Passive control of combustion noise and thermo-acoustic instability with porous inert media

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dc.contributor Baker, John
dc.contributor Lane, Alan M.
dc.contributor Taylor, Robert P.
dc.contributor.advisor Agrawal, Ajay K. Smith, Zachary A. 2017-03-01T14:47:25Z 2017-03-01T14:47:25Z 2011
dc.identifier.other u0015_0000001_0000713
dc.identifier.other Smith_alatus_0004M_10755
dc.description Electronic Thesis or Dissertation
dc.description.abstract Combustion noise and thermo-acoustic instability present a major area of concern for many industrial combustion applications, especially those operating under lean-premixed (LPM) conditions. While LPM combustion reduces thermal NOx by allowing operation at reduced flame temperatures, LPM flames are particularly susceptible to combustion noise and instability. While combustion noise and thermo-acoustic instability are distinctly different phenomena; both originate from the same source ‒ unsteady heat release in a turbulent flow field. Instabilities are self-excited and arise when energy from combustion is added to the system faster than energy is dissipated by heat transfer. In a typical swirl-stabilized combustor, flame is stabilized downstream of the dump plane and is sustained by central and corner recirculation zones. The present study combines porous inert media (PIM) assisted combustion with swirl-stabilized combustion to alter the combustor flow field in an advantageous manner. A ring-shaped PIM insert is placed directly at the dump plane to eliminate zones of intense turbulent fluctuations, thereby mitigating combustion noise at the source. With PIM, a central flame is confined within the annular void of the insert while a small portion of reactants flow through the PIM and stabilize on the downstream surface. Additionally, the porous insert provides acoustic damping and passive attenuation of pressure waves. This study is a preliminary step towards implementing the technique at elevated operating pressures, and eventually, liquid fuel combustors. Atmospheric combustion tests are conducted for a variety operating conditions to determine effectiveness of PIM to reduce combustion noise and instability. Parameters varied include air preheat temperature, air flow rate, equivalence ratio, and swirler axial location. Experiments are conducted with a high swirl angle, as opposed to previous experiments which used a lower swirl angle. For most conditions, PIM is shown to reduce total sound pressure level (SPL) in cases where instability is not intense. For all cases where instability is the dominant component of total SPL, PIM is extremely effective in eliminating instability. In these cases, total SPL is reduced by as much as 30 dB with PIM combustion. Furthermore, experiments show that no significant pressure drop penalty is incurred with porous media.
dc.format.extent 244 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Mechanical engineering
dc.title Passive control of combustion noise and thermo-acoustic instability with porous inert media
dc.type thesis
dc.type text University of Alabama. Dept. of Mechanical Engineering Mechanical Engineering The University of Alabama master's M.S.

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