开孔率对竖井型城市隧道阻滞工况自然通风影响的分析

为了分析开孔率对竖井型城市隧道在交通阻滞工况下对自然通风的影响,本文采用无量纲分析和模型试验的方法对其速度场、温度场和污染物浓度场进行了研究。通过对阻滞工况下隧道内空气所受的热压浮升力与重力的无量纲分析,得到了模型试验所需的热压通风相似准则数和温度分布相同所需散热量比例常数。利用所得相似条件搭建了开孔率分别为2.8%、3.7%、4.5%的3组试验模型进行试验。试验结果表明,随着开孔率的增大隧道内最不利通风段的通风效果得到改善,但竖井的建设费用大幅度提高。选择合适的竖井开孔率既能满足阻滞工况下隧道的通风要求,也能避免开孔率盲目增大导致的初投资浪费,对城市隧道建设具有重要意义。     

城市公路隧道通风方案的评估研究

对某城市隧道采用自然通风方案和三种机械通风方案进行了介绍,指出了机械通风常见的问题并提出了解决方案,通过评估发现这样能够节能35%~45%.从经济性角度对四种通风方案进行了对比,所得结论是采用自然通风方案总投资可以节约30%左右,具有显著的经济效益.最后对四种方案进行了综合比较,为公路隧道通风工程的设计提出了合理的建议.     

城市隧道竖井送排式通风优化

为了更有效地发挥送排风竖井在城市隧道中的通风作用,选择合理的送排风组合是一个重要的途径。本文采用CFD方法,对5种排风速度与5种送风速度的25种送排风组合进行了模拟,分析了不同送排风组合隧道内的通风效果。模拟结果表明:当送排比大于1时,隧道内会出现回流,且送排比越大,隧道回流效应越强,经济效益越低。隧道内气流分布和污染物浓度都与送排风组合有关,较大的排风速度虽有利于降低污染物浓度,但能耗也较大,过大或者过小的送风速度都会使隧道局部污染物浓度过高,降低通风作用。因此,综合考虑隧道通风经济性和实用性,确定排风速度为5~6m/s和送风速为8~12m/s为最优组合。选择合理的送排风组合,不仅能有效控制隧道污染物浓度,还能减少能量损失,对城市隧道的建设具有指导意义。     

高速地铁列车空气阻力数值模拟研究

针对高速地铁列车空气阻力直接影响列车运行速度、能耗及安全,采用三维数值模拟方法对6编组全尺寸列车运行在设置有通风竖井的区间隧道的列车空气阻力进行研究,对隧道内空气阻力随时间变化、列车各节车厢阻力的分布特性、每节车厢转向架在整车阻力所占的比重情况进行分析.研究结果表明:列车逐渐向竖井靠近的时间段内,阻力系数一直在下降,最小值为1.57;在经过竖井的时间段,阻力系数大大增加,最大值为4.85,是最小值的3.08倍.列车匀速行驶时,尾车空气阻力在整车中占比最大,头车略小,分别为39.6％和24.7％;过竖井正下方时,头车空气阻力占比是整车的一半之多,达到了53.9％.过竖井前,前5节车厢转向架阻力在35％～45％内波动,尾车的仅占12.7％;过竖井时,4车厢转向架阻力占比最大,最大值为52.7％,头车的降到了17.0％;过竖井后,中间4车厢转向架区域占比最大,头车尾车的占比略小.     

严寒地区通风房间室内甲醛污染物浓度分布规律研究

向室内引入新风是解决由装修材料加工工艺导致室内甲醛超标问题的根本方法之一。为了研究不同通风方法的有效性,本文利用Fluent软件,对自然通风和机械通风效果进行研究并分别分析不同送风口温度和不同送风速度对室内不同高度位置处的甲醛浓度的影响。模拟结果表明:自然通风工况下,不同送风温度下的甲醛浓度均超标,机械通风工况下,不同送风速度下的甲醛浓度均未超标;当进风口速度为2 m/s时,甲醛浓度最低;通过数值模拟,同一送风温度下,自然通风甲醛的浓度是机械通风的2.07倍。本文将模拟的2种工况在沈阳、营口进行实测,试验结果与模拟结果基本一致,进一步验证了该结论。     

船舶舱室通风设计与分析

介绍了船舶舱室通风设计的基本思路、通风量的计算方法,分析了部分舱室通风设计的要点和自然通风情况,以期为船舶舱室通风设计提供有益参考.     

