Indirect combustion noise is caused by entropy spots that are accelerated at the first turbine stage. These so-called entropy waves originate from the equivalence ratio fluctuations in the air–fuel mixture upstream of the flame. As entropy waves propagate convectively through the combustion chamber, they are subject to diffusion and dispersion. Because of the inherent difficulty of accurately measuring the burned gas temperature with sufficient temporal resolution, experimental data of entropy waves are scarce. In this work, the transfer function between equivalence ratio fluctuations and entropy fluctuations is modeled by a linearized reactor model, and the transport of entropy waves is investigated based on a convection-diffusion model. Temperature fluctuations are measured by means of a novel measurement technique at different axial positions downstream of the premixed flame, which is forced by periodic fuel injection. Experiments with various flow velocities and excitation frequencies enable model validation over a wide range of parameters.

中文翻译：

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燃气轮机燃烧室中熵波的产生和传输的测量和建模

间接燃烧噪声是由在涡轮第一级加速的熵点引起的。这些所谓的熵波源自火焰上游的空气燃料混合物中的当量比波动。当熵波通过燃烧室对流传播时，它们会扩散和弥散。由于以足够的时间分辨率精确测量燃烧气体温度存在固有的困难，因此熵波的实验数据稀缺。在这项工作中，通过线性化反应器模型对当量比波动和熵波动之间的传递函数进行建模，并基于对流扩散模型研究熵波的传输。通过一种新颖的测量技术，在预混火焰下游的不同轴向位置测量温度波动，这是通过定期喷射燃料来实现的。使用各种流速和激励频率进行的实验可以对各种参数进行模型验证。