The Experts below are selected from a list of 10593 Experts worldwide ranked by ideXlab platform
Srečko Glodež - One of the best experts on this subject based on the ideXlab platform.
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computational assessment of the allowable static contact loading of a roller slewing bearing s case hardened raceway
International Journal of Mechanical Sciences, 2015Co-Authors: Peter Göncz, Miran Ulbin, Srečko GlodežAbstract:Abstract A computational model for the assessment of the static load capacity of roller-slewing bearings with a case-hardened raceway is presented in this paper. The proposed 3D numerical model considers different influential parameters (arbitrary roller geometry, actual mechanical properties of raceway׳s material, tilted contact between the roller and raceway segment, etc.) on the allowable contact loading between rollers and their raceway. Within this paper, three representative types of roller geometries and their effect on the static load capacity are investigated: a cylindrical roller ( ZR ), a logarithmical roller ( LN ) and a partially crowned roller ( ZB ). For each type of roller, two different criteria are then used to determine the limit contact loading: (i) permanent indentation criterion and (ii) subsurface damage criterion. The results of a comprehensive computational analysis have shown that there are significant differences between each roller type with regards to limit contact load. The other important influencing parameters are the case depth of the raceway and the tilt angle, which mainly depends on the bearing clearance, and the contact loading. The proposed model and results presented here may allow manufacturers to take into account some particularities of large slewing bearings to improve their static load capacity.
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Rolling Contact Fatigue Life Assessment of Induction Hardened Raceway
Procedia Engineering, 2014Co-Authors: Peter Göncz, Srečko GlodežAbstract:Abstract In this paper the assessment of the rolling contact fatigue life of an induction hardened raceway is presented. For determination of the equivalent subsurface stress distribution field in the raceway, 3D numerical model of the contact between the through hardened roller made of 100Cr6 steel and the surface hardened raceway made of 42CrMo4 was employed. The calculation of the contact fatigue life of the raceway was then carried out in the stress-life regime. Additionally, alternative HCF parameters for the 42CrMo4 steel in compression were experimentally determined with pulsating compression tests. For the experimental validation of computationally determined fatigue life of the induction hardened Raceways, test specimens for RCF bench were manufactured and their testing has started.
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computational model for determination of static load capacity of three row roller slewing bearings with arbitrary clearances and predefined raceway deformations
International Journal of Mechanical Sciences, 2013Co-Authors: Pete Goncz, Rok Potocnik, Srečko GlodežAbstract:Abstract A new computational model for determination of internal contact forces distribution and consequently the determination of acceptable load curves for static load capacity in three-row roller slewing bearings is presented in this paper. The proposed model considers some typical characteristics of large slewing bearings (possible structural ring deformations, non-parallel ring displacements, clearances, surface quenching of the raceway Raceways, etc.) and their influence on the bearing static capacity. For practical applicability of the model, vector approach is used for mathematical description of the bearing geometry and relative ring movements, together with the static force and moment equilibrium calculation. The model has been implemented into a computer code and it serves as a convenient engineering tool especially suitable for early stages of slewing bearings’ design. The proposed computational model has been used to determine the static load capacity of an actual three-row roller slewing bearing, where different geometric parameters, such as different predefined ring deformations, rollers sizes, roller profile modifications and tilted contact of rollers have been additionally analyzed. Computational analyses have shown that some of the investigated parameters have a significant influence on the static load capacity of analyzed slewing bearing.
Kimberly L. Ogden - One of the best experts on this subject based on the ideXlab platform.
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simulation of shading and algal growth in experimental Raceways
Algal Research-Biomass Biofuels and Bioproducts, 2019Co-Authors: George Khawam, Peter Waller, Song Gao, Scott J. Edmundson, Said Attalah, Michael H Huesemann, Kimberly L. OgdenAbstract:Abstract Many algae research groups use elevated experimental Raceways to characterize algal biomass productivity. Side walls and a relatively large paddlewheel shade the culture and lower productivity, particularly in winter and with low culture depth. This paper presents a four-step method to calculate shading for a given raceway shape: (1) develop a computational mesh of the inner surface geometry of the raceway; (2) offset the mesh horizontally in the x and y directions on the water surface as a function of wall height, solar zenith angle, and solar azimuth angle; (3) calculate the shaded area for each projected mesh with the shoelace algorithm; (4) use regression to develop a response surface for shaded area as a function of horizontal x and y offset. For each time step, the shaded area is calculated with the regression equation based on the x and y offset at that time step. The shading model was added to the Huesemann Algae Biomass Growth (HABG) model. In the model, productivity was sensitive to the assumed light distribution below the water surface. Shading and light distribution models were evaluated with biomass concentrations from three Regional Algal Feedstock Testbed (RAFT) experiments with three different species of algae. Averaging light in each layer resulted in higher calculated growth rate than calculating growth separately in shaded and unshaded areas. The Local Photon Flux Density Variable Light (LPFD_V) shading algorithm reduced the HABG estimate of productivity and improved the agreement with observed productivities. The LPFD_V RMSD values ranged between 0.01 and 0.07 g L−1 and the bias factors ranged between 0.9 and 1.1. Shaded area was sensitive to raceway orientation, water depth, and time of year. A north-south raceway orientation had less average shading in winter but more average shading in summer than an east-west orientation.
