【摘要】 为研究炉内的非对称流动现象,从燃烧器对冲布置的锅炉炉膛中抽象出几何结构和物理边界条件完全对称的二维模型进行冷态流场的数值模拟,比较不同燃烧器出口雷诺数(Re)下流场对称性的变化情况,并利用相图和频谱分析等方法对特征解进行非线性特性分析。结果表明:即使几何结构及物理边界条件均对称,炉内仍会出现非对称流动;随着燃烧器出口Re的进一步增大,流场不对称性逐渐增大,流体速度随时间振荡,甚至出现混沌流;数值解存在稳定定常解、周期振荡解、非周期振荡解3种不同性质的特征解;稳定定常解的相图为不动点,频谱未出现其他基频,周期振荡解的相图为折叠的极限环,频谱出现了1个基频,非周期振荡解的相图无规则但局限于一定区域,频谱图表现为连续频谱。更多还原

【Abstract】 To study the asymmetric flow in a furnace, the cold flow field was simulated by a two-dimensional model with symmetric geometric structure and physical boundary conditions, which was abstracted from an opposed wall-fired boiler. The symmetry of flow field was compared under various Reynolds numbers, and the nonlinear characteristic of special solution was analyzed by using phase diagram and frequency spectrum. Results show that even if the geometric structure and physical boundary conditions are symmetric, asymmetric flow still exists. With the increase of Reynolds numbers, the asymmetry of flow field increases gradually, fluid velocity oscillates over time, and even appears chaotic flow. There are three kinds of special solutions with different properties: steady solution, periodic oscillatory solution and aperiodic oscillatory solution. The phase diagram of steady solution is a fixed point, and no other fundamental frequency appears in the spectrum; the phase diagram of periodic oscillation solution is a folded limit cycle, and a fundamental frequency appears in the spectrum; the phase diagram of aperiodic oscillatory solution is irregular but limited to a certain region, and the spectrum diagram transforms from discrete to continuous.更多还原