Numerical Simulation of Airflow Organization Process during Double Highway Tunnel Fire

2014 ◽  
Vol 501-504 ◽  
pp. 2370-2376
Author(s):  
Hai Yan Wang ◽  
Mei Zhen Chen ◽  
Guo Fa Liu
Keyword(s):  
Pressure Field ◽  
Air Flow ◽  
Concentration Field ◽  
Key Technology ◽  
Tunnel Fire ◽  
Highway Tunnel ◽  
Organization Process ◽  
In Fire ◽  
The Mathematical Model ◽  
And Diffusion

Taking Majiazhai double highway tunnel as a prototype, the mathematical model of double tunnel fire is established to analyze smoke plume spread and diffusion during air flow organization process of highway tunnel fire. In the conditions of double tunnel fire jet fans closed, tunnel jet fans open, ventilators of tunnel and cross-road open simultaneously, the temperature field, pressure field and concentration field of air flow and smoke relative motion are obtained. Then it puts forward that the key technology for smoke countercurrent control in double tunnel fire is to increase the ventilation resistance in fire source upwind cross-road and reduce the air quantity flowing from tunnel jet fans into cross-road.

scholarly journals A Study on the Effect of O2 Diffusion on the Retention Time of Inert Agents

2020 ◽  
Vol 10 (19) ◽  
pp. 6694
Author(s):  
GoonHo Kim ◽  
Ju-Hong Cha ◽  
Jee-Hun Jeong ◽  
Ho-Jun Lee
Keyword(s):  
Theoretical Model ◽  
Retention Time ◽  
Hold Time ◽  
Theoretical Models ◽  
Accurate Model ◽  
Fire Extinguishing ◽  
A Value ◽  
O2 Diffusion ◽  
In Fire ◽  
And Diffusion

Gaseous agents are widely used in fire extinguishing systems (FESs) when water extinguishing agents are unavailable. The extinguishing ability of the FES-gaseous agent is determined by the retention time (hold time) at which its concentration is maintained. In particular, the retention time of the inert agent is determined by the O2 inflow from the outside. However, current theoretical models for inert agents do not provide an accurate model for the diffusion of incoming O2. Specifically, because the theoretical equations do not include O2 diffusion or include too large a value, there is a large difference between the measured and theoretical retention times. Therefore, in this study, accurate O2 diffusion was verified through experimental and numerical analyses using three types of deactivators and reflected in the existing theoretical model. O2 diffusion was analyzed through the interface slope α and diffusion velocity vd. As a result, this proposed method can predict the retention time more accurately than existing theoretical models.

Buffer Groove Design of Continuous Rotary Electro-Hydraulic Servo Motor Used in Simulator

2010 ◽  
Vol 37-38 ◽  
pp. 234-237
Author(s):  
Xiao Jing Wang ◽  
Jun Peng Shao ◽  
Guang Bin Yu
Keyword(s):  
Mathematical Model ◽  
Pressure Gradient ◽  
Experimental Research ◽  
Pressure Field ◽  
Structure Design ◽  
Cavity Pressure ◽  
Servo Motor ◽  
Pressure Impact ◽  
Hydraulic Servo ◽  
The Mathematical Model

In order to improve the low speed stationary of continuous rotary electro-hydraulic servo motor and avoid the pressure impact in the sealed cavity during the oil distributing, this paper designed the shape of buffer groove, established the mathematical model of pressure gradient, and analyzed change law of sealed cavity pressure gradient under different dimension of buffer groove. The pressure field distribution of sealed cavity was studied in certain radial and axial gap, and it is validated the dimension of buffer groove is rational, which lays foundation for structure design and experimental research of large displacement servo motor.

scholarly journals The role of acoustics in flame/vortex interactions

1993 ◽  
Vol 254 ◽  
pp. 579-603 ◽  
Author(s):  
T. L. Jackson ◽  
Michéle G. Macaraeg ◽  
M. Y. Hussaini
Keyword(s):  
Initial Temperature ◽  
Pressure Field ◽  
Ignition Time ◽  
Flame Structure ◽  
Time Varying ◽  
Vortex Interactions ◽  
Main Emphasis ◽  
One Step ◽  
And Diffusion

The role of acoustics in flame/vortex interactions is examined via asymptotic analysis and numerical simulation. The model consists of a one-step, irreversible Arrhenius reaction between initially unmixed species occupying adjacent half-planes which are allowed to mix and react by convection and diffusion in the presence of an acoustic field or a time-varying pressure field of small amplitude. The main emphasis is on the influence of the acoustics on the ignition time and flame structure as a function of vortex Reynolds number and initial temperature differences of the reactants.

NEW AUTOMATIC IMPULSE EXTINGUISHING DEVICE

Transport ◽  
2008 ◽  
Vol 23 (2) ◽  
pp. 124-128
Author(s):  
Vladimiras Suslavičius ◽  
Marijonas Bogdevičius
Keyword(s):  
Hydraulic System ◽  
Water Surface ◽  
Hyperbolic Type ◽  
System Of Equations ◽  
Water Surface Area ◽  
Characteristics Method ◽  
Hydrodynamic Processes ◽  
Atomize Water ◽  
In Fire ◽  
The Mathematical Model

A simple way to increase the extinguishing water surface area is to atomize water into fine drops. The smaller drops are developed, the better use of water properties can be implemented and less water is consumed in fire fighting. The automatic impulse extinguishing is created. The main aim of the investigation is to develop the approach to investigate the dynamic and hydrodynamic processes in the extinguishing device. The mathematical model of the extinguishing device is presented, where the flow of liquid and gas and the interaction of liquid with the gas are taken into account. The flow of fluids in a hydraulic system is described by a system of equations of a hyperbolic type, which is solved by a characteristics method. An instance of the mathematical simulation of the activity of extinguishing device is shown.

