基于调谐被动控制方法的脉动燃烧驱动机理研究

Pulse combustion as a special combustion process is widely recognized to its high combustion efficiency and intensity, high heat transfer rates and low pollutant emission. How to optimize pulse combustion characteristics by effectively increasing the thermoacoustic coupling as well as decreasing the acoustic dissipation has become a research focus. In recent researches, passive control and active control as the two main kinds of control methods have obvious shortcomings. The former tends to be effective over only a limited range of operating conditions for specific devices and the latter which intervenes combustion dynamically by control algorithm has the potential to generate the opposite effects. The conclusions from these methods are disputable and there is no developed unify understanding on the driven mechanism of pulse combustion, which leads to the significant limitation for developing pulse combustors. Therefore, how to aim at the phenomena that coupled with combustion heat release, acoustic oscillation and boundary conditions for proposing a research approach that can control and adjust them separately during the pulse combustion process is significantly important. Investigation of pulse combustion driven mechanism based on tuned passive control methods is presented. From the interactive coupling point of view, the effects of boundary conditions on acoustic oscillation and the effects of fuels and air distribution on the thermoacoustic coupling tend to be investigated separately. The driven mechanism model of pulse combustion as well as measures for optimizing pulse combustion characteristics will be proposed, which will provide the theoretical reference for the control and optimal design of pulse combustors.

脉动燃烧作为一种特殊的燃烧方式，以其燃烧效率高、强度大、传热率高、污染物排放量低等特性得到了广泛认可。如何有效加强热声耦合、降低声耗散来优化脉动燃烧特性成为研究焦点。在目前的研究中，被动控制和主动控制作为两种主要的控制方法存在明显不足，前者只对特定设备有效，且调节范围有限；而后者通过控制算法对燃烧动态干预，有时却起到相反的效果。这两种方法得出的结论存在争议，尚未形成对脉动燃烧驱动机理的统一认识，这极大地制约了脉动燃烧器的发展。因此，如何针对脉动燃烧过程中燃烧放热、声脉动、边界条件相互耦合的现象，提出一种能对其分别进行控制、调节的研究方法具有重要意义。本项目提出基于调谐被动控制方法研究脉动燃烧的驱动机理，从交互耦合的视角研究边界条件对声脉动的影响，研究燃料和配风对热声耦合的影响，给出脉动燃烧驱动机理模型，提出优化脉动燃烧特性的措施，为脉动燃烧器的控制和优化设计提供理论参考。

脉动燃烧作为一种特殊的燃烧方式，以其燃烧效率高、强度大、传热率高、污染物排放量低等特性得到了广泛认可。如何有效加强热声耦合、降低声耗散来优化脉动燃烧特性成为研究焦点。由于被动控制和主动控制作为两种主要的控制方法存在明显不足，得出的结论存在争议，尚未形成对脉动燃烧驱动机理的统一认识，极大地制约了脉动燃烧器的发展。因此，如何针对脉动燃烧过程中燃烧放热、声脉动、边界条件相互耦合的现象，提出一种能对其分别进行控制、调节的研究方法具有重要意义。本项目提出基于调谐被动控制方法研究脉动燃烧的驱动机理，从交互耦合的视角研究了边界条件对声脉动的影响，以及燃料和配风对热声耦合的影响。揭示了脉动燃烧的着火机理：着火过程分为4个阶段：a.预着火过渡阶段，b.点火延迟阶段，c.脉动发展阶段，d.周期性振荡阶段。脉动燃烧形成之初的点火源是回流烟气，而稳定周期振荡阶段的点火源是接近未燃混合气处的高温残余气体。本项目得到了脉动燃烧器的NOx排放特性：燃烧温度及烟气在高温区的停留时间对NOx排放量影响较大，存在一个优化的热负荷区间，使NOx排放量较低。建立了脉动燃烧器直弯尾管传热准则方程，与实验数据的误差范围小于20%。本项目通过调节去耦室压力、增加燃料/ 空气喷注单元、改变配风比例，实现了脉动燃烧的调谐被动控制，提高了Helmholtz型无阀自激脉动燃烧器频率和压力的调节范围，并提出了优化控制措施，给出了Helmhotlz型无阀自激脉动燃烧油田加热炉设计简例，也研制了用于相关领域研究的无阀自激脉动燃烧器设备。本项目的实施，为脉动燃烧器的控制和优化设计提供了理论参考，也为开发Helmholtz型无阀自激脉动燃烧器奠定了基础。