• Tribology and Lubricants
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• 제20권4호
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• pp.204-208
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• 2004

This paper presents the oil leakage characteristics of the valve stem system in gasoline engines. For the oil leakage investigation, four study models have been prepared as functions of used poppet valve and used valve stem seal, used poppet valve and unused valve stem seal, unused poppet valve and used valve stem seal, and unused poppet valve and unused valve stem seal. With four models, the experimental study on the oil leakage has been investigated for the oil temperature, intake pressure, and camshaft speed. The experimental results show that the sealing performance of the valve stem seal plays an important role on the leakage of the valve stem system. And the appropriate replacement of a stem seal with used poppet valve shows good sealing performance in oil leakage in compared with a new valve system.

• Journal of Advanced Marine Engineering and Technology
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• 제32권4호
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• pp.557-562
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• 2008

In this paper, experiments have been performed for the investigation of tribological characteristics of automobile gear oil with the addition of ZDDP and DEP by using the FALEX WEAR TEST MACHINE. The results are as follows. The wear characteristics of gear oil was improved by adding compound additives. The extreme pressure of gear oil increases and then decreases with the applied load. The maximum extreme pressure of gear oil with compound additive is bigger then that of pure gear oil. The friction coefficient of pure gear oil monotonically increases with the temperature, but that of gear oil mixed with the additives decreases at the high temperature.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1006-1011
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• 2004

Recently, technical trend in machine tools is focused on enhancing of speed, accuracy and reliability. Such high speed usually results in thermal displacement and structural deformation. To minimize such thermal effect, most precision machine tools adopt high precision cooling system. This study proposes a temperature control for an oil cooler system using PI control with fuzzy logic. In a cooler system, the refrigerant flow rate is controlled by rotational speed of the compressor, where the outlet oil temperature is selected as the control variable. The fuzzy control rules iteratively correct PID parameters to minimize the error, difference between the outlet temperature and the reference one. Here, the ambient temperature is used as the reference one. To show the effectiveness of the proposed method, a series of experiments are conducted for an oil cooler system of machine tools, and the results are compared with the ones of a conventional PID control. The experimental results show that the proposed method has advantages of smaller overshoot and smaller steady state error.

• 한국의류학회지
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• 제18권5호
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• pp.661-673
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• 1994

We have gathered a fatty acid to recycle the waste oil of food manufacturing process, and then made a soap from the waste oil by alkali saponification. Effects of the washing elements such as the concentration of the soap, temperature and time were evaluated to find out the optimum washing conditions, and results are as follows. 1. We could find soaps made from the soybean oil (A), corn oil (B), rape seed salad oil (C), cotton seed oil (D) and a soap consisting of the each oil 25% respectively (I) had the lowest surface tension at the concentration of 0.225% -0.25%. Compared with the single fatty-acid soap, the multi-component soap I showed the lower surface tension at the cmc. 2. All the samples of A-I showed the lowest contact angle for the solid material at the concentration of 0.25%. The multi-component soap of I showed higher contact angle than the single.component soaps of A, B, C and D. 3. The soap G, made from the waste oil, show lower surface tension than 5, made from the complex raw fats of the eatable fatty oil acid and H, commercial soap. 4. The washing efficiency depends on the washing time. Especially the 25-minute was found to be the optimum washing time. 5. The highest washing efficiency was found at the 0.25% cont. reagardless of the washing temperature. At 0.15% concentration level the washing efficiency reduces as washing tem- perature increases. At 0.3% concentration level the highest washing efficiency was found between $50^{\circ}$-$60^{\circ}$. 6. The soap made from the waste oil showed the highest washing efficiency in terms of concentration, temperature, and time. 7. The soap made from the waste oil showed the similiar concentration of hydrogen ion to the synthetic detergent. 8. The hand value of the fabric washed by the soap made from the waste oil was a little lower value than those washed by the synthetic detergent.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2609-2614
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• 2007

Shell & Tube type Oil Cooler is widely used for hydraulic presses, die casting machines, generation equipments, machine tools and construction heavy machinery. Temperature of oil in the hydraulic system changes viscosity and thickness of oil film. They have a bad effect to performance and lubrication of hydraulic machinery, so it is important to know exactly the heat exchanging efficiency of oil cooler for controlling oil temperature. But most Korean manufacturers do not have test equipment for oil cooler, so they cannot carry out the efficiency test of oil cooler and it is impossible to verify its performance. This paper includes information of construction of necessary utilities for oil cooler test and design and manufacture of test equipment. One can select the optimum product by obtaining performance data through tests of various kinds of oil coolers. And also the paper developed a program which can be easily used for design of 2D and 3D drawings of oil cooler.

