Direct numerical simulation of lean hydrogen/air auto-ignition in a constant volume enclosure

2013 ◽  
Vol 160 (9) ◽  
pp. 1706-1716 ◽  
Author(s):  
Rixin Yu ◽  
Xue-Song Bai
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Constant Volume ◽  
Auto Ignition

Three-dimensional direct numerical simulation of a turbulent lifted hydrogen jet flame in heated coflow: a chemical explosive mode analysis

2010 ◽  
Vol 652 ◽  
pp. 45-64 ◽  
Author(s):  
T. F. LU ◽  
C. S. YOO ◽  
J. H. CHEN ◽  
C. K. LAW
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Near Field ◽  
Three Dimensional ◽  
Mode Analysis ◽  
Scalar Dissipation ◽  
Complex Flows ◽  
Jet Flame ◽  
Auto Ignition ◽  
Grid Points

A chemical explosive mode analysis (CEMA) was developed as a new diagnostic to identify flame and ignition structure in complex flows. CEMA was then used to analyse the near-field structure of the stabilization region of a turbulent lifted hydrogen–air slot jet flame in a heated air coflow computed with three-dimensional direct numerical simulation. The simulation was performed with a detailed hydrogen–air mechanism and mixture-averaged transport properties at a jet Reynolds number of 11000 with over 900 million grid points. Explosive chemical modes and their characteristic time scales, as well as the species involved, were identified from the Jacobian matrix of the chemical source terms for species and temperature. An explosion index was defined for explosive modes, indicating the contribution of species and temperature in the explosion process. Radical and thermal runaway can consequently be distinguished. CEMA of the lifted flame shows the existence of two premixed flame fronts, which are difficult to detect with conventional methods. The upstream fork preceding the two flame fronts thereby identifies the stabilization point. A Damköhler number was defined based on the time scale of the chemical explosive mode and the local instantaneous scalar dissipation rate to highlight the role of auto-ignition in affecting the stabilization points in the lifted jet flame.

Direct numerical simulation of ignition front propagation in a constant volume with temperature inhomogeneities

2006 ◽  
Vol 145 (1-2) ◽  
pp. 128-144 ◽  
Author(s):  
Jacqueline H. Chen ◽  
Evatt R. Hawkes ◽  
Ramanan Sankaran ◽  
Scott D. Mason ◽  
Hong G. Im
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Front Propagation ◽  
Constant Volume ◽  
Ignition Front

Direct numerical simulation of ignition front propagation in a constant volume with temperature inhomogeneities

2006 ◽  
Vol 145 (1-2) ◽  
pp. 145-159 ◽  
Author(s):  
Evatt R. Hawkes ◽  
Ramanan Sankaran ◽  
Philippe P. Pébay ◽  
Jacqueline H. Chen
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Front Propagation ◽  
Constant Volume ◽  
Ignition Front

Three-dimensional direct numerical simulation of a turbulent lifted hydrogen jet flame in heated coflow: flame stabilization and structure

2009 ◽  
Vol 640 ◽  
pp. 453-481 ◽  
Author(s):  
C. S. YOO ◽  
R. SANKARAN ◽  
J. H. CHEN
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Heat Release ◽  
Three Dimensional ◽  
Flame Stabilization ◽  
Flux Analysis ◽  
Jet Flame ◽  
Lifted Flame ◽  
Auto Ignition ◽  
Lagrangian Tracking

Direct numerical simulation (DNS) of the near field of a three-dimensional spatially developing turbulent lifted hydrogen jet flame in heated coflow is performed with a detailed mechanism to determine the stabilization mechanism and the flame structure. The DNS was performed at a jet Reynolds number of 11,000 with over 940 million grid points. The results show that auto-ignition in a fuel-lean mixture at the flame base is the main source of stabilization of the lifted jet flame. A chemical flux analysis shows the occurrence of near-isothermal chemical chain branching preceding thermal runaway upstream of the stabilization point, indicative of hydrogen auto-ignition in the second limit. The Damköhler number and key intermediate-species behaviour near the leading edge of the lifted flame also verify that auto-ignition occurs at the flame base. At the lifted-flame base, it is found that heat release occurs predominantly through ignition in which the gradients of reactants are opposed. Downstream of the flame base, both rich-premixed and non-premixed flames develop and coexist with auto-ignition. In addition to auto-ignition, Lagrangian tracking of the flame base reveals the passage of large-scale flow structures and their correlation with the fluctuations of the flame base. In particular, the relative position of the flame base and the coherent flow structure induces a cyclic motion of the flame base in the transverse and axial directions about a mean lift-off height. This is confirmed by Lagrangian tracking of key scalars, heat release rate and velocity at the stabilization point.

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