• Journal of ILASS-Korea
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• v.14 no.3
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• pp.109-116
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• 2009

The purpose of this study is the experimental and numerical investigation on the DME spray characteristics in the combustion chamber according to the injection timing in a common-rail injection system. The visualization system consisted of the high speed camera with metal halide lamp was used for analyzing the spray characteristics such as spray development processes and the spray tip penetration in the free and in-cylinder spray under various ambient pressure. In order to observe the spray characteristics as a function of injection timing, the piston head shape of re-entrant type was created and the fuel injected into the chamber according to various distance between nozzle tip and piston wall in consideration of injection timing. Also, the spray and evaporation characteristics in the cylinder was calculated by using KlVA-3V code for simulating spray development process and spray tip penetration under real engine conditions. It was revealed that the high ambient pressure of 3 MPa was led to delay the spray development and evaporation of DME spray. In addition, injected sprays after BTDC 20 degrees entered the bowl region and the spray at the BTDC 30 degrees was divided into two regions. In the calculated results, the liquefied spray tip penetration and fuel evaporation were shorter and more increased as the injection timing was retarded, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.46-54
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• 2005

Film cooling characteristics has been examined numerically for the height variation of a stepped slot exit. In this study, the upstream wall height of the stepped slot exit varies from -2d (d = slot width) to 3d, blowing ratio ranges from 0.5 to 3, and injection angles are $15^{\circ},\;30^{\circ},\;and\;45^{\circ}$. The results showed that film cooling performance was mainly subjected to the magnitude of recirculation region near the downstream-side slot exit as well as the magnitude and the distribution region of turbulent kinetic energy due to the local velocity and momentum differences between the coolant and the main flow near the slot exit. The up-1d type slot at higher blowing ratios over 2 and the flat type slot at lower blowing ratios below 1 have the best film cooling performances, in case of the injection angles of $30^{\circ},\;and\;45^{\circ}$, respectively. Compared with the other injection angles, in case of the injection angles of $15^{\circ}$, the best film cooling performances was shown in even a higher upstream wall (up-3d) at higher blowing ratio like 3 by the gradual reduction of the coolant velocity which minimizes the local velocity differences between the coolant and the main flow near the slot exit.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.10
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• pp.1285-1293
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• 2000

In port fuel injection system of SI engines, injected fuel is impinged onto the surface of intake valves and port-wall, and then formed the wall flow under the cold start operation. Wall flows entrained into the cylinder result in the unsteady and nonuniform mixture formation. Therefore, the spray impingement to the wall is considered as having negative influences such as lowering combustion efficiency and causing unburned hydrocarbon emissions. This study investigates the spray characteristics of the wall impinging air-assist spray in suction air flow. A PDPA was used to analyze the flow characteristics under the different conditions such as impingement angle and supplied air. Experimental data concerning the impinging sprays has been obtained in the vicinity of the wall. Measured droplets divided into the pre-impinging droplets which denote as the positive normal velocities and post-impinging droplets that describe as the negative normal velocities for the suction flow. Their velocities, size distributions and SMD are comparatively analyzed before and after the impingement.

• Journal of the Korean GEO-environmental Society
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• v.6 no.4
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• pp.65-71
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• 2005

Recently, difficulties in soft ground improvement that caused by effectiveness of the ground improvement, the durability and environmentally friendliness of the injection material come to the fore. This paper studies the field applicability of the SCM in reinforcement and seepage cutoff of the back of an existing continuous wall. SCM uses double rod which imposes heavy pressure($10-100kgf/cm^2$) to disturbed, cut, discharge, and mix the ground. It is observed that a bulb is formed by using cement paste and environmentally friendly injection materials with minimal alkali leaching. Unconfined compression test and fish poison tests are performed. Test results indicate that the method results in higher durability, less leaching through use of the environmentally friendly injection material, and faster mobilization of the strength. In addition, field tests confirm the formation of the bulb and the seepage cutoff wall.

