• Tribology and Lubricants
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• v.39 no.2
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• pp.49-55
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• 2023

Currently, the demand for green technologies toward a sustainable future is rapidly increasing due to growing concern over environmental issues. Methanol is biodegradable and can provide clean combustion to reduce sulfur oxide and nitrogen oxide emissions, and therefore it is a candidate fuel for marine engines. However, the effect of methanol on tribological characteristic degradation should be addressed for methanol-fueled engines. In this study, the methanol addition effects on tribological characteristic degradation is experimentally assessed using a pin-on-disk tribo-tester. Ni-based alloy is used as a target material due to its broad applicability as an engine component material. For a lubricant, engine oil with and without methanol are used. The tests are conducted for up to 10,000 cycles under boundary lubrication while the change in friction force is monitored. Additionally, the wear rate is determined based on laser scanning confocal microscope data. An additional test in which methanol is added at regular intervals is performed with an aim to directly observe its effect on friction. Overall, the friction coefficient increases slightly with increasing methanol concentration. Furthermore, the wear rate of the pin and disk increase significantly with methanol addition. The results also indicate that the friction increases instantaneously with methanol addition at the contacting interface. These findings may be useful for better understanding the methanol effect on the tribological characteristics of Ni-based alloys for methanol-fueled engines with improved performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.3
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• pp.237-243
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• 2015

In this study, the effects of the mixing ratio of emulsified fuel on the droplet evaporation and spray behavior characteristics were analyzed. A surfactant comprising span 80 and tween 80 mixed at a 9:1 ratio was used for the emulsified fuel. The fuel and surfactant were mixed at a ratio of 3:1 for the emulsified fuel. In addition, considering the mixing ratio of the surfactant, the mixing ratio of $H_2O_2$ in the emulsified fuel was set as EF (emulsified fuel)0, EF2, EF12, EF22, EF32, and EF42. To observe the evaporation characteristics, droplets of the emulsified fuel were dropped on a heating plate and observed using scattered light and a Schlieren system. In addition, to analyze the effect of the $H_2O_2$ mixing ratio, the behavior characteristics of the evaporative free spray were investigated in the mixing ratio range of EF0 to EF22 using a constant volume chamber with heaters. Consequentially, it was found that in the case of EF22, the free spray development of the emulsified fuel was faster than that of EF0 (diesel only) because of the promotion of the evaporation due to the phase change in the peroxide contained in the emulsion fuel.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.4
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• pp.412-418
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• 2020

Generally, the propeller shaft that constitutes the ship shaft system has different patterns of behavior due to the ef ects of engine power, propeller load and eccentric thrust, which increases the risk of bearing failure by causing local load variations. To prevent this, different studies of the propulsion shaft system have been conducted focused the relative inclination angle and oil film retention between the shaft and the support bearing, mainly with respect to the Rules for the Classification of Steel Ships. However, in order to secure the stability of the propulsion shaft via a more detailed evaluation, it is necessary to consider dynamic conditions, including the transient state due to sudden change in the stern wakefield. In this context, a 50,000 DWT vessel was analyzed using the strain gauge method, and the effects of propeller shaft movement were analyzed on the starboard rudder turn which is a typical transient state during normal continuous rate(NCR) operation in ballast draught condition. Analysis results confirm that the changed propeller eccentric thrust acts as a force that temporarily pushes down the shaft to increase the local load of the stern tube bearing and negatively affects the stability of the shaft system.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.717-726
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• 2017

The current allowable cross-contamination level of fatty acid methyl esters (FAME) in aviation turbine fuel (AVTUR) is 50 mg/kg, due to that the presence of FAME in AVTUR can significantly impact the fuel supply system and jet engine. It has been difficult to analyze the level of FAME in AVTUR, since it is consisted of a lot of hydrocarbons. In this study, thus, a new method using multi-dimensional GC-MS (MDGC-MS) was proposed in order to determine the FAME level in AVTUR effectively. Applying to MDGC-MS with Deans switching system enabled us to detect and quantify the FAME with low carbon numbers such as those derived from coconut oil and palm kernel oil. The matrix effect of MDGC-MS method, which could shift the FAME peaks to slightly longer retention times, was reduced by 20 times compared with that of 1-dimensional GC-MS reference method. This developed method could be suitable for qualitative and quantitative analyses to determine the contamination level of trace FAME in AVTUR.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.653-662
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• 2014

In this study, Mokpo national maritime university Training ship Centralizes Air Conditioning System was upgraded by installing onboard an Air-cooled Air conditioner. This resulted in the improvement of the performance and operation. This study compared refrigeration performance to former equipment and improving one. And through the actual measurement study about the cabin thermal environment, it will be used as basic data for marine air conditioning design and plan in the future. At same climate condition, when the Centralized Air Conditioning System and an improved air conditioning system operated, cabin temperature was at $24{\sim}28^{\circ}C$, humidity was 55~75 % as comfortable condition, Generator load measurement showed a saving of 48KW in the average load and 8 % in the full load factor. This also resulted in a saving of daily fuel oil consumption(FOC) at around 222 [${\ell}/day$] average. On the other hand, one cadet cabin(Cadet No.21) indicated a higher temperature due to heat transmission of engine room. It found us not to consider installing additional diffuser to reduce the heat transmission.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1199-1206
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• 2015

