• 한국자동차공학회논문집
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• 제4권1호
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• pp.165-176
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• 1996

The flow field and spray characteristics for loop scavenged type 2stroke engine having pancake shape was numerically computed using KIVA-Ⅱ code. The cylinder has 1intake port, 2side intake ports and 1exhaust port with induced flow angle 25 deg. In engine calculation, the chop techniques is used to strip or add planes of cells across the mesh adjacent to the TDC and the BDC(ports parts) for preventing the demand of exceed time during the computation, providing a control on cell height in the squish region. The modified turbulent model including the consideration of the compressibility effect due to the compression and expansion of piston was also used. The case of 25 deg.(injection angle) which is opposite to scavenging flow direction shows better the distribution of droplets and the evaporation rate of droplets compared to other cases(0 deg., - 25 deg.). When injection pressure was increased, the spray tip penetration became longer. When injection pressure was increased, the interaction between the upward gas velocity and spray droplets strongly cause. Thus the breakup of droplets is strongly occurred and the evaporation rate of droplets was found to be better.

• 에너지공학
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• 제11권2호
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• pp.160-165
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• 2002

LPG 연료를 사용하는 대형 단기통엔진은 연소과정과 배기성능을 파악하기 위해서 설계.제작되었다. 실린더헤드와 피스톤 크라운은 LPG 연소를 위해서 변경되었다. 또한 플라이휠은 단기통엔진의 진동을 최소로 하기 위해서 제작되었다. 실험용 단기통엔진의 실린더내경과 행정은 각각 130mm와 140mm이다. 압축비는 피스톤 크라운 형상을 다르게 하여 8에서 9로 변경되었다. 본 연구를 위해서 제작된 단기통엔진은 1,000rpm에서 운전되었다. 본 연구의 주요 결론은 (1)제작된 엔진의 출력은 3가지 다른 압축비별로 당량비 1.0에서 최고를 나타낸다. (2) 압축비 증가에 따라서 출력이 약간 증간한다. (3) 최적 점화시기는 크랭크각으로 2에서 10까지 압축비의 증가와 함께 지각되어진다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권6호
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• pp.981-988
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• 2008

This paper describes a development of automatic measuring device for cylinder liner wear amount. An operator should regularly measure the wear amount of the cylinder liner to prevent the wear amount of the cylinder liner from exceeding the maximum limit specific to the engine type. In previous methods. an operator entered the inside of the cylinder liner on a ladder and measured the amount of wear using a inside micrometer. Such method is unpleasant in severe environments and full of hazards. In addition, in order to enter the cylinder, the piston head had to be detached. requiring much time and money. In order to solve these problems, a new measuring device that consists of two measuring units and a special install jig is developed. The measuring units are installed through the scavenging air port by the install jig and measures the wear amount during 1 revolution of crankshaft. so detaching of the cylinder head and entering inside the cylinder liner are not required.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.472-477
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• 2003

This study was performed to investigate the behavior of vapor phase of fuel mixtures with different piston cavity diameters in a optically accessible engine. The images of vapor phases were measured in the motoring engine using exciplex fluorescence method. The conventional engine was modified as GDI engine with swirl flow. Fuel was injected into atmospheric nitrogen to prevent quenching phenomenon by oxygen. Injection pressure is 5.1MPa. Two dimensional spray fluorescence image of vapor phases was acquired to analyze spray behavior and fuel distribution inside of cylinder. Three injection timings were set at BTDC $180^{\circ}$, $60^{\circ}$and $60^{\circ}$. With a fuel injection timing of BTDC $60^{\circ}$, fuel-rich mixture was concentrated in near the cavity center. With a fuel injection timing of BTDC $60^{\circ}$, fuel-rich mixture level in the center region was highest in the S-type during the late compression stroke. With a fuel injection timing of BTDC $180^{\circ}$, fuel was not affected in a piston cavity and generally distributed as homogeneous mixture.

• 드라이브 ㆍ 컨트롤
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• 제16권3호
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• pp.23-32
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• 2019

This study proposed a fault tolerant control algorithm for electro-hydraulic brake systems where permanent magnet synchronous motor (PMSM) drive is adopted to boost the braking pressure. To cope with motor position sensor faults in the PMSM drive, a braking pressure controller based on an open-loop speed control method for the PMSM was proposed. The magnitude of the current vector was determined from the target braking pressure, and motor rotational speed was derived from the pressure control error to build up the braking pressure. The position offset of the pump piston resulting from a leak in the hydraulic system is also compensated for using the open-loop speed control by moving the piston backward until it is blocked at the end of stroke position. The performance and stability of the proposed controller were experimentally verified. According to the results, the control algorithm can be utilized as an effective means of degraded control for electro-hydraulic brake systems in the case that a motor position sensor fault occurs.

