A Three-Dimensional Time-Accurate Computational Fluid Dynamics Simulation of the Flow Field Inside a Vaneless Diffuser During Rotating Stall Conditions

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Michele Marconcini ◽  
Alessandro Bianchini ◽  
Matteo Checcucci ◽  
Giovanni Ferrara ◽  
Andrea Arnone ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Field ◽  
Mechanical Stability ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Dynamics Simulation ◽  
Regulation System ◽  
Vaneless Diffuser

An accurate characterization of rotating stall in terms of inception modality, flow structures, and stabilizing force is one of the key goals for high-pressure centrifugal compressors. The unbalanced pressure field that is generated within the diffuser can be in fact connected to a non-negligible aerodynamic force and then to the onset of detrimental subsynchronous vibrations, which can prevent the machine from operating beyond this limit. An inner comprehension on how the induced flow pattern in these conditions affects the performance of the impeller and its mechanical stability can therefore lead to the development of a more effective regulation system able to mitigate the effects of the phenomenon and extend the left-side margin of the operating curve. In the present study, a 3D-unsteady computational fluid dynamics (CFD) approach was applied to the simulation of a radial stage model including the impeller, the vaneless diffuser, and the return channel. Simulations were carried out with the TRAF code of the University of Florence. The tested rotor was an industrial impeller operating at high peripheral Mach number, for which unique experimental pressure measurements, including the spatial reconstruction of the pressure field at the diffuser inlet, were available. The comparison between experiments and simulations showed a good matching and corroborated the CFD capabilities in correctly describing also some of the complex unsteady phenomena taking place in proximity of the left margin of the operating curve.

A 3D Time-Accurate CFD Simulation of the Flow Field Inside a Vaneless Diffuser During Rotating Stall Conditions

2016 ◽  
Author(s):  
Michele Marconcini ◽  
Alessandro Bianchini ◽  
Matteo Checcucci ◽  
Giovanni Ferrara ◽  
Andrea Arnone ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Pressure Field ◽  
Mechanical Stability ◽  
Aerodynamic Force ◽  
Rotating Stall ◽  
Regulation System ◽  
Vaneless Diffuser ◽  
Return Channel ◽  
University Of Florence ◽  
The University

An accurate characterization of rotating stall in terms of inception modality, flow structures, and stabilizing force is one of the key goals for high-pressure centrifugal compressors. The unbalanced pressure field that is generated within the diffuser can be in fact connected to a non-negligible aerodynamic force and then to the onset of detrimental sub-synchronous vibrations which can prevent the machine from operating beyond this limit. An inner comprehension on how the induced flow pattern in these conditions affects the performance of the impeller and its mechanical stability can therefore lead to the development of a more effective regulation system able to mitigate the effects of the phenomenon and extend the left-side margin of the operating curve. In the present study, a 3D-unsteady CFD approach was applied to the simulation of a radial stage model including the impeller, the vaneless diffuser and the return channel. Simulations were carried out with the TRAF code of the University of Florence. The tested rotor was an industrial impeller operating at high peripheral Mach number, for which unique experimental pressure measurements, including the spatial reconstruction of the pressure field at the diffuser inlet, were available. The comparison between experiments and simulations showed a good matching and corroborated the CFD capabilities in correctly describing also some of the complex unsteady phenomena taking place in proximity of the left margin of the operating curve.

Experimental and simulation study of thermal accumulation in an enclosed vehicle

2019 ◽  
Vol 233 (14) ◽  
pp. 3621-3629
Author(s):  
Sing Ngie David Chua ◽  
Boon Kean Chan ◽  
Soh Fong Lim
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Dynamics Simulation ◽  
Computational Fluid Dynamics Simulation ◽  
Heat Accumulation ◽  
Ansys Fluent ◽  
Direct Exposure ◽  
Car Park

Thermal accumulation in a car cabin under direct exposure to sunlight can be extremely critical due to the risk of heatstroke especially to children who are left unattended in the car. There are very limited studies in the literature to understand the thermal behaviour of a car that is parked in an open car park space and the findings are mostly inconsistent among researchers. In this paper, the studies of thermal accumulation in an enclosed vehicle by experimental and computational fluid dynamics simulation approaches were carried out. An effective and economical method to reduce the heat accumulation was proposed. Different test conditions such as fully enclosed, fully enclosed with sunshade on front windshield and different combinations of window gap sizes were experimented and presented. Eight points of measurement were recorded at different locations in the car cabin and the results were used as the boundary conditions for the three-dimensional computational fluid dynamics simulation. The computational fluid dynamics software used was ANSYS FLUENT 16.0. The results showed that the application of sunshade helped to reduce thermal accumulation at car cabin by 11.5%. The optimum combination of windows gap size was found to be with 4-cm gap on all four windows which contributed to a 21.1% reduction in car cabin temperature. The results obtained from the simulations were comparable and in agreement with the experimental tests.

