• Journal of ILASS-Korea
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• v.4 no.2
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• pp.33-39
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• 1999

This paper presents the spray atomization characteristics of the high-pressure gasoline injector for the direct-injection gasoline engine. The gasoline sprays of the injector were minted into a pressurized spray chamber with a optical access at various ambient pressures. The atomization characteristics of fuel spray such as mean diameter, mean velocity of droplet were measured by the phase Doppler particle analyzer system. In order to investigate the effect of fuel injection pressure on the quantitative characteristics of spray, the global visualization and experiment of particle measurement in the fuel spray were investigated at 3, 5 and 7 MPa of injection pressure under different ambient pressure in the spray chamber. Based on the results of this work, the fuel injection pressure of fuel injector in gasoline direct-injection engine have influence upon distribution of the mean velocity and droplet size of fuel spray. Also, the influence of injection pressure on the velocity distribution at various measuring location were investigated.

• The KSFM Journal of Fluid Machinery
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• v.16 no.1
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• pp.32-39
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• 2013

The multi-stage control valve is one of the devices which controls cavitation and high pressure drop. To attain the high pressure drop, the conventional control valves adopted the multi-stage trim to avoid the occurrence of local cavitation in valves. This work studied the effect of divergence angle on the characteristics of multi-stage trim. Pressure drop and flow characteristics was calculated for the 1 passage of multi-staged trim by using the FLUENT 6.3.26. The result showed that the pressure drop is significantly influenced by the divergence angle of multi-stage trim. In addition, the pressure drop increased consistently as the Reynolds number and divergence angle increases.

• 한국연소학회:학술대회논문집
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• 2000.12a
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• pp.194-201
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• 2000

This paper is intended to analyze the macroscopic behavior and transient atomization characteristics of the high-pressure gasoline injector in direct-injection gasoline engine. The global spray behavior of fuel injector was visualized by shadowgraph technique. Time-resolved droplet axial and radial velocity components and droplet diameter were measured at many probe positions in both axial and radial directions by a two-component phase Doppler particle analyzer (PDPA). In order to obtain the influence of fuel injection pressure, the macroscopic visualization and experiment of particle measurement on the fuel spray were investigated at 3,5 and 7 MPa of injection pressure under different surrounding pressure in the spray chamber. The results of this work show that the fuel injection pressure of gasoline injector in GDI engine has influence upon the mean droplet diameter, mean velocity of spray droplet, the spray tip penetration, and spray width under the elevated ambient pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.77-82
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• 2003

A parametric study was conducted on pressure drop in a catalytic converter for automobile. In this work, we proposed a new pressure drop relation which contains the various parameters needed to calculate and got a few results. In a monolith of catalyst, the flow originally turbulent flow changes to laminar flow and thus the pressure drop through the monolith is linearly proportional to the velocity. The exhaust pressure is doubly affected by the increase of mean velocity and length when we decrease the diameter of monolith while the volume keeps constant. Theoretical parameters such as $\alpha$ and $\beta$ are suggested to use as a reference value when there is no a experimental data. Especially in the part load test, these values should be modified to consider the property change of exhaust gas.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.497-501
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• 2000

One of the way to derive design parameters of the fuel feeding system in satellite is to analyze unsteady flow of liquid propellant (hydrazine) in the propulsion system. During steady thruster firing the flow rate is constant: if a thruster valve is abruptly shut down among a sets of thrusters, pressure spikes much higher than the initial tank pressure occur. This renders the fuel flow unsteady, and the fluid pressure and flow rate to oscillate. If the pressure spikes are high enough, there are possibilities that propellant explosively decomposes, thruster valves are damaged, and adiabatic detonation of the hydrazine propellant is potentially incurred. Reflected shockwaves could also affect the calibration and operation of the pressure transducers. These necessitate the analysis of unsteady flow in the propulsion system design, and the calculation results obtained through some governing parameter variation are presented in this work.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1156-1161
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• 2001