scholarly journals Two dimensional temperature distribution model in human dermal region exposed at low ambient temperatures with air flow

2013 ◽  
Vol 8 (2) ◽  
pp. 11-24 ◽  
Author(s):  
DB Gurung
Keyword(s):  
Subcutaneous Tissue ◽  
Air Flow ◽  
Static Condition ◽  
Skin Surface ◽  
Distribution Model ◽  
Two Dimensional ◽  
Ambient Temperatures ◽  
Insensible Perspiration ◽  
Engineering And Technology ◽  
The Mathematical Model

This paper deals with thermo-regulation in human dermal part in a cold atmosphere with significant air flow. The mathematical model involving bio-heat equation has been solved using finite element method and Crank-Nicolson technique to numerically investigate two dimensional temperature distributions. The natural three layers of dermal part – epidermis, dermis, and subcutaneous tissue are considered for the study. The important parameters like blood mass flow rate, metabolic heat generation rate and thermal conductivity are taken distinct in each layer according to their distinct sub-regional activities. The human subject is assumed in static condition. The wind speed is considered in the range from the start of forced convection (? 0.2 m/s) and up to 5 m/s. The loss of heat from the skin surface to the environment is taken due to convection, radiation, and insensible perspiration. Kathmandu University Journal of Science, Engineering and Technology Vol. 8, No. II, December, 2012, 11-24 DOI: http://dx.doi.org/10.3126/kuset.v8i2.7320

Turbulent Pressure-Velocity Measurements in a Fully Developed Concentric Annular Air Flow

1983 ◽  
Vol 105 (3) ◽  
pp. 345-354 ◽  
Author(s):  
R. J. Wilson ◽  
B. G. Jones
Keyword(s):  
Velocity Field ◽  
Pressure Field ◽  
Air Flow ◽  
Pressure Fluctuations ◽  
Core Region ◽  
Flow Channel ◽  
Wall Pressure ◽  
Analysis Method ◽  
Local Pressure ◽  
Wall Pressure Fluctuations

An experimental study of the fluctuating velocity field and the fluctuating static wall pressure in an annular turbulent air flow system with a radius ratio of 4.314 has been conducted. The study included direct measurements of the mean velocity profile, turbulent velocity field and fluctuating static wall pressure from which the statistical values of the turbulent intensity levels, power spectral densities of the turbulent quantities, and the cross-correlation between the fluctuating static wall pressure and the fluctuating velocity field in the core region of the flow were obtained. The effect of the turbulent core region of the flow on the wall pressure fluctuations was studied by cross-correlating the axial and radial velocity components with the wall pressure fluctuations. A three-sensor, signal subtraction data analysis method using coherence techniques was developed to separate the superimposed local pressure fluctuations and acoustically transmitted noise. This analysis method is shown to adequately isolate the local pressure fluctuation information at each wall of the flow channel. The results of the experimental measurements are compared with existing experimental and numerical information on turbulent annular flow fields and wall pressure statistics. The pressure-velocity correlation indicates that a substantial contribution to the pressure field on the wall of the flow channel is from the turbulent core region outside of the boundary layer. The wall pressure field is shown to be significantly different on the two dissimilar walls. The pressure-velocity correlations show that this difference is due to the geometric difference between the dissimilar volumetric sources which contribute to the wall pressure field. The results of this study show that vibration modeling must incorporate the effects of the flow geometry on the wall pressure statistics, which are used as the driving force for flow-induced vibrations.

Air Flow in Yarn Texturing Nozzles

1987 ◽  
Vol 109 (3) ◽  
pp. 197-202 ◽  
Author(s):  
M. Acar ◽  
R. K. Turton ◽  
G. R. Wray
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Experimental Work ◽  
Air Flow ◽  
Air Jet ◽  
Continuous Filament ◽  
The Mathematical Model ◽  
Experimental Nozzle ◽  
Good Agreement

The air-jet texturing process, a purely mechanical means of texturing continuous filament yarns, is described. Industrial texturing nozzles are reviewed and categorized in two groups, either as converging-diverging or cylindrical type nozzles. A mathematical model is developed for the complex airflow in cylindrical type texturing nozzles, and experimental data obtained from various nozzles verify the flow predicted by this model. The mathematical model is also shown to be in good agreement with the data obtained from a modified experimental nozzle, which has a trumpet shaped diverging exit. Further experimental work with a scaled-up model of a typical industrial texturing nozzle is also reported.

Key Technology of Form Grinding Wheel’s Axis Section’s Derivation

2013 ◽  
Vol 753-755 ◽  
pp. 1557-1561
Author(s):  
Ling Zhang ◽  
Bin Yao ◽  
Zhi Huang Shen ◽  
Wen Chang Zhao ◽  
Bin Zhou
Keyword(s):  
Research Method ◽  
Screw Compressor ◽  
Grinding Wheels ◽  
Relevant Research ◽  
Key Technology ◽  
Form Grinding ◽  
Key Technologies ◽  
Twin Screw ◽  
Screw Rotors ◽  
The Mathematical Model

Upon researching on the form grinding principle of rotor of the twin-screw compressor, firstly, this article gives the mathematical model of acquiring form grinding wheels axis section from screw rotors end section which is given by a series of discrete points. Then some key technologies to solve problems during the derivation of grinding wheels axis section and relevant research method to optimize the best setting angle have been analyzed. And last, the results of simulation and actual processing prove that this method is reliable and can meet the requirements of machining precision.

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