• 한국자동차공학회논문집
• /
• 제7권8호
• /
• pp.17-23
• /
• 1999

This paper presents the characteristics of the gas flow in the engine cylinder under various intake flow conditins. The particle tracking velovimetry(PTV) was used to anlayze the gas flow pattern and flow field in the cylinder. Effects of tumble intensifying valve(TIV), swirl intensifying valve(SIV) and one-valve deactivated condition on in-cylinder flow patterns were compared with the baseline engine udner 600rpm motoring condition. In addtion, tumbel ration was estimated rwith results of in -cylinder flow fields. Base on experimental results, the tumble ration of in-cylinder flow field has the maximum value at the bottom dead center for the different four inlet conditions. In TIV condition, the tumble ration is 1.35 times larger than that of baseline engine and 1 intake valve deactivated condition is effective to improve in-cylinder swirl motion.

• 한국산학기술학회논문지
• /
• 제14권12호
• /
• pp.6125-6132
• /
• 2013

본 연구목적은 사회적언어 사용과 거친 신체놀이의 관계를 알아봄으로써 사회적언어를 활용하여 거친 신체놀이를 증진시킬 수 있는 프로그램 개발을 위한 기초자료를 제공하는 것이다. 연구문제는 첫째, 유아의 사회적언어 사용과 거친 신체놀이는 어떠한 관계가 있는가? 둘째, 유아의 사회적언어 사용은 거친 신체놀이에 어떠한 영향을 미치는가? 연구대상은 충남 N시의 유아 90명이며 평균 78개월이었다. 연구결과는 첫째, 거친 신체놀이 전체는 사회적언어의 하위영역인 제안, 평가, 주의집중, 차례지정, 경고, 명령과 정적상관이 나타났다. 다만 달리기와 거부는 부적상관이 나타났다. 둘째, 유아의 거친 신체놀이 중 유아의 도망가기 놀이에는 경고, 명령의 사회적언어, 놀리기는 평가, 명령의 사회적언어, 밀고 당기기의 놀이는 명령, 승낙, 추정의 사회적언어가 정적영향력이 있었으며 행위요구는 부적영향이 나타났다. 치기 찌르기의 놀이는 개인적 요망, 주장과 정적영향, 넘어지기는 제안, 명령이 정적영향이 있었으며 거부는 부적영향이 나타났다. 잡기는 제안, 주의집중이 정적영향이 나타났으며 행위요구는 부적영향이 나타났다. 달려들기는 경고가 정적 영향력이 있었으나 거부는 부적영향이 나타났다. 몰래다가가 놀래키기는 예절표시가 정적 영향을 미치는 것으로 나타났다. 유아들이 사회적 관계를 형성할 수 있는 거친 신체놀이를 위해서는 사회적언어 사용 전략을 활용한 프로그램이 개발 되어야 할 것이다.

• Journal of Mechanical Science and Technology
• /
• 제17권12호
• /
• pp.2027-2033
• /
• 2003

The purpose of this study is to investigate the stratification of fuel vapor with different in-cylinder flow, piston cavity and injection timings in an optically accessible engine. Three different piston shapes that are F(Flat), B(Bowl) and R(Re-entrance) types were used. The images of liquid and vapor fuel were captured under the motoring condition using Laser Induced Exciplex Fluorescence technique. As a result, at early injection timing of 270 BTDC, liquid fuel was evaporated faster by tumble flow than swirl flow, where most of fuel vapor were transported by tumble flow to the lower region and both sides of cylinder for the F-type piston. At late injection timing of 90 BTDC, tumble flow appears to be moving the fuel vapor to the intake side of the cylinder, while swirl flow convects the fuel vapor to the exhaust side. The concentration of mixture in the center region was highest in the B-type piston, while fuel vapor was transported to the exhaust side by swirl flow in F and R-type pistons. At the injection timing of 60 BTDC, the R-type piston was better for stratification due to a relatively smaller bowl diameter than the others.

• 한국자동차공학회논문집
• /
• 제10권2호
• /
• pp.23-30
• /
• 2002

This present study experimentally investigates the behavior of liquid and vapor phase of fuel mixtures with changing the in-cylinder air motion in an optically accessible engine. The conventional MPI/DOHC engine was modified to gasoline direct injection engine with swirl motion. The images of liquid and vapor phases were captured in the motoring operation condition using exciplex fluorescence method. Two dimensional spray fluorescence images of liquid and vapor phases were acquired to analyze spray behaviors and fuel distribution inside of cylinder respectively, In early injection timings $(BTDC\;270^{\circ},\;180^{\circ})$, tumble flow transported most of vapor phase to the lower region and the both sides of cylinder, so vapor phase didn't become uniform distribution up to the half of the compression stroke. In the case of swirl flow, the fuel mixture was confined near the swirl origin in upper region of cylinder. In late injection timings $(BTDC\;90^{\circ})$, tumble flow transported vapor phase to the intake valve and swirl flow to the exhaust valve.

