The internal flow and the liquid structure at nozzle exit are investigated in a typical pressure swirl atomizer for aero-engine applications under isothermal non reacting environment, using a two-phase flow modeling according to the VOF numerical methodology. A parametrical analysis is performed to investigate the effect of operating conditions on the injector performances and the characteristics of the liquid jet exiting the nozzle. The liquid film thickness at nozzle exit and the injector discharge coefficient predicted by the simulations are compared against commonly used correlations available in the literature. The influence of the turbulence model on the injector performances is also analyzed using three different models: the RNG k-ε model, the Reynolds Stress Model (RSM) and the Large Eddy Simulation (LES) model.

Image-based computational fluid dynamics (CFD) has shown potential to aid in the clinical management of intracranial aneurysms, but its adoption in the clinical practice has been missing, partially because of lack of accuracy assessment and sensitivity analysis. To numerically solve the flow-governing equations, CFD solvers generally rely on 2 spatial discretization schemes: finite volume (FV) and finite element (FE). Since increasingly accurate numerical solutions are obtained by different means, accuracies and computational costs of FV and FE formulations cannot be compared directly. To this end, in this study, we benchmark 2 representative CFD solvers in simulating flow in a patient-specific intracranial aneurysm model: (1) ANSYS Fluent, a commercial FV-based solver, and (2) VMTKLab multidGetto, a discontinuous Galerkin (dG) FE-based solver. The FV solver's accuracy is improved by increasing the spatial mesh resolution (134k, 1.1m, 8.6m, and 68.5m tetrahedral element meshes). The dGFE solver accuracy is increased by increasing the degree of polynomials (first, second, third, and fourth degree) on the base 134k tetrahedral element mesh. Solutions from best FV and dGFE approximations are used as baseline for error quantification. On average, velocity errors for second-best approximations are approximately 1 cm/s for a [0,125] cm/s velocity magnitude field. Results show that high-order dGFE provides better accuracy per degree of freedom but worse accuracy per Jacobian nonzero entry as compared with FV. Cross-comparison of velocity errors demonstrates asymptotic convergence of both solvers to the same numerical solution. Nevertheless, the discrepancy between underresolved velocity fields suggests that mesh independence is reached following different paths.

This article describes a CFD engineering application developed to investigate numerically the multiphase, non-isothermal, turbulent flow physics within the suspension preheater of a dry-process rotary cement kiln. The multi–stage cyclone preheater is a counter-current heat exchanger. We used the CFD flow solver ANSYS-Fluent R18.1. to accomplish this task. The hybrid Eulerian multiphase-dense discrete phase model is a coupled Eulerian-Lagrangian technique. The primary carrier-phase is treated as a continuum by solving the Navier-Stokes equations, while the secondary discrete dispersed-phase is solved by tracking the particle parcels through the calculated flow field. The multiphase turbulence of the carrier-phase is modeled using the Reynolds stress transport model. The dispersed-phase interactions are modeled through the specific collisions models provided by the kinetic theory of granular flow and/or discrete element method. The Eulerian multiphase-DDPM method provided a quiet stable solution for a medium/high mass loading (solid to gas mass ratio 0.89:1). The four-stage cyclone suspension preheater is analyzed for its operating performance i.e. overall pressure drop and global collection efficiency of cyclone stages, calcination degree at bottom cyclone stage, flue gas temperature at 1st. cyclone stage and availability to get more insight of very complex multi-phase flow patterns within this equipment. The set of industrial measurements, collected during a heat and mass balance of a dry process rotary cement kiln, were used to verify and to validate part of the simulation results.

The paper presents a three-dimensional (3-D), time-dependent Euler-Lagrange multiphase approach for high-fidelity numerical simulation of strongly swirling, turbulent, heavy dust-laden flows within large-sized cyclone separators, as components of the state-of-art suspension preheaters (SPH) of cement kilns. The case study evaluates the predictive performance of the coupled hybrid 3-D computational fluid dynamics–dense discrete phase model (CFD-DDPM) approach implemented into the commercial general purpose code ANSYS-Fluent R16.2, when applied to industrial cyclone collectors used to separate particles from gaseous streams. The gas (flue gases) flow is addressed numerically by using the traditional CFD methods to solve finite volume unsteady Reynolds-averaged Navier-Stokes (FV-URANS) equations. The multiphase turbulence is modeled by using an option of Reynolds stress model (RSM), namely dispersed turbulence model. The motion of the discrete (granular) phase is captured by DDPM methodology. The twin cyclones of SPH top-most stage have been analyzed extensively both for the overall pressure drop and global collection efficiency, and for the very complex multiphase flow patterns established inside this equipment. The numerical simulation results have been verified and partially validated against an available set of typical industrial measurements collected during a heat and mass balance (H&MB) of the cement kiln.

Three dimensional, time dependent Euler-Euler simulation approach for numerical calculation of multiphase strongly swirling turbulent gas-heavy laden particulate flow in large industrial collection cyclones, positioned vertically, in staggered downward cascade arrangement has been performed. The multiphase flow was featured high mass loading. This paper specifically addresses a CFD modeling of a “suspension preheater”, typical equipment for dry process cement kiln. Big sized cyclone separator is a key component of this device. The simulation case study was developed in the frame of the commercial general-purpose code ANSYS-Fluent R13. In cyclone separators the swirling gas motion induces a centrifugal force on the solid particulate phase which is the driving force behind the separation process. The turbulence disperses the solid particulates and enhances the probability that particles are discharged, as reject. Both phenomena are related to solid phase particle size distribution (PSD) and flow pattern into the collection cyclones. The multiphase turbulence was modeled using the RSM Mixture Turbulence Model. The simulation results were validated against industrial measurements carried out on an industrial suspension preheater, in the frame of heat and mass balance of cement kiln energy audit. The numerical simulation results were found in reasonable agreement with the collected industrial measurements. This CFD simulation represents a powerful engineering tool on behalf of the cement process engineer either for new cutting-edge design or for performance verification of an existing plant.