• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.3
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• pp.43-53
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• 2022

In this study, analysis of the flow characteristics of pintle-controlled nozzle with split-line TVC system and the thrust performance prediction was performed. The numerical computation was verified by comparing the thrust coefficient derived from the analysis results with the experimental data. By applying the same numerical analysis technique, the flow characteristics of nozzle were confirmed according to operating altitude, pintle stroke position and TVC angle with the 1/10 scale. As the TVC angle increased, thrust loss occurred and the tendency of AF was different depending on the position of the pintle stroke. Based on the analysis results, the relation of thrust coefficient was derived by applying the response surface methods. The thrust performance model with a slight difference of 1.2% on average from the analysis result was generated.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.132.1-132
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• 2001

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.934-939
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• 2005

Starting pressure of a supersonic ejector with a second-throat was investigated. In case of mixing chamber length longer than a critical length, starting pressure is in proportion to length of the mixing chamber. In this study, we assumed that the ejector starts when the primary supersonic flow reaches inlet of the second-throat and the distance of the supersonic flow traveling can be expressed by multiplying an empirical factor to the first diamond shock length of overexpanded flow. To calculate the overexpanded supersonic flow, a mixing model was employed to compute secondary flow pressure and the result was applied to back pressure condition of overexpanded flow calculation. In the result, for three cases of primary nozzle area ratio, we could get accurate model of predicting the starting pressure by selecting a suitable empirical factors around 3.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.9
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• pp.581-589
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• 2008

The pulverized coal combustion behavior in the utility boiler is very complex since so many physical and chemical processes happen in it, simultaneously. The mixing of pulverized coal with combustion air plays an important role in achieving the efficient combustion and stable boiler operation. The distribution of combustion air supplied to the furnace through the windbox damper system has not been clearly known since the individual measurements of air flow for each air nozzle were not possible, yet. The present study describes the CFD modelling of windbox damper system and aims to obtain the air flow rates and pressure loss coefficients across the present five damper systems, respectively. The one dimensional flow network model has been also established to get air flow distributions across the windbox damper, and applied to the actual plant operation condition. Compared with the designed air flow distribution, the modelled one gives a reasonable agreement. For the actual plant operation, the predicted air flow distribution at each air nozzle is differed with the designed data and strongly affected by the individual opening angle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.5
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• pp.476-482
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• 2009

The effect of pintle shape on the thrust level of pintle-nozzle Solid Rocket Motor(PNSRM) was studied numerically using the Spalart-Allmaras turbulent model of Fluent. Mass flow rate of PNSRM was always less than theoretical value and the extent of decrease in mass flow rate grew in the large pintle because of increase in the relative boundary layer thickness between pintle body and nozzle wall. The bigger pintle size was, the more thrust of pintle tip pressure was obtained. Meanwhile the more thrust of nozzle and chamber pressure decreased. Hence, total thrust of big pintle was less than a small pintle under same throat area condition. Specific impulse was relatively flat for all pintle shape.

• Journal of the Korean Society of Combustion
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• v.3 no.2
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• pp.13-27
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• 1998

The optimization of frontal device including fuel nozzle and swirler is required to secure the mixing of fuel and air and the combustion stability leading the reduction of pollutant emissions and the increase of combustion efficiency in gas turbine combustor. The effects of injection nozzle and swirler on the flow field, spray characteristics and consequently the combustion stability, were experimentally investigated by measuring the velocity field, droplet sizes of fuel spray, lean combustion limit and the temperature field in the main combustion region. Flow fields and spray characteristics were measured with APV(Adaptive Phase Doppler Velocimetry) under atmospheric condition using kerosine fuel. Temperatures were measured by Pt-Pt13%Rh, R-type thermocouple which was 0.2mm thick. Spray and flame was visualized by ICCD(Intensified Charge Coupled Device) camera. It was found that the dual swirler resulted in the biggest recirculation zone with the highest reverse flow velocity at the central region, which lead the most stable combustion. The various combustion characteristics were observed as a function of the geometries of injector and swirler, that gave a tip for the better design of gas turbine combustor.

• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.30-35
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• 2014

This study has been conducted to develop an ejector system applied in the aircraft engine-bay ventilation system. Tandem-Ejector was selected as a component of ventilation system because it could achieve high ventilation performance in spite of motive flow with small flow rate. Tandem-Ejector is composed of a primary nozzle and two mixing ducts ($1^{st}$ mixing duct and $2^{nd}$ mixing duct). In this study, 1-D Tandem-Ejector model has been built with conservation laws and isentropic relation for 1-D ejector sizing and performance prediction. Computational Fluid Dynamics(CFD) has been conducted to investigate ejector performance and flow characteristics in the ejector. Also, Tandem-Ejector performance tests have been conducted to obtain ejector pumping performance and to investigate stand-off (gap between primary nozzle and $1^{st}$ mixing duct inlet) effect on ejector pumping performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.1
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• pp.73-81
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• 1997

Numerical analysis on turbulent flow and heat transfer in the rocket nozzle has been studied using the mass-weighted-averaged full Navier-Stokes equations, the Morkovin hypothesis on turbulent flow, the $\textsc{k}$-$\varepsilon$ turbulence model with the wall function specially designed to be able to consider the effects of pressure gradients, heat transfer and compressibility, and the numerical scheme of Karki. The present results are in good agreement with the experiments of Back et al.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.31-36
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• 2001

The velocity and temperature profiles in the cabin of the automobile affect greatly to the comfort of the passenger. In this paper, the three dimensional flow and temperature analysis in the cabin of the automobile which is geometrically complicated was performed to investigate and predict the velocity and temperature profile. The three dimensional Navier-Stokes code used in this case was validated by performing of a 1/5 experimental scale model vehicle flow anal)rsis successfully. The temperature field of cavity was analyzed for Energy-equation code validation. The comparison of the results are made with the polished computational data and give a coincided one.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2798-2803
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• 2008

The confined slot air jet impinging normally on a moving flat surface has been investigated numerically by using commercial CFD code Ansys CFX-V11. Turbulent flows are modeled using k-w turbulence model. Two-dimensional turbulent flow is considered. Calculations were conducted for a nozzle-to-plate spacing of eight slot nozzle width, at three Reynolds number(Re=4500, 6700 and 10,000) and four surface-to-velocity ratios i.e. 0, 0.25, 0.5 and 1. Results are compared against corresponding cases for heat transfer from a stationary plate. Local Nusselt number is calculated under constant wall temperature condition. The analysis reveals that the average Nusselt number increases considerably with the jet exit Reynolds number, but decrease with the plate velocity.