• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.12
• /
• pp.1017-1026
• /
• 2014

A multi-perforated tube is generally installed between the muffler inlet and in front of selective catalytic reduction (SCR) catalysts in the integrated urea-SCR muffler system in order to disperse the urea-water solution spray uniformly and to make better use of the SCR catalyst, which would result in an increase nitrogen oxide ($NO_x$) reduction efficiency and a decrease in the ammonia slip. The effects of the multi-perforated tube orifice area ratios on the internal flow characteristics were investigated analytically by using a general-purpose commercial software package. From the results, it was clarified that the multi-perforated tube geometry sensitively affected the generation of the bulk swirling motion inside the plenum chamber set in front of the SCR catalyst and to the uniformity index of the velocity distribution produced at the inlet of the catalyst. To verify the analytical results, engine tests were carried out in the ESC and ETC modes. Results of these tests indicated that the larger flow model in the longitudinal direction showed the highest NOx reduction efficiency, which was a good agreement with the analytical results.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.949-951
• /
• 1992

A low pressure DC plasma jet has been used to obtain diamond films from a mixture of $CH_4$ and $H_2$ with high deposition rate (>1$\mu\textrm{m}$/min). The effects of the deposition conditions such as torch geometry, substrate temperature, gas mixing ratio, chamber pressure, axial magnetic field on the diamond film properties such as morphology, purity, uniformity of the film and deposition rate, etc. have been examined with the aid of Scanning Electron Microscopy, X-Ray Diffraction, and Raman Spectroscopy. Both the growth rate and particle size increased rapidly for low methane concentrations but saturated and the morphology changed from octahedral to cubic structure when the concentration exceeded 1.0 %. Higher growth rates (>1.5${\mu}m$/min) can be obtained by applying an axial magnetic field to the DC plasma jet. Diamond obtained from the magnetized plasma jet also shows a sharp peak at 1332.5$cm^{-1}$ in the Raman Spectra and this result implies that higher growth rate with a good quality diamond films can he obtained by applying an external magnetic field to the plasma jet.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.9
• /
• pp.2373-2385
• /
• 1995

The goals of this study are to apply exciplex method to the visualization of the fuel spray of a diesel engine and to investigate the liquid phase of fuel spray that injected at the various tips of a fuel injector. This study provides the informations for the improvement of the diesel injection system and the structures of diesel spry with the boiling of fuel droplets in combustion chamber by the exciplex method. Hexame was used as fuel for approximation to injection condition of the engine. And naphthalene and TMDP were added to the fuel for the visualization by exciplex method. Experimental injectors were 4hole, 8hole, and 1hole impinging injectors. In the injection condition of actual engine the exciplex was sufficient to catch the liquid phase signal. The spray penetration of impinging injector was small than that of actual 4 and 8hole injector but atomization was better. The upper bound of impinging injector was determined by the geometry of a cylinder head and the lower bound was determined by spray angle. On impinging injector the atomization was better at the edge of disk than at center of disk and also the mixing with environmental gas was better.

• 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.

• Journal of ILASS-Korea
• /
• v.16 no.4
• /
• pp.201-209
• /
• 2011

Optimum engine performance is obtained when the spray characteristics is well matched to the geometry of a combustion chamber. Among many parameters governing the combustion performance in internal combustion engine, fuel supply characteristics and atomization are important performance factors. Therefore, spray characteristics of high pressure multi-hole injector has been studied experimentally. An experimental test system has been made to operate high pressure injection system and to visualize spray behavior. Spray visualization has been performed to analyze spray formation, spray cone angle, bent angle and penetration length. Spray interaction with piston has been analyzed with various injector installation angle, injection pressure and ambient pressure. Test results show that penetration length is greatly influenced by the injection pressure. Penetration length is decreased as ambient pressure increased. Spray cone angle is increased as injection pressure and ambient pressure increased. However, bent angle is not influenced by the change of injection pressure and ambient pressure. Spray cone angle distribution map is plotted using the experimental data. Fuel movement around the spark-plug has been enforced as increasing injector installation angle.

• The KSFM Journal of Fluid Machinery
• /
• v.4 no.3 s.12
• /
• pp.53-61
• /
• 2001

Vortex type Fluidic Device(FD) which is installed at the bottom of Safety Injection Tank(SIT) controls the discharge flow rate from the tank. In case of loss of coolant accident the injection water flows into primary system in two steps; initial high flow rate for certain period of time and subsequent low flow rate. By two-step control of the discharge flow rate, FD can ensure the effective use of water in the tank. A small-scale FD has been tested to obtain a required flow characteristics maintaining full pressure and height of prototype, which are the major contributing parameters. Through the testing of many different arrangements of internal geometry of FD, most appropriate one was selected and its performance data was obtained. As characteristics of FD, time dependent Euler number, flow rate and pressure are presented and discussed. Also a method to predict the full size FD is presented.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.3 no.3
• /
• pp.53-61
• /
• 1999

Impinging jets are observed when exhaust gases from missiles or V/STOL aircrafts impinge on the ground, flame deflector, ship deck, etc. The flow shows different patterns according to the nozzle geometry, nozzle-to-plate distance, and plate angle, for example. This paper describes experimental works on the phenomena (pressure distribution, occurrence of stagnation bubble, and so on.) when underexpanded supersonic jets impinge on a perpendicular flat plate using a supersonic cold-flow system, and compares the results with those obtained using a shock tunnel. The flow characteristics for the supersonic cold-flow system were also investigated. Surface pressure distribution of supersonic cold-flow system differed from that of shock tunnel because of water and temperature in the low-pressure chamber. Surface pressure distribution as to underexpanded ratio showed similar patterns together.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.1752-1761
• /
• 2000

This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

• Journal of computational fluids engineering
• /
• v.20 no.4
• /
• pp.7-13
• /
• 2015

Vortex tube is a thermal static device that separates compressed air into hot and cold streams. In general, the cooling efficiency of vortex tubes is lower than that of traditional air conditioning equipment and vortex tubes are mainly used for industrial spot cooling applications because of their quick responses. In this study, conical frustums are employed in the nozzle chamber to improve the cooling performance. Conical frustums can be used to decrease the ineffective mass fraction that directly passes through the cold exit without energy separation. The shape optimization of conical frustums has been performed using full factorial design. It is found that the height of frustums has the largest main effects on the cooling performance. Computational results show that the cooling performance can be increased by about 10% within the considered range of the design parameters. This is because the ineffective mass fraction toward the cold exit is decreased by about 20%.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.6
• /
• pp.701-713
• /
• 2003

The BEM is a highly efficient method in the sense of economical computation. However, boundary integration is not easy for the complex geometry and moving surface, e.g. a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element according to their acoustic characteristics. In this study, an axial fan is assumed to have unsteady loading noise as a dominant source. Dipole sources can be modeled to solve the FW-H equation. Acoustic field is then computed by determining Kirchhoff surface on which near-field is implemented, to analyze the effect of Kirchhoff surface on it. The optimal shape and the location of Kirchhoff surface are discussed by comparing with experimental data acquired in an anechoic chamber.