Effects of gas pressure on dynamic response of two-phase flow for coal–gas outburst

2021 ◽  
Vol 377 ◽  
pp. 55-69
Author(s):  
Bin Zhou ◽  
Jiang Xu ◽  
Fazhi Yan ◽  
Shoujian Peng ◽  
Yabin Gao ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Two Phase Flow ◽  
Gas Pressure ◽  
Phase Flow ◽  
Two Phase ◽  
Coal Gas ◽  
Gas Outburst

scholarly journals Experiment Study of Outburst Pulverized Coal-Gas Two-Phase Flow and Characteristic Analysis of Outburst Wave

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xusheng Zhao ◽  
Jie Cao ◽  
Bo Wang ◽  
Xuelin Yang
Keyword(s):  
Gas Flow ◽  
Two Phase Flow ◽  
Pulverized Coal ◽  
Coal And Gas Outburst ◽  
Phase Flow ◽  
Flow State ◽  
Two Phase ◽  
Coal Gas ◽  
Gas Outburst ◽  
Propagation Velocities

Coal and gas outburst is still a major safety problem in the process of coal production in China. Correctly understanding of the migration law of outburst high gas and pulverized coal is an important basis for accurately predicting the occurrence time and possible scope of outburst. To reveal the airflow disturbance characteristics and coal-gas flow rule in coal and gas outburst process, outburst coal-gas migration simulations under different gas pressures were conducted using a self-developed visual outburst dynamic effect test device. The results showed that coal-gas flow state at the outburst port is divided into subcritical flow, critical flow, and supercritical flow state. The pulverized coal-gas flow migration in the roadway space can be divided into coal gas two-phase flow area, air compression area, and undisturbed area. Under the experimental conditions, the maximum propagation velocities of wave are 342.22~359.21 m/s, and the coal gas two-phase flow is far less than the propagation velocities of outburst wave, just 3.68~33.33 m/s. When the outburst energy is large, multiple compression waves can superimpose to form shock waves. The peak value of the wave does not necessarily appear in the first boosting range. The presence of pulverized coal leads to a faster attenuation of shock wave, but it makes a greater dynamic destructive force at the same speed.

scholarly journals EDEM-FLUENT coupled simulation of coal-gas outburst two-phase flow

2021 ◽  
pp. 014459872110238
Author(s):  
Feng Du ◽  
Yangyang Guo ◽  
Liang Wang ◽  
Chao Xu ◽  
Aitao Zhou ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Physical Simulation ◽  
Two Phase Flow ◽  
Underground Mining ◽  
Pulverized Coal ◽  
Phase Flow ◽  
Two Phase ◽  
Coal Gas ◽  
Gas Outburst ◽  
Short Time

In the process of coal-gas outburst, the gas-solid two-phase flow of pulverized coal and gas will induce large-scale damage to underground mining. In this work, in order to study the dynamic evolution law of gas-solid two-phase flow of coal-gas outburst, and clarify the short-time destructive effect of outburst dynamic phenomenon, an EDEM-FLUENT coupled model is constructed to realize the numerical simulation of coal-gas outburst two-phase flow. The simulation results show that the flow velocity of pulverized coal in a short time (tens of milliseconds) approaches to the maximum velocity rapidly, which can reach 60 m/s. The velocity of pulverized coal is inversely proportional to the particle size. The initial acceleration of particles is slow, and then the acceleration increases rapidly. The accumulation angle of pulverized coal in the outburst hole is about 21° and is far less than the natural accumulation angle of pulverized coal, which is consistent with the general phenomenon of coal-gas outbursts. The results also show that the shock wave overpressure of the coal-gas outburst of numerical simulation is similar to that of the physical simulation test, and the difference is less than 10%. And the pressure change in the roadway is completed in short time. In terms of spatial relationships, the pressure at the position closest to the outburst mouth is not the maximum, and the maximum pressure exists at a certain position away from the outburst mouth.

Two-Phase Flow Characteristics in a Co-Flow Induced Microchannel With Microbubbles Generation

2007 ◽  
Author(s):  
Sujin Yeom ◽  
Seung S. Lee ◽  
Sang Yong Lee
Keyword(s):  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Gas Pressure ◽  
Superficial Velocity ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Gas Channel ◽  
Micro Bubble

This paper presents a micro-fluidic device which generates micro-bubbles, ranging from 70μm to 160μm in diameter, and two-phase flow characteristics in the device were tested. The device is composed of three sub-channels: a centered gas channel (10μm×50μm) and two liquid channels (both with 85μm×50μm) on each side of the gas channel. Micro-bubbles are generated by co-flow of gas and liquid at the exit of the gas channel when the drag force becomes larger than the surface tension force as bubbles grow. Methanol and a gas mixture of CO2 and N2 were used as the working fluid. Since the flow rate of gas was very small, the gas momentum effect was considered negligible. Thus, in the present case, the controlling parameters were the liquid superficial velocity and the inlet pressure of the gas. A high speed camera was used to record two-phase flow patterns and micro-bubbles of the device. To confine the ranges of the micro-bubbles generation, two-phase flow patterns in the device is observed at first. Four different flow patterns were observed: annular, annular-slug, slug, and bubbly flow. In bubbly flows, uniform-sized micro-bubbles were generated, and the operating ranges of the liquid superficial velocity and the gas pressure were below 0.132 m/s and 0.7 bar, respectively. Diameters of the micro-bubbles appeared smaller with the higher superficial liquid velocity and/or with a lower gas pressure. Experimental results showed that, with the gas pressure lower than a certain level, the sizes of micro-bubbles were almost insensitive to the gas pressure. In such a ranges, the micro-bubble diameters could be estimated from a drag coefficient correlation, CDw = 31330/Re3, which is different from the correlations for macro-channels due to a larger wall effect with the micro-channels. In the latter part of the paper, as a potential of application of the micro-bubble generator to gas analysis, dissolution behavior of the gas components into the liquid flow was examined. The result shows that the micro-bubble generator can be adopted as a component of miniaturized gas analyzers if a proper improvement could be made in controlling the bubble sizes effectively.

scholarly journals Gas pressure deop and liquid holdup for two-phase flow of air-water in crossflow packed columns.

