• 대한기계학회논문집B
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• 제25권10호
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• pp.1346-1354
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• 2001

The heat transfer characteristics off swirling air jet impinging on a heated flat plate have been investigated experimentally. The main object is to enhance the heat transfer rate by increasing turbulence intensity of impinging jet with a specially designed swirl generator. The mean velocity and turbulent intensity profiles of swirling jet were measured using a hot-wire anemomety. The temperature distribution on the heated flat surface was measured with thermocouples. As a result the swirl effect on the local heat transfer rate on the impinging plate is confined mainly in the small nozzle-to-plate spacings such as L/D<3 at the stagnation region. For small nozzle-to-plate spacings, the local heat transfer in the stagnation region is enhanced from the increased turbulence intensity due to swirl motion, compared with the conventional axisymmetric impinging jet without swirl. For example, the local Nusselt number of swirling jet with swirl number Sw=0.75 and Sw=1 is about 9.7-76% higher than that of conventional impinging jet at the radial location of R/D=0.5. With the increase of the nozzle-to-plate distance, the stagnation heat transfer rate is decreased due to the diminishing axial momentum of the swirling jet. However, the swirling impinging jet for all nozzle-to-plate spacings tested in this study does not enhance the average heat transfer rate.

• 한국추진공학회지
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• 제11권4호
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• pp.1-9
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• 2007

많은 산업체들은 현재 연소기의 열효율을 증가시키기 위해 노력하고 있으며, 증가되는 NOx 발생으로 환경적인 규제에 직면하고 있다. 우리는 이렇게 열효율 증가와 NOx 발생 감소를 동시에 해결할 수 있도록 새로운 방법을 연구하였다. 이 새로운 개념은 확실히 NOx와 같은 오염물질을 절감시키며, 동시에 반경방향 열전달을 증가시키는 것으로 알려져 있고 이를 세차제트 연소기라고 부른다. 이러한 세차제트 노즐의 특징은 가스터빈의 연소효율의 증가로 이어질 수 있을 것이다. 기본적인 세차제트 노즐에 대한 특설파악을 위해 FLUENT를 이용한 수치해석, 레이저를 이용한 가시화 시험을 진행하였고, 노즐단면에서의 속도분포를 다른 논문의 실험결과와 비교하였다. Centerbody가 있는 경우 세차현상이 잘 일어났고 노즐 출구에서의 확산각이 증가함을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1771-1776
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• 2003

The supersonic swirl jet is being extensively used in many diverse fields of industrial processes since those lead to more improved performance, compared with the conventional supersonic no swirl jet. In the present study, an experiment is carried out to investigate the effect of annular swirl jet on the supersonic dual coaxial jet. A convergent-divergent nozzle with a design Mach number of 1.5 is used for the supersonic primary jet, and the sonic nozzles with four tangential inlets are used to make the secondary swirl jet. The primary jet pressure ratio is varied in the range from 3.0 to 7.0 and the outer annular jet pressure ratio is from 1.0 to 4.0. The interactions between the annular swirl and the inner supersonic jet are quantified by the pitot impact and static pressure measurements and visualized by using the Schlieren optical method. The results show that annular swirl jet alters the shock structure and impact pressure distributions compared with no swirl jet.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2003년도 추계학술대회 논문집
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• pp.91-94
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• 2003

The present study addresses experimental results to investigate the details of the near field flow structures produced in the under-expanded, dual, coaxial, swirling, jet. The sonic swilling jets are emitted from a sonic inner nozzle and the outer annular nozzle produces the co/counter swirling streams against the primary swirling jet, respectively. The interactions between both the secondary annular swirling and primary inner supersonic swirling jets are quantified by the pilot impact and static pressure measurements, and visualized by using the Schlieren optical method. The experiment has been performed fur different swirl intensities and pressure ratios. The results obtained show that the secondary co-swirling jet significantly changes the inner under-expanded swirling jet, such as the recirculation zone, pressure distribution, through strong interactions between both the swirling jets, and the effect of the secondary counter-swirling jet on the primary inner jet is similar to the secondary co-swirl jet case.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.15-18
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• 2003

The present study addresses an experimental investigations of the near field flow structures of supersonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the sonic and supersonic free jets. The interactions between the secondary swirl and inner soni $c^ersonic jets are quantified by a fine pilot impact and static pressure measurements and are visualized by using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary soni $c^ersonic jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary sonic and supersonic jets, compared with the secondary stream of no swirl. The results show that the presence of annular swirl stream causes the Mach disk to move more downstream, with the increased diameter, and remarkably reduces the fluctuations of the impact pressures in the supersonic dual coaxial jet, compared with the case of the secondary annular stream of no swirl.swirl.

