scholarly journals ВИЗНАЧЕННЯ КОНСТРУКТИВНИХ ПАРАМЕТРІВ ПРОТОЧНОЇ ЧАСТИНИ АЕРОТЕРМОПРЕСОРА СИСТЕМИ ОХОЛОДЖЕННЯ ЦИКЛОВОГО ПОВІТРЯ МІКРОТУРБІН

2019 ◽  
pp. 44-50
Author(s):  
Галина Олександрівна Кобалава
Keyword(s):  
Cfd Simulation ◽  
Air Flow ◽  
Calculated Data ◽  
Resistance Coefficient ◽  
Low Flow ◽  
Analytical Determination ◽  
Geometrical Parameters ◽  
Local Resistance ◽  
Research Areas ◽  
Divergent Angle

Among modern jet technologies, one of the promising research areas is a study of gas-dynamic processes in the aerothermopressor. This jet apparatus is a device for contact cooling (the heat from the air flow is consumed for the instantaneous evaporation of water droplets), in which there is a thermogasdynamic compression effect, and that is, the air pressure increase is taken place. A significant influence on the working processes in the aerothermopressor is exercised by design factors. The influence of these factors on energy costs to overcome the friction losses and local resistances on the convergent-divergent sections of the apparatus was investigated. Relevant in the aerothermopressors development is to determinate of rational parameters of the workflow organization with the corresponding development of the flow part design. At the same time, it is necessary to have an opportunity for analytical determination of pressure losses in the confuser and diffuser of the aerothermopressor. A research of typical models of the aerothermopressor for a number of taper angles of a confuser a (convergent angle a = 30; 35; 40; 45; 50 °) and diffuser b (divergent angle b = 6; 8; 10; 12 °), for a number of air velocity values in the working chamber M = 0.4-0.8 has been carried out. The obtained calculated data (results of computer CFD-simulation) and experimental data have been compared. The error of the values for the coefficients of local resistances in the confuser and diffuser does not exceed 7-10%. It was established that the value of the local resistance coefficient depends only on the geometrical parameters (the angle of tapering and the diameters ratio of the input and output D1/D2), that is, the air flow character in the aerothermopressor corresponds to the self-similar mode. The recommended angles were determined: confuser convergent angle a = 30 ° and diffuser divergent angle b = 6 °, corresponding to the minimum pressure loss DPloss = 1.0–9.5 %. The empirical equations were defined for determining the local resistance coefficients of the confuser and diffuser, which can be recommended for use in the design of low-flow aerothermopressor for microturbines

scholarly journals Numerical Calculation of the Tee Local Resistance Coefficient

2015 ◽  
Vol 9 (1) ◽  
pp. 876-881 ◽  
Author(s):  
Qin Zhang ◽  
Manlai Zhang ◽  
Zhihong Zhou ◽  
Shizhong Wei
Keyword(s):  
Cfd Simulation ◽  
Flux Ratio ◽  
Frictional Resistance ◽  
Resistance Coefficient ◽  
Head Loss ◽  
Local Resistance ◽  
Local Resistance Coefficient ◽  
Tee Junction ◽  
Resistance Coefficients

The local head loss of tee could be calculated with the determination of local resistance coefficient by CFD simulation and test. Based on the mesh-independent feature identified, the flow field inner tee was numerically simulated by the standard k - ε turbulent model and SIMPLEC algorithms, which has revealed the mainstream was obliged to turn to the opposite side of tee junction, and a rise in pressure drop between upstream and downstream was caused as a result. Furthermore, the frictional resistance coefficient was calculated for eliminating the frictional head loss of model, which decreased from 0.0207 to 0.0133 when the inlet velocity increased from 1 m/s to 12 m/s. Additionally, the local resistance coefficients of tee at flow conditions were attained, and the quadratic polynomial between the local resistance coefficient and flux ratio was presented due to the influence of branch on mainstream. Through the test, the simulation result has been compared and the effectiveness of simulation has been verified.

