基于描述函数的燃烧振荡建模与仿真

Modeling and Simulation of Combustion Oscillations Based on Describing Function Method

关键词:  燃气轮机  燃烧振荡  非线性  描述函数  热声耦合

Key words:  Gas turbine  Combustion oscillations  Nonlinearity  Describing function  Thermoacoustic coupling

摘要:

针对贫预混燃烧在燃气轮机燃烧室中的燃烧振荡问题进行主动控制技术研究，一般需依赖于较为准确的火焰动力学模型，但是，通过仿真或者试验测量完整、准确的非线性火焰动力学响应特性都存在较大的困难。针对该问题，基于声学分析，结合非线性建模方法的应用，提出了一种基于描述函数的热声耦合系统分析方法，既能够体现火焰非线性动力学过程的影响，又便于实验测量与系统辨识。本文对旋流预混燃烧室的热声耦合特性进行了实验测量，通过系统辨识得到热声耦合系统的描述函数模型，在此基础上开展热声耦合系统时域仿真分析。实验测量结果表明，包含火焰动力学过程的声波传播过程具有较强的非线性特征，并且在一定频率范围内描述函数的幅值随扰动量幅值变化显著；仿真分析结果证明了辨识得到的描述函数可以对燃烧室中的热声耦合形成过程和极限环振荡特征进行描述。

Abstract:

To study the active control technique of combustion oscillations in a lean premixed gas turbine combustor， a detailed flame dynamic model is generally needed. However， there are greater difficulties to acquire the complete and accurate nonlinear flame dynamic response by simulation or experiment. In response to this problem， this paper proposes a thermos-acoustic system analysis method based on the Describe Function method， which can not only describe the influence of the flame’s nonlinear dynamics process， but also facilitate experimental measurement and system identification. The analysis is based on acoustic analysis and combined with the application of nonlinear modeling methods. The thermoacoustic instability characteristics of the swirling premixed combustor were measured experimentally. The describe function models of the thermoacoustic coupling system were obtained by system identification， and they were used in the time domain simulation of the thermoacoustic system. The experimental results show that the sound wave propagation process including the flame dynamics process has strong nonlinear characteristics. Within a certain frequency range， the variation of the describe function amplitude with the input disturbance amplitude shows a significant tendency. The simulation results prove that the identified describe functions can describe the thermoacoustic instability growing process and the limit cycle in the combustor.