scholarly journals Comparison of Two Single Stage Low-Pressure Rotary Lobe Expander Geometries in Terms of Operation

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4512
Author(s):  
Michalina Kurkus-Gruszecka ◽  
Piotr Krawczyk
Keyword(s):  
Cfd Simulation ◽  
Mechanical Energy ◽  
Electric Energy ◽  
Low Pressure ◽  
Single Stage ◽  
Small Scale ◽  
Operational Parameters ◽  
Data Simulation ◽  
Time Step ◽  
Geometry Model

In the article the computational fluid dynamics (CFD) simulation and calculated operational parameters of the single stage low-pressure rotary lobe expander compared with the values obtained from a different geometry simulation are presented. Low-pressure rotary lobe expanders are rotary engines that use a compressed gas to produce mechanical energy, which in turn can be converted into another form, i.e., electric energy. Currently, expanders are used in narrow areas, but have a large potential in the energy production from gases of low thermodynamic parameters. The first geometry model was designed on the basis of an industrial device and validated with the empirical data. Simulation of the second geometry was made based on a validated model in order to estimate the operational parameters of the device. The CFD model included the transient simulation of compressible fluid in the geometry changing over time and the rotors motion around two rotation axes. The numerical model was implemented in ANSYS CFX software. After obtaining simulation results in the form of parameters monitors for each time step, a number of calculations were performed using a written code analysing the CFD program output files. The article presents the calculation results and the geometries comparison in terms of work efficiency. The research indicated that the construction of the device on a small scale could cause a significant decrease in the aforementioned parameter, caused by medium leaks in the expander clearances.

scholarly journals Computational fluid dynamic analysis and validation of the single stage low pressure rotary lobe compressed air expander

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1133-1142 ◽  
Author(s):  
Piotr Krawczyk ◽  
Michalina Kurkus-Gruszecka ◽  
Aleksandra Mikolajczak ◽  
Piotr Lapka ◽  
Krzysztof Badyda
Keyword(s):  
Fluid Dynamic ◽  
Mechanical Energy ◽  
Low Pressure ◽  
Industrial Processes ◽  
Operating Pressure ◽  
Operational Parameters ◽  
Computational Fluid Dynamic Analysis ◽  
Compressed Gas ◽  
Model Geometry ◽  
The Mathematical Model

Technologies using media with relatively low thermodynamic parameters are now being developed more and more widely. These technologies may be used in industrial processes in which waste media such as low pressure air or other gases are available. One of the technologies enabling the use of such gases is rotary lobe expander. Rotary lobe expanders are compressed gas-powered devices which produce electricity or mechanical energy. In terms of the nature of operation, these devices are similar to turbines, but have higher efficiency at lower operating pressure. Currently, they are applied in mines as engines or as drives for elevators. The paper covers the CFD model of the expander and its validation using the literature data on the industrial device. The mathematical model, geometry, the choice of the computational grid and the adopted boundary conditions were presented. Several simulations were carried out for the variable operational parameters of the device and an attempt was made to assess the correctness of the assumptions and developed model. Finally, the results with discussion are presented both in tabular and graphical forms.

Transient CFD Co-Simulation of a 3D Compressor Model in its 1D System Environment

2019 ◽  
Author(s):  
Andreas Spille-Kohoff ◽  
Farai Hetze ◽  
Bennie Du Toit
Keyword(s):  
Distribution System ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Low Pressure ◽  
System Response ◽  
Pressure Side ◽  
Time Step ◽  
The Impact ◽  
Transient Coupling

Abstract Rotary compressors such as screw compressors, roots blowers, and turbo compressors are used in industry to compress process gases, or as vacuum or backing pumps to evacuate vessels. Gas is sucked in at low-pressure side, transported and compressed by size-changing chambers (PD machines) or energy transmission from rotor to fluid (turbo machinery), and released at high-pressure side. In expanders or turbines, flow direction is from high to low pressure side to gain energy from pressurized gases. The 3D CFD simulation of such compressors/expanders is complex and time-consuming due to its transient nature and fine meshes to ensure a proper representation of radial and axial gaps in the range of some microns with machine dimensions up to meters. Due to this complexity, 3D CFD simulation should focus on the component, i.e. the compressor, and the attached overall system with vessels, valves, pipes, and consumers should be simulated in a 1D network or system simulation. Due to oscillations in the gas flow and interaction with the connected system a transient coupling is necessary. In this paper we show a 3D CFD simulation of a screw compressor using ANSYS CFX in a co-simulation with the 1D Flownex simulation environment of a network modelling the pressurized gas distribution. Whereas the 3D solver works on meshes with up to several million nodes in parallel on HPC systems, the 1D solver typically works serially on several thousand nodes that discretize the flow direction. The transient coupling is based on the exchange of variables at the boundaries of each simulation for every time step allowing for detailed analysis. The impact of the acoustic propagation of pressure fluctuations and the pulsating fluid flow provided by the compressor on the distribution system, and in return the effects of the system response on the compressor are evaluated. Furthermore transient scenarios such as start-up procedures or component failure will be shown.

