• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.115-122
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• 1999

A friction tester to measure friction force generated at the interface between the piston ring and the cylinder liner was developed. Modified piston ring is bar-shaped and 100mm long. Surface of the modified piston ring is machined by the profile grinding machine to be formed as a shape of an arc of a circle. Measured data are treated as mean effective friction force and power loss. From this test it can be confirmed that friction force is deeply affected by surface shape of the piston ring and viscosity of supplied oil. Friction force is deeply affected by surface shape of the piston ring and viscosity of supplied oil. Friction force is decreased and power loss is increased with increasing velocity. And it is known that region of mixed lubrication is broader than estimated with theoretical analysis. it is expected that this tester can be used as the optimization tool of the surface shape of the piston ring at the first stage of development of the piston rings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.12a
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• pp.63-69
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• 1993

In this paper the characteristics of Hydrostatic Bearing of piston of cylinder are investigated . The dynamic characteristic equations of piston considering both parallel and rotational motion and time dependent modified Reynolds Equation are analyzed and the dynamic pressure distribution of oil film is numerically calculated by perturbation method and finite difference method. and the atatic analysis is carried out. so, the influence of design parameter of piston on the characteristic of bearing is analyzed.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.5
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• pp.554-564
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• 2002

A newly designed combustion chamber of diesel engine with a modified piston crown was prepared for the purpose of investigation for reduction of NO emission. It was intended to realize 2-stage combustion that is to keep fuel rich condition during early stage of combustion and fuel lean condition during next stage. The engine was tested on various conditions concerning exhaust gas emissions especially about NO emission and simultaneously fuel consumption rate. It was found that the engine with 2-stage combustion type piston emits significantly low NO at various speed and torque compared with conventional engines, but it raised points at issue in CO and smoke emissions with fuel consumption rate. The increasing of injection pressure on 2 stage combustion type diesel engine affects on CO and smoke emission considerably to reduce but slightly on NO to increase. The effect of 2-stage combustion was better at low speed than at high speed.

• International Journal of Advanced Culture Technology
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• v.3 no.2
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• pp.132-137
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• 2015

The purpose of this paper was to investigate the effects of solution treatment time and Sr-modification on the microstructure and property of the Al-Si piston alloy. It was found that as-cast microstructures of unmodified and Sr-modified Al-Si alloys consisted of a coarse acicular plate of eutectic Si, $Cu_3NiAl_6$ and $Mg_2Si$ phases in the ${\alpha}$-Al matrix but different in size and morphology. Both size and inter-particle spacing of Si particles were significantly changed by increasing of the solution treatment time. After a short solution treatment, the coarse acicular plate of the eutectic Si appears to be fragmented. Fully modified microstructure of Sr-modified alloy can reduce the solution treatment time to shorter compared to unmodified alloy. The maximum of a peak hardness value is found in the very short solution treatment of both Al-Si piston alloys. Compared to 10 h solution treatment, the solution treatment of 2-4 h is sufficient to achieve appropriate microstructures and hardness. The short solution treatment is very useful to increase the productivity and to reduce the manufacturing cost of the Al-Si piston alloys.

• Journal of Drive and Control
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• v.16 no.2
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• pp.43-50
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• 2019

The objective of this study was to reverse engineer a swash plate type piston pump mounted on a wheeled armored vehicle and to analyze the structure of the pump case. From the analysis, the weak parts were identified and corrected in the final design. Each element corresponding to the piston pump case was analyzed. The analytical method was given static boundary conditions, load conditions and confirmed displacement, strain, stress, and safety factor. Plastic deformation and damage were also confirmed and the component elements redesigned through structural analysis Structural analysis and vibration analysis were carried out for the components of the piston pump case. The piston pump model was finally modified by structural analysis and vibration analysis results for each component assembly, and a prototype was designed. Durability test and environmental test were carried out and the test results satisfied all of the requirements. Therefore, the analytical method presented in this study can be utilized as a methodology for element component design in the development of various piston pumps.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.32-38
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• 2004

