Design of auto air pressure balance system for fire control and numerical simulation of pressure balance effect

2011 ◽  
Author(s):  
Zhu Hongqing ◽  
Zhang Zhengyu ◽  
Hao Junwei ◽  
Li Feng ◽  
Lv Dongnan
Keyword(s):  
Numerical Simulation ◽  
Air Pressure ◽  
Pressure Balance ◽  
Fire Control ◽  
Balance System

scholarly journals Numerical Simulation of EPB Shield Tunnelling with TBM Operational Condition Control Using Coupled DEM–FDM

2021 ◽  
Vol 11 (6) ◽  
pp. 2551
Author(s):  
Hyobum Lee ◽  
Hangseok Choi ◽  
Soon-Wook Choi ◽  
Soo-Ho Chang ◽  
Tae-Ho Kang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Tunnel Boring Machine ◽  
Chamber Pressure ◽  
Screw Conveyor ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Operational Conditions ◽  
Shield Tunnelling ◽  
Epb Shield

This study demonstrates a three-dimensional numerical simulation of earth pressure balance (EPB) shield tunnelling using a coupled discrete element method (DEM) and a finite difference method (FDM). The analysis adopted the actual size of a spoke-type EPB shield tunnel boring machine (TBM) consisting of a cutter head with cutting tools, working chamber, screw conveyor, and shield. For the coupled model to reproduce the in situ ground condition, the ground formation was generated partially using the DEM (for the limited domain influenced by excavation), with the rest of the domain being composed of FDM grids. In the DEM domain, contact parameters of particles were calibrated via a series of large-scale triaxial test analyses. The model simulated tunnelling as the TBM operational conditions were controlled. The penetration rate and the rotational speed of the screw conveyor were automatically adjusted as the TBM advanced to prevent the generation of excessive or insufficient torque, thrust force, or chamber pressure. Accordingly, these parameters were maintained consistently around their set operational ranges during excavation. The simulation results show that the proposed numerical model based on DEM–FDM coupling could reasonably simulate EPB driving while considering the TBM operational conditions.

Investigation into the Characteristic of Air Pressure Field in the Melt Blowing with Dual Slots via Numerical Simulation

2012 ◽  
Vol 538-541 ◽  
pp. 804-809 ◽  
Author(s):  
San Fa Xin ◽  
Xin Hou Wang
Keyword(s):  
Numerical Simulation ◽  
Pressure Difference ◽  
Research Method ◽  
Pressure Field ◽  
Three Dimensional ◽  
Air Pressure ◽  
Melt Blowing ◽  
Main Research

The characteristic of air pressure field in melt blowing with dual slots was studied. The main research method was the numerical simulation of three dimensional. The results show that the air pressure field is symmetric. There exist two sections: the pressure difference section and the zero-pressure difference section along the whole centerline. In the pressure difference section, there also exist three sub-sections.

scholarly journals Research on Distribution Properties of Coating Film Thickness from Air Spraying Gun-Based on Numerical Simulation

Coatings ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 721 ◽  
Author(s):  
Xiaopeng Xie ◽  
Yinan Wang
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Film Thickness ◽  
Coating Thickness ◽  
Thickness Distribution ◽  
Air Pressure ◽  
Reasonable Assumption ◽  
Coating Film ◽  
Discrete Phase Model ◽  
Spraying Process

This work aims to study the influence of the spraying parameters on the spray flow field and coating thickness distribution during the air spraying process. The shaping air pressure and the target geometry have an important influence on the distribution of coating film thickness. This paper begins with a 3-D physical model of an air spray gun, in which unstructured grids were generated for control domain. A grid independency study was also carried out to determine the optimal number of cells for the simulations. Then the Euler–Lagrange method was used to describe the two-phase spray flow by establishing a paint deposition model. The numerical simulation based on the discrete phase model (DPM) and TAB model has been carried out. A reasonable assumption was proposed based on the analysis of the spraying process, so that the droplets were injected into the airflow at the position of the paint hole. The influence of the shaping air pressure on the air flow field and the coating thickness distribution was analyzed by changing the shaping air pressure. From the numerical simulation results, it can be concluded that the smaller the shaping air pressure, the more concentrated the coating. With increasing the shaping air pressure, the length of the coating film along z-axis gradually increases, the width along x-axis gradually decreases, and the spray area gradually increases. The paper ends with a numerical simulation and experimental study on planar vertical spraying, planar tilted spraying, and cylinder spraying. Comparisons and experiment results verify the validity and practicability of the model built in this paper.

Temperature-Humidity Coupled Analysis in Battery Pack Based on Airflow Characteristics of Waterproof-breathable Valve

2021 ◽  
pp. 1-13
Author(s):  
Weijian Li ◽  
Fengchong Lan ◽  
Jiqing Chen
Keyword(s):  
Mass Transfer ◽  
Thermal Characteristic ◽  
Transfer Characteristic ◽  
Coupling Model ◽  
Air Pressure ◽  
Battery Pack ◽  
Transfer Model ◽  
Pressure Balance ◽  
Characteristic Analysis ◽  
Mass Transfer Characteristic

Abstract Waterproof breathable valves (WBV) are applied to the battery packs in electric vehicles due to their advantages of high efficiency waterproof and air-pressure balance. With the continuity of mass transfer of WBV and uncertain thermal conditions, the dynamic thermal characteristic of the moisture inside the battery pack is difficult to obtain by experiments, especially the phase change of the moisture. To analyze the temperature-humidity characteristic in the battery pack considering mass transfers of WBV, this study presents a temperature-humidity coupling model of the battery pack based on the mass transfer characteristic of WBV. A mass transfer model of WBV is developed with the airflow mass transfer characteristic in air pressure difference. The proposed models verified the feasibility of dynamic thermal characteristic analysis with experiments. Finally, a practical case study on a battery pack is used to study dynamic characteristics of the temperature-humidity during idle and working. Using the coupling model and the WBV model, temperature-humidity distribution and the location and time attributes of moisture condensation in the battery pack are effectively obtained. The inner walls of the pack casing and the battery surface near WBV are condensation areas during different environmental conditions.

