Session: 04-43 Hydrogen Emissions III

Submission Number: 177481

Experimental Investigation of Pressure Influence on a Swirled Stabilized Premixed Hydrogen-Air Flame for Aeronautical Applications Using Optical Diagnostics 

Reducing the environmental impact and dependence on carbon-based fuels of aviation sector is vital to ensure its long-term survival. One way for achieving this objective is to develop new aircraft architectures including technology breaks. A promising solution for short-to-medium-haul flights is to replace kerosene with hydrogen combustion. This switch in fuel leads to significant changes in the architecture of the combustion chamber. Whether optimising existing concepts or developing new ones, combustion chamber design requires a detailed understanding of the dynamics of reactive flows. Due to hydrogen’s large flame speed, low diffusivity and large flammability range, H₂ flames are prone to flashback and could be difficult to stabilize, thus reducing the operability range. When operated in lean premixed conditions, H₂ flames are also subject to thermo-diffusive instabilities. Besides, due to the slightly higher adiabatic flame temperature and differences in chemistry-turbulence interactions, mitigating NO_x emissions remain challenging. Therefore, in order to guarantee optimal operation over a wide range of operability, it is necessary to have a detailed understanding of the operation of the injection system and the flame stabilisation mechanisms. This study aims to report a novel injector design of premixed ultra-low NOx swirl-stabilized H₂-air flame. This concept has been tested on the ONERA high pressure – high temperature MICADO test rig. Various operating conditions have been explored up to 19 bar and global equivalent ratio between 0.2 and 0.3. Flame dynamics and topology have been characterised using high-speed OH* chemiluminescence imaging and OH-PLIF. NO_x emissions and combustion efficiency are measured by exhaust gases sampling. Results show very low NO_x levels for all tested operating conditions. Though fully premixed conditions are limited due to flashback phenomena, the introduction of a pilot injection demonstrates the capacity to extend the safe operation range of such technology, without degrading NO_x emissions or combustion efficiency.

Presenting Author: Guillaume Pilla ONERA

Presenting Author Biography: Guillaume Pilla has obtained his PhD in 2008. Among the scientific fields he has explored during his career, he has developed solid expertise in combustion in propulsion systems, as well as in optical metrology.

Authors:

Guillaume Pilla ONERA
Sylvain Petit ONERA
Jiangheng Ruan ONERA
Axel Vincent-Randonnier ONERA