The Air Consumption Estimation of Convection Heaters with Natural Convection and Water Heat Carrier

2015 ◽  
Vol 725-726 ◽  
pp. 1301-1306
Author(s):  
Viktor Pukhkal
Keyword(s):  
Natural Convection ◽  
Heat Flow ◽  
Heat Carrier ◽  
Natural Circulation ◽  
Air Flow ◽  
Resistance Coefficient ◽  
Local Resistance ◽  
Cold Air ◽  
Effective System ◽  
Local Resistance Coefficient

The knowledge of temperature and air consumption at the output of a convection heater is required to develop an effective system protecting serviced room zones against descending cold air flow near the glassing. The existing method of heat appliances’ study and calculation, which uses an idea of nominal heat flow, does not provide those parameters. The analytic correlation between aerodynamical and thermotechnical characteristics of heat convectors with natural circulation at nominal conditions is established. The experimental estimation of air consumption and local resistance coefficient of „Atoll“ (PKN 309) convection heater is carried out. The obtained dependencies allow calculating temperature and air consumption at convection heater output by the existing method of heat appliances’ calculation using nominal heat flow.

EXPERIMENTAL AND ANALYTICAL STUDIES OF VERTICAL AXIS WIND TURBINES

2018 ◽  
pp. 51-58
Author(s):  
B. P. Khozyainov
Keyword(s):  
Wind Turbine ◽  
Flow Velocity ◽  
Wind Power ◽  
Wind Turbines ◽  
Power Efficiency ◽  
Air Flow ◽  
Geometrical Parameters ◽  
Wind Speeds ◽  
Analytical Studies ◽  
Air Flow Velocity

The article carries out the experimental and analytical studies of three-blade wind power installation and gives the technique for measurements of angular rate of wind turbine rotation depending on the wind speeds, the rotating moment and its power. We have made the comparison of the calculation results according to the formulas offered with the indicators of the wind turbine tests executed in natural conditions. The tests were carried out at wind speeds from 0.709 m/s to 6.427 m/s. The wind power efficiency (WPE) for ideal traditional installation is known to be 0.45. According to the analytical calculations, wind power efficiency of the wind turbine with 3-bladed and 6 wind guide screens at wind speedsfrom 0.709 to 6.427 is equal to 0.317, and in the range of speed from 0.709 to 4.5 m/s – 0.351, but the experimental coefficient is much higher. The analysis of WPE variations shows that the work with the wind guide screens at insignificant average air flow velocity during the set period of time appears to be more effective, than the work without them. If the air flow velocity increases, the wind power efficiency gradually decreases. Such a good fit between experimental data and analytical calculations is confirmed by comparison of F-test design criterion with its tabular values. In the design of wind turbines, it allows determining the wind turbine power, setting the geometrical parameters and mass of all details for their efficient performance.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

scholarly journals Calculated research of aeroelastic stability of a bridge over the river Ob in Salekhard at the stage of assembling and operation

2019 ◽  
Vol 6 (3) ◽  
Author(s):  
Anastasiya Shustikova ◽  
Andrei Kozichev ◽  
Sergei Paryshev ◽  
Konstantin Strelkov
Keyword(s):  
Cfd Simulation ◽  
Load Capacity ◽  
Air Flow ◽  
Lift Coefficient ◽  
High Strength ◽  
Railway Bridge ◽  
Aeroelastic Stability ◽  
Ansys Fluent ◽  
Long Span ◽  
Long Span Bridge

Recently, long span bridge construction has been demanded for development of the regions of the Russian Federation. In terms of economy, it’s useful to build a combined road-railway bridge. Such bridges, generally, constitute a metal cross-cutting girder with carriageways on lower, upper or both zones of the girder. The major advantages of combined bridges are high strength and load capacity, plus cross-cutting to wind load. Focus of this research is a combined road-railway bridge over the Ob river at the stage of assembling and operation. The purpose of the study was to determine the limits of aeroelastic stability of combined road-railway bridge at the stage of assembling and operation using numerical simulation. To better understand the bridges behaviour in air flow, flow around a section model has been researched with CFD simulation in the ANSYS FLUENT. Then based on the given results of the calculations the dependence of the bridge vibrations on wind speed within a specified range is obtained, and also values of drag coefficient Сх, lift coefficient Су and torque coefficient Мz are received. These studies were carried out in the range of angles of attack α = ±3°. The possibility of divergence and galloping was also estimated. The results of the study made it possible to estimate the influence of air flow on combined bridge cross-cutting girder. Overall, the conducted research seems promising for further investigation and development in the field of bridge aeroelasticity.

