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

气候变化对地球上的生命构成了生存威胁。虽然大多数温室气体(GHG)排放者都有一些可能的替代方案；但由易于获得的具有极高能量密度的液体燃料提供动力的商用远程飞机发动机尚未实现温室气体零排放解决方案。这种情况突出表明，迫切需要最大限度地提高效率，从而减少飞机发动机的燃油消耗和排放。通过增加总压比，相应地提高燃烧室内的压力和温度，可以实现效率的逐步提高。氢气也被认真考虑为零温室气体排放的航空燃料。无论哪种解决方案都涉及到极端工程，这需要基础研究投入，以确保安全运行，实现持续、稳定的燃烧和火焰稳定，而不会自燃、闪回或喷出，而这些都会在极端和变化很大的发动机热力学状态下加剧。在如此高的压力-温度下，发动机运行条件下，湍流修正的火焰速度、火焰结构、传播模式和喷吹机制所需的测量仍然难以实现。拟议的计划将提供全面的测量、科学依据和对局部和全球火焰速度和结构、火焰传播模式和制度以及飞机发动机条件下涡流稳定的湍流预混火焰的喷出机制的建模。为此，将在压力高达25bar，入口温度高达700K，湍流雷诺数高达68000的情况下，对亚临界、超临界喷气燃料和氢气进行实验。这在加拿大的大学中是独一无二的，在世界各地的同类大学中也很少--UTIAS新建的高压燃烧研究设施(HPCRF)使拟议的研究计划得以实施。这将解决湍流燃烧的一些最深刻的问题，同时为下一代飞机发动机提供设计投入。具体地说，将利用高速层析粒子图像测速仪、化学发光成像和最近开发的火焰粒子跟踪算法来测量局部和全局火焰速度。通过小尺度拉格朗日流体粒子跟踪获得的湍流扩散率，与高速激光诱导的荧光和拉曼散射相结合，将产生湍流火焰结构。高保真计算辅助实验诊断将描绘出不同的火焰传播模式和相应的区域。最后，氢空气湍流燃烧实验和收集到的见解将最终形成用于零温室气体排放的飞机发动机的新燃烧室。除了深远的工程影响外，在该项目中培训的高素质人员将在HPCRF拥有无与伦比的研究经验，这将使他们做好准备，成为碳中性航空推进的下一代领导者。

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.