Study of an Ignition Infra-Red Laser Cell – ECLAIR

This project belongs to thematic 2, fluids and structures, subject 2.2.3. “propulsion and energetic flows” of the call and correspond to priority “reactive flow control which ignition is a crucial issue”.
This project is dedicated to the investigation of laser ignition of two-phase flows in aeronautical combustion chambers. Ignition and specially altitude re-ignition is a crucial issue for the jet-engine manufacturers because it determines the combustion chamber volume. The availability of a high-performance and reliable igniter is a key asset for the manufacturers. The project is focused on the development of an innovating laser source able to ignite a kerosene/air two-phase flow produced by an aeronautical injection system under altitude conditions (-40°C, 0.5 atm.). this device will be developed by LOMA with the partnership of the Fibercryst company. It will produce, at at a 500 Hz frequency, 1 to 2 nanosecond quasi-gaussian (M2<2) pulses centred on 1064 nm wavelength, with an energy up to 10 mJ. These pulses, focused on a point in a combustion chamber, will create locally a plasma wich will produce a burning kernel which will ignite the chamber. Depositing the energy et high frequency in the flow, we should deposit it more efficiently for ignition. indeed, with present spark-plugs, the literature show that at most 20 to 30% of the energy is used for ignition. In parallel, optical diagnostics will be developed and coupled to accurately characterise the energy deposited in the flow by the focused laser beam, and the chemical species produced during the breakdown. The deposited energy is badly known but is a crucial entry data for the CFD simulations of the ignition of a combustion chamber. A better knowledge of this point would improve the predictive ability of the CFD solvers which could be used afterwards by the jet-engine manufacturers to design their chamber according to ignition. Finally, the laser source will be tested on the MERCATO experiment, the French benchmark for ignition in aeronautical propulsion under actual conditions. The performances of the new igniter will be measured with previously developed optical diagnostics and compared with those of a classical spark igniter.