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The test engine was a turbocharged 10.5L engine with an intercooler. A performance target was set at a rated power of 300 kW (BMEP = 1.7 MPa) and peak torque of 1842 Nm (BMEP = 2.2 MPa). Emission targets were set at a level of near future and stringent regulation standards in Japan. The engine was equipped with new technologies such as a high pressure common rail system, FCD piston, a high pressure ratio VGT and an aftertreatment system. The high and low pressure loop EGR system was installed and this system with a VGT had a high performance and could increase an EGR rate in order to reduce BSNOx while maintaining the satisfied BSFC and PM performance simultaneously not only in the steady state condition but also in the transient condition.

Cycle-resolved residual gas fraction measurements were made inside a heavy-duty diesel engine using an infrared absorption method. An in situ laser infrared absorption method was developed using an optical fiber sensor and a 4.301-μm quantum cascade laser (QCL) as the light source. We discuss the feasibility of obtaining in situ CO2 concentration measurements inside the engine combustion chamber using the newly developed optical fiber sensor system. Lambert–Beer’s law can be applied for the case of a single absorption line of CO2, and the dependence of the CO2 molar absorption coefficient on the ambient pressure and temperature of was determined using a constant volume vessel. This coefficient decreased with increasing pressure, indicating almost constant at pressures over 1.0 MPa. CO2 concentration measurements were made in a compression–expansion engine in order to calibrate the measurement system. The feasibility of the optical fiber sensor system was then investigated in a heavy-duty diesel engine. We were able to measure the CO2 concentration inside the combustion chamber under various engine load conditions and were able to determine the internal exhaust gas recirculation (EGR) ratio. This measurement technique proved to be valuable in obtaining the cycle-to-cycle CO2 concentration of the residual gas in a heavy-duty diesel engine.

Heavy-duty diesel engines have adopted numerous technologies for clean emissions and low fuel consumption. Some are direct fuel injection combined with high injection pressure and adequate in-cylinder air motion, turbo-intercooler systems, and strong steel pistons. Using these technologies, diesel engines have achieved an extremely low CO 2 emission as a prime mover. However, heavy-duty diesel engines with even lower NOx and PM emission levels are anticipated. This study achieved high-boost and lean diesel combustion using a single cylinder engine that provides good engine performance and clean exhaust emission. The experiment was done under conditions of intake air quantity up to five times that of a naturally aspirated (NA) engine and 200 MPa injection pressure. The adopted pressure booster is an external supercharger that can control intake air temperature. In this engine, the maximum cylinder pressure was increased and new technologies were adopted, including a monotherm piston for endurance of P max = 30 MPa. Moreover, every engine part is newly designed. As the boost pressure increases, the rate of heat release resembles the injection rate and becomes sharper. The combustion and brake thermal efficiency are improved. This high boost and lean diesel combustion creates little smoke; ISCO and ISTHC without the ISNOx increase. It also yields good thermal efficiency.

An ignition and combustion model has been developed to predict the heat release rate in direct injection compression ignition engines employing very early injection timing. The model describes the chemical reactions, including low-temperature oxidation. The KIVA II computer code was modified with the present ignition and combustion model. The numerical results indicate that the model developed in this work reproduces major features of two-stage autoignition, as well as experimentally observed trends in NOx and unburned fuel emissions. The computational results show that fuel injection timing significantly influences NOx emissions. Results also indicate that fuel droplets that enter the squish region possibly become unburned fuel emissions. Some graphical results demonstrate the relationships among the in-cylinder fuel spray distributions, fuel-air equivalence ratio, temperature, and mass fractions of NO and unburned fuel.

Recently, pre-mixed lean mixture combustion has attracted attention, and many researchers are investigating compression ignition of a pre-mixed lean mixture. Previous research in our laboratory has shown that low NOx emission combustion is obtained by PREDIC (PREmixed lean DIese1 Combustion). However some problems still remain, such as higher fuel consumption, a lack of ignition timing control, a large increase in THC and CO, compared to conventional diesel combustion. The output limit of PREDIC is about 50% of conventional diesel combustion. So in order to increase the PREDIC engine output, supercharging was adopted. It was resulted that the power output was higher and the fuel consumption was better than the conventional natural aspiration diesel engine using supercharging. The numerical simulation analysis shows that NOx was produced at rich mixture area because of lower spray penetration under high density conditions. As the result, the high injection rate is effective to make a lean mixture.