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Ultra-low energy consumption and ultra-low emission vehicle technologies have been developed by combining petroleum-alternative clean energy with a hybrid electric vehicle (HEV) system. Their component technologies cover a wide range of vehicle types, such as passenger cars, delivery trucks, and city buses, adsorbed natural gas (ANG), compressed natural gas (CNG), and dimethyl ether (DME) as fuels, series (S-HEV) and series/parallel (SP-HEV) for hybrid types, and as energy storage systems (ESSs), flywheel batteries (FWBs), capacitors, and lithium-ion (Li-ion) batteries. Evaluation tests confirmed that the energy consumption of the developed vehicles is 1/2 of that of conventional diesel vehicles, and the exhaust emission levels are comparable to Japan's ultra-low emission vehicle (J-ULEV) level.

Four urea SCR systems were developed and evaluated on a C/D and on the road to investigate their potential for Japanese emission regulations in 2005 and beyond. Test results showed that NOx conversion ratios were 50 to 70% during the Japanese D13 mode cycle, and the ratios under the transient driving cycle were lower than those tested during a steady state. Unregulated emissions, such as benzene, aldehyde and benzo[a]pyrene, existed either at a trace level using the oxidation catalyst, or lower than a base diesel engine, when no oxidation catalyst was used. The health effects of particulate matter emitted from the SCR system were almost the same as those from conventional diesel engines, as evaluated by the Ames test and in vitro micronucleus test. Thermal degradation products, such as cyanuric acid and melamine, were two to four figures lower compared with the toxicological information of Safety Information Resources Inc. (SIRI).

Five diesel particulate filter systems have been studied for their practicality in the case of their application to garbage trucks operating in urban areas. Driving data of garbage trucks operating in Tokyo were collected, and a driving pattern was prepared to evaluate filter systems. Test engines fitted with a wall-flow-monolith filter were in the range of 2.8 to 3.6 liters in displacement. Each test engine was operated for an accumulated loading time of 400 hours using an engine dynamometer. Regeneration used was electric heater, diesel fuel burner and intake-exhaust gas throttling. Regeneration temperature of the throttling system was lower and more stable than other systems at every regeneration. In the electric heater regeneration, on the other hand, the temperature distribution in the filter was different at every cycle, and its temperature gradient was steep.

Four different diesel particulate filter (DPF) systems for city buses have been studied on an engine bench, and based on the results, their practicalities are discussed. On road data of buses operating in Tokyo were collected, and a city bus driving pattern for engine bench test was prepared. Evaluation tests were carried out on an engine bench using an 11-liters engine, used on city buses. The test engine equipped with a DPF system was operated on cyclic test of the city bus driving pattern for the accumulated loading time of 400 hours. Each of the DPF systems has a wall flow monolith filter. A diesel fuel burner or an electric heater with or without catalyst-coated filter is used for regeneration. It is possible to remove about 90% of particulates from the exhaust gas by the use of DPF systems for diesel engines. Soluble organic fraction (SOF) is reduced by about 30%. It is difficult to sufficiently remove SOF.

Thermal efficiency of carbureted and injection engine was compared through thermodynamic cycle simulation. When the compression ratio is the same, the combined control carbureted engine in which the A/F ratio control method is used in the high load range and the throttling method is used in the low load range shows the highest thermal efficiency followed by the injection engine and the throttling carbureted engine. The thermal efficiency of the injection engine is lower than that of combined control carbureted engine because the temperature of gases in cylinder does not rise much due to stratified charge combustion. When the compression ratio of these engines is optimized, the thermal efficiency is the highest for the injection engine followed by the combined control carbureted engine. The thermal efficiency of the combined control carbureted engine is lower than that of the injection engine at high and low loads, but they are in the same level at intermediate loads.

Ignition and combustion of methanol in a spark-assisted methanol diesel engine were studied for the purpose of developing such an engine that is practical for actual vehicles. It became clear through investigations on combustion of methanol in a spark-assisted methanol diesel engine that methanol combustion proceeds mainly by flame propagation. Based on this finding, effects of such parameters as the injection direction, ignition position, ignition energy, compression ratio, injection timing and ignition timing were studied to obtain optimal conditions for methanol combustion. It was found through such studies that it is effective to form the mixture upstream of the spark, plug relative to the swirling direction and increase the inductive component of the ignition energy to achieve a high ignition stability.

This paper describes the development of a dilution mini-tunnel to allow measurement of diesel exhaust particulate emissions in transient operating cycles. The dimensions of the tunnel were 84 mm inner diameter and 1.7 m length. A fraction of the total exhaust gas is drawn into the tunnel by an air ejector. The amount of exhaust gas depends on the flow rate of driving air in the air ejector corresponds to the operating engine speed. Performance of the dilution mini-tunnel system was examined using a light-duty vehicle under steady-state conditions and FTP cycles. A good correlation was found between the particulate emission rates measured in the mini-tunnel system and those measured in a total exhaust dilution tunnel system.

A diesel engine with a dual-fuel (methanol-diesel) injection system has been developed, and the practicality of a prototype bus equipped with the developed engine has been confirmed. This study showed that methanol could be substituted for diesel fuel at the rates of 86 vol. percent in transient mode operation and 94 vol. percent in steady-state operation. Driving performance was equivalent to that of a conventional bus. Fuel economy of the dual-fuel injection engine was the same as that of a conventional diesel engine in steady-state operation, and decreased by about 9 percent in transient mode operation. The dual-fuel injection engine met the Japanese regulations on exhaust emissions stipulated in 1979. Exhaust smoke and particulate emissions were extremely reduced to the level of smoke-free operation.

Schlieren and direct cine photography have been used in conjunction with the gas sampling method to investigate three dimensional combustion phenomena in a DI diesel engine cylinder. Gas movement, dispersion of fuel-air mixture after fuel impingement on the cavity wall and the combustion process under continuous running conditions were observed. Gas concentrations of NOx, THC, CO, CO2, O2, H2 and decomposed hydrocarbons were analyzed. The distribution of equivalent fuel concentration and the decomposition process of fuel are presented. Air swirl accelerates the homogeneity of fuel-air mixture after spray impingement on the cavity wall. It is concluded that a combined measurement by photography and gas sampling method is a useful one to combustion study of diesel engines.