Test and Simulation of the Effects of Surface Roughness on a Shrouded Centrifugal Impeller

2014 ◽  
Author(s):  
William T. Cousins ◽  
Lei Yu ◽  
Jacquelynn Garofano ◽  
Barbara Botros ◽  
Vishnu Sishtla ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Cfd Simulation ◽  
Centrifugal Impeller ◽  
Test Results ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
The Common ◽  
R Value ◽  
The Impact ◽  
Grain Roughness

Surface roughness is an important parameter in the operational efficiency and loss development of turbomachinery components. Many computational fluid dynamics (CFD) simulations are performed on turbomachinery, but often one of the common assumptions is that the surfaces are hydraulically smooth. In this work, examination of the surfaces of two cast impellers is performed and compared to machined impellers with smoother surfaces. Both impeller sets were run in a two-stage industrial chiller unit using R134a refrigerant. Test results are presented and the impact of surface roughness modeling on the design is reviewed. Also discussed is the theory of the impact of roughness on turbulent boundary layers. Details about providing the CFD simulation with the proper sand grain roughness is discussed when surface finish (R-value) in microinches (μin) is measured.

Effect of Buoyancy and Density Ratio on Heat Transfer in a Smooth Cooling Channel of a Gas Turbine Blade

2018 ◽  
Author(s):  
Mandana S. Saravani ◽  
Saman Beyhaghi ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Rotational Speed ◽  
Cfd Simulation ◽  
Density Ratio ◽  
Reynolds Numbers ◽  
Buoyancy Effect ◽  
Square Channel ◽  
First Case ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

The present work investigates the effects of buoyancy and density ratio on the thermal performance of a rotating two-pass square channel. The U-bend configuration with smooth walls is selected for this study. The channel has a square cross-section with a hydraulic diameter of 5.08 cm (2 inches). The lengths of the first and second passes are 514 mm and 460 mm, respectively. The turbulent flow enters the channel with Reynolds numbers of up to 34,000. The rotational speed varies from 0 to 600 rpm with the rotational numbers up to 0.75. For this study, two approaches are considered for tracking the buoyancy effect on heat transfer. In the first case, the density ratio is set constant, and the rotational speed is varied. In the second case, the density ratio is changed in the stationary case, and the effect of density ratio is discussed. The range of Buoyancy number along the channel is 0–6. The objective is to investigate the impact of Buoyancy forces on a broader range of rotation number (0–0.75) and Buoyancy number scales (0–6), and their combined effects on heat transfer coefficient for a channel with aspect ratio of 1:1. Several computational fluid dynamics (CFD) simulation are carried out for this study, and some of the results are validated against experimental data.

The Impact of Predried Lignite Cofiring With Hard Coal in an Industrial Scale Pulverized Coal Fired Boiler

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Halina Pawlak-Kruczek ◽  
Robert Lewtak ◽  
Zbigniew Plutecki ◽  
Marcin Baranowski ◽  
Michal Ostrycharczyk ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Bituminous Coal ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Industrial Scale ◽  
Hard Coal ◽  
Cfd Simulations ◽  
Reference Case ◽  
The Impact

The paper presents the experimental and numerical study on the behavior and performance of an industrial scale boiler during combustion of pulverized bituminous coal with various shares of predried lignite. The experimental measurements were carried out on a boiler WP120 located in CHP, Opole, Poland. Tests on the boiler were performed during low load operation and the lignite share reached over to 36% by mass. The predried lignite, kept in dedicated separate bunkers, was mixed with bituminous coal just before the coal mills. Computational fluid dynamic (CFD) simulation of a cofiring scenario of lignite with hard coal was also performed. Site measurements have proven that cofiring of a predried lignite is not detrimental to the boiler in terms of its overall efficiency, when compared with a corresponding reference case, with 100% of hard coal. Experiments demonstrated an improvement in the grindability that can be achieved during co-milling of lignite and hard coal in the same mill, for both wet and dry lignite. Moreover, performed tests delivered empirical evidence of the potential of lignite to decrease NOx emissions during cofiring, for both wet and dry lignite. Results of efficiency calculations and temperature measurements in the combustion chamber confirmed the need to predry lignite before cofiring. Performed measurements of temperature distribution in the combustion chamber confirmed trend that could be seen in the results of CFD. CFD simulations were performed for predried lignite and demonstrated flow patterns in the combustion chamber of the boiler, which could prove useful in case of any further improvements in the firing system. CFD simulations reached satisfactory agreement with the site measurements in terms of the prediction of emissions.

