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Hong-Gye Sung

Bio: Hong-Gye Sung is an academic researcher from Korea Aerospace University. The author has contributed to research in topics: Combustion & Combustor. The author has an hindex of 13, co-authored 105 publications receiving 543 citations.


Papers
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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

Proceedings ArticleDOI
25 Jul 2010
TL;DR: In this article, a novel blended solid fuel which mixes paraffin wax of alkane and LDPE of alkene is invented and tested in a slab motor and hybrid rocket motor to visualize droplet entrainment and to analyze combustion characteristics.
Abstract: A Novel blended solid fuel which mixes paraffin wax of alkane and LDPE of alkene is invented and tested in a slab motor and hybrid rocket motor to visualize droplet entrainment and to analyze combustion characteristics. The mechanical strength of blended fuel was investigated increasing the LDPE wt%. Overall regression rate of PR95PE05 is found to be 3.9 factors higher compared to that of HDPE. Improved combustion efficiency was achieved with respect to pure paraffin fuel where performance gain was comparable to that of SP-1a fuel of Stanford University. Analysis of the spectrum of the chamber pressure revealed no critical instability for the range of this study. The PR95PE05 blended fuel can be regarded comparatively effective for the hybrid rocket fuel in terms of mechanical strength, combustion performance, and combustion instability.

36 citations

Journal ArticleDOI
TL;DR: In this article, boron particles were coated with glycidyl azide polymer (GAP) to improve their combustion characteristics, and the coated particles were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrographs.
Abstract: Elemental boron has attracted considerable attention as a potential high energetic material for explosives and propellants. However, its use has been hindered by its high vaporization temperature and surface oxide layer. In this study, boron particles were coated with glycidyl azide polymer (GAP) to improve their combustion characteristics. The coated particles were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy. XPS performed before and after Ar+ ion sputtering confirmed that the azide (−N3) group of GAP was positioned at the proximity of the boron surface. In addition, B@GAP particles could be decorated with metallic Ag (∼10 nm) nanoparticles. The combustion characteristics were examined using a newly designed pre-heated (1,800 K) drop tube furnace and a high speed camera. Two stages of combustion were observed for a dust cloud of GAP-coated boron particles. The burning time was estimated to be approximately 37.5 msec.

31 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigate combustion characteristics of the cylindrical multiport grain of a hybrid rocket motor and highlight the effect of port number on the regression rate of combustion.
Abstract: The purpose of this experimental research is to investigate combustion characteristics of the cylindrical multiport grain of a hybrid rocket motor and to highlight port number effects on the regression rate. The physical model of concern includes an oxidizer supply system, a multiport fuel grain, and a combustor with pre- and postchamber. Several design parameters, such as the port number, fuel type (polyethylene and polymethylmethacrylate), and end-burning effects, are experimentally analyzed using small- and large-scale grain, where grain diameters of 50 and 96 mm are used, respectively. For the oxidizer mass flux ranging from 10 to 300 kg/m2· s, the increase of port number positively shifts the oxidizer-to-fuel ratio to near its optimum value and the increase of regression rate is damped beyond three ports, regardless of grain size. It is observed that the radiation effect on the regression rate of polyethylene is much more dominant than that of polymethylmethacrylate, and that the end-burning effect ...

28 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


Cited by
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01 Jan 1994
TL;DR: Numerical experiments indicate no oscillation and robustness of the scheme for shock/expansion waves, and for a single contact discontinuity, this scheme gives the numerical flux of the exact solution of the Riemann problem.
Abstract: A flux splitting scheme is proposed for the general nonequilibrium flow equations with an aim at removing numerical dissipation of Van-Leer-type flux-vector splittings on a contact discontinuity. The scheme obtained is also recognized as an improved Advection Upwind Splitting Method (AUSM) where a slight numerical overshoot immediately behind the shock is eliminated. The proposed scheme has favorable properties: high-resolution for contact discontinuities; conservation of enthalpy for steady flows; numerical efficiency; applicability to chemically reacting flows. In fact, for a single contact discontinuity, even if it is moving, this scheme gives the numerical flux of the exact solution of the Riemann problem. Various numerical experiments including that of a thermo-chemical nonequilibrium flow were performed, which indicate no oscillation and robustness of the scheme for shock/expansion waves. A cure for carbuncle phenomenon is discussed as well.

