• 대한조선학회논문집
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• 제49권6호
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• pp.512-520
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• 2012

In this study, the numerical analysis for the flows around an axial cylinder is carried out in order to investigate the basic characteristics of drag of blunt body. A variation of drag and flow separation for the axial cylinder is investigated according to the length-diameter ratio. Also, the flow separation around the head is removed by rounding-off the front edge of the body to analyze the effect of drag reduction. Most of the drag turns out to be a pressure drag component and the variation of drag is caused by the change of pressure and velocity which is affected strongly by the flow separation at the edges of the axial cylinder. Especially, it is found that the pressure drag component acting on the back of axial cylinder, as known as the base drag, mainly changes the drag. As the length-diameter ratio of axial cylinder increases, the drag sharply decreases and the minimum is shown when the length-diameter ratio is about 2.4. Also, as the length-diameter ratio increases further above 2.4, the drag increases at a slower rate. The pressure drag is almost constant when the length-diameter ratio is greater than 8, but the increase of friction drag component is the reason for the increase of the drag. When flow separation is removed completely at the front edge of the axial cylinder, the pressure drag component is reduced to 12~17%, but the total drag is reduced to only 17%~32% due to the friction drag component that increases linearly proportional to the length-diameter ratio.

• 한국수소및신에너지학회논문집
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• 제19권2호
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• pp.139-144
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• 2008

The focus of this research is that the scavenging aspect of in-cylinder is visualized by the PIV method and its characteristic is analyzed so that the scavenging performance of the free piston hydrogen fueled engine can improve with loop scavenging. As the results, the piston of convex type shows the best scavenging performance among the presented pistons. In case of the abnormal expansion, the scavenging of area between cylinder head and cylinder wall doesn't operate well.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.82-88
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• 1999

The object of this study is to find new evaluation index for in-cylinder flow chracteristics istead of current swirl, tumble coefficient using steady flow test rig on intake port system. To this end, port flow system. To this end, port flow rig test was conducted on DOHC head varying intake valve lift respectively. Finally combination angular coefficient and inclination angle were introduced as new evaluation index for in-cylinder angularflow characteristics instead of swirl and tumble coefficient.

• 한국자동차공학회논문집
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• 제5권5호
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• pp.188-196
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• 1997

Many researchers have developed the measurement technique of in-cylinder flow characteristics and found the effect of intake port geometries on engine performance. The flow characteristics of four-valve cylinder head were examined in a steady flow rig for different intake ports. Tumble intensity of intake configurations with different entry angles were quantified with a tumble meter. The velocity and angular momentum distributions in the tumble adaptor were measured under steady conditions with PIV(Particle Image Velocimetry). We have obtained the results that flow structure becomes complicated by valve interference at low valve lift. As the valve interferences were reducing and the flow pattern changed to large vortex structure with tumble direction, intake ports with different entry angles have different tumble centers. Tumble eccentricity of intake port with low entry angle was large, so that the port had relatively much angular momentum compared to others which was expected to improve combustion performance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.602-607
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• 2007

The heavy duty diesel engine must have a large output for maintaining excellent mobility. The compacted graphite iron (CGI) is a material currently under study for the engine demanded for high torque, durability, stiffness and fatigue. In this study, three dimensional finite element model of a heavy-duty diesel engine was developed to conduct the stress analysis by using property of CGI. The FE model of the heavy duty diesel engine section consisting with four half cylinder was selected. The heavy duty diesel engine section include cylinder block, cylinder head, liner, bearing cap, bearing and bolt. The loading conditions of engine are pre-fit load, assembly force and gas force.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.99-105
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• 2003

The configuration of intake port is a dominant factor of inlet air flow and mixture formation in an engine. In this study, as an available technology to optimum intake port, the flow box system using resine has been applied. So we presents a methodology for estimating inlet flow characteristics in this paper. This quantified experimental result shows good agreements with visualization data in a cylinder. We obtained the optimal value of swirl ratio and flow coefficient under steady flow rig test for new development of intake port for heavy-duty engine. From this results, the cylinder heat with a good evaluated swirl flow characteristics was developed and adapted for a 11L heavy-duty engine using the liquid phase LPG injection (LPLi) system. This .research expects to clarify major factor that make the intake port efficiently.

• 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.

• 한국자동차공학회논문집
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• 제2권3호
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• pp.1-12
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• 1994

A model engine having a flat cylinder head and a piston face and an off-center intake valve is investigated in this analysis. Calculation domain is confined to the half of the cylinder with swirl free inlet velocity condition. Due to the absence of measured inlet conditions, the inlet flowrates during induction period are calculated from overall mass and energy conservation requirements. Finite difference equation for velocity and pressure were solved by modified SIMPLER algorithm, standard k-$\varepsilon$turbulence model and hybrid scheme. From the result of prediction, dimensionless velocity distribution and turbulence intensities are investigated at each crank angle.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.22-30
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• 1996

In-cylinder flow of a purpose-built small HSDI Hydra Diesel engine was investigated by laser Doppler velocimetry(LDV) during induction and compression processes. The flow was quantified in terms of ensemble-averaged axial and swirl velocities, normalized by the mean piston speed, at a plane located 12mm from the cylinder head and corresponding to the mid-plane of the diametrically-opposed quartz windows at an enigne speed of 1000rpm. The formation of toroidal vortices during the intake process and the evolution and decay of swirl motion during the compression process were observed. Turbulence at around TDC of compression became homogeneous and isotropic.

• 대한기계학회논문집
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• 제12권6호
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• pp.1358-1371
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• 1988

The combustion process is the most important process in the S.I. engine since it determines performance and emissions. As the flame propagates slowly due to EGR or lean mixture, the fast burn system is widely used in the modern engines in order to improve engine performance. As the basic research for the fast burn system of the S.I engine, this study is aimed to identify the effects of the intake port design on the air motion inside a cylinder. In this study various intake ports were designed and tested. Swirl levels for the different intake ports were measured by a swirl meter and LDv.Also transient air motion inside a cylinder is further investigated following the motion of the boston. Out of the various intake ports tested in this study the masked shroud head (MSH) generates the highest swirl while keeping satisfactory volumetric efficiency. The MSH port also produces high level of turbulence by shearing action between cylinder wall and swirl.