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首页> 外文期刊>Flow, turbulence and combustion >Effects of Fuel Lewis Number on Localised Forced Ignition of Globally Stoichiometric Stratified Mixtures: a Numerical Investigation
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Effects of Fuel Lewis Number on Localised Forced Ignition of Globally Stoichiometric Stratified Mixtures: a Numerical Investigation

机译：Effects of Fuel Lewis Number on Localised Forced Ignition of Globally Stoichiometric Stratified Mixtures: a Numerical Investigation

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摘要

The influences of fuel Lewis number L e (F) on localised forced ignition of globally stoichiometric stratified mixtures have been analysed using three-dimensional compressible Direct Numerical Simulations (DNS) for cases with L e (F) ranging from 0.8 to 1.2. The globally stoichiometric stratified mixtures with different values of root-mean-square (rms) equivalence ratio fluctuation (i.e. I center dot (')= 0.2, 0.4 and 0.6) and the Taylor micro-scale l (I center dot) of equivalence ratio I center dot variation (i.e. l (I center dot) /l (f) = 2.1, 5.5 and 8.3 with l (f) being the Zel'dovich flame thickness of the stoichiometric laminar premixed flame) have been considered for different initial rms values of turbulent velocity u ('). A pseudo-spectral method is used to initialise the equivalence ratio variation following a presumed bi-modal distribution for prescribed values of I center dot (') and l (I center dot) /l (f) for global mean equivalence ratio aOE (c) I center dot >=1.0. The localised ignition is accounted for by a source term in the energy transport equation that deposits energy for a stipulated time interval. It has been observed that the maximum values of temperature and the fuel reaction rate magnitude increase with decreasing L e (F) during the period of external energy deposition. The initial values of L e (F) , u (')/S (b(I center dot=1)), I center dot (') and l (I center dot) /l (f) have been found to have significant effects on the extent of burning of the stratified mixtures following localised ignition. For a given value of u (')/S (b(I center dot=1)), the extent of burning decreases with increasing L e (F) . An increase in u (') leads to a monotonic reduction in the burned gas mass for all values of L e (F) in all stratified mixture cases but an opposite trend is observed for the L e (F) =0.8 homogeneous mixture. It has been found that an increase in I center dot (') has adverse effects on the burned gas mass, whereas the effects of l (I center dot) /l (f) on the extent of burning are non-monotonic and dependent on I center dot (') and L e (F) . Detailed physical explanations have been provided for the observed L e (F) , u (')/S (b(I center dot=1)), I center dot (') and l(phi) /l(f) dependences.

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