• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.68-76
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• 2016

This research is carried out for the performance evaluation of the injector that is one of the critical components of bipropellant-rocket-engine. Spray characteristics are investigated in detail according to the recess length and injection pressure on the swirl-coaxial-injector using gaseous methane and liquid oxygen as propellants. A visualization is conducted by the Schlieren photography that is composed of a light source, concave mirrors, knife, and high-speed-camera. A hollow-cone-shape is identified in the liquid spray that is spread only by inner injector and the spray angle is decreased due to the diminution of swirl strength in accordance with the increase of the length of injector orifice. When the injector sprays the liquid through the inner injector with the aid of gas through the outer injector, the spray angle in external mixing region tends to increase with rise of the recess length, while in internal mixing region, it is decreased. It is also confirmed that the same tendency of the spray angle with recess length appears irrespective of the injection pressure of liquid spray.

• Journal of ILASS-Korea
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• v.1 no.3
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• pp.29-36
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• 1996

The present study systematically investigates the effect of evaporation rate on the combustion characteristics and the flame stabilization in a gasoline engine. A constant volume combustion chamber was used to elucidate a basic combustion characteristics and the premixer was installed to control temperature and equivalence ratio. And the maximum pressure, combustion duration and flame propagation according to the evaporation rate were measured to determine the optimal temperature range for evaparating a gasoline fuel. These experimental results indicate that the combustion characteristics such as combustion chamber pressure and combustion duration were deteriorated by decreasing surrounding temperature of fuel injected. It was also found that the overall gasification process for gasoline fuel was strongly influenced by a combustion chamber temperature rather than a premixer temperature.

• Journal of ILASS-Korea
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• v.2 no.2
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• pp.24-34
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• 1997

This paper describes the investigation of combustion characteristics of gasoline-methanol blend in constant volume combustion chamber. A constant volume combustion chamber was used to elucidate a basic combustion characteristics and the premixer was installed to control temperature and equivalence ratio. And the maximum pressure, combustion duration and flame propagation according to the evaporation rate were measured to determine the optimal temperature range for evaporating a blend fuel. These experimental results indicate that the combustion characteristics such as combustion chamber pressure and combustion were deteriorated by decreasing surrounding temperature of fuel. These experimental results indicate that the combustion characteristics such as combustion chamber pressure and combustion were deter orated by decreasing surrounding temperature of fuel injected. It was also found that the overall gasification process for methanol blend fuel was influenced by a combustion chamber temperature rather than a premixer temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.12
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• pp.1652-1661
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• 2000

A visualization study using the schlieren method is adopted in an optically-accessible, cylindrical constant volume combustion chamber to identify the mechanism of ignition energy and ignition system interaction in spark ignited, lean gasoline-air mixture. In order to research the effects of ignition system on flame propagation, two kinds of ignition system are designed, and several kinds of spark plugs are tested and evaluated. To control the discharge energy, the dwell time is varied. The initial flame development is quantified in terms of 2-D images which provides information about the projected flame area and development velocity as a function of ignition system and discharge energy. The results show that high ignition energy and extended spark plug gap can shorten the combustion duration in lean mixtures. The material, diameter and configuration of electrodes the flame development by changing the transfer efficiency from electrical energy to chemical energy and discharge energy. However these factors do not affect of flame development as much a ignition energy or extended gap does.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3386-3394
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• 1994

An experimental study has been performed on the flow over a rotating disk, where the diameter of the disk is 500 mm and the maximum vertical deviation of the upper surface is $50 \mu{m}$ for the whole range of the angular velocity up to 3400 rpm. The flow visualization experiment for the wall jet flow induced by impinging circular jet is carried out using schlieren system and measurements are made by 3-hole and 5-hole pitot tubes. Schlieren photographs show that as the rotating speed increases the wall jet flow becomes more stable and the size of the largest eddies becomes smaller. Measurements for impinging jet flow on the stationary disk verify the accuracy of the present experiment, and those for free rotating disk flow display the existence of transition region from laminar to turbulent flows. Measurements for impinging jet flow on the rotating disk exhibit the interaction between the wall jet and the viscous pumping effect, which explains the decay in size of turbulent eddies illustrated by the schlieren photographs.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.572-579
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• 2009

This study is to investigate experimentally the flame structure and propagation mechanism in dust explosions and to provide the fundamental knowledge. Upward propagating laminar dust flames in a vertical duct of 1.8 m height and 0.15 m square cross-section are observed and flame front is visualized using by a high-speed video camera. Also, the thicknesses of preheated and reaction zone have been determined by a schlieren, electrostatic probe and thermocouple. The thickness of preheated zone in lycopodium dust flame is observed to be 4~13 mm, about several orders of magnitude higher than that of premixed gaseous flames. From the experimental results by a PIV(Particle Image Velocimetry) system, a certain residence time of the unburned particle in preheated zone is needed to generate combustible gas from the particle. The residence time will depend on preheated zone thickness, particle velocity and flame propagation velocity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.363-367
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• 2016

A test section of a supersonic wind tunnel was designed for the analysis of flow characteristics over a backward-facing step with Mach 1.0 slot injection in a supersonic flow of Mach 2.5. The cavity flow of a high-speed vehicle is very complex at supersonic speed, so it is necessary to do experiments using supersonic wind tunnels to verify numerical analysis methods. The previous 2D symmetrical nozzle was replaced with an asymmetrical nozzle. The inviscid nozzle contour was designed using Method of Characteristics (MOC), and the boundary layer thickness correction was reflected by experimental data from the wind tunnel. The results were compared with a CFD analysis. The PID control system was changed to be based on the change of tank pressure. This improved the control efficiency, and the run times of supersonic flow increased by about 1 second. The flow characteristics over a backward facing step with slot injection were visualized by a Schlieren device. This equipment will be used for an experimental study of the film cooling effectiveness over a cavity with various velocities, mass flows, and temperatures.