Session: 04-25: Novel Combustors I

Paper Number: 102769

102769 - Experimental Study of a Low Nox and Soot Injection System for Spinning Combustion Technology: Characterization of Soot and No Formation Under Realistic Operating Conditions by Laser Diagnostics 

Global air traffic is expected to grow at an average rate of ~ 5% per year during the next 20 years. Hence, severe reductions of fuel burn and pollutant emissions are required for preserving our environment and ensuring the sustainability of the aviation industry. In order to mitigate the detrimental impact of the higher operating pressure and temperature on pollutant emissions, lean combustors are currently developed by engine manufacturers. Meeting the regulations formulated by the international organizations will be possible by pushing these combustion technologies towards their limits regarding both efficient operability, and their ability to reduce pollutant emissions. In the context of these technologies, the French manufacturer, Safran Helicopter Engines, has developed and patented a spinning combustion technology (SCT) for the novel generation of engines. This solution has already been adopted in real propulsion systems like the ARANO engine, which exhibits CO₂ reduction of ~15% compared to the previous engine generation. Spinning combustion also allows improved ignition and blow-off capabilities as well as combustor weight reduction, without compromising turbine and combustor lifetimes. Nevertheless, in addition to these major improvements, a key point of SCT engines remains to be addressed: the low NOx and soot particle emissions.

The aim of this work is to propose and implement a development pathway for upgraded low-emission spinning combustion injection systems for the SCT, including the design and the experimental study of these injectors by accurately quantifying NOx and soot production. The research consists in the application of various laser diagnostics to fully analyze the physical and chemical mechanisms interacting mutually within the combustor (spray injection, evaporation, air/fuel mixing, combustion efficiency, pollutants…). The originality of the work lies in the wish to systematically record simultaneous temporally-resolved spatial distributions on various scalar quantities thanks to the combination of various laser diagnostics. In the current paper, a complete description of the experimental results obtained on a low-NOx multi-point swirl injection system build by additive manufacturing is presented. The injector is mounted in a high-pressure optical combustion facility running under conditions similar to those of aeronautical engines (up to 14 bar). The effects of fuel atomisation and air/fuel mixing on the flame structure and NO formation were investigated first by performing simultaneous planar laser-induced fluorescence measurements on OH, kerosene and NO at the outlet of the injector fuelled by Jet-A1. Results show that NO produced close to the flame front, is subsequently transported into the internal recirculation zone (IRZ). The resultant mixing of NO with the high-temperature exhaust gases in IRZ then leads to a homogeneous radial distribution of NO at the flame tip. Complementary measurements of soot volume fraction by laser-induced incandescence combined with OH-PLIF and kerosene-PLIF were also performed. Results reveal a strong correlation between the time-averaged distributions of OH, soot volume fraction and kerosene. The flame topology presents an asymmetry arising from the design of the injection system which has a severe impact on the radial distribution of inlet air at the injector outlet. An analysis of the consecutive instantaneous distributions of these physical quantities also showed large spatio-temporal dynamics represented by high variabilities of soot volume fraction intensities per event and location. Intermittency of these soot events in the instantaneous images can be interpreted by exploring the large correlations between the sporadic areas of soot particles and the region of appearance both of evaporated kerosene (soot formation) and OH (soot oxidation). Furthermore, soot formation and NO production were also conditioned by the combustion chamber pressure and the equivalence ratio. This research could be considered as an exemplary application of laser diagnostics to understand the NOx and soot formation occurring in aero-engine combustors.

Presenting Author: Andrei-Silviu Milea INSA Rouen Normandie - CORIA

Presenting Author Biography: Andrei-Silviu Milea is graduated from the Engineering School “INSA Rouen Normandie” in Energetics and Propulsion" (France). He also spent one year in the Cranfield University to obtain a specialization in gas turbines for aeronautical applications. He has presently a position of Phd student involved in an experimental activity focused on the "Experimental investigation of innovative Low NOx / low soot injection systems for spinning combustion technology using advanced laser diagnostics".

Authors:

Andrei-Silviu Milea INSA Rouen Normandie - CORIA
Aurélien Perrier INSA Rouen Normandie - CORIA
Marcos Caceres INSA Rouen Normandie - CORIA
Alexis Vandel INSA Rouen Normandie - CORIA
Gilles Godard INSA Rouen Normandie - CORIA
Fabien Renard GDtech France S.A.S.
Patrick Duchaine Safran Helicopter Engines
Stephane Richard Safran Helicopter Engines
Gilles Cabot University of Rouen - CORIA
Frédéric Grisch INSA Rouen Nrmandie - CORIA