铁路高瓦斯大断面隧道监测及通风施工技术

以某铁路隧道工程为例，基于高瓦斯大断面隧道施工安全隐患多、质量控制要求高的特点，研究具体通风方式，构建具备通风参数检测、通风状态监控多项功能的通风监控系统。阐述高瓦斯大断面隧道施工环境监控与安全预警的技术策略，结合实测数据研究高瓦斯大断面隧道施工环境的安全程度，评价通风技术的可行性。研究结果表明：通过瓦斯隧道监测及通风技术的应用，可及时反馈现场施工情况，提高了瓦斯隧道通风管理水平，有利于营造安全的隧道施工环境，推动隧道施工的顺利进行。     

海底沉管隧道射流风机通风效果影响因素的研究

针对海底沉管隧道"高度有限,宽度有余"的矩形断面结构特点,运用计算流体力学软件建立沉管隧道射流纵向通风方式的三维数值仿真模型,研究海底沉管隧道射流纵向通风方式的通风效果,通过正交试验分析沉管隧道内射流风机安装高度、安装角度、轴向净间距等安装因素对隧道通风效果的影响规律与影响程度,优化沉管隧道内射流风机布置形式,提高通风效果。分析结果表明:多种因素对隧道内风速影响的主次顺序为:射流风机安装高度、安装角度、轴向净间距;考虑海底沉管隧道高度有限的特点,可通过增加射流风机组安装角度来有效提高隧道内通风效果。     

百叶箱与通风防辐射罩的温度对比观测结果分析

通过分析郑州国家基准气象观测站2a的外场对比观测试验,对比分析了百叶箱与不同通风防辐射罩性能和差异。本次对比观测试验结果表明:不同的防辐射罩由于结构差异、体积差异和通风差异呈现相对较大的温度差:白天高温阶段,t玻璃钢t自然通风t强制通风;夜间低温阶段,t强制通风t玻璃钢t自然通风;日平均气温,t玻璃钢t强制通风。     

压缩空气在发电厂暖通设计中的拓展应用探讨

火力发电厂暖通空调系统设计中,地下电缆隧道通风、楼梯间加压送风及正压室等设计对电厂安全生产、人身安全起着重要作用。现从压缩空气的特性入手,探讨在常规设计受限时将压缩空气拓展应用于地下电缆隧道通风、楼梯间加压送风及正压室的设计,并与传统的机械通风方式进行了对比。     

A numerical simulation of train-induced unsteady airflow in a tunnel of Seoul subway

This study has been conducted to investigate numerically the characteristics of train-induced unsteady airflow in a subway tunnel. A three-dimensional numerical model using the dynamic layering method for the moving boundary of a train is applied. The validation of the present study has been carried out against the experimental data obtained by Kim and Kim [1] in a model tunnel. After this, for the geometries of the tunnel and subway train which are very similar to those of the Seoul subway, a three-dimensional unsteady tunnel flow is simulated. The predicted distributions of pressure and air velocity in the tunnel as well as the time series of mass flow rate at natural ventilation ducts reveal that the maximum exhaust mass flow rate of air through the duct occurs just before the frontal face of a train reaches the ventilation duct, while the suction mass flow rate through the duct reaches the maximum value just after the rear face of a train passes the ventilation duct. The results of this study can be utilized as basic data for optimizing the design of tunnel ventilation systems.     

A computational analysis of the airflow in a twin-track subway tunnel with a sliding-curtain to improve ventilation performance

A computational model of an actual Seoul subway tunnel was analyzed in this study. The computational model was comprised of one natural ventilation shaft, two mechanical ventilation shafts, one mechanical air supply, a twin-track tunnel and a train. The natural ventilation shaft discharges and supplies air due to the train’s movement. The mechanical ventilation shaft and the mechanical air supply discharges and supplies, respectively, the airflow from the axial flow fans in the middle of the ducts of the shafts. A sliding-curtain was installed in the tunnel. The objective of this study was to numerically investigate train-induced airflow in the twin-track subway tunnel with natural and mechanical ventilation shafts and an installed curtain. The numerical analysis characterized the aerodynamic behavior and performance of the ventilation system by solving three-dimensional turbulent Reynolds-averaged Navier-Stokes equations. ANSYS CFX software was used for the computations. The airflow velocity from the computational results was validated by experimental results. Understanding the flow pattern of the train-induced airflow in the tunnel is necessary to improve ventilation performance. The ventilation and aerodynamic characteristics in the tunnel, including train-induced airflow, were investigated by analyzing the volume flowrate at the exits of the ventilation shafts and the velocity in the tunnel. The computational results were compared to cases with and without a curtain installed in the twin-track tunnel. As the train passed the mechanical ventilation shafts, the quantity of discharged-air in the ventilation shafts decreased rapidly. The flowrate at the exits of the ventilation shafts was gradually recovered with time, after the train passed the ventilation shafts. The airflow at the natural shaft and mechanical ventilation shaft 2, which was closest to the curtain, was increased. The computational results showed that the installed curtain can improve ventilation performance in the tunnel.     

