列车运动对地铁站台环境影响的数值模拟

利用计算流体力学(CFD)方法,对地铁岛式站台在不开启机械通风系统的情况下,单列车进站、停车及出站过程中流场和温度场分布进行了三维数值模拟。模拟结果量化了在列车通过的过程中,站台靠近轨道一侧所形成的较大风速和温升,以及这种影响在站台中部区域的衰减,现场实验说明了模拟结果具有可靠性。根据模拟结果,分析了列车运动过程所造成的活塞风以及列车散热对站台乘客候车环境的影响。采用的三维非稳态模拟方法,使得模拟更加接近于真实的物理过程,模拟结果对于地铁环控系统的设计具有指导意义。     

A computational analysis of the train-wind to identify the best position for the air-curtain installation

This study focuses on computational analysis for the improvement of the tunnel ventilation and the environmental control system of the subway by solving Reynold-averaged Navier-Stokes equations for train-induced unsteady flow. The two-equation turbulence model can predict velocity and pressure field at the tunnel. The sharp interface method is used for the moving boundary of an immersed solid. The flow rate through the natural ventilation-shaft and the features of the train-wind in the subway tunnel help to find better installation locations for the air-curtain. The air-curtain separates two adjacent environments and reduces the transfers of bacteria and radioactive particles. The ANSYS CFX software is used to perform unsteady computations of the flow field at the subway tunnel.     

北京新建地铁通风空调系统模拟分析

本研究以北京新建地铁四号线第三标段隧道和车站为对象,借助SES软件,建立数学模型,对两种典型的通风空调系统方案正常工况运行进行数值模拟。分析得出产热量的分布规律;列车行车状况、活塞风井、不同形式车站及区间隧道通风空调系统对隧道内速度场、温度场及新风量的影响规律。研究同时对通风空调系统方案进行了初步的技术经济比较。本研究为分析地铁通风空调系统的空气流动与传热提供了参考,为新建地铁通风空调系统方案的选择、设计及科学地运行管理提供有价值的数据资料。     

干混砂浆混合过程的有限元模拟分析

基于ANSYS CFX软件,利用多重参考系和RNGk-ε两方程湍流模型对干混砂浆混合设备内的流场进行有限元建模.在此基础上,对物料混合过程进行有限元模拟分析,获得物料混合的速度场、湍动能场以及体积分数变化规律,并通过试验对模拟结果进行验证.结果表明,有限元模拟结果与试验结果一致.     

CFD simulations of gas dispersion around high-rise building in non-isothermal boundary layer

Urban heat island phenomena and air pollution become serious problems in weak wind regions such as behind buildings and within street canyons, where buoyancy effect cannot be neglected. In order to apply CFD techniques for estimation of ventilation and thermal and pollutant dispersion in urban areas, it is important to assess the performance of turbulence models adopted to simulate these phenomena. As the first step of this study, we carried out wind tunnel experiments and CFD simulations of gas and thermal dispersion behind a high-rise building in an unstable non-isothermal turbulent flow. The standard k-ε model and a two-equation heat-transfer model as RANS models, and LES, were used for the CFD simulation. One of the important purposes of this study was to clarify the effect of inflow turbulence (both velocity and temperature) on flow field and gas/thermal dispersion for the LES calculation. Thus, LES calculations with/without inflow turbulence were conducted. The inflow turbulence was generated through a separate precursor simulation. The calculated results showed that both RANS models overestimated the size of the recirculation region behind the building and underestimated the lateral dispersion of the gas. Turbulent flow structures of LES with and without inflow turbulence were completely different. The LES result with inflow turbulence achieved better agreement with the experiment.     

Numerical study on the optimization of smoke ventilation mode at the conjunction area between tunnel track and platform in emergency of a train fire at subway station

To cope with fires in a subway station, ventilation systems are usually installed, which includes an air supply system and a smoke exhaust system. In case of a train fire, the operation of these ventilation systems needs to be studied in order to get optimal control of smoke propagation and provide better environmental conditions for personnel evacuation. In this paper, CFD simulations are carried out by Fire Dynamics Simulator (FDS) to study the effectiveness of different ventilation modes in case of a train fire in a subway station. The temperature and visibility contours are computed as to compare the performance of various ventilation modes for subway stations with full-seal Platform Screen Door (PSD) or half-height safety door. Results show that appropriate activation of the air supply system can improve the efficiency of the ventilation system in smoke control, and vice versa. It is better to activate the lobby air supply system and meanwhile close the platform air supply system. As for the exhaust system, it is necessary to activate the platform exhaust system and the Over Track Exhaust (OTE) system, and it is better to deactivate the Under Platform Exhaust (UPE) system. The optimization strategy of the ventilation mode for subway stations with full-seal PSD is similar to that for subway stations with half-height safety door. With the help of the additional smoke barrier, smoke propagation in a subway station can be well controlled. The results in the paper may serve as a useful reference for the smoke control design in case of subway train fires.     