• 한국전산유체공학회지
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• 제7권3호
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• pp.9-16
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• 2002

Most of modem aerospace gas turbines must be operated at a gas temperature which is several hundreds of degrees higher than the melting temperatures of the materials used in their construction. Complicated cooling schemes need to be employed in the combustor walls and in the high pressure turbine stages. Internal passages are cast or machined into the hot sections of aero-gas turbine engines and air from the compressor is used for cooling. In many cases, the cooling system is engineered to utilize jets of high velocity air, which impinge on the internal surfaces of the components. They are categorized as 'Impinging Cooling Method' and 'Vortex Cooling Method'. Specially, research of new cooling system(Vortex Cooling Method) that overcomes inefficiency of film cooling and limitation of space. The focus of new cooling system that improves greatly cooling efficiency using less amount of cooling air on surface heat transfer elevation. Therefore, in this study, a numerical analysis has been peformed for characteristics of flow and heat transfer in the swirl chamber and compared with the flow measurements by LDV. Especially, for understanding high heat transfer efficiency in the vicinity of wall, we considered flow structure, vortex mechanism and heat transfer characteristics with variation of the Reynolds number.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.580-585
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• 2003

The present study addresses experimental results to investigate the details of the near field flow structures produced in the under-expanded, dual, coaxial, swirling, jet. The sonic/supersonic swirling jets are emitted from the sonic inner nozzle and the outer annular nozzle produce the co-swirling and counter swirling against the primary swirling jet, respectively. The interactions between both the secondary annular swirling and primary inner supersonic swirling jets are quantified by the pitot impact and static pressure measurements and visualized by using the Schliern optical method. The experiment is performed for different swirl intensity and pressure ratio. The results obtained show that the secondary co-swirling jet significantly changes the inner under-expanded swirling jet, such as the recirculation zone, pressure distribution, through strong interactions between both the swirling jets and the effects of the secondary counter-swirling jet is similar to the secondary co-swirl jet case.

• 한국항공우주학회지
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• 제43권1호
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• pp.8-22
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• 2015

지금까지 인젝터의 수치적 시뮬레이션은 대부분 Eulerian 기법의 바탕위에서 이루어져 왔다. 그러나 액체제트의 미립화현상과 복잡한 공기와의 경계면 변화를 나타내는데 있어 기존의 기법들이 갖는 선천적인 단점이 존재하며 따라서 본 연구에서는 새로운 Smoothed Particle Hydrodynamics(SPH)라는 입자 기법을 도입하였다. 수치적 시뮬레이션을 위해 먼저 해석을 위한 SPH 코드를 개발하였으며 본 논문에서는 인젝터 문제를 정확하게 나타내는데 있어 필수적인 알고리즘중 하나인 다상유동모사에 대한 검증문제가 제시 되어 있다. 마지막으로 다양한 인젝터 종류 중 하나인 액체-액체 동축형 스월 인젝터에 대한 시뮬레이션이 수행되었으며 실제실험과의 비교를 진행하였다.

• 한국분무공학회지
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• 제19권2호
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• pp.75-81
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• 2014

Swirl flow in the gun type burner has a decisive effect on the stabilization of the flame, improvement of the combustion efficiency, and also a reduction of NOx. This swirl flow is created by the spinner which is inside the airtube that guide the combustion air. Gun type burner has generally the inner devices composed nozzle adapter, spark gap ignitor, and spinner. These inner components change the air flow behavior passing through air tube. Meanwhile, turbulent characteristics of this air flow are important to understand the combustion phenomena in the gun type burner, because the mixture of fuel and air are depended on. However, nearly all of the studies have been analyzed the turbulent flow of simplified combustion formation without the inner devices. So, this study conducted the measurement using by hot-wire anemometer and analyzed turbulent flow characteristics of the swirl flow discharged from the air tube with inner devices. Turbulence characteristics come up in this study were turbulence intensity, kinetic energy and shear stress of the air flow with the change of the distance of axial direction from the exit of the air tube.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.905-911
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• 2017

공기와 물을 사용하여 인젝터의 위치와 운동량 플럭스 비가 수직유동이 횡단유동장내의 수직분사 제트에 미치는 영향을 정성적으로 연구하고 도시하였다. 운동량 플럭스 비를 고정하고 인젝터 홀의 위치를 변화시키고 역으로 인젝터 홀의 위치를 고정하고 운동량 플럭스 비를 변화시켰다. 이미지 가시화는 고속카메라를 이용하여 Shadowgraph 기법을 사용하였다. 가시화된 이미지는 밀도구배강도 이미지를 통하여 분무의 차이를 비교하였다. 장치의 x/d가 증가할수록 제트의 분열 높이가 낮아지며 분무 각도 또한 감소하는 것을 관측하였다. x/d가 0일 때는 어떠한 운동량 플럭스 비에서도 분무가 바닥과 천장에 닿게 되는 결과를 보였다.