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Ammonia is one of the most useful compounds that react with NOx selectively on a catalyst, such as V2O5-TiO2, under oxygen containing exhaust gas. However ammonia cannot be stored because of its toxicity for the small power generator in populated areas or for the diesel vehicles. A new concept for NOx reduction in diesel engine using ammonia is introduced. This system is constructed from the hydrogen generator by fuel reformer, the ammonia synthesizer, SCR catalyst for NOx reduction and the gas injection system of reformed gas into the cylinder. Experimental results show that, the SCR catalyst provides a very high rate of NOx reduction, reformed gas injection into cylinder is very effective for particulate reduction. WHEN CONSIDERING INTERNAL COMBUSTION ENGINES of the 1990's the question of how to harmonize the engine with the natural environments is one of the greatest problems. The internal combustion engine changes a substance into energy via its explosive combustion.

Exhaust-gas recirculation (EGR) causes the piston rings and cylinder liners of a Diesel engine to suffer abnormal wear on the sliding parts. The present study aimed at making clear such abnormal wear structurally by examining the state of lubrication of the piston with a floating liner method, observing directly a visualized cylinder and experimenting on a Diesel engine for wear. As a result, it was confirmed that soot in EGR gas would change a lot the characteristics of the piston friction force. There are two mechanisms: one directly enters the sliding surfaces, and the other enters the ring rear, applying more load to them. It was also confirmed that the level of wear on the piston ring would vary to a large extent as the state of lubrication changed.

Offsetting the crankshaft axis with respect to the cylinder axis has been thought to be a method to reduce piston side force[1]. Hence the piston friction is expected to be reduced. An automotive manufacturer has already used the crankshaft offset for a production gasoline engine to improve fuel economy. The authors have conducted research into the effect of crankshaft offset on the piston friction. A single-cylinder engine was modified to have a crankshaft offset. Piston frictional force was measured in real-time by using a floating liner method. In addition, laser-induced fluorescence (LIF) technique was employed to measure oil film thickness on the piston skirt area, and a gap sensor was used to measure piston motion. As a result, the authors concluded that the effect of crankshaft offset on piston friction could not be explained only by its effect on the piston side force. In accordance with the measurement results, crankshaft offset changed piston slap motion.

An ultra-lightweight piston and conrod without small end bush, combined with a ring pack designed for minimized friction is analyzed and demonstrated as an optimized power cylinder system in a high performance gasoline engine. Component and system analysis for optimizing the design, materials used and design features are reviewed, along with durability, NVH and friction testing results. Results are compared to other benchmark power cylinder system components for weight, performance and value.

Due to increasing economic and environmental performance requirements of internal combustion engines, piston manufacturers now focus more on lower friction designs. One factor strongly influencing the friction behavior of pistons is the dynamic interaction between lubricating oil, cylinder bore and piston. Therefore, the dynamic effect of the oil film in the gap between the liner and piston has been studied, using a single cylinder engine equipped with a sapphire window. This single cylinder engine was also equipped with a floating liner, enabling real-time friction measurement, and directly linking the oil film behavior to friction performance of pistons.

Frictional force as a function of crank angle of a piston assembly and piston rings alone were measured after the following devices were developed. (1) A gas sealing device that did not affect the measuring values. (2) A device to minimize the effect of gas pressure on the cylinder head and block deformations. (3) A device to minimize the effect of piston slap force. From the measurement of the frictional force diagrams the following characteristics have been found. (1) Lubricating oil temperature has the greatest effect upon the frictional loss of the piston. (2) Piston friction does not increase to the point of becoming proportional to the engine speed. (3) Friction in the expansion stroke increases at high load by the piston slap phenomenon. But the increase of total losses are small because the duration is short. (4) Piston rings account for the majority of the entire frictional force of the piston.