scholarly journals Hybrid Triboelectric-Electromagnetic Nanogenerators for Mechanical Energy Harvesting: A Review

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
João V. Vidal ◽  
Vladislav Slabov ◽  
Andrei L. Kholkin ◽  
Marco P. Soares dos Santos
Keyword(s):  
Energy Harvesting ◽  
System Integration ◽  
Vibrational Energy ◽  
Mechanical Energy ◽  
Short Circuit ◽  
Electric Energy ◽  
Open Circuit ◽  
Future Research ◽  
Small Scale ◽  
Transduction Mechanisms

AbstractMotion-driven electromagnetic-triboelectric energy generators (E-TENGs) hold a great potential to provide higher voltages, higher currents and wider operating bandwidths than both electromagnetic and triboelectric generators standing alone. Therefore, they are promising solutions to autonomously supply a broad range of highly sophisticated devices. This paper provides a thorough review focused on major recent breakthroughs in the area of electromagnetic-triboelectric vibrational energy harvesting. A detailed analysis was conducted on various architectures including rotational, pendulum, linear, sliding, cantilever, flexible blade, multidimensional and magnetoelectric, and the following hybrid technologies. They enable highly efficient ways to harvest electric energy from many forms of vibrational, rotational, biomechanical, wave, wind and thermal sources, among others. Open-circuit voltages up to 75 V, short-circuit currents up to 60 mA and instantaneous power up to 144 mW were already achieved by these nanogenerators. Their transduction mechanisms, including proposed models to make intelligible the involved physical phenomena, are also overviewed here. A comprehensive analysis was performed to compare their respective construction designs, external excitations and electric outputs. The results highlight the potential of hybrid E-TENGs to convert unused mechanical motion into electric energy for both large- and small-scale applications. Finally, this paper proposes future research directions toward optimization of energy conversion efficiency, power management, durability and stability, packaging, energy storage, operation input, research of transduction mechanisms, quantitative standardization, system integration, miniaturization and multi-energy hybrid cells.

Small-scale low pressure ‘single effect distillation’ and ‘single stage flash’ solar driven barometric desalination units: A comparative analysis

Desalination ◽  
2018 ◽  
Vol 444 ◽  
pp. 53-62 ◽  
Author(s):  
Mansoor Siddique ◽  
Nedim Turkmen ◽  
Omar M. Al-Rabghi ◽  
Elsayed Shabana ◽  
Mohammed H. Albeirutty
Keyword(s):  
Comparative Analysis ◽  
Low Pressure ◽  
Single Stage ◽  
Small Scale ◽  
Single Effect

scholarly journals Hydrodynamic constraints on the energy efficiency of droplet electricity generators

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Antoine Riaud ◽  
Cui Wang ◽  
Jia Zhou ◽  
Wanghuai Xu ◽  
Zuankai Wang
Keyword(s):  
Energy Efficiency ◽  
Kinetic Energy ◽  
Total Energy ◽  
Viscous Dissipation ◽  
Shear Force ◽  
Mechanical Energy ◽  
Electric Energy ◽  
The Past ◽  
Viscous Shear ◽  
Impingement Velocity

AbstractElectric energy generation from falling droplets has seen a hundred-fold rise in efficiency over the past few years. However, even these newest devices can only extract a small portion of the droplet energy. In this paper, we theoretically investigate the contributions of hydrodynamic and electric losses in limiting the efficiency of droplet electricity generators (DEG). We restrict our analysis to cases where the droplet contacts the electrode at maximum spread, which was observed to maximize the DEG efficiency. Herein, the electro-mechanical energy conversion occurs during the recoil that immediately follows droplet impact. We then identify three limits on existing droplet electric generators: (i) the impingement velocity is limited in order to maintain the droplet integrity; (ii) much of droplet mechanical energy is squandered in overcoming viscous shear force with the substrate; (iii) insufficient electrical charge of the substrate. Of all these effects, we found that up to 83% of the total energy available was lost by viscous dissipation during spreading. Minimizing this loss by using cascaded DEG devices to reduce the droplet kinetic energy may increase future devices efficiency beyond 10%.

scholarly journals A two-dimensional glacier–fjord coupled model applied to estimate submarine melt rates and front position changes of Hansbreen, Svalbard

2018 ◽  
Vol 64 (247) ◽  
pp. 745-758 ◽  
Author(s):  
E. DE ANDRÉS ◽  
J. OTERO ◽  
F. NAVARRO ◽  
A. PROMIŃSKA ◽  
J. LAPAZARAN ◽  
...  
Keyword(s):  
Coupled Model ◽  
Small Scale ◽  
Two Dimensional ◽  
Time Step ◽  
Software Packages ◽  
Front Position ◽  
Circulation Patterns ◽  
Glacier Front ◽  
Order Of Magnitude ◽  
Frontal Ablation

