COHERENT ANTI-STOKES RAMAN SCATTERING AND FLUORESCENT STUDY OF IGNITION AND COMBUSTION OF H2/O2 MIXTURES UPON PHOTODISSOCIATION OF O2 MOLECULES

The low-temperature ignition of H2/O2 mixture promoted by resonant laser radiation leading to the photodissociation of O2 molecules was studied experimentally. The experimental test bench involving the model combustion chamber, coherent anti-Stokes Raman scattering (CARS) and fluorescent diagnostic techniques was created for the experimental investigation of mixture ignition and combustion at conditions typical for gas turbine engines. For the production of chemically active oxygen atoms which initiate ignition in the H2/O2 mixture, the pulsed excimer ArF-laser emitting at a wavelength of 193 nm was employed. Complementary experiments on measuring the temperature and recording the emission of OH and OH* radicals indicate that it is possible to ignite the H2/O2 mixture with ф = 1-3 and P0 = 1-3 atm at a rather low temperature of ~ 700 K under the action of focused laser radiation (A = 193 nm) with the energy in the laser pulse of E = 30-150 mJ. The induction time varies in the range of 8-50 s depending on the laser energy and mixture parameters. Two-dimensional (2D) numerical simulation of ignition and combustion processes in the model combustion chamber was performed. A good agreement of calculation results with experimental data was obtained.