The main objective of the European research project CHAiRLIFT is to assess an innovative combustor concept capable to achieve an ultra-lean, low NOx, operation of future engines. The innovative concept has the potential to achieve the long term European emissions goals for aircraft engines as set in the “Flightpath 2050” by Advisory Council for Aviation and Research in Europe. For addressing this issue, a new concept of combustors is proposed in the CHAiRLIFT project by combining of the following features:
The first is to adopt “low swirl” lean lifted spray flames which feature a high degree of premixing and consequently significantly reduced NOx emissions. Inherent characteristics of such flames are the strongly reduced risk of flashback. However, such lifted flames bear the risk of lean blow out at some operating conditions. Therefore, the lean lifted spray flames are combined with an alternative approach to standard flame piloting. Stable and safe operations of the combustor are ensured by the interaction of adjacent flames in circumferential direction within the annular combustion chamber. This requires tilting of the axis of the flames relative to the axis of the machine. This design is called Short Helical Combustor (SHC). It has the advantage that no extra pilot flame is required which may produce additional NOx emissions. Additional benefits are the reduced length of the combustor. Most importantly, the turning angle of the NGV can be reduced resulting into a smaller number of NGV and hence reduced cooling air requirement.
The project partners of CHAIRLIFT are the University of Florence (coordinator), Karlsruhe Institute of Technology, University of Salento and the University of Rouen.
The Enlger-Bunte-Institute of Karlsruhe Institute of Technology is conducting the experimental investigations on a multi burner array with and without inclination. The Lean Blow Out limits (LBO) at different operating conditions (air inlet temperature, relative air pressure drop) will be determined, the velocity field will be measured by Laser optical methods as Particle Image Velocimetry (PIV) and the flame shape by e.g. OH*-chemiluminescence. Furthermore, measurements of local mixture fraction and temperature by probe measurements will be applied to enhance the understanding of the stabilization mechanism. Moreover, to explore further NOx reduction capabilities of the concept, an advanced LBO active control will also be tested by combining ion sensor probe and nano-plused plasma-assisted combustion in cooperation with the University of Salento.