• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.557-563
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• 2002

In this paper, the characteristics of flow and spray motions affected by from piston head configurations were investigated numerically. Calculations were carried out from intake process to the end of compression. GTT (Generalized Tank and Tube method) code, which includes a third order upwind Chakravarthy-Osher TVD scheme and k-$\varepsilon$ turbulence model with fuel spray analysis was used for the calculations. As a results, piston heads with smaller radii of curvature were found to give stronger reverse tumble than those with larger radii of curvature. Similar results are shown in the convection and diffusion of fuel sprays.

• 대한기계학회논문집B
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• 제24권6호
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• pp.880-885
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• 2000

Flow patterns and steady flow characteristics of an intake 3valve cylinder head are not obviously declared. Thus, in the study, the characteristics and limitation of intake flow coefficient which applied to multi intake valve engine are introduced. The flow coefficient and tumble characteristics are investigated by means of the steady flow test and flow visualization method. As the results, it is found that the intake flow rate is dominated by effective valve open area. In addition, this paper shows that the mass flow rate of intake 3valve engine is greater than that of intake 2valve engine and tumble flow of intake 3valve engine is superior to that of intake 2valve engine.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.188-198
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• 1995

Turbulent flow characteristics of a lean-burn engine were qualitatively studied in order to obtain the optimum design parameters. 3-D lean-burn model engine was made up of an intake port, an intake valve and a cylinder. Computational grids were generated using PATRAN which was a FEM grid-generation software and numerical calculations were performed using STAR-CD. The predicted results showed that swirl and tumble structures were significantly changed by the valve lifts.

• 한국의류산업학회지
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• 제20권3호
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• pp.331-342
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• 2018

This paper enables stakeholders involved in textile industry to gain an overview of standards used for care labelling and help establish a common standard that could be used as a universal standard. This study provides a comprehensive and detailed analytical study of care labelling standards adopted by common countries in the textile market. It was found that the development of a universal system for care labeling could enhance the trade of textile articles and assist consumers in caring for textile articles. Universal care label systems could be characterized by two main features of inclusiveness and comprehensiveness. The range of instructions and symbols presented were found different among standards. Insignificant differences in symbols' shapes were found between standards for bleaching, ironing and professional cleaning. The washing process had the widest variety of instructions; in addition, options were provided by stated standards. Different meanings were found for similar shapes in some tumble drying symbols. The study findings show the importance of enhancing text based standards or the development of an understandable format across as many cultures as possible. The unification of symbols and meanings may be needed to provide global consumers consistent guidance. The efficiency of a detailed standard that provides and covers a wide range of instructions is an important aspect. The visibility and practicality of offering variable options/symbols in one standard is an important aspect for developing a universal care label system.

• 한국자동차공학회논문집
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• 제8권6호
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• pp.51-59
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• 2000

In-cylinder spray flow motion plays an important in the adjustment of mixture preparation with a fundamental spray characteristics and in-cylinder flow field well in direct-injection gasoline engine. In this study, the fundamental spray characteristics such as mean drop size, velocity distribution, spray angle were measured and in-cylinder spray flow motion was visualized in order to optimize intake port, piston top land and combustion chamber shapes in the development stage of mass-produced G야 engine. For these experiments, the PDPA measurements and Mie scattering technique were used for detailed spray characteristics and in-cylinder spray motions were obtained by use of ICCD camera through the single-cylinder optical engine. From the experimental results, the test injector shows a good low-end linearity between the dynamic flow and fuel injection pulse width and the fuel spray of 20mm or less in SMD with good spray symmetry. In addition, the in-cylinder tumble flow has more effect on the homogeneous mixture formation than that of in-cylinder swirl flow at early injection mode and the in-cylinder swirl flow plays a better role of stratified mixture preparation than tumble flow at late injection mode.

