• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.79-85
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• 2008

Generally Solid Rocket Motor(SRM) has advantages like this - safety, simplicity and flexibility in design and manufacturing process. However, once propellant grain shape and nozzle throat area are determined, modification of thrust magnitude is nearly impossible. Recently, methods for controlling the thrust magnitude of SRM are vigorously developed. This paper predicts internal ballistic performance variation, especially thrust of SRM by means of Linear Approximation according as chamber pressure or nozzle throat area is changed. The results predicted by the proposed method are good agreement with the those of exclusive Ballistic Performance Prediction Program(SPP).

• International Journal of Aeronautical and Space Sciences
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• v.4 no.2
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• pp.51-60
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• 2003

An experimental research program is being undertaken to develop a regeneratively-cooled experimental thrust chamber of liquid rocket engine using liquefied natural gas and liquid oxygen as propellants. Prior to firing test using a regenerative cooling with liquefied natural gas in this program, several firing tests were conducted with water as a coolant. Experimental thrust chambers with a thrust of about 10tf were developed and their firing test facility was built up. Injector used in the thrust chamber was of shear-coaxial type appropriate for propellants of gas and liquid phase and cooling channels are of milled rectangular configuration. Periodical variation of the soot deposition and discoloration was observed through an eyes' inspection on the inner wall of a combustion chamber and a nozzle after each firing test, and an intuitive concept of the periodical variation of mixture ratio near the inner wall of a combustion chamber and a nozzle at once was brought about and analyzed quantitatively. Thermal heat flux to the coolant was calculated and modified with the periodical variation model of mixture ratio, and the increment of coolant temperature at cooling channels was compared with measured one.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.10-20
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• 2019

Recently, fluidic thrust vector control has become a core technique to control multifarious air vehicles, such as supersonic aircraft and modern rockets. Fluidic thrust vector control using the shock vector concept has many advantages for achieving great vectoring performance, such as fast vectoring response, simple structure, and low weight. In this paper, computational fluid dynamics methods are used to study a three-dimensional rectangular supersonic nozzle with a slot injector. To evaluate the reliability and stability of computational methodology, the numerical results were validated with experimental data. The pressure distributions along the upper and lower nozzle walls in the symmetry plane showed an excellent match with the test results. Several numerical simulations were performed based on the shear stress transport(SST) $k-{\omega}$ turbulence model. The effect of the momentum flux ratio was investigated thoroughly, and the performance variations have been clearly illustrated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.671-679
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• 2008

The effect of Pre-cooled Turbojet Engine installation and nozzle exhaust jet on Hypersonic Turbojet EXperimental aircraft(HYTEX aircraft) were investigated by three-dimensional numerical analyses to obtain aerodynamic characteristics of the aircraft during its in-flight condition. First, simulations of wind tunnel experiment using small scale model of the aircraft with and without the rectangular duct reproducing engine was performed at M=5.1 condition in order to validate the calculation code. Here, good agreements with experimental data were obtained regarding centerline wall pressures on the aircraft and aerodynamic coefficients of forces and moments acting on the aircraft. Next, full scale integrated analysis of the aircraft and the engine were conducted for flight Mach numbers of M=5.0, 4.0, 3.5, 3.0, and 2.0. Increasing the angle of attack $\alpha$ of the aircraft in M=5.0 flight increased the mass flow rate of the air captured at the intake due to pre-compression effect of the nose shockwave, also increasing the thrust obtained at the engine plug nozzle. Sufficient thrust for acceleration were obtained at $\alpha=3$ and 5 degrees. Increase of flight Mach number at $\alpha=0$ degrees resulted in decrease of mass flow rate captured at the engine intake, and thus decrease in thrust at the nozzle. The thrust was sufficient for acceleration at M=3.5 and lower cases. Lift force on the aircraft was increased by the integration of engine on the aircraft for all varying angles of attack or flight Mach numbers. However, the slope of lift increase when increasing flight Mach number showed decrease as flight Mach number reach to M=5.0, due to the separation shockwave at the upper surface of the aircraft. Pitch moment of the aircraft was not affected by the installation of the engines for all angles of attack at M=5.0 condition. In low Mach number cases at $\alpha=0$ degrees, installation of the engines increased the pitch moment compared to no engine configuration. Installation of the engines increased the frictional drag on the aircraft, and its percentage to the total drag ranged between 30-50% for varying angle of attack in M=5.0 flight.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.365-369
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• 2007