• Journal of ILASS-Korea
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• v.10 no.1
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• pp.17-23
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• 2005

Even though a relatively complete knowledge base has been established for diesel sprays, much of the knowledge cannot be directly translated to correlate the characteristics of gasoline spray. The macroscopic characteristics of gasoline impingement spray was investigated with photographic and image processing technique by Particle Motion Analysis System. The injector with single hole nozzle diameter of 0.28 mm was used in this experiment and the injection duration was selected as 10 msec. The injection pressure with 0.3, 0.35, and 0.4 MPa, impingement distance or 70, 100 and 130m, impingement angle or 0.15, 30 and $45^{\circ}$ were employed for the variables to affect the spray characteristics of impinging spray. It is clear that there is the analogy on the spray tip penetration between the gasoline impinging jet and diesel free jet. The spray tip penetration of impinging gasoline spray is proportional to the quarter power of the time after start of injection. The maximum height of impinging gasoline spray is also proportional to the quarter power of the time regardless of impingement distance, impingement angle and injection pressure. In addition, the effect of impingement angle on the spray tip penetration is significant according to the time after start of injection, even though there is minor effect in the initial stage of time after start of injection. Moreover, there is no remarkable effect of injection pressure on the spray tip Penetration under the experimental condition used in this study.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.119-122
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• 2002

In general, Liquid Injection Thrust Vector Control(LITVC) is accomplished by injecting a liquid into the supersonic exhaust flow through holes in the wall of the propulsion nozzle. This injection flow field is highly complicated and detailed flow physics associated with the secondary flow injection should be known far the practical design and use of the LITVC system. The present study aims at understanding the LTTVC flow field and obtaining fundamental design parameters for LITVC. The experimentations were performed in a supersonic blow-down wind tunnel. Compressed, dry air was used for both the main exhaust and injection flows but the pressures of these two flows were controlled independently. The location of the injection holes was changed and the pressures of the two streams were also changed between 2.0 and 15.0 bar. The effectiveness of LITVC was discussed in details using the results of the pressure measurements and flow visualizations

• Korean Journal of Veterinary Research
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• v.31 no.4
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• pp.519-522
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• 1991

Pain reflex and anesthetic state in swine with xylazine epidural anesthesia were observed. In xylazine epidural anesthesia, dosages of 0.50mg/kg BW for analgesia of perineal region and 0.7550mg/kg for analgesia of low abdominal wall were required. Regional anesthesia was induced 5~20 min after epidural injection of xylazine and recovered 90~120 min after administration. The results indicated that xylazine as an epidural local anesthetic was useful in swine.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.287-290
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• 2001

최근 정보통신 산업의 급속한 발전으로 이동 통신용 단말기 및 반도체 칩 케리어 등의 플라스틱 부품의 초소형 경량화 요구가 증대되고 있다. 미세 사출성형용(micro injection molding) 박판의 사출을 위한 미세사출 성형 고분자 재료는 매우 우수한 용융 유동 특성을 가져야 하고, 반도체나 소형 엔지니어링 부품으로 사용하려면 높은 인장강도, 충격강도 및 치수안정성을 가져야 한다. (중략)

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.593-600
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• 2012

Thixomolding of Mg-alloy is a semi-solid injection molding process utilizing thixotropic phenomenon. Using this process, higher strength, thinner wall section and tighter tolerance without porosity are obtained. It has been applied for production of near-net-shape magnesium component. To design optimal thixomolding process of Mg-alloy part, molding conditions such as slurry temperature, mold temperature and injection time should be determined properly. Selection of these parameters has been dependent upon engineers' experience and intuitiveness. In this paper, to improve mechanical properties of the thixomolded product, optimal selection of process variables such as injection velocity, barrel temperature and die temperature in the process has been studied through microstructural analysis and Taguchi method. Performance of the process is verified through experiments.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.2
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• pp.17-25
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• 2001

In this paper, a theoretical study has been made to reduce the residual stress and birefringence in the injection-molded parts. An optimization program has been used to minimize the residual stresses and birefringence calculated from a simulation program. The thermally induced stress has been calculated using a linear viscoelasticity model. The flow stress and birefringence has been calculated using the Leonov's viscoelasticity model. This has been applied to the injection molding of a circular disc and a plate. the optimization has been done either by changing process variables while maintaining the mold temperature constant or by varying the mold-wall temperature with time. This study shows the significant reduction in residual stress and birefringence is possible through the optimization of processing conditions.