• Tribology and Lubricants
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• 제25권1호
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• pp.1-6
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• 2009

In this paper, the minimum oil film thickness and the maximum oil film pressure of engine bearings have been analyzed by using the elastohydrodynamic theory and Taguchi's design method as functions of the oil groove width, oil hole diameter, oil hole position, and oil supply pressure. The optimized design of the engine bearing f3r an automotive Diesel engine is very important for supporting a load-carrying capacity due to gas pres-sures from the engine combustion chamber and inertia forces of the piston. The optimized design data of engine bearings indicated that the optimized oil groove width and an oil diameter of a engine bearing are 8mm at the speed of 2,000 rpm for a given 4-cylinder Diesel engine. Thus, the oil groove oil groove and an oil hole for high performances of an engine bearing may be considered as major design parameters compared to other design factors, which are strongly related to the minimum oil film thickness and the maximum oil pressure distribution of the engine oil.

• 소성∙가공
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• 제25권6호
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• pp.390-395
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• 2016

GDI fuel rail is component of GDI system which directly fuel with high pressure in the engine combustion chamber. And it is required to high strength and dimensional accuracy. Multi roll-die drawing process consists of the idle roll-die and drawing die in tandem. In the course of drawing with roll-die, deformation takes place between the idle roller pair or pairs. The friction force decreases with the idle roll-die, enabling the reductions to be risen in one step. In this study, the caliber of 4-roll was designed into pass schedule that made the draw force at the exit of the drawing die be equal. In order to compensate for over-filling area, the roll caliber was modified using the result of FE-analysis. The results of FE-analysis and experiment show that the proposed design method can be used to effectively design the multi roll-die process, leading to an accurate shape and correct dimensions of the final within an allowable tolerance of ${\pm}0.08mm$. Furthermore, the productivity was evaluated by comparing with multi roll-die drawing process and conventional multi shape drawing process. The result was confirmed that it has an efficiency of about 2 times than conventional process in terms of time.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.539-542
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• 2006

Many researches about next generation vehicles are trending toward HEV which has better fuel economy than an internal-combustion engine. But existing HEV has some defects at specific running states(eg. highway running It is possible that dual-mode hybrid system overcomes that defects. Mode change parameter, ${\gamma}$ helps to analyse the mode changing of dual mode hybrid and is applied at a numerical analysis on testing the performance. There is an additional constraint when vehicles drive on engine mode. No power assistance of battery applies on engine mode. Because vehicles must be sustained by only engine power while vehicle drives on constant speed mode. At the conclusion of this paper, graphs show the ability of motors that satisfy the equilibrium of the lever system. Designers can roughly determine capacities of the motors, parameters of the lever system by this analysing method.

• 한국화재소방학회논문지
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• 제25권2호
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• pp.114-119
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• 2011

폭발한계와 인화점은 가연성물질의 화재 및 폭발의 위험성을 결정하는데 중요한 연소특성치이다. 본 연구에서는 산류와 케톤류의 폭발상한계를 예측하기 위해서, 평형상태에서 인화점을 측정하는 Setaflash 밀폐식 장치(ASTM D3278)를 사용하여 이들의 상부인화점을 측정하였다. 측정된 상부인화점을 이용하여 Antoine 식에 의한 계산된 폭발상한계는 기존의 문헌값들보다 약간 낮게 나타났다. 본 연구에서 제시한 실험 및 예측 방법을 이용하여 다른 가연성물질의 폭발상한계 예측이 가능해 졌다.

• 한국화재소방학회논문지
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• 제26권4호
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• pp.18-23
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• 2012

이산화탄소 주조법에서 사용되고 있는 방법을 응용하여 목질내에 규산겔과 탄산소다, 이산화규소가 석출된 목재를 제조한 후 외부 복사열원(20, 25, 35 및 50 $kW/m^2$)에 따른 점화시간, 점화온도, 질량감소속도, 임계열유속을 측정하였다. 연구결과, 물유리와 이산화탄소를 이용한 가압함침 처리된 목재는 Pre-Flashover 단계에서의 복사열원(20 $kW/m^2$ 이하)에서 난연성능이 있음을 확인할 수 있었다. 향후 지속적인 연구를 통해 우수한 배합비율을 찾는다면 난연목재로서의 활용가능성이 있다고 판단된다.

