scholarly journals Study on the Effect of Jet Direction of Compound Air Curtain on Smoke Control

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6983
Author(s):  
Zhiyong Zhou ◽  
Yao Lu ◽  
Yimeng Cui
Keyword(s):  
Working Conditions ◽  
Working Condition ◽  
Simulation Software ◽  
Control Effect ◽  
Smoke Control ◽  
Ansys Fluent ◽  
Air Curtain ◽  
Fire Source ◽  
Smoke Prevention ◽  
Fire Scene

High temperature smoke caused by fire is a major cause of casualties. In order to ensure the safety of personnel, it is very important to control the spread of smoke and enable personnel to quickly withdraw from the fire scene. While traditional hard isolation, such as fire doors, may hinder the safe evacuation of people, the use of an air curtain as a flexible isolation has received more and more attention from researchers. In this paper, the influence of jet direction of compound air curtain on the smoke control effect was studied, and six working conditions were designed. The temperature and smoke isolation of the compound air curtain were numerically simulated by using ANSYS FLUENT software. The parameters such as temperature, velocity pressure and velocity streamline were analyzed, and the smoke control effects of six different jet directions were discussed. The simulation results were verified by Pyrosim fire simulation software simulation software. The results show that the direction of jet flow has a significant influence on the smoke control effect, and the fire smoke control effect under working conditions 4 and 5 is better. The working condition 5 (both air curtain A and air curtain B have outward jet direction) has the best smoke prevention effect, which is suitable for a situation that is close to the fire source. Working condition 4 (outward direction of air curtain A and inward direction of air curtain B) has the second-best effect of smoke prevention, which is suitable for situations far from the fire source.

scholarly journals Numerical simulation on the characteristics of smoke exhaust effect with different sets of smoke vent in deep buried inclined channel fire

2021 ◽  
Vol 252 ◽  
pp. 02050
Author(s):  
Lu Yuhan ◽  
Weng Miao cheng ◽  
Liu Fang
Keyword(s):  
Control Effect ◽  
Smoke Control ◽  
Metro Station ◽  
Thermal Buoyancy ◽  
Average Temperature ◽  
Fire Source ◽  
Smoke Spread ◽  
Fire Smoke ◽  
Fire Characteristics ◽  
Better Than

Deep buried metro stations require longer and more inclined exit passages to connect with the outside. The fire characteristics of these inclined and narrow passages are significantly different from those of above-ground or shallow buried metro station exit passages, and at the same time fires in those inclined channels have a greater risk. This paper takes a channel of deep buried tunnel station in Chongqing as an example and simplifies the actual passage to establish a 3D model to study the smoke spread characteristics along the passage with different smoke vent characteristics including shape and location by FDS, as well as temperature distribution characteristic under different working conditions. The results show that: after a fire, smoke will spread upwards rapidly under the action of thermal buoyancy, and mechanical smoke exhaust plays a certain role in controlling smoke, which is more obvious at the beginning of the fire; there are differences in the smoke exhaust efficiency of different smoke extraction openings shape, but the differences are small, and square smoke vents have a slightly better effect on smoke control than other shapes of smoke vents; changing the location of smoke outlets has a greater impact on the environment in the tunnel. When the smoke vent is located directly above the fire source, the mechanical smoke control effect is significantly better than other positions, and as the distance between smoke vent and fire source increases, the average temperature along the passage increases. At the same time, because of the pressure difference after the fire, the emergency staircase and the upstream of the fire source are basically unaffected by smoke.

scholarly journals Study on Fire Smoke Distribution and Smoke Control in Extra-long Double-hole Tunnel

2020 ◽  
Vol 3 (4) ◽  
pp. p17
Author(s):  
Jingdan Gan ◽  
Feng Shan Wu ◽  
Hong Liu
Keyword(s):  
Simulation Software ◽  
Smoke Control ◽  
Air Curtain ◽  
Tree Analysis ◽  
Fire Smoke ◽  
Operation Period ◽  
The Cross ◽  
Accident Tree

Abstract： Construction of tunnels, as one of the main methods to solve physical traffic barriers, However, It vulnerable to the threat of fire during the process of tunnel operation period. In response to such situation, this article explores the smoke distribution of extra-long double-tube tunnel and its impact on evacuation in the event of a fire. This paper take the Jieling tunnel as an example, and applies Accident Tree Analysis (ATA) method combined with Fires Dynamics Simulator (FDS）simulation software to study the changes of harmful factors such as tunnel smoke. According to the research, when a fire occurs in an extra-long double-tube tunnel, It is concluded that people are supposed to be guided to leave via the nearest cross-passages as soon as possible, In the end analysis the roles that air curtains could play in the control of smoke. It is recommended to open the air curtain so that in such condition people away from the cross-passages have enough time to escape.

