Electric performance of fastened hybrid busbars: An experimental and numerical study

2021 ◽  
pp. 146442072110430
Author(s):  
Rui FV Sampaio ◽  
João PM Pragana ◽  
Ivo MF Bragança ◽  
Carlos MA Silva ◽  
Chris V Nielsen ◽  
...  
Keyword(s):  
Cross Sections ◽  
Current Flow ◽  
Numerical Study ◽  
Surface Condition ◽  
Design Guidelines ◽  
Electric Resistance ◽  
Tightening Torque ◽  
Unit Cells ◽  
Aluminium Sheets ◽  
Steel Bolts

This paper is focused on fastened hybrid busbars made from copper and aluminium with the purpose of analysing the influence of the steel bolts, of their tightening torque and of the surface condition of the sheets on the electric current flow and electric resistance of the joints. The methodology combines experimentation with unit cells that are representative of the joints and electro-mechanical numerical simulation using a finite element computer program developed by the authors. Results are a step forward in understanding the combined influence of bolts, contact pressure and surface roughness on the electric performance of fastened hybrid busbars. Design guidelines for dimensioning the cross sections of the copper and aluminium sheets and for effectively distributing bolts across the contacting surfaces are also provided.

Orientational randomness and its influence on the barrier properties of flake-filled composite films

2016 ◽  
Vol 33 (4) ◽  
pp. 438-456 ◽  
Author(s):  
TD Papathanasiou ◽  
A Tsiantis
Keyword(s):  
Cross Sections ◽  
Volume Fraction ◽  
Numerical Study ◽  
Composite Films ◽  
Effective Diffusivity ◽  
Barrier Properties ◽  
Power Exponent ◽  
Random System ◽  
Improvement Factor ◽  
Unit Cells

This direct numerical study investigated the effect of orientational randomness on the barrier properties of flake-filled composites. Over 2500 simulations have been conducted in two-dimensional, doubly periodic unit cells, each containing 500 individual flake cross-sections which, besides being spatially random, assume random orientations within an interval [−ɛ, +ɛ] ([Formula: see text]). We consider long flake systems (aspect ratio α = 50, 100, and 1000) from the dilute (αϕ = 0.01) to the concentrated (αϕ = 15) regime, where (ϕ) is the flake volume fraction. At each (ɛ) and (αϕ), several realizations are generated. At each of those, the steady-state diffusion equation is solved, the mass flux across a boundary normal to the diffusion direction is computed and an effective diffusivity Deff calculated from Fick’s Law. The computational results for Deff are analyzed and the effects of (ɛ) and (αϕ) are quantified. These differ in the dilute (αϕ < 1) and in the concentrated regimes (1 < αϕ < 15). In the dilute regime, the barrier improvement factor is a linear function of (ɛ) and a power function of (αϕ), with the exponent (∼1.07) independent of orientation. In concentrated systems, we find that for aligned flakes or flakes showing small deviations from perfect alignment, the barrier improvement factor approaches the quadratic dependence on (αϕ) predicted by theory. However, the power exponent is found to decrease as (ɛ) increases, from 1.71 in the aligned system (ɛ = 0) to ∼0.9 in the fully random system (ɛ = π/2). We propose a scaling which incorporates the effects of both (αϕ) and (ɛ) on the barrier improvement factor, resulting in a master curve for all (αϕ) and (ɛ). Our results suggest that the anticipated barrier property improvement may not be realized if the flake orientations exhibit a significant scatter around the desired direction.

scholarly journals PARAMETRIC STUDY ON THE LATERAL TORSIONAL BUCKLING OF STAINLESS STEEL I BEAMS WITH CLASS 4 CROSS-SECTIONS IN CASE OF FIRE

2016 ◽  
Author(s):  
Nuno Lopes ◽  
Pedro Gamelas ◽  
Paulo Vila Real
Keyword(s):  
Stainless Steel ◽  
Cross Sections ◽  
Elevated Temperatures ◽  
Numerical Study ◽  
Design Guidelines ◽  
Steel Grade ◽  
Steel Beams ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Steel Members

For predicting the behaviour of beams with thin-walled I sections, named Class 4 in Eurocode 3 (EC3), it is necessary to account for the occurrence of both local and lateral torsional buckling (LTB). These instability phenomena, which are intensified at elevated temperatures, should be accurately considered in design rules. The fire design guidelines for stainless steel members, given in Part 1-2 of EC3, propose the use of the same formulae developed for carbon steel (CS) elements. However, these two materials have different constitutive laws, leading to believe that the use of those formulae should be validated. This work presents a parametric numerical study on the behaviour of stainless steel beams with Class 4 I sections at elevated temperatures. The influences of several parameters such as stainless steel grade, loading type and cross section slenderness are evaluated, and comparisons between the obtained numerical results and EC3 rules are presented.

scholarly journals Aluminium alloy cross-sections under uniaxial bending and compression: A numerical study

2021 ◽  
Vol 1058 (1) ◽  
pp. 012011
Author(s):  
Evangelia Georgantzia ◽  
Michaela Gkantou ◽  
George S. Kamaris ◽  
Kunal Kansara ◽  
Khalid Hashim
Keyword(s):  
Aluminium Alloy ◽  
Cross Sections ◽  
Numerical Study

