scholarly journals Numerical Study on the Influence of Mass and Stiffness Ratios on the Vortex Induced Motion of an Elastically Mounted Cylinder for Harnessing Power

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2580 ◽  
Author(s):  
Vidya Chandran ◽  
Sekar M. ◽  
Sheeja Janardhanan ◽  
Varun Menon
Keyword(s):  
Numerical Study ◽  
Cross Flow ◽  
Maximum Amplitude ◽  
Field Tests ◽  
Operating Conditions ◽  
Irrigation Canal ◽  
Bluff Bodies ◽  
Low Velocity ◽  
Useful Power ◽  
The Face

Harnessing the power of vortices shed in the wake of bluff bodies is indeed a boon to society in the face of fuel crisis. This fact serves as an impetus to develop a device called a hydro vortex power generator (HVPG), comprised of an elastically mounted cylinder that is free to oscillate in the cross-flow (CF) direction even in a low velocity flow field. The oscillatory motions in turn can be converted to useful power. This paper addresses the influence of system characteristics viz. stiffness ratio (k*) and mass ratio (m*) on the maximum response amplitude of the elastically mounted cylinder. Computational fluid dynamics (CFD) simulations have been used here to solve a two way fluid–structure interaction (FSI) problem for predicting the trend of variation of the non-dimensional amplitude Y/D with reduced velocity Ur through a series of simulations. Maximum amplitude motions have been attributed to the lowest value of m* with Ur = 8. However, the maximum lift forces correspond to Ur = 4, providing strong design inputs as well as indicating the best operating conditions. The numerical results have been compared with those of field tests in an irrigation canal and have shown reasonable agreement.

A Numerical Study of Inlet Geometry for a Low Inertia Mixed Flow Turbocharger Turbine

2014 ◽  
Author(s):  
Thomas M. Leonard ◽  
Stephen Spence ◽  
Juliana Early ◽  
Dietmar Filsinger
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Velocity Ratio ◽  
Cone Angle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Transient Performance ◽  
Blade Angle ◽  
Low Velocity ◽  
Mixed Flow

Mixed flow turbines can offer improvements over typical radial turbines used in automotive turbochargers, with regards to transient performance and low velocity ratio efficiency. Turbine rotor mass dominates the rotating inertia of the turbocharger, and any reductions of mass in the outer radii of the wheel, including the rotor back-disk, can significantly reduce this inertia and improve the acceleration of the assembly. Off-design, low velocity ratio conditions are typified by highly tangential flow at the rotor inlet and a non-zero inlet blade angle is preferred for such operating conditions. This is achievable in a Mixed Flow Turbine without increasing bending stresses within the rotor blade, which is beneficial in high speed and high inlet temperature turbine design. A range of mixed flow turbine rotors was designed with varying cone angle and inlet blade angle and each was assessed at a number of operating points. These rotors were based on an existing radial flow turbine, and both the hub and shroud contours and exducer geometry were maintained. The inertia of each rotor was also considered. The results indicated that there was a trade-off between efficiency and inertia for the rotors and certain designs may be beneficial for the transient performance of downsized, turbocharged engines.

Experimental Study of Non-Premixed Flames of Liquefied Petroleum Gas and Air in Cross-Flow and the Effects of Fuel Properties on Flame Stability

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
S. Muthu Kumaran ◽  
Vasudevan Raghavan
Keyword(s):  
Premixed Flames ◽  
Cross Flow ◽  
Operating Conditions ◽  
Fuel Properties ◽  
Jet Flows ◽  
Flame Stability ◽  
Bluff Bodies ◽  
Liquefied Petroleum Gas ◽  
Air Jet ◽  
The Stability

Abstract Stability of flames are affected by fuel properties, geometry of the burner and operating conditions. In this experimental work, first the characteristics of non-premixed flames of Liquefied Petroleum Gas (LPG) and air in cross-flow configuration, where air jet flows perpendicular to the fuel stream, are studied experimentally. Flame transition and stability regimes of non-premixed flames of LPG and air, in a cross-flow burner without and with obstacles, are determined by systematically varying the fuel and air flow rates. Obstacles such as backward facing step and cylindrical bluff bodies are considered. Subsequently, the effects of fuel properties on the stability of flames are analyzed, Flame stability regimes of natural gas (methane) and biogas (methane and carbon-dioxide), measured from a similar burner are available in literature. These have been compared with the stability of LPG flames in terms of power rating of the burner and global equivalence ratio (defined for non-premixed flames).

