ENERGIZE: Adjoint-based and additive manufacturing-enabled optimization of hydrogen combustion systems

绿色氢燃烧将在向可再生能源过渡中发挥关键作用。然而，氢的燃烧给燃气轮机界带来了新的重大挑战。首先，燃烧室的火焰稳定对燃气轮机的安全运行是渐进的，但天然气燃烧器中使用的最先进的解决方案不能转移到含氢量高的燃料上。其次，由于缺乏实验数据和详细的数值模拟，湍流结构与氢火焰锋面的相互作用还不是很清楚。然而，这些湍流-火焰相互作用与实际配置高度相关。一方面，它导致火焰片的波纹，以允许高的全球消耗率。另一方面，它会导致热点诱导的NOx排放，热声不稳定和火焰噪声。因此，一个主要的挑战是控制湍流-火焰相互作用，以平衡这些积极和消极的影响。为了应对这些挑战并克服燃气轮机中氢燃烧的现有障碍，必须开发全新的燃烧室设计。然而，到目前为止，由于传统切割和铸造技术的制造限制，燃烧器的设计参数受到很大的限制。在这种情况下，在开发过程中加入增材制造（AM）技术可能会改变游戏规则。这些技术大大拓宽了设计参数空间，为完全脱离传统限制的制造设计铺平了道路。然而，使用传统的实验和数值方法，不可能开发出一种燃烧器设计，可以考虑AM的巨大自由度。ENERGIZE的主要目标是在氢燃烧的物理和技术限制下，通过采用基于逆模型的技术优化燃烧室设计，从根本上改善燃烧室设计过程。这种逆技术是基于控制平均场方程的伴随形式，并允许优化过程的显着加速。在ENERGIZE项目中，该技术被开发用于优化湍流氢射流火焰，目的是通过定制的流量控制应用减少火焰闪回和氮氧化物排放。这些包括多孔介质，表面粗糙度/光滑度和通过微通道的吸入/吹气。该方法是跨学科的，结合了基于模型的优化和流动控制、尖端的增材制造和实验燃烧诊断。这种结合的方法有望揭示氢燃烧的基本见解，并将为开发新的氢燃烧技术提供一个综合框架。

Green hydrogen combustion will play a key role in transition towards renewable energies. However, the combustion of hydrogen presents the gas turbine community with new significant challenges. Firstly, flame stabilization in the combustion chamber is incremental to safe operation of gas turbines, but state-of-the-art solutions used in natural gas combustors are not transferable to fuels with high hydrogen content. Secondly, the interaction of turbulent flow structures with hydrogen flame fronts is not well understood, due to the lack of experimental data and detailed numerical simulations. These turbulence-flame interactions are, however, of high relevance for practical configurations. On the one hand, it causes a corrugation of the flame sheet to allow for high global consumption rates. On the other hand, it leads to hot spot-induced NOx emissions, thermoacoustic instabilities and flame noise. A main challenge is therefore to control turbulence-flame interactions to balance these both positive and negative effects. To address these challenges and to overcome the existing barriers to hydrogen combustion in gas turbines, entirely new combustor designs must be developed. Until now, however, the design parameters of combustor have been significantly limited by the manufacturing restrictions of conventional cutting and casting techniques. In this context, the inclusion of additive manufacturing (AM) technologies in the development process can be a game changer. These technologies significantly widen the design parameter space, paving the way to manufacture designs completely detached from conventional constraints. However, using conventional experimental and numerical methods, it is impossible to develop a burner design that accounts for the immense degrees of freedom of AM. The key goal of ENERGIZE is to fundamentally improve combustor design processes by employing inverse model-based techniques for combustor design optimization under the physical and technical constraints imposed by hydrogen combustion. This inverse technique is based on the adjoint form of the governing mean field equations and allows for dramatic speed-up of the optimization process. In the ENERGIZE project this technique is developed to optimize a turbulent hydrogen jet flame with the objective to reduce flame flashback and NOx emissions via tailored flow control applications. These include porous media, surface roughness/smoothness and suction/blowing via microchannels. The approach is interdisciplinary combining model-based optimization and flow control, cutting-edge additive manufacturing, and experimental combustion diagnostics. This combined approach is expected to reveal fundamental insight into hydrogen combustion and will deliver an integrated framework for the development of new hydrogen combustion technology.