• 한국자동차공학회논문집
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• 제7권8호
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• pp.91-98
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• 1999

This paper describes the air flow characteristics inside the throttle valve. Tow-dimensional steady incompressible Navier-Strokes equation are solved numerically with embedding the conceopt of the artificial compressibility and adopting the Baldwin-Lomax turbulence model. With varying the valve opening angles(the Reynolds number )such as 15$^{\circ}$(5000) , 45$^{\circ}$(3000) , 75$^{\circ}$(7000) and 90$^{\circ}$(10000), respectively. tow cases, with a valve shaft and without one, are analysed. The pressure loss between the entrance and exit is severe at 15$^{\circ}$, 100 times as larger as that of 90$^{\circ}$ case, which also depends much on the existece of the valve shaft. The counter rotating vortices are formed over the valve plate with the shaft at only 75$^{\circ}$. They are smally and very large scale in front and back of the valve shaft , respectively. The velocity profiles of 15$^{\circ}$ and 90$^{\circ}$ at the exit are almost symmetric to the horizontal center line, however, the symmetricity is no longer maintained at 45$^{\circ}$ and 75$^{\circ}$ , and in addition, the flow at 75$^{\circ}$ is enforced a lot below center line. The pressure distribution on the walls is largely changed near the valve shaft, and its magnitude becomes great as the valve angle decreases.

• 한국기계가공학회지
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• 제18권6호
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• pp.45-54
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• 2019

In this study, we analyze the rattle noise of a power takeoff (PTO) driveline and develop a PTO driveline resonance model. We measured the rattle noise of the PTO driveline on the output shaft and, by analyzing the rattle noise in the time domain, we determine that the engine expansion stroke period matches the sound pressure of rattle noise. This finding helped us demonstrate that the rattle noise is caused by the collision between the PTO driving gear and the gear driven by the engine expansion stroke; the torsional vibration caused by this collision is affected by the angular velocity fluctuation of the PTO drive shaft. By measuring the angular velocity of the PTO drive shaft, we confirm that the angular velocity fluctuation of the engine flywheel tends to excessively amplify the PTO drive shaft angular velocity fluctuation. We conclude that the resonance, which occurs when the operating frequency of the engine is close to the natural frequency of the tractor power transmission system, causes the excessive angular velocity fluctuation of the PTO drive shaft. We performed a modal analysis of the PTO driveline resonance and, using the characteristic equation, we show that the resonance occurs when the engine rotation speed is close to 850 rpm, which matches the natural frequency of the PTO driveline.

• 대한기계학회논문집B
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• 제32권7호
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• pp.549-557
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• 2008

Despite of the laminar-turbulent transition region co-exist with fully turbulence region around the leading edge of an airfoil, still lots of researchers apply to fully turbulence models to predict aerodynamic characteristics. It is well known that fully turbulent model such as standard k-model couldn't predict the complex stall and the separation behavior on an airfoil accurately, it usually leads to over prediction of the aerodynamic characteristics such as lift and drag forces. So, we apply correlation based transition model to predict aerodynamic performance of the NREL (National Renewable Energy Laboratory) Phase IV wind turbine. And also, compare the computed results from transition model with experimental measurement and fully turbulence results. Results are presented for a range of wind speed, for a NREL Phase IV wind turbine rotor. Low speed shaft torque, power, root bending moment, aerodynamic coefficients of 2D airfoil and several flow field figures results included in this study. As a result, the low speed shaft torque predicted by transitional turbulence model is very good agree with the experimental measurement in whole operating conditions but fully turbulent model(${\kappa}-\;{\varepsilon}$) over predict the shaft torque after 7m/s. Root bending moment is also good agreement between the prediction and experiments for most of the operating conditions, especially with the transition model.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.3-8
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• 1997

This parer was presented for the experimental results of torsional vibrations of the horizontal rotating shaft with three disks. The torsional vibrations meter used is a laser system for non-contact measurement of torsional angular vibration velocity and torsional angular vibration displacement. The distance between the disks war changed; the one that had 76mm of disk distance war called basic model, and another that had 106mm of disk distance wide model, and other that had 46mm of disk distance narrow model. In each model, outer diameter of disk was 40mm. And 45mm, or 50mm was also used to extend the effective range of frequencies. The angula vibration displacement and the angular vibration velocity in its torsional vibration were measured to obtain the stable and the unstable regions.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.537-547
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• 2015

A Monte Carlo (MC) simulation was conducted to predict the reliability of a newly developed pyrotechnic pin puller. The reliability model is based on the stress-strength interference model that states that failure occurs if the stress exceeds the strength. In this study, the stress is considered to be the energy consumed by movement of a pin shaft, and the strength is considered to be the energy generated by pyrotechnic combustion for driving the pin shaft. Failure of the pin puller can thus be defined as the consumed energy being greater than the generated energy. These energies were calculated using a performance model formulated in the previous study of the present authors. The MC method was used to synthesize the probability densities of the two energies and evaluate the reliability of the pin puller. From a probabilistic perspective, the calculated reliability was compared to a deterministic safety factor. A sensitivity analysis was also conducted to determine which design parameters most affect the reliability.

