Understanding the Role of Heat Recirculation in Enhancing the Speed of Premixed Laminar Flames in a Parallel Plate Micro-Combustor
Abstract
This dissertation investigates the role of heat recirculation in enhancing the flame speeds of laminar flames stabilized in a parallel plate reactor by: (1) developing analytical models that account for conjugate heat transfer with the wall and (2) making measurements of temperature profiles in a simulated microcombustor using nonintrusive FTIR spectroscopy from which heat recirculation is inferred. The analytical models have varying degrees of complexity. A simple heat transfer model simulates the flame by incorporating a concentrated heat release function along with constant temperature wall model. The next level model accommodates conjugate heat transfer with the wall along with a built in heat loss model to the environment. The heat transfer models identify the thermal design parameters influencing the temperature profiles and the Nusselt number. The conjugate heat transfer model is coupled with a species transport equation to develop a 2-D model that predicts the flame speed as an eigenvalue of the problem. The flame speed model shows that there are three design parameters (wall thermal conductivity ratio (kappa), wall thickness ratio (tau) and external heat loss parameter (NuE) that influence the flame speed. Finally, it is shown that all these three parameters really control the total heat recirculation which is a single valued function of the flame speed and independent of the velocity profile (Plug or Poiseuille flow). On the experimental side, a previously developed non-intrusive diagnostic technique based on FTIR spectroscopy of CO2 absorbance is improved by identifying the various limitations (interferences from other species, temperature profile fitting, etc) and suggesting improvements to each limitation to make measurements in a silicon walled, simulated microcombustor. Methane/Air and Propane/Air flames were studied for different equivalence ratios and burning velocities.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2009
- Accession Number
- ADA605170
Entities
People
- Ananthanarayanan Veeraragavan
Organizations
- University of Maryland