• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.138-145
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• 2004

Experimental study was conducted on cylindrical supersonic diffuser in order to investigate the effects of the ratios of diffuser area to nozzle throat area (Ad/At), diffuser area to nozzle exit area (Ad/Ae), nozzle exit area to its throat area (Ae/At), and diffuser length to its diameter (L/D), the free volume of vacuum chamber, and the relative distance between nozzle exit and diffuser inlet on the diffuser performance. The study showed that the minimum diffuser starting pressure (Po/Pa)st increased monotonically with increase in (Ad/At) as predicted by the normal shock and momentum theory models and the volume of vacuum chamber affected vacuum pressure level during diffuser operation at lower value of (Ad/Ae). The results of this investigation will be utilized in the design of real-scale high-altitude simulation test facility.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.5
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• pp.11-23
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• 2022

For the design of the shortened ED(Expansion Deflection) nozzle, a numerical study of ED nozzle was performed according to the length reduction methods. The first method is to reduce the extension length of the ED nozzle with 80% bell nozzle length by 10%, 20% and 30%. The second method is to shorten the extension length by increasing the nozzle throat angle. Due to the increase in the curvature of the contour as the length shortened, the decrease in the nozzle exit velocity between the ED nozzle with 80% bell nozzle length and the ED nozzle in the first method was reduced, and the thrust become similar. The ED nozzle of the second method increased the thrust by increasing the nozzle exit velocity compared to the ED nozzle with 80% bell nozzle length.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.40-45
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• 2005

Techniques used for throcket motors are mainly classified as fixed nozzles with mechanical exhaust jet interferences on the expansion region (such as jet tabs and jet vanes) and movable nozzles(such as ball&socket md flexible seal). Using the numerical analysis and the cold-flow test, this paper evaluates the performance of supersonic nozzle for asymmetric entrance shape at tilted position of ball&socket nozzle. Numerical results show that the asymmetric effects in the flow fields are gradually diminished up to the nozzle throat and are not noticeable downstream of the nozzle throat. Although the calculated thrust and the lateral force are less than those of cold-flow test, two results show a flirty good agreement.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.123-128
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• 2012

According to the sequence of pintle operation, the performance characteristics of pintle nozzles are analyzed. The pintle movement was simulated using unsteady numerical techniques, the response lag and sensitivity at the chamber and nozzle are estimated for movable pintle. Three operation sequences of the pintle are considered for evaluating whether the rate of the chamber pressure increase and the operation sequence will have any significant impact towards the rocket performance. Three operation sequencies are as following; the pintle moves toward the nozzle throat, it turns instantly (case 1), stops at the nozzle throat for some time(0.5sec) (case 2), and stops at the nozzle throat (case 3). As a result, the dynamic characteristics according to the operation sequence and pintle shape were analyzed to take account the rocket performance.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.2
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• pp.7-14
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• 2003

Computational work using the axisymmetric, compressible, Navier-Stokes Equations is carried out to predict the discharge coefficient of mass flow through a micro-critical nozzle. Several kinds of turbulence models and wall functions are employed to validate the computational predictions. The computed results are compared with the previous experimented ones. The present computations predict the experimental discharge coefficients with a reasonable accuracy. It is found that the standard $\kappa$-$\varepsilon$turbulence model with the standard wall function gives a best prediction of the discharge coefficients. The displacement thickness of the nozzle wall boundary layer is evaluated at the nozzle throat and is well compared to a prediction obtained by an empirical equation. The resulting displacement thickness of the wall boundary layer is about 2% to 0.6% of the diameter of the nozzle throat for the Reynolds numbers of 2000 to 20000.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.392-396
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• 2012

Experimental and computational study for steady-state pintle driven nozzle throat flow are carried out by changing four pintle shape. Results show that thruster performance is influenced by pintle shape greatly. This attributes to the distorted throat area and chamber pressure change as the pintle shape and its penetration.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.8-15
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• 2014

The ablation characteristics of graphite nozzle throat insert is analyzed for the use in solid rocket propulsion system. The propulsion system is composed of three types of conventional nozzles, such as De-Laval type, blast tube type, and submerged type. Various kinds of propellants are used in the thirteen kinds of propulsion system that has different shapes of each other. Total thirty seven tests are performed. From the results of the analysis, it is found that the ablation rate is higher for the higher average chamber pressure and the higher concentration of oxidizing species in combustion gas.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.44-53
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• 2006

In this study, the non-destructive computed tomography was adopted to observe the density profile of the needle-punched Carbon/Carbon(C/C) composites nozzle throat. The density profile of C/C was evaluated within ${\pm}0.01g/cm^3$ with 98.74% confidence when the correction of the image and high signal-to-noise ratio were achieved by the optimization of the beam hardening, the electrical noise and the scattered X-ray. The density variation of C/C with the computed tomography was in good agreement with the results obtained by the water immersion method and the observation with scanning electron microscope.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.275-278
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• 2010

By changing the nozzle throat area during the operation, thrust of a pintle thruster can be adjusted easily such as a liquid propulsion. In this paper, numerical analysis was carried out for SNECMA's pintle thruster with different pintle shapes. Flow field and aerodynamic load changed drastically with pintle shapes. Bore in the pintle decreased aerodynamic load significantly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.697-709
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• 1996

Supersonic axisymmetric jets issuing from various kinds of nozzles with a throat diameter of a few millimeters were experimentally investigated. The exit Mach number and Reynolds number based on the throat diameter of nozzle were in the range of 1.0 ~ 5.9 and 8.4$\times$ $10^4$ ~ 2.9$\times$$10^6$, respectively. The nozzle pressure ratio was varied from 5 to 85. Present paper aims to offer fundamental information of the supersonic free-jets, with an emphasis to give data with which the shape of the free-jets can be depicted under a specified condition. Experimental data are summarized to enable an estimation of the shape of the supersonic free-jets. The result shows that the shape of free-jets is dependent on only the nozzle pressure ratio.