• 한국분무공학회지
• /
• 제3권2호
• /
• pp.42-50
• /
• 1998

The effect of swirl flows un the fuel spray characteristics were investigated for various swillers in a model combustor. The interaction between the flow field and fuel spray in the main combustion tone made by frontal devices including fuel injection nozzles and swirlers. which were characterized by flow velocities, fuel droplet sizes and their distributions which were measured by APV(Adaptive Phase/Doppler Velocimetry) under atmospheric condition at 320cc/min kerosine fuel flow and 0.04kg/sec air supply. A dual swirler with circumferential two-stage swirl vanes of $40^{\circ}\;and\;45^{\circ}$ vanes in different directions and two single-stage swillers of $40^{\circ}$ vanes with 12 and 16 vanes were tested. It was found that the dual swirler has the largest recirculating zone with highest reverse flow velocity. The strongest swirl flow was found at the boundary of recirculation zone. Small fuel droplets were observed in the main axial stream and inside the recirculation zone when swirling flow field were generated by the frontal devices. These findings could give the tips on the optimal design of frontal devices to realize low emissions in gas turbine combustion.

• International Journal of Aeronautical and Space Sciences
• /
• 제15권4호
• /
• pp.444-453
• /
• 2014

A throttleable rocket engine enables operational possibilities such as the docking of spacecraft, maneuvering in a certain orbit and landing on a planet's surface, altitude control, and entrance to atmosphere-less planets. Thus, throttling methods have long been researched. However, dual-manifold injectors, which represent one throttling method, have been investigated less than others. In this study, dual-manifold and single-manifold injectors were compared to determine the characteristics of dual-manifold injectors. Also, the effects of gas injection were investigated with various F/O ratios. To investigate the characteristics, mass flow rate, spray pattern, spray angle, and droplet size were measured. The spray angle and droplet size were captured by indirect photography. About 30 images were taken to assess the spray patterns and spray angle. Also, 700 images were analyzed to understand the droplet distribution and targeting area, moving to the right from the centerline with 1.11-cm intervals. The droplet size was obtained from an image processing procedure. From the results, the spray angle showed two transition regions, due to swirl momentum in the swirl chamber regardless of the F/O ratio. The droplet size showed similar trends in both dual-manifold and single-manifold injectors except in the low mass flow rate region. In the case of the dual- manifold injector, the spray cone was not fully developed in the low mass flow rate region due to low angular momentum in the swirl chamber.

• 한국추진공학회지
• /
• 제7권3호
• /
• pp.30-37
• /
• 2003

Swirl 인젝터는 유체가 접선방향의 주입구를 통해 주입되어 인젝터 내부에서 접선방향 속도와 축방향 속도를 갖고 흐르다 노즐에서는 속도성분비에 의해 결정된 분산각에 따라 흐른다. 이러한 분산각은 특히 이중 swirl 인젝터에서 두 유체가 분무되어 서로 간섭을 주고 특히 recess가 있는 경우 내부 혼합 등의 이유로 예측이 어렵다. 이러한 분산각 현상을 recess 길이별로 실험을 통하여 규명하고 또한 상용 열수력 해석 코드인 FLUENT Version6.0을 사용하여 수치해석하였다. 다상유동 해석 모델중 VOF (Volume Of Fluid)모델을 사용하여 모사하고 실험결과와 비교하여 적용 타당성을 확인하였으며, recess가 단독 분사시와 혼합 분사시 분산각에 미치는 영향에 대하여 분석하였다.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
• /
• pp.149-152
• /
• 2012

The laboratory experiments have been conducted to investigate the effects of air preheated temperature on the emission characteristics by a model gas turbine burner with a hybrid/dual swirl jet flames configuration. The concentration of NOx and CO emissions, and flue gas temperature at combustor exit were measured with varying the equivalence ratio for different air preheated temperatures of 300, 400, 500K at atmospheric pressure. It was overall shown that the NOx and CO emissions, and flue gas temperature were decreased according to the decreasing of equivalence ratio due to the effects of lean premixed combustion regardless of the air preheated temperature. Experimental results of a lean premixed flames configuration indicated that the NOx emission was increased with higher inlet air temperature and air flow rate, which is attributed to the increasing of flue gas temperature and heat release related to the thermal NOx mechanism. But the CO emission was shown the opposite tendency, that is, the CO emission was decreased with increasing of inlet air temperature and flow rate.

