Comparison of flameless combustion and conventional combustion

Flameless combustion is a mild combustion mode under low oxygen dilution conditions, which is characterized by low reaction rate, low local heat release, uniform heat flow distribution, small temperature difference in the furnace, low peak combustion temperature, minimal noise and low NOX generation.

In the conventional combustion mode, the concentration of reactants before entering the reaction zone is high and the temperature is low, while in the flameless combustion mode, the concentration of reactants before entering the reaction zone is low and the temperature is high. In the flameless combustion process, the diffusive mixing of air and fuel is retarded by spraying high temperature preheated air and fuel into the combustion chamber through different nozzles, forming a strong flue gas reflux and mixing violently with fuel and air. As the concentration of reactants decreases in flameless combustion, the reaction area expands, the fuel burns in a high temperature and low oxygen atmosphere, the reaction occurs in a wide area, sometimes even filling the whole chamber, the flame volume expands exponentially, the flame front disappears, the temperature distribution of the whole chamber is uniform, the volumetric heat load of the chamber is increased, the radiation heat transfer is enhanced, and the local high temperature and high oxygen zone, which appears in the traditional combustion method, no longer occurs. Thus, the NOX concentration is controlled at a low level.