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Technical Paper

Effects of Lubricating Oil Supply on Reductions of Piston Slap Vibration and Piston Friction

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.
Technical Paper

Development of a Technique to Predict Oil Consumption with Consideration for Cylinder Deformation - Prediction of Ring Oil Film Thickness and Amount of Oil Passing Across Running Surface under Cylinder Deformation -

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.
Technical Paper

The Effects of Crank Ratio and Crankshaft Offset on Piston Friction Losses

A study was conducted to understand the effects the specifications of the crank-slider mechanism have on piston friction losses. The information obtained through the study is believed to be useful information for reducing the piston friction. A single-cylinder spark-ignited gasoline engine was designed and constructed to have not only a real-time piston friction measurement system using the floating liner method, but also provisions to facilitate changing the specifications of the crank-slider mechanism. This paper describes the study results obtained under various engine-operating conditions and reports the parametric test results of three crank ratios and five crankshaft-offset amounts tested.
Technical Paper

Variation of Piston Friction Force and Ring Lubricating Condition in a Diesel Engine with EGR

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.
Technical Paper

The Effect of Oil Ring Geometry on Oil Film Thickness in the Circumferential Direction of the Cylinder

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.
Technical Paper

Variation of Piston Ring Oil Film Thickness in an Internal Combustion Engine - Comparison Between Thrust and Anti-Thrust Sides

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.
Technical Paper

Study on Mechanism of Backfire in Hydrogen Engines

In this study, the cause of backfire concerning an external mixture formation type hydrogen engine was clarified. It has been known that the maximum output power of the external mixture formation type hydrogen engine should be kept significantly low, because of backfire. Generally, the backfire of this type of hydrogen engine is caused by pre-ignition. In this type of hydrogen engine, pre-ignition occurred for a range of lean mixture. Under this study, therefore, the relationship between the occurrence of backfire and the temperature at the tip of the spark plug electrode, and the detection of the luminescence spectrum of the flame near the spark plug were examined and studied in relation to the spark plug ignition theory which appeared to be promising. Then the pre-ignition timing and location were studied by detecting the flame luminescence spectrum.
Technical Paper

A Study on the Mechanism of Backfire in External Mixture Formation Hydrogen Engines -About Backfire Occurred by Cause of the Spark Plug-

It is a well-known fact that the exhaust emission characteristics of hydrogen fueled engines are extremely good. The external mixture formation - a hydrogen fuel supply method - has the merit of practically zero NOx emission level in the lean mixture range with the excess air ratio λ set at 2.0 or greater as well as the merits of simple mechanism and easy operation. However, the practical use of such engines has been impeded partly due to the occurrence of backfire where the excess air ratio λ is 2 to 3. In order to allow the practical use of the hydrogen fueled engines with external mixture formation, it is vital to determine the causes of backfire and to establish proper countermeasures. It is found through a recent study conducted on the mechanism of backfire that the abnormal electric discharge in the intake stroke is one of the causes of backfire.
Technical Paper

Friction and Lubrication Characteristics of Piston Pin Boss Bearings of an Automotive Engine

The aim of this research was to analyze the lubrication conditions of piston pin boss bearings used in the press-fit piston pins of automobile gasoline engines. An original pin boss friction measuring device was developed and used to successfully obtain measurements. It was revealed that the friction force peaks twice every cycle at high engine loads, and non-fluid lubrication characteristics are displayed. The friction forces for various differing piston pins and pin boss bearings were analyzed, and it was shown that reducing piston pin length or thickness to reduce piston weight, or reducing the pin boss bearing clearance to reduce noise worsen the friction characteristics and increase the possibility of abnormal bearing friction as well as seizure.
Technical Paper

Effect of Piston Motion on Piston Skirt Friction of a Gasoline Engine

This study has been aimed at the reduction of the intense piston skirt friction force that appears in the expansion stroke out of all piston friction forces generated in gasoline engines. The friction characteristics at the piston skirt have been analyzed according to the measured results at piston friction forces and the shapes of wears at the piston skirt in actual engine operations. It is found from the above that the majority of the side force working on each piston is supported by the oil film on the skirt, while only some of the side force is supported by the portion in metallic contact with the cylinder. It is also found through experiments that the metallic contact portion has a great effect on the friction force at the skirt. The effect of piston posture in expansion stroke on the friction force has been also analyzed based on the measured results of piston slap motions.
Technical Paper

A Study of Decrease Oil Consumption for NSOR-Two-Ring Package Piston

Furuhama(1)* proposed the new two ring package consist of a pressure ring and a narrow single-rail oil ring (NSOR) in 1985. Number of studies(2) have been done for the purpose of reducing the oil consumption (OC) in this ring package. However, OC reduction problem has been still remaining to solve as only one serious problem of this ring package. The reasons of a larger OC in the new ring package than the conventional three ring has been hardly understood, considering the OC control ability on second ring in three ring package will not so large since the fact that the oil film thickness is thicker than that of the oil ring. In this study, the mechanism of OC increase in new ring package was found out at last, as a result, OC of new ring package piston was improved up to the same level of conventional three ring package piston.
Technical Paper