Numerical Study on the Interaction of In-Line and Cross-Flow VIV

2009 ◽  
Author(s):  
Shizhen Tang ◽  
Weiping Huang
Keyword(s):  
Fatigue Damage ◽  
Current Velocity ◽  
High Frequency ◽  
Amplitude Ratio ◽  
Numerical Study ◽  
Cross Flow ◽  
Statistical Methodology ◽  
Low Velocity ◽  
Ratio Curve ◽  
The Mean

The fatigue damage induced by in-line vibration and cross-flow vibration was addressed in this paper using a statistical methodology and also the amplitude ratio. Traditionally, engineers have concentrated on cross-flow vibrations, assuming that in-line oscillations are less important. In-line amplitudes are generally lower, but the high-frequency nature of these oscillations can result in significant fatigue damage. The ratio between amplitude of in-line oscillation and cross-flow vibration in four different current velocity was studied, and also be analyzed by statistical method. For the fatigue analysis, the ratio between damage of in-line and cross-flow was obtained, the maximum ratio curve and the mean ratio curve were presented. The conclusions presented the fatigue damage caused by in-line vibration couldn’t be neglected, especially in low velocity.

Numerical Investigation of Thermal-Hydraulic Performance of Circular and Non-Circular Tubesin Cross-Flow

2021 ◽  
pp. 102-117
Author(s):  
R. Deeb ◽  
D.V. Sidenkov ◽  
V.I. Salokhin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Circular Tube ◽  
Numerical Study ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Ansys Fluent

A numerical study has been conducted to clarify flow and heat transfer characteristics around circular, cam, and drop-shaped tubes using the software package ANSYS FLUENT. Reynolds number Re based on equivalent circular tube is varied in range of (8.1--19.2)·103. All tube shapes are investigated under similar operating conditions. Local heat transfer, pressure and friction coefficients over a surface of the tubes were presented. Obtained results agree well with those available in the literature. Correlations of the average Nusselt number Nuav and a friction factor f in terms of Reynolds number for the studied tubes were proposed. The results indicated that Nuav increases with increasing Re. In the contrary, f decreases as Re increases. Thermal-hydraulic performance is used to estimate the efficiency of the cam and drop-shaped tubes. Results show that the drop-shaped tube has the best thermal-hydraulic performance, which is about 1.6 and 2.5 times higher than that of the cam-shaped and circular tube, respectively

scholarly journals Computational analysis of a cross flow turbine performance

2018 ◽  
Vol 240 ◽  
pp. 03011
Author(s):  
Vanessa Ruiz Gómez ◽  
Edison A. Palacio Higuita ◽  
Aldo Germán Benavides Morán
Keyword(s):  
Energy Demand ◽  
Numerical Study ◽  
Cross Flow ◽  
Experimental Tests ◽  
Electrical Energy ◽  
Operating Conditions ◽  
Ansys Fluent ◽  
Turbine Performance ◽  
Study Results ◽  
Guide Blade

In the electrical energy generation context in Colombia, the water resources represent the 64% of the potential generated according to UPME in the 2015 year; becoming into a solution to the growing energy demand and to the supply of energy in non-interconnected zones. The cross-flow turbines as Michell-Banki type, become an efficient and economically attractive choice. This paper shows the fluiddynamic performance of a laboratory’s model turbine under several operating conditions. The development of this analysis is supported by the results of experimental tests, uses the computational fluid dynamics as a tool for modelling, estimate, and analyse the turbine behaviour under different operating conditions, with ANSYS-Fluent software; the computational model considers the most important geometric aspects of the turbine and the opening percentage effect of the guide blade. The water flow through the rotor is approach through a turbulence model as κ – ε type. The numerical study results agree satisfactorily with the turbine performance observed in the laboratory.

