Abstract:
Most of the energy produced and used in the world comes from fossil fuels. The combustion
of these fuels cause the emission of significant quantities of greenhouse gases as well as
different types of pollutants such as CO, NOx and other pollutant particles. The addition of
hydrogen in hydrocarbons appears to be a promising way to reduce these emissions. Indeed, it
has been demonstrated by several authors that the addition of certain quantities of hydrogen in
hydrocarbons improves combustion performance (improves flame stability, pollution, etc). As
hydrogen is a good energy carrier, its addition to hydrocarbons could be a good way for the
introduction of renewable energies.
In this work, we focus on the effect of hydrogen on two turbulent diffusion flames methane.
The first flame is obtained with a burner coaxial configuration were the jet of fuel is in the
center. The second flame is produced by a coaxial burner with a pilot flame. The role of the
pilot flame is to maintain the flame. For the first configuration we compared the performance
of three turbulence models (the standard k-ε, the RSM model and the modified k-ε) and the
performance of two detailed kinetic schemes, the GRI 2.11 and the GRI 3. We do vary the
volumetric fraction of hydrogen from 0 to 50% for this flame. Attention was given, here, to
the hydrogen effect on the flame structure, the heat power produced, as well as to the effect on
the production of polluting gases such as nitric oxide and carbon monoxide.
For second case, we simultaneously vary the initial temperature, the ambient pressure and the
hydrogen fraction. The initial temperature is varied from 290 to 600 K, the pressure of 1 to 10
atm and hydrogen volumetric fraction of hydrogen from 10 to 30%.
We have noted that the addition of hydrogen in both cases causes a reduction of the radial and
axial expansion of the flame with reduction of the reaction zone; It also causes an increase of
the combustion temperature, which induced an increase in nitric oxide emissions.
The increase in pressure causes a narrowing of the flame and reduces the effect of hydrogen.
Finally, increasing the initial temperature causes an increase in the fuel consumption rate.
