Basic Instability Mechanisms in Chemically Reacting Subsonic and Supersonic Flows
Abstract
This report summarizes the main results and conclusions of research on turbulent combustion. The main objective was to determine and elucidate the mechanisms governing turbulence-combustion interactions in different spectral regimes. Problems studied included: 1) Structure of disturbed flames; 2) Evolution of turbulence-combustion interactions; and 3) Thermal and flow structures of turbulent premixed V-flames at low Damkoehler numbers. In an experimental investigation, simultaneous measurements of velocity and temperature in premixed, rod-stabilized, lean methane-air V-flames demonstrated the presence of high-frequency fluctuations within slowly drifting flame brushes, leading to temporal changes in flame shapes, thicknesses and propagation speeds. Cross-correlation coefficients of these simultaneous signals assumed high values within the reaction zone, suggesting the possibility that these fluctuations might be induced by the same governing mechanism. A theoretical study showed the importance of 'wrinkling-like' effects as well as the effects of chemical reactions rate on the evolution of fluctuations in a reacting shear layer. The direct rate-augmentation effects due to reaction led to changes in phase relationships between the various fluctuations, resulting in turbulent energy and mass transport in a direction opposite to that suggested by the gradient model. Keywords: Reaction kinetics; Energy transport; Thermal and flow structures; Methane/ethane/air; High frequency fluctuations; Spectral density distributions; Probability density functions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 08, 1989
- Accession Number
- ADA206669
Entities
People
- Tau-yi Toong
Organizations
- Massachusetts Institute of Technology