Flow rate measurement in stacks with cyclonic flow – Error estimations using CFD modelling. (December 2018)

• Record Type: Journal Article
• Authors: Geršl, J.; Knotek, S.; Belligoli, Z.; Dwight, R.P.; Robinson, R.A.; Coleman, M.D.
• Is Part Of: Measurement. Volume 129(2018)
• Page Start: 167
• Page End: 183
• Publication Date: 2018-12
• Subjects: Emission measurement -- Flow measurement in stacks -- Cyclonic flow -- Pitot tube -- Ultrasonic flow meter -- CFD; Weights and measures -- Periodicals; Measurement -- Periodicals; Measurement; Weights and measures; Periodicals; 530.8
• DOI: 10.1016/j.measurement.2018.06.032
• Languages: English
• ISSNs: 0263-2241

Abstract

Highlights: Cyclonic flow in stacks significantly increases a flow rate measurement error. Change in orientation or height of a sampling grid changes error by several percent. Deviation of flow from axis of a Pitot tube increases error by several percent. CFD is a useful tool for optimisation of flow measurement setups in stacks. Abstract: Two methods of flow measurement in stacks are investigated to determine their errors in presence of cyclonic flow. One method – based on velocity measurements with a Pitot tube in a grid of points – is the standard reference method according to EN ISO 16911-1. The second method – ultrasonic flow measurement – is often used as the automated measurement system in stacks according to EN ISO 16911-2. Several typical stack configurations are considered and the flow field in the stacks is obtained using validated computational fluid dynamics (CFD) modelling with OpenFoam software. We show that possible errors of the standard reference method due to the cyclonic flow are significant compared to the requirements of the EU's Emissions Trading System. For the ultrasonic flow meter we compare various configurations (number, orientation, position) of the ultrasound beams and we demonstrate the flow profile pre-investigation by CFD as prescribed in section 8.3 of EN ISO 16911-2.