Three-Dimensional Computational Fluid Dynamics Prediction of Turbocharger Centrifugal Compression System Instabilities

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Rick Dehner ◽  
Ahmet Selamet
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Flow Reversal ◽  
Constant Speed ◽  
Local Flow ◽  
Stall Cells

The present work combines experimental measurements and unsteady, three-dimensional computational fluid dynamics predictions to gain further insight into the complex flow-field within an automotive turbocharger centrifugal compressor. Flow separation from the suction surface of the main impeller blades first occurs in the mid-flow range, resulting in local flow reversal near the periphery, with the severity increasing with decreasing flow rate. This flow reversal improves leading-edge incidence over the remainder of the annulus, due to (a) reduction of cross-sectional area of forward flow, which increases the axial velocity, and (b) prewhirl in the direction of impeller rotation, as a portion of the tangential velocity of the reversed flow is maintained when it mixes with the core flow and transitions to the forward direction. As the compressor operating point enters the region where the slope of the constant speed compressor characteristic (pressure ratio versus mass flow rate) becomes positive, rotating stall cells appear near the shroud side diffuser wall. The angular propagation speed of the diffuser rotating stall cells is approximately 20% of the shaft speed, generating pressure fluctuations near 20% and 50% of the shaft frequency, which were also experimentally observed. For the present compressor and rotational speed, flow losses associated with diffuser rotating stall are likely the key contributor to increasing the slope of the constant speed compressor performance curve to a positive value, promoting the conditions required for surge instabilities. The present mild surge predictions agree well with the measurements, reproducing the amplitude and period of compressor outlet pressure fluctuations.

Transient Simulation of a Three-Dimensional Moving Downburst

2012 ◽  
Vol 446-449 ◽  
pp. 3875-3878
Author(s):  
Bai Feng Ji ◽  
Wei Lian Qu
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Wind Field ◽  
Three Dimensional ◽  
Simulation Method ◽  
Transient Simulation ◽  
Dynamics Simulation ◽  
Transmission Tower ◽  
Transient Wind

Thunderstorm microbursts, which are sources of extreme wind loadings in nature, have caused numerous structural failures, especially collapses of transmission tower around the world. Numerical simulation using computational fluid dynamics (CFD) has recently made significant progress in simulating downbursts. In this paper, transient simulation of a three-dimensional moving downburst was studied using computational fluid dynamics simulation method. Transient simulation of a three-dimensional moving downburst was conducted using time-filtered Reynolds Averaged Navier-Stokes (RANS) numerical simulation method. The three-dimensional transient wind field characteristics in a moving downburst were studied in detail. The results indicate that transient wind field characteristics in a moving downburst present quite different characteristics compared with stationary downburst at different heights and radial positions.

Research on Pressure Field of Hydrostatic Center Rest

2013 ◽  
Vol 427-429 ◽  
pp. 262-265
Author(s):  
De Fan Zhou ◽  
Qi Hui Zhou ◽  
Xiu Li Meng ◽  
Xiao Dong Yu ◽  
Zhi Qiang Wang ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Pressure Distribution ◽  
Pressure Field ◽  
Rotation Speed ◽  
Three Dimensional ◽  
Mechanical Deformation ◽  
Cavity Pressure ◽  
Distribution Law

In order to solve the mechanical deformation of the hydrostatic center rest, a numerical simulation concerning pressure field of hydrostatic center rest is studied. CFX of ANSYS has been used to compute three-dimensional pressure field of gap fluid between workpiece and bearing pillow. This research analyzes the influence of rotation speed on the bearing pressure performance according to lubricating theory and computational fluid dynamics, and it has revealed its pressure distribution law of gap oil film. Results indicate that an improved characteristic will be affected by rotation speed easily, and oil cavity pressure increases by gradually with rotation speed enhancing. The reliability of a hydrostatic center rest can be predicted through this method.

Microscale Computational Fluid Dynamics Simulation for Wind Mapping Over Complex Topographic Terrains

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Ashkan Rasouli ◽  
Horia Hangan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Spatial Resolution ◽  
Three Dimensional ◽  
Dynamics Simulation ◽  
Scale Model ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Wide Range ◽  
Wind Mapping

Wind mapping is of utmost importance in various wind energy and wind engineering applications. The available wind atlases usually provide wind data with low spatial resolution relative to the wind turbine height and usually neglect the effect of topographic features with relatively large or sudden changes in elevation. Two benchmark cases are studied for computational fluid dynamics (CFD) model evaluation on smooth two-dimensional (2D) and three-dimensional (3D) hills. Thereafter, a procedure is introduced to build CFD model of a complex terrain with high terrain roughness heights (dense urban area with skyscrapers) starting from existing topography maps in order to properly extend the wind atlas data over complex terrains. CFD simulations are carried out on a 1:3000 scale model of complex topographic area using Reynolds averaged Navier–Stokes (RANS) equations along with shear stress transport (SST) k-ω turbulence model and the results are compared with the wind tunnel measurements on the same model. The study shows that CFD simulations can be successfully used in qualifying and quantifying the flow over complex topography consisting of a wide range of roughness heights, enabling to map the flow structure with very high spatial resolution.

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