scholarly journals Theoretical study of the process of interaction of particles of weed impurities in the flow of raw cotton with the working bodies of the cleaning machine

2020 ◽  
Vol 6 (4) ◽  
Author(s):  
Abdurakhmonov Akmalzhon Akbarovich ◽  
Gaybnazarov Egamnazar Eryigitovich
Keyword(s):  
Velocity Distribution ◽  
Flow Velocity ◽  
Euler Equations ◽  
Theoretical Study ◽  
Stationary Flow ◽  
Flow Rates ◽  
Mesh Surface ◽  
Cleaning Machine ◽  
Working Bodies ◽  
Moving Layer

The article proposes to use the Euler equations to describe the motion of a stationary flow in the cleaning zones, which allows determining the laws of pressure, density and velocity distribution along the arc of contact of a moving layer of raw cotton with a mesh surface in the process of impact impact with spikes on the pulp. It has been established that the pressure, densities and flow rates along the cleaning arc as a result of hammer spikes vary in steps, with a decrease in pressure and density and an increase in the flow velocity along this arc.

scholarly journals Powder flow down a vertical pipe: the effect of air flow

2002 ◽  
Vol 459 ◽  
pp. 317-345 ◽  
Author(s):  
Y. BERTHO ◽  
F. GIORGIUTTI-DAUPHINÉ ◽  
T. RAAFAT ◽  
E. J. HINCH ◽  
H. J. HERRMANN ◽  
...  
Keyword(s):  
Small Diameter ◽  
Stationary Flow ◽  
Momentum Conservation ◽  
Wall Friction ◽  
Particle Fraction ◽  
Friction Forces ◽  
Flow Rates ◽  
Lower Flow ◽  
Grain Flow ◽  
Grain Distribution

The dynamics of dry granular flows down a vertical glass pipe of small diameter have been studied experimentally. Simultaneous measurements of pressure profiles, air and grain flow rates and volume fractions of particles have been realized together with spatio-temporal diagrams of the grain distribution down the tube. At large grain flow rates, one observes a stationary flow characterized by high particle velocities, low particle fractions and a downflow of air resulting in an underpressure in the upper part of the pipe. A simple model assuming a free fall of the particles slowed down by air friction and taking into account finite particle fraction effects through Richardson–Zaki's law has been developed: it reproduces pressure and particle fraction variations with distance and estimates friction forces with the wall. At lower flow rates, sequences of high-density plugs separated by low-density bubbles moving down at a constant velocity are observed. The pressure is larger than outside the tube and its gradient reflects closely the weight of the grains. Writing mass and momentum conservation equations for the air and for the grains allows one to estimate the wall friction, which is less than 10% of the weight for grains with a clean smooth surface but up to 30% for grains with a rougher surface. At lower flow rates, oscillating-wave regimes resulting in large pressure fluctuations are observed and their frequency is predicted.

Numerical Simulation of Impacts of Different Types of Air Duct Outlets on Ventilation Efficiency

2013 ◽  
Vol 438-439 ◽  
pp. 1098-1103
Author(s):  
Chun Zi Nan ◽  
Ji Ming Ma ◽  
Luo Zhao
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Velocity Distribution ◽  
Flow Velocity ◽  
Numerical Method ◽  
Concentration Effect ◽  
Mixing Zone ◽  
Mixing Effect ◽  
Ventilation Efficiency ◽  
Different Types

To enhance the exhaust efficiency during ventilation, three types of air duct outlets were imported. According to the characteristics of velocity distribution simulated by numerical method, the flow field is divided into the mixing zone and the exhaust zone. The gradual contracted air duct outlet can enhance the mixing effect between fresh air and smoke. In the exhaust zone, however, the flow velocity on the upper section of the tunnel is weakened, which is unfavorable for smoke exhaust. Gradual expanded air duct outlet, on the contrary, may weaken the concentration effect of the airflow. The flow velocity on the upper section of the tunnel is increased in the exhaust zone, thus the flow field is more homogenized, which is in favor of smoke exhaust.

scholarly journals Study on the Formation Law of the Freezing Temperature Field of Freezing Shaft Sinking under the Action of Large-Flow-Rate Groundwater

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Bin Wang ◽  
Chuan-xin Rong ◽  
Jian Lin ◽  
Hua Cheng ◽  
Hai-bing Cai
Keyword(s):  
Temperature Field ◽  
Groundwater Flow ◽  
Flow Velocity ◽  
Flow Rate ◽  
Freezing Temperature ◽  
Freezing Process ◽  
Flow Rates ◽  
Porosity Reduction ◽  
Shaft Sinking ◽  
Large Flow

Taking into account moisture migration and heat change during the soil freezing process, as well as the influence of absolute porosity reduction on seepage during the freezing process, we construct a numerical model of hydrothermal coupling using laws of conservation of energy and mass. The model is verified by the results of large-scale laboratory tests. By applying the numerical calculation model to the formation of artificial shaft freezing temperature fields under the action of large-flow groundwater, we conclude that groundwater with flow rates of less than 5 m/d will not have a significant impact on the artificial freezing temperature field. The maximum flow rates that can be handled by single-row freezing pipes and double-row freezing pipes are 10 m/d and 20 m/d, respectively, during the process of freezing shaft sinking. By analyzing the variation of groundwater flow rate during freezing process, we find that the groundwater flow velocity can reach 5–7 times the initial flow velocity near the closure moment of the frozen wall. Finally, in light of the action characteristics of groundwater on the freezing temperature field, we make suggestions for optimal pipe and row spacing in freezing pipe arrangement.

scholarly journals Flow-velocity model for hydrokinetic energy availability assessment in the Amazon

2019 ◽  
Vol 42 ◽  
pp. e45703
Author(s):  
Josias da Silva Cruz ◽  
Claudio José Cavalcante Blanco ◽  
Antônio César Pinho Brasil Junior
Keyword(s):  
Flow Velocity ◽  
Amazon Basin ◽  
Velocity Model ◽  
Amazon River ◽  
Data Series ◽  
Flow Rates ◽  
Hydrokinetic Energy ◽  
Historical Series ◽  
Flood Period ◽  
Availability Assessment

The Brazilian hydrological information network does not provide data series of daily velocities. The river velocities are important for the study of hydrokinetic potential. Therefore, the work proposes a model called flow-velocity that estimates the average daily velocity and the distribution of the velocity profile of the cross section of rivers. The model was applied to the Amazon basin, using the highest and lowest flow rates of the historical series. The highest and lowest average velocities found in the Amazon River were 2.27 m s-1 and 0.735 m s-1, respectively. The main contributors to the Amazon River presented average daily velocities close to 2.0 ms-1 for the flood period, but in the dry season these velocities did not exceed 0.5 m s-1. Thus, it was verified that the Amazon River has hydrokinetic potential throughout the year and its tributaries during the flood period.

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