Basic Instability Mechanisms in Chemically Reacting Subsonic and Supersonic Flows
Abstract
Examination of low-frequency instability in ramjet dump combustors shows that the oscillations are triggered and sustained by interactions between non-uniform entropy zones and pressure waves. Pressure waves are produced as entropy waves convect through a choked nozzle and entropy waves are generated as the pressure waves perturb the combustion zone. A linearized stability theory is developed for the case of near blow-off which corresponds to maximum rumble. Both oscillation frequencies and amplification rates are obtained. The theory is used to analyze the effects of combustor configurations (including combustor-to- inlet area ratio, nozzle-to-combustor area ratio, combustor diameter, presence of flameholder and mode of fuel injection), inlet stanation temperature, and fuel-air ration on stability. Both predicted frequencies and stability characteristics agree well with the experimental observations. One possible mechanism of turbulence-combustion interactions has been examined by studying the development of Tollmien-Schlichting waves in a reacting shear layer. Analysis shows that the growth rates of these waves depend on the order, the thermocity, and the activation energy of the Arrhenius-type chemical reaction as well as the disturbance wavelengths and Damkohler's similarity parameters. (AW)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 29, 1982
- Accession Number
- ADA215282
Entities
People
- T. Y. Toong
Organizations
- Massachusetts Institute of Technology