Experimental turbulence assessment of the reactive flow field in a flameless combustion chamber operating in three regimes

This paper presents the study of the flow field in a flameless combustion chamber using PIV for different combustion regimes. Three representative reactive flow test cases from the literature were chosen to validate the experimental test bench and measurement techniques. The streamlines of mean velocity magnitude indicated the main recirculation structure in the combustion chamber, which is responsible for the dilution of the fresh reactants with the combustion products in the reactive flow. Measured normalized Reynolds stress components indicate higher turbulence intensity for the flameless case when compared to the conventional regime. The Large-eddy PIV methodology was applied for the first time in a reactive flow under flameless combustion regime to estimate the turbulent kinetic energy dissipation rate, making it possible to calculate the Kolmogorov time scale based on the estimated epsilon. A discussion on the fundamentals of the turbulent combustion for the three regimes is presented by an analysis of the turbulent combustion diagram based on the experimental results. The conven-tional combustion regime develops with the thickened-wrinkled flame structure since its Karlovitz number is 1<Ka<100 . The flameless case, with Ka>100 , indicates a higher interaction of the reaction zone structure with the smaller scales of turbulence compared to the conventional regime.