• Journal of Biosystems Engineering
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• 제20권3호
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• pp.205-216
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• 1995

A fast and inexpensive approximate analysis method to predict power output characteristics of the Stilting engines in a preliminary design stage was investigated. In basic equations proposed by Walker, typical temperatures of working fluids in expansion and compression spaces were treated as those of working fluids in heater and cooler respectively. While the temperature of working fluid in the expansion space was actually lower than that of working fluid in the heater, the temperature of working fluid in the compression space was higher than that of working fluids in the cooler. In this paper, the working fluid temperature of expansion space was treated as lower than the heater temperature and that of compression space was treated as higher than the cooler temperature. Also, according to them, the power output characteristics of the Stirling engine were evaluated with respect to the GPU-3 and 4-215 Stilting engines. The following conclusions were drawn from the analysis. 1. Using the available experimental data from the GPU-3 Stirling engine, it was shown that the approximate analysis predicts the brake power with a maximum error of 19 percent at 1, 000rpm and with a minimum error of 3 percent at 2, 000rpm. 2. The approximate analysis data which for the GPU-3 Stirling engine were much closer to the experimental data than those of adiabatic 2nd order and 3rd order analysis within 1, 500rpm to 2, 500rpm. 3. The approximate analysis data which for the GPU-3 and 4-215 Stilting engines were much closer to the experimental data than those of the Beal number analysis.

• 동력기계공학회지
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• 제13권5호
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• pp.59-66
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• 2009

High temperature and pressure valves in power plant have been used for fluid flowing and leakage occurred owing to valve internal damage such as disc wear, crack and inserting of foreign objects etc. in these valves. Recently, multi-measuring technique applied both ultrasonic and acoustic method have been used for evaluation of valve internal leakage in order to raise measurement reliability. Therefore, we have performed various leakage tests using ultrasonic and acoustic measuring system and acquired leakage data for the various leakage conditions. In this study, we developed the estimation method of regression model through leakage data, and expectation method for valve opening ratio, which is directly proportion to leakage rate, using the established estimation model from the measured data, valve size and fluid pressure so as to enhance data reliability. As a result of this study, it was founded that expectation method of leakage rate by statistical analysis method is appropriate to valve leakage evaluation.

• 한국산학기술학회논문지
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• 제12권9호
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• pp.3808-3814
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• 2011

본 연구는 열교환기의 효율적인 설계를 위하여 열교환기 내의 삼각형 단면 덕트의 비뉴톤 유체의 압력강하 및 대류 열전달률 수치해석적으로 수행하였다. 비뉴톤 유체의 구성방정식은 기존의 비뉴톤 유체 멱법칙을 보완한 수정 멱법칙 모델을 채택하였다. 덕트 내의 압력강하를 의미하는 마찰계수와 수정 레이놀즈 수의 곱은 기존 연구의 문헌치와 비교할 때 뉴톤 유체 영역과 비뉴톤 멱법칙 영역에서 각각 0.13% 및 2.85% 내에서 일치함을 보였고 비뉴톤 수정멱법칙 유체 모델의 형태를 띠는 Shear-Thinning 유체를 열교환기 내의 삼각형 단면 덕트 내에서 사용하면 뉴톤 유체보다 62%의 압력강하를 감소시켰고 12%의 대류 열전달 향상을 발생시킬 수 있었다.

• 대한기계학회논문집B
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• 제26권6호
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• pp.868-874
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• 2002

A high-impulse, low-power, digital microthruster has been developed using low-boiling-temperature liquid propellant with high-viscosity fluid plug. The viscous fiction force of the fluid plug increases the blast pressure and the low-boiling-temperature liquid propellant is intended to reduce input power consumption. The three-layer microthruster has been fabricated by surface micromachining as well as bulk micromachining in the size of 7$\times$13$\times$1.5㎣. A digital output impulse bit of 6.4$\times$10$^{-8}$ Nsec has been obtained from the fabricated microthruster using perfluoro normal hexane (FC72) propellant and oil plug, resulting in about ten times increase of the impulse bit using one hundredth electrical input energy compared to the conventional multiple-shot microthruster.

• 동력기계공학회지
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• 제5권4호
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• pp.38-43
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• 2001

This paper describes the effect of dynamic characteristics in tube line by external vibration conveying fluid with the power steering system. By the experimental analysis we found out that the factor of system vibration is the fluid-structure interaction of tube line. In fluid-filled tube system we study on the influence that the natural frequency of system and the frequency of wave motion produce upon through experiment. Experiments are modal test, frequency response function in continuous system, and vibrating tests when the system is driving with bolted clamping joint condition. From the results of the experimental studies, we obtained that the natural frequencies of system are very important than the wave induced vibrations. And we found that the tendency of system vibration level was decreased by bolting force, bolting condition and clamping distance.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.665-672
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• 2004

Chemical cleaning of boiler pipelines is necessary before the commissioning of thermal power plant after many years of construction. Fluid-Dynamic study for the chemical cleaning of boiler piplelines in Young-Heung thermal power plant is carried out. First, flow velocity necessary to sustain and exhaust solid particles in the vertical pipelines is calculated. Second, the flowrate necessary to make the calculated velocities in each vertical pipelines is calculated. Third, all the pipelines are analyzed with the Piping Systems Fluid Flow software to calculated the pressure loss in the pipelines. Finally, the operating point of the applied pump is calculated with the help of the same software.

• 드라이브 ㆍ 컨트롤
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• 제2권1호
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• pp.32-35
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• 2005

• 동력기계공학회지
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• 제14권6호
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• pp.67-74
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• 2010

Many tanks are installed in ship and marine structures. They are often in contact with inner or outer fluid, like ballast, fuel and cargo tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks in contact with fluid near engine and propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tanks. Many authors have studied vibration of cylindrical and rectangular tanks containing fluid. Few research on dynamic interaction among tank walls through fluid are reported in the vibration of rectangular tanks recently. In case of rectangular tanks, structural coupling between adjacent panels and effect of vibration modes of multiple panels on added mass have to be considered. In the previous report, A numerical tool of vibration analysis of a 3-dimensional tank is developed by using finite element method for plates and boundary element method for fluid region. In this paper, the coupling effect between panels of a tank on added mass of containing fluid, the effect of structural constraint between panels on each vibration mode for fluid region and mode characteristics in accordance with changing breadth of the plates are investigated numerically and discussed.

• 유공압시스템학회논문집
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• 제1권2호
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• pp.8-14
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• 2004

Abstract: In the oil hydraulic piston pumps the clearance between the valve plate and cylinder block plays an important role for volumetric and overall efficiency. Thus, adequate lubricational fluid film is needed for the interface. In this study, fluid film thickness is measured by a gap sensor and a slip ring under operational conditions to observe the behavior of the lubrication mechanism in detail. To investigate the effect according to the valve plate types in view of the fluid film, three different types were designed. Leakage flow rate and shaft torque were also measured to clarify the effect according to the valve plate types. A broad range of experiments were conducted to provide reasonable data on the effect of fluid film. In this experiments two main parameters were found, of which the one is the discharge pressure and the other is valve plate geometry. As a result, we found that the spherical valve plate could get more stable fluid film thickness, maintain good efficiency for high pressure range than the other types.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.589-594
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• 1998

Heat and fluid flow in the motor block room of a motorized car is numerically simulated. The motorized car, composed of a motor block room and a passenger room, supplies additional Power to achieve the design speed. A motor block, a transformer, and a fan are equipped in the motor block room. Flow phenomena in the ducts on the motor block and power transformer are investigated. Also, the three dimensional heat and fluid flow in the motor block room is simulated to give a qualitative information of the flow characteristics.