• Journal of Mechanical Science and Technology
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• 제17권5호
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• pp.726-739
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• 2003

A multi-dimensioanl model is being increasingly used to predict the thermo-flow field in the gas turbine combustor. This article addresses an integrated survey of modeling of the liquid spray formation and fuel distribution in gas turbine with high-shear nozzle/swirler assembly. The processes of concern include breakup of a liquid jet injected through a hole type orifice into air stream, spray-wall interaction and spray-film interaction, breakup of liquid sheet into ligaments and droplet,5, and secondary droplet breakup. Atomization of liquid through hole nozzle is described using a liquid blobs model and hybrid model of Kelvin-Helmholtz wave and Rayleigh-Taylor wave. The high-speed viscous liquid sheet atomization on the pre-filmer is modeled by a linear stability analysis. Spray-wall interaction model and liquid film model over the wall surface are also considered.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.217-220
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• 2010

본 논문에는 가스발생기를 사용한 사출시스템의 성능향상 즉 최대가속도를 줄일 수 있는 방법 중 하나인 노즐마개의 파열압 저감에 대한 내용이 기술되어있다. 여러가지의 노즐마개를 제작하여 공압시험으로 파열압을 측정하여 노치의 형상과 파열압과의 관계를 조사하였다. 파열압을 저감시킨 노즐마개를 적용하여 가스발생기를 제작, 시험한 결과 기준모델과 비교시 최대가속도를 저감에 효과적임을 확인하였다.

• 한국분무공학회지
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• 제24권2호
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• pp.58-65
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• 2019

A 3D FEM (Finite Element Method) based Helmholtz solver has been commonly used to characterize fundamental acoustic behavior and investigate dynamic instability features in many combustion systems. In this approach, a geometrical simplification of the target system has been generally made in order to reduce computational time and cost because a real combustor and fuel nozzle have a very complicated flow passage. The feasibility of these simplifications is quantitatively investigated in a small aero gas turbine nozzle in term of acoustic characteristics. It is found that the simplification in a nozzle geometry during the 3D FEM analysis process has no great influence on the acoustic modeling results, while the calculation complexity can be improved for a similar modeling accuracy.

• 한국가시화정보학회지
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• 제17권2호
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• pp.67-72
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• 2019

In this study, we investigate the non-reacting and reacting performance of single nozzle for post H class gas turbine by using commercial CFD tool, CONVERGE, based on adaptive mesh refinement. By varying swirl number and mixing length of base nozzle design. Through the numerical analysis, basic phenomena can be well described with respect to fuel concentration for non-reacting flow, temperature distribution, velocity vector and combustion outlet temperature distribution for reacting flow. However, there are rooms for improvements in model accuracy by comparing test results. Comparison between numerical analysis are planning for further study.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.335-338
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• 2010

A recent study for tracing the profiles of supersonic axisymmetric Minimum Length Nozzle with uniform and parallel flow at the exit section, the stagnation temperature is taken into account. The aim of this work is to add optimization algorithm to the supersonic nozzle design in order to get the optimum nozzle shape. The comparisons of the nozzle contours based on the method of characteristics are presented. The specific heats and their ratio vary with the stagnation temperature when this temperature of a perfect gas increases. An application is made for air in a supersonic nozzle.

• International Journal of Aeronautical and Space Sciences
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• 제18권1호
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• pp.82-90
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• 2017

The aim of this work is to develop a new computational program to determine the effect of using the gas of propulsion of combustion chamber at high temperature on the shape of the two-dimensional Minimum Length Nozzle giving a uniform and parallel flow at the exit section using the method of characteristics. The selected gases are $H_2$, $O_2$, $N_2$, CO, $CO_2$, $H_2O$, $NH_3$, $CH_4$ and air. All design parameters depend on the stagnation temperature, the exit Mach number and the used gas. The specific heat at constant pressure varies with the temperature and the selected gas. The gas is still considered as perfect. It is calorically imperfect and thermally perfect below the threshold of dissociation of molecules. A error calculation between the parameters of different gases with air is done in this case for purposes of comparison. Endless forms of nozzles may be found based on the choise of $T_0$, $M_E$ and the selected gas. For nozzles delivering same exit Mach number with the same stagnation temperature, we can choose the right gas for aerospace manufacturing rockets, missiles and supersonic aircraft and for supersonic blowers as needed in settings conception.