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Model of temperature, evaporation, and productivity in elevated experimental algae Raceways and comparison with commercial Raceways
Algal Research-Biomass Biofuels and Bioproducts, 2019Co-Authors: George Khawam, Peter Waller, Song Gao, Scott J. Edmundson, Mark S. Wigmosta, Kimberly L. OgdenAbstract:Abstract Elevated Experimental Raceways (EERs) have been used at many research sites in the United States to evaluate algal biomass productivity. This paper develops temperature and evaporation models for EERs and then evaluates whether the temperature profile and resultant productivity in an EER is representative of large-scale commercial Raceways. Open water surface evaporation and temperature models with shading algorithms were programmed in Python and calibrated with temperature and evaporation data from the EERs in the Regional Algal Feedstock Testbed (RAFT) experiments at the University of Arizona. The final calibrated model for EERs was named the EERTEM (Elevated Experimental Raceway Temperature and Evaporation Model). The energy balance algorithms in the Biomass Assessment Tool (BAT model) were also added to the Python code and used to develop temperature simulations of standard commercial paddlewheel Raceways. A comparison of BAT and EERTEM simulations indicated that EER temperature fluctuations are not representative of in ground commercial paddlewheel Raceways, primarily due to the buffering effect of soil heat flux in commercial Raceways. With the different temperature profiles, biomass productivities of three algae species in the EERs were compared to productivities in commercial Raceways. Differences in productivity between EERTEM and BAT model temperature profiles were observed when the maximum daytime temperature of one raceway was in the optimal growth range but the temperature of the other raceway exceeded or was below the optimal growth range.
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a comparison of nannochloropsis salina growth performance in two outdoor pond designs conventional Raceways versus the arid pond with superior temperature management
International Journal of Chemical Engineering, 2012Co-Authors: Braden J Crowe, Peter Waller, Said Attalah, Randy Ryan, Shweta Agrawal, Jonathan Van Wagenen, A Chavis, John A Kyndt, Murat Kacira, Kimberly L. OgdenAbstract:The present study examines how climatic conditions and pond design affect the growth performance of microalgae. From January to April of 2011, outdoor batch cultures of Nannochloropsis salina were grown in three replicate 780 L conventional Raceways, as well as in an experimental 7500 L algae raceway integrated design (ARID) pond. The ARID culture system utilizes a series of 8–20 cm deep basins and a 1.5 m deep canal to enhance light exposure and mitigate temperature variations and extremes. The ARID culture reached the stationary phase 27 days earlier than the conventional Raceways, which can be attributed to its superior temperature management and shallower basins. On a night when the air temperature dropped to −9°C, the water temperature was 18°C higher in the ARID pond than in the conventional Raceways. Lipid and fatty acid content ranged from 16 to 25% and from 5 to15%, respectively, as a percentage of AFDW. Palmitic, palmitoleic, and eicosapentaenoic acids comprised the majority of fatty acids. While the ARID culture system achieved nearly double the volumetric productivity relative to the conventional Raceways (0.023 versus 0.013 g L−1day−1), areal biomass productivities were of similar magnitude in both pond systems (3.47 versus 3.34 g m−2day−1), suggesting that the ARID pond design has to be further optimized, most likely by increasing the culture depth or operating at higher cell densities while maintaining adequate mixing.
Pete Goncz - One of the best experts on this subject based on the ideXlab platform.
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computational model for determination of static load capacity of three row roller slewing bearings with arbitrary clearances and predefined raceway deformations
International Journal of Mechanical Sciences, 2013Co-Authors: Pete Goncz, Rok Potocnik, Srečko GlodežAbstract:Abstract A new computational model for determination of internal contact forces distribution and consequently the determination of acceptable load curves for static load capacity in three-row roller slewing bearings is presented in this paper. The proposed model considers some typical characteristics of large slewing bearings (possible structural ring deformations, non-parallel ring displacements, clearances, surface quenching of the raceway Raceways, etc.) and their influence on the bearing static capacity. For practical applicability of the model, vector approach is used for mathematical description of the bearing geometry and relative ring movements, together with the static force and moment equilibrium calculation. The model has been implemented into a computer code and it serves as a convenient engineering tool especially suitable for early stages of slewing bearings’ design. The proposed computational model has been used to determine the static load capacity of an actual three-row roller slewing bearing, where different geometric parameters, such as different predefined ring deformations, rollers sizes, roller profile modifications and tilted contact of rollers have been additionally analyzed. Computational analyses have shown that some of the investigated parameters have a significant influence on the static load capacity of analyzed slewing bearing.
