• 대한기계학회논문집B
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• 제31권10호
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• pp.884-888
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• 2007

It is necessary to evaluate periodically the performance of the AOV(air-operated valve) which is used for controlling flow and pressure in nuclear power plant. The required thrust for actuating valve and available thrust of actuator are calculated with conditions of flow through a valve in this study and operating performance is analyzed through comparing two thrusts. In general, differential pressure is increased according to increase the flow rate and differential pressure affects the required thrust of valve. We found the fact that it is possible not to close the valve perfectly because required thrust becomes bigger than available thrust of actuator.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.395-398
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• 2006

this paper provides a novel method to start the linear engine coupled linear generator from dead stop to its final steady state operation. This method depends mainly to use the linear generator mounted on the shaft of the linear engine to provide the required thrust force to move and oscillate the linear engine from bottom to top dead centers. It is a cost effective approach to start the internal linear combustion engine using its coupled tubular permanent magnet linear generator proposed here. This linear generator operates in this case in motoring mode, providing the required thrust force by feeding this linear generator phases with currents by using a three phase PWM inverter controlled by position feedback scheme. In order to provide the desired thrust force with specific value and direction, a position feedback is required to control the free piston engine motion through controlling the inverter switches using PWM control scheme.

• 한국군사과학기술학회지
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• 제14권6호
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• pp.1067-1072
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• 2011

If the flow of booster gas which is exhausted to the rear part of a canister is properly restricted in the canister of a hot-launch system, the resultant pressure built up in the canister provides additional force to accelerate the missile to a required launch velocity. These thrust augmentation performances can be controlled through the configuration design of baseplate orifices. In this paper, the simple technique to analyze the thrust augmentation performances of baseplate orifices is suggested and the thrust augmentation characteristics by its various configurations are compared. According to the initial displacement of a missile, the inner pressure of a canister is measured from scaled cold flow tests, and the discharge coefficient of baseplate orifices is calculated. Then the thrust augmentation in a canister is simulated by applying these discharge characteristics to the AMESIM software for launch dynamics.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.209-212
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• 2006

Insect and birds in nature flap their wings to generate fluid dynamic forces that are required for the locomotion. Most of the previous published papers discussed mainly on the effect of flapping parameters such as flapping frequency and amplitude on the thrust at a fixed Reynolds number. However, it is not much known on the values of the flapping parameters that the flapping wing requires to generate the thrust at the low Reynolds number flow. In this paper, the onset of the thrust generation is investigated using the lattice Boltzmann method. The wake patterns and velocity profiles behind a flat plate in heaving oscillation are investigated for the heaving amplitude of 0.5C. The time-averaged thrust coefficient value is investigated by changing the reduced frequency from 0.125 to 3.0 for three values of heaving amplitude (h/C=0.25, 0.325, 0.50). It is also found that the critical Strouhal number over which the flat plate starts to produce the thrust is around 0.1 and the thrust is an exponential function of the Strouhal number.

• 한국해양공학회지
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• 제23권4호
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• pp.47-51
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• 2009

Thrust is one of the important performance characteristics of an AUV. At the design stage, the resistance of an AUV at its maximum speed is estimated and then the thrust system is designed, including the propeller diameter, propeller rpm, driving system, and required power. However, it is not possible to be certain that the thrust system has been correctly designed until the AUV is launched and its speed is measured. If data from a propeller open-water test is available, the thrust and torque of the propeller at a certain speed can be estimated. In addition, if the motor's torque characteristics are available, the maximum speed saturated by the induced propeller torque can be estimated. In this paper, an easy technique for estimating the maximum speed of an AUV will be shown, even in a case where additional resistance is gained from appendages not considered at the design stage. Furthermore, the thrust performance changes by adjusting the diameter of the propeller can be easily investigated.

• International Journal of Precision Engineering and Manufacturing
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• 제9권1호
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• pp.19-24
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• 2008

We propose a new miniature air-bearing stage with a moving-magnet slotless linear motor. This stage was developed to achieve the precise positioning required for submicron-level machining and miniaturization by introducing air bearings and a linear motor sufficient for mesoscale precision machine tools. The linear motor contained two permanent magnets and was designed to generate a preload force for the vertical air bearings and a thrust force for the stage movement. The characteristics of the air bearings, which used porous pads, were analyzed with numerical methods, and a magnetic circuit model was derived for the linear motor to calculate the required preload and thrust forces. A prototype of a single-axis miniature stage with dimensions of $120\;(W)\;{\times}\;120\;(L)\;{\times}\;50\;(H)\;mm$ was designed and fabricated, and its performance was examined, including its vertical stiffness, load capacity, thrust force, and positioning resolution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1143-1148
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• 2007

LRE(Liquid propellant Rocket Engine) is one of the important parts to control the motion of rocket. For operation of rocket in error boundary of the set-up trajectory, it is necessarily to control the thrust of LRE according to the required thrust profile and control the mixture ratio of propellants fed into combustor for the 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.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.237-240
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• 2011

본 연구에서는 핀틀 형상의 변곡점 존재 유 무가 SNECMA 노즐목 가변 추력기의 성능에 어떤 영향을 미치는지 알아보기 위해 수치해석을 수행하였다. 그 결과 변곡점의 존재는 요구추력을 유지하면서 공력하중이 감소하는 효과가 있어 전체시스템의 크기와 무게를 감소시킬 수 있다.

• Advances in aircraft and spacecraft science
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• 제2권2호
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• pp.183-198
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• 2015

Scramjets are a class of hypersonic airbreathing engine that are associated with realizing the technology required for economical, reliable access-to-space and high-speed atmospheric transport. After-burning augments the thrust produced by the scramjet nozzle and creates a more robust nozzle design. This paper presents a numerical study of three parameters and the effect that they have on thrust augmentation. These parameters include the injection pressure, injection angle and streamwise injection position. It is shown that significant levels of thrust augmentation are produced based upon contributions from increased pressure, mass flow and energy in the nozzle. Further understanding of the phenomenon by which thrust augmentation is being produced is provided in the form of a force contribution breakdown, analysis of the nozzle flowfields and finally the analysis of the surface pressure and shear stress distributions acting upon the nozzle wall.

• 한국추진공학회지
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• 제10권1호
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• pp.9-17
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• 2006

우주항공 산업과 유도무기의 발달로 여러 종류의 다양한 고성능 추진기관의 개발이 요구됨에 따라서 보다 정확한 추력계측이 요구된다. 이와 같은 요구조건을 충족하기위하여 지금까지 국방과학연구소에서 개발하여 적용하고 있는 시험대의 설계 기법을 제시하고 시험대의 설계에 필요한 기본적이며 전문적인 지식, 개념을 정리한 것이다. 본 논문에서 정확도를 해치는 여러 가지 원인 분석과 제거기법을 제시하였으며 본 설계기법을 적용한 실례를 통하여 본 설계기법의 우수성을 확인하였다.