• 한국공작기계학회논문집
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• 제16권4호
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• pp.13-21
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• 2007

This paper presents characteristics of steady flow by variation of a combustion chamber and an intake port. Gas flow field inside a combustion chamber is the important factor in improving combustion stability and reduction of emission level. The flow characteristics such as flow coefficient, tumble ratio and swirl ratio are measured by the steady flow rig test with an impulse meter in this study. In the measuring, the valve lifts are varied between 1mm to 10mm. The three combustion chambers and two intake ports were applied to the steady flow apparatus in order to investigate the effect of swirl and tumble on the in-cylinder flow. As a result, tumble ratio were found to be different by variation of the combustion chambers and the intake ports. The data from the present study can be applied to design of a similar engine as basic data.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.17-23
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• 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.

• 연구논문집
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• 통권23호
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• pp.63-71
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• 1993

To improve flow in-cylinder flow in a 2-valve gasoline engine, various geometries of combustion chambers are modified. Air flow rate, swirl and tumble flow are measured and analyzed by swirl impulse meter and LDV in a steady state flow measuring rig. The results of LDV experiment are compared with the data of swirl impulse meter.

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

• 한국연소학회:학술대회논문집
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• 한국연소학회 1997년도 제15회 KOSCO SYMPOSIUM 논문집
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• pp.153-162
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• 1997

The effects of tumble and swirl flows on the flame propagation were investigated experimentally in a 4-valve optical gasoline engine. The tumble flow patterns, generated by various intake ports of different entry angle; $25^{\circ}$ , $20^{\circ}$ and $15^{\circ}$ , were characterized under motored conditions with laser Doppler velocirnetry. Inclined tumble(swirl) flows were induced by three different swirl control valves. The initial flame propagation was visualized by an ICCD camera and its image were analyzed to compare the enflamed area and displacement of initial flames. It was found that there is a correlation between the stronger tumble during induction and turbulence levels at the time of ignition resulting in faster flame development. Inclined tumble was proved to be more beneficial than the pure tumble for faster and stable combustion under lean mixture conditions, which was confirmed by faster propagating flame images.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.87-95
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• 1995

A commercial DOHC four valve engine was modified to make a single-cylinder optical model engine with replaceable head. Three kinds of head were used to generate swirl, tumble, and combined swirl/tumble motion. Schlieren visualization technique was applied to characterize the in-cylinder flow qualitatively. Particle Image velocimetry has been developed and applied for the quantitative flow measurements. Axial and tangential flow motion inside the cylinder has been characterized. The swirl/tumble port shows beneficial results in terms of turbulence generation for the initial flame propagation and mean swirl motion for the overall flame propagation.

• 대한기계학회논문집B
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• 제23권9호
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• pp.1178-1184
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• 1999

The in-cylinder flow field of gasoline engine comprises unsteady compressible turbulent flows caused by the intake port, combustion chamber geometry and the change of the spatial shape. Thus the quantitative analysis of the in-cylinder bulk flow plays an important role in the improvement of engine performances and the reduction of exhaust emission. The influences of tumble intensifying valve (TIV) and swirl intensifying valve (SIV), and various intake-flow conditions are compared with the tumble ratio obtained by the measured results of the in-cylinder gas flow. In order to obtain the quantitative analysis of the in-cylinder gas flows of gasoline engine this investigation applied the particle tracking method to the analysis of gas flow characteristics. Various intake conditions such as tumble and swirl intensifying valve, the deactivated condition of one valve among two intake valves, and the other factors of gas flow are considered.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3038-3043
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• 2008

Tumble or swirl flow is used adequately to promote mixing of air and fuel in the cylinder and to enlarge turbulent intensity in the late time of compression stroke. However, since in-cylinder flow is a kind of transient state with rapid flow variation, that is, non-steady state flow, swirl or tumble flow has not been analyzed sufficiently and not been recognized whether they are available for combustion theoretically yet. In the investigation of intake turbulent characteristics using PIV method, different flow characteristics were showed according to SCV figures. SCV installed engine had higher vorticity, turbulent strength by fluctuation and turbulent kinetic energy than a baseline engine, especially around the wall and lower part of the cylinder. Consequently, as swirl flow was added to existing tumble flow, it was found that fluctuation component increased and flow energy was conserved effectively through the experiment.

• 한국공작기계학회논문집
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• 제17권4호
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• pp.81-88
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• 2008

Flow characteristics have one of the effects in the process of engine. The numerical analysis makes it possible to predict the flow fields. This paper presents characteristics of steady flow according to variation of valve lift in a gasoline engine. The numerical computations have been made to observe the pressure distribution in accordance with the variable valve lift. Characteristics of tumble flow and swirl flow according to the variable valve has also been investigated. We could find that tumble ratio and swirl ratio is different between with/without PDA valve. The steady flow test was simulated through three-dimensional analysis on intake port design for comparing with experimental data and confirming the feasibility of applying analytic method. As a result, this study shows the possibility of the usage of numerical simulation to predict the flow characteristics for gasoline engine.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.66-75
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• 1999

Many researchers have developed the measurement technique of in-cylinder flow. Recently, there are lots of studies on steady flow with different SCV geometries. In this study the flow characteristics of four-valve cylinder head were examined in a steady test rig for different SCV open ratios. Each swirl ratio of several SCV angle was quantified by swirl impulse meter and 2D-LDV measurement. The results showed that the swirl ratio was controlled between 2.3 and 3.8 based on SCV angles. The velocity distributions of in-cylinder flow field were measured by 2-D LDV test and visualized swirl and tumble flow pattern at different positions. In this engine , we found out that the swirl was dominant flow.