• 오토저널
• /
• 제15권3호
• /
• pp.55-67
• /
• 1993

In this study, the thermal behavior characteristics of the cylinder block of a small 3-cylinder, 4-stroke gasoline engine were analyzed, using the 3-dimensional finite element method. Before numerical analyses were conducted, the performance test and the heat transfer experiment of the engine were carried out in order to prepare the input data for the computations. Engine cycle simulation was performed to obtain the heat transfer coefficient and the temperature of the gas and the mean heat transfer coefficient of coolant. Temperature fields as a result of steady-state heat transfer were obtained and compared with experimental results measured at specific points of the inner and the outer walls of the cylinder block. The thermal stress and deformation characteristics resulting from the nonuniform temperature distributions of the block were investigated. The effects of the thermal behaviors of the cylinder block on the engine operations and the unfavourable aspects of excessive thermal loading were examined on the basis of the calculated results.

• Journal of Advanced Marine Engineering and Technology
• /
• 제29권6호
• /
• pp.671-677
• /
• 2005

In internal combustion engines the usual material for the cylinder liner is because of its good wear resistance Apparently this wear resistance arises from the at iron to form a hard glazed surface when under sliding friction. When the cylinder liner wear limits, it shall be replace with new one according to the classification soci manufacturer's standards. However, adoption of alternative repairing method such a metalizing, thermo plastic deformation process became inevitable taking enormous cost renewal into consideration. In this paper. the material properties of cylinder liner of grey discussed on the basis of the results of experimental work of the thermo plastic deformation the worn out cylinder liner made of grey cast iron.

• 대한기계학회논문집
• /
• 제8권5호
• /
• pp.498-504
• /
• 1984

가열된 곡면에 의한 자연대류에서는 유동의 박리현상이 존재하지 않음이 알려져 있다. 이에 반해 날카로운 모서리를 갖는 가열된 정방형 수평실린더에 의한 자연대류에서는 그라소프 수가 4.66*$10^{4}$ 전후로 부착 혹은 박리현상이 윗쪽 양 모서리 부근에서 일어남을 광학간섭 계(Mach Zehnder Inter-ferometer)를 이용하여 온도장을 가시화하고 이를 이용하여 좌우 대칭 선상에서의 속도분포를 간단한 대수적인 방법으로 구하여 수평정방형 윗쪽 수평면 위에 유동의 박리현상을 시사하는 "쌍동이 소용돌이"의 존재를 입증하였고, 이에 의해 온도역전현상과 평균 열전달량의 급격한 증가를 설명 할 수 있다.설명 할 수 있다.

• 대한기계학회논문집B
• /
• 제30권6호
• /
• pp.587-593
• /
• 2006

A ventilated disc brake having semi-cylindrical grooves has been proposed to improve the thermal judder by way of heat transfer enhancement. The local heat transfer coefficients were measured in the flow passage of disc brake. These measured local heat transfer data were utilized to do the finite element numerical analysis which predicts the maximum temperatures on the disc brake. The results show that the maximum temperatures on the disc surface with semi-cylindrical grooves are approximately 35.2% lower than those without them.

• 한국자동차공학회논문집
• /
• 제10권6호
• /
• pp.1-10
• /
• 2002

As the preliminary stage for the countermeasure of thermal loading in miller cycle engine, coolant flows in the cylinder head of base engine including exhaust valve bridge were visualized and analyzed by using PIV technique. It was found that low coolant velocity regions were around exhaust valve bridge, around which stagnation of the coolant flow was observed due to the complex geometry configuration of water jacket. And velocity variation between each cylinder was remarkable. For the countermeasure of these, it is necessary to enhance coolant flow around exhaust valve bridge and to improve the deviation of coolant flow between each cylinder.