• Corrosion Science and Technology
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• 제9권6호
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• pp.239-246
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• 2010

When galvanized steel strip is produced through a continuous hot-dip galvanizing process, the thickness of the adhered zinc film is controlled by impinging a thin plane nitrogen gas jet. The thickness of the zinc film is generally affected by impinging pressure distribution, its gradient and shearing stress at the steel strip. These factors are influenced by static pressure of gas spraying at air knife nozzle, a nozzle-to-strip distance and strip and a geometric shape of the air knife, as well. At industries, galvanized steel strip is produced by changing static pressure of gas and a distance between the air knife nozzle and strip based on experimental values but remaining a geometric shape of nozzle. Splashing and check-mark strain can generally occur when a distance between the air knife nozzle and strip is too short, while ability of zinc removal can lower due to pressure loss of impinging jet when a distance between the air knife nozzle and strip is too long. In present study, buckling of the jet and change of static pressure are observed by analyzing flow characteristics of the impinging jet. The distance from the nozzle exit to the strip varies from 6 mm to 16 mm by an increment of 2 mm. Moreover, final coating thickness with change of a distance between the air knife nozzle and strip is compared with each case. An ability of zinc removal with the various distances is predicted by numerically calculating the final coating thickness.

• 대한공업교육학회지
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• 제33권1호
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• pp.282-296
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• 2008

기존의 자동차 부품 로봇 용접방법은 노즐을 통하여 $CO_2$ 가스가 확산되는 구조로 되어있어 용접대상물에 노즐간섭으로 인하여 로봇 용접이 불가능한 부위가 많고, 공간이 좁은 부분의 용접은 2차 수작업으로 완성하고 있어 생산성 향상에 걸림돌이었다. 따라서 본 연구에서는 이러한 용접과정을 분석하여 $CO_2$ 가스 소모량을 절약하고, 좁은 공간 부위를 로봇 용접할 수 있는 새로운 특수 용접 노즐을 개발하여 생산성을 향상시키고자 하였다. 본 연구개발에서 설계 제작된 협대역 자동차 부품 로봇 용접용 특수 용접 팁은 2단 구조로서 중단부에 직경 3mm의 구멍을 8개소로 제작하고 $CO_2$ 가스 소모량을 47%이상 절약한 형태로서 용접 결함율이 비교적 낮은 개발품이다. 본 연구의 결과는 국내 자동차 업계에서 사용되는 구형 용접 팁을 중간부에 구멍이 뚫린 2단 구조의 노즐로 대체하면 생산원가를 절감할 수 있다고 판단된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.381-385
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• 2005

최근 우주 개발 기술은 "더 빠르고, 저렴하고, 효율적인"으로 표현할 수 있다. 이런 장치들 사이에서 마이크로 추진 장치는 필수적인 요소이다. 또한 마이크로 노즐은 마이크로 추진 장치에서 가장 중요한 부분이다. 냉가스 추력기의 경우, 마이크로 노즐은 팽창비의 변화를 통해 압축 가스내의 저장된 에너지를 운동에너지로 변환시킨다. 본 논문에서는 노즐 팽창비와 비열비에 따른 마이크로 노즐의 특성을 실험하였다. 추력은 추력 측정 장치에 부착한 스트레인게이지를 사용하여 측정하였다. 또한 실험을 통해 마이크로 노즐의 성능을 평가해보았다.

• 한국정밀공학회지
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• 제4권4호
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• pp.84-92
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• 1987

To investigate the influence of the cutting pressure on the laser cutting quality, an expermental facility was constructed which can measure the cutting pressure distribution for various cutting conditions. Flow visualization was performed using the Schlieren photography and the pressure acting on the workpiece surface was measured, corresponding to the important process variables such as the kind of assist gas, nozzle pressure, distance between the nozzle exit and the workpiece surface, and the presence of the secondary nozzle. The cutting pressure acting on the workpiece was largely influenced by the nozzle pressure and nozzle-workpiece distance. The secondary nozzle which is used to raise the effective working pressure had its obvious role only when the angle between it and the main nozzle was small and when the distance between the nozzle exit and the workpiece surface was large.