• Journal of Mechanical Science and Technology
• /
• 제15권1호
• /
• pp.108-116
• /
• 2001

The in-cylinder flow field of gasoline engine comprises unsteady compressible turbulent flows caused by the intake port, combustion chamber geometry. Thus, the quantitative analysis of the in-cylinder flow characteristics plays an important role in the improvement of engine performances and the reduction of exhaust emission. In order to obtain the quantitative analysis of the in-cylinder gas flows for a gasoline engine, the single-frame particle tracking velocimetry was developed, which is designed to measure 2-dimensional gas flow field. In this paper, influences of the swirl and tumble intensifying valves on the in-cylinder flow characteristics under the various intake flow conditions were investigated by using this PTV method. Based on the results of experiment, the generation process of swirl and tumble flow in a cylinder during intake stroke was clarified. Its effect on the tumble ratio at the end of compression stroke was also investigated.

• 한국산업융합학회 논문집
• /
• 제2권2호
• /
• pp.155-163
• /
• 1999

In this study, single cylinder engines with different tumble ratio were made to find out in-cylinder fluid motion and flame propagation. Tumble ratio derived from the steady state flow rig test. Flame propagation speed was obtained using cylinder head gasket ionization probe and the piston ionization probe. And the combustion pressure in cylinder was measured to analyze the combustion characteristics. In case of high tumble engine, BSFC and BSHC were decreased and BSNOx was increased at part load test. Also BMEP and combustion peak pressure was increased at full load test. Tumble flow motion had an great effects on initial burning period rather than main burning period in part load test.

• 한국자동차공학회논문집
• /
• 제14권6호
• /
• pp.184-189
• /
• 2006

Tumble flow test rig has been used as the useful tool in the developing intake system because major flow pattern induced by intake port of DOHC engine is tumble. Angular momentum of in-cylinder tumble flow can not be directly measured by impulse torque meter in the test rig like that of in-cylinder swirl flow due to rotational axis of the flow. Therefore the adaptor to transform tumble to swirl flow must be adapted in the test rig. In this study, using the commercial CFD code STAR-CD, we studied the effects on measured results due to the variation of the major design variables in the adaptor, tube length(L), tube diameter(D) and cylinder height(H). The effect of the attached angle($\theta$) of the test head to the adaptor also was simulated.

• 대한기계학회논문집B
• /
• 제21권5호
• /
• pp.650-658
• /
• 1997

Analysis and control of intake charge motion such as swirl and tumble are very important factors in improving the gasoline engine performance. In this paper, single-frame PTV (particle tracking velocimetry) is used to investigate intake tumble patterns in a steady flow test rig of gasoline engine with dual-intake-valve and pent-roof combustion chamber. Intake tumble pattern is quantified in accordance with blockage ratio of TIV (tumble intensifying valve) with single- frame PTv.The view of the instantaneous 2-D velocity field gives a realistic understanding of in-cylinder flow field. Thus it is confirmed that PTV is a effective tool in engine design. In conventional port, two tumble structures appear clearly, and the larger one is observed under the exhaust valve side and the smaller is right below the intake valve side. The larger vorticity is observed in TIV port, thus it is concluded that TIV have an effect on intensified tumble motion in cylinder flow.

• 아동학회지
• /
• 제19권1호
• /
• pp.131-140
• /
• 1998

The purpose of this study was to describe relations between the rough-and-tumble play of preschoolers and their social competence. The subjects were 61 4-year-olds and 59 5-year-olds. Children were observed on a day care center playground during free play time. Teachers were asked to rate the children's social competence. The results indicated that the incidence of rough-and-tumble play varied according to the sex of the child and the physical environment of the playground. Children's rough-and-tumble play was negatively correlated with measures of social competence.

• International Journal of Automotive Technology
• /
• 제7권4호
• /
• pp.415-422
• /
• 2006

Swirl and tumble flows in an engine in-cylinder have been simulated by using a three-dimensional computational fluid dynamics code, and the results are validated in comparison with experimental data. The large eddy simulation based on the Smagorinsky model and the fractional step method is adopted to describe the turbulence of in-cylinder flows and to save computing time, respectively. The main purpose of this study is connected with the effect of various conditions of intake flows on formation and development of in-cylinder tumble and swirl motions. The engine speeds considered are 1000 rpm and 3000 rpm for intake flows with inclination angles between $-10^{\circ}$ and $20^{\circ}$ at deflection angles of $0^{\circ}$, $22.5^{\circ}$, and $30^{\circ}$. The results are discussed by visualizing flow fields and by evaluating parameters in relation to vortex intensity such as swirl and tumble ratios.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집D
• /
• pp.933-938
• /
• 2001

A 5-valve(intake 3-valve) engine has been developed to increase engine performance. These vehicles have a high power caused by the decrease of inertia mass of an intake valve and the increase of intake effective area. In this study, velocity profiles at near intake valves were inspected by using a two-color PIV and laser sheet method with tumble control valve(TCV). In addition, steady flow tests were performed to quantify tumble ratio on flow-fields generated with a TCV. These experimental results show that the tendency of the tunble ratio in intake 3-valve engine is different from the one in intake 2-valve engine. From this results, the intake flow characteristics around intake valves were made clear.

• 한국자동차공학회논문집
• /
• 제11권6호
• /
• pp.7-13
• /
• 2003

The purpose of this study is to investigate the effect of the in-cylinder flows and different injection timings on fuel behavior in the cylinder of a GDI engine. Three different flows types induced by using masked port, unmasked port, and port deactivation were tumble, swirl&tumble, and high swirl respectively. LIEF technique was applied to investigate the mixture formation and fuel distribution at ignition time in the transparent engine with optical access through the piston top and upper part of cylinder liner. Injection timings of 180,90, and 60 degrees before TDC were examined. It was found that tumble flow was more effective on the homogeneous mixture formation than other flow and swirl flow transported more fuel vapor to the exhaust side at early injection mode, and swirl and swirl & tumble flow made fuel vapor concentrate around the cylinder center at late injection mode.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.2233-2238
• /
• 2003

It is well known that organized vortex rotations swirl and tumble greatly affect the mixing, the combustion and heat transfer processes in engine cylinder. We have developed 3 dimensional numerical simulation codes whose predictions make good agreement with the experimental data. Large eddy simulation based on Smagorinsky subgrid scale model was adopted to describe the turbulence of in-cylinder flows. The tumble motions generated by different inclination angles between valve-port and cylinder head have been calculated. The results show that the angles between direction of induced flow and cylinder walls which the flow collides with play a great role in the formation and generation of tumble motions. Therefore, it is inferred that seat angle and inclination angle are important factors of engine design. In addition, the numerical results of different engine speed -1000 rpm and 3000 rpm are very similar in the flow structure.

• 아동학회지
• /
• 제31권4호
• /
• pp.75-90
• /
• 2010

This study sought to investigate the aspects and other factors at work in rough and tumble play by children, through a qualitative research approach. The participants consisted of 25 5-year-old children and their teachers at A kindergarten, located in Seoul. The results of the research are as follow：(1) there are various aspects in the initiation of, development of, as well as the way children's rough and tumble play ends. (2) The factors that trigger children's rough and tumble play include : limitation and creation of toys, teacher absence, particular times throughout the day, gender awareness, peer relationships, the reactions of teachers, and social and cultural factors at work in class.