scholarly journals NUMERICAL ESTIMATION ABOUT PERFORMANCE OF CPP AND PODDED PROPULSOR ON MANY OFF-DESIGN CONDITIONS USING RANS APPROACH

2019 ◽  
Author(s):  
K Himei ◽  
K Okazaki ◽  
H Yamaguchi
Keyword(s):  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Numerical Estimation ◽  
Propeller Blade ◽  
Steering Angle ◽  
Rotational Moment ◽  
Propeller Design ◽  
Podded Propulsor ◽  
Wide Range ◽  
The Common

On the off-design condition of CPP or podded propulsor, the angle of attack against the propeller blade or the flow interaction between propeller and pod housing is quite different from the propeller design condition. The flow around them is very complex. Hence there is the difficulty for numerical estimating. In order to verify the applicability to wide range of the off-design condition, RANS simulations were executed. The calculation range for CPP was complete two quadrant condition each at several pitch setting. Regarding podded propulsor, pull type and push one having the common propeller and housing were targeted and the range of pod steering angle were set to all 360 degrees. Hydrodynamic performance as these calculated results were compared with published experimental results including the rotational moment of changing CPP’s pitch angle or steering the pod housing. Then, it was found that there were good agreements except for the particular kind of the operating conditions.

Influence of Stator Blade Geometry on Torque Converter Cavitation

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Cheng Liu ◽  
Wei Wei ◽  
Qingdong Yan ◽  
Brian K. Weaver ◽  
Houston G. Wood
Keyword(s):  
High Speed ◽  
Torque Converter ◽  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Speed Ratio ◽  
Capacity Loss ◽  
Wide Range ◽  
Stator Blade ◽  
Torque Converters ◽  
Blade Geometry

Cavitation in torque converters may cause degradation in hydrodynamic performance, severe noise, or even blade damage. Researches have highlighted that the stator is most susceptible to the occurrence of cavitation due to the combination of high flow velocities and high incidence angles. The objective of this study is to therefore investigate the effects of cavitation on hydrodynamic performance as well as the influence of stator blade geometry on cavitation. A steady-state homogeneous computational fluid dynamics (CFD) model was developed and validated against test data. It was found that cavitation brought severe capacity constant degradation under low-speed ratio (SR) operating conditions and vanished in high-speed ratio operating conditions. A design of experiments (DOE) study was performed to investigate the influence of stator design variables on cavitation over various operating conditions, and it was found that stator blade geometry had a significant effect on cavitation behavior. The results show that stator blade count and leaning angle are important variables in terms of capacity constant loss, torque ratio (TR) variance, and duration of cavitation. Large leaning angles are recommended due to their ability to increase the cavitation number in torque converters over a wide range of SRs, leading to less stall capacity loss as well as a shorter duration of cavitation. A reduced stator blade count is also suggested due to a reduced TR loss and capacity loss at stall.

scholarly journals Mixing of complex fluids with coaxial mixers composed of two central impellers and an anchor

2021 ◽  
Author(s):  
Argang Kazemzadeh
Keyword(s):  
High Speed ◽  
Complex Fluids ◽  
Operating Conditions ◽  
Newtonian Fluids ◽  
Hydrodynamic Performance ◽  
Mixing Efficiency ◽  
Efficient System ◽  
Wide Range ◽  
Coaxial Mixers ◽  
Pseudoplastic Fluids

