• 한국정밀공학회지
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• 제17권5호
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• pp.100-107
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• 2000

The hydraulic couplings have been widely used in industries, automobile, and power-station drives including ships. A mathematical analysis by which the design and application of hydraulic couplings are made is used in conventional design formulae and general roto-dynamic theories. The fluid flow of hydraulic couplings can be considered to have two component, one circumferentially about the coupling axis, and the other passing fluid from the pump to the turbine in the plane of the coupling axis. Tests have been carried out on the full-scale production coupling. The performance test consists of taking measurement of torque of the fluid coupling for three different amount of working fluid inside with various loads to the output shaft. The purpose of this research is to construct the experimental test equipments and to establish a series of performance test for the domestically developed hydraulic couplings, and to obtain experimental results which can be used to improve the performance of the hydraulic coupling and to solve the practical problems confronted in operation.

• 산업기술연구
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• 제25권A호
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• pp.3-14
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• 2005

In order to accurately analyze the detailed hydraulic characteristics of the curved channel in the downstream of dam with the hydraulic structures such as bridge piers, RMA2 model which is one of two-dimensional models is applied to ChunCheon dam downstream curved channel. A series of hydraulic model tests are carried out for comparison studies. HEC-RAS model is also applied to the same site. There are no errors when velocities and water levels resulted from HEC-RAS model RMA2 model are compared with those of hydraulic model test on the straight channel. But, it is found that results of RMA2 model have a better agreement with those of hydraulic model test than those of HEC-RAS model on the curved channel with bridge piers. Additionally, RMA2 model can be predicted the eddy phenomena around bridge piers of the curved channel.

• Tribology and Lubricants
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• 제30권5호
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• pp.271-277
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• 2014

Hydraulic reciprocating seals have been widely used to prevent fluid leakage and to provide lubricant film on counter surface in various hydraulic system. The degradation of the seal may cause the catastrophic failure of the hydraulic system. To assess the durability of the seals and the compatibility with counter surface, accelerated life testing (ALT) has been typically employed from industry. However, ALT often takes up to a few months to cause a failure of the seals, and therefore, there is a need to develop more efficient ALT methods. In this work, the degradation characteristics of polyurethane (PU) seals from field test are investigated and they are compared to those from the component and bench tests, with an aim to contribute to the development of ALT method. From the comparison of the cross-sectional profiles of the sealing surface of the PU specimens before and after the tests, both wear and compression set are found to be responsible for degradation of the PU seals. It is also shown that the major wear mechanisms of the PU seals from the field is abrasive wear and formation of pits. The component and bench tests performed in this work are shown to reproduce such wear mechanisms, and therefore, those test methods can be used as an ALT method for PU seals. In particular, the bench test proposed in this work may be effectively utilized to assess the durability and the compatibility of the seals with the counter surface. The results of this work are expected to aid in the design of ALT for PU seal.

• 지질공학
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• 제5권2호
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• pp.129-138
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• 1995

주입률의 병화가 안산암의 수압파쇄특성에 미치는 영향을 검토하기 위하여 세 단계의 주입률 조건하에서 파쇄실험을 수행하였다. 40kN의 수직하중 하에서 주입률을 각각 1ml/min, 2ml/min 및 3ml/min로 제어하였을때, 주입률의 변화에 관계없이 파쇄압은 163kg/$cm^2$ 내외로 일정한 값을 나타내었다. 화강암에서는 수압파쇄특성에 미치는 온도변화의 영향을 파악하기 위하여 다섯 단계의 온도 조건 하에서 파쇄실험을 수행하였다. 40kN의 수직하중 하에서 1.7ml/min의 주입률로 파쇄시켰을 때 파쇄압은 상온에서는 평균 168kg/$cm^2$를 보였으나 온도가 상승할수록 감소하여 20$0^{\circ}C$에서는 평균 124kg/$cm^2$를 나타내어 약 25%정도 감소하는 경향을 보였다. 주입률을 일정하게 제어할 경우 균열의 초기 생성압은 온도변화에 상관없이 파쇄압과 잘 일치하였으며 이러한 사실은 균열음 측정결과로도 확인할 수 있었다.

