Passive Control of Combustion Instability in Lean Premixed Combustors

Abstract

A Solar fuel injector that provides lean premixed combustion conditions has been studied in a combined experimental and numerical investigation. Lean premixed conditions can be accompanied by excessive combustion driven pressure oscillations which must be eliminated before the release of a final combustor design. In order to eliminate the pressure oscillations the location of fuel injection was parametrically evaluated to determine a stable configuration. It was observed that small axial changes in the position of the fuel spokes within the premix duct of the fuel injector had a significant positive effect on decoupling the excitation of the natural acoustic modes of the combustion system. In order to further understand the phenomenon, a time-accurate 2D CFD analysis was performed. 2D analysis was first calibrated using 3D steady-state CFD computations of the premixer in order to model the radial distribution of velocities in the pre mixer caused by non-uniform inlet conditions and swirling flow. 2D time-accurate calculations were then performed on the baseline configuration. The calculations captured the coupling of heat release with the combustor acoustics, which resulted in excessive pressure oscillations. When the axial location of the fuel injection was moved, the CFD analysis accurately captured the fuel time lag to the flame-front, and qualitatively matched the experimental findings.

An investigation of instability in a domestic gas boiler by simulation

“…A survey of the numerous combustion instability models available in the literature was conducted [3][4][5][6][7][8][9][10][11][12][13][14]. In addition to the modelling of the combustion, the prediction of instability domains must take into account the dynamics of the internal flows.…”

Passive control of thermoacoustic instabilities in swirl-stabilized combustion at elevated pressures

“…A range of test conditions with air inlet temperature of 20 C were examined and details are reported in Smith, 30 including pressure, P ¼ 0.203 MPa (2 atm), 0.304 MPa (3 atm), and 0.405 MPa (4 atm); equivalence ratio, f ¼ 0.55, 0.65, and 0.75, and combustion air flow rate, Q ¼ 400 L/min and Q ¼ 600 L/min. Figure 5 shows the visual flame images, without and with PIM, for Q ¼ 400 L/min, P ¼ 0.101 MPa, and f ¼ 0.65.…”

“…16 On the other hand, passive combustion control systems are reliable but effective only for a limited operating range. Passive control techniques include baffles aimed at suppressing the acoustic standing wave; dynamic phase converters and quarter-wave tubes that alter the interactions between combustion and acoustics, 17,[19][20][21] Helmholtz resonators that dampen and dissipate the acoustic energy [22][23][24][25] and perforated liners. 26,27 Recently, a passive technique to suppress combustion instabilities and noise in swirl-stabilized, LPM systems has been introduced by our research group.…”

Mitigating self-excited flame pulsating and thermoacoustic oscillations using perforated liners

“…Passive control methods [31] are more reliable and robust and effective, when designed properly. Some solutions have already been proved to be applicable in real configurations [32,33].…”