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Low NOx and soot free premixed diesel combustion can be realized by increasing ignition delays in low oxygen atmospheres, as well as the combustion here also depends on fuel ignitability. In this report single intermittent spray combustion with primary reference fuels and a normal heptane-toluene blend fuel under several oxygen concentrations in a constant volume combustion vessel was analyzed with high-speed color video and pressure data. Temperature and KL factor distributions are displayed with a 2-D two-color method. The results show that premixing is promoted with a decrease in oxygen concentration, and the local high temperature regions, above 2200 K, as well as the duration of their appearance decreases with the oxygen concentration. With normal heptane, mild premixed diesel combustion can be realized at 15 vol% oxygen and there is little luminous flame.

Diesel Particulate Filter (DPF) has become a key technology in modern diesel vehicles to achieve low emissions, and the performance of DPFs has been improved through considerable efforts by manufacturers. While DPF is essential to meeting the stringent regulations for particulate matter (PM), it has a negative impact on fuel efficiency (FE) due to its periodical regeneration for burning off the accumulated PM in DPF. Hence, detailed assessments on the FE impact of DPF regeneration technologies are necessary to better understand the FE potential of diesel vehicles. However, few quantitative FE studies have been reported regarding the DPF regeneration technologies applied to vehicles introduced into the market. We investigated the influence of the DPF regeneration on FE performance using three new diesel vehicles with different DPF regeneration technologies.

In this study influence of fatty acid methyl ester (FAME) blends in petroleum based diesel fuel on cold performance was investigated. First, influences on pour point (PP), cold filter plugging point (CFPP) and cloud point (CP) were evaluated for palm oil methyl ester (PME) and rape-seed oil methyl ester (RME) blends. RME-blended fuels showed similar properties to those of the base fuel. Thus, for vehicle tests, low temperature performance was examined with PME-blended fuels only. Startability and driveability were evaluated at varying temperatures using two vehicles (one old model and one new model). The results indicated that at low temperatures PME blends would deteriorate driveability performance.

Four fuels in the gasoline boiling range where tested in a constant volume combustion bomb and a variable compression ratio HCCI engine. The fuels were tested using a port fuel injection system. The results of the experiments defined the range of HCCI operation in terms of the Coefficient of Variation (COV) of IMEP and the maximum rate of pressure rise. The results for the test fuels are compared to each other and to a baseline gasoline. The results are discussed in terms of the effects of the fuel properties (basically, various measure of ignition quality) on the engine heat release rates and efficiencies.

For better understanding of diesel emissions in real world, the effects of driving conditions and fuel properties on diesel emissions were studied. A diesel engine system that is compliant to the Japanese New Short Term Regulation (J-2003 regulation) was used in this study. Major technologies for emission reduction were a common-rail high-pressure fuel injection equipment system, a cooled exhaust gas recirculation (EGR) system and a diesel oxidation catalyst (DOC). Various driving modes with a wide range of average vehicle speeds and accelerations were selected, including US FTP, US Highway, Japanese JC08, Japanese JE05, Tokyo Metropolitan Government #2, #5 and #8. Several kinds of test fuels of which characteristics were drastically changed in distillation range, aromatics content and sulfur content were used. A test fuel that complies with the Category-4 Specification of the World-Wide Fuel Charter (WWFC) was included.

The effect of sulfur concentration in gasoline fuel on emissions from vehicles equipped with lean NOx catalyst (LNC) was studied. The durability of the emission control systems against sulfur poisoning was evaluated using three recently launched vehicles under mileage accumulation tests. The major elements for the NOx trap function of the lean NOx catalysts evaluated in this study were Ba, Na and/or K. The range of sulfur contents of the test fuels was 3 to 80 ppm. The mileage accumulation was conducted up to 10,000 km mainly with Japanese 11 lap mileage accumulation driving cycle where the average and maximum velocities are 46 and 100 km/h respectively. The effects of vehicle velocity on emissions were also investigated by modifying the mileage accumulation driving cycle. As a result, it was found that the durability of the emission control systems against sulfur poisoning has been remarkably improved with the recently launched vehicles.

1 A novel analysis approach called “Regression Density method” was developed for better understanding of fuel property effects on exhaust emission. The approach was applied to diesel emission data obtained in JCAP programs and emission models were conducted to analyze the effects of fuel properties and engine conditions on emissions. By introducing this analysis method, the relationship between density factor and aromatics factor (chemical composition factor) was identified, however, they have been reported previously as dominant factors in fuel properties. The effects of engine conditions and fuel properties on emissions were investigated quantitatively based on the statistically conducted emission models to clarify universal ways to emission reduction. The mechanism of emission formation of vehicles and engines with characteristic behavior was also examined.