1988 ◽  
Vol 14 (1) ◽  
pp. 107-111 ◽  
Author(s):  
Yoshishige Hayashi ◽  
Eiji Hirai ◽  
Yasuhide Nakano ◽  
Masakatsu Urairi
Keyword(s):  
Two Phase Flow ◽  
Packed Columns ◽  
Gas Pressure ◽  
Phase Flow ◽  
Liquid Holdup ◽  
Two Phase

scholarly journals Numerical simulation of hydraulic fracturing in coal seam for enhancing underground gas drainage

2018 ◽  
Vol 37 (1) ◽  
pp. 166-193 ◽  
Author(s):  
Chaojun Fan ◽  
Sheng Li ◽  
Mingkun Luo ◽  
Zhenhua Yang ◽  
Tianwei Lan
Keyword(s):  
Elastic Modulus ◽  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Two Phase Flow ◽  
Damage Zone ◽  
Gas Pressure ◽  
Phase Flow ◽  
Two Phase ◽  
Gas Flux ◽  
Gas Drainage

Hydraulic fracturing is an efficiency approach to improve underground gas drainage. Although the interaction of fluid and coal has been comprehensively investigated in fracturing process and gas drainage process, fewer scholars have combined these two processes together and taken the gas–water two-phase flow into account, which brought a large deviation for design of hydraulic fracturing enhancing underground gas drainage. In this paper, we proposed a fully coupled hydraulic stress damage mathematical model considering gas–water two-phase flow, which can be used to simulate the whole process of hydraulic fracturing enhancing underground gas drainage. The coal seam is simplified as a dual-porosity single-permeability elastic media with elastic modulus reduce and permeability increase when encountered damage. The permeability and porosity serving as the coupling term is a function of stress, water/gas pressure, gas ad/desorption, and damage value. The proposed model was first verified by showing that the modeled gas flux agrees with the field data. The evolution laws of permeability and gas pressure during hydraulic fracturing enhancing underground gas drainage were studied and several influence factors were analyzed by accomplishing a series of simulations. Gas drainage can be effectively enhanced only when the hydraulic fracturing induced damage zone is breakthrough at drainage hole. After the coal seam is effectively fractured, the gas flux has a decline–incline–decline tendency with increasing of drainage time. The breakthrough time of damage zone increases linearly with coal seam elastic modulus, increases exponentially with vertical stress and borehole spacing, and decreases exponentially with injecting pressure.

The Numerical Simulation of Gas-Pulverized Coal Two Phase Flow after Coal and Gas Outburst

2012 ◽  
Vol 524-527 ◽  
pp. 776-780 ◽  
Author(s):  
Bai Sheng Nie ◽  
Xiang Chun Li ◽  
Wen Bo Liu ◽  
Yang Wang ◽  
Xiao Yan Wang ◽  
...  
Keyword(s):  
Two Phase Flow ◽  
Volume Fraction ◽  
Pulverized Coal ◽  
Coal And Gas Outburst ◽  
Damage Effect ◽  
Maximum Speed ◽  
Phase Flow ◽  
Two Phase ◽  
Emergency Rescue ◽  
Gas Outburst

The gas-pulverized coal two phase flow law of gas is simulated by the use of the theory of jet after coal and gas outburst. Research results show that as the volume fraction of pulverized coal in outbursts mixture increases, the speed of two phase flow at the exit gradually reduces, jet core length shorter, turbulent longitudinal effect range smaller, jet width narrower. And dynamic head mainly concentrates in the jet core area and its distribution is more uniform in the roadways. The maximum speed of outburst two-phase flow decreases with the adding volume fraction of pulverized coal, that is higher the coal content in outburst mixtures, smaller the maximum speed after outburst. But a high content of coal have higher impact strike force which can cause major damage effect. The research may provide some theoretical basis for setting underground safety facilities, mine personal protection, disaster warning and emergency rescue.

New approach for two-phase flow calcuation of artifical lift

2021 ◽  
pp. 49-55
Author(s):  
V.J. Abdullayev ◽  
Keyword(s):  
Pressure Difference ◽  
Two Phase Flow ◽  
Gas Pressure ◽  
Phase Flow ◽  
Opening Pressure ◽  
Two Phase ◽  
New Approach ◽  
Valve Opening ◽  
Gas Lift ◽  
Design Pressure

The article develops a method for adjusting design pressure of bellows gas lift valves in deviated gas lift wells based on research and calculations and provides a method for the arrangement of gas lift valves along tubing. As a result of the calculations, the valve opening pressure of the first gas lift valve was taken equal to the initial gas pressure, the valve opening pressure of the following valves was 0.05-0.175 MPa lower than that of the previous gas lift valve, and the pressure difference between the last valve and the second from the last valve was 0.28-0.35 MPa.

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