Numerical Simulation and Backfilling Materials Research on Coal Spontaneous Combustion of Thick Seam Large-Scale Top-Caving Region in Resources Conformity Coal Mine

2012 ◽  
Vol 524-527 ◽  
pp. 317-320
Author(s):  
Bo Tan ◽  
Yuan Gang Jiang ◽  
Chao Nan He ◽  
Jing Chang ◽  
Ya Qi Luo
Keyword(s):  
Numerical Simulation ◽  
Process Model ◽  
Large Scale ◽  
Spontaneous Combustion ◽  
Combustion Process ◽  
Fire Control ◽  
Coal Spontaneous Combustion ◽  
Thick Seam ◽  
Materials Research ◽  
And Control

This paper aimed at fire control in thick seam large-scale top-carving region. On the basis of coal and oxygen compounding theory, theoretical analysis, numerical simulation and experiment are combined, and a coal spontaneous combustion process model is built according to fluid mechanics and control theory. By studying and testing on top-carving coal spontaneous combustion process, conclusion is drawn that spontaneous combustion area is the largest in partly-closed region, followed by unclosed region. A totally closed baffle leads to the smallest spontaneous combustion area and the smallest possibility of fire. With local materials in a certain condition, new, cheap backfilling materials are developed. Thus provide theoretical basis for study on the forecasting and prevention of thick seam large-scale top-carving coal spontaneous combustion.

Simulation Study on the Wind Pressure of Village Flat Roof with Parapet Based on Different Wind Angles

2014 ◽  
Vol 638-640 ◽  
pp. 228-232 ◽  
Author(s):  
Jun Liu ◽  
Yuan Quan Yang ◽  
Yan Lei Sun ◽  
Bin He
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Pressure Fluctuation ◽  
Field Measurement ◽  
Pressure Coefficient ◽  
Air Pressure ◽  
Wind Pressure ◽  
Simulation Technology ◽  
Wind Tunnel Tests ◽  
Flat Roof

The main research methods to predict and research wind loads on buildings at home and abroad include wind tunnel tests, field measurement and numerical simulation. However, the wind tunnel tests and field measurement require big funds, long cycle and complicated measurement. Moreover, numerical simulation technology is quite mature. In this paper, based on fluid dynamics software CFD and criteria Reynolds k-ε turbulence model, wind field of the village flat roof with parapet is studied using the numerical simulation technology. Furthermore, the wind pressure data in different wind angles are processed and analyzed. The results show that wind angle has a significant impact on the wind pressure and its distribution. When the wind angle is 0 °, the air pressure-fluctuation in each node of the roof is small, and the pressure coefficient is steady between -1.50 and -2.00. When the wind angle is 45 °, the air pressure fluctuation in each node of the roof is large, and the pressure coefficient fluctuates between -0.8 and -3.0. When the wind angle is 90 °, the wind pressure-fluctuation in each node of the roof is equal to the fluctuation between 0 ° and 45 °wind direction angle, and the wind pressure coefficient fluctuates between -0.7 and -1.7. When incoming flow is along the asymmetric axis, the wind pressure-fluctuation is large, and the wind pressure is greater than that in the large negative pressure zone which is along the symmetry axis, which can bring serious damage on the roof.

scholarly journals A Displacement-Based Theory for Predicting the Support Force on the Shield Tunneling Surface in Sandy Soil Layers

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Guang Sun ◽  
Han Liu ◽  
Zhiyuan Guo ◽  
Ranjie Li ◽  
Tao Li
Keyword(s):  
Numerical Simulation ◽  
Sandy Soil ◽  
Soil Layer ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Shield Tunnel ◽  
Soil Pressure ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Support Force

Due to the poor stability of the loose sandy soil layer, if the support force is not properly controlled during the construction process of the shield tunnel using the earth pressure balance method, it is easy to cause the ground to collapse or uplift. Therefore, understanding the support force of the excavation surface of shield tunneling in sandy soil layer is very vital to ensure the stability of the excavation surface. Firstly, it is assumed that the damaged soil is a three-dimensional wedge and a modified three-dimensional wedge in the active and passive failure modes, respectively. The shallow soil pressure theory and the soil plastic limit equilibrium theory are derived by analyzing the stress distribution on the damaged soil. The equation for revealing the inner essence between the support force of the shield excavation surface and excavation surface displacement under the condition of sand-covered soil is used. Secondly, the numerical simulation method analyzes the displacement of the excavation surface when the support force changes under different working conditions, and the relationship curve between the excavation surface support force and the shield tunneling displacement is obtained. The comparison and analysis between the numerical simulation calculation and the theoretical analysis indicate that the deduced calculation equation for the excavation surface support force based on the displacement earth pressure is reasonable.

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