Gradient, counter-gradient transport and their transition in turbulent premixed flames
| dc.contributor.author | Zimont, Vladimir L. | |
| dc.contributor.author | Biagioli, Fernando | |
| dc.date.accessioned | 2014-05-27T09:34:08Z | |
| dc.date.available | 2014-05-27T09:34:08Z | |
| dc.date.issued | 2001 | |
| dc.description.abstract | We theoretically and numerically analyze the phenomena of counter-gradient transport in open premixed turbulent flames. The focus is on the transition from counter-gradient to gradient transport obtained when reducing the turbulence intensity/laminar flame speed ratio, a phenomenon recently found in open laboratory flames experiments by Frank at el. The analysis is based on the TFC combustion model for the simulation of turbulent premixed flames at strong turbulence (u`>>sι). In this case earlier work suggests that turbulent premixed flames have increasing flame brush with controlled in the model only by turbulence and independent from the counter-gradient transport phenomenon which has gasdynamics nature, and a turbulent flame speed which quickly adapts to a local equilibrium value, i. e. Intermediate Steady Propagation (ISP) flames. According to the present analysis transport in turbulent premixed flames is in fact composed by two contributions: real physical gradient turbulent diffusion, which is responsible for the growth of flame brush thickness, and counter-gradient pressure-driven convective transport related to the differential acceleration of burnt and unburnt gases subject to the average pressure variation across the turbulent flame. The novel gas dynamics model for the pressure-driven transport which is developed here, shows that in open turbulent premixed flames the overall transport may be of gradient or counter-gradient nature according to which of these contributions is dominant and that along the flame a transformation from gradient to counter-gradient transport takes place. Reasonable agreement with the mentioned laboratory experimental data, strongly support the validity of the present modeling ideas. Finally, the model predicts existence of this phenomenon also in large-scale industrial burners at much higher Reynolds number. | IT |
| dc.identifier.uri | http://hdl.handle.net/11050/952 | |
| dc.language.iso | en | IT |
| dc.subject | turbulent flame | IT |
| dc.subject | counter-gradient transport | IT |
| dc.subject | premixed turbulent combustion | IT |
| dc.subject | gas | IT |
| dc.subject | Reynolds number | IT |
| dc.subject.een-cordis | EEN CORDIS::FISICA E SCIENZE ESATTE::Fisica::Fisica dei fluidi | IT |
| dc.subject.een-cordis | EEN CORDIS::FISICA E SCIENZE ESATTE::Matematica, statistica::Modellazione matematica | IT |
| dc.subject.een-cordis | EEN CORDIS::ENERGIA::Altri temi di energia::Combustione, fiamme | IT |
| dc.title | Gradient, counter-gradient transport and their transition in turbulent premixed flames | IT |
| dc.type | Report | IT |