A Experimental assessment on the influence of disturbed approaching flows on ultrasonic flow measurement
Name: MATHEUS FELLIPE DAMACENA
Publication date: 04/06/2024
Examining board:
Name |
Role |
|---|---|
| JULIANA BRAGA RODRIGUES LOUREIRO | Examinador Externo |
| RAMON SILVA MARTINS | Examinador Interno |
| RENATO DO NASCIMENTO SIQUEIRA | Presidente |
| ROGERIO RAMOS | Coorientador |
Summary: Ultrasonic flow meters (UFM) are usually the preferred choice in flare gas flow measurement. At the same time, flow measurement of flaring operations is generally regulated by laws and, in Brazil, regulations allow a maximum uncertainty of ±5%. The profile factor applied to ultrasonic flow measurement is a parameter that translates the mean velocity measured by the device to the mean flow velocity in flow rate calculation. In light of that, any error in the flow profile correction factor (FPCF) is directly transmitted to the flow rate measurement. Hence, researches on the effect of disturbed approaching flows to the UFM
and how tube fittings affect the profile factor are desired by the industry. In this work, two methodologies were applied to study the effects of curves in the profile factor. Firstly, the parameter is measured by means of Laser Doppler Velocimetry (LDV) in a closed-circuit wind tunnel, where the flow is recirculated by two 90° bends. Velocity profiles are taken for a Reynolds number range between 6.5 × 103 and 2.3 × 105 in three different tunnel setups with straight tube lengths upstream from the meter equal to 36.5D (configuration C1), 26.2D (configuration C2) and 15.9D (configuration C3). The maximum relative difference between the wind tunnel configurations is 2.2% at Re = 2.4 × 104 between C3 and C1, whilst the minimum is 0.8%, between C2 and C1 at Re = 1.3 × 104. The second methodology evaluates the profile factor for the wind tunnel in its open-circuit configuration in distinct curve arrangements at the entrance of the tunnel, while keeping the upstream straight path from the meter fixed. Velocity profiles are taken by LDV for a Reynolds number range between 5.6 × 103 and 2.9 × 105 in four different tunnel setups: a reference mounting without any curves (mounting M1), one bend (mounting M2), two bends on the same plane in an S shape (mounting M3) and two curves on orthogonal planes (mounting M4). By comparing the FPCF for the curve mountings and the reference, no curve setup, one may notice an overall behavior of the profile factor for mounting M4 equal to the tunnel setup without any bends. At the same time, for configurations M2 and M3 the profile factor magnitude is inferior to that for the reference wind tunnel. The maximum relative difference is 1.8% between M3 and M1 at Re = 2 × 105. Lastly, results for the profile factor are applied to ultrasonic flow measurements (UFM) performed in all four open-circuit wind tunnel setups. The mean velocity measured by UFM presented an overall deviation from the reference (true) velocity of 2%, which fulfil flare regulations.
