Effect of Swirl Flow on Flame Structure and Stability in Turbulent Combustion

In this study, we have investigated turbulent premixed flames affected by local stretch in a swirl flow, measured by the simultaneous OH-PLIF/SPIV system. Evaluating the transient of burning velocity and stretch rate, the flow and the flame dynamics in a cyclone-jet combustor were discussed. The flame front was determined by the OH fluorescence signal. Results show that the axial mean velocity becomes the maximum around the center axis, whereas the axial or the radial rms velocity takes the maximum at the position far from the center axis. These could be caused by the velocity fluctuation due to the flame and flow interactions. According to the local burning velocity and the stretch rate, the estimated Markstein number (Ma) roughly matches the value of the laminar flame. With an increase of the swirl number (S w ), the rms velocity is enlarged. Interestingly, the probability of higher burning velocity increases at larger S w . At the same time, the flame extinction occurs more frequently. Thus, it is derived that the swirl flow has a positive effect to increase the local burning velocity, but it simultaneously has a negative effect which causes the local flame extinction.

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“…The turbulent flames are largely affected by the local stretch (Suzuki and Yamamoto, 2013;Kazbekov et al, 2021). As seen in Eq.…”

Section: Introductionmentioning

confidence: 99%

Flow field and local burning velocity affected by stretch in swirl flow of turbulent premixed flames

Yamamoto

Yamamori

Suzuki

2022

JTST

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Flow field and flame surface density of turbulent flames by simultaneous PIV/OH-PLIF measurements

Yamamoto¹,

Yamamori²,

Asada³

2018

JTST

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Simultaneous measurements of flame geometry and flow field by OH-PLIF/Stereo PIV

和弘

健太

直樹

2016

Transactions of the JSME (In Japanese)

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It is difficult to understand turbulent combustion, because the combustion process is very complex and unsteady. One of the useful parameters for discussion of the unsteady flame behaviors is the flame stretch rate, which is evaluated by local flame curvature and strain rate. In this study, we conducted simultaneous OH-PLIF/Stereo PIV measurements of turbulent premixed flames. Flame shape and flow field were obtained. Then, local flame curvature and strain rate were discussed. The turbulent flame was established by a cyclone-jet combustor for propane/air mixtures. The main jet velocity was U m = 10, 30 m/s, and the equivalence ratio was  m = 0.75, 0.90. The equivalence ratio of the cyclone jet was the same as that of the main jet, but the velocity of the cyclone jet was the constant of 10 m/s. It was found that the variation of flame curvature was large when the main jet velocity was high. Difference between curvature convex to unburned gas and curvature convex to burned gas was relatively small. Frequency of larger strain rate was high when the main jet velocity was large and equivalence ratio was small. It is suggested that the local flame extinction could be caused by the large strain rate because the local flame extinction occurs more frequently. At all conditions, compared with the positive strain rate, the frequency of negative strain rate was high.

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Effect of Swirl Flow on Flame Structure and Stability in Turbulent Combustion

Cited by 4 publications

References 18 publications

Flow field and local burning velocity affected by stretch in swirl flow of turbulent premixed flames

Flow field and local burning velocity affected by stretch in swirl flow of turbulent premixed flames

Flow field and flame surface density of turbulent flames by simultaneous PIV/OH-PLIF measurements

Simultaneous measurements of flame geometry and flow field by OH-PLIF/Stereo PIV

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