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The engine in the research is a single cylinder DI diesel using the emission reduction techniques such as high boost, high injection pressure and broad range and high quantity of exhaust gas recirculation (EGR). The study especially focuses on the reduction of particulate matter (PM) under the engine operating conditions. In the experiment the authors measured engine performance, exhaust gases and mass of PM by low sulfur fuel such as 3 ppm and low sulfur lubricant oil such as 0.26%. Then the PM components were divided into soluble organic fraction (SOF) and insoluble organic fraction (ISOF) and they were measured at each engine condition. The mass of SOF was measured from the fuel fraction and lubricant oil fraction by gas chromatography. Also each mass of soot fraction and sulfate fraction was measured as components of ISOF. The experiment was conducted at BMEP = 2.0 MPa as full load condition of the engine and changing EGR rate from 0% to 40 %.

Reduction of exhaust emissions and BSFC was studied for high pressure, wide range, and high EGR rates in a Super-clean Diesel six-cylinder heavy duty engine. The GVW 25-ton vehicle has 10.52 L engine displacement, with maximum power of 300 kW and maximum torque of 1842 Nm. The engine is equipped with high-pressure fuel injection of a 200 MPa level common-rail system. A variable geometry turbocharger (VGT) was newly designed. The maximum pressure ratio of the compressor is about twice that of the previous design: 2.5. Additionally, wide range and a high EGR rate are achieved by high pressure-loop EGR (HP-EGR) and low pressure-loop EGR (LP-EGR) with described VGT and high-pressure fuel injection. The HP-EGR can reduce NOx concentrations in the exhaust pipe, but the high EGR rate worsens smoke. The HP-EGR system layout has an important shortcoming: it has great differences of the intake EGR gas amount into each cylinder, worsens smoke.

In recent years, the dimethyl ether (DME) fuel has been attracting attention as an alternative engine in terms of diesel utilization. This is (a) because its cetane number is close to that of diesel fuel, (b) an innovative chemical process has been developed to produce DME efficiently from natural gas and coal, and (c) DME as a fuel has fewer environment-polluting characteristics than diesel fuel. Inasmuch as DME fuel have lower molecular weights, a molecular C-O bond, and are much more volatile or evaporative than diesel fuel, it is possible to control particulate matters much more easily when DME is used instead of diesel fuel. As for NOx, however, even when using DME, there still remain problems under stringent exhaust gas regulations. Developed and optimized accordingly has been the NOx storage-reduction (NSR) system, using the DME engine with a common-rail injection system. The NSR system is coated with an NOx storage catalyst principally comprised of Pt and Rh.

To establish NOx Storage Reduction(NSR) system, the effect of post fuel injection in exhaust pipe with rich spike on NOx conversion rate was investigated. With post fuel injection, a higher injection pressure and the rich spike close to the NSR catalyst (just before the NSR catalyst) shows better NOx reduction performance. Based on these results, exhaust emission was tested in transient driving mode (JE-05). In this driving mode test, it was possible to reduce NOx emission less than 0.5 g/kWh for only a 1% of fuel penalty controlling the rich spike injection precisely.

Effects of measurement method, coolant temperature and fuel composition on soot emissions were examined by engine experiments. By reducing the pressure fluctuation in the sampling line, the measured soot emissions with better stability and reproducibility could be obtained. With lower coolant temperatures, larger soot emissions were yielded at much advanced fuel injection timings. Compared to gasoline, soot emissions with a blend fuel of normal heptane, isooctane and toluene were significantly decreased, suggesting the amounts of aromatic components (toluene or others) should be increased to obtain a representative fuel for the predictive model of particulate matter in SIDI engines.