• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.18-28
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• 2016

Numerical analysis was conducted as a preliminary study for evaluating the dual bell nozzle. For future parametric studies, a dual bell nozzle was designed, and thereafter inlet condition, turbulence model, and the number of optimum grids were determined. Dual bell nozzle was designed based on the KSLV-II first stage nozzle. Inlet condition was determined to frozen flow model of non-reacting eight species by comparing with the design values. SST $k-{\omega}$ model turned out to be suitable as turbulence model. About 150 thousand of the grids were selected after grid sensitivity tests. Based on the results determined in this study, we plan to investigate performance gain of the KSLV-II by adopting a proposed dual bell nozzle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.4
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• pp.215-224
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• 2009

Analysis for various driven nozzle position changes. The analysis was done for different Reynolds number in entrance region of jet-pump and for several diameter ratios of driven nozzle. (1) The largest absorption energy was found at the point s=1 in condition of diameter ratio 1:3.21 and point s=0.5 in condition of diameter ratio 1:2.25. (2) The absorption energy was not related to the change of entrance velocity and the driven nozzle position having the largest absorption energy was function for cross section ratio. (3) As the position of driven nozzle moves to the downstream, the absorption energy gets weaker. Because the energy from swirl was lost at the cross section gets smaller. (4) As the position of driven nozzle moves to the downstream, the injection energy leans to the upper direction wall and as the Reynolds number increase, the lean phenomenon is more distinct. (5) The flow quantity of driven nozzle, the diameter ratio 1:3.21, was 32% higher than that of 1 : 2.25 and as the inlet velocity gets faster the efficiency decreased. And as the cross section of the driven nozzle increases.

• Journal of ILASS-Korea
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• v.24 no.3
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• pp.137-144
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• 2019

The Y-jet nozzle has benefits such as simple design and wide operating conditions. Because of these benefits, it is used in various combustion devices including industrial boilers. The most important variables in the design of the Y-jet nozzle are the mixing chamber length, the supply diameter of the liquid fuel and gas, and the exit orifice diameter. In addition, because of the use of a twin-fluid, optimized data is required depending on the spray condition. In this study, spray experiment was carried out under the pressure condition of 7 bar or more, which is the spraying condition used in industry. There was no change in flow rate with the length of the Y-jet nozzle mixing chamber, but the difference in SMD was confirmed. Adjusting the exit orifice diameter is most important to achieve the desired flow rate. Changes in the liquid and gas inlet port diameters ratio were found to be help improve the operating range and significant difference in SMD was observed.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.372-375
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• 1999

This paper presents an arc(hot-gas flow field) analysis method in GCB. This method includes the Lorentz's force due to magnetic field, turbulent viscous effect and radiation heat transfer which are indispensable to the analysis of hot-gas flow. To verify the applicability of the Proposed method, steady state hot-Eas flow analysis within a simplified interrupter has been carried out. Inlet boundary pressure values were assumed to be 9.0atm and 12.0atm. For each inlet boundary condition, three cases of hot-gas flow field analyses were performed according to the values of arc currents which were assumed to be D.C 0.6kA. 1.0kA and 2.0kA. The results revealed that the arc radius at nozzle throat has been concentrated by increasing the pressure of nozzle upstream and that the maximum temperature of arc core has been decreased along to nozzle exit and the high temperature lesion come to be wide in nozzle downstream. From these results, it is confirmed that the proposed method will be applicable to predict the large current interruption capability of GCB.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.3
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• pp.209-216
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• 2001

A numerical study is peformed to investigate the effect of circumferential velocity generated by the guide vane on the nozzle flow of a jet fan, s a way of increasing the penetration force of jet fan with nozzle of 175mm diameter. For the validation of numerical results. the velocity is measured by a 5-hole pitot tube and flow visualization is conducted by the tuft method. Under the inlet condition that the maximum circumferential velocity in the stator outlet of the present jet fan is 1.8m/s, the axial velocity in the nozzle outlet has the feature that the velocity at the axis is low and the velocity near the wall high. Therefore, to increase the throw length of the jet fan, the configuration of the fairing and nozzle needs to be developed and the precise revise of the stator angle is required, In addition, the bigger the circumferential velocity, the smaller the axial velocity at the axis and the bigger non-uniformity of the flow distribution.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.57-64
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• 2002