scholarly journals Numerical and experimental analyses for the improvement of surface instant decontamination technology through biocidal agent dispersion: Potential of application during pandemic

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0251817
Author(s):  
Paulo Roberto Freitas Neves ◽  
Turan Dias Oliveira ◽  
Tarcísio Faustino Magalhães ◽  
Paulo Roberto Santana dos Reis ◽  
Luzia Aparecida Tofaneli ◽  
...  
Keyword(s):  
Experimental Tests ◽  
Cfd Simulations ◽  
New Device ◽  
Qualitative And Quantitative ◽  
Droplet Concentration ◽  
Computational Fluid Dynamics Cfd ◽  
Suspended Droplet ◽  
The Impact ◽  
Disinfection Chamber ◽  
Important Form

The transmission of SARS-CoV-2 through contact with contaminated surfaces or objects is an important form of transmissibility. Thus, in this study, we evaluated the performance of a disinfection chamber designed for instantaneous dispersion of the biocidal agent solution, in order to characterize a new device that can be used to protect individuals by reducing the transmissibility of the disease through contaminated surfaces. We proposed the necessary adjustments in the configuration to improve the dispersion on surfaces and the effectiveness of the developed equipment. Computational Fluid Dynamics (CFD) simulations of the present technology with a chamber having six nebulizer nozzles were performed and validated through qualitative and quantitative comparisons, and experimental tests were conducted using the method Water-Sensitive Paper (WSP), with an exposure to the biocidal agent for 10 and 30 s. After evaluation, a new passage procedure for the chamber with six nozzles and a new configuration of the disinfection chamber were proposed. In the chamber with six nozzles, a deficiency was identified in its central region, where the suspended droplet concentration was close to zero. However, with the new passage procedure, there was a significant increase in wettability of the surface. With the proposition of the chamber with 12 nozzles, the suspended droplet concentration in different regions increased, with an average increase of 266%. The experimental results of the new configuration proved that there was an increase in wettability at all times of exposure, and it was more significant for an exposure of 30 s. Additionally, even in different passage procedures, there were no significant differences in the results for an exposure of 10 s, thereby showing the effectiveness of the new configuration or improved spraying and wettability by the biocidal agent, as well as in minimizing the impact caused by human factor in the performance of the disinfection technology.

CFD simulation of empty fuel tanks separation from a trainer jet

2020 ◽  
Vol 92 (10) ◽  
pp. 1459-1468
Author(s):  
Aleksander Olejnik ◽  
Adam Dziubiński ◽  
Łukasz Kiszkowiak
Keyword(s):  
Cfd Simulation ◽  
Body Movement ◽  
Cfd Simulations ◽  
Content Type ◽  
Sequential Release ◽  
Wind Tunnel Data ◽  
Computational Fluid Dynamics Cfd ◽  
External Forces ◽  
Additional Value ◽  
Control Surfaces

Purpose This study aims to create 6-degree of freedom (SDOF) for computational fluid dynamics (CFD) simulations of body movement, and to validate using the experimental data for empty tank separation from I-22 Iryda jet trainer. The procedure has an ability to be modified or extended, to simulate, for example, a sequential release from the joints. Design/methodology/approach A set of CFD simulations are calculated. Both the SDOF procedure and the CFD simulation settings are validated using the wind tunnel data available for the aircraft. Findings The simulation using designed procedure gives predictable results, but offers availability to be modified to represent external forces, i.e. from body interaction or control system without necessity to model the control surfaces. Practical implications The procedure could be used to model the separation of external stores and design the deployment of anti-radar chaff, flares or ejection seats. Originality/value The work presents original work, caused by insufficient abilities of original SDOF procedure in ANSYS code. Additional value is the ability of the procedure to be easily modified.

scholarly journals Thermal management of machine compartment in a built-in refrigerator

2018 ◽  
Vol 240 ◽  
pp. 05005
Author(s):  
Milind Devle ◽  
Ankur Garg ◽  
Darci Cavali
Keyword(s):  
Heat Exchange ◽  
Cfd Simulation ◽  
Heat Extraction ◽  
Free Standing ◽  
Cfd Simulations ◽  
Performance Effectiveness ◽  
Hot Air ◽  
Computational Fluid Dynamics Cfd ◽  
Major Factors ◽  
Side Gap

