• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.102-109
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• 1994

As a fundamental study to apply high pressure injection system to direct injection diesel engine, fuel injection system and constant volume combustion chamber were made and the behaviors of evaporating spray with the variation of injection pressure and the ambient gas temperature were observed by using high speed camera, and the combusion characteristics with the variation of injection pressure and A/F ratio were analyzed. As injection pressure increases, spray tip penetration and spray angle increase and, as a results spray volume increases. This helps an uniform mixing of fuel and air. Spray liquid core length decreases as ambient gas temperature increases, while it decreases as injection pressure increases but the effect of ambient gas temperature is dorminant. As injection pressure increases, ignition delay is shortened and combustion rate being raised, maximum heat release rate increases. It become clear that High injection pressure has high level of potential to improve the performance of DI-diesel engine.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.3
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• pp.385-393
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• 1993

Injection processing of denture base resin was introduced by Pryer in 1942, in an attempt to reduce processing shrinkage. More recently a continuous-pressure injection type technique has been developed (SR-Ivocap, Ivoclar AG, Schaan, Liechtenstein.), and it reduced processing error and increased resin density. The purpose of this study was to compare tensile bond strength of heat-cured, cold-cured, and light-cured denture base resin bonded to continuous-pressure injection type resin. To know it, 60 cylindrical resin specimens were fabricated, and tensile bond strength were measured. The results were as follows : 1. The mean tensile bond strength bonded to continuous-pressure injection type resin was lower than bonded to conventional heat cured resin. But tensile bond strength of conventional heat cured resin bonding with light cured resin was lower than continuous-pressure injection type resin. 2. Of the tensile bond strength bonded to continuous-pressure injection type resin, tensile bond strength bonding with continuous-pressure injection type resin was the greatest(but not significantly different from bonding with conventional heat cured resin), followed by cold-cured, light-cured resin. 3. Of the tensile bond strength bonded to conventional heat cured resin, tensile bond strength bonding with conventional heat cured resin was the greatest and followed by continuous-pressure injection type resin, cold-cured resin, light-cured resin. According to these results, bonding of continuous-pressure injection type resin with conventional heat cured resin or continuous-pressure injection type resin is acceptable, but bonding with light-cured resin is questionable.

• Design & Manufacturing
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• v.2 no.1
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• pp.39-43
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• 2008

There occur not only many problems in the injection process but also low quality productivity due to the injection conditions of various injection factors. Injection molding process factors such as molding temperature, injection pressure, flow rate and flow velocity, must be controlled properly in filling and packing phases in the injection molding process. In this study, effects of these factors on the injection molding were investigated through the flow analysis for the holding pressure affecting cooling time. Results of this study would be helpful to setting of holding pressure for optimization of forming condition in order to reduce cooling time in injection molding.

• Journal of Power System Engineering
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• v.1 no.1
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• pp.42-51
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• 1997

In this study, in order to investigate the influence of cam profile on the injection rate, the characteristics of injection in PLN (pump - line - nozzle) diesel injection system were simulated. Six types of the profile of fuel cam were used for simulation. The maximum injection pressure and maximum injection rate of initial and end phase were analyzed to demonstrate the characteristics of injection. The mathematical model of the injection system and the computation results were verified by experimental results. Simulation results showed that the maximum injection pressure, maximum injection rate, injection quantity and pressure drop in the end phase were proportional to the velocity of fuel cam during the effective stroke.

• Journal of ILASS-Korea
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• v.17 no.4
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• pp.171-177
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• 2012

To understand oxygenated fuel characteristics including spray penetration length and spray angle at a real engine ambient pressure condition, DME was injected into a high pressure chamber by a piezo injector common rail system. The piezo injector common rail system was able to apply steady injection pressure, rapid response, and accurate injection quantity. Injection and ambient pressure were varied to confirm a relation with spray form. Using a direct photographing technique, development process of DME spray was captured. DME injection quantity was enlarged linearly as increasing of the injection pressure. In the high pressure chamber, when the injection pressure was enlarged the penetration length and velocity were increased due to a big momentum of fuel particle at the same ambient pressure. When ambient pressure was increased, the DME spray penetration length and velocity were decreased since the high ambient density of nitrogen was acted as a resistance. Although the ambient pressure and injection pressure were varied, each case of spray angle was almost same since the spray angle had a connection of the injector nozzle geometry.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.116-122
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• 2012

