• 한국추진공학회지
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• 제18권2호
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• pp.80-85
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• 2014

노즐개방형 측추력기는 고체 추진기관을 사용하는 비행체의 궤도 수정 기능을 제공하는 장치이다. 노즐개방형 측추력기는 비교적 낮은 연소온도를 가지는 추진제, 안정된 추력을 공급하기 위한 중립형 추진제 그레인, 선택적 노즐 사용이 가능한 노즐개방장치로 구성되었다. 궤도 수정이 요구되면 추력 반대방향으로 필요한 추력만큼 노즐을 개방하여 비행체에 측추력을 발생시킨다. 궤도 수정 후 추력방향으로 노즐을 개방하여 측추력을 제거함으로써 추력 발생을 정지한다. 지상연소시험을 통해 측추력기의 작동과정을 확인하였으며, 본 연구를 통하여 개발된 노즐개방형 측추력기는 노즐개방을 통한 측추력 제어를 통해 비행체의 궤도 수정에 활용할 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.160-160
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• 2008

In practical etching process, etch ant is sprayed on the metal-deposited panel through nozzles collectively connected to the manifold and that panel is usually composed of many PCB(printed circuit board)'s. The etching uniformity, the difference between individual PCB's on the same panel, has become one of most important features of etching process. In this paper, the prediction of nozzle trajectory has been performed by the combination of algebraic formula and numerical simulation. With the pre-determined geometrical factors of nozzle distribution, the trajectories of individual nozzles were predicted with the change of process operational factors such as panel speed, nozzle swing frequency and so on. As results, two dimensional distribution of impulsive force of etchant spray which could be considered as a key factor determining the etching performance have been successfully obtained. Though only qualitative prediction of etching uniformity have been predicted by the process developed in this study, the expansion to the quantitative prediction of etching uniformity is expected to be apparent by this study.

• Journal of Advanced Marine Engineering and Technology
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• 제25권4호
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• pp.797-808
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• 2001

Three-dimensional trajectory of fluid particle is simulated by a particle motion, which is able to examine the influences of changes in the several parameters. To calculate the trajectory of a particle, the Runge-Kutta method was utilized. The use of a projectile of particles for the trajectory of liquid jet has been shown to be useful to estimate the influence of different operating parameters such as best particle diameter, density of liquid body, initial take-off velocity, wind velocity, cross wind velocity, take-off angle, and base angle for a released flow from the nozzle. The results give the trajectories of various types of particle of body and at different elevations, base angles, wind velocities and densities of liquid body. The trajectories in a vacuum show that air resistances decreases both the distance and the maximum height of a projectile, and also explain that the termination time is also reduced in air. In addition, the maximum distance in the x direction was obtained with take-off angles from 30 degrees to 45 degrees in still air and the projectile of particles was highly effected by wind and cross wind. Clearly, a particle has to be so positioned as to take the optimum possible advantage of the wind if the maximum distances is requested. The wind astern increased the maximum distances of x direction compared with the wind ahead. Finally, it is possible to optimize the design of pump by using these results.

• 한국분무공학회지
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• 제13권2호
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• pp.79-84
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• 2008

The correlations for cross-flow have not been well established, because of the complexity of breakup and atomization mechanism. A study was performed to investigate the characteristics of spray behaviour of liquid jet in the bag breakup regime injected into low-speed cross-flow with the pressure single-hole nozzle. The shadow-graphy method was used for the cross-flow jet visualization. The experimental variables of liquid jet were nozzle diameter $(0.3mm{\sim}1.0mm)$, injection pressure $(50kPa{\sim}150kPa)$, and the velocity of cross-flow $(27m/s{\sim}42m/s)$. The highest penetration trajectories of liquid jet are governed by the momentum ratio $({\rho}_{\iota}U_{\iota}^2/{\rho}_aU_{cross}^2)$ rather than the Weber number and the new empirical equations of the highest penetration trajectory and breakup point at low-speed corss-flow are established.

• Journal of Welding and Joining
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• 제29권2호
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• pp.64-71
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• 2011

In this paper, crack propagation analyses in the inner diameter (ID) repair weld of the dissimilar metal weldment of a nozzle were performed using a finite element alternating method (FEAM). To calculate the theoretical solution for the crack tip stress intensity factor, a weak type singular integral equation consisted of crack surface traction and dislocation density function was constructed and solved in conjunction with the FEAM. A two-dimensional axisymmetric finite element nozzle model was prepared and ID repair welding was simulated. An initial crack, 10% depth of weld thickness, was assumed and crack propagation trajectory from the initial crack to the 75% depth of thickness was calculated using the FEAM. Crack growth versus time curve was also calculated and compared with the curves obtained from ASME code method. With the method constructed in this paper, crack propagation trajectory and crack growth time were calculated automatically and effectively.

