Morones Ruelas, Anibal (2015-08). Turbulence Measurements in a Fan-Stirred Flame Bomb Using Laser Doppler Velocimetry. Master's Thesis.
An ongoing project for the construction of a high-pressure, high-temperature turbulent flame speed vessel is furthered in this study. Prior to this work, a laminar flame bomb apparatus was repurposed as a turbulent flame speed vessel with the addition of four fans. Several impeller prototypes were proposed and tested in a mock model. The turbulence was characterized with PIV. At that time, homogenous and isotropic flow field and negligible mean flow were found at the plane of measurement, but the study was limited to a small area and one fan speed. The turbulence characterization is revisited here with a newly acquired LDV system. The study objectives are to: confirm the PIV measurements with LDV, this time in the actual vessel; expand the interrogation area from a plane to a 3d volume; asses the performance of the impellers at different levels rotational speed, and; provide a more direct assessment of the temporal scale. Basic concepts on the statistical description of turbulence were introduced. The LDV principle of operation and the function of the elements comprising the LDV system were explained. The method developed for the experimentation was presented along with all the relevant parameters and adjustments in the control of the experiment. Two levels of fan speed were chosen to run in the modified turbulent vessel, namely 8,000 and 12,000 rpm. A tridimensional space situated at the center of the vessel was systematically scanned and turbulence statistics were obtained. The results confirmed some of the observations of the PIV, but the extension of the measurements to a tridimensional region also revealed unfavorable characteristics previously missed. The work concludes suggesting improvements for a new design of turbulent flame bomb. In particular a new arrangement of the fans is advised.