In general a multi-door refrigerator machine compartment comprises of fan, condenser, compressor, control box, drain tray, and drain tubes. The performance of machine compartment depends upon the efficiency of heat extraction or heat exchange from heat generating components such as condenser and compressor. The efficiency of heat exchange can be improved by addressing two major factors, namely (1) Air bypass and (2) Hot air recirculation. The hot air recirculation in the machine compartment for builtin multi-door refrigerator configuration is the focus of this study. The results from Computational Fluid Dynamics (CFD) simulations show that efficiency of heat exchange for built-in application is lower than that for free-standing configuration. Recirculation of hot air and reduction in airflow are the two major factors which contribute towards the variation in machine compartment performance. The CFD simulations were coupled with Partial Factorial Design of Experiment (DoE) approach to systematically investigate the effect of variables such as (a) side gap and top gap between kitchen cabinetry and the refrigerator, (b) the baffle/flap (i.e. back and bottom of machine compartment) on the performance effectiveness of machine compartment. The results of the simulation provided critical design improvement directions resulting in performance improvement. Furthermore, the CFD simulation results were also compared to test data and the results compared favourably.

Transient CFD Visualization of Fossil Fuel Combustion Simulations

2003 ◽  
Author(s):  
Brian Dotson ◽  
Kent Eshenberg ◽  
Chris Guenther ◽  
Thomas O’Brien
Keyword(s):  
Power Plants ◽  
High Efficiency ◽  
Cfd Simulation ◽  
Low Cost ◽  
Three Dimensional ◽  
Cfd Simulations ◽  
Projection System ◽  
Computational Fluid Dynamics Cfd ◽  
High Level ◽  
Wall System

The design of high-efficiency lower-emission coal-fed power plants is facilitated by the extensive use of computational fluid dynamics (CFD) simulations. This paper describes work conducted at the National Energy Technology Laboratory (NETL) and Pittsburgh Supercomputing Center (PSC) to provide an environment for the immersive three-dimensional visualization of CFD simulation results. A low-cost high-resolution projection system has been developed in the visualization lab at NETL. This multi-wall system consists of four projection screens, three of which are tiled into four quadrants. The graphics for the multi-wall system are rendered using a cluster of eight personal computers. A high-level visualization interface named Mavis has also been developed to combine the powerful 3D modules of OpenDX with methods developed at NETL for studying multiphase CFD data. With Python, a completely new OpenDX user interface was built that extends and simplifies the features of a basic graphics library.

An Analytical and Experimental Assessment of a Diffuser Flow Phenomenon as a Precursor to Stall

2012 ◽  
Author(s):  
James M. Sorokes ◽  
Jorge E. Pacheco ◽  
Clementine Vezier ◽  
Syed Fakhri
Keyword(s):  
Rotating Stall ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Test Results ◽  
Vaneless Diffuser ◽  
Diffuser Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses ◽  
Validation Testing ◽  
Lower Flow Rate

The paper describes an experimental and analytical study on the vaneless diffuser downstream of a high flow coefficient, high inlet relative Mach number centrifugal impeller. The diffuser flowfield exhibited a unique behavior in which the low momentum zone typically found along the shroud side of a centrifugal compressor diffuser suddenly shifted to the hub side of the diffuser just prior to the onset of diffuser rotating stall. The phenomenon was observed in the computational fluid dynamics (CFD) analyses conducted as well as in the experimental data obtained during stage validation testing. A review of the analytical and test results suggested that the phenomenon was at least partially attributable to the level of diffusion in the vaneless diffuser. Modifications made to reduce the diffusion rate were shown by CFD analysis to move the onset of the unusual shift of low momentum flow to a much lower flow rate. The modifications also increased the efficiency of the overall stage by 1.2%.

Vibratory Finishing of Immobilized Cylinders

2012 ◽  
Vol 565 ◽  
pp. 278-283 ◽  
Author(s):  
Stephen Wan ◽  
Takashi Sato ◽  
Andry Hartawan
Keyword(s):  
Surface Roughness ◽  
Flow Field ◽  
Granular Flow ◽  
Flow Direction ◽  
General Purpose ◽  
Vibratory Finishing ◽  
Cfd Simulations ◽  
Dense Granular Flow ◽  
The Media ◽  
Computational Fluid Dynamics Cfd

