• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.13-24
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• 1989

The geometrical characteristics of sculls which are in use for propulsion of Korean traditional row boats were briefly surveyed. A typical dimension of the scull was selected and prototype for test was prepared. Angular displacements and the force components at handle and pivoting point were measured when the scull was operated in moored condition by skilled fisherman. Time histories and trajectories of motion were analyzed with the force generated at the scull blade. It was found out that the thrust of the scull was generated mainly by reaction force. The direction of improvement for better rowing motion could be also suggested. Continued study on this topic in a self-propulsion condition will provide us another interesting informations and prepare a possibility of application in evaluating rowing motion of oar.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.36-43
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• 2017

The results of a numerical study on the performance of a propeller operating near a free surface are presented in this paper. The simulations are verified through comparison with experimental data, which was performed in a circulating water channel. The propeller performance as a function of the submerged depth was investigated. The effect of the propeller advance ratio on the wave patterns, flow structures around propeller, and thrust and torque of the propeller was also studied. Air ventilation was not observed for low advance coefficients. However, the simulations showed that wave pattern was strongly related to the tip vortex strength and inflow velocity. When air ventilation does not occur, the deduction of propeller thrust and torque increase for high advance coefficients.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.328-341
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• 2017

In the control actuator system of a launch vehicle based on thrust vectoring, the interaction between electro-mechanical position servo and inertial load are combined with the dynamic characteristics of the flexible vehicle support to generate synthetic resonance. This occurred resonance is fed back to the attitude control system and can influence stability of launch vehicle. In this study, we proposed a simulation model to analyze synthetic resonance of electro-mechanical actuation system for thrust vector control and explained the results of simulation and test using dynamic force feedback control which improves dynamic characteristics of servo actuation system by reducing synthetic resonance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.10
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• pp.791-797
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• 2018

In this work, the high-altitude environment simulation study was carried out at an altitude of 65 km exceeding Mach number of 6 after the launch of Korean Space Launch Vehicle using a shock tunnel. To minimize the flow disturbance due to the strut support of test model as much as possible, a few different types of strut configurations were considered. Using the configuration with minimum disturbance, the high-altitude environment simulation experiment including a propulsion system with a single-plume, was conducted. From the thruster test through flow visualization, not only a shockwave pattern, but a general flow-field pattern from the mutual interaction between the exhaust plume and the free-stream undisturbed flow, was experimentally observed. The comparison with the computation fluid dynamic(CFD) results, showed a good agreement in the forebody whereas in the afterbody and the nozzle the disagreement was about ${\pm}7%$ due to unwanted shockwave formation emanated from the nozzle-exit.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.26-34
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• 2018

Structural static test and the performance test were conducted to determine whether the propeller developed for a multi-copter with the take-off weight of 25 kg satisfies the design requirement. The result of the structural test revealed that the propeller had a safety margin of 3 or more as the ultimate load and requirement load did not cause the specimen breakage. In the performance test, the propeller generated the hover thrust and maximum thrust of design requirement, and hover efficiency in the operating thrust range was greater than 0.73. Maximum hover efficiency increased by more than 3% compared to the reference propeller and electric power consumption decreased by more than 4% in the operating range. The propeller was found to be successfully developed based on the satisfaction rate of the structural strength requirement and the performance requirement.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.9
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• pp.799-804
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• 2007

The behavior of spray emanating from an injector to be employed in a liquid-propellant thrust chamber is investigated by optical measurement techniques. The injector has eight holes, each of which has 30 cant angle from the center-axis with the diameter of 0.406 mm. In order to examine an atomization process according to the spray-generation conditions and the evolution along spray downstream, variational features in the velocity and size of droplets obtained through Dual-mode Phase Doppler An 799emometry (DPDA) are delineated and discussed together with instantaneous plane images captured by using Nd:Yag laser sheet beam. A categorization of spray-flow regime representing the atomization and turbulent nature is made through evaluating the non-dimensional parameters, i.e., Reynolds number and Weber number based upon the theoretical injection velocity. These qualitative and quantitative data of spray breakup will be a firm basis for the design of brand-new thruster

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.29-37
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• 2018

This paper reports the preliminary firing test performed with an ADN-based monopropellant using a 5 N scale thruster. ADN-based propellant and catalyst was fabricated and catalytic combustion of propellant was characterized by DSC-TG analysis. Although an explosion in the catalyst bed was occurred, high temperature in the catalyst bed obtained and demonstrated catalytic combustion of the propellant. Preliminary test results motivates the research for catalysts with better thermal stability.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.4
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• pp.264-272
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• 2011

Shipbuilders carry out the operation test to check the conditions of the main propulsion system and auxiliaries for moored vessel in the quoy before the sea trial. The estimation of the thrust and torque for the partially submerged propeller should be prepared to ensure the safety of mooring line and the ship. In this paper, the variations of the thrust and torque according to the shaft submergence and the propeller rotating speed in bollard pull condition are investigated with the model test and the numerical analysis. Based on these resaearch, the empirical formula representing the physical phenomena of the partially submerged propeller is derived and validated through comparison to measurement results of full-scale propellers under the quoy operation test.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.139-145
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• 2006

LRE(Liquid propellant Rocket Engine) is one of the important parts to control the trajectory and dynamics of rocket. The purpose of control of LRE is to control the thrust according to requiredthrust profile and control the mixture ratio of propellants fed into gas generator and combustor for constant mixture ratio. It is not easy to control thrust and mixture ratio of propellants since there are co-interferences among the components of LRE. In this study, the dynamic model of LRE was constructed and the dynamic characteristics were analyzed with control system as PID control and PID+Q-ILC(Iterative Learning Control with Quadratic Criterion) control. From the analysis, it could be observed that PID+Q-ILC control logic is more useful than standard PID control system for control of LRE.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.12
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• pp.986-993
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• 2018

Lateral thrust jet has better maneuverability performance than the control surface like the conventional fin for attitude control or orbital transition of guided weapons. However, in the supersonic region, a jet interaction flow occurs due to the lateral thrust jet during flight, and a complicated flow structure is exhibited by the interaction of the shock wave, boundary layer flow, and the vortex flow. Especially, hit-to-kill interceptors require precise control and maneuvering, so it is necessary to analyze the effect of jet interaction flow. Conventional jet interaction analyses were performed under low altitude conditions, but there are not many cases in the case of medium altitude condition, which has different flow characteristics. In this study, jet interaction flow analysis is performed on the lateral jet controlled interceptor operating at medium altitude. Based on the results, the structural characteristics of the flow field and the changes of aerodynamic coefficient are analyzed.