Study on Passive Control of the Self-excited Thermoacoustic Oscillations Occurring in Combustion Systems

ABSTRACT

Self-excited thermoacoustic oscillations seriously threaten the operation of combustion equipment. Various active and passive control methods for self-excited thermoacoustic oscillations have been proposed, while most existing methods are complex and difficult to implement. A new passive control method was expected to be proposed in the present study. The thermoacoustic oscillations occurring in asymmetrical two-dimensional combustion systems were investigated numerically. The control effects of the asymmetrical fuel-air feed conditions on thermoacoustic oscillations were examined. In addition, experimental tests were performed to further examine the control effects. The results showed that the oscillations would be encouraged in an asymmetrical combustion system if an appropriate standing wave was formed. The asymmetrical fuel-air feed conditions could affect the waveform and consequently influence the occurrence of thermoacoustic oscillations. The oscillations could be eliminated by adjusting the length or the inlet boundary condition for half of the fuel-air feed channels, and the combustion chamber did not need to be retrofitted. The passive control method was simple and easy to implement for eliminating thermoacoustic oscillations.

KEYWORDS:

• Self-excited thermoacoustic oscillations
• passive control
• asymmetrical fuel-air feed condition
• standing wave analysis

Nomenclature

$t$ time

$\rho$ density

$u_i$ mean velocity in $x_i$ direction

$x_i$ Cartesian coordinates in the $i$ direction

$p$ static pressure

${\tau }_{ij}$ stress tensor

$-\rho \stackrel{‾}{{u{ }^{\mathrm{\prime }}}_i{u{ }^{\mathrm{\prime }}}_j}$ Reynolds stress

$Y_n$ mass fraction of the $n^{th}$ species

$J_n$ diffusion flux of the $n^{th}$ species

$R_n$ species source from chemical reaction

$E$ total energy

$\lambda$ thermal conductivity

${\lambda }_t$ turbulent thermal conductivity

$S_c$ energy source from chemical reaction

$S_r$ energy source from radiation

Acknowledgments

The authors acknowledge financial support from the National Natural Science Foundation of China (51906192) and the Natural Science Basic Research Plan in Shaanxi Province of China (2020JQ-061).

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [51906192]; Natural Science Basic Research Plan in Shaanxi Province of China [2020JQ-061].