EXPERIMENTAL INVESTIGATION WITH OPTICAL DIAGNOSTICS OF A LEAN-PREMIXED AERO-ENGINE INJECTION SYSTEM UNDER RELEVANT OPERATING CONDITIONS

A Lean-Premixed (LP) aero-engine injection system was experimentally studied using optically-based measurements. Experiments were conducted under relevant operating conditions up to 1.38 MPa and using commercial kerosene as fuel. First of all, the structure of the reaction zone and the flame length into the combustion chamber have been studied with CH* chemiluminescence. It is observed from the data measurements that combustion can produce two types of flames, a V-shaped flame in which combustion is stabilized a few mm downstream from the injector and a tulip flame in which combustion is developing inside the injection system. The flame is found to be shorter and more confined when increasing the pressure. To complement this study, experiments were also performed using the OH-PLIF measurement technique. Data processing of the absorption of OH fluorescence signals along the laser propagation allowed the determination of the absolute distribution of OH concentration without any calibration of the OH fluorescence signals. The obtained values are in agreement with estimated premixed adiabatic chemical equilibrium results. Furthermore, the flame front location and its structure were captured from gradient based filtering operations on OH-PLIF signals. Finally, pollutant emissions were also measured with an exhaust gas sampling probe positioned downstream from the combustor outlet. It has been found that NOx emission increases with Fuel Air Ratio (FAR) and pressure whereas CO exhibits an inverse trend.