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The effects of injection system design, air/fuel ratio, coolant temperature and fuel volatility on engine-out hydrocarbon emissions, NOx emissions and cyclic variability have been studied in a prototype 1.8l lean-burn SI engine. The results have been compared with ILIDS measurements of in-cylinder spray characteristics made under similar conditions, to establish the degree to which variations in fuel spray formation correlate with engine performance. The lean-burn engine and the methodology of the combined study are described. The engine was found to exhibit a different behaviour when running lean compared to stoichiometric. When running lean, there was a negative correlation between steady-state engine-out NOx emissions and cyclic variability (COV of IMEP), and a positive correlation between steady-state engine-out hydrocarbon emissions and cyclic variability.

The effects of injection system design, air/fuel ratio, coolant temperature and fuel volatility on engine-out hydrocarbon emissions, NOx emissions and cyclic variability have been studied in a prototype 1.8l lean-burn SI engine. The results have been compared with ILIDS measurements of in-cylinder spray characteristics made under similar conditions, to establish the degree to which variations in fuel spray formation affect engine performance. The engine was found to exhibit a different behaviour when running lean compared to stoichiometric. In lean-burn operation, there was a clear tendency for the best performance to occur under operating conditions which produced charge stratification in the cylinder, whereas when the engine was run with a stoichiometric air/fuel ratio, the best performance was achieved under engine operating conditions which gave the most homogeneous charge in-cylinder.

Recently, numerous researches of overbased calcium sulfurized alkylphenates focused on their total base number (TBN) were reported. And it's well known that a increase of TBN(typically, greater than 300 mg KOH/g) was effective to reduce their cost. However, calcium sulfurized alkylphenates having a TBN greater than 300 have several problems on their unsatisfied performance, such as thermal stability. COSMO PETROTECH Co., COSMO RESEARCH INSTITUTE, and COSMO OIL Co. have developed a calcium sulfurized alkylphenate “PAD-450” having the TBN greater than 400mgKOH/g. “PAD-450” has similar performance with conventional calcium sulfurized alkylphenates (TBN =250mgKOH/g) on usual laboratory tests and a marine engine test. The innovational performance of PAD-450 is based on our specific procedure to increase TBN.

One outstanding feature of methanol as an alternative fuel for spark ignition engines is its very high antiknock characteristics. In this study, potential improvements in output power and thermal effiency that methanol offers for a supercharged high compression ratio S.I. engine as an automotive prime mover were investigated. They were compared with those of a naturally aspirated gasoline engine. As a result the effect of operating parameters such as supercharged boost pressure, charge temperature and exhaust back pressure on thermal efficiency and output power was clarified quantitatively. Next it was confirmed that a methanol fueled turbocharged 1.3 ℓ S.I. engine with high compression ratio of 11:1 achieved almost the same output performance as that of a gasoline fueled naturally aspirated 2.0 ℓ engine. This engine also realized a lean burn system with high compression ratio and low NO× characteristics of methanol and achieved extremely good roll economy.

Using five single-component, three dual-component and five full boiling range fuels, the relationship between engine startability under low temperature and fuel volatility was experimentally studied. The study was carried out through the analysis of fuel vaporization and mixture formation in the cylinder. The effect of other factors such as cranking speed, ignition timing and fuel quantity supplied to the cylinder on startability was also examined from the view point of fuel vaporization in the cylinder. A theoretical approach for estimating the startability with fuels of various volatility was attempted. Based on this estimation, the degree of cold startability deterioration with lower volatility fuels and the way to improve cold engine startability were discussed.

In the way to seek a marked reduction of NOx just by EGR which was proved to be the best answer from the past studies, this analytical study deals with combustion around the practical engine stability limit. The results show that practical engine operating stability limit with the four cylinder engine is determined by the occurrence of several percent of slow burn. Experiments applying short combustion duration (fast burn) showed that the fast burn in combination with heavy EGR improves engine stability and has a potential to achieve substantial reduction in NOx emission along with some improvement in fuel economy. This potential was also directed by mathematical model study. This fast burn concept was embodied in the newly developed Nissan Z Fast Burn Engine.