• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.76-84
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• 2018

In this paper, the numerical analysis for heat conduction of silica/phenolic composite material, used for solid rocket nozzle liners or insulators, is conducted. A 1-dimensional finite difference method for the analysis of silica/phenolic during the firing of a solid rocket motor is used to calculate heat conduction, considering surface ablation and thermal decomposition. The boundary condition at the nozzle wall, considering the convective heat transfer, is obtained via integration equations. The numerical results of the surface ablation and char depth are compared with the results of a TPEM-10 test motor, finding that the result of calculation agrees with the thermal response of the test motor.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.26-36
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• 2007

The thermal response characteristics of nozzle liner for a solid rocket motor applying highly aluminized PCP or HTPB propellant with slotted tube grain have been investigated. The SEM photographs of aluminum oxide particles taken from nozzle liner show that the PCP propellant with the finer and less contents of oxidizer can offer greater possibility for increasing aluminum agglomeration than the HTPB propellant. The PCP propellant shows locally greater mechanical erosion at 4 circumferential areas of the nozzle entrance in line with grain slot due to the impingement of large particles, but the HTPB propellant shows greater thermochemical ablation at the nozzle blast tube, the throat insert and the exit cone because of relatively much more mole fraction of $H_2O\;and\;CO_2$ in combustion gases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.536-542
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• 2017

A great deal of difficulty is encountered in the thermo-mechanical analyses of nozzle assembly for solid propellant rocket motors. The main issue in this paper is the modeling of the boundary conditions and the connections between the various components-gaps, relative movements of the components, contacts, friction, etc. This paper evaluated the complex phenomena of nozzle assembly during burning time with co-simulation which include fluid, thermal surface reaction/ablation and structural analysis. The validity of this approach was verified by comparison of analysis results with measured strains.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.24-30
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• 2013

To guarantee the exact control of missile warhead, it is inevitable to ensure the stabilities in the view points of structural and fluid/thermo dynamics of the rocket motor. Specially, despite of shortness in operating time of the rocket motor which is initial turning type of missile, it occurs frequently some problems of ablation at the neighborhood of the nozzle throat, with the result that the system itself gets to failure. In these connections, in the present study, the effect of the operating time of a rocket motor on the coefficient of convective heat transfer at the nozzle wall is investigated by numerical analysis. As a result, it is turned out that the heat transfer coefficient is largest at the just ahead of nozzle throat and decreases with the increase of operating time of the rocket motor. Furthermore, we found that the radius of curvature of throat becomes smaller, the maximum coefficient of convective heat transfer becomes larger.

• The KSFM Journal of Fluid Machinery
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• v.11 no.4
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• pp.7-13
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• 2008

The computational investigation is performed to find out the interaction of arc plasmas with surrounding materials and the thermal flow characteristics in a PASB (Puffer-Assisted Self-Blast) chamber, which is one of new breaking concepts in $SF_6$ switchgears. It is very important to define the flow and mass transfer happened during the full arcing history for further understanding complex physics inside the chamber. In this study, we have considered two diffusion processes by the hot arc plasma, one is PTFE nozzle ablation and the other is Cu electrode evaporation, simultaneously. It was found that the principle of the pressure-rise inside the chamber is confirmed by the computational results and the increase of the electrical conductivity of the residual gas near current zero is critical to the chamber design.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.54-58
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• 2003

Jet vane is an useful component which is installed at the end of a nozzle for the purpose of the posture control and the secure controlling stability during the initial launching of a rocket. Small space for installation and rapid response are considered as its merits but it is ablated thermally and mechanically by the combusted gas having high velocity and temperature produced in a combustion chamber. En this study, as the fundamental study for the ablation analysis of jet vane, the heat transfer into a jet vane which is located in the supersonic flow field.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.2
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• pp.119-125
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• 2017

Ablative material in a rocket nozzle is exposed to high temperature combustion gas, thus undergoes complicated thermal/chemical change in terms of chemical destruction of surface and thermal decomposition of inner material. Therefore, method for conjugate analysis of thermal response inside carbon/phenolic material including rocket nozzle flow, surface chemical reaction and thermal decomposition is developed in this research. CFD is used to simulate flow field inside nozzle and conduction in the ablative material. A change in material density and a heat absorption caused by the thermal decomposition is considered in solid energy equation. And algebraic equation under boundary layer assumption is used to deduce reaction rate on the surface and resulting destruction of the surface. In order to test the developed method, small rocket nozzle is solved numerically. Although the ablation of nozzle throat is deduced to be higher than the experiment, shape change and temperature distribution inside material is well predicted. Error in temperature with experimental results in rapid heating region is found to be within 100 K.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.622-624
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• 2002

This paper describes a method for steady state hot gas flow analysis considering nozzle ablation for the nozzle of $SF_6$ gas circuit breaker. In order to take account of the effect of ablated nozzle material on the hot gas flow. the PTFE mass concentration equation is added to the established equations for hot gas flow analysis. The steady state simulations were carried out under the condition of DC current flows and the results are presented.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.695-698
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• 2008

Self-blast circuit breakers utilize the energy dissipated by the arc itself to create the required conditions for arc quenching during the current zero. During the arcing period, high pressure, temperature and radiation of the arc could burn in pure SF6 gas and PTFE nozzle. Ablated nozzle shape and $SF_6$-PTFE mixture vapor affect the performance of an self-blast circuit breaker. After a number of tests, nozzle in circuit breaker is disassembled, a section of ablated nozzle is investigated precisely. Using computational fluid dynamics, the conservation equation for the gas and temperature, velocity and electric fields within breaker is solved. Before applying a section model, developed program is verified with experimental data. Performance of ablated nozzle shape is compared with original model through analysis program.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.36-43
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• 2018

A great deal of difficulty is encountered in the thermo-mechanical analyses of nozzle assemblies for solid propellant rocket motors. The main issue in this paper is the modeling of the boundary conditions and the connections between the various components-gaps, relative movements of the components, contacts, friction, etc. This paper evaluates the complex phenomena of nozzle assemblies during burning time with co-simulations that include fluid, thermal surface reaction/ablation, and structural analysis. The validity of this approach is verified via comparison of analysis results with measured strains.