It is desired to minimize clearance between the piston and the cylinder to reduce noise and suppress vibration. Although significant effort has been made for this purpose, increased piston friction force and the occurrence of seizure still prevent the ideal clearance from being realized. In order to determine the lower limit of the piston clearance, it is crucial to clarify the following unknowns; which part of piston contributes to friction increase as the piston clearance is decreased, during which phase of the piston motion the friction increase occurs, and how the piston clearance affects lubrication phenomena. Measurements of piston friction force under operating conditions were made by applying the Floating Liner Method(1),(2)* to a single-cylinder test gasoline engine. The measurement revealed how the piston friction varied as the piston clearance decreased. Lateral motion of the piston was also measured.

Aiming at the improvement in piston lubrication and the reduction of piston friction loss under this study, piston friction forces of cylinders with different surface roughness and treatment methods have been measured by means of a floating liner method, and the piston surface conditions have been also observed. As a result, it is found that the piston lubrication can be markedly improved by reducing the cylinder surface roughness. It is also verified that the deterioration in lubrication can be reduced even if some low viscosity oil is used, and the effect on the friction loss reduction becomes greater by reducing the piston surface roughness. On the other hand, it is found that many small vertical flaws are generated on the cylinder surface by reducing the surface roughness. In order to cope with this problem, etching and DLC (Diamond Like Carbon) coating have been tested as the surface treatments. As a result, it is confirmed that DLC coating is effective for the above.

This study has been conducted aiming at reductions of piston slap noise and piston friction loss, and effects of lubricating oil supply between the piston skirt and cylinder on diesel engine have been verified through a series of experiments. Namely, lubricating oil was supplied forcibly into the piston skirt from outside of engine, and its effects on the cylinder block vibration, piston friction force, slap motion and oil consumption have been measured. As a result, it has been verified that the supply of a small amount of oil (6mL/min) to the piston skirt reduces about 50 % of the block vibration caused by the piston slap motion in idling operation, and about 20 % of the piston friction loss in full load operation. Furthermore it has verified without giving any significant adverse effect on oil consumption.

Although various factors affecting oil consumption of an internal combustion engine can be considered, a technique to predict the amount of oil consumed within a cylinder that passes across a running surface of a ring was developed in this study. In order to predict the effect of cylinder deformation on oil consumption, a simple and easy technique to calculate the oil film thickness in deformed cylinder was proposed. For this technique, the piston ring was assumed to be a straight beam, and the beam bends with ring tension, gas pressure, and oil film pressure. From the calculated oil film thickness, amount of oil passing across the running surface of the TOP ring and into the combustion chamber was calculated. The calculated results were then compared to the oil film thickness of the ring and oil consumption measured during engine operation, and their validity was confirmed.

It is well known that lubricating oil consumption (LOC) is much affected by the cylinder bore deformation occurring within internal combustion engines. There are few analytical reports, however, of this relationship within internal combustion engines in operation. This study was aimed at clarifying the relationship between cylinder bore deformation and LOC, using a conventional in-line four-cylinder gasoline engine. The rotary piston method developed by the author et al. was used to measure the cylinder bore deformation of the engine’s cylinder #3 and cylinder #4. In addition, the sulfur tracer method was applied to measure LOC of each cylinder. LOC was also measured by changing ring tension with a view to taking up for discussion how piston ring conforms to cylinder, and how such conformability affects LOC. Their measured results were such that the cylinder bore deformation was small in the low engine load area and large in the high engine load area.

Exhaust-gas recirculation (EGR) causes the piston ring and cylinder liners of a diesel engine to suffer abnormal wear. The present study aimed at making clear the mechanism of wear which is induced by soot in the EGR gas. The piston ring has been chrome plated and the cylinder was made of boron steadite cast iron. Detailed observations of the ring sliding surfaces and that of the wear debris contained in lubricating oil were carried out. As a result, it was found that the wear of the top ring sliding surfaces identify abrasive wear without respect to the presence of EGR by steadite on the cylinder liner sliding surface. In addition, it is confirmed in a cutting test that soot mixed lubricating oil improved in performance as cutting oil. Based on these results, we proposed the hypothesis in the present study that ring wear is accelerated at EGR because abrasive wear increases due to a lot of soot mixed into lubricating oil improving the performance of lubricating oil as cutting oil.