scispace - formally typeset
Search or ask a question
Author

Sangkyu Yoon

Bio: Sangkyu Yoon is an academic researcher from Korea Aerospace University. The author has contributed to research in topics: Diffuser (thermodynamics) & Supersonic speed. The author has an hindex of 3, co-authored 4 publications receiving 46 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the design and operational parameters of rocket exhaust diffusers equipped to simulate high-altitude rocket performance on the ground were investigated and characterized using a comprehensive approach (theoretical, numerical, and experimental).
Abstract: The design and operational parameters of rocket exhaust diffusers equipped to simulate high-altitude rocket performance on the ground were investigated and characterized using a comprehensive approach (theoretical, numerical, and experimental). The physical model of concern includes a rocket motor, a vacuum chamber, and a diffuser, which have axisymmetric configurations. Further, the operational characteristics of a rocket exhaust diffuserwereanalyzed froma flowdevelopmentpointof view.Emphasiswasplacedondetailed flowstructure inthe diffuser, to observe the pressure oscillation in both the vacuum chamber and diffuser, which determines the minimum rocket-motor pressure required to start the diffuser. Numerical simulations were compared with experimental data on startup and in operational conditions to understand the effects of major design parameters, including the area ratio of diffuser to rocket-motor nozzle throat, the rocket-motor pressure, and the vacuumchamber size. Nomenclature Ad = inner cross-sectional area of diffuser Ade = exit cross-sectional area of diffuser Ae = exit cross-sectional area of rocket nozzle At = throat cross-sectional area of rocket nozzle

27 citations

Journal ArticleDOI
TL;DR: In this article, a numerical analysis was conducted to investigate and characterize the unsteadiness of the flow structure and oscillatory vacuum pressure inside of a supersonic diffuser equipped to simulate high-altitude rocket performance on the ground.
Abstract: A numerical analysis was conducted to investigate and characterize the unsteadiness of the flow structure and oscillatory vacuum pressure inside of a supersonic diffuser equipped to simulate high-altitude rocket performance on the ground. A physical model including a rocket motor, vacuum chamber, and diffuser, which have axisymmetric configurations was employed. Emphasis was placed on investigating the physical phenomena of very complex and oscillatory flow evolutions in the diffuser operating very close to the starting condition, i.e. at a minimum starting condition, which is one of the major important parameters from a diffuser design point of view.

16 citations

Proceedings ArticleDOI
07 Jan 2008
TL;DR: In this paper, a comprehensive approach (theoretical, numerical, and experimental approach) has been conducted to study the design and operation parameters of supersonic exhaust diffusers simulating high altitude condition on the ground.
Abstract: A comprehensive approach (theoretical, numerical, and experimental approach) has been conducted to study the designand operationparameters of supersonic exhaust diffusers simulating high altitude condition on the ground. A physical model of concern includes a rocket motor, a vacuum chamber, and a diffuser, which have axisymmetric configurations, using nitrogen gas as a driving fluid. An analysis has been conducted to investigate operation characteristics of a supersonic exhaust diffuser from a flow-development point of view. Emphasis is placed on physical phenomena and several designand operationparameters of the diffuser such as the area ratio of the diffuser to the rocket nozzle, the vacuum chamber size, and the minimum starting pressure of the rocket motor to start the diffuser.

4 citations

01 Mar 2008
TL;DR: In this paper, a numerical analysis has been conducted to investigate and characterize the unsteadiness of flow structure and oscillatory vacuum pressure inside of a supersonic diffuser equipped to simulate the high-altitude rocket test on the ground.
Abstract: A numerical analysis has been conducted to investigate and characterize the unsteadiness of flow structure and oscillatory vacuum pressure inside of a supersonic diffuser equipped to simulate the high-altitude rocket test on the ground. A physical model of concern includes a rocket motor, a vacuum chamber, and a diffuser, which have axisymmetric configurations, using nitrogen gas as a driving fluid. Emphasis is placed on investigating physical phenomena of very complex and oscillatory flow evolutions in the diffuser operating at very close to the starting condition, i.e. minimum starting condition, which is one of major important parameters in diffuser design points of view.

Cited by
More filters
Journal ArticleDOI
TL;DR: In this article, the authors investigate the operation condition of a fluidic thrust vector using injection of the control flow tangential to the main jet direction; co-flow injection is used to analyze the dynamic characteristics of fluidic control of jet vectoring up-and downward from the nozzle axis, so that the response time of jet deflection to control flow injection and the pressure dispersion on the nozzle wall were investigated.
Abstract: The purpose of this research is to investigate the operation condition of fluidic thrust vector using injection of the control flow tangential to the main jet direction; co-flow injection. The physical model of concern includes a chamber and a supersonic nozzle for supersonic main jet injection, and two chambers with slots for control flow injection. Steadystate numerical and experimental studies were conducted to investigate operating parameters; detailed flow structures, jet deflection angles, and shock effects were observed near the nozzle exit. An unsteady numerical calculation was conducted to analyze the dynamic characteristics of fluidic control of jet vectoring up- and downward from the nozzle axis, so that the response time of jet deflection to control flow injection and the pressure dispersion on the nozzle wall were investigated. Internal nozzle performance was predicted for total pressure range of the jet from 300 kPa to 1000 kPa to the control flow pressure from 120 to 200 kPa. To take into account the important features of high-speed flows, including shock-boundary layer interactions, a low Reynolds number k-e turbulence model with compressible-dissipation and pressure-dilatation effects was applied.

