Three-dimensional Large Eddy Simulation of Smoke Flow during Indoor Fire

Indoor fires are quite dangerous,claiming many casualties and resulting in great property loss.Using Computational Fluid Dynamics(CFD),a three-dimensional large eddy simulation model of smoke flow is set up.Through the simulation of smoke flow,the theoretical basis is provided for controlling a fire in multiple rooms,thereby saving people.The results of simulation show that high temperatures and thick smoke exist near the fire,and the probability of combusting other tinder will increase.Moreover,there are close relationships between fire and ventilation.The latter can lower the average temperature and speed up the spread of smoke flow and toxic gases,providing conditions for the further development of indoor fire.Moreover,from both the simulated calculation and physical measurement,it is shown that indoor fires and their temperature distribution and smoke concentration are influenced by the fire power and the room size.The results from calculation and measurement are quite consistent.     

Experimental Analysis of Building Space Constructions on Hot smoke Flow in Residential Fire

Based on the characteristics of spatial structure of residential units, the effect of building space construction on temperature raise and hot smoke flow in residential fire was analyzed on building model with simulating multiple floors and rooms. The raise and distribution of temperature indoors were mainly tested under varied location of fire sources. And, the rule of smoke flow was discussed by using the law of temperature raise, indirectly. The results indicate that the mode of smoke flows is influenced by three spatial factors which include the form of junction terminal room construction; the height of down stand above the door and the relative locations of each room. The diffusion of hot smoke is prevented effectively by the down stand of the room; the temperature difference between indoor and outdoor should be higher than that of the room without down stand. When the open direction of door in non fire room is opposite to that of the door in fire room, there is much more hot smoke.     

A Study on Application of Air Pollution Diagnosis and Predict Model to Chongqing Urban

This paper presents results of a research project "The prediction of the Fire Smoke Flow Properties in the Building", supported by the National Natural Science Fund. The numerical model of fire smoke flow in the building and its applied computer software are outlined. The experimental results obtained from full-scale fire test are compared with the results of numerical prediction using computer software.     

Numerical Model of Hot Smoke Flow in Residential Fire

Based on the characteristics of spatial structure of residential units, the law of indoor hot smoke flow was investigated by experimental research on a platform model with multiple floors and rooms in a residential building. Three factors exerting influence on hot smoke flow in residential construction were mainly analyzed, including the relationship between the height of space and the area of single room, the size of doorway opening, and the hub space. Based on basic concepts of thermodynamics and fluid mechanics, the geometric relational model of the height of space and the area of single room impacted on filling speed of hot smoke in room was presented by conservation of mass. Moreover, under the influence of hot smoke flow, the formula of doorway opening size was developed by conservation of momentum. The results show that the fire safety of residential building should take full account of the impact of spatial structural. The indoor temperature distribution and hot smoke flow path will be controlled effectively by the design of single room size and room connectivity.     

Numerical Simulation for Fire Smoke Flow in a High-rise Building with Patio Space

Characteristics of smoke flow and fire spread in a patio space of a high-rise building were studied to investigate their influences on fire compartment and safety evacuation.Fire development model was established and fire scenarios were designed to simulate fire and smoke spread by CFD software numerically based on concepts of fire performance-based design in a high-rise building with double patio space,whose height are 74.65 m and 55.95 m,respectively.Simulation results show that in all fire scenarios,performance targets for safety evacuation for people in each floor was satisfied,if smoke was extracted naturally using the patio space.Hang walls mounted in corridors around the patio space prevent smoke flowing out smoothly,shorten the coming of the risk time and increase fire danger.Using chimney effect,it is preferred to adopt natural smoke exhaust method in a high-rise building with patio space.     

Thermal Radiation Effects on Smoke-flow in Atrium Fires

The field models for smoke flow in atrium, takings into account strong buoyancy, turbulence, radiation exchange and wall heat losses are developed according to the characteristics of the atrium fire. Realistic combustion processes in the burning fuel have not been included. A six-flux radiation model is included in a general mathematical model for fires, which are taking as a volumetric heat source, It is applied to the predictions of fire smoke development in a small-scale atrium. In order to avoid complicated radiation exchange models, radiation heat loss effects are combined to the wall heat loss. A General-purpose compute program PHOENICS has been developed to meet this need. Results of numerical calculations based on the field model are compared with test data for a fire in the small-scale atrium test facility. The resullts indicate that radiation transfer has the minor effects, due to the relatively low temperatures encountered. The method that the effect of radiation is included in the calculation of wall heat transfer losses by using maximum heat transfer coefficient is feasible. The field model used in the present study is not good enough, which a turbulent combustion sub-model must be included.     