A significant trial has been performed for estimation of noise level of a cross flow fan for air conditioning system. In general, measurements of noise level of machinery require rigorous equipment involving an anechoic chamber with precision gauges. The apparatus is expensive to utilize and is not easy to construct. In this work, we adopt static pressure sensing from an ordinary pressure transducer for prediction of noise level of a rotating fan. The present procedure is finding sound pressure from the static pressure by manipulating Light-Curle equation depicts noisy energy in terms of pressure on surfaces of noise generators. Sound power level near core unit of the fan is evaluated with the present methodology in a normal laboratory room without any sound absorbers. The method is easy and shows good prediction results compared with precise measurements by using microphones.

• Journal of the Korean Society of Combustion
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• v.8 no.3
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• pp.31-37
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• 2003

The objective of this work is to investigate the effect of swirl, injection pressure and pilot injection on D.I.Diesel combustion by using a transparent engine system. The test engine is equipped with common rail injection system to obtain high pressure and to control injection timing and duration. In this study, the combustion analysis and steady flow test were conducted to estimate the heat release rate from in-cylinder pressure and pilot injection was investigated by using LII technique. As the results, high injection pressure was found to shorten ignition delay as well as enhance peak pressure and heat release rate was greatly affected by injection timing and pilot injection. In addition, the results showed that the period of soot formation corresponded to the diffusion flame.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.95-101
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• 2001

This work is concerned with construction of the intelligence stress predictor far compression strength evaluation using neural network-ultrasonic waves. The contact pressure in jointed plates was measured by using ultrasonic technique. Neural network is used to evaluate and predict contact pressure from the results of the calibration curves. The organized neural system was leaned with the accuracy of 99%, as a result of learning the ultrasonic echo ratio to the contact pressure measurement between SM45C and STS410 materials. And it could be evaluated and predicted with the accuracy of 90% in the evaluation of ultrasonic echo ratio difference in the same surface roughness and contact pressure, and 85% in the prediction of virtual ultrasonic echo ratio. Thus the proposed stress predictor is very useful for the evaluation and prediction of the contact pressure between SM45C and STS410 materials.

• Journal of the Korean Society of Combustion
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• v.19 no.1
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• pp.11-16
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• 2014

Spherically expanding flames are used to measure flame speeds, which are derived the corresponding laminar flame speeds at zero stretch. Dimethyl Ether-Air mixtures at high pressure are studied over an extensive range of equivalence ratios. The classical shadowgraph technique is used to detect the reaction zone. In analytical methodology the optimization process using least mean squares is performed to extract the laminar flame speeds. It is seen that the laminar flame speed of DME-Air mixture with the increase of pressure decreases rapidly showing a similar trend to other hydrocarbon fuels. At pressure of 2 and 10 atm the experimental data from the present study agree well with results reported in the literature. Especially the laminar flame speeds at 2 atm are in good agreement with those calculated in numerical work over the full stoichiometric range. At elevated pressure of 12 atm the measured data are slightly slower at fuel lean condition and show close agreement at fuel rich condition when compared with the numerical results.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.110-116
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• 1994

In this research, the tensile strength of molded parts and pressure distribution were analyzed to study the cavity filling stage and packing stage in injection molding. The measurement of cavity pressure was obtained by a data acquisition system with the installation of transducers in the cavity. Molded parts were tested by a universal testing machine to obtain the tensile strength. For the experimental work, the tensile strength of molded parts increased with longer packing time and exact freezing time of the gate was obtained by a cavity pressure curve. In addition, the effect of packing did not occur and tensile strength was almost constant after early 1.5 sec of the freezing time of gate. Density tended to be higher about 0.2% due to a larger degree of mold temperature and melt temperature. Also, changing pressure in the cavity was effectively sensed. Thereafter, the possibility of the development of pattern recognition expert system was confirmed on the basis of the experimental results.