaust emission regulation for 1991.

Development status of small direct Injection diesel engine at Isuzu Motors Ltd. is reviewed. There is much difficulty in combustion optimization of small DI engines, due to small combustion chamber volume, large surface to volume ratio, wide engine speed range and so on, Novel ideas in the area of injection system, combustion chamber and induction swirl were tried to solve these problems and their effects are presented here. Our prototype DI engines which adopted some of these ideas has turned out to have better fuel economy by about 15 percent, 2-3 dB(A) higher noise level than IDI and almost the same power output performance as IDI. As to exhaust emissions, they have a possibility to conform to ′86 California emission standards, in inertia weight classes up to 2625 LBS. The remaining problem areas are noise emission, durability of injection pump and cabin heater performance.

Isuzu Motors Limited has recently-developed 2.5 liter and 2.8 liter diesel engines to power Isuzu “ELF” trucks (payload 1-2 tons). These two engines are high fuel economy direct injection diesels featuring a square cavity combustion chamber and Bosch VE distributor type injection pump. To reduce the D.I. diesel engine noises, the combustion chamber, fuel injection system, and cylinder block construction have been improved. In addition, a vibration damping sheet oil pan, timing belt drive, and cylinder block, cover are employed. The two diesel engines are small size, light weight, highly reliable engines to be successors to the 2.0, 2.2 and 2.4 liter Isuzu “C”-series diesel engines. To date, 2 million of these engines have been produced to power the Isuzu “ELF” trucks and other vehicles as well as a wide variety of industrial and marine applications.

An appropriate configuration of square cavities shows two distinct characteristics when compared with the characteristics of the circular cavity. One is that the injection angle to the square cavity wall has some effect on reducing smoke level at low engine speeds and loses this effect with increasing engine speed. Secondly, the reduction in swirl at high engine speeds results in a better balance of swirl over the entire engine operating range. This allows best injection timing for BMEP to be retarded resulting in lower NOx and noise.

The diesel engine with a electronic control system which has been used in production passenger cars in Isuzu shows great advantages such as fuel economy, idle noise, cold startability and output performance by the help of the new commet V combustion chamber design. The new combustion chamber which differs in shape and throat area from the conventional commet V has been developed to be well matched to the electronic control system. The passenger car equipped with the electronic control diesel engine mentioned above provides the following four additional advantages: 1. Good acceleration response 2. Idle speed control which is affected by engine coolant temperature, on-off of the air conditioning compressor and battery voltage 3. Cruise control 4. Self-diagnostic system

The 4BC2 diesel is a small DI engine of 3.27 litres displacement and maximum power output of 100 PS(73.6 KW)/3500 RPM(JIS) developed for small truck application. This paper describes comparative study results indicating that this DI diesel offers approximately 15% fuel economy advantage over IDI of the corresponding displacement and DI noise levels are 3-5 dB(A) lower at idling and the same or lower at full load compared with IDI. Also covered are the DI features which leads to improvement of coolant heat-up performance to the same levels as with IDI.

The following features of a small high-speed DI engine are counterplans of unsuitable changes in the engine performance occurring in DI engine down-sizing and in the increasing of engine speed. The features differ in each design of the gasket, the piston, the nozzle and the nozzle holder from the conventional diesel design technology. These features can raise the engine performance of small engines up to the level of large engines.

This paper describes the recent trend toward dieselization of light and medium duty trucks in Japan. The customers needs are of prime consideration in engine development. Improvements have been made mainly in the areas of increased power, fuel economy, and anti-pollution. Maximum effort is being applied to meet government regulations both in exhaust emissions and noise. Some of the recent engineering developments in light duty, high speed diesel engines in Japan are described.