Filtered Rayleigh Scattering With Polarization Separation for Fuel/Air Mixing in a Lean Premixed Prevaporized Combustor

The present work aims to demonstrate the potential of the Filtered Rayleigh Scattering (FRS) technique for fuel mixture fraction measurements in a Lean Premixed Prevaporized combustor designed for civil supersonic transport. For a more efficient mitigation of undesired scattering sources in the harsh combustor environments, an improved FRS methodology is implemented in conjunction with polarization separation technique. The fuel/air mixture images acquired in the combustor with this technique exhibit notable signal spikes in the flame boundary regions, which can be related to higher fuel concentration levels. In parallel to the measurements, complementary fuel/nitrogen mixture FRS signal simulations were carried out via the well-known Tenti S6 gas kinetic model at the same conditions as the measurements to help assess the performance of the modeling approach. The measurements were observed to significantly deviate from the model results, addressing the need for more accurate gas kinetic models. On the other hand, the measured FRS mixture signals exhibited a linear response to the increasing fuel amounts, which is an important aspect for mixing quantification using this technique. With these efforts, the new FRS methodology is believed to be successfully incorporated into mixing measurements in advanced future combustor concepts.