• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.85-92
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• 2004

As a research to develop a SCRAM jet engine is actively conducted, a necessity to produce a high-enthalpy flow in a laboratory is increasing. In order to develop the SCRAM-jet engine, stabilized combustion in a supersonic flow-field should be attained, in which a duration time of flow is extremely short. Therefore, a mixing process of breathed air and fuel, which is injected into supersonic flow-fields is one of the most important problem. Since, the flow inside SCRAM jet engine has high-enthalpy, an experimental facility is required to produce such high-enthalpy flow-field. In this study, a detonation-driven shock tunnel was built and was used to produce high-enthalpy flow. Further-more, SCRAM jet engine model equipped backward-facing step was installed at test section and flow-fields were visualized using color-schlieren technique and high speed video camera. The fuel was injected perpendicular to the flow of Mach number three behind backward-facing step. The height of the step, distance of injection and injection pressure were changed to investigate the effects of step on a mixing characteristic between air and fuel. The schlieren photograph and pressure histories show that the fuel was ignited behind the step.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1040-1049
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• 1996

The high loading combustion is accomplished by making the turbulent intensity strong and the scale small in the premixed combustor. The Da-mkoler number, which is decreased by short turbulent characteristic time or by long chemical reaction time, can make the distributed reaction flame. So we developed a doubled jet burner for high loading combustion. The doubled jet burner was designed to make the scale of the flame small by the effect of impingement and increasing shear stress with doubled jet. We investigated the turbulence characteristics of unburned mixture and visualized several flames with the typical schlieren photography. Then we studied the influence of several factors that related the scale of flame. Consequently, the doubled jet burner can make the eddy very small. And we can obtain the detail information of the flame scale through ADSF(the Average Distance between Successive Fringes) in the micro- schlieren photography. The ADSF is not a exact flame scale, but it has qualitative trend with increasing turbulent intensity. The ADSF is diminished remarkably with increasing turbulent intensity. The reason is that strong turbulent intensity makes the flame zone thick and flamelets numerous. We can confirm this fact by the signal analysis of ion currents.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.943-949
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• 2002

The propagation of the impulse wave discharged from the Inclined exit of a pipe is investigated through shock tube experiment and numerical computations. The pressure histories and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are analyzed for the range of the incident shock wave Mach number between 1.1 and 1.4. In the shock tube experiments, the impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. Computations using the two-dimensional. unsteady, compressible, Euler equations are carried out to represent the experimented impulse waves. Computed Schlieren images predict the experimented impulse waves with a good accuracy. The results obtained show that for the radial direction the peak pressure of the impulse wave discharged depends upon the Inclined angle of the exit of the pipe. but for the axial direction it is almost constant regardless of the inclined angle of the pipe exit.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.294-299
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• 2012

An investigation into the influence of ultrasonic standing wave on the structural behavior of propane/air premixed flame has been made to get a clue to the combustion reaction acceleration and combustion instability, as well. Visualization technique utilizing the Schlieren method was employed for the observation of structural variation of the premixed flame. The flame shape and propagation velocity were measured according to the variation of equivalence ratio. It was found that the standing wave distorted the flame front and expedited a transition to the flame with turbulent nature.

• Journal of ILASS-Korea
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• v.27 no.1
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• pp.1-10
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• 2022

In this study, an experimental investigation on the effects of the pressure ratio on the wall-impingement spray characteristics of nitrogen gas using a compressed natural gas (CNG) injector was conducted. The transient development of the impingement spray was recorded by a high speed camera with Z-type Schlieren visualization method. The spray behavior under various pressure ratio conditions were analyzed. The experimental results showed that the pressure ratio has positive effect on the development of spray wall-impingement. The effects of the above factor were evaluated in a constant volume chamber at atmospheric conditions. The data from test showed that, with the increase of the pressure ratio, the spray tip penetration (STP) quickly increases before the impingement and gradually increases after the impingement. Additionally, the spray velocity first increases and then sharply decreases on regardless of the injection pressure level. As the spray spreading angle increases, spray area and volume increases rapidly with the increase in STP at the beginning of injection, and finally entered a stable range, has a great correlation with the increase of pressure ratios.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.2
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• pp.34-44
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• 1985

Swirling flows have commonly used for a number of years for the stabilization of high- intensity combustion processes. In general, these swirling flows are poorly understood because of their complexity. This paper, therefore, deals with the experimental study on turbulent diffusion flames with swirling flow in unburned flow field by using a model combustor. The purpose of this study is to investigate quantitatively the swirling air jets issuing from vane swirlers. The fundamental experiments have been performed for the local velocity distribution, turbulence intensity and Schlieren photograph in th jets issuing into the atmosphere.

• Journal of Biomedical Engineering Research
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• v.2 no.2
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• pp.141-144
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• 1981

This paper descirbes about effects of refraction of ultrasonic beam on B-mode tomogram. Both compution based on Snell's law and the experiments performed using B-mode scanner and schlieren optical method are discussed on a circular phantom immersed in water. In these results, if the discrepancy of sound velocity is more than 0. 6%, the distortion of the B-mode image becomes conspicuous and a target beyound the phantom may disappear or displayed as two targets depending on the velocity of the phantom.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.36.2-36.2
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• 2005

• 연구논문집
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• s.23
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• pp.57-62
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• 1993

An experimental investigation was carried out to study the characteristics of concentration of a coaxial jet being tone excited and consisting of $CO_2$, and air. The concentration in a binary gas mixture was measured by using the hot-wire anemometer and flow visualization was performed by the schlieren technique. In the case of excited flow, it is found that acoustic energy is partially transferred to RMS concentration to enhance mixing.

• Journal of the korean Society of Automotive Engineers
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• v.4 no.2
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• pp.13-23
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• 1982

To understand the effects of turbulence on combustion, it was experimentally investigated in the combustion chamber with sub-chamber by using pressure record and high speed Schlieren motion picture. The results show that turbulence can increase the flame propagating rate and there exists a condition under which the total burning time becomes the minimum. And it was also found that there exist three kinds of flame propagating pattern and the total burning time can be reduced with the appropriate selection of sub-chamber size and orifice diameter.