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Hyo-Won Yeom

Bio: Hyo-Won Yeom 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 5, co-authored 10 publications receiving 91 citations.

Papers
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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 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 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

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

Journal ArticleDOI
Iksoo Park1, Sun-Kyoung Kim, Hyo-Won Yeom, Hong-Gye Sung, Jung-Woo Park, Min-Jea Tahk 
TL;DR: In this paper, a control-oriented model for the position and control of the terminal shock in the intake duct of a ramjet engine is presented, which is more suitable for controller design with the objective of regulating the intake shock position.
Abstract: R AMJET-POWERED engines have a history of over 100 years [1]. The secret to efficiency, safety, and performance of ramjet combustion systems has been the correct location and control of the terminal shock in the intake duct [2]. The position of the intake shock is affected by perturbations propagating upstream from the combustor [3] and from disturbances in the freestream [4]. These can lead to the familiar instability problems of unstart or buzz [5,6]. At the same time, these very instabilities can be controlled by pressure perturbations injected by suitably manipulating the exhaust nozzle throat area [7]. To properly evaluate such a control, it is necessary to obtain amodel for the ramjet engine including the intake, combustor, and exhaust nozzle. The issue of shock position control has always been an interesting one [8], but accurately sensing the position of the intake shock for the purpose of active control has been a challenge. In recent years, though, the problemhas attractedmuch attention [9,10], and building on the earlier work on the dynamics of shocks in ducts [3,11], models that may be used for designing intake shock position controllers have been obtained [12,13].However, itmay be noted that all thesemodels were limited to the intake alone and hence could not be directly used to study the effect of the exhaust nozzle throat area variation on the intake shock location. A model that couples the intake with the combustor and exhaust nozzle for a ramjet was first realized recently by our coworkers [14], and it was used [15] to derive a control law for the intake shock location using the nozzle throat area as input. A significant feature of the model in [14] was the use of time lags to capture the physics of upstream anddownstreampropagatingwaves between the intake and combustor. However, these time lags were applied to the primitive variables for simplicity instead of the specific pressure or entropy waves [12]. Second, despite the relatively low order of the global model in [14], the model for each component was multiparameter and nonlinear, in order to capture the various physical phenomena in the intake and combustor. Thus, in deriving the control law in [15], local linearized reduced-order models at several operating points had to be obtained using a system identification tool. The system identification is, unfortunately, a mathematical procedure that results in a set of states that cannot be easily related to the physical variables, thus masking the physical relationships inherent in the system. Control of the terminal shock positionwas obtained indirectly in [15] by defining a related parameter called intake backpressure margin. The present Note differs from these previous works in three significantways. First, wewrite an explicit equation for the dynamics of the intake shock location in a coupled model of the intake and the combustor plus nozzle. Second, a single time-lag parameter is obtained numerically, and applied directly to the shock position variable. Third, the various component models are written using standard quasi-one-dimensional flow relations in such a manner that the physical relationships they represent are apparent. These features make the present model more suitable for controller design with the objective of regulating the intake shock position; hence, it is called a control-oriented model.

12 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors review the current knowledge of the mechanics of cavity-based flameholding in supersonic flows and discuss the non-reacting and reacting cavity flowfield with particular emphasis on the impact of fuel injection location relative to the flameholder.

139 citations

Journal ArticleDOI
TL;DR: In this article, a rectangular open cavity with upstream dual injectors at a freestream Mach number of 1.9 was investigated using high-speed schlieren photography, particle image velocimetry, and surface oil flow techniques.

47 citations

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, a sliding mesh method was applied to take into account the effects of the pintle shape and movement, and the physical nozzle throat based on pintle location was analytically investigated and found to compare well with numerical results.
Abstract: Unsteady numerical simulations of pintle nozzles were implemented to investigate dynamic characteristics of various pintle configurations. To take into account the effects of the pintle shape and movement, a sliding mesh method was applied. The physical nozzle throat based on pintle location was analytically investigated and found to compare well with numerical results. The static and dynamic results are verified with the experimental results. The flow separation shock trains as the pintle strokes are analyzed according to the three pintle models. The response lag and sensitivity of the chamber pressure and nozzle performance were evaluated for pintle reciprocation, insertion, and extraction processes to better understand the dynamic performance of the pintle nozzle. The pressure coupling effects of the propellant burning surface during the pintle reciprocation are conducted, which are compared with the cold-flow cases.

27 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