• Structural Engineering and Mechanics
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• 제84권3호
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• pp.337-344
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• 2022

Due to corrosion defects on the surface of the oil pipe, the sealing performance of the annular blowout preventer (BOP) decreases, and the leakage of toxic and harmful gases such as H₂S and SO₂ will threaten the safety of operators on the well. Therefore, this paper establishes the FE model for evaluating the sealing performance of BOP-oil pipe corrosion defects, which is based on the rubber large deformation theory and rubber core sealing mechanism, and designs the experiment of BOP sealing performance to verify the accuracy of the FE model. The sealing performance of BOP sealing oil pipe with corrosion defects is studied. The research results show that the sealing performance of BOP is more sensitive to the axial size of corrosion defects. With the increase of oil pipe outer diameter, the critical size of defects increases continuously. The sensitivity of radial and depth dimensions is low, When for 88.9 mm outer diameter oil pipe, the axial critical size of corrosion defect is 20 mm, the radial critical size is 16 mm and the critical depth is 2 mm. Fit the formula between the outer diameter of oil pipe and the piston increment. According to the formula, the operator can calculate the piston stroke increment required by the BOP to complete the sealing when the oil pipe is corroded.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.89-95
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• 2001

Recently GDI(Gasoline Direct Injection) engine is spotlighted to achieve higher thermal efficiency under partial loads and better performance at full loads. To realize this system, it is essential to make both stratified combustion and homogeneous combustion. When compared to PFI(Port Fuel Injection) engine, GDI engine needs more complicated control and optimal design with injection system. In addition, spray pattern must be optimized according to injection timing because ambient pressure in combustion chamber is also varied. Thus spray structure should be analyzed in details to meet various conditions. In this experimental study, two types of visualization system were developed to simulate compression stroke and intake stroke, respectively. With an increase of the ambient pressure, the penetration length tends to decrease due to rising resistance caused by the drag force of the ambient air. Spray characteristics impinged on the piston has a significant effect on mixture stratification around the spark plug. These results provide the information on macroscopic spray structure and design factors far developing GDI injector.

• 소음진동
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• 제8권2호
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• pp.239-250
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• 1998

Traditionally, intake noise from internal combustion engine has not recevied much attention compared to exhaust noise. But nowadays, intake noise is a major contributing factor to automotive passenger compartment noise levels. The main objective of this paper is to identify the mechanism of generation, propagation and radiation of the intake noise. With a simplest geometric model, one of the main noise sources for the intake stroke is found to be the pressure surge, which is generated after intake valve closing. The pressure surge, which has the nonlinear acoustic behavior, propagates and radiates with relatively large amplitude. In this paper, unsteady compressible Navier-Stokes equations are employed for the intake stroke of axisymmetric model having a single moving cylinder and a single moving intake valve. To simulate the periodic motion of the piston and the valve, unsteady deforming mesh algorithm is employed and Thompson's non-reflecting boundary condition is applied to the radiation field. In order to resolve the small amplitude waves at the radiation field, essentially non-oscillatory(ENO) schemes with an artificial compression method (ACM) are used.

• 한국자동차공학회논문집
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• 제16권6호
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• pp.148-156
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• 2008

This paper is the first of 2 companion papers which investigate in-cylinder swirl generation characteristics according to inlet valve angle. Two DOHC 4 valve engines, one has wide intake valve angle and the other has narrow valve angle, were used to compare the characteristics of swirl motion generation in the cylinder. One intake port was deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake stroke. The results show that the stronger swirl motion is observed in wide valve angle engine at the early intake stage; however, the swirl motion is gradually distorted by the intake flow component passing through valve area near the cylinder wall as the stroke proceeds. The tumble motion also does so in wide angle. On the contrary, the swirl and tumble motions, which are not clear at the initial stage, become better and better arranged as the piston goes down and up again after bottom dead center.

• 수산해양기술연구
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• 제23권2호
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• pp.86-94
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• 1987

열선유속계를 이용하여 디이젤 기관 연소실내의 한점에서 유속을 측정한 결과는 다음과 같은 결론을 얻었다. 1. 연소실내의 유동은 cylinder의 원주방향의 속도 성분이 크며, 유속변화는 밸브 timing과 피스톤 속도등에 밀접한 관계가 있다. 2. 유속은 흡입시부터 증가하여 압축행정중 흡입밸브가 닫히는 60$^{\circ}$ABDC에서 최대치를 갖고 이후 피스톤의 속도가 감소함에 따라 유속도 감소하여 팽창행정중 배기 밸브가 열리는 120$^{\circ}$ATDC에서 다시 증가하였다. 3. 평균유속은 shroud 밸브 사용시가 no shroud 밸브 사용시보다 낮지만 shroud 밸브 사용시 흡입행정에서 난류강도가 가장 크게 나타났다. 4. 90$^{\circ}$shroud 밸브 사용시가 120$^{\circ}$shroud 밸브 사용시보다 난류강도는 더 크고, 90$^{\circ}$shroud의 180$^{\circ}$위치에서 난류강도가 제일 크게 나타났다.(이 논문의 결론부분임)