An experimental study into the manipulation and control of combustion instability in swirl-stabilized flames via active control of heat-loss from the wave-maker region.

• Applicant: Abhishek Kushwaha
• Subject Area: Hydraulic and Turbo Engines and Piston Engines ; Fluid Mechanics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 541611060

The primary objective of this project is to experimentally investigate the hypothesis that the stability of combustion in swirl-stabilized burners with a wavemaker region depends on the spatial overlapping of the flame with the wavemaker region. The study employs the "PRECCINSTA" model combustor, subjecting it to known flow conditions that yield a stable flame overlapping the wavemaker region. Active cooling of the burner centerbody will be used to induce localized flame extinction within the wavemaker region while preserving the underlying fluid dynamics. By disrupting the spatial overlap of the flame with the wavemaker region, I will experimentally test the hypothesis that the flame stability in swirl-stabilized burners characterized by a wavemaker region, necessitates the spatial overlap between the flame and the wavemaker region. The research contributes to our understanding in the following ways: 1. Revealing the effects of the perturbations in the wavemaker region: By forcing the flame out of the wavemaker region, alterations in the flow field will manifest, leading to modifications in flow characteristics. Alongside changes in flow characteristics, the properties of the flame will undergo modifications due to reduced central body temperature. A comprehensive examination of these variations in the flow and the flame and their consequences is essential. 2. Mitigation of Combustion Instability: By addressing the above concerns, we can identify effective mechanisms to mitigate combustion instability. This can be achieved by manipulating the central body temperature. A detailed analysis of experimental data of the combustor uncovers four distinct combustor states: (i) chaotic oscillations during stable operation, (ii) intermittency, (iii) Period-1 limit cycle oscillations (P1-LCO), and (iv) Period-2 limit cycle oscillations (P2-LCO). It is imperative to ascertain whether altering the centerbody temperature induces thermoacoustic instability and, if so, classify it as P1-LCO or P2-LCO. Investigating the underlying mechanisms driving these variations represents a significant research endeavour. Simultaneously, gaining insights into the complex dynamics of the combustor necessitates a comprehensive understanding of the flow field and its associated mechanisms, particularly vortices and shear layers. Manipulating the central body temperature induces changes in the size and shape of vortices and shear layers in the flow field, thus enhancing our understanding of the physical mechanisms governing variations in the flow and the flame fields.

• DFG Programme: WBP Position