Large Eddy Simulation and PIV Measurements of Unsteady Premixed Flames Accelerated by Obstacles |
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Authors: | V Di Sarli A Di Benedetto G Russo S Jarvis E J Long G K Hargrave |
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Institution: | (1) Istituto di Ricerche sulla Combustione, Consiglio Nazionale delle Ricerche (CNR), Via Diocleziano 328, 80124 Naples, Italy;(2) Dipartimento di Ingegneria Chimica, Università degli Studi di Napoli Federico II, Piazzale Tecchio 80, 80125 Naples, Italy;(3) Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK |
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Abstract: | In gas explosions, the unsteady coupling of the propagating flame and the flow field induced by the presence of blockages
along the flame path produces vortices of different scales ahead of the flame front. The resulting flame–vortex interaction
intensifies the rate of flame propagation and the pressure rise. In this paper, a joint numerical and experimental study of
unsteady premixed flame propagation around three sequential obstacles in a small-scale vented explosion chamber is presented.
The modeling work is carried out utilizing large eddy simulation (LES). In the experimental work, previous results (Patel
et al., Proc Combust Inst 29:1849–1854, 2002) are extended to include simultaneous flame and particle image velocimetry (PIV) measurements of the flow field within the
wake of each obstacle. Comparisons between LES predictions and experimental data show a satisfactory agreement in terms of
shape of the propagating flame, flame arrival times, spatial profile of the flame speed, pressure time history, and velocity
vector fields. Computations through the validated model are also performed to evaluate the effects of both large-scale and
sub-grid scale (SGS) vortices on the flame propagation. The results obtained demonstrate that the large vortical structures
dictate the evolution of the flame in qualitative terms (shape and structure of the flame, succession of the combustion regimes
along the path, acceleration-deceleration step around each obstacle, and pressure time trend). Conversely, the SGS vortices
do not affect the qualitative trends. However, it is essential to model their effects on the combustion rate to achieve quantitative
predictions for the flame speed and the pressure peak. |
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Keywords: | Large eddy simulation Particle image velocimetry Unsteady propagation Premixed combustion Obstacles Sub-grid scale turbulence |
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