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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.

This paper describes a measurement method using laser induced fluorescence we have developed for simple simultaneous measurements of piston ring oil film thickness at plural points for internal combustion engines. The findings obtained by the measurements of oil film thickness on both thrust and anti-thrust sides of the piston for a mono-cylinder compact diesel engine using this new measurement method are also discussed in this paper. One of main findings is that the oil film thickness of each ring on both sides differs markedly in terms of the absolute value and the stroke- to-stroke variation. It is found that this difference in oil film thickness is caused by the difference in the amount of lubricating oil supplied to the oil ring, and the effect is greater than that of engine speed or load.

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.

This paper describes measurements of oil film thickness of piston ring packages which have different oil control rings. The oil film thickness measurements were taken at three points, namely, the piston thrust side, front side and rear side, by the Laser Induced Fluorescence Method(LIF). One of the main findings is that the oil film thickness on the thrust side varies greatly from cycle to cycle, while cyclic variations are smaller on the front and rear sides. This difference is due to the smaller inclination of the oil control rings on the front and rear sides, compared with that on the thrust side. It is also found that oil consumption has a good correlation with oil film thickness on the thrust side and that the thrust side oil film thickness becomes thinner as the oil ring becomes narrower.

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.

Oil film thicknesses of the piston top ring and the second ring of a truck diesel engine have been measured simultaneously by embedding capacitance type clearance sensors in the ring sliding surfaces. Owing to the above, several phenomena such as the variation in oil film thickness of each ring in one cycle, correlation between the rings, difference in oil film thickness between the thrust and counter thrust-sides, effects of engine operating conditions on oil film thickness, etc. have been determined. Efforts have been also made to analyze the causes of such phenomena according to the measured results of piston slap motion and ring motions, and the calculated results of oil film thickness.

Surface scuffing related to gas nitrided piston rings is attracting more attention as the effective cylinder pressure is increased in the recent years. However, the mechanism behind scuffing induced in long-term operations remained unknown. This study focuses on clarifying the mechanism behind scuffing related to gas nitrided piston rings. In addition, application of a thin composite plated surface film containing dispersed particles is proposed as an effective measure for preventing surface scuffing during long-term operations. Furthermore, factors enabling maintenance of high scuffing resistance on the ring surface after the thin plated composite film wears off and the underlying nitrided surface is exposed were analyzed. The dominant factor was discovered to be the difference in the resulting sliding surface profile, after initial wear, between a ring surface with composite plating and a ring surface with only gas nitriding treatment.

Using small thin-film pressure sensors deposited onto a piston skirt surface, oil-film pressure on the piston skirt surface is measured when piston slap noise is generated without affecting the surface geometry, stiffness and mass of the piston. Under a no-load firing engine condition and at low temperature, the measured oil-film pressure corresponded well to the measured acceleration of the cylinder liner, which is indicative of piston slap noise, confirming the validity of the present method. Moreover, the oil-film pressure distribution on the skirt surface was measured for different engine speeds and piston pin offsets, which enabled more insight to be provided into piston secondary motion than that by considering the effects of cylinder liner acceleration.

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.

A recent increase in detergent additives to gasoline has resulted in an increase in the accumulation of deposits inside the engine's combustion chamber (this type of deposit will be hereinafter referred to as “CCD”;Combustion Chamber Deposit). Along with this tendency, authors have observed an engine noise generated during warm up, which may be attributable to the CCD accumulation. It was reported that the engine noise was identified as carbon knocking caused when the piston and cylinder head physically come in contact because of these CCDs(1X2) This paper deals with another noise generated by the CCD trapped between the piston ring and piston ring groove.

To reduce the oil consumption in diesel engines, the combination of top ring gap clearance (C1) and second ring gap clearance (C2) (ring gap balance) was applied. The effect of the ring gap balance on piston ring axial motion and second land pressure was observed and factors to control oil consumption were analyzed. The authors obtained a technique to reduce oil consumption by decreasing second land pressure and thus making second ring liable to lift off. Blow up gas was significantly concerned about oil consumption of blow-by gas.

Today preservation of the global environment is an international challenge, and air pollution has attracted more concern than ever. Especially, pollution due to exhaust emission from automobiles is a serious matter, and among others, the improvement of exhaust emission is urgent. For this purpose, regulations have been tightened on exhaust emission such as particulate control and NOx control. Thus, it is essential for oil consumption of diesel engines to reduce oil consumption and employ Exhaust Gas Recirculation (EGR), and piston rings are the important key to solve these problems. This paper clarifies the effect of top rings, among piston rings, on oil consumption through engine tests and theoretical calculation of oil film thickness, and suggests techniques to reduce 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.

Considerable amount of research work on hydrogen fueled engines has been conducted for 17 years in Musashi Institute of Technology. The primary purpose of the research has been to develop a hydrogen powered autmobile, and in order to realized it, various innovations have been applied and tested. The newest outcome of this 17 years research was Musashi-7 Track, which demonstrated its performance in Innovation vehicle Design Competition held in Vancouver in July 1986. Musashi-7 Track was a modified medium duty truck, which was originally made by Hino Motors, and had a hydrogen powered engine. The track was equipped with 150 ℓ liquid hydrogen (LH2) tank and 8 MPa high pressure LH2 pump. The pump delivered 8 MPa high pressure hydrogen gas to the engine and the fuel was injected to a hot surface igniter in DI combustion chamber. This type of hydrogen enigne has following advantages. Firstly, fuel corrier weight and volume can be much smaller than those of metal-hydrides (MH).

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.