• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.1
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• pp.71-76
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• 2002

Because the driving time is increased under the low speed by rapidly increasing of vehicles, this paper is presented a new ignition control system for improvement the fuel economy, which only some of cylinders are using under the idle status or low speed and preserving the engine rpm. is applicable to effective in fuel economy. An actual hardware was made to prove this new control system. The developed variable cylinder engine concentrated the heat neat the cylinders in idle status or low speed, so there was a problem in re-ignition. It was the reason of a lot of exhaust gas, high fuel consumption and instability of engine revolution. In this paper, in order to solve above problem to show the improvement fuel economy using the new ignition control system and valve opening period at idle status of low speed.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.695-703
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• 2000

The purpose of this study was to evaluate the effects of fabrication and tightening methods of gold cyliner on the preload of the standard abutment. Three linear strain gauges (KFR-02N-120-C1-23, Kyowa, Japan) were mounted longitudinally on the 5.5mm Standard abutment (Nobel Biocare, Sweden) and three kinds of gold cylinders such as, as-received gold cylinder, gold cylinder after casting, and plastic cylinder after casting with type IV gold alloy were connected over the top of the standard abutment. Two kinds of tightening methods, such as manual torque with handhold screwdriver and electronic torque using Electronic torque controller were used to generate preload on the abutment. The result were as follows; 1. The preload generated by tightening cast plastic cylinder with handhold screw driver, was the lowest among the six groups. 2. The preload generated by cast plastic cylinder was lower than those by gold cylinders regardless of the tightening methods. 3. The electronic torque controller produced higher torque values than the handheld screwdriver.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1672-1679
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• 2002

This paper provides an engineering J estimation equation for cylinders with finite internal axial surfacecracks under internal pressure. The proposed equation is the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-O) materials. Based on detailed 3-D FE results using deformation plasticity, plastic influence functions for fully plastic J components are tabulated for practically interesting ranges of the mean radius-to-thickness ratio, the crack depth-to-length ratio, the crack depth-to-thickness ratio. the strain hardening index for the R-O material, and the location along the semi-elliptical crack front. Based on tabilated plastic influence functions, the J estimation equation along the crack front is proposed and validated for R-O materials. Good agreements between the FE results and the proposed J estimation provide confidence in the use of the proposed method to elastic-plastic fracture mechanics of pressurized piping.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2442-2449
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• 2002

This paper provides an reference stress based J estimation equation fur cylinders with finite internal axial surface cracks under internal pressure. In part 1, the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-0) materials is proposed. In this paper, the developed CE/EPRI -type solutions ale then re-formulated based on the reference stress concept. Such a re-formulation provides a simpler equation for J. estimation are then further extended to combined internal pressure and bending. The proposed reference stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress-strain data for a Type 304 stainless steel. Good agreement between the FE results and the proposed reference stress based J estimations provides confidence in the use of the proposed method to elastic -plastic fracture mechanics of pressurised piping.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.877-883
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• 1987

A new improved inviscid separation model to calculate the mean flow past circular cylinders is proposed. The wake region is modeled by a pair of vortex sheets which emerge from the separation points and are allowed to move freely with the local stream. The vortex strength assumes a constant value for some initial distance which is related to the pressure drag and gradually decreases to zero as the sheet moves farther away from the body. This vorticity distribution automatically takes care of the length parameter which has been one of the deficiencies in the existing models. The procedure is tested against various experimental data and the agreement is quite good for both sub and super-critical regimes. The comparison with an existing model is also given.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.725-731
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• 1985

In this study the rigid-plastic finite element method is used in order to study the deformation characteristics of solid cylinder upsetting. The effects of friction and aspect ratios on the effective strain distribution, axial stresses at the die-material interface, radial displacements, strain components, grid distortion on the meridional cross-section and gradual changes of outer profile are studied analyzed and compared with the experiments for commercially pure aluminum and .alpha.-brass. The agreement between numerical (or theoretical)and experimental results is shown to be acceptable for the engineering purpose.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1630-1636
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• 2003

Automobile companies and research institutions in leading automobile-manufacturing nations have recently been very active with research regarding the HCCI engine for use in future vehicles. Because HCCI engines take advantage of high compression ratio and heat release rate, they exhibit high efficiency found in compression ignition engines. HCCI engines also utilize a lean air/fuel ratio resulting in low emissions of NO$_{x}$ and PM (particulate matter). The objective of this research is to determine the effects of EGR rate on the combustion processes of HCCI. for this purpose, a 4-cylinder, compression ignition engine was converted into a HCCI engine, and a heating device was installed to raise the temperature of the intake air and also to make it more consistent. In addition, a pressure sensor was inserted into each of the cylinders to investigate the differences in characteristics among the cylinders. The experimental study of the effects of EGR rate on various gas emissions, engine performance, etc. should prove to be a valuable source of information for the development of the HCCI engine.e.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.79-86
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• 2000

The effects of recirculated exhaust gas on the wears of piston and piston rings were investigated by the experiment with a two-cylinder, four cycle, indirect injection diesel engine operating at an engine load of 75% and an engine speed of 1600 rpm. For the purpose of comparison between the wear rates of two cylinders with and without EGR, the recirculated exhaust gas was sucked into one of two cylinders after the soot contenets in exhaust emissions were removed by an intentionally designed cylinder-type scrubber equipped with 6 water injectors(A water injector has 144 nozzles of 1.0 mm diameter), while only the fresh air was inhaled into the other cylinder. These experiments were carried out on the fuel injection timing fixed at 15.3$^{\circ}$ BTDC. It was found that the wear rate of piston skirt with EGR increased a little bit, but the piston head diameter increased, rather than decreased, owing to soot adhesion and erosion wear, and especially larger with EGR, and that the wear rates of the top and second piston ring(compression ring)thickness with EGR were more than twice the wear rate of top ring in case of no EGR, but the wear rate of oil rings thickness without EGR increased greater than that with EGR.

• Journal of Biosystems Engineering
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• v.16 no.2
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• pp.142-147
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• 1991

Because combine cylinders account for up to 80 percent of the power requirements to harvest grain, it is important to have a reliable method to predict and analyze power consumption. An equation was derived to meet the prediction needs. The equation contains the variables number of bars on the cylinder, concave clearance, concave length, thickness of the feed material, feed rate, and cylinder speed. Indirectly, cylinder diameter was also considered. The derived equation was verified to be a reliable function for three of the variables and the equation was judged to be a reliable power prediction equation.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.34-39
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• 2006

The flow forming has been used to produce long thin walled tube parts, with reduced forming force and enhanced mechanical for a good finished part, compared with other method formed parts. Especially, the flow forming is suitable for making high precision thin walled cylinders, such as rocket motor cases, combustion chamber, hydraulic cylinders and high-pressure vessels and so on. In this paper, finite element analysis of three-roller forward and backward flow forming for combustion chamber is carried out to study effects of forming depth and feed rate on forming force. The axial and radial forming forces of forward flow forming on several forming depth and feed rate conditions are compared with those of backward flow forming.