In this study, the exhaust gas of a diesel engine operating on biodiesel(BD) fuel(a mixture of diesel and soybean oil) was investigated for different fuel mixing ratios in the range of BD3 to BD100. The experiments were conducted using injection pressures of 400, 600, 800, 1000, and 1200 bar. The Pearson correlation coefficient and Spearman rank-order correlation coefficient were used to quantify the NOx and Soot emissions based on the fuel mixing ratio and injection pressure. Consequently, the Pearson correlation coefficient obtained for NOx and Soot emissions according to the mixing ratio and injection pressure was -0.811 and the corresponding Spearman rank-order correlation coefficient was -0.884, which indicated that the correlation of the NOx and Soot emissions was linear. Thus, the NOx and Soot have a trade-off relationship. Moreover, at each injection pressure, the Pearson correlation coefficient was a negative number, which indicated an inversely proportional relationship between NOx and Soot.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1237-1244
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• 2015

A gerotor can be manufactured in a miniature size because it has a high discharge per cycle and a simple structure. Gerotors are widely used for the lubrication oil of an engine and as the hydraulic source of an automatic transmission. Recently, improvements in fuel efficiency and noise reduction have come to the fore in the automobile industry, and it has been necessary for better fuel efficiency to continuously improve the flow rate and noise of internal gear pumps through the optimal design of the gerotor and port shape. In this study, gerotors were generated based on the equations derived for a lobe shape with multiple profiles (ellipse 1-elliptical involute-ellipse 2). The ranges of the design parameters were considered to prevent a cusp and loop. In addition, the optimal lobe shape was obtained by determining the influence of the lobe shape on the performances (flow rate, irregularity, etc.), according to the values of the design parameters.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.60-60
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• 2017

화석연료의 고갈과 환경오염이 문제시 되면서 친환경 에너지개발에 대한 연구가 진행되고 있다. 그중 바이오디젤은 동,식물성유지 및 폐식용유를 이용하여 생산이 가능할뿐더러 농용엔진에 특별한 개조 없이 사용가능하다. 또한 바이오디젤 자체에 산소를 함유하고 있어 이산화탄소 저감에 효율적이다. 바이오 디젤에 관한 많은 연구가 수행되었으며, 기존의 연구는 단일유지의 폐식용유를 사용하여 바이오디젤을 생산하는 연구가 진행되었다. 하지만 가정에서 배출되는 식물성 폐식용유의 경우 여러 가지가 혼합되어 배출되고 있어, 혼합폐식용유지의 바이오디젤 특성평가가 필요하다. 따라서 본 연구에서는 폐식물성유지(폐대두유, 폐카놀라유, 폐해바라기유)를 중량비(1:4, 1:1.5 1:0.66, 1:0.25)로 혼합하여 바이오디젤을 생산하고, 생산한 바이오디젤을 농용기관에 이용하여 농용기관의 출력특성 및 배기배출물특성 평가를 실시하였다. 실험에 사용된 농용기관은 배기량이 673cc인 직접분사식 디젤기관(ND10DE, Daedong, Korea)이며, 엔진성능평가를 위해 토크는 토크센서(YDL-704s, Setech, Korea)를 사용하였다. 배기배출물 평가는 배기가스분석기(HG-550, Airlex, Germany)를 이용하여 이산화탄소, 질소산화물을의 배출량을 측정하였다. 폐식용유를 이용하여 생산한 바이오디젤과 경유의 기관성능을 비교한 결과 토크와 축출력의 경우 BD의 혼합량이 증가할수록 줄어들었다. 토크는 혼합된 유지에 따라 상용운전범위인 1500rpm~2400rpm에서 평균 대두와 카놀라유를 혼합하여 생산한 BD10은 7.2%, BD20은 12.1% 감소하였고, 대두와 해바라기유를 혼합하여 생산한 BD10은 11.3% BD20은 16.3% 감소하였다. 또한 해바라기와 카놀라유를 혼합하여 생산한 BD10은 8.3%, BD20은 14.6% 감소하였다. 이는 BD의 발열량이 경유에 비해 낮아 토크가 감소한 것으로 판단된다. 또한 배기배출물 평가의 경우 질소산화물은 BD의 함랑이 증가함에 따라 경유에 비해 배출량이 증가하는 경향을 보였고, 이산화탄소는 저감되는 것으로 나타났다. 이는 바이오디젤이 함산소연료이므로, 연료내의 산소로 인해 완전연소를 촉진시켜 이산화탄소를 저감시키고 질소산화물은 증가된 것으로 판단된다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.29-36
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• 2015

Exact comparisons of the thermal conductivities of the base fluid and a nanofluid are very important in the early stages of nanofluid development. A simple procedure of measuring the thermal conductivity of the two fluids by the transient hot wire method and numerically dividing these values is used for this purpose. However, because the experiments are not performed simultaneously and the physical properties of the measurement system are sometimes not properly known, large errors are incurred during the evaluation process. This article proposes a new apparatus for thermal conductivity comparison where the working principle is mainly based on relative measurement rather than absolute measurement. The measuring circuit and data processing steps are explained in detail; a validation test was performed using the well-known glycerine and engine oil.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.133-138
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• 2005

Automotive pulleys play a key role in driving the cooling pump, oil pump, air-conditioner and so on by using an engine power. Researches on design processes and technologies of the pulleys can be found in many literatures. On the other hand, the areas related to manufacturing processes of the pulleys have been treated negligently. Vast data extracted from various information systems are transformed, integrated, and summarized to become a special database for helping users make a decision. The database, namely the data warehouse has been popularly used in the marketing and customer management of enterprises and recently applied to improve the design and manufacturing processes. In this study the manufacturing process of pulleys were analyzed through the intensive investigation of shop-floors and the interviews with workers and managers. The defects generated during a manufacturing process were categorized in a few types and the causes of defects examined for extracting the dominant parameters in the setup process for producing pulleys. As the first step to construct the data warehouse for the manufacturing processes of pulleys, authors proposed its architecture focused on the reduction of defect rate during the setup process.