A laminar flamelet based NOx-radiation integrated modelling of turbulent non-premixed flame

Laminar flamelet model in its adiabatic form has been extended with radiation and NOx sub models to study the impact of radiation heat exchange on NOx predictions. Bluff-body stabilized CH4/H2 flame operating far from blow-off limit has been chosen as the test case. Radiation sub model is based on enthalpy defect concept while NOx model involves solving an additional transport equation for NO with a source term dependent on flamelet calculations. Turbulence closure has been achieved with a modified k-ε model. Detailed chemistry in the form of GRI2.11 has been adopted for the flamelet calculations. Numerical calculations have been carried out in a 2D finite-volume code with staggered grid arrangement. Comparison of predictions from adiabatic and non-adiabatic forms of flamelet model result in more or less similar predictions of mixing field, temperature and major species mass fractions with reasonably good agreement to measurements. However, the non-adiabatic model results in minor improvements to NO mass fraction predictions by reducing the extent of overprediction observed with adiabatic model. In order to achieve this effect, it has been found that variation in scalar dissipation rate should be considered in the non-adiabatic flamelet libraries.