Abstract
The accumulation of particles in a turbulent flow of incompressible air with mono-dispersed solid particles inside a 90° pipe bend was simulated using ANSYS® Fluent (CFD), taking into account the effect of gravity, drag force and a bidirectional fluid-particle coupling. An analysis of the geometrical parameters and the structures of the secondary flow generated in a curved pipe (Dean vortices) was developed, thus determining the characteristic time scales of the flow. Four Stokes numbers (Stk) were formulated, whose values are calculated and studied from the numerical simulations performed. Two different particle sizes (d1 = 50 μm y d2 = 150 μm), at two different flow conditions (Re1 = 61,500 y Re2 = 173,972), and for three curvature ratios Rc/R = 1, 4 and 8 were studied. The flow was solved using a Eulerian–Lagrangian approach with a RNG k-ε turbulence model. Once the multiphase flow was solved and validated, the distribution and maximum particle concentration inside the 90° bend were presented. Additionally, the Stk numbers were calculated to estimate the possible particle concentration level for the different system configurations (dp, Re and Rc/R). It is concluded that, if all Stk numbers are less than one, relative concentration levels reach a minimum, while for Stk numbers larger than one, an increase in the maximum concentration inside the pipe bend was noticed.
Highlights
Particle-laden turbulent flows in curved pipes are essential components of almost all industrial process equipment, including power production, chemical and food industries, heat exchangers, nuclear reactors, and engine exhaust ducts, understanding their behavior is of great interest
In this work we address the problem of quantifying, by means of ad hoc Stokes numbers, the accumulation of solid particles carried by a turbulent air flow inside a 90◦
An effective way to study the accumulation inside the bend was presented through the results of concentration and distribution of particles inside the pipe, under the premise that, if there is an increase in concentration over time, it reveals particle accumulation
Summary
Particle-laden turbulent flows in curved pipes are essential components of almost all industrial process equipment, including power production, chemical and food industries, heat exchangers, nuclear reactors, and engine exhaust ducts, understanding their behavior is of great interest. In 1997, McFarland et al numerically studied a turbulent flow loaded with solid particles through a 90◦ bend pipe using RANS Equations) along with the Reynolds stress model to solve the transport phase flow field while accounting for turbulent fluctuations in the equation of motion of the particles. They developed an empirical model that considered the influence of Stokes number, Reynolds number and radius on particle accumulation [1]. Zhang et al (2012) carried out a systematic numerical study to generate the computational guidelines to model and validate the turbulent flow through curved pipes by means of RANS equations and Lagrangian tracking, using the commercial code ANSYS
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