Optical Diagnostics Used at Onera to Characterize Turbulent Reactive Flows and to Validate Aero- and Rocket Engine Combustor Modeling

The reactive flows encountered in combustion systems are very complex and varied. Optical diagnostics have been a great help in improving our understanding of the physics of combustion because they can give information on the core of the flow without perturbing it. Optical measurements are essential for validating the CFD codes for reactive flows. These techniques have undergone continuous improvement so that we can now obtain 2D visualizations and simultaneous measurements of different quantities with high resolution on combustor systems operating in tough conditions of pressure and temperature. Examples of such measurements are given in this article; they concern industrial combustors as well as burners dedicated to basic research. The article also compares numerical simulations to these measurements. Optical diagnostics still need further improvements, for instance, so that they can operate in dense sprays or characterize soot particles accurately. Higher data acquisition frequency is also needed in order to better understand and remove combustion instabilities.