Performance enhancement of a Darrieus hydrokinetic turbine with the blocking of a specific flow region for optimum use of hydropower

2019 ◽  
Vol 135 ◽  
pp. 1144-1156 ◽  
Author(s):  
Vimal Patel ◽  
T.I. Eldho ◽  
S.V. Prabhu
Author(s):  
M. Simoes ◽  
O. Simonin

In space propulsion, compressible reactive dispersed two-phase flows are investigated in order to predict the behavior of solid or liquid rocket motors. In the frame of full Eulerian approach, physical modeling of aerodynamic flows in such motors is performed resolving unsteady compressible Navier-Stokes equations for both phases. However, numerical simulations performed on a simple axisymmetric motor have pointed out a flaw of this basic Eulerian approach. Indeed, the variance of the particle velocity distribution is not accounted for, leading to unrealistic accumulations of particles in some specific flow region. To correct this shortcoming, we have developed an advanced Eulerian model based on a statistical approach in the framework of the Mesoscopic Eulerian Formalism (MEF).


2020 ◽  
Vol 10 (18) ◽  
pp. 6284
Author(s):  
Dong Kyun Kim

Recently, many refrigerators of high have been designed so as to improve the performance of the refrigerator and to economize on energy. There are many methods of improving the total efficiency of the refrigerators using a methodological approach. In this experimental and numerical study, three methods—namely, modifying the flow channel and the operating conditions and changing the positions of the fan at the mechanical chamber room (MCR)—are used to analyze the performance improvement of the refrigerator. These methods of changing the flow channel in an MCR of a refrigerator are, in many ways, used as a regulation of the upper flow region of the condenser, especially in this research. Modifying the refrigerators’ MCR is carried out by changing the shape of the cover back machine (CBM). We compute the fluid flow in a refrigerator MCR by computational fluid dynamics (CFD) techniques. The commercial code ANSYS CFX 16.2 is used for this computation. The regulation flow region shows a reduction in power consumption of about 0.75% per month. The result of the operating conditions of the fan at MCR is relative to the flow rate for reducing power consumption. The changing positions are also relative to the length of the reducing power consumption. Moreover, with the results obtained by CFD, we understand the flow structure in a refrigerators’ MCR for various types of CBM. The results also show that the efficiency of the refrigerator is improved by 1.2%.


2020 ◽  
Vol 18 (1) ◽  
pp. 51-65 ◽  
Author(s):  
Mabrouk Mosbahi ◽  
Sana Elgasri ◽  
Mariem Lajnef ◽  
Bouzid Mosbahi ◽  
Zied Driss

Author(s):  
Marine Simoes ◽  
Patrick Della Pieta ◽  
Franck Godfroy ◽  
Olivier Simonin

In solid rocket motors (SRM) used for space propulsion, such as Ariane 5, aluminum is frequently used as a propellant additive to increase specific impulse. However, its combustion produces aluminum oxide residues that are carried away by the flow field. Thus, physical modeling of aerodynamic flows in SRM should account for this condensed phase. In the frame of full Eulerian approach, unsteady compressible Navier-Stokes equations are solved for both phases. However, numerical simulations performed on a simple axisymmetric motor have pointed out a flaw of the basic Eulerian approach. Indeed, the variance of the particle velocity distribution is not accounted for, leading to unrealistic accumulations of particles in some specific flow region. Hence, we have developed an advanced Eulerian model to correct this shortcoming, which is presented in this paper.


2003 ◽  
Author(s):  
M. Bar-Eli ◽  
O. Lowengart ◽  
J. Goldberg ◽  
S. Epstein ◽  
R. D. Fosbury

2020 ◽  
Vol 91 (3) ◽  
pp. 30201
Author(s):  
Hang Yu ◽  
Jianlin Zhou ◽  
Yuanyuan Hao ◽  
Yao Ni

Organic thin film transistors (OTFTs) based on dioctylbenzothienobenzothiophene (C8BTBT) and copper (Cu) electrodes were fabricated. For improving the electrical performance of the original devices, the different modifications were attempted to insert in three different positions including semiconductor/electrode interface, semiconductor bulk inside and semiconductor/insulator interface. In detail, 4,4′,4′′-tris[3-methylpheny(phenyl)amino] triphenylamine (m-MTDATA) was applied between C8BTBTand Cu electrodes as hole injection layer (HIL). Moreover, the fluorinated copper phthalo-cyanine (F16CuPc) was inserted in C8BTBT/SiO2 interface to form F16CuPc/C8BTBT heterojunction or C8BTBT bulk to form C8BTBT/F16CuPc/C8BTBT sandwich configuration. Our experiment shows that, the sandwich structured OTFTs have a significant performance enhancement when appropriate thickness modification is chosen, comparing with original C8BTBT devices. Then, even the low work function metal Cu was applied, a normal p-type operate-mode C8BTBT-OTFT with mobility as high as 2.56 cm2/Vs has been fabricated.


2019 ◽  
Vol 13 (3) ◽  
pp. 5242-5258
Author(s):  
R. Ravivarman ◽  
K. Palaniradja ◽  
R. Prabhu Sekar

As lined, higher transmission ratio drives system will have uneven stresses in the root region of the pinion and wheel. To enrich this agility of uneven stresses in normal-contact ratio (NCR) gearing system, an enhanced system is desirable to be industrialized. To attain this objective, it is proposed to put on the idea of modifying the correction factor in such a manner that the bending strength of the gearing system is improved. In this work, the correction factor is modified in such a way that the stress in the root region is equalized between the pinion and wheel. This equalization of stresses is carried out by providing a correction factor in three circumstances: in pinion; wheel and both the pinion and the wheel. Henceforth performances of this S+, S0 and S- drives are evaluated in finite element analysis (FEA) and compared for balanced root stresses in parallel shaft spur gearing systems. It is seen that the outcomes gained from the modified drive have enhanced performance than the standard drive.


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