We report preliminary results from an on-going study investigating the effect of fixing workpieces within the media flow field contained in a typical vibratory finishing bowl. To this end, we studied the surface roughness evolution over the surfaces of workpieces with generic geometries such as cylinders. A granular flow dynamics model applicable to dense granular flow and a previously derived process equation were invoked in order to respectively describe the flow of the abrasive media; and the roughness distribution in terms of the granular pressure and velocity. By solving the granular flow field for the pressure and velocity distribution on a given geometry using a general purpose computational fluid dynamics (CFD) code, we were able to analyse changes in surface roughness distribution from the process equation. The immobilized cylinders were submerged in the top portion of the media flow field so as to facilitate comparison between media flow past the workpieces as experimentally observed and as predicted by the CFD simulations. We conclude with an analysis, based on both experimental and predicted results, of the way in which media flow direction biases the surface roughness distribution on an immobilized cylinder.

scholarly journals De-risking flight trials using airwake simulations

2018 ◽  
Author(s):  
C M Ward
Keyword(s):  
Royal Navy ◽  
Exposure Limits ◽  
Cfd Simulations ◽  
Real Time System ◽  
Flow Features ◽  
Operating Limits ◽  
Turbulent Airflow ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Rotary Wing

Air operations around naval vessels are inherently challenging and a major contributor to this is the turbulent airflow around the vessels, colloquially known as the airwake. To manage the risks associated with these unsteady airflows and to help define safe operating limits for the ship and the aircraft, the Royal Navy undertakes First of Class Flight Trials (FOCFTs). However, these trials inherently carry their own risks as well as being costly and time consuming. This paper discusses how Computational Fluid Dynamics (CFD) simulations have been used to de-risk flight trials and operations on the Queen Elizabeth Class (QEC) carriers. The simulations are shown to be in excellent agreement with full-scale LiDAR and anemometer measurements, which provides the requisite confidence to use them as a basis for de-risking. To de-risk the rotary wing FOCFTs, the turbulence approach parameter was defined as a proxy for pilot workload. It is shown that this parameter can be used to identify the wind conditions that are likely to be the most difficult for pilots, and to advise on changes to the approach paths that would reduce pilot workload. Test pilots were briefed with this airwake information prior to the FOCFTs, and the flow features identified in the CFD were found to be consistent with the pilots’ experiences. In the future this analysis could be used to reduce the time and cost associated with flight trials, manage through-life risks, and assess the impact of design decisions on the airwake during ship design. The work has also been used to de-risk F-35 trials and operations. In particular, the findings show that it may be possible to extend the operating envelope of the aircraft using a novel real-time system to predict airwake turbulence. In addition, CFD simulations were used to de-risk ondeck operations by ensuring that aircraft are within their exposure limits when tied-down. This information was used by the FOCFTs teams during rotary wing trials.

scholarly journals Crude Oil Fouling in Heat Exchangers: A Study on Effects of Influencing Forces

2021 ◽  
Vol 287 ◽  
pp. 03003
Author(s):  
Sampath Emani ◽  
M. Ramasamy ◽  
Ku Zilati Ku Shaari
Keyword(s):  
Surface Roughness ◽  
Crude Oil ◽  
Flow Velocity ◽  
Deposition Rate ◽  
Heat Exchangers ◽  
Cfd Simulations ◽  
Deposition Velocities ◽  
Computational Fluid Dynamics Cfd ◽  
Lower Temperature ◽  
Oil Fouling

One of the major concerns in petroleum refinery preheat trains is identified as fouling. Fouling impacts the refinery economics and environment heavily. Various approaches to mitigate fouling have not yielded the desired results. This is due to lack of understanding on the effect of influencing forces on crude oil fouling in heat exchangers. Therefore, this study attempts to investigate the effects of various forces such as gravity, Saffman Lift, drag and thermophoretic on crude oil fouling in heat exchangers through Computational Fluid Dynamics (CFD) simulations. From the simulations, it is observed that the higher particle size and particle concentration resulted in higher deposition of particles. Deposition velocities increase for larger sized particles and decrease for small and medium sized particles. The Increased flow velocities and surface roughness increases wall shear and mitigate fouling. Lower temperature gradients at the heat exchanger surface decreases deposition rates due to high thermophoretic forces. The mass deposition rate is reduced by 10.3 and 16.9% with 0.03 and 0.05 Pa, respectively, for 0.14 m/s flow velocity. Also, the mass deposition rate is reduced by 15.6 and 25.1% with 0.03 and 0.05 Pa, respectively, for 0.47 m/s flow velocity. With increased surface roughness from 0.03 to 0.05 mm, the mass deposition rate is reduced by 11.48 and 19.18%, respectively, for 0.14 m/s flow velocity. Also, for 0.47 m/s flow velocity, the mass deposition rate is reduced by 18.84 and 32.92% for 0.03- and 0.05-mm surface roughness, respectively.

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