• Fire Science and Engineering
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• v.29 no.2
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• pp.84-91
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• 2015

The purpose of this study is to suggest the reasonable model of the caliber in suction nozzle, the pressure of suction nozzle, and the flow rate about foam system of line proportioner type using in the pumpcar. To test this, the experimental study was accomplished on the ground of the standards for the Performance Certification and Product Inspection of Foam Fire-extinguishing Chemical Mixing Machine. Aqueous Film Forming Foam in 3% and pipe type air foam nozzle with line proportioner FE 40 type were used. Test result showed that the pressure of suction nozzle within the limits between 0.25 MPa and 0.35 MPa was appropriate when the caliber in suction nozzle is 4 mm. Also, the pressure of suction nozzle within the limits between 0.45 MPa and 0.60 MPa was appropriate in the higher pressure than 4 mm when the caliber in suction nozzle is 5 mm.

• 한국연소학회:학술대회논문집
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• 1997.06a
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• pp.77-87
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• 1997

The axisymmetric Navier-Stokes model together with detailed chemical kinetics and variable transport properties has been applied to analyze the effects of the multidimensional flow on the flame characteristics in the nitrogen-diluted hydrogen counterflow nonpremixed flame. Computations are performed for two nozzle exit area-averaged velocities. Effects of multidimensional flow and strain rate on the near-extinction structure of the highly diluted hydrogen flames are discussed in detail.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.127-130
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• 2003

This paper presents the numerical thermal analysis for regeneratively cooled rocket thrust chambers. An integrated numerical model incorporates computational fluid dynamics for the hot-gas thermal environment, and thermal analysis for the liner and coolant channels. The flow and temperature fields in rocket thrust chambers is assumed to be axisymmetric steady state which is presumed to the combustion liner. The heat flux computed from nozzle flow is used to predict the temperature distribution of the combustion liner. As a result, we present the wall temperature of combustion liner and the temperature change of coolant.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.190-199
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• 1993

In order to find the effect of flame interaction on NO production, dual laminar diffusion flames issuing from two rectangular nozzles were investigated theoretically. Chemical equilibrium model and Zeldovich mechanism were used in numerical model. The effect of four major parameters on NO production were inspected. These parameters are nozzle spacing, Raynolds number, aspect ratio of nozle cross section and velocity of secondary flow. It is found that interaction of flames enhances production of n. It is also found that multiflames with large spacing, small aspect ratio and strong secondary flow product less n.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.599-604
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• 1997

One of important inconsistencies in the six-equation model predictions has been found to be the force experienced by a single bubble placed in a convergent stream of liquid. Various sets of governing equations yield different amount of forces to hold the bubble stationary in a convergent nozzle. By using the first order potential flow theory, it is found that the six-equation model can not be used to estimate the force experienced by a deformed bubble. The theoretical value of the particle stress of a bubble in a convergent nozzle flow has been found to be a function of the Weber number when bubble distortion is allowed. This force has been calculated by using different sets of governing equations and compared with the theoretical value. It is suggested in this study that the bubble size distribution function can be used to remove the presented inconsistency by relating the interfacial variables with different moments of the bubble size distribution function. This study also shows that the inconsistencies in the thermal-hydraulic governing equation can be removed by mechanistic modeling of the phasic interface.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.947-954
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• 2015

The homogeneous coating of a flexible film that is applied to dye-sensitized solar cells is related to the performance and durability of the product. The applied coating is obtained from the uniform temperature distribution and the mass flow rate in the nozzle of the hot air dryer. In this study, we determine the uniform temperature distribution and mass flow rate of each nozzle by performing numerical simulations to understand how various factors affect the performance of the hot air dryer. The numerical model is composed of the momentum equation for flow motion and the energy equation for temperature. In addition, we compare the numerical results to the experimental results to validate the model. Based on the results, the round-hole plate inside the hot air dryer significantly affects the uniform temperature and the mass flow rate.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.761-770
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• 2008

The report presents turbulent Navier Stokes computations on twin engine afterbody model with jet exhaust. The computations are carried out for free-stream Mach number of 0.8 to 1.20 and jet pressure ratio of 3.4 to 7.8. The Spalart-Allmaras turbulence model is used in the computations. Comparison is made with experimental data and Cp distribution around the afterbody is found to agree well with experiments. Flow features of the exhaust jet like under expansion, over expansion, Mach discs, etc are well captured. The effect of nozzle pressure ratio and flight Mach number are studied in detail. These computations serve as validation of the in-house code for twin jet afterbody.

• Journal of the Korean Institute of Gas
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• v.26 no.6
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• pp.9-15
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• 2022

In order to verify the durability of the high-pressure hydrogen tank in the operating pressure range, a hydraulic rupture test should be performed. However, if the bubbles generated by the initial injection process of water are attached to the inner wall of the tank and remain, a sudden pressure change of the bubbles during the rupture of the pressurized tank may cause shock and noise. Therefore, in this study, the flow velocity required to remove the bubbles remaining on the inner wall of the tank was predicted through simplified formulas, and the shape of the injection nozzle to maintain the flow velocity was determined based on the shape of the hydrogen tank for the hydrogen bus. In addition, a numerical model was developed to predict the change in flow velocity according to the inlet pressure, and an experiment was performed through a model tank to prove the validity of the prediction result. As a result of the experiment, the flow velocity near the tank wall was similar to the predicted value of the analysis model, and when the inlet pressure was 1.5 to 5.5 bar, the minimum size of the removable bubble was predicted to be about 2.2 to 4.6 mm.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1915-1920
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• 2004

An edge tone is the discrete tone or narrow-band sound produced by an oscillating free shear layer impinging on a rigid surface. In this paper we present a two-dimensional edge tone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle by the finite difference lattice Boltzmann method. We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing a conventional FDLB model, and also use a boundary fitted coordinates. The jet is chosen long enough in order to guarantee the parabolic velocity profile of the jet at the outlet, and the edge consists of a wedge with an angle of ${\alpha}=23^{\circ}$ . At a stand-off distance ${\omega}$ , the edge is inserted along the centreline of the jet, and a sinuous instability wave with real frequency f is assumed to be created in the vicinity of the nozzle and to propagate towards the downstream. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. Its interaction with the wedge produces an irrotational feedback field which, near the nozzle exit, is a periodic transverse flow producing the singularities at the nozzle lips.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.1-14
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• 2009

When the stagnation temperature increases, the specific heat does not remain constant and start to vary with this temperature. The gas is perfect, it's state equation remains always valid, except, it was called by gas calorically imperfect or gas at high temperatures. The purpose of this work is to develop a mathematical model for a normal shock wave normal at high temperature when the stagnation temperature is taken into account, less than the dissociation of the molecules as a generalisation model of perfect for constant heat specific. A study on the error given by the perfect gas model compared to our model is presented in order to find a limit of application of the perfect gas model. The application is for air.