• Advances in aircraft and spacecraft science
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• v.9 no.1
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• pp.39-57
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• 2022

Instead of developing new guided missiles, converting unguided missile into guided ones by adding guidance and controlkits hasbecome aglobaltrend.Ofthemost efficient andwidelyused thrust vector control(TVC) techniquesin rocketry isthe jet vanes placed inside the nozzle divergentsection. Upon deflecting them, lift created on the vanesistransferred to the rocket generating the desired control moment. The presentstudy examinesthe concept of using an add-on jet vaneTVC kit to a plain nozzle.The impact of adding the kit with different vaneslocations and deflectionanglesisnumericallyinvestigatedbysimulatingtheflowthroughthenozzlewiththekit.Twohingelocations are examined namely, at 24% and 36% of nozzle exit diameter. For each location, angles of deflection namely 0°, 5°, 10°, and 15° are examined. Focus is made on variation of control force, thrust losses, lift and drag on vanes, jet inclination, and jetflow structure withTVCkit design parameters.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1136-1141
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• 2008

The helicopter rotor system generates lift, thrust, maneuvering force and moment to the helicopter with the torque and pitch control force transferred from the main rotor hub/control. And the tail rotor system generates the thrust for yaw axis control of the helicopter with the torque and pitch control force transferred from the tail rotor hub/control. Ground whirl test shall be performed to verify the compliance of requirement performance test and dynamic test of rotor blade and hub/control. This paper describes a design of whirl tower test facility for helicopter rotor system test and evaluation. Design results are summarized and compared with design requirements.

• Proceeding of EDISON Challenge
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• 2012.04a
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• pp.73-76
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• 2012

변장비의 변화에 따른 타원형 실린더 주위의 유동장을 해석하기 위하여 Navier-Stokes 방정식을 사용한 EDISON 열유체 툴로 분석하였다. 본 논문은 기존의 연구와 비교 분석하는데 목적을 두었으며, 기존의 연구결과와 비교 분석하기 위하여 계산 영역을 동일하게 설정하였다. 타원형 실린더의 변장비를 0.5, 1, 2, 4로 변화시키고 레이놀즈수 200, 400, 1000인 조건하에 유동장을 해석하였다. 본 연구의 해석 결과를 통해 선행연구와 전체적인 경향이 같다는 것을 알 수 있었고, 또한 변장비와 레이놀즈수는 항력진폭과 양력진폭, 스트로할 수에 영향을 미침을 알 수 있었다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.94-99
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• 2003

As the rotating speed of rotors is increased, the instability and power loss become serious problems. Gas bearings are introduced as a good solution to those problems. But in the development of gas bearings, high load capacity and high damping force to vibrations are required. In this study a new air bearing using leaf spring pad is introduced to improve load capacity and damping force. The experimental results of the leaf spring pad air bearings show high load capacity and high damping forces. And the results show that leaf spring pad air bearings can be simultaneously acted as radial and thrust bearings

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.350-355
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• 2007

Pad-eye is connected to crane with sling. When block is lift, pad-eye have a various applied force. Applied force on pad-eye is related to sling angle. Sling angle is decided by various parameters, including pad-eye location, sling length and crane location. Welded joint on pad-eye requires strength design because sling angle changes force on pad-eye. Strength design for welded joint of pad-eye will calculate with general mechanical design and FE analysis. FE analysis would become a useful tool in the analysis of welded joint. A commercial software(ANSYS 10.0) was used in the structural strength analysis for welded joint of pad-eye.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.6
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• pp.591-596
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• 2012

Recently, a vessel's maneuvering performance is considered to be an important subject to secure safety at short sea shipping. Especially the high turning performance, which is required to avoid the marine pollution by the ships that was grounded, becomes more severe. In this paper, we discuss the effect of increasing rudder force on turning performance of short sea shipping ship by free running test in towing tank. First of all, we make the 47K PC model ship and high-lift rudder using Coanda effect. And we make the free running test system for the turning test in towing tank. And also we perform the turing test of 47K PC model in several changes of Coanda jet momentum and evaluate the turing performance such as advance and tactical diameter. Finally, we confirm that the increasing of rudder force is very effective to improvement of turning performance of short sea shipping ship.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.229-240
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• 1991