This study was performed to investigate the behavior of liquid and vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The conventional engine was modified as Central Injected DI gasoline engine with swirl motion. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze spray behavior and fuel distribution inside of cylinder using exciplex fluorescence method. Piston cavity geometries were set by Type S, M and L. The results obtained are as follows. In the spray formation after SOI, the cone angle and width of the spray were decreased at late injection timing. With a fuel injection timing of BTDC $180^{\circ}C$, fuel was not greatly affected in a piston cavity but generally distributed as homogeneous mixture in the cylinder. With a fuel injection timings of BTDC $90{\circ}C$ and $60^{\circ}C$, fuel mixture was widely distributed in near the cavity center. As a injection timing was late in the compression stroke, residual width of fuel mixture was narrow in proportion to piston cavity.

• Journal of the Korean institute of surface engineering
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• v.23 no.1
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• pp.34-43
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• 1990

Al-Si piston alloys such as AlS10CuMg have been anodized to examine apossibility of forming a hard film aat relatively higher temperatures compard with those in conventional sulfuric acid processes. Three types of electrolytes have been employed in this study ; electrolyte A(15% H2SO4, $0^{\circ}C$), electrolyte B(12% H2SO4, 1% oxalic, $10^{\circ}C$), electrolyte C(tartaric acid 125g/L+oxalic 75g/L+aluminum sulfate 225g/L, $25^{\circ}C$). Hard anodisine process in electrolyte B at a current density of 1.54A/dm2 produced a harder film of VHN 396 at a relatibely low film forming voltage compared with those obtained in other electrolyte at equivalent current density. A liner relationship between hardness and abrasion resistance exists for Al-Si piston alloys. The hardness of anodized film decreasees with increasing silicon content in Al-Si alloys and also with bath temperature. The film hardeness of Na-modified alloy os higher than that of P-modified alloy due to its finer microstructre. The film on the silicon phase in Al-Si alloys is observed to be formed by lateral growth of oxide film nucleated at surroundings.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.528-533
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• 1988

The assignment of boundary conditions for the piston thermal loading analysis in internal combustion engine has been tested using the thermal circuit method with an engine simulation program. In an attempt to examine the accuracy of the employed boundary condition, another thermal boundary condition has been sought for through the electrolytic tank analogue method. Comparison of calculated temperature distributions obtained from these two boundary conditions with measured temperature values reveals that the electrolytic tank analogue method gives excellent agreement. However, the thermal circuit method has been found to be reasonable for practical applications, if modified partially.

• Journal of Korea Foundry Society
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• v.13 no.3
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• pp.268-275
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• 1993

In gravity die casting, die cooling systems are frequently employed with water cooling to remove the heat of the solidifying metal. Thermal modeling is an important technique in mold design for improving the productivity of the process. Computer simulation system which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of cyclic gravity die casting. The pre-processor is used for mesh generation in a PC system. The modified finite difference method is adopted for the main solidification simulation algorithm during all the casting cycles. The post-processor graphically presents the simulation results. Several experiments in automotive cast piston were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. The effects of cycle number on solidification pattern are also studied. Several experimental results for the prediction of shrinkage defects are compared with calculated results.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.31-38
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• 2006

Cylinder liner rotation is a new concept for reducing piston assembly friction in the internal combustion engine. The purpose of cylinder liner rotation is to reduce the occurrence of boundary and mixed lubrication friction in the piston assembly. This paper reports the results of experiments to quantify the potential of the rotating liner engine. A GM Quad-4 SI engine was converted to single cylinder operation and modified for cylinder liner rotation. The hot motoring method was used to compare the friction loss between the baseline engine and the rotating liner engine. Additionally, tear-down tests were used to measure the contribution of each engine component to the total friction torque. The cycle-averaged motoring torque of the RLE represents a $23\~31\%$ friction reduction compared to the baseline engine for hot motoring tests. Through tear down tests, it was found that the piston assembly friction of the baseline engine is reduced from $90\%$ at 1200 rpm to $71\%$ at 2000 rpm through liner rotation.