• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.33-34
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• 2012

• 한국산학기술학회논문지
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• 제15권6호
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• pp.3950-3960
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• 2014

본 연구에서는 수치모의를 통해서 월류 흐름이 존재하는 수몰 사각 실린더의 항력 특성에 대하여 분석하였다. 모의의 신뢰성을 검토하기 위하여 실험자료와 비교하였으며 실험에서 측정하기 어려운 실린더 접촉면의 압력에 대한 분석을 통해서 상대 수심에 따른 항력의 특성을 분석하였다. 3차원 동수역학 모형을 이용한 수몰 사각 실린더의 항력 계산 결과는 실험자료의 상대 수심의 변화에 따른 항력계수의 변화를 유사하게 모의하고 있음을 확인할 수 있었다. 수치모의 결과 분석에 의하면 수몰 사각 실린더에 작용하는 항력은 대부분 압력이며 상대 수심이 증가함에 따라 전단력의 비중은 감소하였다. 실린더 접촉면의 압력계수 분석 결과에 의하면 상대 수심이 낮은 경우에는 전면부에 높은 압력계수가 형성되고 후면부에 낮은 압력계수가 형성되어 결과적으로 높은 항력계수가 나타남을 확인하였다. 상대수심이 증가하면 전면부의 압력계수는 감소하고 후면부의 압력계수는 증가하여 2차원 흐름 내의 사각 실린더와 유사한 양상을 나타낸다. 정수압 영향 분석에 의하면 전면부와 후면부의 수위 차에 의한 정수압은 항력에 미치는 영향이 제한적이며 사각 실린더에 의해 형성되는 국부적인 수위와 함께 3차원적인 흐름에 의해 형성되는 동수압의 영향이 크다는 것을 확인하였다.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.118-125
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• 2009

Calculation of indicated mean effective pressure(IMEP) requires high cylinder pressure sampling rate and heavy computational load. Because of that, it is difficult to implement in a conventional electronic control unit. In this paper, a cylinder pressure based real-time IMEP estimation method is proposed for controller implementation. Crank angle at 10-bar difference pressure($CA_{DP10}$) and cylinder pressure difference between $60^{\circ}$ ATDC and $60^{\circ}$ BTDC($DP_{deg}$) are used for IMEP estimation. These pressure variables can represent effectively start of combustion(SOC) and fuel injection quantity respectively. The proposed IMEP estimation method is validated by transient engine operation using a common-rail direct injection diesel engine.

• 유공압시스템학회논문집
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• 제5권2호
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• pp.14-19
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• 2008

Hydraulic excavator consists of booms, arms, bucket, and cylinder. The cylinder make these structures moved and the cushion parts of cylinder in operation absorb the great impact which is stemmed from high velocity and pressure at cushion parts of cylinders. The cushion technology of cylinders has a great effect on the operator's comfortable as well as protecting equipment from damage by suppressing the inertia of the hydraulic excavator. In this study, three hydraulic cylinders have different shapes of a cushion ring, respectively. we studied optimal cushion pattern by analyzing the change of cushion pressure and time, according to supply pressure and velocity variations.

• 오토저널
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• 제11권2호
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• pp.41-54
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• 1989

In this study, steady state heat conduction problems of the cylinder block of turbocharged gasoline engine were solved by the boundary element method. Surface of the cylinder block was divided by the triangular cells with constant potential. Temperature distribution, effective heat transfer coefficient of the cylinder block were investigated with variation of equivalence ratio, engine speed and boost pressure. The results show that maximum temperature of cylinder block increase rapidly with increasing engine speed and boost pressure. The monolithic structure of cylinder block results in sever inhomogeneity of inner wall temperature at the high engine speed and boost pressure.

• Wind and Structures
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• 제17권5호
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• pp.465-477
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• 2013

In this paper, the effects of parapets on the mean and fluctuating wind pressures which are acting on a flat top of a finite cylinder vertically placed on a flat plate have experimentally been investigated. The aspect ratio (AR) of cylinder is 1 and the Reynolds number (Re) based on cylinder diameter and free stream velocity is 150000. The pressure distributions on the flat top and the side wall of the finite cylinder immersed in a simulated atmospheric boundary layer have been obtained for different parapet heights. The large magnitudes of mean and minimum suction pressures occurring near the leading edge were measured for the cases with and without parapet. They shift to the further downstream on the circular top with increasing parapet height. It is seen that the parapets reduce the local high suction on the top up to 24%.