Influence of Surface Condition on Oxides Layer Morphology on NiCrAlY Coating during Oxidation at Temperature 1000°C and 1100°C

2015 ◽  
Vol 227 ◽  
pp. 385-388 ◽  
Author(s):  
Grzegorz Moskal ◽  
Dawid Niemiec
Keyword(s):  
Cross Sections ◽  
Surface Characterization ◽  
Surface Condition ◽  
Point Of View ◽  
Inconel 625 ◽  
Oxidation Test ◽  
Nicraly Coating ◽  
Static Oxidation ◽  
Plasma Spraying Process

Characterization of top-surface of NiCrAlY coating deposited by plasma spraying process on Inconel 625 Ni based superalloys was analyzed in two different completely conditions. First of them was as sprayed state of NiCrAlY coating and the second one was condition after grinding process. The basic aim of this treatment was related to obtain totally different conditions of coatings surface especially from roughness point of view. Those two types of top surface morphology was a base to comparison of oxidation resistant during static oxidation test at temperature of 1000°C and 1100°C. The temperature of static oxidation test was 1000°C and 1100°C. The specimens were moved out from furnace after 25, 300, 500, 750 and 1000 hours of exposition in laboratory air. The range of investigations after each interval included top surface characterization of specimens by SEM, XRD and EDS method. Those investigations showed that different types of top surface conditions had a fundamental influence on oxides layer morphology. Especially in the case of phase`s constituent of oxides zone. More detailed investigations were made on the cross sections of two types of investigated specimens. Analysis of oxides layer morphology showed in this case basic differences in thickness of oxides zone which was much higher in the case of as sprayed NiCrAlY coating.

scholarly journals Numerical and Experimental Study of Cross-Sectional Effects on the Mixing Performance of the Spiral Microfluidics

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1470
Author(s):  
Omid Rouhi ◽  
Sajad Razavi Bazaz ◽  
Hamid Niazmand ◽  
Fateme Mirakhorli ◽  
Sima Mas-hafi ◽  
...  
Keyword(s):  
Cross Sections ◽  
Numerical Study ◽  
Large Angle ◽  
Element Model ◽  
Channel Length ◽  
Cross Sectional ◽  
Flow Rates ◽  
Lab On Chip ◽  
Mixing Performance ◽  
Dean Flow

Mixing at the microscale is of great importance for various applications ranging from biological and chemical synthesis to drug delivery. Among the numerous types of micromixers that have been developed, planar passive spiral micromixers have gained considerable interest due to their ease of fabrication and integration into complex miniaturized systems. However, less attention has been paid to non-planar spiral micromixers with various cross-sections and the effects of these cross-sections on the total performance of the micromixer. Here, mixing performance in a spiral micromixer with different channel cross-sections is evaluated experimentally and numerically in the Re range of 0.001 to 50. The accuracy of the 3D-finite element model was first verified at different flow rates by tracking the mixing index across the loops, which were directly proportional to the spiral radius and were hence also proportional to the Dean flow. It is shown that higher flow rates induce stronger vortices compared to lower flow rates; thus, fewer loops are required for efficient mixing. The numerical study revealed that a large-angle outward trapezoidal cross-section provides the highest mixing performance, reaching efficiencies of up to 95%. Moreover, the velocity/vorticity along the channel length was analyzed and discussed to evaluate channel mixing performance. A relatively low pressure drop (<130 kPa) makes these passive spiral micromixers ideal candidates for various lab-on-chip applications.

scholarly journals Developing the Flow Path For the K-1250-6.9/25 Turbine Unit Using the Optimal Design Methods

2021 ◽  
pp. 15-18
Author(s):  
Ihor Palkov ◽  
Sergii Palkov ◽  
Oleh Ishchenko ◽  
Olena Avdieieva
Keyword(s):  
Numerical Experiment ◽  
Cross Sections ◽  
Turbine Unit ◽  
Current Flow ◽  
Three Dimensional ◽  
Flow Path ◽  
Three Dimensional Model ◽  
Flow Paths ◽  
Intermediate Pressure ◽  
Blade System

The paper considers the main principles that are used to develop the flow paths (FP) of the high-pressure cylinders (HPC), intermediate-pressure cylinders (IPC), and low-pressure cylinders (LPC) for the K-1250-6.9/25 turbine unit. It describes approaches to the numerical experiment when designing flow paths, the advantage of which is lower labor, time and financial costs and higher informativeness compared to the physical experiment on flow paths. When designing the flow paths of high- and intermediate-pressure cylinders (HIPC), the numerical experiment is performed using the three-dimensional viscous-flow method. For this purpose, a three-dimensional model of the blade system in the flow path is built, which consists of a large number of finite volumes (elements) in the shape of hexagons, in each of which the integration of the equations of gas dynamics is performed. When developing LPC, the method of parameterization and analytical profiling of the blade crown sections is used, where the profiles are described by the curves of the fourth and fifth orders with the condition of providing the minimum value of the maximum curvature and monotonicity of variation of the three-dimensional blade geometry along height. This method allows obtaining the optimal profiles of the cross sections of the blades, which correspond to the current flow lines to the fullest extent, and minimizing the profile energy losses when the flow flows around the blades.

