Impact of Centerbodies on the Precessing Vortex Core in Swirling Flow
Open Access
- Author:
- Horigan, Jackson
- Area of Honors:
- Mechanical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Jacqueline Antonia O'Connor, Thesis Supervisor
Jean-Michel Mongeau, Thesis Honors Advisor - Keywords:
- Swirl
PVC
Centerbody
Combustion
Precessing - Abstract:
- Gas turbine combustion systems are susceptible to combustion instability, or the coupling between combustor acoustics and flame heat release rate oscillations, which can damage the combustor if oscillation amplitudes are not controlled. The dynamic structure in typical combustor flow fields is the precessing vortex core (PVC), which can interact with the thermoacoustic combustion instability oscillations. Some studies have shown that it can enhance these destructive instabilities, while others from our lab at Penn State have provided evidence that it can suppress combustion instability. Combustor designers can use different geometries and fuel injection hardware to minimize the negative contributions the PVC has on the flow. One such piece of hardware is a centerbody, a cylindrical mass that is placed ahead of the swirler in the combustor to disturb the vortex breakdown bubble and further stabilize the flame by creating a low-velocity region immediately ahead of it. Determining the impact of centerbodies on combustor flow fields, particularly the precessing vortex core, would be useful for designers, as they would gain more understanding of how the dynamic properties of the flow will change and can more accurately predict combustor performance. Prior research hypothesizes that the presence of a centerbody should suppress the PVC by disrupting the wavemaker region of the flow immediately ahead of the central recirculation zone. This work investigates the impact of different geometry centerbodies on non-reacting, variable-swirl air flow. Acoustic signals from the flow are analyzed to characterize PVC frequencies at different swirl numbers. The goal of this work is to better understand how centerbodies of different designs affect the PVC.