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Technical Paper

Part 2: The Effects of Lubricating Oil Film Thickness Distribution on Gasoline Engine Piston Friction

2007-04-16
2007-01-1247
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.
Technical Paper

Measurement of Piston Skirt Oil-film Pressure under Piston Slap

2007-05-15
2007-01-2215
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.
Technical Paper

Direct Heat Loss to Combustion Chamber Walls in a D.I. Diesel Engine-Development of Measurement Technique and Evaluation of Direct Heat Loss to Cylinder Liner Wall

2007-09-16
2007-24-0006
The purpose of this study is to clarify the state of heat loss to the cylinder liner of the tested engine of which piston and cylinder head were previously measured. The authors' group developed an original measurement technique of instantaneous surface temperature at the cylinder liner wall using thin-film thermocouples. The temperature was measured at 36 points in total. The instantaneous heat flux was calculated by heat transfer analysis using measurement results of the temperature at the wall. As a result, the heat loss ratio to all combustion chamber walls is evaluated except the intake and exhaust valves.
Technical Paper

An Experimental Study on Phenomena of Piston Ring Collapse

2002-03-04
2002-01-0483
This study has been conducted aiming at an experimental verification of the ring collapse phenomena that occurs in a taper faced second ring of a direct fuel injection type truck diesel engine. The oil film thickness of the second ring, the ring axial motion and the inter-ring pressure have been measured under various operating conditions of engine. As a result, it is verified that the back pressure of the second ring becomes lower than the second land pressure, and that the second ring oil film becomes extremely thick temporarily where the second ring contacts with the ring groove upper surface. It is also verified that blow-by passes through the second ring where the oil film of the second ring becomes thick. Hence it is highly probable that the collapse of the second ring has occurred at that time.
Technical Paper

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

2001-03-05
2001-01-0566
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

The Effect of Crankshaft Offset on Piston Friction Force in a Gasoline Engine

2000-03-06
2000-01-0922
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.
Technical Paper

A Study of Abnormal Wear in Power Cylinder of Diesel Engine with EGR - Wear Mechanism of Soot Contaminated in Lubricating Oil

2000-03-06
2000-01-0925
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.
Technical Paper

Part 3: A Study of Friction and Lubrication Behavior for Gasoline Piston Skirt Profile Concepts

2009-04-20
2009-01-0193
This paper deals with the friction performance results for various new concept piston skirt profiles. The program was conducted under the assumption that friction performance varies by the total amount of oil available at each crank angle in each stroke and the instantaneous distribution of the oil film over the piston skirt area. In previous papers [1,2] it was that lower friction designs would be expected to show higher skirt slap noise. This paper discusses the correlation between friction and skirt slap for each new concept profile design. Finally, this paper explains the friction reduction mechanism for the test samples for each stroke of the engine cycle by observing the skirt movement and oil lubrication pattern using a visualization engine.
Technical Paper

Part 1: Piston Friction and Noise Study of Three Different Piston Architectures for an Automotive Gasoline Engine

2006-04-03
2006-01-0427
The objective was to rank piston friction and noise for three piston architectures at three cold clearance conditions. Piston secondary motion was measured using four gap sensors mounted on each piston skirt to better understand the friction and noise results. One noticeable difference in friction performance from conventional designs was as engine speed increased the friction force during the expansion stroke decreased. This was accompanied by relatively small increases in friction force during the other strokes so Friction Mean Effective Pressure (FMEP) for the whole cycle was reduced. Taguchi's Design of Experiment method was used to analyze the variances in friction and noise.
Technical Paper

HCCI Combustion Characteristics of Hydrogen and Hydrogen-rich Natural Gas Reformate Supported by DME Supplement

2006-04-03
2006-01-0628
Hydrogen is expected to be a clean and energy-efficient fuel for the next generation of power sources because it is CO2-free and has excellent combustion characteristics. In this study, an attempt was made to apply Homogeneous Charge Compression Ignition (HCCI) combustion to hydrogen with the aim of achieving low oxides of nitrogen (NOx) emissions and high fuel economy with the assistance of the di-methyl-ether (DME) fuel supplement. As a result, HCCI combustion of hydrogen mixed with 25 vol% DME achieved approximately a 30% improvement in fuel economy compared with HCCI of pure DME and spark-ignited lean-burn combustion of pure hydrogen under almost zero NOx emissions and low hydrocarbon (HC) emissions. This is attributed to control of the combustion process to attain the optimum onset of combustion and to a reduction of cooling losses.
Technical Paper

Oil Film Thickness Measurement and Analysis of a Three Ring Pack in an Operating Diesel Engine

2000-06-19
2000-01-1787
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.
Technical Paper

Heat Transfer into Ceramic Combustion Chamber Wall of Internal Combustion Engines

1986-09-01
861276
The authors developed the optimum thin film thermocouples in terms of materials, shape and dimensions to make instantaneous surface temperature and heat flux measurements of combustion chamber wall in internal combustion engines with accuracy by the computer analysis. And they succeeded to make thin film thermocouple in ceramic piston, by the application of the above technique. Then, the instantaneous surface temperature was measured to obtained the instantaneous heat flux on the ceramic plate fixed on top of the piston.
Technical Paper

Improvement of Piston Lubrication in a Diesel Engine By Means of Cylinder Surface Roughness

2004-03-08
2004-01-0604
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.
Journal Article

An Experimental Study on Relationship between Lubricating Oil Consumption and Cylinder Bore Deformation in Conventional Gasoline Engine

2009-04-20
2009-01-0195
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.
Technical Paper

Study on Mechanism of Backfire in Hydrogen Engines

1994-10-01
942035
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

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

1998-10-19
982660
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

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

1993-08-01
931811
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

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

2003-03-03
2003-01-0983
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

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 -

2003-03-03
2003-01-0982
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

Effect of Piston and Piston Ring Designs on the Piston Friction Forces in Diesel Engines

1981-09-01
810977
How much reduction in piston friction loss can be achieved by the piston design? Piston friction force measurements have been carried out using the measuring method developed by the authors to obtain the effects of piston clearance, surface roughness, lubricant and ring size and contact pressure on the piston friction forces. A particular emphasis is placed on the study of effects of the piston rings by the experimental and theoretical analyses, since friction forces of piston rings accounted for 3/4 or more of the total piston friction force.
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