• 연구논문집
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• 통권28호
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• pp.73-87
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• 1998

A pneumatic control system of compressed air as a working fluid has a variety of advantages such as low price, high respondence, non-explosion and good control performance and thus has many applications in the field of automobile, electronic and semiconductor industry. However, it has a difficulty in contolling a precise position due to quick response of system and compressibility of working fluid and. in particular, shock stress may occur due to an external load, resulting in fracture of a cylinder cap unless cushion device is equipped in the linear actuator. To avoid this, a cushion device should be installed for damping effect of the external load and the supply pressure as well as for decreasing shock stress and vibration caused by high speed rotation. Previous studies include dimensionless analyses and computer simulations of cushion capability and experiments of horizontally-mounted cylinder performances. A new attempt is experimentally made in this study using a vertically-mounted cylinder under an operation condition of 4, 5 and 6 (bar) as supply pressure and 40, 70 and 100 (kgf) as external load. It turns out that the cushion pressure is mainly a function of the external load rather than the supply pressure. The cushion characteristics was also revealed in the meter-in circuit.

• Journal of Advanced Marine Engineering and Technology
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• 제23권1호
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• pp.69-78
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• 1999

In this study a new pattern of pressure control of hydraulic cylinder using high speed On-Off solenoid valve in the electro-hydraulic system has been suggested. The control valve is 3-way high speed On-Off solenoid valve which is operated by PWM(Pulse Width Modulation)control signal. The high speed On-Off solenoid valve has a tendency to induce severe pressure fluctuation in the hydraulic actuator so it has not been used for the purpose of closed loop control with direct pres-sure feedback. In this study closed loop control with direct pressure feedback is enabled by using a digital filter which has linear minimum mean square filter algorithm. Through some experiments it is confirmed that stable pressure control can be realized by the proposed control technique.

• 한국가스학회지
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• 제18권2호
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• pp.16-20
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• 2014

본 논문에서는 현재 캠핑 문화의 확산에 따라 수요가 증가하는 LGP 재충전 용기에 관한 내압성능을 실험적으로 검증하였다. 겨울철에 부탄가스는 높은 비점의 영향으로 기화가 쉽게 일어나지 않는 물적 특성을 지니고 있다. 하지만 프로판의 경우 비점이 낮아 겨울철에도 기화가 쉽게 일어나 연료로써 공급 필요성이 증가되고 있다. 하지만 프로판은 높은 증기압으로 인해 많은 안전상의 문제가 존재하며, 이를 극복하고 연로로써 유통되기 위해서는 안전한 용기의 공급이 우선시 되어야 한다. 국내외적으로 고압용 소형 재충전 용기의 보급을 시도하고 있으나, 프로판의 높은 증기압으로 인한 안전상의 문제로 제재가 되고 있다. 본 논문은 재충전 용기의 내압성능을 검증하기 위해 수압장치를 이용하여 용기의 가압 및 파열 실험을 수행하였다. 또한 고온에서 프로판의 증기압과 용기 파열시 수압과 비교하여 그 특성을 제시하였다. 수압가압 실험 및 파열 실험을 통해 토출 된 본 논문의 결과는 향후 소형 재충전 용기 개발 연구의 기초가 될 것으로 기대하며, 재충전 용기의 보급에 있어 기준 자료로 활용 될 것으로 사료된다.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.28-38
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• 2003

Finite element analysis of cylinder heat/block compound under assembly, thermal and firing condition were performed. FE model including two cylinders with gasket, head bolts, liners and valve seats was used. FE modeling method and boundary conditions were introduced. Stress distribution and deformation of cylinder head and block under each loading condition were presented. Gasket pressure distribution and bore distortion level were predicted. Measured data of bore distortion was compared with the analysis results. The analysis result showed similar trends with the experimental data. High cycle fatigue analysis on the basis of this result has been performed in order to find the critical areas of the engine assembly.