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Aaron Johnson

Dr. Aaron Johnson is a mechanical engineer with expertise in fluid dynamics and flow measurement. His interests include measuring flue gas flows, measuring pipeline-scale natural gas flows, designing primary flow standards, analyzing the uncertainty of flow measurements, computational fluid dynamics, and modeling flow meters (e.g., critical flow venture meters, turbine meters, ultrasonic meters).

Dr. Johnson has leadership roles in three projects:

  1. developing a scale-model smokestack simulator. The simulator's diameter (1.2 m) is approximately 1/10th the diameter of the stack of a typical, coal-fired power plant. The simulator will (a) quantify the accuracy of flow meters used in smokestacks, (b) quantify uncertainties of stack-flow measurement protocols, and (c) test alternative, low-uncertainty flow-measurement technologies (e.g., long-wavelength acoustic meters, multipath ultrasonic techniques). By facilitating accurate stack flow measurements with quantified uncertainties, the simulator supports programs that place a price on the emissions of coal-burning power plants.
  2. developing and maintaining NIST's internationally-recognized, natural gas flow calibration service that provides industry low-uncertainty (0.22 % to 0.4 %) flow measurements. These measurements are traceable to primary flow standards developed and maintained by NIST. Flow meters serve as "cash registers" during custody transfers of natural gas; they determining the money exchanged between buyers and sellers. NIST's natural gas calibration service facilitates equitable custody transfer within the U.S. and in international commerce.
  3. improving gas flow meter calibrations performed under non-ideal flow conditions including (a) swirling, asymmetric flows typical of smokestacks, and (b) transient and quasi-stable flows typical of blow-down methods. Blow-down methods are used to calibrate meters with flows that are too large (> 10 kg/s) to maintain in a steady state laboratories. To facilitate calibrations under these non-ideal circumstances, Johnson is "taking the lab to the field;" thereby making NIST's calibrations more useful to its customers.

Publications

Improving Measurement for Smokestack Emissions - Workshop Summary

Author(s)
Rodney A. Bryant, Aaron N. Johnson, John D. Wright, Tamae M. Wong, James R. Whetstone, Michael R. Moldover, Iosif I. Shinder, Scott Swiggard, Chris Gunning, David Elam, Tom Martz, Eric Harman, David Nuckols, Liang Zhang, Woong Kang, Salvator Vigil
The complex flow conditions inherent in power plant smokestacks make accurate flow measurements challenging, which in turn limits the accuracy of hazardous

Progress Towards Accurate Monitoring of Flue Gas Emissions

Author(s)
Aaron N. Johnson, Iosif I. Shinder, Michael R. Moldover, Joey T. Boyd, Bernard J. Filla
The amounts of CO2 and other pollutants emitted by a coal-fired power plant are measured using a continuous emissions monitoring system (CEMS) permanently

Errors in Rate of Rise Gas Flow Measurements from Flow Work

Author(s)
John D. Wright, Aaron N. Johnson, Gina M. Kline, Michael R. Moldover
The rate of rise (RoR) method measures the time rate of change of the mass of gas in a collection volume as it is filled via a flow meter under test. The mass
Created April 2, 2019