Ignition and early stage combustion of H2–O2 mixture upon the photodissociation of O2 molecules by UV laser radiation: Experimental and numerical study

Abstract

The ignition and combustion of H2O2 mixture upon the photodissociation of O2 molecules by the resonance laser radiation with a wavelength of 193 nm are studied both experimentally and computationally. The experimental test bench equipped with CARS and fluorescent diagnostic techniques was created and applied for the measurement of the induction time and velocity of combustion front during laser-induced ignition of the H2O2 mixture in the model chamber. The complementary experiments on measuring the temperature and recording the emission of OH(X2Π) and OH(A2Σ+) radicals indicate that it is possible to ignite the H2O2 mixture with ϕ= 1–3 and P0 = 1–3 atm at a rather low temperature ∼700 K, which is below the autoignition temperature, under the action of focused laser radiation (λ= 193 nm) with the energy in the pulse of ∼25–150 mJ. And the induction time is rather small and varies in the range of 8–50 µs depending on mixture parameters and laser pulse energy. The analysis of ignition and combustion processes in the H2O2 mixture under the action of resonance laser radiation is carried out on basis of two-dimensional numerical simulation with the use of the detailed kinetic mechanism of H2 oxidation supplemented by the set of reactions describing the formation of electronically excited radicals OH(A2Σ+). A special methodology for the calculation of the radiation absorption and determination of oxygen atoms concentration along the laser beam path was applied. The elaborated model allows us to describe the experimentally measured data for the induction time, the velocity of the combustion front, the space-time distribution of the OH radicals in the ground and excited states, and the temperature evolution in the focal region of the initiating laser radiation.