Cake Formation in Cross-Flow Microfiltration Systems

1992 ◽  
Vol 25 (10) ◽  
pp. 149-162 ◽  
Author(s):  
V. L. Pillay ◽  
C. A. Buckley
Keyword(s):  
Cross Flow ◽  
Operating Conditions ◽  
Waste Waters ◽  
Domestic Waste ◽  
Time Curve ◽  
Good Correspondence ◽  
Operating Variables ◽  
Start Up ◽  
Turbulent Flow Regime ◽  
Cake Formation

Cross-flow microfiltration (CFMF) has potentially wide application in the processing of industrial and domestic waste waters. Optimum design and operation of CFMF systems necessitates a knowledge of the characteristic system behaviour, and an understanding of the mechanisms governing this behaviour. This paper is a contribution towards the elucidation and understanding of the behaviour of a woven fibre CFMF operated in the turbulent flow regime. The characteristic flux-time curve and effects of operating variables on flux are presented for a limestone suspension cross-flow filtered in a 25 mm woven fibre tube. The phenomena contributing to the shape of the flux-time curve are discussed. A model of the mechanisms governing cake growth and limit is presented. Predicted steady-state fluxes show a notably good correspondence with experimentally measured values. It is also found that the flux may not be uniquely defined by the operating conditions, but may also be a function of the operating path taken to reach the operating point. This is of significance in the start-up and operation of CFMF units.

scholarly journals Designs of InGaN Micro-LED Structure for Improving Quantum Efficiency at Low Current Density

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Shiqiang Lu ◽  
Jinchai Li ◽  
Kai Huang ◽  
Guozhen Liu ◽  
Yinghui Zhou ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Current Density ◽  
Carrier Transport ◽  
Defect Density ◽  
Numerical Study ◽  
Structure Design ◽  
Operating Conditions ◽  
Hole Injection ◽  
Electron Blocking Layer ◽  
Recombination Processes

AbstractHere we report a comprehensive numerical study for the operating behavior and physical mechanism of nitride micro-light-emitting-diode (micro-LED) at low current density. Analysis for the polarization effect shows that micro-LED suffers a severer quantum-confined Stark effect at low current density, which poses challenges for improving efficiency and realizing stable full-color emission. Carrier transport and matching are analyzed to determine the best operating conditions and optimize the structure design of micro-LED at low current density. It is shown that less quantum well number in the active region enhances carrier matching and radiative recombination rate, leading to higher quantum efficiency and output power. Effectiveness of the electron blocking layer (EBL) for micro-LED is discussed. By removing the EBL, the electron confinement and hole injection are found to be improved simultaneously, hence the emission of micro-LED is enhanced significantly at low current density. The recombination processes regarding Auger and Shockley–Read–Hall are investigated, and the sensitivity to defect is highlighted for micro-LED at low current density.Synopsis: The polarization-induced QCSE, the carrier transport and matching, and recombination processes of InGaN micro-LEDs operating at low current density are numerically investigated. Based on the understanding of these device behaviors and mechanisms, specifically designed epitaxial structures including two QWs, highly doped or without EBL and p-GaN with high hole concentration for the efficient micro-LED emissive display are proposed. The sensitivity to defect density is also highlighted for micro-LED.

scholarly journals Data-driven Modelling of Microfiltration Process with Embedded Static Mixer for Steepwater from Corn Starch Industry

2017 ◽  
Author(s):  
Laslo Šereš ◽  
Ljubica Dokić ◽  
Bojana Ikonić ◽  
Dragana Šoronja-Simović ◽  
Miljana Djordjević ◽  
...  
Keyword(s):  
Corn Starch ◽  
Desirability Function ◽  
Specific Energy Consumption ◽  
Cross Flow ◽  
Operating Conditions ◽  
Transmembrane Pressure ◽  
Static Mixer ◽  
Permeate Flux ◽  
Experimental Conditions ◽  
Starch Industry

Cross-flow microfiltration using ceramic tubular membrane was applied for treatment of steepwater from corn starch industry. Experiments are conducted according to the faced centered central composite design at three different transmembrane pressures (1, 2 and 3 bar) and cross-flow velocities (100, 150 and 200 L/h) with and without the usage of Kenics static mixer. For examination of the influence of the selected operating conditions at which usage of the static mixer is justified, a response surface methodology and desirability function approach were used. Obtained results showed improvement in the average permeate flux by using Kenics static mixer for 211 % to 269 % depending on experimental conditions when compared to the system without the static mixer. As a result of optimization, the best results considering flux improvement as well as reduction of specific energy consumption were obtained at low transmembrane pressure and lower feed cross-flow rates.

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