ABSTRACTWe have developed a two-dimensional coupled glacier–fjord model, which runs automatically using Elmer/Ice and MITgcm software packages, to investigate the magnitude of submarine melting along a vertical glacier front and its potential influence on glacier calving and front position changes. We apply this model to simulate the Hansbreen glacier–Hansbukta proglacial–fjord system, Southwestern Svalbard, during the summer of 2010. The limited size of this system allows us to resolve some of the small-scale processes occurring at the ice–ocean interface in the fjord model, using a 0.5 s time step and a 1 m grid resolution near the glacier front. We use a rich set of field data spanning the period April–August 2010 to constrain, calibrate and validate the model. We adjust circulation patterns in the fjord by tuning subglacial discharge inputs that best match observed temperature while maintaining a compromise with observed salinity, suggesting a convectively driven circulation in Hansbukta. The results of our model simulations suggest that both submarine melting and crevasse hydrofracturing exert important controls on seasonal frontal ablation, with submarine melting alone not being sufficient for reproducing the observed patterns of seasonal retreat. Both submarine melt and calving rates accumulated along the entire simulation period are of the same order of magnitude, ~100 m. The model results also indicate that changes in submarine melting lag meltwater production by 4–5 weeks, which suggests that it may take up to a month for meltwater to traverse the englacial and subglacial drainage network.

Pressure Distributions in the Tip Clearance Region of an Unshrouded Axial Turbine as Affecting the Problem of Tip Burnout

1987 ◽  
Author(s):  
Jeffery P. Bindon
Keyword(s):  
Separation Bubble ◽  
Low Pressure ◽  
High Heat ◽  
Tip Clearance ◽  
Small Scale ◽  
Narrow Strip ◽  
Pressure Surface ◽  
High Heat Transfer ◽  
Axial Turbines ◽  
Secondary Vortices

The pressure distribution in the tip clearance region of a 2D turbine cascade was examined with reference to unknown factors which cause high heat transfer rates and burnout along the edge of the pressure surface of unshrouded cooled axial turbines. Using a special micro-tapping technique, the pressure along a very narrow strip of the blade edge was found to be 2.8 times lower than the cascade outlet pressure. This low pressure, coupled with a thin boundary layer due to the intense acceleration at gap entry, are believed to cause blade burnout. The flow phenomena causing the low pressure are of very small scale and do not appear to have been previously reported. The ultra low pressure is primarily caused by the sharp flow curvature demanded of the leakage flow at gap entry. The curvature is made more severe by the apparent attachement of the flow around the corner instead of immediately separating to increase the radius demanded of the flow. The low pressures are intensified by a depression in the suction corner and by the formation of a separation bubble in the clearance gap. The bubble creates a venturi action. The suction corner depression is due to the mainstream flow moving round the leakage and secondary vortices.

Small-scale dynamic structures in low-pressure microwave discharges

1997 ◽  
Vol 40 (8) ◽  
pp. 663-671 ◽  
Author(s):  
N. V. Vvedenskii ◽  
N. K. Vdovicheva ◽  
V. B. Gil’denburg ◽  
N. A. Zharova ◽  
I. A. Shereshevskii ◽  
...  
Keyword(s):  
Low Pressure ◽  
Small Scale ◽  
Dynamic Structures ◽  
Microwave Discharges

Isolation of Immunoglobulin from Chicken Egg Yolk using Single-Stage Ultrafiltration with 100-kDa Regenerated Cellulose Membranes

2011 ◽  
Vol 7 (1) ◽  
Author(s):  
Jianguo Liu ◽  
Juan Yang ◽  
Hai Xu ◽  
Hu Zhu ◽  
Jianbo Qu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Egg Yolk ◽  
Single Stage ◽  
Regenerated Cellulose ◽  
Cellulose Membrane ◽  
Permeate Flux ◽  
Operational Parameters ◽  
Solution Ph ◽  
Chicken Egg ◽  
Chicken Egg Yolk

The aim of this work is to develop a membrane-based cost-effective process for the rapid isolation of immunoglobulin from chicken egg yolk. It was found that a single-stage ultrafiltration using a 100 kDa molecular weight cut-off regenerated cellulose membrane could be employed to isolate immunoglobulin from the crude feedstock. The effects of operational parameters (solution pH, ionic strength, stirring speed and permeate flux) on the transmission of immunoglobulin and the presence of impurity protein with molecular weight close to immunoglobulin were quantified using the parameter scanning ultrafiltration technique. Under optimized conditions, the purity of immunoglobulin obtained was about 85 percent after the single-stage ultrafiltration process, and the recovery of immunoglobulin from the feedstock was 91 percent.

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