As a part of NISTs program to standardize measurements of greenhouse gas emissions, we are developing a long-wavelength acoustic flowmeter (LWAF) for accurate, economical measurements of exhaust flows from coal-burning power plants. Measurements of the flue gas mass flowrate combined with the gass composition are used to determine the emitted CO2 and other by-products of combustion. Today, such measurements have uncertainties of 5% or more due to the large size of the flue-gas stacks and the flows non-uniform, unsteady, and swirling profile. A LWAF averages the spatial non-uniformities of the axial velocity over the entire cross section in a manner insensitive to flow distortions. In contrast, conventional techniques measure gas flow only at isolated points or averaged along chord across the stack. We constructed a 1:100 scale, calibrated flow facility for the initial development of a LWAF. In preliminary tests of three flow metering methods, uncertainties ranged from 1.4% to 4.9%, compared to our target uncertainty of 1%. We present the principle behind the LWAF, our design considerations, and the current performance of time and frequency-based approaches to metering, and describe technical challenges that must be overcome to use a LWAF at a full-scale power plant.
8th International Symposium on Fluid Flow Measurement
June 18-22, 2012
Colorado Springs, CO
flow meter, acoustic, long-wavelength, calibration, frequency response function, sound propagation, greenhouse gas, power plant, emissions, flue gas