• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.320-329
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• 1999

An experimental study has been performed to investigate the heat transfer characteristics of impinging jets with corrugated nozzle and wake generation plate. Three different shapes of corrugated nozzle and five different shapes of wake generation plate were tested to improve the heat transfer characteristics of impinging jet. Heat transfer coefficients were obtained by using transient method based on the liquid crystal thermography. The effects of corrugated nozzle and wake generation plate on the heat transfer characteristics of impinging jets were discussed in detail. The results showed that both the corrugated nozzle and the wake generation plate improved the heat transfer characteristics of impinging jet. Especially, heat transfer coefficients around stagnation region of impinging jets were highly increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.55-65
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• 1999

An experimenta investigation of unsteady impinging DI diesel spray on the unheated plate and heated plate has been conducted in a pressurized chamber using high speed shadowgraphy. The ambient agas pressure was varied using nitrogen with chamber pressure of 1.1MPa, 2.1MPa and 2.6MPa. As the increase of ambient gas pressure of ambient gas pressure, the height of spray is increased if entrainment and circulation . At higher temperature of impinging plate, the radial penetration of the impinging spary is incresed , but the height of impinging spray is decreased.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.2
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• pp.83-89
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• 1996

The objective of this study is to find experimentally the characteristics of the noise generated by the impinging jet on the normal plate, and also to compare the noise characteristics of the impinging jet with those of the free jet. The experiment is performed for the measurement of the noise specturm, the noise power, and the directivity for the free and impinging jets. From the experiment. it is found that the power of noises generated by the free jet as well as the impinging jet is proportional to the eighth power of the jet velocity through the circular converging nozzle, and that the noise power of the impinging jet is 15dB as high as one of the free jet when the plate distance is about within one to three times the nozzle diameter at the pressure ratio 1.39. The sound pressure level of the impinging jet depends upon the jet pressure and the plate distance. The plate distance with the maximum overall sound pressure level is increased with the jet pressure. The directivities with 1/3 octave band frequency for both the free jet and the impinging jet are greatly influenced by the convection effect.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.442-447
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• 2003

The characteristics of instantaneous wall-surface temperature of impinging plate in case of ultra high pressure injection have been measured and analyzed by using thin film instantaneous temperature probe and ultra high pressure injection equipment. The decreasing rate of temperature was greater in case of higher temperature of impinging plate. Temperature drop was largest at center of piston and it was slight for others. Instantaneous temperature decreases rapidly with increasing injection pressure. But above 2,500bar of injection pressure, the decreasing rates are slightly affected by increasing injection pressure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.402-408
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• 2005

The instantaneous temperature behaviors on impinging plate in case of ultra high pressure have been measured and analyzed by using the instantaneous temperature probe and ultra high pressure injection equipment. The temperature drop was largest at P1 which is center of impinging spray and decreased with propagation of spray to the radius direction. The temperature drop was bigger in case of higher temperature of impinging plate. The temperature drop decreased with increase of injection pressure. But decreasing rate of temperature drop was slight over 2,500 bars. Therefore, it was predicted that the fuel evaporation versus the increase of injection pressure was maximum at around 2,500 bars.

• 한국전산유체공학회:학술대회논문집
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• 2001.05a
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• pp.134-143
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• 2001

Viscous solutions of supersonic jet impinging on a flat plate normal to the flow are simulated using three-dimensional Navier-Stokes solver. The jet impinging flow structure exhibits such complex nature as shock shell, plate shock and Mach disk depending on the flow parameters. Among others, the dominant parameters are the ratio of the nozzle exit pressure to the ambient pressure and the distance between the nozzle exit plane and the impinging plane. In the present study, the nozzle contour and the pressure ratio are held fixed, while the jet impinging distance is varied to illuminate the characteristics of the jet plume with the distance. As the plate is placed close to the nozzle at 3D high, the computed wall pressure at or near the jet center oscillates with large amplitude with respect to the mean value. Here D is the nozzle exit diameter. The amplitude of wall pressure fluctuations subsides as the distance increases, but the maximum pressure level at the plate is achieved when the distance is about 4D high. The frequency of the wall pressure is estimated at 6.0 kHz, 9.3 kHz, and 10.0 kHz as the impinging distance varies from 3D, 4D, to 6D, respectively.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1631-1636
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• 2004

The supersonic impinging jet has been extensively applied to rocket launching system, gas jet cutting control, gas turbine blade cooling, etc. In such applications, wall temperature of an object on which supersonic jet impinges is a very important factor to determine the performance and life of the device. However, wall temperature data of supersonic impinging jets are not enough to data. The present study describes an experimental work to measure the wall temperatures of a vertical flat plate on which supersonic, dual, coaxial jet impinges. An Infrared camera is employed to measure the wall temperature distribution on the impinging plate. The pressure ratio of the jet is varied to obtain the supersonic jets in the range of over-expanded to moderately under-expanded conditions at the exit of coaxial nozzle. The distance between the coaxial nozzle and the flat plate was also varied. The coaxial jet flows are visualized using a Shadow optical method. The results show that the wall temperature distribution of the impinging plate is strongly dependent on the jet pressure ratio and the distance between the nozzle and plate.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.739-742
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• 2002

The supersonic, dual, coaxial jet impinging upon a vertical flat plate has recently been applied to a variety of industrial manufacturing processes, since it has several advantages over a conventional supersonic impinging jet. In the present study, experimentation is carried out to investigate the effects of the impinging angle of the annular flow and the design Mach number on the flow field formed over the vertical flat plate. A convergent-divergent nozzle is used to obtain the inner jet flow, its design Mach number being changed between $1.0\;and\;2.0$. The outer annular nozzle has a constant area of the Mach number of 1.0, and its impinging angle of $0^{\circ}\;and\;20^{\circ}$. The primary jet pressure ratio is changed in the range from 6.0 to 10.0 and for the annular flow, the assistant jet pressure ratio is changed from 1.0 to 4.0. The distance between the dual, coaxial nozzle and flat plate is also changed. Detailed pressure measurements are conducted along the axis of the jet and on the flat plate as well. The impinging coaxial Jet flows are visualized using the Schlieren and Shadow optical methods. The results show that the flow field on the plate is not strongly dependent only on the primary and assistant pressure ratios but also the impinging angle of the annular nozzle.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.403-408
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• 2001

The flow characteristics of impinging jet flow are affected greatly by nozzle plate to distance. An sharp edge nozzle was used to achieve uniform mean velocity at the nozzle inlet, and its diameter is 10 mm(d). Therefore, the flow characteristics on the impinging jet plate can be changed largely by the control of main flow. In the parent study, we investigate the effects of main flow length, its variable is nozle plate to distances(12d, 10d, 8d, 6d and 4d)

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.5
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• pp.716-724
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• 1998

The objective of this research was to investigate the enhancement of heat transfer by mesh in impinging air jet system. The technique used in this research is to place mesh as a turbulence promoter in front of the impinging plate. The heat transfer characteristics with and without mesh, the effect of clearances between impinging plate and mesh, the effect of distance between nozzle exit and impinging plate, and the effect of nozzle exit velocity have been studied experimentally. When mesh was installed in front of the impinging plate, heat transer has been increased due to the acceleration between rectangular holes and divided small jets. When clearances are changed, heat transfer comes to a maximum under the condition of C = 1 mm, irrespective of nozzle exit velocity or H/B. Also the average heat transfer enhancement with mesh has been increased about 44% under the condition of U = 18 m/s, H/B = 2 and C = 1 mm, compared to the result of a flat plate without mesh. And the results of this research are compared with existing heat transfer augmentation method by rectangular or circular rod.