Analysis of Fire Smoke Movement with Different Air Velocity at the Stair head to the Hall of a Metro Station

When a fire happens at the subway platform, the downward ventilation at the staircase which connects the hall and platform can prevent smoke spreading into the hall and provides guiding air for evacuation people. To investigate the influence of the ventilation rate on the smoke movement, the air velocity at the staircase was measured under three ventilation modes. Numerical model was established to simulate the real fire scenario. It is shown that the downward air velocity under fire is greater than that without fire, and the traditional design procedure without considering complex factors interaction in real fire scenario should be improved; when fire is near the staircase, smoke easily spills from the smoke screen to the concourse. And smoke concentration of concourse is even higher than that of platform because the hall is under air supply mode; when the fire locates at the public area of the platform, turning on the tunnel fans can increase the downside flow at the staircase. However exceeding high flow can produce disturbance and destroy the smoke stratification, so more area will be filled with smoke. Therefore, reasonable smoke management scheme is as important as smoke exhausting system capability.     

Analysis of Yangtze River Water as a Potential Source for Developing a Water Source Heat Pump in Chongqing

Characteristics of smoke flow and fire spread in a patio space of a high-rise building were studied to investigate their influences on fire compartment and safety evacuation. Fire development model was established and fire scenarios were designed to simulate fire and smoke spread by CFD software numerically based on concepts of fire performance-based design in a high-rise building with double patio space, whose height are 74. 65 m and 55. 95 m, respectively. Simulation results show that in all fire scenarios, performance targets for safety evacuation for people in each floor was satisfied, if smoke was extracted naturally using the patio space. Hang walls mounted in corridors around the patio space prevent smoke flowing out smoothly, shorten the coming of the risk time and increase fire danger. Using chimney effect, it is preferred to adopt natural smoke exhaust method in a high rise building with patio space.     

Hybrid field network simulation of temperature in a building fire

A connecting platform between the field model and network model has been constructed, based on a multi functional building model. The field model is used to simulate the fire smoke in certain special compartments (the fire room and specific large space rooms), while the network model is used to simulate the uniform compartments. When combining the simulation results of the field model and network model as the interface boundary conditions for the each other, a hybrid field and network model is presented. The hybrid field network model can provide more detailed physical information of the fire smoke properties under a specific fire scenario for the specially confined compartments. In addition, the hybrid model can predict the fire smoke flow properties in the building accurately.     

Example Verification and Experimental Study of Network Model for Room Temperature Prediction during the Fire in Buildings

The network model for room temperature and its implicit differential equation are discussed in this paper. The example verification and experimental study were carried out for the prediction of the room temperature in the software of predicting the properties of smoke flow. The results show that the results of example computation are similar to those obtained by similar software in Japan. The results of computation by the software tally with the experimental ones and accord with the law of development and change of room temperature during the fire.     

Optimization Model of Non-rhythm Flow Process and the Dynamic Programming Algorithm

The flowing sequence has important effect to the flow ste Pdistance and the period of non-rhythm flowing construction,algorithmic research of ordering and step distance calculation are always difficult point of non-rhythm flowing construction optimizes studying.An optimization model of non-rhythm flow process is founded,and a common method for confirming the length of flow step was put forward.In order to find the solution of the optimization model conveniently,the optimization problem is transformed to shortest path problem skillfully.A dynamic programming algorithm is given to make the construction project period as shorter as possible,to reduce cost and improve economic efficiency.     

Discussion on Direction of Circular Flow of Reversed Return Hot Water System

Aiming at the central mechanical circulated hot water supply system recommended by the current code, the criteria of water flow direction in the pipes of transport and distribution is brought forward based on the hydraulic principle, followed by the analysing with charts of flow directions in the reversed return hot water system consisting of two, three and several vertical pipes in the working conditions of simple return and a little water distributing. There are several directions of circular flow, the only working condition of simple return and single water flow direction which applied in current hydraulic calculation of reversed return hot water supply system is incomplete, certain hydraulic precondition is necessary to ensure circular flow flowing in each vertical pipe as the assumed direction in the course of hydraulic calculation.     

Average Temperature Distribution of the Ceiling Jet in Train Fires in Tunnels

The flame ceiling jet is easily formed while the on fire train stops in the tunnel. The iterative formula is derived to calculate the average temperature of the flame ceiling jet when the fire source is set on the center of the train by establishing a one dimensional model of the unit control volume, and the heat exchange is considered among the flame smoke and the wall of the tunnel and the train. Undetermined coefficients in the iterative formula are determined by small scale model experiments with the scale factor of 1:8 and numerical simulation. The calculated values of temperature by the iterative formula are consistent well with the measured values, and the maximum error of calculation is no more than 7%, which indicates that the iterative formula is reliable. The results show that the distributions of the average temperature of flame ceiling jet are in the exponential form, but there are some differences between that above the train and that in the tunnel. Two prediction formulas for the flame ceiling jet average temperature changing along the longitudinal tunnel are obtained by the sub fitting method. The results can provide reference for the alarm parameter selection, device settings in tunnel, safety evacuation of the passenger, as well as the analysis of the destructive effects on the tunnel lining structure caused by tunnel fire.     

