Visualisation of propane autoignition in a turbulent flow reactor using OH* chemiluminescence imaging

Autoignition of propane in air was visualised in a turbulent flow reactor using natural OH*-chemiluminescence imaging. The spatial and temporal development of autoignition kernels was studied in an optically accessible tubular section of the reactor. Kernel nucleation, movement and growth affected the location and movement of subsequent autoignition sites, and resulted in stagnation of the incoming flow and flashback. The autoignition delays of the reactants were measured under various conditions of temperature, pressure and equivalence ratio, relevant to micro gas turbines: Temperature T = 803–903 K, pressure p = 0.4–0.6 MPa, equivalence ratio ϕ = 0.2–0.6, mass flow rate of reactants mr = 8–21 g/s, with ignition delays τ between 191 and 498 ms. The effect of diluting the propane + air mixtures with CO2 was investigated for mole fractions of 0 < XCO2 < 0.1. An empirical correlation for the autoignition delays was developed for the aforementioned conditions, and values of activation energy were calculated on the basis of the experimental data. The ignition delay times were compared with the predictions of chemical kinetic models and experimental data previously reported in the literature.