• Title, Summary, Keyword: 트림각

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Numerical Study on Cavitation Reduction in Velocity-Control Trim of Valve with High Pressure Drop (고차압 밸브의 속도제어형 트림에서 케이테이션 억제에 관한 수치적 연구)

  • Kim, Dae Kwon;Sohn, Chae Hoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.9
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    • pp.863-871
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    • 2013
  • Flow characteristics of velocity-control trim in a valve is investigated numerically with high pressure drop. A basic trim widely used for a valve in domestic powerplants is selected and designed for a baseline of velocity-control trim. The numerical analysis is focused on flow rate and cavitation with the basic trim. For a condition of high-pressure drop, pressure drop between inlet and outlet and fluid temperature are selected to be 18.1 MPa and $160^{\circ}C$, respectively, which are typical ones considering operating conditions adopted in powerplants. With this baseline model and condition, design changes are made for improvement of flow rate and cavitation phenomenon. For re-design, trim is divided into three zones in radial direction and design parameters of flow area, stage, and flow direction are considered in each zone. With these combined parameters applied to each zone, 4 models with design changes are proposed and their flow rates and cavitation areas are investigated. From comparison with those in the baseline model of a basic trim, proposed models show better performance in both flow rate and cavitation.

Sensor Fault Detection for Small Turboshaft Engine Considering Multiple Trim Conditions (다중 트림 상태를 고려한 소형 터보샤프트 엔진의 센서 고장 검출)

  • Seong, Sang-Man;Rhee, Ihn-Seok;Ryu, Hyeok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.192-195
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    • 2008
  • A sensor fault detection method for small turbo shaft engine considering multiple trim conditions is proposed. This engine is used in a helicopter. Firstly, under multiple trim conditions, we derive the linearized models from a nonlinear model which includes engine, rotor and feedback control loop. As a fault detection method, we adopt the Kalman filter based method. To keep continuity of estimates between the changes of trim conditions, we reconfigure the initial values of state variables at trim changes. We detect the faults with two steps that when the first filter does not alarm the faults for some sensors, the second filter is runned for other sensor. Via some simulations we show that the proposed method works well under multiple trim conditions.

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A Study on Improvement of Roll Autopilot System (가로축 자동비행시스템 개선에 관한 연구)

  • Kim, Chong-Sup;Koh, Gi-Oak;Ji, Chang-Ho;Cho, In-Je;Lee, Dong-Kyu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.8
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    • pp.706-711
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    • 2015
  • The fighter aircraft uses several different loading configurations for air-to-surface and air-to-air combat missions. To maintain wings-level flight with an asymmetric weapon configuration, a pilot controls a roll trim system. However, it is difficult to apply an accurate roll trim input for wings-level flight in the actual flight under disturbance. The inaccurate roll trim input degrades the performance of the roll autopilot system. In this paper, to solve this problem, an integrator was additionally designed in the command part of the roll autopilot system. The initial transient response was improved by scheduling the limiter to restrict the roll attitude error. As a result of the evaluation of the simulation for the designed flight control law, the roll attitude following performance was found to be improved in the autopilot system operation under the inaccurate roll trim condition.

A Study on the accuracy of speed measuring system by the Doppler effect -The error of speed single beam Doppler log over the ground by various trim- (Doppler 효과(效果)에 의한 속도계측장치(速力計測裝置)의 정도(精度)에 관(關)한 연구(硏究) -Single beam Doppler log의 트림 변화에 따른 대지속력(對地速力) 오차(誤差)-)

  • Kim, Koang-Hong
    • Journal of Fisheries and Marine Sciences Education
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    • v.9 no.2
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    • pp.179-187
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    • 1997
  • Doppler log and current meter are based on the measurment of the doppler effect. Ship's speed over the ground measured by means of doppler log effect of underwater ultrasonic intends to get infulence by the difference of sound velocity, the ship's course, the sea bottom inclination, the trim and tranducer installation etc. This paper investigated on the error of speed over the ground by change of the trim comparing the real speed obtained by the mile post with the speed of single beam type doppler log on the trainning ship Kyeongyangho. The results are as follows ; 1. Indicating speed of doppler log is very much greatly influenced on variation of trim, but the real speed is less affected variation by trim. 2. The range of variation and error of speed over ground are smallest when ship's trim is 2.15m trim by the stern.

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A Study on Longitudinal Flight Dynamics of a QTW UAV (QTW 무인항공기의 종축 비행동역학에 관한 연구)

  • Jung, Ji In;Hong, Sung Tae;Kim, Seungkeun;Suk, Jinyoung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.1
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    • pp.31-39
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    • 2013
  • A Quad Tilt Wing UAV is a new concept hybrid UAV having the advantages of both fixed-wing and rotary-wing aircraft. This paper presents longitudinal flight dynamic characteristics of a Quad Tilt Wing UAV. The designed Quad Tilt Wing UAV is a configuration of a tandem wing type aircraft with an actuating motor and propeller mounted at each wing. Momentum theory is used to calculate the thrust, and nonlinear modeling is performed considering lift and drag generated by slip stream effect of propellers. Also, Force and moment variation at each tilting angle is considered. Static trim on longitudinal axis is analyzed via numerical simulation. Componentwise force contribution was analyzed at each trim mode. Dynamic characteristics were evaluated through eigenvalue analysis for a linear model at each flight mode. It is verified that longitudinal dynamic characteristics are changing from unstable to stable state by continuous transition of dominant poles.

