贫燃预混燃烧热声不稳定特性及其物理机制的研究对于发展低排放、高可靠性的工业燃烧器具有重要意义。本文建立了一套单喷嘴预混旋流燃烧实验装置，围绕热声不稳定特性及其影响因素的作用规律开展实验研究，并结合理论模型分析揭示燃烧过程中的热声不稳定性物理机理。首先，论文研究了热声不稳定发生时燃烧室的压力、释热率振荡特性，以及速度脉动驱动的火焰面演化规律。热声振荡发生时，燃烧器流道内形成了类似于驻波的大幅度压力振荡，分析表明其振型和频率与轴向一阶声学模态近似；释热率与压力同频脉动，两者强烈耦合。研究发现，进气速度的振荡导致火焰锋面往复收扩和火焰褶皱变化，由此引发的火焰表面积时空变化是驱动释热率脉动的主要机制。当旋流火焰与燃烧室壁面作用会使火焰面发生破碎，加速火焰表面积达到最大，从而解释了实验测试中释热率信号产生的“尖峰”。其次，研究了化学当量比、进气参数（进气速度、旋流数）和结构参数（燃烧室和进气段长度）对预混旋流燃烧热声不稳定的影响规律。结果表明，当量比和结构参数对热声不稳定性影响显著，前者主要改变预混气燃烧特性，后者改变燃烧器的声学特性。随着当量比从贫燃到富燃变化，燃烧器经历了“稳定燃烧—准周期性振荡—极限环振荡—准周期性振荡—稳定燃烧”的转变，燃烧室足够短和进气段足够长，均不会发生热声振荡。进气速度与旋流数主要改变燃烧的总放热功率、火焰形态以及火焰与燃烧室壁面的作用，其对热声不稳定的影响相对较弱。再者，研究了声学激励下预混旋流燃烧室的非线性动态特性以及火焰响应特性。结果表明，当声学激励频率在燃烧室声学固有频率附近时会产生共振，导致喷口处速度脉动振幅受限；激励振幅较大且频率在声学固有频率的分谐频附近时，由于声学模态振荡与释热率脉动之间耦合会诱发超谐频共振。火焰对于声学扰动的响应表现出低通频率特性和增益饱和特性，受当量比和进气参数的影响较大。最后，针对本文研究的甲烷-空气预混旋流燃烧器，通过热声学网络模型对热声不稳定性进行了预报分析。结果表明，基于全局和分布式火焰响应函数的模型分析结果基本相同，压力振型与实验结果相符，计算的模态频率与实际值存在一定偏差，当火焰锚定时，计算值低于实际主频，当火焰抬举时，计算值高于实际主频。模型计算的模态振幅增长率能在一定程度上反映热声不稳定压力振荡幅值的大小。

The research on thermoacoustic instabilities in the lean premixed swirl combustion process and its physical mechanism is of great significance for the development of low-emission and high-reliability combustors. In this thesis, a single-nozzle premixed swirl-stabilized combustion system is established for the methane and air mixture. The experimental research is carried out around the thermoacoustic instability characteristics and its influencing factors and the physical mechanism is further disclosed with the theoretical analysis. Firstly, the thesis studies the pressure and heat release rate oscillation characteristics in the combustion chamber, and the evolution of the flame surface driven by velocity perturbation. When the thermoacoustic oscillation occurs, a large-amplitude pressure oscillation similar to a standing wave is formed in the internal channel of the combustor. Analysis shows that its vibration pattern and frequency are similar to the axial first-order acoustic mode; both the heat release rate and the pressure fluctuate at the same frequency. It is found that the inlet velocity perturbation leads to the reciprocating retraction and expansion of the flame front as well as the further change of the flame wrinkle. The spatio-temporal varying in the flame surface area are the key mechanism for driving the fluctuation of the heat release rate. When the swirling flame interacts with the combustor wall, the flame surface will be broken out, and the flame surface area will be extended to the maximum. This can explain that a “spike” exists in measuring signal of heat release rate.Secondly, the influence of chemical equivalence ratio, inlet conditions (mainly the inlet velocity and swirl number) and structural parameters (combustion chamber length and inlet section length) on the thermoacoustic instability of premixed swirl-stabilized combustor is studied. The results reveal that the equivalence ratio and structural parameters have significant effects on thermoacoustic instabilities. The former one mainly changes the sensitivity of the flame to disturbances, while the latter one changes the acoustic characteristics of the burner. As the equivalence ratio changes from the lean to the rich, the burner undergones a transition process: from the stable combustion, quasi-periodic oscillation, limit cycle oscillation, quasi-periodical oscillation, until the stable combustion. If the combustion chamber is short enough or the inlet section is long enough, there will be no thermoacoustic oscillations. The inlet velocity and the swirl number mainly change the flame heat release power, flame shape and the interaction between the flame and the combustor wall, and their influence on the thermoacoustic instability is relatively weaker.Furthermore, the nonlinear dynamic characteristics of the premixed swirl-stabilized combustor and flame response characteristics under acoustic excitation are studied. The results show that resonance will occur when the acoustic excitation frequency near the acoustic natural frequency of the combustion chamber, the velocity perturbation amplitude at the nozzle will be suppressed. When the excitation amplitude is large enough and the frequency is near the subharmonic frequency of the acoustic natural frequency, the coupling between the acoustic natural mode oscillation and the heat release rate fluctuation can induce a superharmonic resonance. The flame response to the acoustic disturbance exhibits low-pass frequency characteristics and gain its saturation, which is greatly affected by the equivalence ratio and inlet conditions.Finally, for the methane-air premixed swirl-stabilized combustor studied in this thesis, the thermoacoustic instability is predicted and analyzed through the thermoacoustic network model. The results show that the prediction results based on the global and distributed flame response functions are basically the same. The mode of vibration is consistent with the experimental results, while the calculated mode frequency has a certain deviation from the actual value. If the actual flame is anchorated, the calculated value is lower than the actual frequency; if the actual flame lift-off, it is higher. The magnitude of growth rate calculated by the model is partly able to represent the actual pressure oscillation amplitude.