Peter Göncz - One of the best experts on this subject based on the ideXlab platform.
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computational assessment of the allowable static contact loading of a roller slewing bearing s case hardened raceway
International Journal of Mechanical Sciences, 2015Co-Authors: Peter Göncz, Miran Ulbin, Srečko GlodežAbstract:Abstract A computational model for the assessment of the static load capacity of roller-slewing bearings with a case-hardened raceway is presented in this paper. The proposed 3D numerical model considers different influential parameters (arbitrary roller geometry, actual mechanical properties of raceway׳s material, tilted contact between the roller and raceway segment, etc.) on the allowable contact loading between rollers and their raceway. Within this paper, three representative types of roller geometries and their effect on the static load capacity are investigated: a cylindrical roller ( ZR ), a logarithmical roller ( LN ) and a partially crowned roller ( ZB ). For each type of roller, two different criteria are then used to determine the limit contact loading: (i) permanent indentation criterion and (ii) subsurface damage criterion. The results of a comprehensive computational analysis have shown that there are significant differences between each roller type with regards to limit contact load. The other important influencing parameters are the case depth of the raceway and the tilt angle, which mainly depends on the bearing clearance, and the contact loading. The proposed model and results presented here may allow manufacturers to take into account some particularities of large slewing bearings to improve their static load capacity.
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Rolling Contact Fatigue Life Assessment of Induction Hardened Raceway
Procedia Engineering, 2014Co-Authors: Peter Göncz, Srečko GlodežAbstract:Abstract In this paper the assessment of the rolling contact fatigue life of an induction hardened raceway is presented. For determination of the equivalent subsurface stress distribution field in the raceway, 3D numerical model of the contact between the through hardened roller made of 100Cr6 steel and the surface hardened raceway made of 42CrMo4 was employed. The calculation of the contact fatigue life of the raceway was then carried out in the stress-life regime. Additionally, alternative HCF parameters for the 42CrMo4 steel in compression were experimentally determined with pulsating compression tests. For the experimental validation of computationally determined fatigue life of the induction hardened Raceways, test specimens for RCF bench were manufactured and their testing has started.
Peter Waller - One of the best experts on this subject based on the ideXlab platform.
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simulation of shading and algal growth in experimental Raceways
Algal Research-Biomass Biofuels and Bioproducts, 2019Co-Authors: George Khawam, Peter Waller, Song Gao, Scott J. Edmundson, Said Attalah, Michael H Huesemann, Kimberly L. OgdenAbstract:Abstract Many algae research groups use elevated experimental Raceways to characterize algal biomass productivity. Side walls and a relatively large paddlewheel shade the culture and lower productivity, particularly in winter and with low culture depth. This paper presents a four-step method to calculate shading for a given raceway shape: (1) develop a computational mesh of the inner surface geometry of the raceway; (2) offset the mesh horizontally in the x and y directions on the water surface as a function of wall height, solar zenith angle, and solar azimuth angle; (3) calculate the shaded area for each projected mesh with the shoelace algorithm; (4) use regression to develop a response surface for shaded area as a function of horizontal x and y offset. For each time step, the shaded area is calculated with the regression equation based on the x and y offset at that time step. The shading model was added to the Huesemann Algae Biomass Growth (HABG) model. In the model, productivity was sensitive to the assumed light distribution below the water surface. Shading and light distribution models were evaluated with biomass concentrations from three Regional Algal Feedstock Testbed (RAFT) experiments with three different species of algae. Averaging light in each layer resulted in higher calculated growth rate than calculating growth separately in shaded and unshaded areas. The Local Photon Flux Density Variable Light (LPFD_V) shading algorithm reduced the HABG estimate of productivity and improved the agreement with observed productivities. The LPFD_V RMSD values ranged between 0.01 and 0.07 g L−1 and the bias factors ranged between 0.9 and 1.1. Shaded area was sensitive to raceway orientation, water depth, and time of year. A north-south raceway orientation had less average shading in winter but more average shading in summer than an east-west orientation.