• 한국추진공학회지
• /
• 제18권4호
• /
• pp.33-42
• /
• 2014

이중선회 연소기에서 다양한 화염거동과 파일럿 화염과 주 화염의 상호작용에 관한 연구가 수행되었다. 주 선회각이 $45^{\circ}$로 고정된 상태에서 파일럿 선회각도, 총 열 발생률 그리고 주 화염의 당량비가 주요 변수로 검토되었다. 주요한 결과로써, 이중선회 연소기의 상세한 화염안정화 영역이 총 발열량과 주화염의 당량비 변화를 통해 발생되는 5가지 화염모드를 통해 확인되었다. 파일럿 화염의 선회각도는 파일럿 화염의 위치 및 연소기 전체의 유동구조에 가장 큰 영향을 미치게 되며, 그 결과 내부 및 외부 화염간의 상호작용의 큰 변화를 가져온다.

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

• 한국유체기계학회 논문집
• /
• 제4권2호
• /
• pp.35-43
• /
• 2001

The flow characteristics passing a multi-point Pitot tube flow-meter of diamond shape and the characteristics of flow coefficients of the flow-meter are experimentally studied by varying combination of upstream rectangular dual elbows. The results provide the flow coefficients, which show good stability and reliability within the Reynolds number range coveted here in this study, and which can be used to measure flow-rates in practice. The variation of dual elbows upstream can change the velocity field so much that the flow pattern might thwart the precise flow measurement using the multi-point Pitot tube. The strongest swirl is detected in the case of $90^{\circ}$ dual elbow combination of all. In addition, it is observed that flow separation remains unchanged and occurs at the same point irrespective of various upstream dual elbow combinations.

• 한국추진공학회지
• /
• 제17권5호
• /
• pp.60-69
• /
• 2013

마이크로 가스터빈용 하이브리드/이중 선회 제트 연소기의 형상 최적화에 대한 실험연구가 수행되었다. 고정된 열부하에서 pilot 버너의 위치 및 선회기 베인의 방향이 주요 변수로 검토되었다. 주요 결과로서, pilot 버너 및 연료 노즐의 위치변화는 버너 출구 근처의 최소 유동면적 및 재순환 유동패턴의 변화를 발생시키며, 이로 인하여 선회강도 및 화염형상이 큰 영향을 받게 된다. 선회기 베인 각도의 증가($30^{\circ}$에서 $45^{\circ}$)는 희박가연한계 근처에서 CO 배출량을 크게 저감시킨다. 추가로 정방향 선회형상이 역방향 선회형상에 비해 보다 낮은 CO 및 NOx 배출량을 갖게 됨을 확인하였다.

• 한국전산구조공학회논문집
• /
• 제20권4호
• /
• pp.407-416
• /
• 2007

가스터빈에서 연료 분무 노즐은 연소 특성에 영향을 미치는 중요한 부품이다. 스월 분무 장치를 설계하기 위하여 유량과 분무액적 평균 직경을 설계변수로 정하고 연료 분무 노즐의 최적화를 수행하였다. 설계변수는 이중 노즐의 실험값들을 비교하여 중요한 영향을 미치는 변수로 선정하였다. 민감도는 유량과 분무액적 평균 직경의 변화에 따른 값을 사용하였다. 이중 오리피스형 스월 분무장치의 형상 최적설계를 통하여 유량의 미립화를 높이도록 연구하였다. 최적설계를 위하여 실험 계획법을 이용하였으며, 영향을 적게 미치는 설계변수들은 설계대상에서 제외하였다. 분무 노즐의 분무액적 평균 직경을 사용한 결과는 Jasuja의 액적 평균 이론을 이용하여 도출된 결과와 유사함을 알 수 있었다. 연구 결과는 이중 오리피스형스월 분무장치와 이와 비슷한 종류의 노즐 최적화를 위한 특성을 파악하고 최적의 유량과 허용 공차를 제시하였다.

• 열처리공학회지
• /
• 제35권1호
• /
• pp.27-32
• /
• 2022

Microbubble technology has been widely applied in various industrial fields. Recently, research on many types of microbubble application technology has been conducted experimentally, but there is a limit in deriving the optimal design and operating conditions. Therefore, if the computational fluid dynamics (CFD) analysis of multiphase flow is used to supplement these experimental studies, it is expected that the time and cost required for prototype production and evaluation tests will be minimized and optimal results will be derived. However, few studies have been conducted on multiphase flow CFD analysis to interpret fluid flow in microbubble generators using swirl flow. In this study, CFD simulation of multiphase flow was performed to analyze the air-water mixing process and fluid flow characteristics in a microbubble generator with a dual-chamber structure. Based on the simulation results, it was confirmed that a negative pressure was formed on the central axis of rotation due to the strong swirling flow. And it could be seen that the air inside the suction tube was introduced into the inner chamber of the microbubble generator. In addition, as the high-speed mixed fluid collided with external water sucked by the negative pressure near the outlet, a large amount of microbubbles was ejected due to the shear force between the two flows flowing in opposite directions.