• 융합신호처리학회논문지
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• 제14권3호
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• pp.205-211
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• 2013

최근 공작기계 분야에서 가공속도와 가공정밀도 같은 시스템 성능이 한층 요구되고 있다. 특히 가공속도가 증가함에 따라 공작기계와 수가공 분야의 공작물 가공 부위에 유해한 열 발생을 초래하게 된다. 이 열은 가공 정밀도를 저하시키는 주된 원인으로 작용한다. 따라서 온도를 제어하는 오일쿨러는 공작기계에서 필수적이다. 일반적으로 두 가지 대표적인 제어기법인 핫가스 바이패스방식과 압축기 가변속 제어 방식이 오일쿨러에 채택 되었다. 본 논문에서는 공작기계에 사용하는 핫가스 바이패스 오일쿨러의 정밀한 온도특성을 얻기 위한 퍼지 제어기의 설계와 구현 방법을 다룬다. 출구 오일온도를 설정값과 실내온도로 잘 유지하도록 전자팽창밸브의 개도 각도를 제어하였다. 특히, 퍼지 제어기는 갑작스러운 외란에 의한 온도변화를 억제하는 기능을 포함하고 있다. 몇 가지 실험을 통하여 제안한 방법으로 목표 온도를 ${\pm}0.22^{\circ}C$정상상태 오차 이내로 제어할 수 있었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.95-96
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• 2002

The operation of proceeding bearing in the conditions of misaligned axis of proceeding and bush leads to the load concentration on the bearing edges causing further mixed lubrication conditions, unstable operation and intensive wear of mating parts. For the design process of proceeding bearing the knowledge of static characteristics determined from the oil film pressure and temperature distribution is very important. For the 3-lobe proceeding bearing, the pressure, temperature and viscosity fields, load capacity, minimum oil film thickness, power loss, oil flow and maximum oil film temperature have been determined by iterative solution of the Reynolds', energy and viscosity equations. The paper introduces the results of theoretical investigations of static characteristics of 3-lobe proceeding bearing operating at misaligned axis of proceeding and bush. An effect of misalignment ratio, length to diameter ratio of the proceeding bearing, the lobe clearance ratio on the static characteristics was investigated. Laminar, adiabatic model of oil film for the solution of Reynolds, energy and viscosity equations was applied.

• 한국분무공학회지
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• 제14권3호
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• pp.122-130
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• 2009

Vegetable oil and its derivatives as an alternative diesel fuel have become more attractive recently because of its environmental benefits and the fact that they are made from renewable resources. Viscosity is the most significant property to affect the utilization of vegetable oil and its derivatives in the compression ignition engines. This paper presents the existing correlations for predicting the viscosity of vegetable oil and its derivatives for compression ignition engines. According to the parameter considered in the correlations, the empirical correlations can be divided into six groups: correlations as a function of temperature, of proportion, of composition, of temperature and composition, of temperature and proportion, and of fuel properties. Out of physical properties of fuel, there exist in the literature several parameters for giving the influence on kinematic viscosity such as density, specific gravity, the ratio of iodine value over the saponification value, higher heating value, flash point and pressure. The study for the verification of applicability of existing correlations to non-edible vegetable oil and its derivatives is required.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.147-151
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• 1994

In order to investigate the dielectric characteristic insulating oil is chosen insulating oil for electric cable, and experiment is performed in the temperature range of 30∼120[$^{\circ}C$] and frequency range of 30∼1${\times}$10$\^$6/[㎐]. As a result, the observed linear decrease in tan $\delta$ value at the low frequency range is due to the influence of frequency, whereas the increase in tan $\delta$ value at high frequency range is contributed by the electrode's resistance and dielectric loss. The dipole moment and activation energy of specimen are obtained 1.22(debye) and 12.75∼18.66[㎉/㏖e] of high temperature region, 15.68 ∼ 20.6[㎉/㏖e] of low temperature region respectively.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.343-346
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• 2008

To improve the reliability and extend the life for a wind-turbine gearbox, the gearbox needs to be monitored and analysed exactly. This study was conducted to analyze and detect the gearbox conditions when lubricating oil contaminated by wear particles was used. Characteristics of the gearbox failure by wear particles were monitored simultaneously by the on-line measurement sensor of vibration, oil condition and temperature. For the detail vibration analyses, frequency analysis(FFT) was performed. The results of the study were summarized as follows: Vibrational signal was found sensitive to abnormal changes of the gearbox conditions when lubricant was contaminated by wear particles. Also, using frequency analysis for the harmonics of gear mesh frequency(GMF), it is found that the failure of gearbox was caused by the damages of meshing gears. However, temperature and oil condition measuring signals were found not so effective to detect any gearbox failure by oil contamination.