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Model of temperature, evaporation, and productivity in elevated experimental algae Raceways and comparison with commercial Raceways
Algal Research-Biomass Biofuels and Bioproducts, 2019Co-Authors: George Khawam, Peter Waller, Song Gao, Scott J. Edmundson, Mark S. Wigmosta, Kimberly L. OgdenAbstract:Abstract Elevated Experimental Raceways (EERs) have been used at many research sites in the United States to evaluate algal biomass productivity. This paper develops temperature and evaporation models for EERs and then evaluates whether the temperature profile and resultant productivity in an EER is representative of large-scale commercial Raceways. Open water surface evaporation and temperature models with shading algorithms were programmed in Python and calibrated with temperature and evaporation data from the EERs in the Regional Algal Feedstock Testbed (RAFT) experiments at the University of Arizona. The final calibrated model for EERs was named the EERTEM (Elevated Experimental Raceway Temperature and Evaporation Model). The energy balance algorithms in the Biomass Assessment Tool (BAT model) were also added to the Python code and used to develop temperature simulations of standard commercial paddlewheel Raceways. A comparison of BAT and EERTEM simulations indicated that EER temperature fluctuations are not representative of in ground commercial paddlewheel Raceways, primarily due to the buffering effect of soil heat flux in commercial Raceways. With the different temperature profiles, biomass productivities of three algae species in the EERs were compared to productivities in commercial Raceways. Differences in productivity between EERTEM and BAT model temperature profiles were observed when the maximum daytime temperature of one raceway was in the optimal growth range but the temperature of the other raceway exceeded or was below the optimal growth range.
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energy productivity of the high velocity algae raceway integrated design arid hv
Applied Engineering in Agriculture, 2015Co-Authors: Said Attalah, George Khawam, Peter Waller, Randy Ryan, Michael H HuesemannAbstract:Abstract. The original Algae Raceway Integrated Design (ARID) raceway was an effective method to increase algae culture temperature in open Raceways. However, the energy input was high and flow mixing was poor. Thus, the High Velocity Algae Raceway Integrated Design (ARID-HV) raceway was developed to reduce energy input requirements and improve flow mixing in a serpentine flow path. A prototype ARID-HV system was installed in Tucson, Arizona. Based on algae growth simulation and hydraulic analysis, an optimal ARID-HV raceway was designed, and the electrical energy input requirement (kWh ha -1 d -1 ) was calculated. An algae growth model was used to compare the productivity of ARID-HV and conventional Raceways. The model uses a pond surface energy balance to calculate water temperature as a function of environmental parameters. Algae growth and biomass loss are calculated based on rate constants during day and night, respectively. A 10 year simulation of DOE strain 1412 (Chlorella sorokiniana) showed that the ARID-HV raceway had significantly higher production than a conventional raceway for all months of the year in Tucson, Arizona. It should be noted that this difference is species and climate specific and is not observed in other climates and with other algae species. The algae growth model results and electrical energy input evaluation were used to compare the energy productivity (algae production rate/energy input) of the ARID-HV and conventional Raceways for Chlorella sorokiniana in Tucson, Arizona. The energy productivity of the ARID-HV raceway was significantly greater than the energy productivity of a conventional raceway for all months of the year.
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ARID Raceway Temperature Model Evaluation
Transactions of the ASABE, 2014Co-Authors: George Khawam, Peter Waller, Said Attalah, Randy D. RyanAbstract:Abstract. The ARID (Algae Raceway Integrated Design) raceway temperature model, written in Visual Basic for Applications, calculates algae culture temperature in ARID and conventional Raceways as a function of meteorological data from agricultural weather stations. The model is an atmospheric boundary layer model and uses energy balance terms from the Penman-Monteith equation. The original model used evapotranspiration, as calculated by the weather station, and assumed an average daily albedo. In this research, equations for albedo and for direct calculation of evaporation from atmospheric parameters were added to the ARID model. Albedo was calculated with the Fresnel equations. The Penman-Monteith model was adjusted for algae raceway evaporation rather than reference evapotranspiration. The new model components were calibrated with data from a 21-day algae growth experiment in the ARID raceway during winter 2011. The model was also adapted to model variable circulation times and heat transfer through a canal cover. In summary, this research improved and calibrated the ARID temperature model.
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Study of the flow mixing in a novel ARID raceway for algae production
Renewable Energy, 2014Co-Authors: Peter WallerAbstract:A novel flow field for algae Raceways has been proposed, which is fundamentally different from traditional paddlewheel-driven Raceways. To reduce freezing and heat loss in the raceway during cold time, the water is drained to a deep storage canal. The ground bed of the new raceway has a low slope so that water, lifted by propeller pump, can flow down in laterally-laid serpentine channels, relying on gravitational force. The flow rate of water is controlled so that it can overflow the lateral channel walls and mix with the main flow in the next lower channel, which thus creates a better mixing. In order to optimize the design parameters of the new flow field, methods including flow visualization, local point velocity measurement, and CFD analysis were employed to investigate the flow mixing features. Different combinations of channel geometries and water velocities were evaluated. An optimized flow field design and details of flow mixing are presented. The study offers an innovative design for large scale algae growth Raceways which is of significance to the algae and biofuel industry.