Dynamic monitoring feedback iteration control for damping-adjustable semi-active suspension systems

2021 ◽  
pp. 1-9
Author(s):  
Chongchong Li ◽  
Jiangyong Xiong ◽  
Tingshan Liu ◽  
Ziang Zhang
Keyword(s):  
Root Mean Square ◽  
Working Conditions ◽  
Control Algorithm ◽  
Active Suspension ◽  
Dynamic Monitoring ◽  
Iteration Algorithm ◽  
Mean Square ◽  
Control Effect ◽  
Analytic Hierarchy ◽  
Vehicle Simulation

In order to further improve vehicle ride performance, a dynamic monitoring feedback iteration control algorithm is proposed by combining the features of a variable-damping semi-active suspension system and applying them to the system. A seven-degree-of-freedom finished vehicle simulation model is built based on MATLAB/Simulink. The root-mean-square values of the acceleration of the sprung mass, the dynamic travel of the suspension and the dynamic tire load are taken as evaluation indicators of vehicle ride performance. An analytic hierarchy process (AHP) is used to determine the weighting coefficients of the evaluation indicators, and a genetic algorithm is utilized to determine the optimal damping of the suspension under various typical working conditions. Suspension damping is controlled with a dynamic monitoring feedback iteration algorithm. The correction coefficients of the control algorithm are determined according to the deviation between the obtained damping and the optimized damping so that the control parameters will agree with the optimal result under typical working conditions, and the control effect under other working conditions is verified. The simulation results indicate that the proposed dynamic monitoring feedback iteration control algorithm can effectively reduce the root-mean-square value of the acceleration of the sprung mass by 10.56% and the root-mean-square value of the acceleration of the dynamic travel of the suspension by 11.98% under mixed working conditions, thus improving vehicle ride performance. The study in this paper provides a new attempt for damping control of semi-active suspension and lays a theoretical foundation for its application in engineering.

BP-AdaBoost Algorithm Based on Variational Mode Decomposition Optimized by Envelope Entropy for Diagnosing the Working Conditions of a Slideway Seedling-Picking Mechanism

2021 ◽  
Vol 37 (4) ◽  
pp. 665-675
Author(s):  
Zhitao He ◽  
Haiyang Zhang ◽  
Jun Wang ◽  
Xin Jin ◽  
Song Gao ◽  
...  
Keyword(s):  
Empirical Mode Decomposition ◽  
Working Conditions ◽  
Working Condition ◽  
Recognition Accuracy ◽  
Variational Mode Decomposition ◽  
Adaboost Algorithm ◽  
Layer Number ◽  
Entropy Minimization ◽  
Mode Decomposition ◽  
Penalty Factor

Highlights A method of monitoring the working conditions of a slideway seedling-picking mechanism based on variational mode decomposition (VMD), envelope entropy, and energy entropy is proposed. Based on the criterion of envelope entropy minimization, the combination of the decomposition layer number and penalty factor in VMD is optimized to yield a satisfactory decomposition effect of the analyzed vibration signal. The BP-AdaBoost algorithm is used to improve the working condition classification performance for the slideway seedling-picking mechanism. The working-condition identification effect with the proposed method are compared with those through EMD-based, LMD-based, and EEMD-based methods. Abstract . The slideway seedling-picking mechanism is a type of rotating machinery. This study proposes a novel method of identifying the working conditions of slideway seedling-picking mechanisms for early fault diagnosis by utilizing a back-propagation adaptive boosting (BP-AdaBoost) algorithm based on variational mode decomposition (VMD) optimized by the envelope entropy. The experimental results demonstrate that the proposed method can effectively verify the four working conditions (normal state, slideway failure, cam failure, and spring failure). The overall recognition accuracy reaches 90.0% under the optimal combination of the decomposition layer number K and penalty factor a in VMD determined through the envelope entropy minimization criterion. Classification comparisons with empirical mode decomposition (EMD), local mean decomposition (LMD) and ensemble empirical mode decomposition (EEMD) integrated into the BP-AdaBoost algorithm indicate that the overall recognition accuracy of the proposed method is 18.1%, 16.9%, and 15.6% higher than the accuracies of the three conventional methods, respectively. Compared with the K-means, support vector machine (SVM) algorithms, BP-AdaBoost algorithm demonstrates a more dependable capability for identifying the working conditions. This study provides a useful reference for monitoring the working conditions of slideway seedling-picking mechanisms. Keywords: BP-AdaBoost algorithm, Energy entropy, Envelope entropy, Slideway seedling-picking mechanism, Variational mode decomposition, Working conditions.

