• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.9
• /
• pp.1178-1184
• /
• 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.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.1
• /
• pp.59-72
• /
• 1998

This experimental study was carried out to investigate the characteristics of the in-cylinder eccentricity swirl flow generated by a 4 valve cylinder head with a tangential and a helical intake port. the measurements of the in-cylinder velocity field have been made by a two-channel LDA system. The mean flow coefficient(Cf(meam)), swirl ratio(Rs) and mass flowrate with valve eccentricity ratios and an intake port partition between the two intake ports were measured in the steady flow test fig using the ISM(impulse swirl meter). The experimental results indicated that the mass flowrate through the tangential intake port was 19% and 7.7% more than that of the helical intake port in case of with and without intake port partition respectively. There was a tendency to be a single rotation flow in swirl flow fields formed by a 4 valve cylinder head because of the interaction between the two intake ports. As the intake port partition was not set between flow coefficient(Cf(mean)) was 7.35%.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.12 no.1
• /
• pp.501-517
• /
• 2020

Three-dimensional numerical simulations were performed to study the effects of flow direction and flow velocity on the flow regime behind a curved pipe represented by a curved circular cylinder. The cylinder is based on a previous study and consists of a quarter segment of a ring and a horizontal part at the end of the ring. The cylinder was rotated in the computational domain to examine five incident flow angles of 0-180° with 45° intervals at Reynolds numbers of 100 and 500. The detailed wake topologies represented by λ2 criterion were captured using a Large Eddy Simulation (LES). The curved cylinder leads to different flow regimes along the span, which shows the three-dimensionality of the wake field. At a Reynolds number of 100, the shedding was suppressed after flow angle of 135°, and oblique flow was observed at 90°. At a Reynolds number of 500, vortex dislocation was detected at 90° and 135°. These observations are in good agreement with the three-dimensionality of the wake field that arose due to the curved shape.

• 연구논문집
• /
• s.23
• /
• pp.121-126
• /
• 1993

In general, natural gas engine converted from gasoline engine has disadvantage of power decrease. In order to increase power output in natural gas engine, the improvement of in-cylinder flow motion has been believed as the most effective method. In this study, the geometry of combustion chamber in 4 valve DOHC natural gas engine is modified, and in-cylinder flow patterns are analyized. Also engine performance is evaluated according to the modification of in-cylinder flow motion.

• 한국가시화정보학회:학술대회논문집
• /
• 2003.11a
• /
• pp.31-34
• /
• 2003

The near wake behind a sinusoidal cylinder has been investigated quantitatively using hot-wire anemometer and qualitative. The mean velocity and turbulence intensity were measured in streamwise and spanwise direction. The results show that the wake in the saddle plane has a longer vortex formation region and rapid reversed flow than that in nodal plane. The elongated vortex formation region of sinusoidal cylinder is related with drag reduction. In addition, the flow visualized with particle tracing method support the flow characteristics of sinusoidal cylinder measured by hot-wire.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.3
• /
• pp.92-101
• /
• 1996

In a gasoline engine, the characteristics of air flow is very important not only for the design of the intake system geometry bout also for the accurate measurement of the induction air mass. In this study, an air flow rate measurement of the induction air mass. In this study, an air flow rate measurement was conducted by using the hot wire flow meter at the upstream of the intake port and the throttle. At the upstream of the throttle, the overshoot phenomena of the air flow rate by fast throttle opening were analyzed with choked flow. At the upstream of the intake port, the cylinder variation of the air flow rate and the difference between fast throttle opening and closing were showed during the unsteady state by the throttle step change. The results of this study can be used for the design of the throttle valve geometry and cylinder by cylinder control.

• Journal of Ocean Engineering and Technology
• /
• v.24 no.5
• /
• pp.8-15
• /
• 2010

The flow around a two-dimensional, rectangular cylinder that is freely falling in a channel was simulated using the immersed boundary method with direct forcing to determine the interactions between the fluid and the structure. The results of the present study were in good agreement with previous experimental results. Regardless of the H/L ratio (where H and L are the height and width of the rectangular cylinder, respectively), the flow structures had essentially the same pattern as the two symmetrical circulations that form about the horizontal center of the cylinder, with those centers located at each lateral position near the wake. When the cylinder approaches very close to the bottom, a jet-like flow appeared between the bottom of the rectangular cylinder and the channel. When the jet-like flow goes through the channel, surrounding fluids are sucked into this jet, forming the secondary vortices.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.1
• /
• pp.99-105
• /
• 2007

It is very important to clarify the 3-D angular flow characteristics of in-cylinder bulk motion in the developing process of variable induction system. In-cylinder flow induced by variable induction system is very complex, so we can not describe the in-cylinder bulk flow characteristics using the conventional swirl or tumble coefficient. In this study, we introduced the new 3-D angular flow index, angular flow coefficient($N_B$), for in-cylinder bulk flow characteristics. And also, 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.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.148-153
• /
• 2001

A computational investigation of the effect of the electromagnetic force(or Lorentz force) on the flow behavior around a circular cylinder, a typical model of bluff bodies, is conducted. Two-dimensional unsteady flow computation for $Re=10^2$ is carried out using a numerical method of finite difference approximation in a curvilinear body-fitted coordinate system by solving the momentum equations including the Lorentz force as a body force. The effect of the spatial variations of the Lorentz forcing region and forcing direction along the cylinder circumference is investigated. The numerical results show that the Lorentz force can effectively suppress the flow separation and oscillation of the lift force of the circular cylinder cross-flow, leading to the reduction of the drag.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.12
• /
• pp.1095-1102
• /
• 2003

Flow characteristics of turbulent steady fluid flow past a cylinder in rectangular duct are measured by 5 W laser doppler velocity meter. The fluid flow is also computed by commercial software of STAR-CD for comparison between the measurement and computation. The turbulent models applied in the computations are standard K-epsilon model, RNG K-epsilon model and Chen K-epsilon model. Acurracy of standard K-epsilon model is a little bit better than acurracies of other models even though those models have almost the same order of error compared to measured data. The computations predict satisfactorily the measured velocity profiles at middle section of the circular cylinder before the fluid flow diverges. However, there are some disagreements between them at down stream from the circular cylinder.