Reducing static pressure measurement errors to increase accuracy of air mass flow measurement

Abstract

Inlet air mass flow is one of the most important measurands in aero engine testing and should therefore be measured as accurately as possible. The design, validation and calibration of a new airmeter is here described. Sensitivity coefficients are determined for the individual parameters, which go into the calculation for air mass flow. Errors in the measurement of static and total pressure have the highest influence on the accuracy of air mass flow and they should therefore be measured as accurately as possible. Since static pressure is usually more uncertain than total pressure, methods are described, which reduce the errors in static pressure measurement. They are to a large extent caused by the shape of the static pressure tapping. Careful design, manufacturing and maintenance of static pressure tappings is the key to low uncertainties in static pressure measurement. A new method is described, which allows for continuous monitoring of the static pressure measurement, as well as total pressure measurement, thus maintaining the initial quality of air mass flow measurements over a longer period of usage in an industrial environment. This is based on the airmeter calibration and uses the circumferential distribution of the measurement errors.