• 대한금속재료학회지
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• 제50권5호
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• pp.369-374
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• 2012

Nanopowders of Mo, Ta and Si were made by high-energy ball milling. A dense nanostructured $MoSi_2-TaSi_2$ composite was sintered by the high-frequency induction heated combustion method within 2 minutes from mechanically activated powder of Mo, Ta and Si. A highly dense $MoSi_2-TaSi_2$ composite was produced under simultaneous application of a 80 MPa pressure and the induced current. Mechanical properties and microstucture were investigated. The hardness and fracture toughness of the $MoSi_2-TaSi_2$ composite were $1200kg/mm^2$ and $3.5MPa.m^{1/2}$, respectively. The mechanical properties were higher than those of monolithic $MoSi_2$.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.274-277
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• 2004

ATR 엔진 연소기 내부에서의 연료와 공기의 혼합성능은 연소 안정성이나 효율에 지배적인 요인이 된다. 본 연구에서는 ATR 모델 연소기에서의 혼합성능을 비교하기 위하여 두 유체의 속도 비$(r=v_a/v_f)$를 변화시키면서 연료분포를 측정하였다. 측정 방법으로는 2차원 연료분포를 얻기 위하여 널리 이용되는 평면레이저 유도형광기법과 화상처리 기법을 사용하여 연료분포 이미지를 얻었다. 측정된 연료분포 화상으로부터 공기속도/연료속도 비가 1에 가까울수록 연료 혼합성능이 떨어지는 특성을 관찰하였다.

• Journal of Magnetics
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• 제21권4호
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• pp.537-543
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• 2016

Currently, an interest in electric vehicles (EVs) exhibited by automakers, government agencies and customers make it as more attractive research. This is due to carbon dioxide emitted by conventional combustion engine that worsens the greenhouse effect nowadays. Since electric motors are the core of EVs, it is a pressing need for researchers to develop advanced electric motors. As one of the candidates, switched flux machine (SFM) is initiated in order to cope with the requirement. This paper proposes a new alternate circumferential and radial flux (AlCiRaF) of permanent magnet switched flux machines (PMSFM) for light weight electric vehicles. Firstly, AlCiRaF PMSFM is compared with the conventional PMSFM based on some design restrictions and specifications. Then the design refinements techniques are conducted by using deterministic optimization method in order to improve preliminary performance of machine. Finally the optimized machine design has achieved maximum torque and power of 47.43 Nm and 12.85 kW, respectively, slightly better than that of conventional PMSFM.

• 전력전자학회논문지
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• 제24권1호
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• pp.9-15
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• 2019

Sensorless electric superchargers have recently been actively developed to provide a large amount of oxygen to engines in order assist the combustion process for miniaturizing the engines and improving fuel efficiency. The model-based sensorless method for surface-mounted permanent magnet synchronous motors has a disadvantage in that the system may become unstable due to parameter variations in low-speed operation and the rapid-acceleration section. An electric supercharger requires fast response to improve the engine response delay, such as the turbocharger turbo-rack. Therefore, the responsiveness must be improved to use the model-based sensorless system. The position compensation algorithm designed in this study is controlled by converting the position error into the beta, which is the angle formed by the d-axis and the stator current during sudden speed change. In this study, we improved the response of the model-based sensorless system through the algorithm and verified the algorithm validity by applying the algorithm to an actual dual-motor supercharger.

• 한국군사과학기술학회지
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• 제22권1호
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• pp.27-34
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• 2019

This paper presents a chamber pressure model development of K2 rifle by applying Gaussian mixture model. In order to materialize a real recoil force of a virtual reality shooting rifle in military combat training, the chamber pressure which is one of major components of the recoil force needs to be investigated and modeled. Over 200,000 data of the chamber pressure were collected by implementing live fire experiments with both K100 and M193 of 5.56 mm bullets. Gaussian mixture method was also applied to create a mathematical model that satisfies nonlinear, asymmetry, and deviations of the chamber pressure which is caused by irregular characteristics of propellant combustion. In addition, Polynomial and Fourier Regression were used for comparison of results, and the sum of squared errors, the coefficient of determination and root-mean-square errors were analyzed for performance measurement.