The large camber angle theory of turbomachine blade of compressor has been developed recently for the two-dimensional flow by Hawthorn, et al. However, in the above theory it was assumed that the fluid was incompressible and inviscid, and the blades had no thickness. In this study, the flow in a blade cascade being mounted in parallel fashion with blade of arbitrary thickness is studied in order to determine the effects of the camber angle on the performance characteristic of the blade section under the consideration of compressibility and viscosity of fluid. The panel method is used for potential flow analysis. The flow in the boundary-layer is obtained by solving the integral boundary-layer structure through the laminar, transitional , and turbulent flow using the pressure field determined from the potential flow. And then the viscous-inviscid interaction scheme is used for interaction of these two flows. For the determination of the variation in the outlet fluid angle influenced by deviation in cascade flow, the superposition method which is used for single foil is introduced in this analysis. By the introduction of this method, the effects of the deviation on outlet fluid angle and the resulting fluid angle are made to adjust for oneself through the calculation. As the result of this study, the blade of large camber angle, large incidence angle, large pitch-chord ratio has large viscous and compressible effect than those of small camber angle. Lift force increase as camber angle increases, but above 60.deg. of camber angle, lift force decrease as camber angle increases. But drag force increases linearly with camber angle increases in the entire region.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.243-247
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• 2015

The characteristics of the fluid force reduction of a square prism having a small triangular prism at the upstream side was investigated by measuring of lift and drag on the square prism The experimental parameters were the width ratios (H/B=0.2~0.6) of triangular prisms to the prism width and the gap ratios (G/B=0~3) between the square prism and the triangular prism. The drag reduction rate of the square prism was increased and then decreased with G/B in case of the same H/B, and was increased with H/B in case of the same G/B. The maximum drag reduction rate was represented by 78.5% at H/B=0.6 and G/B=1.5. The lift reduction rate of the square prism was hardly not affected by the width and gaps ratios, the average value was about 52.4%.

• Journal of Korea Water Resources Association
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• v.51 no.5
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• pp.405-415
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• 2018

Hydraulic variables such as discharge coefficient, gate opening, and upstream water depth are required to calculate the discharge of vertical lift gate. It is very important for a precise gate design, because it may affect the rest, to predict the behavior of gate opening during operation. In this study, an equation by which gate opening could be predicted with any upstream water depths was derived from the relation between the calculated value from buoyancy theory and measured one from experiment for a floating gate model. Downpull force was the reason for the differences between the calculated and the measured and it was verified using pressure coefficient. Also, the relation of discharge coefficient with gate opening ratios was derived. The derived relations were used for flood routing and it was realized that downpull force effect should be fully taken into account during gate design.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.450-458
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• 2016

High performance small and mid-sized tractors are required for dryland and orchard operations. A power transmission system is the most important issue for the design of high performance tractors. Many operations, such as loading and lifting, use hydraulic power. In the present study, a hydraulic power transmission system for the 3-point hitch of a 50 kW narrow tractor was developed and its performance was evaluated. First, major components were designed based on target design parameters. Target operations were spraying, weeding, and transportation. Main design parameters were determined through mathematical calculation and computer simulation. The capacity of the hydraulic cylinder was calculated taking the lifting force required for the weight of the implements into consideration. Then, a prototype was fabricated. Major components were the lifting valve, hydraulic cylinder, and 3-point hitch. Finally, performance was evaluated through laboratory tests. Tests were conducted using load weights, lift arm sensor, and lift arm height from the ground. Test results showed that the lifting force was in the range of 23.5 - 29.4 kN. This force was greater than lifting forces of competing foreign tractors by 3.9 - 4.9 kN. These results satisfied the design target value of 20.6 kN, determined by survey of advanced foreign products. The prototype will be commercialized after revision based on various field tests. Improvement of reliability should be also achieved.