508 citations

Journal ArticleDOI
TL;DR: A comprehensive review of the advances made over the past few decades in the areas of synthesis, properties, and applications of metal-based energetic nanomaterials is provided in this paper.

268 citations

04 Jun 2008
TL;DR: In this article, a coupling methodology between an upstream Reynolds Averaged Navier-Stokes (RANS) simulation and a large eddy simulation (LES) further downstream is presented.
Abstract: Abstract A coupling methodology between an upstream Reynolds Averaged Navier–Stokes (RANS) simulation and a Large Eddy Simulation (LES) further downstream is presented. The focus of this work is on the RANS-to-LES interface inside an attached turbulent boundary layer, where an unsteady LES content has to be explicitly generated from a steady RANS solution. The performance of the Synthetic-Eddy Method (SEM), which generates realistic synthetic eddies at the inflow of the LES, is investigated on a wide variety of turbulent flows, from simple channel and square duct flows to the flow over an airfoil trailing edge. The SEM is compared to other existing methods of generation of synthetic turbulence for LES, and is shown to reduce substantially the distance required to develop realistic turbulence downstream of the inlet.

180 citations

Journal ArticleDOI
TL;DR: Although a vast number of theoretical and algorithmic issues still remain open, this paper advances pseudospectral methods along several new directions and outlines the current theoretical pitfalls in computation and control.
Abstract: Recent convergence results with pseudospectral methods are exploited to design a robust, multigrid, spectral algorithm for computing optimal controls. The design of the algorithm is based on using the pseudospectral differentiation matrix to locate switches, kinks, corners, and other discontinuities that are typical when solving practical optimal control problems. The concept of pseudospectral knots and Gaussian quadrature rules are used to generate a natural spectral mesh that is dense near the points of interest. Several stopping criteria are developed based on new error-estimation formulas and Jackson's theorem. The sequence is terminated when all of the convergence criteria are satisfied. Numerical examples demonstrate the key concepts proposed in the design of the spectral algorithm. Although a vast number of theoretical and algorithmic issues still remain open, this paper advances pseudospectral methods along several new directions and outlines the current theoretical pitfalls in computation and control.

179 citations

Journal Article
01 Jan 1998-Scopus
TL;DR: In this paper, the results from large eddy simulations (LES) and direct numerical simulations (DNS) of a two-dimensional, spatially developing, compressible planar free jet undergoing an idealized, exothermic, chemical reaction of the type F+rOx→(1+r)P are presented in order to assess several subgrid-scale combustion models.
Abstract: Results from large eddy simulations (LES) and direct numerical simulations (DNS) of a two-dimensional, spatially developing, compressible planar free jet undergoing an idealized, exothermic, chemical reaction of the type F+rOx→(1+r)P are presented in order to assess several subgrid-scale (SGS) combustion models. Both a priori and a posteriori assessments are conducted. The SGS turbulence model used is the dynamic Smagorinsky model (DSM). Two classes of SGS combustion models are employed in this study. These include the conserved scalar approach and the direct closure approach. Specifically, the SGS combustion models involve several forms of direct filtered reaction rate closures, including a scale similarity filtered reaction rate model (SSFRRM), and a mixing controlled strained laminar flamelet model (SLFM) in the form of thermochemical state relationships, obtained from the DNS, and two assumed forms for the subgrid mixture fraction filtered density function (FDF). In general, LES results are in reasonable agreement with DNS results and highlight the performance of the various SGS combustion models. In particular, in the context of the present study, it is found that: (1) the SLFM cases overpredict product formation due to their inability to capture finite-rate chemistry effects; (2) due to the relatively low values of the SGS mixture fraction variance in the flow under study, the SLFM results are not sensitive to the form of the assumed FDF; and (3) in comparison to the other models investigated, the SSFRRM combustion model provides the best agreement with the DNS for product formation.

169 citations