Session: Student Poster Competition

Submission Number: 186529

Experimental Study by Advanced Optical Diagnostics of a High-Pressure Rich Burn – Quick Mix – Lean Burn Lab-Scale Combustion Chamber 

The Rich burn - Quick mix - Lean burn (RQL) concept is a staged combustion process that exhibits a fuel-rich primary region to ensure a stable flame in all operating conditions. This rich flame which promotes soot, Unburned HydroCarbons (UHCs) and CO formation is then quickly fed by an injection of a large quantity of air in order to decrease the flame temperature and dilute the burnt gases to finally generate a lean combustion providing an oxidation of soot and a lower temperature that reduces the NOx production. Various experimental research studies have been focused on analyzing the potential of this combustion concept, but most of them were performed at atmospheric conditions. Following recent advances in high-pressure RQL combustion, the aim of this poster is to examine, by means of advanced optical diagnostics, a new laboratory-scale RQL burner equipped with a new-generation double-circuit fuel injection system and large optical accesses enabling a simultaneous investigation into the three RQL areas of the physico-chemical mechanisms involved in soot production / oxidation and NOx formation under realistic high-pressure / high-temperature operating conditions encountered in helicopter combustors. The RQL burner is integrated into the visualization module of a high-pressure combustion facility fed with multi-component liquid fuels (kerosene and Sustainable Aviation Fuels). It was designed by means of iterative Large-Eddy Simulations (LES) to fulfill various constraints such as a reactive zone height of  ̴ 40 mm comparable of that of a helicopter combustor sector, an overall pressure drop of  ̴ 3-4 %, an optimal distribution of fuel / air mass flowrates, a high combustion efficiency of  ̴ 100 % at the outlet of the combustion chamber, a good thermal resistance of the metallic walls and optical windows, as well as the ability to pass laser sheets through the different RQL areas for optical measurements.

The experimental study is conducted with liquid kerosene (Jet A-1) at a pressure of 8.5 bar and an air inlet preheating temperature of 600 K. In order to visualize the heat release regions, OH* chemiluminescence is initially performed and highlights the ability to detect well-separated RQL areas. In the Rich-burn area (R), a strong and spatially extended OH* signal is observed, indicating intense chemical activity and a well-stabilized flame. Following the Quick-mix (Q) of the dilution jets with the rich flame, a fast drop in the OH* signal is observed in the Lean-burn area (L), which indicates efficient quenching and dilution, leading then to limited chemical activity and a significant reduction in soot particles through oxidation. In order to obtain a better analysis of the combustion processes within the RQL areas, various advanced laser-based diagnostics are implemented in the median plane of the combustion chamber. A coupling of Planar Laser-Induced Fluorescence on the OH radical (OH-PLIF), liquid and vapor phases of kerosene fuel (kerosene-PLIF) and the NO pollutant (NO-PLIF) is performed to simultaneously record the 2D spatial distributions of these scalar parameters for providing a correlated description of the flame topology, the fuel consumption, as well as the NO formation and reduction processes. The 2D distribution of the soot volume fraction in the RQL areas is also recorded by Planar Laser-Induced Incandescence (PLII) which is coupled with OH-PLIF and kerosene-PLIF to correlate soot production and oxidation with the spatial distributions of OH and kerosene. Furthermore, high-speed Particle Imaging Velocimetry (PIV) is performed to record the 2D spatial distribution of the velocity field at the outlet of the injection system. This experimental study clearly demonstrates the impact of RQL combustion on the reduction of NOx and soot pollutant emissions while preserving flame stability.

Presenting Author: Afaf Karrouk CORIA CNRS UMR 6614 - SAFRAN HELICOPTER ENGINES

Presenting Author Biography: I am a 3rd year PhD Student with the CORIA French Research laboratory and SAFRAN HELICOPTER ENGINES. My work focuses on the study, by means of advanced optical diagnostics and Large-Eddy Simulations (LES), of the Rich burn - Quick mix - Lean burn (RQL) combustion under realistic high-pressure / high-temperature operating conditions encountered in helicopter combustors.

Authors:

Afaf Karrouk CORIA CNRS UMR 6614 - SAFRAN HELICOPTER ENGINES
Maxim Kuvshinov CORIA CNRS UMR 6614
Alexis Vandel CORIA CNRS UMR 6614
Benjamin Quevreux CORIA CNRS UMR 6614
Clément Brunet SAFRAN HELICOPTER ENGINES
Stéphane Richard SAFRAN HELICOPTER ENGINES
Gilles Cabot CORIA CNRS UMR 6614
Frédéric Grisch CORIA CNRS UMR 6614