• 설비공학논문집
• /
• 제8권1호
• /
• pp.26-36
• /
• 1996

Many researches were carried out to estimate heat transfer rate on a circular cylinder in a uniform flow. Various empirical correlations were suggested in the past through experimental studies, however there are considerable discrepancies in the estimated values of heat transfer coefficient. The effect of fluid physical properties on the forced convective heat transfer between a circular cylinder and the external flow was numerically investigated in the present study, The flow and temperature fields were solved using a Finite Volume Method over a wider range of Prandtl number(0.7-40,000) than existing correlations. The cold as well as the hot cylinders in the uniform liquid flow of constant temperature were investigated. A unified correlation was obtainde for both cases.

• 대한기계학회논문집B
• /
• 제28권11호
• /
• pp.1449-1458
• /
• 2004

The influence of eccentric(=staggeredness) ratio between stationary upstream circular cylinders on heat transfer characteristics of a heated downstream circular cylinder installed in a channel was investigated experimentally. In order to enhance the heat transfer rate of the heated downstream cylinder surface, we have changed the configuration of upstream cylinder. As a result, we were able to obtain local time-averaged convective heat transfer enhancement of the heated cylinder by the relative replacement of upstream cylinder. This is basically attributed to the mean flow structure change, such as flow separation, vortex shedding, and recirculation of the upstream cylinder including the reattachment and new thermal boundary developed at the downstream cylinder which are the results of the increase of the staggeredness ratio.

• 한국기계가공학회지
• /
• 제18권2호
• /
• pp.73-81
• /
• 2019

Numerical simulations are performed for the thermal fluid flow around a circular cylinder, and the particle trajectories are calculated to investigate the particle motions and deposition characteristics. We aim to understand the effects of three important parameters (particle Stokes number, temperature difference in the flow and on the cylinder surface, and thermal conductivity ratio between the fluid and the particles) on the deposition efficiency. The results show that the thermophorectic effect is insignificant for particles with large Stokes numbers, but it affects particles with small Stokes numbers. The deposition efficiency increases with the increase in temperature difference between the flow and the cylinder or the decrease in ratio of thermal conductivity of the particles to the fluid. When thermophoresis becomes significant, the particles are deposited even on the back side of the cylinder.

• 자동차안전학회지
• /
• 제6권1호
• /
• pp.33-40
• /
• 2014

In this study the cylinder liner deformation which is one of the most influencing factors in a diesel engine oil consumption was performed by the finite element analysis on the basic designed structure consisting of the cylinder block, head and liners under the conditions of assembly, thermal and gas loads. Compared with a large number of other cylinder blocks showing remarkable harmonic orders of the liner distortion, results are excellent. Namely. the higher harmonic order amplitudes of the radial liner deformation amount to 1 ~ 2㎛ maximally. The main reason lies in the relatively large wall thickness of the liner which amounts to 8.2% of the bore diameter. Besides, a very stiff and symmetrical cylinder block design in combination with a bolt force introduction approximately 1.5mm below the block top deck have a further share on these results. Therefore excellent low oil consumption can be expected.

• 한국융합학회논문지
• /
• 제12권2호
• /
• pp.185-191
• /
• 2021

본 자동차 실린더 블록 주조시 실린더 보어 내에서 발생하는 열로부터 구조적 변형을 방지하는데 필요한 워터 자켓 코어용 주물사의 특성을 분석하였다. 샌드 코어의 특성평가를 위하여 인장강도 시험기, 입도 지수(AFS-GFN), 광학현미경을 사용하였다. 주물사의 SiO2 함량이 높으면 고온팽창에 의한 치수 불량, 베이닝 불량이 발생하며, 너무 낮으면 코어 파손, 기포, 화학적 소착 등이 발생하였다. 입도 지수와 입형이 코어강도와 레진 소비량에 영향을 미치고, 이로 인한 불량 유형 변화가 발생하였다. 건조사가 염분이 높을수록 코어 강도는 감소하며, 알칼리성일수록 코어 강도가 감소하였다. 레진 함량 1.6~1.8%에서 1시간 경화 이후에 코어 강도 증가는 대략 최대를 보였다.