This paper describes the results of a series of experiments executed by using two pilot-scale oxv-fuel burners are designed for maximum capacity of 50,000 kacl/hr, 300,000 kcal/hr and installed in the test furnace. The effects of turn-down ratio, excess oxygen ratio, nozzle exit velocity, injection angle, swirl vane angle and inlet oxygen temperature on the combustion characteristic are investigated. Temperature distributions are measured using R-type and Molybdenum sheathed C-type thermocouple. The results showed that maximum temperature and mean temperature increase with the increase of turn-down ratio and inlet oxygen temperature. The maximum flame temperature was increased about 35% compared to the case of equivalent air operated condition. In addition, Optimum excess oxygen ratio and nozzle characteristics are obtained for this oxy-fuel glass melting furnace.

• Journal of computational fluids engineering
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• v.10 no.4 s.31
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• pp.32-38
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• 2005

Present study simulates oscillatory supersonic impinging jet flows using the axisymmetric Navier-Stokes code. To capture the salient features of flow oscillation and overcome the divergence during the initial transient period, several tests have been conducted for the grid and time step sizes. The results also show that the effects of the inlet flow condition at the nozzle exit and turbulence on the oscillatory behavior of supersonic impinging jets are negligible. Frequencies of the surface pressure oscillation obtained by the selected numerical method are in good accord with the measured impinging tones for various cases of nozzle-to-plate distance. Two seemingly different staging behaviors with nozzle-to-plate distance and nozzle pressure variations are found to correlate well if the frequency and distance are normalized by the length of the first shock cell.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3003-3008
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• 2007

Critical nozzle has been frequently employed to measure the flow rate of various gases, but hydrogen gas, especially being at high-pressure condition, was not nearly dealt with the critical nozzle due to treatment danger. According to a few experimental data obtained recently, it was reported that the discharge coefficient of hydrogen gas through the critical nozzle exceeds unity in a specific range of Reynolds number. No detailed explanation on such an unreasonable value was made, but it was vaguely inferred as real gas effects. For the purpose of practical use of high-pressure hydrogen gas, systematic research is required to clarify the critical nozzle flow of high-pressure hydrogen gas. In the present study, a computational fluid dynamics(CFD) method has been applied to predict the critical nozzle flow of high-pressure hydrogen gas. Redlich-Kwong equation of state that take account for the forces and volume of molecules of hydrogen gas were incorporated into the axisymmetric, compressible Navier-Stokes equations. A fully implicit finite volume scheme was used to numerically solve the governing equations. The computational results were validated with some experimental data available. The results show that the coefficient of discharge coefficient is mainly influenced by the compressibility factor and the specific heat ratio, which appear more remarkable as the inlet total pressure of hydrogen gas increases.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.22-31
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• 2018

In this study, numerical simulations were performed to determine the dynamic characteristics of a pintle nozzle, with changes to the chamber boundary conditions. To apply movement, to the pintle, the nozzle and pintle were created separately by an auto-grid generation program using an overset grid method. The chamber boundary conditions were selected between a constant mass-flow rate condition and a propellant burn-back condition. The pressure and thrust characteristics of the constant mass-flow rate condition were determined by changing the ratio of the mass-flow rate in the inlet. The propellant burn-back condition was considered by formulation of the combustion rate. The burn-back conditions represented nonlinear phenomena, unlike the constant mass flow rate, and a small flow rate resulted in a large change in the chamber pressure.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.15 no.1
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• pp.71-76
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• 2019

Actual stress distributions in the nozzle of a pressure vessel may not be in plane strain condition, implying that the crack-tip constraint condition may be relaxed in the nozzle. In this paper, a methodology for evaluating the fracture toughness of the ASME Code is presented considering the relaxation of the constraint effect in the nozzle of the reactor pressure vessel. The crack-tip constraint effect is quantified by the T-stress. The equation, which represent the relation between the fracture toughness in the lower constraint condition and the plane strain fracture toughness, is derived using the T-stress. This equation is similar to the method for evaluating the fracture toughness of the Master Curve for low constraint conditions. As a result of evaluating the fracture toughness considering the constraint effect in the reactor inlet, outlet and direct injection nozzles using the proposed equation, it was confirmed that the fracture toughness in the nozzles is higher than the plane strain fracture toughness. Applying the proposed evaluation methodology, it is possible to reflect the relaxation of the constraint effect in the nozzles of the reactor pressure vessel, therefore, the safe operation area on the pressure-temperature limit curve can be prevented from being excessively limited.