scholarly journals Tracking control and robustness study of shifting process

2018 ◽  
Vol 46 (2) ◽  
pp. 99-106
Author(s):  
Xin-xin Zhao ◽  
Chao Guan
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Tracking Control ◽  
Pid Controller ◽  
Automatic Transmission ◽  
Good Control ◽  
Simulation Software ◽  
Control Effect ◽  
Engine Torque ◽  
Shift Quality

Heavy dump vehicles are usually working with big load changes and bad work environment, thus change the friction performance of transmission clutches, as well as great affect the shift quality seriously, which influence the vehicle performance. Many researchers developed a lot to design a useful automatic transmission control system. Using PID tracking control and Monte Carlo method, the controller based on an dynamic model was set up to analyze the shifting process of automatic transmission and its robustness in this paper．The shift process was divided into four stages, low-gear phase, torque phase, inertia phase and high-gear phase. The model presents the process from the first gear to the second gear when the torque has big change．Since the jerk and the friction work of clutch are both related to the speed of clutch which was easier to control, it was chose as the target to control the oil pressure for satisfying the requirement of shift quality．The simulation software, Maplesim and Simulink, were used to build the vehicle model and shifting controller for simulation under different working conditions, and the maximum jerk was changed from 34 m/s3 to 12 m/s3 after the optimization. In this paper the Monte Carlo has been used to quantize and evaluate the robustness of the closed-loop system for the friction coefficients and output torque of turbine variation leading by the friction feature parameters and throttle angle changed. Monte Carlo method was used to analyze the effectiveness and robustness of PID controller, which proves that it has good control effect when the throttle is ongoing minor fluctuations. When the throttle is full opening, a quadratic optimal controller based on disturbance is designed by the method of multi-objective optimization. When it changes within 20 percent, PID controller was designed under the guidance of tracking thoughts. The results also show that the controller could still obtain better effect when the friction coefficient ranged from -40 % to 40 % as well as engine torque changed from -20 % to 20 %, which indicates the robustness of controller.

scholarly journals OPTIMIZING THE VELOCITY OF RING SHAPE PARAMETER FOR DESIGNING THE NOZZLES USING CFD

2021 ◽  
pp. 1-10
Author(s):  
Obai Younis ◽  
Reem Ahmed ◽  
Ali Mohammed Hamdan ◽  
Dania Ahmed
Keyword(s):  
Shape Parameter ◽  
Maximum Velocity ◽  
Simulation Software ◽  
Governing Equations ◽  
Ansys Fluent ◽  
Ring Shape ◽  
Ring Location ◽  
Computational Fluid Dynamics Cfd ◽  
Triangular Elements ◽  
Volume Method

This study aims to optimize the velocity of ring shape parameter for designing the nozzles using computational fluid dynamics (CFD) and investigated the flow in nozzles using ANSYS, Inc. simulation software. The model geometries were defined using ANSYS FLUENT-Design Modeler platform. All nozzles were designed on unstructured triangular elements comprising of 1200000 mesh nodes. The differential governing equations were applied in ANSYS FLUENT based on a finite volume method. The distance and dimensions of ring location significantly influence the velocity of water during flow where the maximum velocity at double rings reduces the surface area at distance of 7mm and 15mm and 2x2 mm dimensions. Considering 8, 10, and 12 bar liner proportions, there was an increase in the velocity at maximum points in ring shapes.

scholarly journals CFD investigation on the performance analysis of Tesla turbine

2021 ◽  
Vol 850 (1) ◽  
pp. 012026
Author(s):  
J Kevin Joseph ◽  
R Jeyanthinathan ◽  
R Harish
Keyword(s):  
Power Output ◽  
Cfd Simulation ◽  
Simulation Software ◽  
Working Fluid ◽  
Maintenance Cost ◽  
Ansys Fluent ◽  
Rotating Speed ◽  
Velocity Magnitude ◽  
Turbine Disc ◽  
Improved Performance

