Numerical Study on the Route of Flame-Induced Thermoacoustic Instability in a Rijke Burner

Abstract

The self-excited thermoacoustic instability in a two-dimensional Rijke-type burner with a center-stabilized premixed methane–air flame is numerically studied. The simulation considers the reacting flow, flame dynamics, and radiation model to investigate the important physical processes. A finite volume-based approach is used to simulate reacting flows under both laminar and turbulent flow conditions. Chemical reaction modeling is conducted via the finite-rate/eddy dissipation model with one-step reaction mechanisms, and the radiation heat flux and turbulent flow characteristics are determined by using the P-1 model and the standard k-ε model, respectively. The steady-state reacting flow is first simulated for model verification. Then, the dynamic pressure, velocity, and reaction heat evolutions are determined to show the onset and growth rate of self-excited instability in the burner. Using the fast Fourier transform (FFT) method, the frequency of the limit cycle oscillation is obtained, which agrees well with the theoretical prediction. The dynamic pressure and velocity along the tube axis provide the acoustic oscillation mode and amplitude, also agreeing well with the prediction. Finally, the unsteady flow field at different times in a limit cycle shows that flame-induced vortices occur inside the combustor, and the temperature distribution indicates that the back-and-forth velocity changes in the tube vary the distance between the flame and honeycomb in turn, forming a forward feedback loop in the tube. The results reveal the route of flame-induced thermoacoustic instability in the Rijke-type burner and indicate periodical vortex formation and breakdown in the Rijke burner, which should be considered turbulent flow under thermoacoustic instability.

Self-Excited Thermoacoustic Instability Behavior of a Hedge Premixed Combustion System with an Asymmetric Air/Fuel Supply or Combustion Condition

“…where N is the number of samples and p i is the measured pressure. Alternatively, the sound pressure level (SPL, dB) was also used for a broader amplitude comparison, as given in Equation (2).…”

“…The famous Rayleigh criterion [5] proposed that the coupling between pressure oscillation and reaction heat release oscillation is the main cause of SETAI, and this coupling will encourage SETAI if the phase difference is less than 90 • . This criterion has been widely confirmed and acknowledged by various scholars [1,2,[6][7][8]. However, the oscillation phase difference is very microscopic, and it is virtually impossible to use operation parameters for SETAI prediction via the Rayleigh criterion.…”

“…Self-excited thermoacoustic instability (SETAI) is a very undesirable phenomenon for gas-and liquid-fired equipment [1][2][3]. The accompanying strong vibration causes large noise, equipment damage, failure, and even personal safety accidents [4].…”

“…Our previous work demonstrated that the premixed supply duct length (L P ), fuel flow rate (V F ), and ϕ have a coupled effect that allows for the identification of the phase difference between pressure and heat release oscillation [24,25] by introducing the flow rate oscillation at the combustion chamber inlet. This flow rate oscillation is caused by the pressure oscillation, and their phase difference [8] is determined by the sound pressure mode shape within the premixed duct [2], which is further collaboratively influenced by L P and V F . However, this flow rate oscillation could cause heat release oscillation, and there is also a phase difference between them due to the time needed for the combustion reaction.…”

Patent Analysis of the Development of Technologies Applied to the Combustion Process

“…However, it is important to mention that the search for methodologies involving processes with lower GHG emissions, for example, may be one of the factors why high percentages were not observed. This may strengthen the idea that new technologies, besides OEC, applied to the combustion process are characterized as a potential area of exploration, such as the involvement of acoustic excitation in the processes that, although the technological prospection itself has not been found in many patent applications, have shown good results in the scientific literature, indicating the possibility of their application to combustion processes, with the aim of reducing the negative effects of the process and potentializing the market with new technologies that can be patented [65][66][67][68][69][70].…”