A finite element overlapping scheme for turbomachinery flows on parallel platforms

Proceedings of the Institution of Mechanical Engineers, Part A:

Sheard³

2007

The application of improved blade tip geometries is studied with the aim of identifying an effective design concept for industrial fan passive noise control. The concept developed optimizes a datum blade by means of profiled endplates at the tip, reducing fan noise by changing the tip leakage flow behaviour. Experimental and computational investigations have been carried out on a family of axial fans, in fully ducted configuration, to establish the aerodynamic merits of the proposed blade tip design concept. The flow mechanisms in the fan tip region are correlated to specific blade design features that promote a reduction of the fan aero-acoustic signature in both tonal and broadband noise components. The tip vortical flow structures are characterized, and their role in creation of overall stage acoustic emissions clarified. The reported research identifies modification of tip geometry as markedly affecting the multiple vortex behaviour of blade tip leakage flow by altering the near-wall fluid flow paths on both blade surfaces. Blade tip endplates were also demonstrated to influence the rotor loss behaviour in the blade tip region. Improvement of rotor efficiency was correlated to the control of tip leakage flows

Section: Numerical Procedures and Axial Fan Modellingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Development of improved blade tip endplate concepts for low-noise operation in industrial fans

Proceedings of the Institution of Mechanical Engineers, Part A:

Sheard³

2007

“…To this end, the authors adopt a RANS model based on a non-linear twoequation closure [15], used to cope with non-isotropic and non-equilibrium turbulence effects at reduced computational costs. The numerical scheme is a parallel multigrid (MG) method developed for the in-house developed nite element (FEM) code rst proposed by Borello et al [16]. The FEM formulation is based on a highly accurate stabilized Petrov-Galerkin (PG) method modi ed for application to three-dimensional equal-and mixed-order spaces of approximation.…”

Section: Introductionmentioning

confidence: 99%

Using sweep to extend the stall-free operational range in axial fan rotors

Proceedings of the Institution of Mechanical Engineers, Part A:

2004

117

The paper discusses the use of sweep as a remedial strategy to control the aerodynamic limits in low-speed axial fan rotors. In this respect, the present work contributes to the understanding of the potential effect of blade lean on the shifting of the rotor stall margin. Numerical investigations have been undertaken on highly loaded fans of non-free vortex design, with the ideal total head rise coefficient typical of the industrial application range. Two rotors with identical nominal design parameters and, respectively, with 35° forward swept blades and unswept blades have been studied. The investigation has been carried out using an accurate in-house developed multilevel parallel finite element RANS solver, with the adoption of a non-isotropic two-equation turbulence closure. The pay-off derived from the sweep technology has been assessed with respect to the operating range improvement. To this end, the flow structure developing through the blade passages and downstream of the rotors, as well as loss distributions, have been analysed at design and near-peak pressure operating conditions. The analyses of three-dimensional flow structures showed that, sweeping forward the blade, the non-free vortex spanwise secondary flows are attenuated, and a control on the onset of stall is recovered. Moreover, the swept rotor features a reduced sensitivity to leakage flow effects. Consequently, it operates more efficiently approaching the throttling limit.

“…The authors solved the Reynoldsaveraged Navier-Stokes equations by an original parallel multigrid finite element flow solver [15], using C-| -I-technology and libMesh libraries [16]. They modeled the physics involved in the fluid dynamics of incompressible 3D turbulent flows in a rotating frame of reference with a nonlinear k-e model [30], here in its topology-free low-Reynolds variant.…”

Section: Vdriftmentioning

confidence: 99%

“…The authors adopted a parallel multigrid scheme developed for an in-house finite element method (FEM) solver [15], utilizing the C-l-l-libMesh libraries [16]. They based the FEM formulation on an accurate and stabilized specially designed Petrov-Galerkin (PG) scheme for turbomachinery CFD [17].…”

Section: Introductionmentioning

confidence: 99%

Predicting Blade Leading Edge Erosion in an Axial Induced Draft Fan

Marchegiani

Journal of Engineering for Gas Turbines and Power

et al. 2012

Induced draft fans extract coal flred boiler combustion products, including particles of un-burnt coal and ash. As a consequence of the particles, the axial fan blades' leading edges are subject to erosion. Erosion results in the loss of the blade leading edge aerodynamic proflle and a reduction of blade chord and effective camber that together degrade aerodynamic performance. An experimental study demonstrated that while the degradation of aerodynamic performance begins gradually, it collapses as blade erosion reaches a critical limit. This paper presents a numerical study on the evolution of blade leading edge erosion patterns in an axial induced draft fan. The authors calculated particle trajectories using an in-house computational fluid dynamic (CED) solver coupled with a trajectory predicting solver based on an original finite element interpolation scheme. The numerical study clarifles the influence of flow structure, initial blade geometry, particle size, and concentration on erosion pattern.