Modern methods for predicting combustion dynamics in high-pressure combustors range from high-fidelity simulations of sub-scale model combustors, mostly for validation purposes or detailed investigations of physics, to linearized, acoustics-based analysis of full-scale practical combustors. Whereas the high-fidelity simulations presumably capture the detailed physics of mixing and heat addition, computational requirements preclude their application for practical design analysis. The linear models that are used during design typically use flame transfer functions that relate the unsteady heat addition $q\prime$ to oscillations in velocity and pressure ($u\prime$ and $p\prime$) that are obtained from the wave equation. These flame transfer functions can be empirically determined from measurements or derived from theory and analysis. This paper describes a hybrid approach that uses high-fidelity simulations to generate flame transfer functions along with nonlinear Euler CFD to predict the combustor flowfield. A model rocket combustor that presented a self-excited combustion instability with pressure oscillations on the order of 10% of mean pressure is used for demonstration. Spatially distributed flame transfer functions are extracted from a high-fidelity simulation of the combustor and then used in a nonlinear Euler CFD model of the combustor to verify the approach. It is shown that the reduced-fidelity model can reproduce the unsteady behavior of the single element combustor that was both measured in the experiment and predicted by a high-fidelity simulation reasonably well.

预测高压燃烧器燃烧动力学的现代方法，从用于规模验证或对物理进行详细研究的子尺度模型燃烧器的高保真模拟，到基于线性声学的全尺寸实际燃烧器的分析，不一而足。尽管高保真度模拟可能捕获了混合和添加热量的详细物理过程，但计算要求却排除了它们在实际设计分析中的应用。在设计过程中使用的线性模型通常使用与不稳定热量增加相关的火焰传递函数$q\prime$ 速度和压力的振荡（$ü\prime$ 和 $p\prime$）是从波动方程获得的。这些火焰传递函数可以根据经验通过测量确定，也可以从理论和分析中得出。本文介绍了一种混合方法，该方法使用高保真模拟来生成火焰传递函数，并使用非线性Euler CFD来预测燃烧器流场。用于演示的模型火箭燃烧室具有自激燃烧不稳定性，且压力振荡约为平均压力的10％。从燃烧器的高保真度模拟中提取空间分布的火焰传递函数，然后将其用于燃烧器的非线性Euler CFD模型以验证该方法。