• Proceedings of the KSME Conference
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• 2001.06e
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• pp.282-287
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• 2001

The CSCM Upwind method and Material Transport Analysis (MTA) have been used to predict the thermal response and ablation rate for non-charring material to be used as thermal protection material (TPM) in KSR-III test rocket nozzle. The thermal boundary conditions such as cold wall heat-transfer rate and recovery enthalpy for MTA code are obtained from the upwind Navier-Stokes solution procedure. The heat transfer rate and temperature variations at rocket nozzle wall were studied with shape change of the nozzle surface as time goes by. The surface recession was severely occurred at nozzle throat and this affected nozzle performance such as thrust coefficient substantially.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.100-105
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• 2002

This paper predicts the material properties of spatially reinforced composites (SRC) and analyzes the thermo-elastic behavior of a kick motor nozzle manufactured from that material. To find the appropriate SRC structure for the nozzle throat that satisfies given design conditions, the equivalent material properties of the SRC are predicted using the superposition method for those of rod and matrix. Studied are the elastic behavior, temperature distribution, and thermo-elastic behavior of a kick motor nozzle composed of carbon/carbon SRC as a throat part. The elastic deformation of the nozzle composed of 3D carbon/carbon SRC shows asymmetry in a circumferential direction. However, 4D carbon/carbon SRC nozzle shows uniform deformation in the circumferential direction. Stress concentration in connecting parts of the kick motor nozzle is ultimately high due to the high temperature gradient in each connecting part. The thermo-elastic deformations of both the 3D and the 4D SRC nozzles are uniform in the circumferential direction due to the isotropy of CTE of each SRC. The deformation of the 3D SRC nozzle is a slightly smaller than that of the 4D SRC nozzle in the nozzle throat, which is favorably effective on rocket thrust. The circumferential stress is the most critical component of the kick motor nozzle. The 4D SRC nozzle having 1,1,1,1.7 diameters in each direction has the smallest circumferential stress among several SRC nozzles.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.54-59
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• 2000

A numerical study of axisymmetric rocket main nozzle flow has been accomplished. The CSCM upwind flux difference splitting method with an iterative time marching scheme having second order accuracy in time and space has been used to simulate unsteady flow characteristics in an axisymmetric rocket main nozzle. Though the pressure vary at nozzle inlet with the lapse of time, Mach No. and the density were not changed significontly compared with the temperature. Specific heat ratio $\gamma$=1.134 predicted higher temperature at nozzle throat and exit and nondimensional thrust coefficients at exit than specific heat ratio $\gamma$=1.4 did.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.316-319
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• 2008

A computational analysis has been conducted on the compressible flow in the turbine exhaust nozzle of the gas generator cycle liquid rocket engine. The commercial CFD code Fluent has been used. Four nozzle designs have been compared to select the turbine exhaust nozzle concept. Three candidates with single nozzle have comparable performance. The model with bifurcated nozzles shows significant performance loss. However it will be better in the view of balanced thrust distribution because of its symmetric geometry.

• Journal of Aerospace System Engineering
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• v.14 no.4
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• pp.1-9
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• 2020

The characteristics of an aerospike pintle nozzle system with excellent altitude compensation were analyzed using cold air testing. It was confirmed that reducing the stroke of the aerospike nozzle is effective in increasing the thrust. However, the results of additional numerical analysis indicated that the discharge coefficient factor was significantly lower at the maximum stroke. The Vena contracta due to the cowl reduction angle decreased the effective nozzle throat area at the maximum stroke and hindered expansion. Complementing the cowl design may thus increase the efficiency of a solid-propellant rocket engine that uses the aerospike pintle nozzle system.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.87-95
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• 2016

A study on the effect of altitude-compensation and the possibility of throttling is performed by designing an E-D nozzle that is a type of altitude-compensation nozzles. In order to examine the effect of the altitude-compensation, a CFD analysis is conducted by using three kinds (sea level, altitude at 10 km and 16 km) of the atmosphere condition while maintaining the chamber pressure. Results show that the effective nozzle exit area is also gradually increased when the altitude get increased. Understanding the possibility of throttling, a CFD analysis is conducted by moving the location of the pintle. Just as same as a general pintle thruster, the chamber pressure and thrust are increased when the nozzle throat area get decreased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.644-648
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• 2004

In the present study were examined numerically and experimentally the off-design performance characteristics on an axisymmetric plug nozzle with variable throat area. In this nozzle concept, its throat area can be changed by translating the plug into the axial direction. First, a mixed-expansion plug nozzle, in which two expansion parts are arranged both inside and outside, was designed by means of the method of characteristics. Second, the CFD analysis was verified by the cold-flow wind tunnel test. Third, its performance characteristics were evaluated over a wide range of pressure ratio from half to double throat area through the design point, using the CFD code verified by the wind tunnel tests. It was made clear from the study that not so critical thrust efficiency losses were found and the maximum thrust efficiency loss was at most approximately 5 % under off-design conditions without external flow. This result shows that a plug nozzle can give the altitude compensation even under off-design geometry operations. However, shock waves were observed in the inner expansion part under the doubled throat area operation and thus some thermal problems may be caused on the plug surface. Furthermore, collapse of cell structure on the plug surface was observed with external flow (around Mach number 2.0) as it became lower pressure ratio below the design point and the fact may result in big efficiency loss regardless of geometrical configuration.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.689-698
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• 2021

The development of modern warfare detection technology is increasingly threatening the survivability of aircraft. Among them, IR-seeking missiles greatly affect the survivability of aircraft and are a main factor that reduces the success rate of aircraft missions. In order to increase aircraft survivability, studies on shape-modifying nozzles with added curvature are being actively conducted. In this study, we selected a double serpentine nozzle among shape-modifying nozzles to increase aircraft survivability. We then investigated the effects of the location of the maximum area change rate of the nozzle. It was confirmed that the location of the change rate of area affects the thrust and exit temperature of the nozzle. In addition, it was shown that the thrust penalty was reduced as the position of the change rate of the maximum area was located at the rear of the nozzle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.45-48
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• 2007

Conventional force sensors such as piezoelectric sensor has limitations for measuring micro/nano-scale thrust. In this study we developed nano-scale measurement system using laser displacement sensor and cantilever. And electrospray microthruster was fabricated by using stainless capillary and extraction electrode, to generate nano-scale thrust. The measurement system can measure the around 90 nN thrust from this thruster. In addition, we designed and fabricated electrospray micro thruster based on PMMA(Polymethyl methacrylate), which has a nozzle protruded from the substrate.

• International Journal of Fluid Machinery and Systems
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• v.9 no.4
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• pp.354-361
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• 2016

This study aims to identify aerodynamic characteristics of the ramp tab, a mechanical deflector, by conducting a non-combustive experiment using compressed air and supersonic flow test equipment. With the ramp tabs installed symmetrically and asymmetrically on the outlet of the supersonic nozzle, the structure of the flow field, the thrust spoilage, the thrust deviation angle, and the lift/drag coefficients were derived and analyzed. The results show that the asymmetrically-installed ramp tabs are advantageous relative to the symmetrically-installed tabs in terms of the performance of thrust vector control, thrust deviation angle, and lift coefficient.