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Fischer-Tropsch Diesel (FTD) fuel is expected to be a promising clean diesel fuel in the future because of its characteristics of zero sulfur, zero aromatics and a high cetane number. However, the optimum fuel properties for diesel engines have not been realized. In this study, the effects of cetane number and distillation characteristics on engine-out PM emissions from a conventional direct injection diesel engine were investigated by using paraffinic fuels which were made to simulate FTD fuel. From the results of the vehicle exhaust emissions test and engine dynamometer test, it was found that the narrow distillation characteristics (which eliminates heavy hydrocarbon fraction) could reduce the soluble organic fraction (SOF) in PM emissions, and the excess high cetane number characteristic promoted the formation of insoluble organic fraction (ISOF).

Effects of fuel distillation characteristics and cetane number on premixed charge compression ignition (PCCI) combustion were investigated for the purpose of reducing NOx and PM emissions from a direct injection diesel engine. The test engine had a hole type injection nozzle for conventional diesel combustion at high load operation. A low compression ratio and cooled EGR were applied to the test engine in order to reduce the compression temperature for avoiding pre-ignition. The investigation results show that, in the case of ignition control by EGR, a light fuel with lower distillation characteristics had an advantage of reducing smoke at higher loads. This means that high volatility fuel is effective in promoting lean mixture formation of fuel and air during the ignition delay. Moreover, lowering the cetane number was effective in reducing NOx emissions by suppression of combustion temperature.

A new after-treatment system called DPNR (Diesel Particulate-NOx Reduction System) has been developed for simultaneous and continuous reduction of particulate matter (PM) and nitrogen oxides (NOx) in diesel exhaust gas. This system consists of both a new catalytic technology and a new diesel combustion technology which enables rich operating conditions in diesel engines. The catalytic converter for the DPNR has a newly developed porous ceramic structure coated with a NOx storage reduction catalyst. A fresh DPNR catalyst reduced more than 80 % of both PM and NOx. This paper describes the concept and performance of the system in detail. Especially, the details of the PM oxidation mechanism in DPNR are described.

The white smoke generated by a diesel engine was analyzed and found to consist mainly of hydrocarbons. Test results indicated that the emission level depends on ambient temperature. A compact white smoke meter was developed to enable emission levels to be accurately measured. The internal temperature of this meter is controlled so that white smoke is generated within the measuring device. The meter was used to evaluate the effectiveness of various white smoke emission control devices for the DI diesel engine. The results indicated that an intake air heater offers the greatest potential. Accordingly, a new intake air heater with ceramic PTC thermistor having a very high heating efficiency was developed to reduce white smoke emission.