• Journal of Welding and Joining
• /
• 제27권6호
• /
• pp.9-16
• /
• 2009

In this paper, the coaxial monitoring system to capture image of weld pool was developed in laser-arc hybrid welding. In order to obtain the reliable image, green laser was used as a illumination system and measuring components such as band pass filter, ND (Neutral Density) filter and shutter speed was designed and optimized. Using this monitoring system, weld pool images were captured according to laser power, welding speed, welding current and interspace between laser and arc through the experiment. ANOVA (Analysis of Variation) was carried out to identify the influence of process variables on bead widths extracted from captured images of monitoring system. Welding speed and current were major factor to affect weld pool.

• 대한기계학회논문집B
• /
• 제20권6호
• /
• pp.1948-1958
• /
• 1996

Experimental and theoretical studies on the air-assist coaxial atomizer have been continuously carried out for a long time. But now the importance of the theoretical study is tending to increase as with the development of computer. This study is concerned to the spray modelization, especially, the instability of the liquid jet surrounded by the air stream which flows with high velocity. To study the phenomena of the break up, we used the linear theory based on the classical Kelvin-Helmholtz theory for capillary wave at a simple interface and we investigated the variation of liquid core radius. As a result, we obtained that the drop diameter and the variation of the liquid core radius predicted by using our model are reasonable.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
• /
• pp.282-287
• /
• 2004

Unielement combustion tests were conducted using coaxial bi-swirl injectors. Major experimental parameters were a recess length and a fuel-side swirl chamber. Combustion efficiency mainly depends on a mixing mechanism for the present coaxial swirl injectors. Low-frequency pressure excitations around 200Hz were observed for all injectors. However, dynamic behaviors considerably differ for an external and an internal mixing case controlled by a recess length. The internal mixing induces mixture to be biased at a specific frequency in a mass flow rate, which results in a relatively high amplitude of pressure fluctuations but results for the external mixing case show that fuel and oxidizer mixture flow carries more complicated, multiple wave characteristics due to broad mixing region as well as disintegration and merging phenomena of propellant films.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
• /
• pp.77-78
• /
• 2011

케로신/산소의 연소 해석을 위하여 연소 해리 성분을 고려한 다단 준총괄 반응을 개발하였다. 총괄 반응 상수는 실험 데이터에 잘 부합하도록 결정하였다. 개발된 다단 총괄 반응을 이용하여 케로신/산소 축대칭 전단 동축 분사기의 연소 유동에 대한 수치 해석을 수행하였다. 고해상도 기법을 이용한 해석을 통하여 리세스가 유동 불안정성의 증가시켜 연료 공기 혼합 및 연소 효율을 증대에 기여하는 정성적 특징을 확인하였다.

• 한국분무공학회지
• /
• 제24권2호
• /
• pp.82-88
• /
• 2019

Shear coaxial injectors were commonly used in rocket engine combustor. They showed good combustion performance. However it is not easy to control the thrust. Pintle injectors were not as popular as the coaxial injectors so far, they have a great advantage over the coaxial injectors. That is, it is relatively easy to control the thrust. Spray characteristics of gel type propellant from movable sleeve pintle injector were investigated. Water with 0.05% of Carbopol 940 was used as gel simulant instead of kerosene gel combined with Thixarol ST for academic purpose. Experiments were performed in various temperature, pressure and pintle opening condition. The results were compared with neat liquid spray. It is also verified that the capabilites of the injector by adjusting the pintle opening.

• Korean Chemical Engineering Research
• /
• 제57권5호
• /
• pp.723-729
• /
• 2019

A theoretical analysis was conducted of convective instability driven by buoyancy forces under transient temperature fields in an annular porous medium bounded by coaxial vertical cylinders. Darcy's law and Boussinesq approximation are used to explain the characteristics of fluid motion and linear stability theory is employed to predict the onset of buoyancy-driven motion. The linear stability equations are derived in a global domain, and then cast into in a self-similar domain. Using a spectral expansion method, the stability equations are reformed as a system of ordinary differential equations and solved analytically and numerically. The critical Darcy-Rayleigh number is founded as a function of the radius ratio. Also, the onset time and corresponding wavelength are obtained for the various cases. The critical time becomes smaller with increasing the Darcy-Rayleigh number and follows the asymptotic relation derived in the infinite horizontal porous layer.

• 한국분무공학회지
• /
• 제26권1호
• /
• pp.9-17
• /
• 2021

Six shear coaxial injectors with different recess length and taper angle were manufactured. Cold-flow tests on the injectors were performed at room temperature and pressure using water and air as simulants. By changing the water mass flow rate and air mass flow rate, spray images were taken under single-injection and bi-injection. Breakup length and spray angle were analyzed from instantaneous and averaged spray images using image processing techniques. For all the injectors, the breakup length generally decreased as the momentum flux ratio increased at the same gas mass flow rate. The injectors with 7.5° taper angle usually had the longest breakup length and the smallest spray angle. When the taper angle was 15° or more, it hardly affected breakup length and spray angle. The recess length did not influence breakup length but its effect on spray angle depended on the taper angle.

• 한국안전학회지
• /
• 제8권3호
• /
• pp.19-25
• /
• 1993

This paper deals with the experimental study of the turbulent characteristics in the swirling coaxial Jets. In this research, the experimental study has been carried out to investigate the effects of swirl number and equivalence ratio on the flow characteristics in nonreacting flow field of the model combustor which symplifys the continuous type combustor for the practical use. Author particularly Intends to find out the fuel-air mixing In the recirculation zone In order to make sure the effects of swirl number and equivalence ratio on the stabilization of flame.

• 연구논문집
• /
• 통권23호
• /
• pp.57-62
• /
• 1993

An experimental investigation was carried out to study the characteristics of concentration of a coaxial jet being tone excited and consisting of $CO_2$, and air. The concentration in a binary gas mixture was measured by using the hot-wire anemometer and flow visualization was performed by the schlieren technique. In the case of excited flow, it is found that acoustic energy is partially transferred to RMS concentration to enhance mixing.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2008년도 춘계학술발표대회 개요집
• /
• pp.48-48
• /
• 2008