Challenges and Opportunities for Laser Diagnostics to Make High-Pressure Aircraft Engines Clean and Efficient
14:45 - 15:15
Level 0 lecture hall between Al-Jazri and Al-Kindi (buildings 4 and 5)
Environmental concerns and legislative regulations are driving aircraft combustor manufacturers to meet more stringent pollutant emission standards while improving efficiency and reliability of future aero-engine combustors. In the case of small OPR engines, lean-premixed combustion has been introduced as a promising solution to significantly reduce NOx emissions. Too sharp a reduction in the NOx emission can, unfortunately, leads to a decline of the flame stability as well as an increase of CO and HC emissions. To obtain a better comprehension of the physical processes that govern pollutant emissions, a recent educational and research industrial chair "Powering the future with Clean and Efficient Aero-engines" (PERCEVAL) has been initiated by CORIA (COmplexe de Recherche Interprofessionel en Aérothermochimie) in close cooperation with the French motorist SAFRAN and the French National Research Agency (ANR) to assess the optimization of combustion efficiency and reduction of pollutant emission of innovative staged lean combustors.
The current work aims to study an innovative Lean premixed fuel injection system developed by SAFRAN. To investigate its performances, parametric experiments were conducted in a single-sector high-pressure optical combustion chamber. This test facility is equipped with large optical accesses to perform laser-based measurements under relevant operating conditions (pressure: 0.1-2.0 MPa, preheated air temperature: 300-900 K, air flow rate: 0-300 g/s). The test rig runs with commercial Jet-A1 kerosene fuel. Simultaneous measurements of Planar-Laser induced Fluorescence (PLIF) applied to OH and kerosene were first performed at the outlet of the LP injector for various operating conditions (up to 670 K and 1.8 MPa). Measurements demonstrate the potential of PLIF to measure simultaneously the flame structure and the spatial fuel distribution in flight conditions. In particular, a discrimination of fluorescence of mono- and di-aromatics contained in kerosene made it possible to quantitatively measure air-to-fuel ratio distribution. Good spatial correlation between the distribution of kerosene vapor and the flame front location also permits to quantify the evolution of the combustion efficiency with pressure. Then, high-speed PIV measurements were performed in the same conditions in order to study the aerodynamic field in nonreactive and reactive conditions. The experiments were continued by performing simultaneous PLIF measurements of OH and NO. A methodology adopted to perform quantitative 2D NO concentration distributions ensuring a minimal detection of few ppm of NO as well as minor interferences with potential presence of O2 and kerosene was developed. Data measurements on NO, OH, kerosene and velocity were then analyzed and correlated. For instance, it has been highlighted that the aerodynamic flowfield has a large impact on the formation of NO in such flows. Furthermore, the data collected in this study also provide a series of challenging test-cases for the validation of numerical codes for liquid fuel combustion in high pressure conditions and pollutant formation.