• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.94-97
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• 2003

The effect of pressure perturbation in the ramjet engine on the characteristics of the inlet is studied via numerical simulation. The frequency and amplitude of the pressure perturbation are assumed to be 500Hz and 20% of the exit back pressure, respectively. The simulation shows the characteristics of the normal shock in the inlet according to the pressure perturbations. The relation between the captured mass flow rate and downstream pressure perturbation is studied. The mass flow rate decreases when the downstream pressure perturbation starts.

• Journal of ILASS-Korea
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• v.9 no.4
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• pp.83-89
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• 2004

Vaporization characteristics of a liquid heptane droplet in high-pressure and temperature flow field are numerically studied. Variable thermodynamic and transport properties and high-pressure effects are taken into account in order to consider real gas effects. Droplet Vaporization in convective environments was investigated on the basis of droplet vaporization in quiescent and convective environment. In quiescent environments, droplet lifetime is directly proportional to pressure at the subcritical temperature range but it is inversely proportional to pressure at the supercritical temperature range. In convective environment, droplet deformation becomes stronger by increasing Reynolds number due to increase of velocity while droplet deformation is relatively weak at a higher pressure for the same Reynolds number cases.

• Journal of KSNVE
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• v.9 no.2
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• pp.285-294
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• 1999

Transient analysis for compressible fluid flow has been performed experimentally and analytically to study the dynamic characteristics of the end volume transmission lines following a sudden pressure change a its entrance. The numerical method was developed based on the method of characteristics. The sudden pressure at its entrance was generated by rupture of diaphragm in a shock tube. The sudden pressure was used to obtain the response, as input signal for the numerical analysis. The response to the sudden pressure at the end volume was measured using a pressure transducer. The experimental result shows good agreements with the numerical result. The effects of tube length, its diameter and end volume magnitude are evaluated on the responses of the pressure and on the damping factor. It is found that the viscous damping effects on the response through the transmission pipeline becomes larger with increasing pi;eline length and decreasing diameter of the pipe and the fluid-elastic stiffness decreases with increasing the terminal volume. The numerical approach presented in this paper can be very useful in designing the instrument and control system.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.51-57
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• 2014

High pressure common rail injection technology has revolutionized the diesel industry. Over the last decade it has allowed engine builders to run higher injection pressures as much as above 1,300bar in order to increase engine efficiency, while reducing emissions. This common rail system has low pressure circuit which is consist of low pressure pump, cascade overflow valve and flow metering unit. The low pressure pump's purpose is to feed fuel oil to the high pressure pump. The cascade overflow valve keeps pressure in front of the metering unit constant and provides lubrication for the high pressure pump. The metering unit, known as the MPROP or fuel pressure regulator, regulates the maximum flow rate delivers to the rail. In this paper, we have investigated the performance characteristics of each components and total low pressure circuit of common rail system.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.47-53
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• 2006

The purpose of this study was to investigate the significant characteristics in spray of industrial etch-nozzle for the design of process. The experiment was carried out with different spray pressure and industrial nozzle in wet etch. The characteristics of liquid spray, such as axial velocity and sauter mean diameter measurements were obtained by PDA. And impact force was calculated from spray characteristics. It was found that the fluid with higher spray pressure resulted in the smaller SMD and the higher droplet velocity and impact force. The depth of etch was increased in case of high spray pressure. In the case of injection angle oscillated between $20^{\circ}$, the result indicated constant effect of etch. The correlation between the spray characteristics and etch ones were analyzed. The depth of etch had good positive correlation with axial velocity and impact force. The result clearly shows that the characteristics in wet etch are strongly related to the spray characteristics with process.

• Journal of Korean Association for Spatial Structures
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• v.13 no.2
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• pp.67-73
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• 2013

This paper attempted to bridge this gap by identifying the number of flat-plate solar collectors. The characteristics of wind pressure coefficients acting on flat-plate solar collectors which are most widely used were investigated for various wind direction. Findings from this study found that the location where the maximum wind pressure coefficient occurred in the solar collector was the edge of the collector. Regarding the characteristics according to the number of collectors, the paper found that downward wind pressure coefficient of the lower edge of the collector was higher than the upward wind pressure coefficient of the upper edge of the collector in the basic module (1 piece). However, as the number of collectors increases, the upward wind pressure coefficient of the upper edge become higher than the downward wind pressure coefficient of the lower edge. Finally yet important, it was found that the location of the maximum wind pressure coefficient was changed according to the number of solar collectors.

• Wind and Structures
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• v.4 no.1
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• pp.73-84
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• 2001

Analysis of pressures measured on the roof of the full-scale Texas Tech building and a 1/50 scale model of a typical house showed that the pressure fluctuations on cladding fastener and cladding-truss connection tributary areas have similar characteristics. The probability density functions of pressure fluctuations on these areas are negatively skewed from Gaussian, with pressure peak factors less than -5.5. The fluctuating pressure energy is mostly contained at full-scale frequencies of up to about 0.6 Hz. Pressure coefficients, $C_p$ and local pressure factors, $K_l$ given in the Australian wind load standard AS1170.2 are generally satisfactory, except for some small cladding fastener tributary areas near the edges.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.75-82
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• 2004

In this research, a computer analysis has been developed for predicting the Pipe pressure of the intake and exhaust manifold in a small single cylinder engine. To get the boundary conditions for a numerical analysis one dimensional and unsteady gas dynamic calculation is performed by using the MOC(Method Of Characteristics). The main numerical parameters are engine revolutions. to calculate the Pulsating flow which the intake and exhaust valves are working. The distributions of the exhaust pipe pressures were influenced strongly to the cylinder pressures and the shapes of exhaust pressure variation were similar to the Inside of cylinder pressure As the engine revolutions are increased. the intake pressure was lower than ambient pressure. The amplitude of exhaust pressure had increased and the phase of cylinder pressure $P_c$ is delayed and the amplitude of cylinder pressure were increased.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.1
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• pp.35-42
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• 1985

This paper describes an experimental study of the effect of injection timing on the combustion characteristics in four stroke cycle diesel engine with direct injection type combustion chamber. The effect of injection timing and compression ratio of engine on the combustion characteristics are investigated. Experimental results of combustion characteristics in cylinder show that the combustion pressure and the rate of pressure rise decrease in accordance with the retard of fuel injection timing. It is observed that the rate of pressure rise in cylinder is increased an increase in the compression ratio of engine. The effect of the fuel injection timing on the frequency of cylinder pressure brings about the same trend of the maximum rate of pressure rise in cylinder.

• Journal of Drive and Control
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• v.13 no.4
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• pp.7-13
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• 2016

This paper presents the meter-out and meter-in speed control characteristics of a pneumatic cylinder with relief valve type cushion device. The piston displacement and velocity are measured to investigate high speed driving performance with variation of the pressure setting in relief valve, air supply pressure, load mass, the supply and exhaust flow rate from the cylinder. Also, the internal pressures and temperatures driving pressure and cushion chamber are measured. The piston displacements and velocities of meter-out and meter-in control are compared experimentally determined data. A comparison experimental data meter-out and meter-in control show that a relief valve type cushion device is suitable for high speed pneumatic cylinders. The desired response characteristics of piston displacement and velocity are satisfactory adjust the pressure setting of a relief valve with varying system parameters such as air supply pressure, load mass and controlled flow rate.