Abstract A Tesla turbine is a bladeless turbine in which fluid flows in the direction of the centripetal path. It uses fluid properties such as Boundary layer & adhesion of fluid on a series of discs keyed to a shaft. The initial cost and maintenance cost of the Tesla turbine is very low. Our project’s main motive is to improve the performance of a Tesla turbine by changing various parameters such as disc diameter and disc rotating speed through the CFD simulation software using water as a working fluid. The CAD model is designed using Ansys design modeler, meshing is performed using Ansys meshing and post processing is carried out in Ansys fluent. The numerical simulations were carried out using Ansys Fluent which is based on the finite volume method and the changes that occurred in the pressure and velocities are investigated. The parametric study is performed by varying the turbine disc speed. By performing CFD simulations, total pressure contour and velocity magnitude contours are plotted and it is found that pressure and velocity are maximum when the clearance between disc and turbine casing is lesser and at higher turbine disc speeds. The power output of the Tesla turbine is also plotted for various rpm where higher rpm gives maximum power output. The results from the present study would be useful in designing an efficient Tesla turbine with improved performance.

scholarly journals Impact of Thermal Dissipation on the Lighting Performance and Useful Life of LED Luminaires Applied to Urban Lighting: A Case Study

2022 ◽  
Vol 19 (2) ◽  
pp. 752
Author(s):  
Juan de Dios Unión-Sánchez ◽  
Manuel Jesús Hermoso-Orzáez ◽  
Manuel Jesús Hervás-Pulido ◽  
Blas Ogáyar-Fernández
Keyword(s):  
Thermal Imaging ◽  
Simulation Software ◽  
Thermal Dissipation ◽  
Junction Temperature ◽  
Ansys Fluent ◽  
Imaging Camera ◽  
Fluent Simulation ◽  
Useful Life

Currently, LED technology is an established form of lighting in our cities and homes. Its lighting performance, durability, energy efficiency and light, together with the economic savings that its use implies, are displacing other classic forms of lighting. However, some problems associated with the durability of the equipment related to the problems of thermal dissipation and high temperature have begun to be detected, which end up affecting their luminous intensity and the useful life. There are many studies that show a direct relationship between the low quality of LED lighting and the aging of the equipment or its overheating, observing the depreciation of the intensity of the light and the visual chromaticity performance that can affect the health of users by altering circadian rhythms. On the other hand, the shortened useful life of the luminaires due to thermal stress has a direct impact on the LCA (Life Cycle Analysis) and its environmental impact, which indirectly affects human health. The purpose of this article is to compare the results previously obtained, at different contour temperatures, by theoretical thermal simulation of the 3D model of LED street lighting luminaires through the ANSYS Fluent simulation software. Contrasting these results with the practical results obtained with a thermal imaging camera, the study shows how the phenomenon of thermal dissipation plays a fundamental role in the lighting performance of LED technology. The parameter studied in this work is junction temperature (Tj), and how it can be used to predict the luminous properties in the design phase of luminaires in order to increase their useful life.

scholarly journals CFD-Based Determination of the Optimal Blowing and Suction Air Volume Ratio of Dual-Radial Swirl Shielding Ventilation in a Fully Mechanized Excavation Face

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Kuan Wu ◽  
Shiliang Shi ◽  
Yijie Shi ◽  
Yong Chen
Keyword(s):  
Ventilation System ◽  
Volume Ratio ◽  
Simulation Method ◽  
Dust Concentration ◽  
Dust Control ◽  
Underground Mines ◽  
Physical And Mental Health ◽  
Control Effect ◽  
Air Curtain ◽  
Air Volume

Dust is one of the main pollutants in coal mines, which seriously affects the physical and mental health of workers, as well as the safe production in underground mines. Dual-radial swirl shielding ventilation is a new ventilation method for a fully mechanized excavation face and can effectively reduce the dust concentration in the underground. The dust control effect of dual-radial swirl shielding ventilation is mainly affected by the thickness and integrity of the shielding air curtain, as well as the disturbance of the flow field near the air curtain. By changing the blowing and suction air volume ratio of the air duct, the strength of the radial air curtain can be improved, and the dust control effect of the dual-radial swirl shielding ventilation system can be effectively improved. In order to determine the optimal operating parameters of the dual-radial swirl shielding ventilation system, a numerical simulation method was used to conduct an in-depth study on the blowing and suction air volume ratio of the system. The results showed that when the blowing and suction air volume ratio of the air duct was 1.5, the radial air curtain had the highest strength. Under this condition, the dust concentration at the driver’s position of the roadheader was the lowest, and the dual-radial swirl shielding ventilation system can achieve an ideal dust control effect.

Sign in / Sign up

Export Citation Format

Share Document