【作者】 王岩；

【导师】 周昊；

【作者基本信息】 浙江大学 ， 热能工程， 2015， 硕士

【摘要】 本文首先对燃烧热声不稳定与涡脱落问题以及声场下的喷雾特性问题的国内外研究现状进行了综述,之后对本文实验中涉及到的试验原理和试验方法,以及动态压力采集模块与PDA测量系统做了详细的介绍。本文通过搭建一维方直管实验台,利用钝体绕流生成卡门涡街,采用动态压力采集系统及FFT方法,首先研究了冷态条件下涡街频率及脱落位置对其激发直管内一维声场的特性的影响。结果显示,涡街激发的声场是多频率不同强度声波叠加的结果；激发出的声波频率及幅值与涡街频率及涡脱落位置有关,且只有部分涡街频率下的激发声波表现纯粹驻波特性。之后对台架进行相应改造,利用外加声场模拟发生燃烧热声不稳定时的脉动压力场,利用PDA系统研究了声学脉动、卡门涡街以及二者协同作用对喷雾特性的影响。结果显示,声场会提高喷雾液滴的速度并降低其平均粒径；涡街会显著影响喷雾形态、喷雾液滴速度及其分布特征,对喷雾液滴的平均粒径的影响情况比较复杂；声场强化后的涡街进一步影响喷雾速度,但对喷雾液滴平均粒径的影响基本一致。本文的研究结果可为进一步研究涡脱落激发燃烧热声不稳定提供实验基础与参考依据,可为进一步探究实际运行燃烧器发生热声不稳定时的雾化燃烧特性及利用喷雾控制燃烧不稳定作好基础铺垫。更多还原

【Abstract】 Research on impacts of vortex shedding on the thermoacoustic oscillation and spray characteristics in the presence of acoustic field were firstly reviewed. Then test principles and methods involved in this paper were introduced in detail, so were the dynamic pressure measurement system and PDA system.An experimental setup including a long straight square tube was firstly built to investigate the effect of different vortex frequencies and shedding positions on the features of one-dimensional acoustic field excited by vortex shedding which is Karman vortex street generated by flow around a bluff body here in cold condition using the dynamic pressure measurement system and FFT method. Results show that acoustic field excited by vortex shedding consists of acoustic waves with various frequencies and amplitudes. Excited frequency and amplitude of acoustic wave is related to vortex frequency and shedding position. Moreover, excited acoustic wave showed the feature of pure standing wave only under certain vortex frequency.Then the experimental setup was transformed to investigate independent and combined impacts of Karman vortex street and acoustic oscillation on the spray characteristics using the PDA system. The excited acoustic field here is to simulate the fluctuating pressure field of thermoacoustic oscillation. Results show that acoustic oscillation can increase spray droplet velocity and reduce droplet size. Vortex can significantly affect spray development, spray droplet velocity and its distribution; however its effect on spray droplet size is more complicated.Vortex enhanced by acoustic oscillation further affect spray droplet velocity, but its effect on spray droplet size basically remains the same as before.These experimental conclusions provide basics and references for further study of the excitation process of vortex shedding on thermoacoustic instability, and lay foundation for further investigations about characteristics of spray and its combustion in the presence of thermoacoustic instability in industrial burners, which will help to make use of spray to control thermoacoustic instability.更多还原