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Measurements of combustion dynamics with laser-based diagnostic techniques.

机译：使用基于激光的诊断技术测量燃烧动力学。

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Since the early days of gas turbine engines, combustion/flow instability inside the combustor has been an issue in many engines, but little has been understood as to how the dynamics of the system involved contribute to the instability. The primary objective of this work is to provide general experimental procedures and to validate methods for examining the dynamic behaviors of combustion systems, and to provide accurate measurements of the combustion dynamics for use as a foundation for further theoretical and numerical research. Knowledge of the fundamental dynamics of combustion systems is crucial in understanding and modeling the flame behavior and enabling the use of insights in design process and for creating robust active control of combustors.; Since mixing plays significant roles in combustion processes, the dynamics of fuel/air mixing were studied. A non-premixed burner was examined with acoustic excitations at 22∼55 Hz to assess the mixing and its relation to the thermo-acoustic coupling. Phase-resolved acetone-PLIF was used to image the mixing, and from this the unmixedness was calculated, which quantifies the degree of mixing. The results show that (1) the acoustic waves induce periodicity in the degree of mixing; (2) the way the unmixedness behaves coincides well with the behavior of the Rayleigh index, implying the degree of mixing is a major factor in determining the stability of the combustion system; (3) the two-dimensional measurements of temporal unmixedness effectively visualize the shear mixing zone. A second low-swirl premixed burner was studied to examine the impact of acoustic waves on the combustion dynamics. Measurements were performed with OH-PLIF, with acoustic forcing up to 400 Hz. Swirl burners at higher pressure are industry standard, and this study examined the dynamics at elevated combustor pressure. The results show that (1) the thermo-acoustic coupling seems to be closely coupled to the vortices generated at the flame boundary; (2) high magnitude of flame response coincides with the high absolute value of Rayleigh index; (3) the way the thermo-acoustic coupling is distributed over the space is highly dependent on the excitation frequencies; (4) high pressure suppresses the sensitivity of combustions system to outside disturbances.
机译：自从燃气涡轮发动机问世以来，燃烧器内部的燃烧/流动不稳定性一直是许多发动机中的问题，但是对于所涉及的系统的动力学如何导致不稳定性的了解很少。这项工作的主要目的是提供通用的实验程序并验证检查燃烧系统动态行为的方法，并提供燃烧动力学的准确测量值，以作为进一步的理论和数值研究的基础。燃烧系统的基本动力学知识对于理解和建模火焰行为，在设计过程中使用见解以及创建可靠的燃烧器主动控制至关重要。由于混合在燃烧过程中起着重要作用，因此研究了燃料/空气混合的动力学。对未预混合的燃烧器进行了22〜55 Hz的声激发检查，以评估混合及其与热声耦合的关系。使用相分离的丙酮-PLIF对混合进行成像，并由此计算出未混合度，从而量化了混合度。结果表明：（1）声波在混合度上具有周期性。 （2）不混合性的行为与瑞利指数的行为吻合得很好，这意味着混合程度是决定燃烧系统稳定性的主要因素； （3）时间非混合的二维测量有效地可视化了剪切混合带。研究了第二个低涡流预混燃烧器，以检查声波对燃烧动力学的影响。测量是使用OH-PLIF进行的，声强高达400 Hz。高压旋流燃烧器是工业标准，这项研究研究了燃烧器压力升高时的动态特性。结果表明：（1）热声耦合似乎与火焰边界处产生的涡旋紧密耦合； （2）较高的火焰响应值与较高的瑞利指数绝对值一致； （3）热声耦合在空间上的分布方式高度依赖于激励频率； （4）高压抑制了燃烧系统对外界干扰的敏感性。

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