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New probe designs, hardware, software, calibration procedures, and turbulence corrections to make accurate, rapid, non-nulling measurements of gas velocity in turbulent flows.

Patent Abstract: 

Accurately quantifying hazardous emissions from industrial smokestacks requires accurate gas velocity measurements made at points prescribed by the Environmental Protection Agency (EPA) on cross sections of the stack. Currently, the EPA approves probes that require a time-consuming “nulling procedure” whereby each probe must be rotated about its axis at each prescribed point to find the yaw component of velocity at that point. We developed a new non-nulling procedure that applies to EPA-sanctioned spherical pitot probes, thereby reducing the time and cost of such measurements. We designed new non-nulling pitot probes that measure the velocity more accurately than any EPA-sanctioned probe. The pressure-sensing holes in the new probe design are 3 to 6 times larger than the corresponding holes in the EPA-sanctioned 3-dimensional probes to mitigate plugging problems that occur when the flue gas has water droplets and/or particles. At present, EPA-sanctioned probes are calibrated in laminar wind tunnel flows and used in turbulent stack flows without accounting for turbulence intensity. Our wind tunnel measurements demonstrate that ignoring turbulence leads to over-estimating stack emissions by 5%, when the turbulence intensity is 10%. Our new probes, hardware, and software measure the turbulence intensity of the flue gas velocity and correct the measurements for the turbulence intensity.


Iosif I. Shinder, James B. Filla, Aaron N. Johnson

Internal Laboratory Ref #: 
Patent Status: 
Provisional 63/011,004
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