Modelling of flameless combustion using large eddy simulation

The challenge of achieving a clean and stable combustion in modem power plants or aero engines leads to develop new technologies and new combustors. Pioneer work on 'flameless' combustion has shown the great potential of such a technology for meeting modem requirements in term of safety and. low emissions. The idea behind this technique is to ensure low emissions by operating at very low fuel/air equivalence ratio but with high preheating to stabilize the combustion. In addition, a careful design of the combustor should ensure that fresh gases are diluted by hot exhaust gases. The result is a distributed but efficient oxidation region. This paper presents a new efficient model for simulating 'flameless' oxidation. The model is based on Large Eddy Simulation (LES) ensuring an accurate description of the mixing. In addition, a 'low-cost' technique for coupling the LES code with some complex chemistry is presented. This approach was used for simulating a reacting jet close to the 'flameless' regime. The simulation showed the capability of the present LES tool for understanding the flow dynamics and improving the design of 'flameless' combustors