Analysis of operational parameters, distorted flow and damaged blade effects on accuracy of industrial crude oil turbine flow meter by CFD techniques

Abstract

Abstract This paper aims to investigate the effect of various flow rates, densities, and crude oil viscosities in the steady state condition of the industrial turbine flow meter performance (12 in. with 15 blades), utilizing CFD techniques. The governing equations include continuity, momentum, and rotor׳s torque balance, solved using finite volume method. The turbulence stress tensor in momentum equation was calculated by Realizable k–e turbulence model. Two approaches, stationary and rotational were studied in this work. In stationary model, the rotational torques were calculated from momentum balance and the blades were assumed as moving walls. In rotational model, the Multi Reference Frame (MRF) approach was used and torques were obtained from numerical results. The results, gained from stationary model, showed higher deviation from experimental data; in contrast, the rotational model depicted excellent agreement with experimental ones and therefore was selected as optimum approach in this study. For validation of the CFD model, first the results have been compared with reported experimental data for 15 mm turbine meter; the rotational model showed the average deviation of 3.35% against experimental data for turbine k-Factor. Second, the results for industrial case (12 in.) showed that k-Factor values are nearly constant when closes to 1690 pulse/m 3 compared to 1655 pulse/m 3 against in-situ data in operational flow rates range (2% error). It was depicted that the k-Factor promotes with enhancement of viscosity due to growing of boundary layer thickness on the rotor surface. Additionally, it was found that oil specific gravity changing from heavy to light crude oil decreases the k-Factor. Turbine meters are sensitive to entrance flow pattern and straighteners are used in upstream to produce non-swirling flow. The effect of distortion in entrance flow profile on meter accuracy was considered. The results for four different distorted flows (installation of meter near the elbow, clogging in central, upper and lateral pipes of straightener) were reported, as well; it was shown that k-Factor can change up to ±5% in comparison with the non-swirling flow (with intact straightener placed in upstream). The simulation of one damaged blade in the rotor against intact blades showed approximately 4% reduction in k-Factor.