• 한국융합학회논문지
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• 제11권3호
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• pp.195-200
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• 2020

본 연구에서는 8개의 터빈 날개면들이 각각 추진축상에서 45°, 40°, 35°의 각도로 기울어져 있는 Model 1, 2 및 3인 3가지 Model의 유체클러치 터빈 날개 형상에 대한 유동 해석들을 수행하였다. 터빈 날개면이 추진축상에서 각도가 크게 기울어질수록 터빈 날개의 뒷면 이후에서의 흐름에서 Model들 중에서 가장 유동 압력을 크게 받고 있음을 알 수 있다. 반면에 터빈 날개면이 추진축상에서 각도가 작게 기울어질수록 유동 속도가 작게 된다. 터빈 날개면이 추진축상에서 각도가 작게 기울어질수록, 즉 유체의 흐름과 수직에 가까운 날개 형상이 효율적으로 유체클러치에 동력을 연결하고 차단하는데 있어서 적합함을 알 수 있다. 유체클러치 터빈 날개 유형별 유동해석을 적용함으로서 본 논문에서의 연구 결과는 미적인 설계를 적용할 수 있는 융합 연구자료로서 유리하다고 여겨진다.

• 한국산업융합학회 논문집
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• 제22권1호
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• pp.1-9
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• 2019

In electric agricultural machine the gearbox is used to increase torque and lower the output speed of the motor shaft. The gearbox consists of several shafts, helical gears and spur gears works in series. Optimization plays an important role in gear design as reducing the weight or volume of a gear set will increase its service life and improve the bearing capacity. In this paper the basic design parameters for gear like shaft diameter and face width are considered as the input variables. The bending stress and material volume is considered as the objective function. ANSYS was used to investigate the bending stress when the variable was changed. Artificial Neural Network (ANN) was used to obtain the mathematical model of the system based on the bending stress behaviour. The ANN was used since the output system is nonlinear. The Genetic Algorithm (GA)　technique of optimization is used to obtain the optimized values of shaft diameter and face width on the pinion based on the ANN mathematical model and the results are compared as that obtained using the traditional method. The ANN and GA were performed using MATLAB. The simulation results were shown that the proposed algorithm was successfully calculated the value of shaft diameter and face width to obtain the minimal bending stress and material volume of the gearbox.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.104-108
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• 2003

Finite element (FE) model updating is a procedure to minimize the differences between analytical and experimental results, which can be usually posed as an optimization problem. This paper aims to introduce a hybrid optimization algorithm (GA-SA), which consists of a Genetic algorithm (GA) stage and an Adaptive Simulated Annealing (ASA) stage, to FE model updating for a shrunk shaft. A good agreement of the first four natural frequencies has been achieved obtained from GASA based updated model (FEgasa) and experiment. In order to prove the validity of GA-SA, comparisons of natural frequencies obtained from the initial FE model (FEinit), GA based updated model (FEga) and ASA based updated model (FEasa) are carried out. Simultaneously, the FRF comparisons obtained from different FE models and experiment are also shown. It is concluded that the GA, ASA, GA-SA are powerful optimization techniques which can be successfully applied to FE model updating, the natural frequencies and FRF obtained from all the updated models show much better agreement with experiment than that obtained from FEinit model. However, FEgasa is proved to be the most reasonable FE model, and also FEasa model is better than FEga model.

• 한국지반공학회논문집
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• 제23권8호
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• pp.35-45
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• 2007

말뚝의 거동특성은 지반조건 뿐만 아니라 말뚝의 형상에 의해서도 영향을 받는 것으로 알려져 있다. 본 논문에서는 비배토 테이퍼말뚝과 원통형말뚝의 연직거동과 지지력 특성을 조사하기 위해서 선단지지력과 주면마찰력을 분리해서 측정할 수 있는 모형말뚝과 가압토조를 이용해서 총 12회의 모형말뚝시험을 실시하였다. 시험결과 원통형말뚝의 주면 하중은 말뚝 직경의 4%에 해당하는 침하량에서 극한치에 도달하였다. 반면 테이퍼말뚝의 주면하중은 말뚝이 침하함에 따라 계속 증가하는 경향을 보였으며, 원통형말뚝의 주면하중보다 상당히 큰 것으로 나타났다. 그리고 조밀한 지반에서는 테이퍼말뚝의 전체지지력이 원통형말뚝보다 작은 반면 상대밀도가 보통인 지반에서는 테이퍼말뚝의 전체 지지력이 원통형말뚝보다 큰 것으로 나타났다. 테이퍼말뚝의 단위 극한선단지지력은 지반의 토압계수가 0.4보다 클 때 원통형말뚝보다 컸으며, 테이퍼말뚝의 단위 극한주면마찰력은 지반의 토압계수와는 무관하게 원통형말뚝보다 큰 것을 알 수 있었다.

• 대한조선학회논문집
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• 제50권5호
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• pp.282-290
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• 2013

The effects of the combination of blade number for forward and after propeller on the propeller shaft forces of a contra-rotating propeller (CRP) system are presented in the paper. The research is performed through the numerical simulations based on the Reynolds-Averaged Navier-Stokes equations (RANS). The simulation results of the present method in open water condition are validated comparing with the experimental data as well as the other numerical simulation results based on the potential method for 4-0-4 CRP (3686+3687A) and 4-0-5 CRP (3686+3849) of DTNSRDC. Two sets of CRP are designed and simulated to study the effect of the combination of blade number in behind-hull condition. One set consists of 3-blade and 4-blade, while the other is 4-blade and 4-blade. A full hull body submerged under the free surface is modeled in the computational domain to simulate directly the wake field of the ship at the propeller plane. From the simulation results, the fluctuations of axial force and moment are dominant in the case of same blade numbers for forward and after propellers, whereas the fluctuations of horizontal and vertical forces and moments are very large in the case of different blade numbers.