Trim Range and Characteristics of Autorotation(I): Rotor Speed Limit and Pitch Range (자동회전의 트림 범위와 특성(I): 로터 스피드 한계와 피치범위)

  • Kim, Hak-Yoon;Choi, Seong-Wook
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.6
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    • pp.487-497
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    • 2011
  • Numerical analysis has been performed to investigate the rotor speed and pitch range variations when the airspeed is increased in autorotation. Transient Simulation Method(TSM) was used to obtain the steady states of autorotation. The rotor blade was analyzed by the two-dimensional compressible Navier-Stokes solver in order to adapt to the airspeed increase and the results were used in the transient simulation method. Meanwhile, the Pitt/Peters inflow theory was used to supply the induced velocity fields. For the prescribed torque equilibrium state, the combinations of velocity, shaft angle, and pitch angle were produced to investigate the rotor speeds and variable ranges. The rotor tip Mach number and rotor speed were correlated and the trim range of pitch angle was observed with respect to the shaft angle decrease.

Unsteady Aerodynamic Analysis for Helicopter Rotor in Hovering and Forward Flight Using Overlapped Grid (중첩 격자를 이용한 제자리 및 전진 비행하는 헬리콥터 로터의 비정상 공력해석)

  • Im, Dong-Kyun;Wie, Seong-Yong;Kim, Eu-Gene;Kwon, Jang-Hyuk;Lee, Duck-Joo;Park, Soo-Hyung;Chung, Ki-Hoon;Kim, Seung-Bum
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.3
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    • pp.215-223
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    • 2009
  • In this paper, the helicopter aerodynamics is simulated in hovering and forward flight. Also, an overlapped grid technique is applied in this simulation to consider the blade motion and moving effects. The Caradonna & Tung's rotor blade was selected to analyze the unsteady aerodynamics in hovering and non-lift forward flight. Also, the AH-1G rotor blade was selected in forward flight. In forward flight case, the numerical trim was applied to determine the cyclic pitching angles using Newton-Raphson method, and the numerical results were in good agreement with experimental data, especially, the BVI effects were well simulated in advancing side in comparison other numerical results. The governing equation is a three dimensional unsteady Euler equation, and the Riemann invariants condition is used for inflow and outflow at the boundary.

The Comparison on Resistance Performance and Running Attitude of Asymmetric Catamaran Changing Angle of Inclination of Tunnel Stern Exit Region (비대칭 고속 쌍동선의 선미터널 출구영역의 경사각 변화에 따른 저항성능 및 항주자세 분석)

  • Kim, Sang-Won;Seo, Kwang-Cheol;Cho, Dea-Hwan;Kim, Byung-Jae;Lee, Gyeong-Woo
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • pp.232-233
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    • 2017
  • In this research, tunnel stern was applied on the asymmetric high-speed catamaran to evaluate vessel's hydrodynamic performance by numerical method, and the tunnel stern types are distinguished by angle of inclination of tunnel exit region into 3cases ($0^{\circ}$, $3^{\circ}$ and $6^{\circ}$). Consequently, it is confirmed that the total resistances of tunnel stern which have $0^{\circ}$ of inclination are lower about 4.8-17.9% than the bare hull in the wide speed range, but those of $3^{\circ}$ and $6^{\circ}$ of inclination tunnel stern are higher than bare hull about 5-14% and 5-29%, respectively. On the other hand, trim angles of $0^{\circ}$ of inclination tunnel stern show similar trend with those of bare hull in whole ranges of FnV but those of $3^{\circ}$ and $6^{\circ}$ of inclination tunnel stern are stabilized and declined respectively after FnV=1.54. These phenomena indicated that increasing angle of inclination of tunnel exit region had negative influence on resistance performance, however, it could make vessel's operation performance better than bare hull.

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A Numerical Study on the Selection of Main Specification of the 18.5ft Bass Fishing Boat (18.5ft급 경기용 배스보트의 주요제원 선정에 관한 수치해석 연구)

  • Lim, Jun-Taek;Seo, Kwang-Cheol;Park, Geun-Hong;Kim, Sang-Won
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.7
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    • pp.945-952
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    • 2018
  • Recently, bass fishing has become a marine leisure sport in Korea. There are 4 major fishing associations in Korea, and each association holds 10-15 tournaments each year. However, supply of 17 ft bass boats, which are preferred in leagues, depends 100 % on imports. In this study, we have derived the main specifications to develop the initial hull forms of a 18.5ft bass boat through statistical analysis based on mothership data. In addition, CFD numerical analysis was carried out according to deadrise angle and longitudinal center of gravity, which strongly influenced the resistance and planing performance. For numerical analysis, design speed was set to $Fn=3.284 (Re=9.858{\times}10^7)$, the deadrise angle was set from 12 to $20^{\circ}$, and the longitudinal center of gravity was set in the range of 0 to $8%L_{wL}$ from the center of buoyancy to the stern. Based on the numerical results, we first set the range of these factors by resistance performance and immersion keel length. Furthermore, using a correlation graph of Savitsky's Drag-Lift ratio, we derived the deadrise angle ($14-16^{\circ}$) and longitudinal center of gravity ($4-6%L_{wL}$).