43 citations

Journal ArticleDOI
TL;DR: In this paper, the design and operational parameters of rocket exhaust diffusers equipped to simulate high-altitude rocket performance on the ground were investigated and characterized using a comprehensive approach (theoretical, numerical, and experimental).
Abstract: The design and operational parameters of rocket exhaust diffusers equipped to simulate high-altitude rocket performance on the ground were investigated and characterized using a comprehensive approach (theoretical, numerical, and experimental). The physical model of concern includes a rocket motor, a vacuum chamber, and a diffuser, which have axisymmetric configurations. Further, the operational characteristics of a rocket exhaust diffuserwereanalyzed froma flowdevelopmentpointof view.Emphasiswasplacedondetailed flowstructure inthe diffuser, to observe the pressure oscillation in both the vacuum chamber and diffuser, which determines the minimum rocket-motor pressure required to start the diffuser. Numerical simulations were compared with experimental data on startup and in operational conditions to understand the effects of major design parameters, including the area ratio of diffuser to rocket-motor nozzle throat, the rocket-motor pressure, and the vacuumchamber size. Nomenclature Ad = inner cross-sectional area of diffuser Ade = exit cross-sectional area of diffuser Ae = exit cross-sectional area of rocket nozzle At = throat cross-sectional area of rocket nozzle

27 citations

Journal ArticleDOI
TL;DR: In this article, a second throat ejector using nitrogen as the primary fluid is considered for the creation of a low vacuum in a high-altitude testing facility for large-area-ratio rocket motors.
Abstract: DOI: 10.2514/1.39219 In the present work, a second throat ejector using nitrogen as the primary fluid is considered for the creation of a low vacuum in a high-altitude testing facility for large-area-ratio rocket motors. Detailed numerical investigations have been carried out to evaluate the performance of the ejector for various operational conditions and geometric parametersduring thenonpumpingandpumpingmodesof operation.Inthenonpumpingmode,the lowestvacuum chamberpressureisattainedwhentheprimaryjetjustexpandsuptothemixerthroatandtheresultingsingleshock cellsealsthethroatagainstanybackflow.Thestudyillustrateshoweachgeometricandoperationalparameterofthe ejector can be optimized to meet the test requirements in a high-altitude testing facility byensuring that the primary jet completely expands without a strong impact on the duct wall. When the rocket motor is fully started, due to the self-pumping action, the required vacuum is almost maintained by the exhaust flow itself and the external nitrogen ejector plays only a supplementary role. Numerical predictions for both nonpumping and pumping modes of operation have been validated with experimental data obtained from a scaled-down model of a high-altitude testing facility.

23 citations

Journal ArticleDOI
TL;DR: In this paper, a detailed three-dimensional numerical simulation was conducted to investigate the flow and H2-air mixing characteristics in a scramjet engine with two intake sidewalls and a cavity flameholder.
Abstract: A detailed three-dimensional numerical simulation was conducted to investigate the flow and H2-air mixing characteristics in a scramjet engine with two intake sidewalls and a cavity flameholder. Turbulence closure was achieved using a model that combines the low-Reynolds-number k-e two-equation model and Sarkar and Wilcox’s compressible turbulent-correction model. The governing equations were solved numerically by means of a finite volume, preconditioned flux-differencing scheme. Cases of with and without intake sidewalls were considered. Intake sidewalls were found to strongly affect the inlet flow structure, which became more complex in the nonuniform flowfield on the cross section perpendicular to the engine axis. The complex and nonuniform flow affected the H2-air mixing pattern inside the combustion chamber, unlike the pattern of the case of without sidewalls. To verify the accuracy of the simulation, the computed wall pressure was compared with the experimental data. Mixing efficiency and fuel-propa...

20 citations

Journal ArticleDOI
TL;DR: In this paper, an assessment of two-equation turbulence models, the low Reynolds k-e and k-ω SST models, with the compressibility corrections proposed by Sarkar and Wilcox, has been performed.
Abstract: An assessment of two-equation turbulence models, the low Reynolds k-e and k-ω SST models, with the compressibility corrections proposed by Sarkar and Wilcox, has been performed. The compressibility models are evaluated by investigating transonic or supersonic flows, including the arc-bump, transonic diffuser, supersonic jet impingement, and unsteady supersonic diffuser. A unified implicit finite volume scheme, consisting of mass, momentum, and energy conservation equations, is used, and the results are compared with experimental data. The model accuracy is found to depend strongly on the flow separation behavior. An MPI (Message Passing Interface) parallel computing scheme is implemented.

15 citations