岛式双层地铁车站热环境优化分析

结合一典型双层岛式地铁车站,分析人流变化对室内环境的影响,发现站台环境能较好地响应人流变化。当送风量变小时,站台热环境仍能满足要求,但其空气品质有所下降;站厅由于空间大,当送风量减小时室内空气掺混不足,部分区域温度升高,会加剧室内环境的不均匀性。     

Optimization of emergency ventilation mode for a train on fire stopping beside platform of a metro station

This paper presents a computational fluid dynamics (CFD) simulation investigation of most effective cooperative operation mode of the tunnel rail track area exhaust system and the platform ventilation system for the emergency scenario of a train on fire stopping beside the platform of a subway station. CFD simulations are carried out by fire dynamics simulator (FDS) to analyse and compare the computed field distributions of smoke temperature and visibility, as to find out the most optimal cooperation mode of these ventilation systems. Results show that only starting the over track exhaust (OTE) system can control the smoke more effectively than starting both the OTE system and the under platform exhaust (UPE) system at the same time. In addition, setting the platform ventilation system as exhaust pattern can provide better control performance than setting it as air supply pattern, in counteracting the smoke flowed into the platform from the fire train. Therefore, it is found out and suggested that in such an emergency condition, the most effective strategic cooperative ventilation mode is only starting the OTE system of the tunnel rail track area with the aid of activation the smoke exhaust pattern of the platform ventilation system.     

地铁站台气流状况现场测试及CFD模拟

地铁站台的气流流动属湍流流动,采用CFD对站台通风方式进行模拟时需要确定相关的边界条件和适用的湍流模型。通过对既有地铁站台气流状况的现场测试,获得了有参考价值的数据;建立了CFD模型。CFD模拟结果与测试数据的比较表明,所选的湍流模型能正确模拟复杂的站台气流流动。     

不同人体座位模型对大空间空气分布影响

本文对座椅送风系统的气流组织进行模拟研究,首先运用座椅送风的简化模型,模拟了人体座椅实体的简化模型和虚区域热源模型下气流组织的情况,分析了两种情况的温度场,速度场和相对湿度场,发现人体座椅实体模型模拟的剧院气流组织速度、湿度与温度分布分层更加明显,此特点更易于微气候的分区控制,用更少的能量达到人体舒适的满意度。该研究为大空间建筑空调系统优化设计、模拟气流组织提供了方法及理论依据,同时对研究空气分布对空调系统的舒适性和节能方面的影响有一定的帮助作用。     

地铁变风量环控系统全年运行方案研究

通过对地铁车站公共区的热负荷进行分析计算,确定了远期地铁车站公共区逐时通风量,结合天津市地铁1号线环控系统的设计方案,提出了空调风机全年变频运行,并用计算流体力学(CFD)模拟的方法,借助Airpak软件,模拟夏季车站变风量运行时车站公共区的温度场和速度场,得出变风量运行后能够达到的设计要求。     

Single-sided ventilation — Part I. The flow between a cavity and external air stream

This paper considers in detail particular flows of the kind which give rise to single-sided ventilation. It presents an experimental study of turbulent flow in a square cavity, with particular reference to the shear layer between cavity and external flows. Hot-wire measurements were carried out in a cubical cavity placed beneath the floor of the test section of the boundary-layer tunnel. Results are presented for zero, positive and negative external pressure gradients, and include time-mean velocity, as well as turbulence intensities, kinetic energy, and shear stress. Flow visualization conducted in a smoke tunnel reveals the behaviour in the shear layer and within the cavity. Predictions of two-dimensional flow fields have been undertaken using a finite-difference scheme and a two-equation model of turbulence. Comparisons with measurements show good agreement in regions where the comparison is valid, and reference to the flow-visualization studies reveals that the essential features of the entire flow field are reproduced by the analytical model.     

地铁列车区间隧道着火时行车安全性的讨论

当地铁列车在区间隧道内发生火灾时,现行的关于地铁列车区间隧道着火时的应急对策是:如果列车的条件允许,尽量驶到下一个车站,利用前方车站疏散乘客.本研究运用计算流体力学(CFD)的方法,对运行中地铁列车周围不同部位的相对风速及其速度场分布特性进行了模拟分析;重点讨论了当地铁列车区间隧道着火时,考虑到风助火势的影响,行进中地铁列车的行驶速度对火势蔓延的影响;进而对地铁列车区间隧道着火时的安全行驶速度进行了初步的探讨.     

