• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.54-61
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• 2014

In this study, a plume exhausted from rocket nozzle is investigated by using an unstructured 2-dimensional axisymmetirc DSMC code at various altitude. The small back-pressure to total-pressure ratio($P_b/P_o$) and large $P_b/P_o$ represent low and high altitude condition, respectively. At low altitude, the plume shows a typical complicated structure (e.g. Mach disk) of underexpanded jet while the high altitude plume experiences plain expansion. The various features of exhaust plume is discussed including density, translational/rotational temperature, Mach number and Knudsen number. The results shows that even at 20 km altitude where the freestream Knudsen number is small as $1.5{\times}10^{-5}$, the transitional and rarefied flow regimes can occur locally within the plume. It confirms the necessity of DSMC computation at low altitude.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.9
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• pp.629-641
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• 2019

In order to limit the temperature rise of the structure to a certain level or less while maintaining the aerodynamic shape of solid rocket nozzle by effectively blocking a large amount of heat introduced by the combustion gas of high temperature and high pressure, the heat-resistant materials such as C/C composite having excellent ablation resistance are applied to a position in contact with the combustion gas, and the heat-insulating materials having a low thermal diffusivity are applied to the backside thereof. SiC/SiC composite, which has excellent oxidation resistance, is applied to gas turbine engines and contributes to increase engine performance due to light weight and heat-resistant improvement. Scramjet, flying at hypersonic speed, has been studying the development of C/SiC structures using the endothermic fuel as a coolant because the intake air temperature is very high. In this paper, characteristics, application examples, and development trends of various heat-resistant composites used in solid rocket nozzles, gas turbine engines, and ramjet/scramjet propulsions were discussed.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.126-131
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• 2004

The interaction between the hypersonic free stream and the side jet flow at high altitudes is investigated by direct simulation Monte Carlo(DSMC) method. Since there is a great difference in density between the free stream and the side jet flow, the weighting factor technique which could control the number of simulation particles, is applied to calculate these two flows simultaneously. Chemical reactions are not considered in the calculation. For validation, the corner flow passing between a pair of plates that are perpendicularly attached is solved. The side jet flow is then injected into this comer flow and solution is found for the merged flow. Results are compared with the experiments. For a more realistic rocket model, the flow past a blunted cone cylinder shape is solved. The leeward or windward jet injection is merged with this flow. The effect on the rocket surface is observed at various flow angles. The lambda effect and the wake structure are found like low attitudes. High interaction between the free stream and the side jet flow is observed when the side jet is injected in the windward direction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.12
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• pp.83-91
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• 2005

Air-Launching is an effective method that can launch the 'Nanosat' with low launching cost. In this study, system and subsystem design of the air launching rocket for nanosats which perform a simple mission, have been performed. For this purpose, the WBS of the MIRINAEⅡ, and the subsystem schematics have been defined first. Based on these results, detailed configuration and DMU have been developed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.835-840
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• 2011

The development of a turbopump is fundamental to have an independent LRE(liquid rocket engine) for KSLV-II. Recently, the detail design of a turbopump real-propellant test facility based on liquid oxygen and kerosene has been performed to structure the test facility for the experimental validation of the turbopump. In this paper, the design requirements of the turbopump and the specifications of the test facility was presented and the representative sub-facilities were explained on the basis of the design results. Also, the uncertainty of the sub-facilities which could be appeared during the operation was removed in advance through the simulation method and the experimental verification.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.315-319
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• 2009

Investigation of the lateral force fluctuations in an axisymmetric overexpanded compressed truncated perfect (CTP) nozzle for the shutdown transient is presented. These nozzles experience side-loads during start-up and shut-down operations, because of the flow separation at nozzle walls. Two types of flow separations such as free shock separation (FSS) and restricted shock separation (RSS) shock structure occur. A two-dimensional unsteady numerical simulation has been carried out over an axisymmetric CTP nozzle to simulate the lateral force fluctuations in nozzle during shutdown process. Reynolds Averaged Navier-Stokes equations are numerically solved using a fully implicit finite volume scheme. Governing equations are solved by coupled implicit scheme. Two equation k-$\omega$ SST turbulence model is selected. Unsteady pressure is measured at four locations along the nozzle wall. Present pressure variation compared well with the experimental data. During shutdown transient, separation pattern varies from FSS to RSS and finally returns to FSS. Several pressure peaks are observed during the RSS separation pattern. These pressure peaks generate lateral force or side loads in rocket nozzle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.85-88
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• 2010

This study has been mainly motivated to numerically model the supercritical mixing and combustion processes encountered in the liquid propellant rocket engines. In the present approach, turbulence is represented by the extended $k-{\varepsilon}$ turbulence model. To account for the real fluid effects, the propellant mixture properties are calculated by using SRK (Souve-Redlich-Kwong) equation of state. In order to realistically represent the turbulence-chemistry interaction in the turbulent nonpremixed flames, the flamelet approach based on the real fluid flamelet library has been adopted. Based on numerical results, the detailed discussions are made for the real fluid effects and the precise structure of gaseous methane/liquid oxygen coaxial jet flame.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.2
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• pp.29-37
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• 2015

This paper presents a numerical investigation on detonation of a kerosene-air mixture in the copper tube and the structural response associated with combustion instability in liquid rocket engine. A single step Arrehnius rate law and Johnson-Cook strength model are used to describe the chemical reaction of kerosene-air mixture detonation and the plastic deformation of the copper tube. The changes of flow field and tube stress which are induced by plastic deformation, are investigated on the different tube thicknesses and nozzle configurations.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.419-426
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• 2008

As pulse detonation engine(PDE) does not need compression mechanisms such as compressors because self-sustained detonation waves are able to compress propellant gases by their incident shock waves, the PDE can have a simple straight-tube structure. In this study, we propose an autonomous driving valve system of the PDE, which fill premixed gases into the PDE tubes at high frequency with high mass flow rate. The proposed valve is composed of only three parts: a piston, a cylinder, and a spring. This valve system can produce intermittent flow at high mass flow rate, and also can keep stable reciprocal motion by using the propellant-gas enthalpy. When the cylinder content product is assumed to be constant, experimental results of the mass flow rate were approximately equal to the calculation model. We confirmed the autonomous driving valve performance by experiments, and concluded that this extremely simple valve with no electrical power and controller can be used as the PDE propellant supply system.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.3
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• pp.31-39
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• 2011

The flowfield in a solid rocket motor was simulated at the wall-injection test model, which has a fin-slot grain and submerged nozzle, and visualized by a smoke-wire. The high speed CCD camera captured the visualized images around the nozzle inlet through the grain center port. The vortical tube structure and circumferential flow patterns at the nozzle throat were visualized. The radial momentum transfer caused by the shear-interactions of slot-outlet flow, fin-base flow and grain port flow from upstream worked as the source of these phenomena.