A Thesis Presen ted in Fulfilm ent of the Requirem ents for the Degree of Doctor of Philosophy in Engineering August 1963 / The objectives of combustion research are considered and attention directed to laminar flames, the burning velocity of which is recognised as a basic parameter in all combustion problem s. Various methods of determining this property are critically reviewed and, as a result, it is concluded th at the spherical constant volume vessel technique is potentially one of the most versa tile and accurate. However this method does not appear to have been extensively used, probably because the available equations virtually relegate it to the status of a constant pressure technique

The "zonal grid method" is widely used to alleviate the difficulties for flow field calculations with complex geometry. In the present study, a patched grid method is employed in the computation of flow fields behind a two-ring flameholder which forms a multiple-connected region. A standard K - ε model is used to close the system. The calculation is performed by using a SIMPLE type algorithm in two subdomains in a body-fitted coordinate system With nonstaggered grid arrangements. The concept of conservative interpolation technique is applied to treat the flux conservation across the interface. The effect of the distance between these two rings on the flow pattern is studied. It is found the distance of the rings either in the axial direction or in the radial direction does not change the strength of the recirculation zone, but alters the flow pattern. The predicted streamlines, the turbulence kinetic energy K, and the reverse mass flow rate are presented. / Master of Science

A numerical model is developed to simulate the wrinkled laminar flame sheet flapping in weakly turbulent premixed combustion. The wrinkled laminar flame sheet is represented by a discrete distribution of volume sources called source disks. These source disks are utilized to produce the acceleration of combustion products behind the flame sheet. The laminar flame speed is allowed to vary according to flame stretch. A modified source model is proposed against the background of the existing source model's physically unrealistic symmetric expansion in both the upstream and the downstream directions. This flame model also includes flame-generated vorticity which is associated with the increasing entropy intrinsic to any system going through an irreversible process. The flame-generated vorticity is treated as discrete vortex disks. Vorticity created on the surface of the flame holder is computed with the vortex sheet method and diffuses into the surrounding flow in the form of vortex disks. The freestream turbulence is simulated by injecting vortex disks into an initially uniform freestream. Flame-flow interactions are studied when a thin circular cylinder, a large circular cylinder, and a flat plate normal to freestream are used as flame holders. Results sho\v that the modified source model gives more accurate prediction of flame angle than the existing source model does, the relative errors can be reduced by as much as four times. The modified source model also produces velocity profiles closer to those found in experiment, the deviations are cut by half at most sampling points in the flow. The vorticity shed from a thin circular cylinder flame stabilizer is found to only influence downstream regions very close to the cylinder. The eddy shedding behind a bluff body flame holder is suppressed in reacting flow simulations and the computed recirculating zone in a reacting flow is nearly half as long as that in a cold flow. When the relative size of the flame holder is one order of magnitude larger than the thickness of flame sheet, the vorticity shed by the flame holder can no longer be neglected. Flame wrinkling and flame extinction caused by vortical fluid motion behind the flame holder are found through numerical simulation. / Ph. D.

An experimental investigation of an opposed flow hydrogen-air diffusion flame was conducted. The purpose was to experimentally determine the flow field velocity and corresponding strain rate under different operating flow conditions. An axisymmetric opposed jet burner was employed in this experiment where air was supplied to one circular tube, while fuel and diluent were supplied to the opposing circular tube. Velocity measurements were made under two different operating flow rates, via the laser Doppler anemometer. The experimental results are used to assess current counterflow diffusion flame modeling approximations. The data shows that the radial velocity is approximately linear with radial coordinate, as assumed by most modelings. The boundary conditions (uniform axial velocity, and linear radial velocity) assumed by the potential flow model are appropriate at a particular location upstream of the boundary layer region; and the supply air strain rate approximates the potential flow strain rate, going into the flame boundary layer region. Qualitatively, the plug flow model is a better approximation to the velocity distribution for both flow cases. / Master of Science