A Numerical Study of Single Phase Dielectric Fluid Immersion Cooling of Multichip Modules

2012 ◽  
Vol 2012 (1) ◽  
pp. 000581-000590
Author(s):  
Roy W. Knight ◽  
Seth Fincher ◽  
Sushil H. Bhavnani ◽  
Daniel K. Harris ◽  
R. Wayne Johnson
Keyword(s):  
Single Phase ◽  
Printed Circuit Board ◽  
Numerical Study ◽  
Design Guidelines ◽  
Circuit Board ◽  
Dielectric Fluid ◽  
Multichip Modules ◽  
Ansys Fluent ◽  
Immersion Cooling ◽  
Numerical Parametric Study

Immersion, single phase free convection cooling of multichip modules on a printed circuit board in a pool of dielectric fluid was examined numerically, with experimental verification of baseline cases. A multi-chip module with multiple thermal test cells with temperature sensing capability was simulated. The commercially available computational fluid dynamics program from ANSYS, Fluent, was used with the electronics packaging front end, Icepak, employed to create the models and compact conduction modules. Simulations were first performed of an experimental test vehicle which had five 18 mm by 18 mm die, arranged in a cross pattern, equally spaced die, 25 mm between them. Two of the die were aligned vertically with the center die, two aligned horizontally with it. The board was suspended vertically in a large pool of dielectric fluid. Heat was dissipated in the die at a flux of up to 2 W/cm2, based on the die surface area. Simulation results were compared with experimentally measured die temperature values and excellent agreement was seen for the cases of one die heated and all five die uniformly heated with the board cooled by FC-72. A numerical parametric study was performed to examine the effect of die size and spacing on temperature rise. In addition to FC-72, immersion cooling in Novec 649 and HFE 7100 were modeled. Design guidelines are suggested for dielectric fluid immersion cooled multichip modules.

Experimental study on the flexural behavior of steel tube slab composite beams and key parameters optimization

2019 ◽  
Vol 22 (11) ◽  
pp. 2476-2489 ◽  
Author(s):  
Pengjiao Jia ◽  
Wen Zhao ◽  
Yongping Guan ◽  
Jiachao Dong ◽  
Qinghe Wang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Bearing Capacity ◽  
Composite Beams ◽  
Steel Tube ◽  
Design Guidelines ◽  
Reinforcement Ratio ◽  
Flexural Behavior ◽  
Flexural Capacity ◽  
Design Elements ◽  
Steel Bolts

This work presents an experimental study on the flexural behavior of steel tube slab composite beams subjected to pure bending. The main design elements considered in the work are the flange thickness, reinforcement ratio of high strength bolts, spacing between the tubes, and transverse patterns of the tube connections. Based on nine flexural experiments on simply supported steel tube slab specimens, the failure process and crack development in steel tube slab specimens, and their load–deflection curves are investigated. The results of the laboratory tests show that the welding of the bottom flange significantly improves the flexural capacity of the steel tube slab structure. In addition, a lower concrete’s compressive strength improves the ductility of the steel tube slab specimens. Moreover, the flexural capacities predicted from the design guidelines are in good agreement with the experimental test results. Finally, based on the numerical simulations using the ABAQUS software, a numerical model is established to further investigate the effect of the additional parameters on the flexural capacity of steel tube slab structures. The numerical results suggested that the diameter of the steel bolts and the reinforcement ratio have a limited effect on the flexural bearing capacity of the steel tube slab beams, and the ultimate bearing capacity increases linearly along with increase in the diameter of the steel bolts and the reinforcement ratio in a certain range.

Parametric Experimental and Numerical Study of LP Diffuser and Exhaust Hoods

2016 ◽  
Author(s):  
Derek Taylor ◽  
Gurnam Singh ◽  
Phil Hemsley ◽  
Martin Claridge
Keyword(s):  
Numerical Study ◽  
Design Guidelines ◽  
Geometric Parameters ◽  
Design Tools ◽  
Steam Turbines ◽  
Exhaust Hood ◽  
Geometric Configurations ◽  
Last Stage ◽  
Lp Turbine ◽  
The Impact

The design of an effective diffuser for a given last stage blade of an LP turbine is known to be highly dependent on the size and shape of the exhaust hood in which it is located. For retrofit steam turbines in particular, where a new last stage blade and diffuser are fitted into an existing exhaust hood, the shapes and sizes of the exhaust box have been seen to vary significantly from one contract to the next. An experimental parametric study of diffuser lips and exhaust hood configurations has been run on a model test turbine rig at GE Power to investigate the impact of various geometric parameters on the performance of the diffusers. Improved testing and post-processing methodologies means the diffuser performance has been obtained for a greater number of geometric configurations than was previously typically possible. The results of these experiments are compared with numerical calculations and confirm the accuracy of the standard in-house diffuser design tools. Key geometric parameters are identified from the test data and used to generate improved diffuser design guidelines.

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