食品行业粉体材料流动性研究的新仪器——PFT

奶粉、面粉、糖、盐、调味品等原料和添加剂粉体的流动性研究是目前很多材料行业的难点,现有常见的一些方法不能满足实际的需求。简单介绍了Brookfield公司根据ASTM D 6128推出的PFT粉体流体测试仪的基本功能,介绍了粉体流动函数、壁面摩擦、松装密度、时间固结、拱架、鼠孔、料斗半角的测量和计算。     

Discussion on the Characteristics of Smoke Movement and Smoke Control Methods in a Shaft of High-Rise Building

Characteristics of smoke movement and smoke control in a shaft is a serious issue that closely related to the fire safety of high-rise building. This paper talks about the studies on the characteristics of smoke movement in a shaft of high-rise building from three aspects: the factors which influence smoke movement in a shaft, the distribution of smoke parameters and the upward velocity of smoke flow. Smoke control methods which are commonly used and the problems in engineering practice are summarized. Some methods thoughts are given to improve the efficiency of smoke control.     

一维稳态流非饱和土渗透系数垂直分布模型及其线性简化

渗透系数是控制地下水流动的重要参数,对渗透系数的空间分布规律进行研究具有重要的意义。基于Gardner模型获取了一维稳态流非饱和土渗透系数沿垂直分布模型,该模型用指数函数描述,受饱和渗透系数和无量纲的深度与流动率等因素的控制;该模型表明一维稳态流条件下均质典型土类的渗透系数其沿垂直方向变化趋势主要受比流量与饱和渗流系数的负数值二者之间的相对大小影响。分别采用泰勒级数方法和以地下水位处及地表处的渗透系数作为控制条件方法对一维稳态流非饱和土渗透系数沿垂直分布模型进行线性近似简化。采用泰勒级数方法获取的简化模型其计算误差随无量纲的深度增大而增大。简化后的模型具有形式简单、参数少等特点。通过算例对比简化模型与原模型的差异,计算结果表明:采用以地下水位处及地表处的渗透系数作为控制条件的方法进行线性近似简化的模型计算误差比采用泰勒级数方法获得的线性近似简化模型的计算误差小。     

T型斜叶桨作用下油辣椒多相流数值分析

利用Fluent仿真软件，以辣椒颗粒、肉丁和豆油构成的多相混合流体为研究对象，结合Eulerian多相流模型，研究了T型斜叶桨和开启式斜叶桨作用下的速度场、密度场、各相体积分数分布及功率消耗状况。结果表明：当转速为6 rad/s时，在T型斜叶桨作用下，虽然功耗有所增加，但混合物的整体流动速度提高，絮流强度增加，料槽底部高密度区域得到改善；各单相体积分数分布与初始设定值较为接近，可实现油辣椒的均匀化混合。计算结果为油辣椒搅拌机理研究提供一定理论参考。     

Research on the Law of Highway Debris Flow Moving in Control Structures

Debris flow is a kind of typical water ruins to highways, and it is a dynamic load for highway water ruin. The authors, following the moving law of debris flow and characteristics of highway ruin, put forward reasonable section shape of high - speed drainage trough. Then, according to the energy conservation principle and horizontal throwing theory, the authors established a calculation formula for the throwing distance. The results of the calculation formula given in this paper offer a solution for load calculation and control effect evaluation problems and provide theoretical foundation i to structure design and disease control of debris flow along the highways.     

Axial Force in Restrained RC Columns during Heating and Cooling Phases

Using the computer program of SAFIR, the influences of some parameters (i.e., axial/rotational restraint ratio, sectional dimension, load ratio, load eccentricity ratio, reinforcement ratio, and heating time, etc.) were analyzed on axial forces in restrained concrete columns exposed to ISO834 standard fire with cooling phase, compared with those in the standard fire without cooling phase.Based on the simulation results of 2880 cases, a practical calculation method for axial force in column was proposed.It was shown that: (a) for axially and rotationally restrained columns in fire with or without cooling phase, the enhancement coefficient of axial force increased gradually first, and then reduced gently or kept constant, and finally decreased quickly.However, in the late stage, the enhancement coefficient corresponding to fire without cooling phase dropped more significant than that with cooling phase; and (b) the influences of the rotational restraint ratio, column length and thickness of concrete cover on the enhancement coefficient of axial force in axially and rotationally restrained columns were limited subjected to fire with cooling phase, while the peak value of the enhancement coefficient increased with the increase of the axial restraint ratio, load eccentricity ratio and reinforcement ratio or with the decrease of the load ratio and sectional dimension.     

Three Phase Harmonic Power Flow Using PhaseComponent for Asymmetric Network

With the increasement of the harmonic quantity in power system ,single phase harmonic power flow calculation can't meet the needs. This paper discusses the components model in detail under harmonic condition in three phase distribution power system, include generator,transformer,line and load. Particularly, the transformer model considers the winding connection, the phase shifting among primary and secondary windings, and the off-normal tapping.The three-phase model of transformer, used in traditional harmonic power flow, may the preuent the model from converging, so the paper proposes a three phase back forward sweep harmonic load flow algorithm based on phase-components. At last, a test example was used to prove the algorithm. The results indicate that the proposed method is efficient.