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Technical Paper

Effects of EGR Constituents and Fuel Composition on DISI Engine Knock: An Experimental and Modeling Study

The use of exhaust gas recirculation (EGR) in spark ignition engines has been shown to have a number of beneficial effects under specific operating conditions. These include reducing pumping work under part load conditions, reducing NOx emissions and heat losses by lowering peak combustion temperatures, and by reducing the tendency for engine knock (caused by end-gas autoignition) under certain operating regimes. In this study, the effects of EGR addition on knocking combustion are investigated through a combined experimental and modeling approach. The problem is investigated by considering the effects of individual EGR constituents, such as CO2, N2, and H2O, on knock, both individually and combined, and with and without traces species, such as unburned hydrocarbons and NOx. The effects of engine compression ratio and fuel composition on the effectiveness of knock suppression with EGR addition were also investigated.
Journal Article

Effects of High Boiling Point Fuel Additives on Deposits in a Direct Injection Gasoline Engine

The effects of high boiling point fuel additives on deposits were investigated in a commercial turbocharged direct injection gasoline engine. It is known that high boiling point substances have a negative effect on deposits. The distillation end points of blended fuels containing these additives may be approximately 15°C higher than the base fuel (end point: 175°C). Three additives with boiling points between 190 and 196°C were examined: 4-tert-Butyltoluene (TBT), N-Methyl Aniline (NMA), and 2-Methyl-1,5-pentanediamine (MPD). Aromatics and anilines, which may be added to gasoline to increase its octane number, might have a negative effect on deposits. TBT has a benzene ring. NMA has a benzene ring and an amino group. MPD, which has no benzene ring and two amino groups, was selected for comparison with the former two additives.
Technical Paper

Combustion Development to Achieve Engine Thermal Efficiency of 40% for Hybrid Vehicles

In recent years, enhancing engine thermal efficiency is strongly required. Since the maximum engine thermal efficiency is especially important for HVs, the technologies for improving engine thermal efficiency have been developed. The current gasoline engines for hybrid vehicles have Atkinson cycle with high expansion ratio and cooled exhaust gas recirculation (EGR) system. These technologies contribute to raise the brake engine thermal efficiency to more than 38%.In the near future the consumers demand will push the limit to 40% thermal efficiency. To enhance engine thermal efficiency, it is essential to improve the engine anti-knock quality and to decrease the engine cooling heat loss. To comply with improving the anti-knock quality and decreasing the cooling heat loss, it is known that the cooled EGR is an effective way.
Technical Paper

The Effect of Fuel Compounds on Pre-ignition under High Temperature and High Pressure Condition

Turbocharged (TC) engines have been introduced these days to improve the fuel economy. It is considered that one possible issue of the TC engine is a pre-ignition at high engine speed because of high temperature and high pressure in the combustion chamber. This study shows the effect of fuel compounds on pre-ignition at 4400rpm. The experimental engine is a naturally-aspirated (NA) engine which is customized to imitate the cylinder temperature and pressure of TC engines. It is known that research octane number (RON) describes anti-knock quality well. Meanwhile the results show that pre-ignition characteristic at high engine speed is dominated by motor octane number (MON) and auto-ignition temperature (AIT) rather than RON.