• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.919-921
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• 2011

Variable nozzles are used to enhance the effectiveness of aircraft engines at various altitudes. Unsynchronized movements of variable nozzle flaps affect the direction of thrust in case the variable nozzle consists of many flaps. A synchronization test system was developed to verify the synchronization characteristics of variable nozzle mechanism including flaps. The test system has a capability to simulate combustion pressure in variable nozzle space. The test system was used to qualify the synchronization characteristics of a variable nozzle flaps affected by magnitude and uniformity of simulated combustion pressure, and time delay of each nozzle actuators.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.1-5
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• 2006

Birds and insect in nature morph their mean camberline shapes to obtain both lift and thrust simultaneously. Previous unsteady thin airfoil theories were derived mainly for a rigid flapping airfoil. An extended unsteady thin airfoil theory for a deformable airfoil is required to analyze the unsteady two-dimensional aerodynamic characteristics of a biomorphing wing. Theodorsen's approach is extended to calculate the unsteady aerodynamic characteristics of a biomorphing airfoil. The mean camberline of the airfoil is represented as a polynomial. The unsteady aerodynamic characteristics of the morphing airfoil are represented as noncirculatory and circulatory terms. Present theory can be applied to the unsteady aerodynamic analysis of a flapping biomorphing airfoil and the aeroelastic analysis of a morphing wing.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.368-373
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• 2017

Control method for DACS with variable burning area is designed and the performance of the control method is analyzed by doing simulation at various conditions. DACS, which got solid propellant on board, is designed as end-burning type typically. End-burning type DACS has the merit of controlling pressure and thrust, but it discharges the combustion gas which does not using for getting thrust. Therefore, optimal design of propellant grain and burning area changes over time as a result. Variable burning area can be assumed as a disturbance and adaptive control method is useful for pressure control of DACS effected by disturbance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.647-654
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• 2007

A Discrete continuation Method/homotopy approaches are studied for energy/fuel optimal low thrust Earth escape trajectory by solving a two point boundary value problem(TPBVP). Recently, maneuvers using low thrust propulsion system have been identified as emerging technologies. The low thruster is considered as the main actuator for orbit maneuvers. The cost function consists of a energy/fuel consumption function, and constraints are position and velocity vectors at the terminal escape point. Solving the minimum energy/fuel problem directly is not an easy task, so we adopt the homotopy analysis. Using a solution of the minimum energy, which is solved by discrete continuation method, we obtain the solution of the minimum fuel problem.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.6
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• pp.487-495
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• 2018

Experimental analysis of the spray characteristics of the movable sleeve injector, which can simultaneously control the area of the annular gap and the pintle gap, has been studied and a method for controlling the uniform performance over a wide thrust range has been studied. It is confirmed that the design flow rate is not satisfied when the constant pressure difference is set regardless of the opening distance of the sleeve. In order to improve this, the differential pressure in the annular gap and the pintle gap was applied differently according to the opening distance. It was confirmed that the design flow rate was satisfied within the operating range and thrust control was linear from 25% to 100% in linear sleeve area.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.124-131
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• 2019

A design study of gas turbine engine simulation duct was conducted to investigate the operating characteristics and control gain tunning of the Altitude Engine Test Facility(AETF). The simulation duct design involved testing variable spike nozzle and ISO standard choking nozzle to verify the measurements such as mass flow rate and thrust. The simulation duct air flow area was designed to satisfy Ma 0.4 at the aerodynamic interface plane(AIP) at engine design condition. The test conditions for verifying the AETF controls and measurement devices were deduced from 1D analysis and CFD calculation results. The spike-cone driving part was designed to withstand the applied aero-load, and satisfy the axial traversing speed of 10 mm/s at whole operation envelops.

• 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).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.213-217
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• 2011

Unsteady numerical simulations of pintle nozzles were implemented for solid rocket thrust vector control. The variation of pintle location was considered using unsteady numerical techniques, and dynamic characteristics of various pintle models were investigated. In order to consider the variation of the pintle location, a moving mesh method was applied. The effects of shape and location of the pintle nozzle have been analytically investigated. And the results were compared with numerical results. The chamber pressure, mass flow and thrust are analyzed to take account dynamic characteristics of pintle performance.

• Journal of ILASS-Korea
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• v.25 no.3
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• pp.126-131
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• 2020

Throttleable rocket engines are in high demand due to the diversification of space missions. Pintle injector is known to be suitable for throttleable rocket engines, because of its high efficiency in overall thrust zone. In this study, the relationship between spray angle of a throttleable pintle injector and total momentum ratio based on hot fire test conditions was investigated. As a result, the spray angle in 100% and 60% throttling level is higher than the spray angle obtained by the case which considers only propellant mass flow rate, owing to higher total momentum ratio (TMR). The results of this study may be useful for predicting spray angle in hot fire test.

• Journal of ILASS-Korea
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• v.27 no.3
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• pp.144-154
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• 2022

Gas injection is a technique applied to improve throttling in liquid rocket engines and atomization in effervescent injectors. When a gas is injected into a liquid, it creates a two-phase flow inside the injector. The changes (bubbly flow, slug flow, annular flow, etc.) in the two-phase flow affect the injector's spray characteristics. In this study, cold-flow tests were performed by using three injectors with different orifice diameters and four aerators with different gas injection hole diameters. The experiments were done by changing the thrust ratio (liquid mass flow rate ratio) and gas-liquid mass flow rate ratio. Two-phase flow transition, breakup length, and discharge coefficient according to the injector/aerator design and flow conditions were investigated in detail.