The solid rocket interacts circumscriptively in terms of is many more than liquid rocket. It is uncontrollable than liquid rocket because all part of combustion is decided such as Mixture ratio of propellant, burning time and area. However, production cost is cheap and because authoritativeness security can be easy and enlarge the early speed that follow thrust-to-weight ratio, it is used comprehensively by small size rocket. Considered about nozzle cooling to control phenomenon that burn by thermal conduction in interior wall of nozzle that follow in thrust increase of solid rocket and erosion phenomenon by combustion gas of high speed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1072-1076
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• 2017

In this paper, a numerical study has been performed to analyze flow characteristics of rocket propulsion. Through the ground spin test, combustion chamber pressure was measured. Based on the experimental results, numerical analysis was conducted under various nozzle pressure ratio conditions such as standard, operating and base pressure conditions. And it was compared with quasi-1D solution and experimental result. In addition, the difference in thrust characteristics according to the spin/non-spin of the flow conditions was confirmed at the same nozzle pressure ratio.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.1
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• pp.34-46
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• 2020

Computational assessment of gas-dynamic characteristics is explored for a three-dimensional counter-flow thrust vector control system in a rectangular supersonic nozzle. This convergent-divergent nozzle is designed by Method of Characteristics and its design Mach number is specially set as 2.5. Performance variations of the counter-flow vector system are illustrated by varying the gap height of the secondary flow duct. Key parameters are quantitatively analyzed, such as static pressure distribution along the centerline of the upper suction collar, deflection angle, secondary mass flow ratio, and resultant thrust coefficient. Additionally, the streamline on the symmetry plane, three-dimensional iso-Mach number surface contour, and three-dimensional turbulent kinetic energy contour are presented to reveal overall flow-field characteristics in detail.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.1-8
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• 1999

In the present paper an attempt has been made to simulate the secondary injection-primary flow interaction in the conical rocket nozzle and to derive the performance of secondary injection thrust vector control(SITVC) system. Complex three-dimensional flowfield induced by the secondary injection is numerically analyzed by solving unsteady three-dimensional Euler equation with Beam and Warming's implicit approximate factorization method. Emphasized in the present study is the effect of secondary injection such as secondary mass flow rates and the momentum of secondary/primary nozzle flow mass rates upon the gross system performance parameters such as thrust ratio, specific impulse ratio and deflection angle. The results obtained in terms of system performance parameters show that lower secondary mass flow rate is advantageous for to reduce secondary specific impulse loss. It is further found that the nozzle with secondary jet injected downstream and interacting with fast primary flow is preferable for efficient and stable SITVC over the wide range of use with the penalty of side specific impulse loss.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.3
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• pp.28-39
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• 2018

In this study, numerical simulations were performed for steady and unsteady state characteristics of length effects on linear pintle nozzles using the overset grid method. Nozzles and pintles are created separately by an auto grid generation program to use the overset grid method. Appropriate turbulent models and numerical methods are selected for the validation of simulations. Pintle shapes are chosen from five types, with differences in the ratio of length and diameter. The longer the pintle length, the greater the thrust and thrust coefficient. The chamber pressure tendency of steady-state and unsteady-state are different for various pintle velocities. The thrust of the nozzle exit responds to changes in the nozzle throat in the unsteady-state, and the speed of pressure propagation wave generated by movement of the pintle is considered to predict the major factor of performance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.428-432
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• 2010

A study on the forming characteristics of outer shell structure for thrust chamber nozzle extension has been performed. In order to identify anisotropy of cold rolled sheet metal, three types of tensile specimens according to the direction to the sheet rolling axis were prepared and tested, and Landford's values were obtained using the results and applied to structural analysis. Forming characteristics of the outer shell structure of the nozzle extension are investigated through manufacturing and forming of the full scale outer shell structures, and strain values obtained by the forming processes are compared to the numerical analysis results. The results obtained by this study will be utilized to design forming tools and processes for manufacturing other outer shell structures which have a bigger expansion area ratio.