Fuel Droplet Sizing in a Reacting Lean Prevaporized Premixed Combustor Environment

A key challenge in the development of engines for civil supersonic transport is reducing emissions. One promising topology for combustor designs is lean prevaporized premixed (LPP) systems. While the injectors for these systems are designed to vaporize the fuel, droplets may still present at low temperature and pressure conditions. In this work, we measure the fuel droplets generated by injectors in reacting LPP combustors using digital in-line holography, digital off-axis holography, and high magnification spoiled cavity back light imaging techniques. While holography images are obscured by intense density gradients, the spoiled cavity back light imaging methods are able to successfully capture droplet images. Results show that droplet sizes down to 9 µm can be measured successfully, enabling the comparison of fuel atomization at non-reacting and reacting conditions. By studying the droplet size distributions at different operating conditions, new injector and LPP combustor designs can be developed for future propulsion applications.