• 한국추진공학회지
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• 제9권4호
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• pp.73-80
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• 2005

유도무기의 추력방향 제어(Thrust Vector Control)를 위해 널리 운용되고 있는 가동노즐(Movable Nozzle)의 성능지표는 노즐의 회전중심(유효피봇)을 기준으로 결정된다. 그러나 유효피봇의 동특성으로 인해 실험이나 수학적으로 정확한 위치를 결정하기가 거의 불가능하다. 본 논문에서는 가동노즐 운동 특성을 ADAMS simulation 기법을 이용하여 파악하고 인공 신경망을 적용하여 유효 피봇을 추적할 수 있는 방법을 제안하였으며, 모사된 가상 가동노즐의 유효피봇 추적에 적용하여 만족스러운 결과를 얻음으로 벤취 실험이나 연소시험에 적용된 가동 노즐의 유효 피봇 추적에 활용 가능성을 제시하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.233-236
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• 2002

The high-pressurized spray nozzle is used f3r special washing and cutting with strong impact force. The performance of this nozzle, which focused on spray penetration and radial dispersion, was mainly investigated to maximize the momentum and minimize the flow loss. Hence, our experimental research was conducted by changing the aspect ratio ranging from 0 to 3 with nozzle outlet of 1.1. The spray trajectory far high-pressurized water was experimentally investigated using PDPA diagnostics, which was available at spray downstream region. As the spray at upstream near the nozzle exit did not show the improved disintegration. The results showed empirical correlation with regard to non-dimensional axial velocity distribution, spray penetration, and radial spreading rate with photographic visualization.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.411-413
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• 2009

본 논문은 초음속 추진을 이용한 미사일 시스템에 대한 궤적최적화에 대한 연구를 소개한다. 초음속 추진 시스템은 외부비행조건과 내부 연소 환경에 따른 복잡하고 비선형성이 강한 추력특성을 가진다. 이러한 이유로 초음속 비행체의 운용에 있어 많은 구속조건을 가지며 일반 비행체보다 좁은 비행영역안에서 운용되어야 한다. 본 논문에서는 이러한 특성을 가지는 초음속 비행체의 궤적최적화를 수행하고 보다 효율적인 운용에 대한 비전을 제시하고자 한다. 궤적최적화는 일반적인 초음속 추진에 관련한 구속조건들을 고려하며 수행되었고, 궤적최적화 결과를 통해 얻어진 효율적 연료공급 및 노즐 목 면적 제어에 대한 일반적인 운용 및 응용방안에 대해서 고찰하고자 한다.

• 대한기계학회논문집B
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• 제24권2호
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• pp.270-279
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• 2000

Recently, according to increase in the requirement of electric power, a thermoelectric power plant equipped with pulverized coal combustion system is highly valued, because coal has abundant deposits and a low price compared with others. For efficient use of coal fuel, most of plant makers are studying to improve combustion performance and flame stability, and reduce pollutants emission. One of these studies is how to control the profile of particle injection and velocity dependant on coal nozzle configuration. Basically, nozzle which has mixed flow of gas and particle is required to have the balanced coal concentration at exit, but it is very difficult to obtain that by itself without help of other device. In this study, coal distribution and pressure drop in gas-solid flow are calculated by numerical method in nozzle with various shapes of venturi diffuser as a means to get even coal particle distribution. The tentative correlations of pressure drop and exit coal distribution are deduced as function of the height, length and reducing angle of venturi from the calculated results. When coal hurner nozzle is designed, these equations are very useful to optimize the shape of venturi which minimize uneven particle distribution and pressure drop within coal nozzle.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.301-308
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• 1999

The present study investigates numerically particle laden flow through compressor cascades and a rocket nozzle. Engines are affected by various particles which are suspending in the atmosphere. Especially in the case of aircraft aviating in volcanic, industrial and desert region including many particles, each components of engine system are damaged severely. That damage modes are erosion of compressor blading and rotor path components, partial or total blockage of cooling passage and engine control system degradation. Numerical prediction and experimental data, erosion rates are predicted for two materials - ceramic, soft metal - on compressor blade surface. Aluminum oxide ($Al_2O_3$) Particles included in solid rocket propelant make ablative the rocket motor nozzle and imped the expansion processes of propulsion. By the definition of particle deposition efficiency, characteristics of particles impaction are considered quantitatively Stoke number is defined over the various particle sizes and particle trajectories are treated by Lagrangian approach. Particle stability is considered by definition of Weber number in rocket nozzle and particle breakup and evaporation is simulated in a rocket nozzle.