Pamela Logan

Acoustics of a low-speed dump combustor☆

Abstract The acoustic behavior of a dump combustor operating at very low Mach numbers is explored experimentally and analytically. Two dominant acoustic modes are identified that strongly influence the combustion process in the device: (1) a low-frequency “chugging” mode that is associated with relatively low equivalence ratios (

Incineration of Surrogate Wastes in a Low Speed Dump Combustor

Abstract An experimental study of waste surrogate (sulfur hexafluoride) destruction in a low speed dump combustor is described. The lengths of the combuslor cavity and plenum can be adjusted as a means of exciting combustion instabilities which can produce certain types of acoustic modes. In cases where the surrogate is injected either into recirculation zones within the combustor cavity or into the plenum, very high destruction and removal efficiencies (> 99.999%) can be obtained, particularly at relatively high heat release rates. Combustion instabilities are observed to play a role in the degree to which waste is destroyed, and are correlated with various acoustic modes. Under certain conditions, particularly where waste is injected into the plenum along with auxiliary fuel and oxidizer, acoustic behavior may provide a useful real-time indicator of proper incineration conditions.

Laser diagnostic techniques in a resonant incinerator

Optical diagnostics play a key role in the development of a unique, high volumetric heat release rate incinerator design at UCLA. In the device, a derivative of an aerospace dump combustor, a pre-mixed flame is stabilized within a rectangular duct by a sudden expansion in cross section at the dump plane. Wastes injected into hot, oxidative recirculation regions downstream of the dump plane experience much larger residence times than those of the bulk flow. Particle Image Velocimetry is used to study the velocity field in the combustion cavity. The results confirm the existence of the recirculation regions and illustrate the effect of waste injection on them. Planar Laser-Induced Fluorescence of the OH radical illustrates the propagation of a vortical reaction zone (flame) into the combustion cavity and its interaction with the recirculation zones.

Hot-wire accuracy in supersonic turbulence from comparisons with laser-induced fluorescence

A hot-wire anemometer and a new, nonintrusive, laser-induced fluorescence (LIF) technique are used to survey a turbulent boundary layer in a supersonic channel flow at Mach no. 2.06. The purpose is to test the accuracy of using the hot wire to measure the fluctuation amplitudes of static temperature and density in a compressible turbulent flow by comparing the results with independent and direct LIF measurements. Several methods of hot-wire calibration and analysis are applied. With each method, the hot-wire response can be related primarily to fluctuations of mass flux and total temperature, from which fluctuations of static temperature and density are calculated. However, these calculations are shown to be valid only if the fluctuations in static pressure are negligible. The acquisition and the analysis of the hot-wire data are often simplified further by neglecting the effects of fluctuations in total temperature. Comparisons of the fluctuation amplitudes of temperature and density obtained by hot-wire and LIF measurements demonstrate that such assumptions might not always be warranted, even in apparently simple flows. 21 references.

Improved method of analyzing hot-wire measurements in supersonic turbulence

The present analysis method for hot-wire data in supersonic turbulence takes sound field effects into account and yields greater accuracy in its treatment of flow variable fluctuations than existing methods despite requiring only a moderately accurate estimate of static pressure fluctuations. The method demonstrates the way in which neglecting pressure fluctuations will affect hot-wire data analysis, as well as indicating the probable direction the errors will take.