• Proceedings of the KSME Conference
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• 2001.06e
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• pp.323-328
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• 2001

Supersonic coaxial, axisymmetric, jets issuing from various kinds of dual coaxial nozzles were experimentally investigated. Four different kinds of coaxial, dual nozzles were employed to characterize the major features of the supersonic, coaxial, dual jets. Two convergent-divergent supersonic nozzles with an impinging angle in the jet axis of the annular jets were designed to have the Mach number 2.0 and used to compare the coaxial jet flows with those discharging from two sonic nozzles. The primary pressure ratio was changed in the range from 4.0 to 10.0 and the assistant jet ratio from 1.0 to 4.0. The results obtained show that the assistant jets from the annular nozzle affect the coaxial jet flows and an increase of both the primary jet pressure ratio and assistant jet pressure ratio produces longer supersonic length of the dual, coaxial jet.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.417-422
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• 2001

The shock structure of supersonic, dual, coaxial jet is experimentally investigated. Eight different kinds of coaxial, dual nozzles are employed to observe the major features of the near field shock structure of the supersonic, coaxial, dual jets. Four convergent-divergent supersonic nozzles having the Mach number of 2.0 and 3.0, and are used to compare the coaxial jet flows discharging from two sonic nozzles. The primary pressure ratio is changed in the range between 4.0 and 10.0 and the assistant jet pressure ratio from 1.0 to 4.0. The results obtained show that the impinging angle, nozzle geometry and pressure ratio significantly affect the near field shock structure, Mach disk location and Mach disk diameter. The annular shock system is found depending the assistant and primary jet pressure ratios.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.2
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• pp.51-58
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• 2001

Supersonic, axisymmetric, jets issuing from several kinds of dual, coaxial, nozzles were experimentally investigated. Four different kinds of coaxial, dual nozzles were employed to characterize the major. features of the supersonic, coaxial, dual jets. Two convergent-divergent supersonic nozzles with different impinging angle on the jet axis of were designed to have the Mach number 2.0 and used to compare the coaxial jet flows with those discharging from two sonic nozzles. The primary pressure ratio was changed in the range from 4.0 to 10.0 and the assistant jet ratio from 1.0 to 4.0. The results obtained show that the assistant jets from the annular. nozzle affect the coaxial jet flows and an increase of both the primary jet pressure ratio and assistant jet pressure ratio lead to a longer supersonic length of the dual, coaxial jet.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.2107-2115
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• 2003

A supersonic dual coaxial jet has been employed popularly for various industrial purposes, such as gasdynamic laser, supersonic ejector, noise control and enhancement of mixing. Detailed characteristics of supersonic dual coaxial jets issuing from an inner supersonic nozzle and outer sonic nozzles with various ejection angles are experimentally investigated. Three important parameters, such as pressure ratios of the inner and outer nozzles, and outer nozzle ejection angle, are chosen for a better understanding of jet structures in the present study. The results obtained from the present experimental study show that the Mach disk diameter becomes smaller, and the Mach disk moves toward the nozzle exit, and the length of the first shock cell decreases with the pressure ratio of the outer nozzle. It was also found that the highly underexpanded outer jet produces a new oblique shock wave, which makes jet structure much more complicated. On the other hand the outer jet ejection angle affects the structure of the inner jet structure less than the pressure ratio of the outer nozzle, relatively.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.664-669
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• 2001

The characteristics of dual coaxial jet which composed of inner supersonic nozzle of 26500 in constant expansion rate with 1.91 design Mach number and outer converging one with $40^{\circ}$ converging angle with the variation of outer nozzle stagnation pressures are experimentally investigated in this paper. In which the stagnation pressure for the inner supersonic nozzle is 750kPa thus, the inner jet leaving the nozzle is slightly underexpanded. The plenum pressures of outer nozzle are varied from 200 to 600kPa. Flow visualizations by shadowgraph method, impact pressure and centerline static pressure measurements of dual coaxial jet are presented. The results show that the presence of outer jet affects significantly the structures and pressure distributions of inner jet. And outer jet causes Mach disk which does not appear for the case of single jet stream. As the stagnation pressure of outer jet increases, impact pressure undulation is severe, but the average impact pressure keeps high far downstream.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.426-431
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• 2001

This paper experimentally investigates the characteristics of dual coaxial jet issuing from inner supersonic nozzle and four kinds of outer converging nozzle of 40, 50, $60^{\circ}$ and $70^{\circ}$ in outer ejection angle. The pressure ratio of the stagnation to the exit ambient pressures in the inner supersonic nozzle of constant expansion rate is 7.5, which is corresponded to the condition of a slightly underexpanded, and that of outer nozzle is 4.0. Flow visualizations by using of shadowgraph method, impact pressure and centerline static pressure measurements are presented. It is found that the jet structure is changed significantly by the variation of outer nozzle ejection angle. Impact pressure level is lower and undulation of static pressure is higher, as the injection angle of outer jet increases.

• 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 Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.15-18
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• 2003

The present study addresses an experimental investigations of the near field flow structures of supersonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the sonic and supersonic free jets. The interactions between the secondary swirl and inner soni $c^ersonic jets are quantified by a fine pilot impact and static pressure measurements and are visualized by using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary soni $c^ersonic jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary sonic and supersonic jets, compared with the secondary stream of no swirl. The results show that the presence of annular swirl stream causes the Mach disk to move more downstream, with the increased diameter, and remarkably reduces the fluctuations of the impact pressures in the supersonic dual coaxial jet, compared with the case of the secondary annular stream of no swirl.swirl.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1771-1776
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• 2003

The supersonic swirl jet is being extensively used in many diverse fields of industrial processes since those lead to more improved performance, compared with the conventional supersonic no swirl jet. In the present study, an experiment is carried out to investigate the effect of annular swirl jet on the supersonic dual coaxial jet. A convergent-divergent nozzle with a design Mach number of 1.5 is used for the supersonic primary jet, and the sonic nozzles with four tangential inlets are used to make the secondary swirl jet. The primary jet pressure ratio is varied in the range from 3.0 to 7.0 and the outer annular jet pressure ratio is from 1.0 to 4.0. The interactions between the annular swirl and the inner supersonic jet are quantified by the pitot impact and static pressure measurements and visualized by using the Schlieren optical method. The results show that annular swirl jet alters the shock structure and impact pressure distributions compared with no swirl jet.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.4
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• pp.94-101
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• 2001

The shock structure of dual coaxial jet is experimentally investigated. Eight different kinds of coaxial, dual nozzles are employed to observe the major features of the near field shock structure on the supersonic, coaxial, dual jets. Four convergent-divergent supersonic nozzles having the Mach number 2.0 and 3.0 are used to compare the coaxial jet flows discharging from two sonic nozzles. The primary pressure ratio is changed in the range between 1.0 and 10.0, and the assistant jet ratio from 1.0 to 4.0. The results show that the impinging angle, nozzle geometry and pressure ratio significantly affect the near field shock structure, Mach disk location and Mach disk diameter.