The coaxial mixers composed of a high-speed central impeller and a low-speed anchor have been recommended by the previous researchers for the mixing of highly viscous and non-Newtonian fluids. However, no study has been reported in the literature regarding the use of the coaxial mixing systems composed of two central impellers and an anchor in the agitation of complex fluids. Thus, the main objective of this study was to investigate the performance of coaxial mixers composed of two central impellers and an anchor in the agitation of the xanthan gum solution, which is a yield-pseudoplastic fluid, through electrical resistance tomography (ERT), the computational fluid dynamics (CFD), and design of experiments (DOE) combined with the response surface methodology (RSM). In the first stage of this study, the hydrodynamic performance of coaxial mixers, the single and double Scaba impellers in combination with an anchor impeller, was investigated in the mixing of yield-pseudoplastic fluids. Considering the mixing efficiency criteria, it was found that the double Scaba-anchor coaxial system was more efficient than the single Scaba-anchor coaxial mixer in the mixing of yield pseudoplastic fluids with regard to the mixing time and power drawn. In the second stage of this research project, the performances of three different coaxial mixers, namely, double Scaba-anchor coaxial (DSAC), double Rushton turbine-anchor coaxial (DRAC), and double pitched blade turbine-anchor coaxial (DPAC) mixers were assessed. It was found that the double Scaba-anchor coaxial (DSAC) mixer was more efficient system compared to the others at the same operating conditions. To evaluate the influence of the impeller spacing on the hydrodynamics of the double Scaba-anchor coaxial mixer, the lower impeller clearance and the spacing between two central impellers were changed within a wide range. The results demonstrated that a coaxial mixer with the impeller spacing of almost equal to the central impeller diameter was the most efficient configuration compared to the other cases. When the impeller spacing was varied, the merging flow and parallel flow patterns were observed. Finally, the hydrodynamic performances of different configurations of coaxial mixers composed of a wall scraping anchor impeller in combination with two different or identical central high-speed impellers were analyzed. The coaxial mixers utilized in this stage were the Scaba–Scaba-anchor (SSAC), Scaba-Rushton-anchor (SRAC), Rushton-Scaba-anchor (RSAC), Scaba-pitched blade-anchor (SPBAC), and pitched blade-Scaba-anchor (PBSAC). A new correlation was introduced for these complex configurations of the coaxial mixers by incorporating the Metzner-Otto constants (Ks) of the different types of the central impellers into the Reynolds number. The analysis of the collected data revealed that the Scaba-pitched blade-anchor coaxial (SPBAC) mixer was the most efficient mixing system in the mixing of the highly viscous non-Newtonian fluids.

scholarly journals Roughness Effect on Thermo-Elasto-Hydrodynamic Performance of a 170ᵒ -Arc Partial Journal Bearing

2021 ◽  
Vol 27 (1) ◽  
pp. 16-34
Author(s):  
Souad Jabbar Shamal ◽  
Luay Sadiq Al-Ansari ◽  
Ahmed Niameh Mehdy Alhusseny ◽  
Adel Gharib Nasser
Keyword(s):  
Journal Bearing ◽  
Hydrodynamic Pressure ◽  
Iterative Solution ◽  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Temperature Deformation ◽  
Maximum Pressure ◽  
Static Structure ◽  
Scratch Depth ◽  
Wide Range

In the current analysis, the effects of circumferential scratches along the inner surface of a 170ᵒ -arc partial journal bearing has been numerically investigated. Their impact on the thermo-elasto-hydrodynamic performance characteristics, including maximum pressure, temperature, deformation, and stress, has been examined thoroughly. The ANSYS Fluent CFD commercial code was employed to tackle the iterative solution of flow and heat transfer patterns in the fluid film domain. They are then applied to the ANSYS Static Structure solver to compute the deformation and stress resulted in the solid bearing zone. A wide range of operating conditions has been considered, including the eccentricity ratio ( ) and scratch depth ( ). In contrast, the bearing length-diameter ratio (L/D) and the rotation speed (N) have been fixed at 0.77 and 1500 rpm, respectively. The thermo-hydrodynamic pressure, temperature, stress, and deformation have all been computed. It was found that the scratch depth has a direct effect on the thermo-hydrodynamic performance of the partial bearings. Meanwhile, the deep central scratches are important, especially at scratch depth equal to 0.224 mm.

scholarly journals Roughness Effect on Thermo-Elasto-Hydrodynamic Performance of a 170ᵒ -Arc Partial Journal Bearing

2021 ◽  
Vol 27 (1) ◽  
pp. 16-34
Author(s):  
Souad Jabbar Shamal ◽  
Luay Sadiq Al-Ansari ◽  
Ahmed Niameh Mehdy Alhusseny ◽  
Adel Gharib Nasser
Keyword(s):  
Journal Bearing ◽  
Hydrodynamic Pressure ◽  
Iterative Solution ◽  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Temperature Deformation ◽  
Maximum Pressure ◽  
Static Structure ◽  
Scratch Depth ◽  
Wide Range