• 농업과학연구
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• 제43권3호
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• pp.450-458
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• 2016

High performance small and mid-sized tractors are required for dryland and orchard operations. A power transmission system is the most important issue for the design of high performance tractors. Many operations, such as loading and lifting, use hydraulic power. In the present study, a hydraulic power transmission system for the 3-point hitch of a 50 kW narrow tractor was developed and its performance was evaluated. First, major components were designed based on target design parameters. Target operations were spraying, weeding, and transportation. Main design parameters were determined through mathematical calculation and computer simulation. The capacity of the hydraulic cylinder was calculated taking the lifting force required for the weight of the implements into consideration. Then, a prototype was fabricated. Major components were the lifting valve, hydraulic cylinder, and 3-point hitch. Finally, performance was evaluated through laboratory tests. Tests were conducted using load weights, lift arm sensor, and lift arm height from the ground. Test results showed that the lifting force was in the range of 23.5 - 29.4 kN. This force was greater than lifting forces of competing foreign tractors by 3.9 - 4.9 kN. These results satisfied the design target value of 20.6 kN, determined by survey of advanced foreign products. The prototype will be commercialized after revision based on various field tests. Improvement of reliability should be also achieved.

• 한국해안해양공학회지
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• 제15권4호
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• pp.249-258
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• 2003

본 연구에서는 사석, cube및 tetrapod를 대상으로 불규칙파를 적용하여 경사식방파제의 피복재 안정성에 대한 2차원 실험을 수행하였다. 파복재 중량산정식으로는 Hudson식과 van der Meer식을 대상으로 하였으며, Hudson식은 규칙파, van der Meer식은 불규칙파를 적용한 실험으로부터 얻어진 식이다. 본 연구의 목적은 실험결과를 이용하여 Hudson식과 van der Meer식을 비교 검토하는 것이다

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(1)
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• pp.377-382
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• 1995

An evaluation method of spacer grid thermal mixing performance in rod bundles is suggested based on hydraulic tests in a single phase flow. Heat transfer correlation was derived by the analogy between momentum and heat transfer. Three of major factors, such as blockage ratio of spacer grid, convective flow swirling, and turbulent intensity, were found to be significantly influential to the spacer grid thermal mixing performance. Local heat transfer near spacer grid was predicted for the hydraulic test of 6 ${\times}$ 6 rod bundles with neighboring different spacer grids.

• International Journal of Precision Engineering and Manufacturing
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• 제5권1호
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• pp.55-59
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• 2004

This study developed a fully automated test system for pressure vessels, containing such as oxygen, nitrogen, which is widely used in many industries. The pressure vessel test has three major parts including weight measurement test, water-hydraulic test and leakage test followed by cleaning and drying. The control system for these tests consists of three parts: a PLC, a monitoring system and a database management system. The PLC oversees overall control of test machines, while the monitoring system measures and displays weight, pressure, flow etc. for every situations, and the database management system stores test data. These three modules are designed to communicate with one another at 1 Hz frequency alerting problematic situations to the operator. The system has gone through actual field tests for verification of performances.

• 한국농공학회지
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• 제45권3호
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• pp.65-72
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• 2003

The objective of this study is to evaluate the stability of the design criteria recommended by Betram and Terzaghi as compared with the experimental result. A series of NEF tests was conducted to determine the loss of volume in base soils. The three kinds of base soils classified as CL, SC and SM are used for the NEF tests with various hydraulic pressures and filters following upper and lower bond of the criteria. Volume loss characteristics of the base soils was examined closely by the results of the test successfully. Firstly, it was found that the loss of base soils was mostly eroded at the first stage of seepage. Secondly, the amount of loss volume was ranked CL > SM > SC in order of their amounts for upper criteria, and SM > CL > SC orderly for lower criteria. Thirdly, the volume loss of all soils was increased with increasing the hydraulic pressures. And lastly, the needs of the new design criteria was proved for the control of seepage and piping.

• 상하수도학회지
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• 제25권4호
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• pp.497-502
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• 2011

In order to examine the effects of combination of plug flow reactors in series on hydraulic characteristics, comparative tracer tests were conducted for the cases of the existing clear well and clear wells combined in series. From the results of tests, $T_{10}$/T within existing clear well was 0.62~0.68 depending on inlet flowrate, and that in the case of combination in series was 0.69~0.78. While it would be minor improvement in contact efficiency, it would be appropriate to combine two clearwell with pipe in series for expansion.