The purpose of this study is to investigate the overall spray behavior characteristics for various injection conditions in a gasoline direct injection(GDI) injector with multi-hole. The spray characteristics, such as the spray penetration, the spray angle, and the injection quantity, were studied through the change of the injection pressure, the ambient pressure, and the energizing duration in a high-pressure chamber with a constant volume. The n-heptane with 99.5% purity was used as the test fuel. In a constant volume chamber, the injected spray was visualized by the spray visualization system, which consisted of the high-speed camera, the metal-halide lamp, the injector control device, and the image analysis system with the image processing program. It was revealed that the injection quantity was mainly affected by the difference between the injection pressure and the ambient pressure. For low injection pressure conditions, the injection quantity was decreased by the increase of the ambient pressure, while it nearly maintained regardless of the ambient pressure at high injection pressure. According to the increase of the ambient pressure in the constant volume chamber, the spray development became slow, consequently, the spray tip penetration decreased, and the spray area increased. In additions, the circular cone area decreased, and the vortex area increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.162-173
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• 1998

The high pressure common rail injection system offers a high potential for improving emmisions and performance characteristics in large direct diesel engines. High pressures in the common rail with electronic control allows the fuel quantity and injection timing to be optimized and controlled throughout a wide range of engine rpm and load conditions. In this study, high pressure supply pump, common rail, pipes, solenoid and control chamber, and nozzle were modeled in order to predict needle lift, rate of injection, and total injected fuel quantity. When the common rail pressure is raised up to 13.0 ㎫ and the targer injection duration is 1.0ms, the pressure drop in common rail is about 5.0㎫. The angle of effective pressurization is necessary to be optimized for the minimum pump drive torque and high pressure in common rail depending on the operating conditions. The characteristics of injection were also greatly influenced by the pressures in common rail, the areas of the inlet and exit orifice of the control chamber.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.12
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• pp.100-106
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• 2008

In this paper, the injection molding process of automotive seat-back cover is analyzed in terms of simulation and of experiment. FE analysis was used to obtain molding conditions such as injection pressure, filling pattern, packing, shrinkage. Vacuum system for low pressure injection molding is developed in the experiment. Low pressure injection molded parts have been compared with conventional molded parts in terms of molding quality and mechanical properties. Based on the results, good product and the productivity improvement can be obtained in low pressure injection molding for automotive seat-back cover.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1436-1448
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• 2006

This paper describes the effects of injection rate shaping on the combustion, fuel consumption and emission of $NO_x$ and soot of a medium duty diesel engine. The focus is on the influence of four different injection rate shapes, square type 1, square type 2, boot and ramp, with a variation of maximum injection pressure and start of injection (SOI). The experiments were carried out on a 1 liter single cylinder research diesel engine equipped with an amplifier-piston common rail injection system, allowing the adjustment of the injection pressure during the injection event and thus injection rate as desired. Two strategies to maintain the injected fuel mass constant were followed. One where rate shaping is applied at constant injection duration with different peak injection pressure and one strategy where rate shaping is applied at a constant peak injection pressure, but with variable injection duration. Injection rate shaping was found to have a large effect on the premixed and diffusion combustion, a significant influence on $NO_x$ emissions and depending on the followed strategy, moderate or no influence on soot emission. Only small effects on indicated fuel consumption were found.

• Elastomers and Composites
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• v.52 no.4
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• pp.309-316
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• 2017

In injection molding, the quality of an injection molded product varies greatly depending on the molding conditions. Many researche studies have been conducted on the quality analysis of molded parts according to the molding conditions such as injection pressure, injection temperature, and packing pressure. However, there have not been many studies on the V/P switchover timing. It is known that when a large pressure is applied to a cavity in the packing phase, the cavity pressure is most affected by the packing pressure. In addition, depending on the position (timing) of the packing pressure, it can have a direct influence on quality based on the shrinkage and dimensions of the molded parts. In this study, the change in pressure profile in the cavity according to the V/P switchover position is confirmed. A CAE analysis program (Moldflow) was used to simulate and analyze two models using the PC and PBT materials. In order to compare these results with the actual injection molding results, injection molding was performed for each V/P switchover position, and the correlation between simulation and experiment, especially for the shrinkage of molded parts, was evaluated.