Complete Williams Asymptotic Expansion near the Crack Tips of Collinear Cracks of Equal Lengths in an Infinite Plane

2016 ◽  
Vol 258 ◽  
pp. 209-212 ◽  
Author(s):  
Larisa Stepanova ◽  
Pavel Roslyakov ◽  
Tatjana Gerasimova
Keyword(s):  
Plane Elasticity ◽  
Analytical Determination ◽  
Geometrical Parameters ◽  
Infinite Plane ◽  
Variable Theory ◽  
Complex Variable Theory ◽  
Plane Medium ◽  
Crack Tips ◽  
Plane Elasticity Theory

The present study is aimed at analytical determination of coefficients in crack tip expansion for two collinear finite cracks of equal lengths in an infinite plane medium. The study is based on the solutions of the complex variable theory in plane elasticity theory. The analytical dependence of the coefficients on the geometrical parameters and the applied loads for two finite cracks in an infinite plane medium is given. It is shown that the effect of the higher order terms of the Williams series expansion becomes more considerable at large distances from the crack tips. The knowledge of more terms of the stress asymptotic expansions allows us to approximate the stress field near the crack tips with high accuracy.

Theoretical leakage equations towards liquid-phase flow in the straight-through labyrinth seal

2021 ◽  
pp. 1-44
Author(s):  
Lingsheng Han ◽  
Yongqing Wang ◽  
Kuo Liu ◽  
Ziyou Ban ◽  
Bo Qin ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Numerical Approach ◽  
Labyrinth Seal ◽  
Resistance Coefficient ◽  
Cryogenic Cooling ◽  
Geometrical Parameters ◽  
Phase Flow ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
Empirical Coefficients

Abstract Labyrinth seals are widely applied in turbomachinery for gas and liquid sealing. A series of labyrinth seal leakage equations so far have been proposed for compressible gas, but few equations for incompressible liquid. Based on the flow conserving governing equations, this paper originally presents semi-empirical analytic equations of the leakage flow rate and tooth-clearance pressure for liquid-phase flow in the straight-through labyrinth seal. The equations indicate that the leakage and pressure are closely related to the inlet pressure, outlet pressure, seal geometrical parameters and four empirical coefficients, whilst no relation to the temperature and compressibility effects compared to the common gas equations. The empirical coefficients include the velocity compensation coefficient, friction coefficient, jet contraction coefficient and resistance coefficient. Particularly, the velocity compensation coefficient is determined through an optimization by the genetic algorithm, while others are referred from previous research. Ultimately, taking the sealing of deeply subcooled liquid nitrogen within the spindle of the cryogenic cooling machine tool as a case, the accuracy of proposed equations is evaluated under various pressure ratios and geometry conditions using the numerical approach, whose numerical model has been validated by the experimental data in the literature. The results show that errors between calculation and simulation are generally within the limit of ±5%, except for the pressure values at the first two teeth. This work provides a theoretical basis for further studies on the liquid leakage equations in other labyrinth seal types.

Investigating barotrauma in juvenile salmon passing through a very low head turbine using response surface methodology

2021 ◽  
pp. 095440622110504
Author(s):  
Mehrshad Foroughan ◽  
Alireza Riasi ◽  
Amir Bahreini
Keyword(s):  
Chinook Salmon ◽  
Cfd Simulation ◽  
Geometrical Parameters ◽  
Innovative Design ◽  
Computational Costs ◽  
Water Turbine ◽  
Low Head ◽  
Computational Fluid Dynamics Cfd ◽  
Biological Performance ◽  
Riverine Fish

Although hydropower is a clean source of energy, in some cases, it can jeopardize the life of some species of riverine fish. Very Low Head (VLH) water turbine is an innovative design that aims at reducing the adverse effects of such hydroelectric facilities. In this research, two methodologies are integrated to investigate barotrauma in juvenile salmons passing through this particular turbine. First, to quantify barotrauma, we implement a method known as BioPA (Biological Performance Assessment) by combining the results of some laboratory experiments on juvenile Chinook salmon moving through a simulated turbine passage with the Computational Fluid Dynamics (CFD) simulation of the flow field in this environment. In the second part, we added surrogate-based modeling as a tool, which enabled us to study the effects of two geometrical parameters on the environmental performance of the VLH turbine with low computational costs. The results indicate a significant dependency between the installation angle of the VLH turbine and the severity of the barotrauma of this particular fish. In addition, further investigations suggest that the region near the middle of blades is the safest for fish in the case of decompression.

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