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The aim of this work is to investigate the possibility of heat insulation by “Temperature Swing”, that is temperature fluctuation, on combustion chamber walls coated with low-heat-conductivity and low-heat-capacity materials. Adiabatic engines studied in the 1980s, such as ceramic coated engines, caused constantly high temperature on combustion wall surface during the whole cycle including the intake stroke, even if it employed ceramic thermal barrier coating methods. This resulted in increase in NOx and Soot, decrease in volumetric efficiency and combustion efficiency, and facilitated the occurrence of engine knock. On the other hand, “Temperature Swing” coat on the combustion chamber walls leads to a large change in surface temperature. In this case, the surface temperature with this insulation coat follows the transient gas temperature, which decreases heat loss with the prevention of intake air heating, and also which is expected to prevent NOx and Soot from increasing.

The lean combustion of an SI engine has been recognized as one of the most promising methods for further improvement of fuel economy. There has been, however, difficulty in extending the lean misfire limit enough to realize NOx emission levels below the mandatory level and still keep satisfactory driveability. A simulation study has been carried out to search for the possibility of getting better fuel economy under the constrainsts of NOx emission and driveability. To realize the optimum calibration, the lean misfire limit has been extended by the introduction of (1) high swirl and high combustion chamber turbulence through the use of a helical port with an unique swirl control valve, (2) a newly developed ZrO2 lean mixture sensor and (3) the multi-point fuel injection with sophisticated control. A very good fuel economy level of 17.0 km/1 (Japanese 10 mode) has been accomplished while still meeting the NOx emission cycle regulation of 0.25 g/km.

To improve fuel efficiency of engines, cooling heat loss is one of the most dominant losses among the various engine losses to reduce. The present work proposes a new heat insulation concept in combustion chamber, "TSWIN (Thermo-Swing Wall Insulation Technology)" that can reduce heat loss to the coolant without any sacrifice in other engine performances. Surface temperature of insulation coat on combustion chamber wall changes rapidly, according with the fluctuating temperature of in-cylinder gas. Reduced temperature differences between them lead to lower heat transfer. During the intake stroke, surface temperature of the insulation coat goes down rapidly, and prevents intake air heating. To realize the scheme mentioned above, a new insulation material with both low thermal conductivity and low volumetric heat capacity, "SiRPA (Silica Reinforced Porous Anodized Aluminum)" was developed and applied on the top surface of the piston.

Some magnesium detergents in engine oil are reported to form sludge of needle crystals in the presence of carbon dioxide and water We tried to reproduce needle crystals in a beaker test and studied factors in needle crystal formation by magnesium detergents We found that overbased components of magnesium detergents dissolved in carbonic acid water formed needle crystals recrystallizing We also found the quantities of needle crystals increased when both carbon dioxide and water content in oil increased Moreover we clarified the quantities and sizes of needle crystals differed by magnesium detergents