• 한국연소학회지
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• 제1권1호
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• pp.65-73
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• 1996

Flame propagation in a four-valve spark-ignition optical engine was visualized under lean-bum conditions with A/F=18 at 2000rpm. The early flame development in a four-valve pentroof-chamber single-cylinder engine was examined with imaging of the laser-induced Mie scattered light using an image-intensified CCD camera. Flame profiles along the line-of-sight were also visualized through a quartz piston window. Two-dimensional flame structures were visualized with a Proxitronic HF-1 fast motion camera system by Mie scattering from titanium dioxide particles along a planar laser sheet generated by a copper vapor laser. The flame propagation images were subsequently analysed with an image processing programme to obtain information about the flame structure under different tumble flow conditions generated by sleeved and non-sleeved intake ports. This allowed enhancement of the flame images and calculation of the enflamed area, and the displacement of its center, as a function of the tumble flow induced by the pentroof-chamber in the vicinity of spark plug. Image processing of the early flame development quantified the correlation between flame and flow characteristics near the spark plug at the time of ignition which has been known to be one of the most important factors in cyclic combustion variations in lean-burn engines. The results were also compared with direct flame images obtained from the natural flame luminosity of the lean mixture.

• 대한기계학회논문집B
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• 제30권11호
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• pp.1066-1073
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• 2006

Recently, because the variable induction systems are adopted to intake system, in-cylinder flow induced by induction system is very complex. Therefore it is very difficult to describe the in-cylinder bulk flow characteristics using the conventional swirl or tumble coefficient. In this study, in order to clarify the 3-D angular flow characteristics of in-cylinder bulk motion in the developing process of variable induction system, we introduced the new 3-D angular flow index, angular flow coefficient($N_B$) Finally, to confirm the index, we carried out the steady flow rig test for intake port of test engine varying valve lift on the test matrix.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.704-715
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• 2005

In this study, to investigate in-cylinder tumble or swirl intake flow of a gasoline engine, the flow characteristics were examined with opening control valve (OCV) and several swirl control valves (SCV) which intensify intake flow through steady flow experiment, and also turbulent characteristics of in-cylinder flow field were investigated by 2-frame cross-correlation particle image velocimetry (PIV) method. In the investigation of intake turbulent characteristics using PIV method, the different flow characteristics were showed according to OCV or SCV figures. The OCV or SCV installed engine had higher vorticity and turbulent kinetic energy than a baseline engine, especially around the wall and lower part of the cylinder. Above all, SCV B type was superior to the others. About energy dissipation and reynolds shear stress distribution, a baseline engine had larger loss than OCV or SCV installed one because flow impinged on the cylinder wall. It should be concluded, from what has been said above, as swirl component was added to existing tumble flow adequately, it was confirmed that turbulent intensity was enlarged, flow energy was conserved effectively through the experiment. In other words, there is a suggestion that flow characteristics as these affected to in-cylinder combustion positively.

• 대한기계학회논문집
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• 제18권4호
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• pp.920-932
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• 1994

The combustion phenomena of a 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, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. 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. This paper describes cycle resolved LDV measurement of turbulent flow inside the cylinder of a 4-valve engine under motoring(non-firing) conditions, and studies the effect of intake port configurations on the turbulence characteristics using following parameters ; Eulerian temporal autocorrelation coefficient, turbulence energy spectral density function, Taylor micro time scale, integral time scale, and integral length scale.

• 한국자동차공학회논문집
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• 제16권6호
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• pp.148-156
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• 2008

This paper is the first of 2 companion papers which investigate in-cylinder swirl generation characteristics according to inlet valve angle. Two DOHC 4 valve engines, one has wide intake valve angle and the other has narrow valve angle, were used to compare the characteristics of swirl motion generation in the cylinder. One intake port was deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake stroke. The results show that the stronger swirl motion is observed in wide valve angle engine at the early intake stage; however, the swirl motion is gradually distorted by the intake flow component passing through valve area near the cylinder wall as the stroke proceeds. The tumble motion also does so in wide angle. On the contrary, the swirl and tumble motions, which are not clear at the initial stage, become better and better arranged as the piston goes down and up again after bottom dead center.