The visualization and mapping of turbulent premixed impinging flames

Front. Energy Power Eng. China

2009

It is known that fuel variability of different gas suppliers may cause combustion instability in a gas turbine combustor. Mechanisms that control the time scale of the heat release oscillations and acoustic pressure perturbations are both physical and chemical in nature, and thus can be influenced by changes in fuel composition. The intent of this study is to investigate the fuel variability on the flickering frequency of diffusion flames in the hope of understanding some of the fundamental aspects of fuel variability effect on the dynamics of combustion. Experiments were conducted at atmospheric pressure with a matrix of methane and propane blends. An optical fibre system was applied to capture simultaneously the flame flickering at two different light frequencies (430 nm and 516 nm), which provided a means of comparing the chemistry change. It was found that the low frequency oscillation of flow and flame structures depended only weakly on the exit velocities of the fuel, while ambient conditions had a significant effect on flickering frequencies and spectrum. The results of using CH 4 and C 3 H 8 as test fuels at different flow rates showed very little variations, with peak frequencies at 11-13 Hz. When the jet flame was not disturbed, harmonics to at least the third mode were obtained in most of these cases. However, the cases which included CH 4 /C 3 H 8 splits of 90/10, 85/15 and 80/20 by volume showed that unstable flickering frequencies and flame harmonics were not observed. When a mixture of methane/propane at a ratio of 1:1 was used the peak flickering frequency was around 6 Hz, and slight disturbance in the environment would cause the harmonics to disappear. Mechanisms thought to produce changes in the dynamic response and frequency harmonics were discussed.

Section: Methodsmentioning

confidence: 99%

Fuel variability effect on flickering frequency of diffusion flames

Front. Energy Power Eng. China

2009

“…It is found that different combustion modes of impinging flames can be established under identical nozzle flow conditions only by changing the initial ignition locations [9,10]. However, the aforementioned research mainly focused on the flame-to-wall heat transfer characteristics; the investigation of real flame structure and propagation dynamics during ignition process is rarely reported yet.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved 3D investigation of the ignition process of a methane diffusion impinging flame

Wang

Zhao

Experimental Thermal and Fluid Science

2015

The ignition process of a methane diffusion impinging flame was investigated experimentally, using high speed schlieren/stereo imaging and image processing techniques. Two types of flame can be identified during the ignition process: premixed like flame with weak blue colour and diffusion flame with yellow-reddish colour. The 3D structure of blue flame after enhancement and yellow flame has been reconstructed and analysed seperately. The ratio between green and blue colour intensity is used to provide indications of the global fuel/air mixture state of the blue flame, which is found to correlate well with the flow conditions and flame propagation characteristics.

“…The diffusion flame rig was modified from an impinging burner for premixed flame as described in the work of Foat et al (2001) and Ng et al (2002). Basically, it consists of a burner unit, a circular steel plate, and a fuel/air supply system.…”

Section: Methodsmentioning

confidence: 99%

Stereoscopic imaging and computer vision of impinging fires by a single camera with a stereo adapter

Int J Imaging Syst Tech

2005

In this article, the novelty of using a single camera for stereoscopic imaging and computer vision of fire dynamics has been described. Specifically, 3D surface topology of the fires can be reconstructed and visualized using stereoscopic methodology. The basic stereo apparatus used in the present study consists of a high-resolution digital camera and a stereo adapter, which is mounted to the front filter ring of the camera. A pair of stereo images could therefore be formed through the same lens system and recorded simultaneously on the same charge coupled device (CCD) chip. The mechanism of using a stereo adapter for stereoscopic imaging and its geometry has been elaborated in detail. The digitally reconstructed 3D results have also been validated by optical stereoscopic viewing using a pair of electronic shutter glasses synchronized with a computer monitor. The results have demonstrated that the single camera technique is a very powerful and cost-effective diagnostic tool for fire studies.