Structure, propagation, and stabilization of turbulent flames at aircraft engine conditions

点击翻译按钮获取中文摘要

Climate change poses an existential threat to life on earth. While most greenhouse gas (GHG) emitters have some possible alternatives; commercial, long-range aircraft engines powered by easily accessible liquid fuels of exceptional energy density, are yet to realize zero GHG-emission solutions. Such a situation underscores the urgent need to maximize efficiency, thereby reduce fuel consumption and emissions from aircraft engines. A step increase in efficiency can be achieved by correspondingly increasing the pressure and temperature in the combustor by increasing the overall pressure ratio. H2 is also being seriously considered as a zero GHG-emission aviation fuel. Either solution involves extreme engineering which behooves fundamental research inputs to ensure safe operation by enabling sustained, stable combustion, and flame stabilization without autoignition, flashback, or blowoff, which would be exacerbated in the extreme and widely varying engine thermodynamic states. The required measurements for turbulence modified flame speeds, flame structure, propagation modes, and blowoff mechanisms at such high pressure-temperature, engine operating conditions remain elusive. The proposed program will provide comprehensive measurements, scientific underpinnings, and modeling of local and global flame speeds and structure, flame propagation modes and regimes, and blowoff mechanisms of swirl-stabilized, turbulent premixed flames at aircraft engine conditions. To this end, experiments will be conducted at pressure up to 25 bar, inlet temperature up to 700 K, and at turbulence Reynolds numbers up to 68000 with both subcritical, supercritical jet fuels, and H2. Unique in Canadian universities and only very few of its kind around the world - the newly constructed High-Pressure Combustion Research Facility (HPCRF) at UTIAS enables the proposed research program. This will address some of the most profound questions of turbulent combustion, all the while serving design inputs for next-generation aircraft engines. Specifically, high-speed tomographic particle image velocimetry, chemiluminescence imaging, and the recently developed Flame Particle Tracking algorithms will be utilized to measure the local and global flame speeds. Turbulent diffusivity obtained by Lagrangian Fluid Particle Tracking at small scales, combined with high-speed laser induced fluorescence and Raman scattering will yield the turbulent flame structure. High fidelity computation aided experimental diagnostics will delineate the different flame propagation modes and corresponding regimes. Finally, H2-air turbulent combustion experiments and the insights gleaned will culminate into new combustors for zero GHG-emission aircraft engines. Alongside the far-reaching engineering impact, the highly qualified personnel trained in this program will have an unmatched research experience at HPCRF, which will prepare them to emerge as next-generation leaders of carbon-neutral aerospace propulsion.