Numerical analysis of ignition and flame stabilization in an n-heptane spray flame

Author(s):  
Lei Zhou ◽  
Zhen Lu ◽  
Zhuyin Ren ◽  
Tianfeng Lu ◽  
K. H. Luo
2017 ◽  
Vol 36 (2) ◽  
pp. 2567-2575 ◽  
Author(s):  
F. Shum-Kivan ◽  
J. Marrero Santiago ◽  
A. Verdier ◽  
E. Riber ◽  
B. Renou ◽  
...  

Author(s):  
Fernando Biagioli ◽  
Alessandro Innocenti ◽  
Steffen Terhaar ◽  
Teresa Marchione

Abstract Lean premixed gas turbulent flames stabilized in the flow generated by an industrial swirl burner with a central bluff body are experimentally found to behave bi-stable. This bi-stable behaviour, which can be triggered via a small change in some of the controlling parameters, for example the bulk equivalence ratio, consists in a rather sudden transition of the flame from completely lifted to well attached to the bluff body. While several experimental investigations exist on this topic, numerical analysis is limited. The present work is therefore also of numerical nature, with a two-fold scope: a) simulation and validation with experiments of the bi-stable flame behaviour via Computational Fluid Dynamics (CFD) in the form of Large Eddy Simulation (LES) and b) analysis of CFD results to shed light on the flame stabilization properties. LES results, in case of the lifted flame, show that the vortex core is sharply precessing at a given frequency. Phase averaging these results at the frequency of precession clearly indicates a counter-intuitive and unexpected presence of reverse flow going all the way through the flame apex and the bluff body tip. A simple one-dimensional flame stabilization model is applied to explain the bi-stable flame behaviour.


Author(s):  
B. Franzelli ◽  
A. Vié ◽  
B. Fiorina ◽  
N. Darabiha

Accurate characterization of swirled flames is a key point in the development of more efficient and safer aeronautical engines. The task is even more challenging for spray injection systems. On the one side, spray interacts with both turbulence and flame, eventually affecting the flame dynamics. On the other side, spray flame structure is highly complex due to equivalence ratio inhomogeneities caused by the evaporation process. Introducing detailed chemistry in numerical simulations, necessary for the prediction of flame stabilization, ignition and pollutant concentration, is then essential but extremely expensive in terms of CPU time. In this context, tabulated chemistry methods, expressly developed to account for detailed chemistry at a reduced computational cost in Large Eddy Simulation of turbulent gaseous flames, are attractive. The objective of this work is to propose a first computation of a swirled spray flame stabilized in an actual turbojet injection system using tabulated chemistry. A Large Eddy Simulation of an experimental benchmark, representative of an industrial swirl two-phase air/kerosene injection system, is performed using a standard tabulated chemistry method. The numerical results are compared to the experimental database in terms of mean and fluctuating axial velocity. The reactive two-phase flow is deeper investigated focusing on the flame structure and dynamics.


1983 ◽  
Vol 26 (220) ◽  
pp. 1753-1760 ◽  
Author(s):  
Tharwat Messiha Farag ◽  
Masataka ARAI ◽  
Masanori SHIMIZU ◽  
Hiroyuki HIROYASU

Author(s):  
Fernando Biagioli ◽  
Alessandro Innocenti ◽  
Steffen Terhaar ◽  
Teresa Marchione

Abstract Lean premixed gas turbulent flames stabilized in the flow generated by an industrial swirl burner with a central bluff body are experimentally found to behave bi-stable. This bi-stable behaviour, which can be triggered via a small change in some of the controlling parameters, for example the bulk equivalence ratio, consists in a rather sudden transition of the flame from completely lifted to well attached to the bluff body. This has impact on combustion dynamics, emissions and pressure losses. While several experimental investigations exist on this topic, numerical analysis is limited. The present work is therefore also of numerical nature, with a two-fold scope: a) simulation and validation with experiments of the bi-stable flame behaviour via Computational Fluid Dynamics (CFD) in the form of Large Eddy Simulation (LES) and b) analysis of CFD results to shed light on the flame stabilization properties. LES results, in case of the lifted flame, show that the vortex core is sharply precessing at a given frequency. Phase averaging these results at the frequency of precession clearly indicates a counter-intuitive and unexpected presence of reverse flow going all the way through the flame apex and the bluff body tip. The counter-intuitive presence of a lifted flame is explained here in terms of the phase averaged data which show that the flame apex is not placed at the centre of the spinning reverse flow region. It is instead slightly shifted radially outward where the axial velocity recovers to low positive values of the order of the turbulent burning rate. A simple one-dimensional flame stabilization model is applied to explain this peculiar flame behaviour. This model provides first an estimation of the flame radius of curvature in terms of axial velocity and turbulence quantities. This radius is therefore used to determine the total flux of reactants into the flame, given by an axial convection and a radial diffusion contributions. Subsequently the possibility of the flame positioned at the centre of the vortex is excluded based on the balance between this flux and the turbulent burning rate. A clear explanation of the mechanism leading to the sudden flame jump has instead not been identified and only some hypotheses are provided.


2020 ◽  
Vol 221 ◽  
pp. 201-211
Author(s):  
Stephen W. Grib ◽  
Tyler C. Owens ◽  
Michael W. Renfro

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