Acoustics
Blazetech has extensive experience with acoustic-combustion instabilities to minimize noise from burners and flow systems. We have also used sound to enhance combustion. Sample related activities at
BlazeTech include:
Air Force
For the Air Force, we investigated the influence of bubbles on the propagation of sound and shock waves in a liquid medium. Tests were conducted in a two inch diameter tube by one meter
long. The speed of sound was measured for various bubble sizes and number densities (void fraction). Up to 98% pressure attenuation was obtained compared to a non-bubbly liquid. The low amplitude results were
qualitatively supported by numerical calculations using a state-of-the-art finite amplitude, non-linear pressure wave propagation model.
DOE
For DOE, we developed an advanced concept in Fluidized Bed Combustion involving air pulsation to improve performance. Two regimes were considered: a high frequency regime where a high power
siren is used to impose an acoustic field on the bed; and a low-frequency regime where the air flow was modulated with a mechanically driven valve. We characterized the performance improvement in each regime
and carried out successful validation tests on small- scale cold-flow model. A plan was developed for testing a large scale fluid bed combustor at a DOE facility.
Also, we developed an analysis of the effects of sonic fields on heat and mass transport across boundary layers. The analysis identified the
conditions (frequency and dB level) required for sound-induced transport augmentation over the steady flow case.
NASA
For NASA, we developed a non-intrusive, acoustic based technique to determine the liquid volume content of a tank where the liquid/vapor interface is not well defined. We added a small
turret to the tank and imposed airflow over it (as in a musical instrument) to excite the tank as a Helmholtz resonator. The resonance frequency was measured and translated into a liquid volume. We
established the proof of concept by testing. This method is particularly useful in tank with complex volumes and uneven liquid level as would occur in a commercial aircraft.
Oil Industry
For an oil company, we modeled the fast deflagration of unconfined propane
vapor clouds of various shapes. We used linear acoustic theory and a Taylor-type constant-velocity flame-piston formulation to estimate bounds on the predicted overpressures. We showed that the results for pancake-shaped clouds differ significantly from the use of standard TNT-equivalent analyses.
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