In the current analysis, the effects of circumferential scratches along the inner surface of a 170ᵒ -arc partial journal bearing has been numerically investigated. Their impact on the thermo-elasto-hydrodynamic performance characteristics, including maximum pressure, temperature, deformation, and stress, has been examined thoroughly. The ANSYS Fluent CFD commercial code was employed to tackle the iterative solution of flow and heat transfer patterns in the fluid film domain. They are then applied to the ANSYS Static Structure solver to compute the deformation and stress resulted in the solid bearing zone. A wide range of operating conditions has been considered, including the eccentricity ratio ( ) and scratch depth ( ). In contrast, the bearing length-diameter ratio (L/D) and the rotation speed (N) have been fixed at 0.77 and 1500 rpm, respectively. The thermo-hydrodynamic pressure, temperature, stress, and deformation have all been computed. It was found that the scratch depth has a direct effect on the thermo-hydrodynamic performance of the partial bearings. Meanwhile, the deep central scratches are important, especially at scratch depth equal to 0.224 mm.

scholarly journals Marine Turbine Hydrodynamics by a Boundary Element Method with Viscous Flow Correction

2018 ◽  
Author(s):  
Francesco Salvatore ◽  
Zohreh Sarichloo ◽  
Danilo Calcagni
Keyword(s):  
Viscous Flow ◽  
Numerical Models ◽  
Turbine Blades ◽  
Integral Equation Method ◽  
Boundary Integral ◽  
Operating Conditions ◽  
Hydrodynamic Performance ◽  
Numerical Predictions ◽  
Wide Range ◽  
Marine Current

A computational methodology for the hydrodynamic analysis of horizontal axis marine current turbines is presented. The approach is based on a boundary integral equation method for inviscid flows originally developed for marine propellers and adapted here to describe the flow features that characterize hydrokinetic turbines. To this purpose, semi-analytical trailing wake and viscous-flow correction models are introduced. A validation study is performed by comparing hydrodynamic performance predictions with two experimental test cases and with results from other numerical models in the literature. The capability of the proposed methodology to correctly describe turbine thrust and power over a wide range of operating conditions is discussed. Viscosity effects associated to blade flow separation and stall are taken into account and predicted thrust and power are comparable with results of blade element methods that are largely used in the design of marine current turbines. The accuracy of numerical predictions tend to reduce in cases where turbine blades operate in off-design conditions.

scholarly journals Mixing of complex fluids with coaxial mixers composed of two central impellers and an anchor

2021 ◽  
Author(s):  
Argang Kazemzadeh
Keyword(s):  
High Speed ◽  
Complex Fluids ◽  
Operating Conditions ◽  
Newtonian Fluids ◽  
Hydrodynamic Performance ◽  
Mixing Efficiency ◽  
Efficient System ◽  
Wide Range ◽  
Coaxial Mixers ◽  
Pseudoplastic Fluids

The coaxial mixers composed of a high-speed central impeller and a low-speed anchor have been recommended by the previous researchers for the mixing of highly viscous and non-Newtonian fluids. However, no study has been reported in the literature regarding the use of the coaxial mixing systems composed of two central impellers and an anchor in the agitation of complex fluids. Thus, the main objective of this study was to investigate the performance of coaxial mixers composed of two central impellers and an anchor in the agitation of the xanthan gum solution, which is a yield-pseudoplastic fluid, through electrical resistance tomography (ERT), the computational fluid dynamics (CFD), and design of experiments (DOE) combined with the response surface methodology (RSM). In the first stage of this study, the hydrodynamic performance of coaxial mixers, the single and double Scaba impellers in combination with an anchor impeller, was investigated in the mixing of yield-pseudoplastic fluids. Considering the mixing efficiency criteria, it was found that the double Scaba-anchor coaxial system was more efficient than the single Scaba-anchor coaxial mixer in the mixing of yield pseudoplastic fluids with regard to the mixing time and power drawn. In the second stage of this research project, the performances of three different coaxial mixers, namely, double Scaba-anchor coaxial (DSAC), double Rushton turbine-anchor coaxial (DRAC), and double pitched blade turbine-anchor coaxial (DPAC) mixers were assessed. It was found that the double Scaba-anchor coaxial (DSAC) mixer was more efficient system compared to the others at the same operating conditions. To evaluate the influence of the impeller spacing on the hydrodynamics of the double Scaba-anchor coaxial mixer, the lower impeller clearance and the spacing between two central impellers were changed within a wide range. The results demonstrated that a coaxial mixer with the impeller spacing of almost equal to the central impeller diameter was the most efficient configuration compared to the other cases. When the impeller spacing was varied, the merging flow and parallel flow patterns were observed. Finally, the hydrodynamic performances of different configurations of coaxial mixers composed of a wall scraping anchor impeller in combination with two different or identical central high-speed impellers were analyzed. The coaxial mixers utilized in this stage were the Scaba–Scaba-anchor (SSAC), Scaba-Rushton-anchor (SRAC), Rushton-Scaba-anchor (RSAC), Scaba-pitched blade-anchor (SPBAC), and pitched blade-Scaba-anchor (PBSAC). A new correlation was introduced for these complex configurations of the coaxial mixers by incorporating the Metzner-Otto constants (Ks) of the different types of the central impellers into the Reynolds number. The analysis of the collected data revealed that the Scaba-pitched blade-anchor coaxial (SPBAC) mixer was the most efficient mixing system in the mixing of the highly viscous non-Newtonian fluids.

Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs

1972 ◽  
Vol 30 ◽  
pp. 596-597
Author(s):  
David A. Ansley
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Spatial Filter ◽  
Operating Conditions ◽  
Objective Lens ◽  
List Type ◽  
Spatial Filters ◽  
Transmission Electron ◽  
Wide Range

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:(1) Specimen amplitude, phase, and separation(2) Illumination wavelength, half-angle, and tilt(3) Objective lens focal length and aperture width(4) Spherical aberration, defocus, and chromatic aberration focus shift(5) Detector gamma, additive, and multiplicative noise constants(6) Type of spatial filter: linear cosine, linear sine, or deterministic

Structure and properties of compact articles from high-alloyed iron powder with adding of boron nitride

2020 ◽  
pp. 39-48
Author(s):  
B. O. Bolshakov ◽  
◽  
R. F. Galiakbarov ◽  
A. M. Smyslov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Grain Boundary ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Operating Conditions ◽  
Structure And Properties ◽  
Steam Turbines ◽  
Friction Forces ◽  
Wide Range

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

COPPER ALLOY No. 268

Alloy Digest ◽  
1976 ◽  
Vol 25 (2) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Copper Alloy ◽  
Cold Working ◽  
Heat Treating ◽  
Zinc Alloy ◽  
Good Resistance ◽  
Wide Range ◽  
Copper Zinc ◽  
The Common ◽  
Cold Worked

Abstract Copper Alloy No. 268 is a copper-zinc alloy with excellent cold-working properties and good resistance to corrosion. It can be cold worked by all the common fabrication processes and has a wide range of applications. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear strength as well as fatigue. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Cu-306. Producer or source: Brass mills.

Nitrogen Removal from Anaerobically-Treated Leachate

1984 ◽  
Vol 19 (1) ◽  
pp. 87-100
Author(s):  
D. Prasad ◽  
J.G. Henry ◽  
P. Elefsiniotis
Keyword(s):  
Nitrogen Removal ◽  
Air Flow ◽  
Operating Conditions ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Anaerobic Filter ◽  
Ph Values ◽  
Wide Range ◽  
Ammonia Desorption ◽  
Effects Of Ph

Abstract Laboratory studies were conducted to demonstrate the effectiveness of diffused aeration for the removal of ammonia from the effluent of an anaerobic filter treating leachate. The effects of pH, temperature and air flow on the process were studied. The coefficient of desorption of ammonia, KD for the anaerobic filter effluent (TKN 75 mg/L with NH3-N 88%) was determined at pH values of 9, 10 and 11, temperatures of 10, 15, 20, 30 and 35°C, and air flow rates of 50, 120, and 190 cm3/sec/L. Results indicated that nitrogen removal from the effluent of anaerobic filters by ammonia desorption was feasible. Removals exceeding 90% were obtained with 8 hours aeration at pH of 10, a temperature of 20°C, and an air flow rate of 190 cm3/sec/L. Ammonia desorption coefficients, KD, determined at other temperatures and air flow rates can be used to predict ammonia removals under a wide range of operating conditions.

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