• 한국자동차공학회논문집
• /
• 제14권3호
• /
• pp.142-149
• /
• 2006

A PIV(Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake stroke. Two engines, one is conventional DOHC 4 valve and the other is narrow valve angle, were used to compare real intake flow. The results show that the intake flow pattern of conventional engine is more complicated than that of narrow angle one in horizontal plane and the vertical component of in-cylinder flow is rapidly decayed at the end stage of intake. On the other hand, the flow pattern of narrow angle one is relatively well arranged in horizontal plane and the vertical velocity component remains so strongly that forms large-scale strong tumble. Two engines also form commonly three tumble; two are small and bellow the intake valve and one is large-scale. The center of large scale tumble moves to bottom of cylinder as the vertical velocity increases.

• Journal of Advanced Marine Engineering and Technology
• /
• 제32권4호
• /
• pp.498-505
• /
• 2008

Many researches have been studied on in-cylinder flow as one of dominant effects for an engine combustion. The combustion phenomena of reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. To know this relationship definitely, this paper describes analytical results of the tumble motion, swirl motion, turbulence intensity, turbulence inside the cylinder of marine engine. 3-D computation has been performed by using STAR-CD solver and es-ice.

• 대한기계학회논문집B
• /
• 제34권3호
• /
• pp.219-228
• /
• 2010

텀블형 드럼 건조기의 적외선 건조 과정동안의 온도 및 수분량의 변화를 예측할 수 있는 2 차원 수학적 모델을 개발하였다. 본 모델에서는 건조대상 물질의 액체 수분의 이동과 건조공기의 유동 및 열전달을 고려하였다. 유체의 유동과 열전달 현상, 그리고 복사열전달은 유한체적법을 이용하여 해석하였다. 텀블 건조기의 2 차원 모델을 모사하기 위한 지배방정식을 소개한 후 적외선 히터, 히터의 온도, 그리고 가열 패턴에 따른 수치해석을 수행하였고, 적외선 히터를 도입함으로써 건조시간을 감소시킬 수 있음을 제시하였다.

• 한국전산유체공학회지
• /
• 제4권3호
• /
• pp.21-27
• /
• 1999

In this paper, tile characteristics of flow resulting from the configurations of piston head and intake-port of the cylinder in a gasoline-direct-injection engine are investigated numerically. Calculations are carried out from intake process to the end of compression. GTT code which includes the third order upwind Chakravarthy-Osher TVD scheme and κ-ε turbulence model with the law of wall as a boundary condition. As a result, a piston head with a smaller radius of curvature and larger radius gives stronger reverse tumble. It is also shown that as the maximum tumble ratio increases by the configuration of the intake-port the tumble ratio at the end of compression stroke increases. It is concluded that flows at the end of compression stroke can be controlled by the optimum design of intake-port and piston head.

• 한국자동차공학회논문집
• /
• 제9권3호
• /
• pp.1-8
• /
• 2001

The flow field inside a cylinder of four-valve Sl engine was investigated quantitatively using a three-dimensional Laser Doppler Velocimetry system, to determine how stroke changes affect the flow field. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance. For this study, the sane intake manifold, engine head, cylinder, and the piston were used to examine the flow characteristics in different strokes. Quantification of the flow field was done by calculating three major parameters which are believed to adequately characterize in cylinder motion. These quantities were TKE, tumble and swirl ratios. The LDV results reveal that flow patterns are similar, the flow velocities scale with piston speed but another parameters such as TKE, and tumble and swirl numbers are not the same for different stroke systems.

• 한국유체기계학회 논문집
• /
• 제10권4호
• /
• pp.47-54
• /
• 2007

Simultaneous 3-D LDV measurements of the in-cylinder flows of three different engine setups were summarized for the quantification of the flow characteristics in each vertical or horizontal plane, and in entire cylinder volume. The ensemble averaged-velocity, tumble and swirl motions, and turbulent kinetic energy during the intake and compression strokes were examined from the measured velocity data (approximately 2,000 points for each engine setup). The better spatial resolution of the 3-D LDV allows measurements of the instantaneous flow structures, yielding more valuable information about the smaller flow structures and the cycle-to-cycle variation of these flow patterns. Tumble and swirl ratios, and turbulent kinetic energy were quantified as planar and volumetric quantities. The measurements and calculation results were animated for the visualization of the flow, and hence ease to analysis.