Heat Transfer into Ceramic Combustion Wall of Internal Combustion Engines

A thin film thermocouple with a high accuracy was developed by means of computer analysis, which allowed measurements of instantaneous temperatures and heat fluxes on combustion chamber walls. Conventional Al-alloy and ceramic plates were compared in terms of the heat loss at the upper surface of each piston during combustion, using a gasoline engine and a diesel engine in the series of experiments. It was found by the comparison that the ceramic plates subjected to higher temperatures had greater heat losses in both the gasoline and diesel engines contrary to the anticipation.
Technical Paper

Influence of Clearance Between Piston and Cylinder on Piston Friction

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.
Technical Paper

Low NOx Emission Automobile Liquid Hydrogen Engine by Means of Dual Mixture Formation

According to authors' previous research, high pressure hydrogen engines with direct injection right before TDC and spark ignition obtain high performance and eliminate almost. abnormal combustion. This study has clarified the mooted points in the flame propagation to adjacent jets and the control of the optimum spark timing and large NOx emissions even in leaner than excess air ratio of λ=2. Nitric oxides (NOx) is the only the pollutant in the exhaust gases emitted by hydrogen engines. It has been found that the NOx formation largely depends on the mixture formation method. In order to operate the engine in a small amount of NOx, an experimental study was carried out to investigate the reduction of NOx and the output power by using dual mixture formation method, external mixture formation and direct injection.
Technical Paper

Measurement of Piston-Skirt Deformation in Engine Operation by Means of Rotating Cylinder with Gap-Sensors

An unique measurement method was developed for measurement of the piston outer surface during the engine operation. The method was realized by embedding a gap sensor into a cylinder bore and by rotating the cylinder in the circumferential direction. By means of this method, interesting data of skirt deformation of a gasoline engine caused by temperature, pressure and the slap force were obtained.
Technical Paper

Effects of Flame Motion and Temperature on Local Wall Heat Transfer in a Rapid Compression-Expansion Machine Simulating Diesel Combustion

Local heat flux from the flame to the combustion chamber wall, q̇, was measured the wall surfaces of a rapid compression-expansion machine which can simulate diesel combustion. Temperature of the flame zone, T1, was calculated by a thermodynamic two-zone model using measured values of cylinder pressure and flame volume. A local heat transfer coefficient was proposed which is defined as q̇/(T1-Tw). Experiments showed that the local heat transfer coefficient depends slightly on the temperature difference, T1-Tw, but depends significantly on the velocity of the flame which contacts the wall surface.
Technical Paper

Effect of Hydrogen Jet on Mixture Formation in a High-Pressure Injection Hydrogen Fueled Engine with Spark Ignition

In order to establish hydrogen engines for practical use, it is important to overcome difficulties caused by unique characteristics of hydrogen fuel. A hydrogen engine with direct injection right before top dead center(TDC) and spark ignition has advantages such as prevention of abnormal combustion and realization of high power output near the stoichiometric air-fuel ratio, in comparison with an engine with external mixture. On the other hand, it has been pointed out that ignition and combustion for this type of hydrogen engines should be improved and that further studies on mixture formation of air and injected hydrogen are necessary for the improvement. For the direct injection hydrogen engine, mixture is formed both by air flow inside the combustion chamber and by injected hydrogen jet.
Technical Paper

Hydrogen Combustion Study in Direct Infection Hot Surface Ignition Engine

The hydrogen combustion characteristics have been studied in a late-injection (near TDC) hot surface ignition engine. As a supplemental experiment, the mode of combustion was observed in a constant volume combustion chamber by the schlieren method. Consequently the combustion process, that was the flame propagation initiated by a hot surface through heterogeneous hydrogen jets, was not the same as that of a diesel engine. The experimental results in test engine showed the optimum number of injection holes and the effect of intake air swirl for better mixture formation. It was observed that the combustion was frequently accompanied by non-negligible combustion pressure vibrations at all engine operating conditions.
Technical Paper

Development of a Hydrogen Powered Medium Duty Truck

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).
Technical Paper

Measurement of Cylinder Bore Deformation During Actual Operating Engines

One of the phenomena accompanying the lightweight/compact/high power output feature of engines is the cylinder bore deformation, which may readily cause increased oil consumption, gas leakage, unusual wear, scuffing, etc.. The authors have had experiences that piston rings had generated contact failure during engine operation (1)*. Such deformation is generated as a combination of the static deformation due to head bolt tightening, crankshaft installation, etc., and the deformation by the operating factors; thermal load and combustion pressure. Countermeasure of design have been made for the former (2)*, and prediction of the deformation during actual operating have been tried using FEM analysis, etc. for the latter (3)*. Therefore, the accurate measurement result have been required strongly, for a long time. But it could not be realized in the past.