剧场座椅送风气流组织数值模拟

座椅送风是置换通风的一种具体形式,不同于传统置换通风的侧送风形式,我国在这方面设计规范也相应较少,又鉴于座椅送风初投资昂贵,在设计时有必要对其气流组织、舒适性等加以模拟预测。本文采用FLUENT软件对其空调系统的气流组织进行模拟研究,运用座椅送风的简化模型,模拟各种送风形式下的温度场和速度场,对比了各种送风形式的温度、速度、风量等因素,为大空间建筑空调系统优化设计、模拟气流组织提供了方法及理论依据。     

地铁岛式站台空调气流CFD模拟

为给岛式站台的气流组织设计提供依据,评价气流组织设计方案,确定合适的送风温差以优化岛式站台空调系统的设计。建立典型岛式站台的三维几何模型,应用标准湍流模型作为站台气流的物理模型,根据实际测试的站台热湿负荷设定数值模拟的边界条件,应用CFD（计算流体力学）对地铁岛式站台空调系统进行模拟。岛式站台的温度场模拟结果与实际测试的站台温度场吻合较好,表明在合理的简化条件下,采用标准湍流模型的计算流体力学模拟能够较为准确地模拟和预测地铁岛式站台的温度场,可以为岛式站台空调系统的气流组织设计提供依据。     

Numerical analysis of tunnel thermal plume control using longitudinal ventilation

A CFD model of the 4th Beijing subway line was used to study the effect of longitudinal ventilation on heat and smoke plume movement in the tunnel. The critical ventilation velocity is correlated with the heat release rate for both a simplified heat fire source model and a complete combustion fire source model with methane gas as fuel. The influences of the heat source length and the fuel gas inlet geometry on the critical velocity are investigated for both fire source models. The results show that the influences of the combustion process and fire source area variation are not included in models based on Froude number preservation theory. Thus, Ri is no longer suitable as a dimensionless number for the critical ventilation velocity when the fire geometry or combustion conditions influence the results. The back-layering air temperature above the front of the fire source can be used to explain the different critical velocity variation regimes for all the simulation conditions.     

Effects of vent shaft location on the ventilation performance in a subway tunnel

A computational analysis of a ventilation system in a subway tunnel is carried out by solving 3D Reynolds-averaged Navier–Stokes equations for train-induced unsteady flow using the sharp interface method as the model for the moving boundary of an immersed solid. The ventilation performance is evaluated depending on the location of the vent shaft by analyzing the ventilating flow rate through the shaft and the feature of the flow field in the subway tunnel around the shaft. It is found that the optimum location of the vent shaft with respect to maximizing ventilation performance lies near the station.     

Experimental and numerical study of a full scale ventilated enclosure: Comparison of four two equations closure turbulence models

Full-scale experimental and computational fluid dynamics (CFD) methods are used to investigate the velocity and temperature fields in a mechanically ventilated enclosure. Detailed airflow fields are measured in three cases of ventilation air temperature: an isothermal case, a hot case and a cold case. The ventilation system creates an axisymmetric jet which is developing near the ceiling. The experimental data are used to test four two equations turbulence models: a k–ε realizable model, a k–ε RNG model, a k–ω model and a k–ω SST model. It is found that, even if the models can predict reasonably the hot and isothermal cases global values of temperature and velocity, none of the models is reliable concerning the cold case. Moreover, a detailed analysis of the jet shows that none of the models is able to predict the exact experimental velocity and temperature fields.     

浅谈地铁车站通风空调系统设计的几个方面

针对地铁车站通风空调系统设计,对地铁隧道通风与空调运行模式、隧道通风系统及冷却塔布置形式进行了分析,提出了合理可行的方案,从而优化地铁通风空调设计,有效降低造价,减少能耗。     

A second order turbulence model for the prediction of air movement and heat transfer in a ventilated room

A full-scale test room is used to investigate experimentally and numerically the velocity and temperature fields in the case of a mechanical ventilation. Detailed fields are measured for three cases of ventilation air temperature: an isothermal case, a hot case, and a cold case. The experimental data are used to test two turbulence models: a first order k-ε realizable turbulence model and a second order quadratic RSM (Reynolds Stress Model) turbulence model. The RSM model predicts the temperature and velocity fields better than the k-ε turbulence model. In particular, global values of velocity and temperature coming from experiments are in good agreement with the RSM turbulence model. This conclusion is confirmed using a turbulence analysis based on Lumley triangles.