Field measurement and estimation of ventilation flow rates by using train-induced flow rate through subway vent shafts

This study measured and estimated the subway vent shaft air flow rate induced by moving trains in the tunnel. This work estimated the flow rate via the tunnel structure and train movement to determine the quantitative effect of vent shafts as air purification systems of natural ventilation to improve the air quality management of a subway. The amount of air suctioned into the tunnel is significantly larger than that vented from the tunnel. Thus, placing vent shafts near subway stations is desirable for natural ventilation systems. Experimental approaches to measure train-induced flow rates have not yet been published. Results of this study provide useful fundamental data to study the natural ventilation in a subway. Therefore, this study suggested the significant design factors required to control indoor air quality in a subway.     

Numerical optimization study to install air curtain in a subway tunnel by using design of experiment

Subways are a major mode of public transportation in metropolitan cities. A proper ventilation system is required to maintain indoor air quality in subway tunnels. Platform screen doors improve the platform environment but degrade air quality in subway tunnels. Trains transport fine particles from the tunnel into the platform. An air curtain installation in the subway tunnel permits traffic and reduces the transfer of bacteria and fine particles. The existing tunnel of Seoul subway was investigated by using computational fluid dynamics and design of experiment method for optimum air curtain installations. The flow field of the subway tunnel was computed by using ANSYS CFX software. Minitab software was used to generate the design process and to analyze the computational results. The computational domain of the existing tunnel included two natural ventilation shafts, one mechanical shaft, and the twin tracks. The height, width, and length of each track were 6, 4, and 400 m, respectively. The air curtain installation area was located between the natural and the mechanical ventilation shafts of Rrack 1. The design variables for the optimization study were the width, velocity, and installation location of the air curtain. The object function for optimization was mass flow rate at the natural ventilation shaft. The length of the air curtain was fixed at 4 m. The predicted mass flow rates were analyzed with the design variables by using the response surface method (RSM). The optimum values of the design variables, i.e., velocity, width, and installation location were 25 m/s, 0.2 m, and 5.8195 m, respectively. The maximum mass flow rate with the optimum design values was 114.4447 kg/s. The optimum values of the design variables were validated by computing the tunnel with the optimum values from RSM. The mass flow rate in the natural ventilation shaft 1 was 114.2 kg/s, as predicted. The optimization study can be helpful to set the optimum design conditions for the subway ventilation system.     

空调室外机轴流换热风扇性能研究

空调系统现在广泛应用于大型商场、饭店、车间等场所。为了提高换热效率和换热量,空调室外机大多采用轴流式换热风扇。通过对比发现,通风量在5 300~6 600m3/h的中型空调室外机研究较少。为了提高通流量和全压,从而增强换热效果,本文针对某公司产品中分体式空调室外机轴流换热风扇进行了风管性能测试实验与数值模拟。其中为了考核数值计算的可靠性,对于模拟仿真如何与实验匹配进行了计算区域的研究。结果表明进计算区域出口长度存在恰当匹配,并为数值模拟与风管实验台测试吻合提出了一个数值模拟计算域的选取准则。     

Tunnel ventilation controller design using an RLS-based natural actor-critic algorithm

Tunnel ventilation systems provide drivers with a comfortable and safe driving environment by generating sufficient airflow and by diluting the concentration of noxious contaminants below an acceptable level. For that purpose, tunnel ventilation systems contain mechanical equipment such as jet-fans, blowers and dust collectors. These machines consume large amount of energy, therefore, it is necessary to have an efficient operating algorithm for tunnel ventilation in terms of energy savings and safe driving. In this paper, a new reinforcement learning (RL) method is applied as the control algorithm. In the process of formulating the reward of the tunnel ventilation system, which is a performance index to be maximized in the RL methodology, the following two objectives are of great interest: maintaining an adequate level of pollutants and minimizing power consumption. The RL control algorithm adopted in this research is based on an actor-critic architecture and natural gradient method. Due to its ability to achieve the truly steepest direction of gradients, the natural gradient method can be a promising route to improving the efficacy of the actor module. Also, the recursive least-squares (RLS) method is employed to the critic module in order to improve the efficiency by which data is used. Using actual data collected from an existing tunnel ventilation system, extensive simulation studies were performed. It was confirmed that the suggested algorithm achieved the desired control goals and, when compared to previously developed RL-based control algorithms, improved the performance considerably.     

THREE DIMENSIONAL MULTIPHASE COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF VENTILATED SUPERCAVITATION

For some vehicles travelling through water, it is advantageous to cover the vehicle in a supercavity for the sake of reducing the drag acting on it. The method of artificial ventilation is most effective for generating and dominating the supercavity. This paper focuses on the numerical simulation of flow field around three dimensional body. The method is based on the multiphase computational fluid dynamics （CFD） model combined with the turbulence model and the full cavity model. The flow field of cavity is simulated by solving the compressible Navier-Stokes equations. The fundamental similarity parameters of ventilated supercavitaty flows that include cavitation number, Froude number, ventilation rate and drag coefficient are all investigated numerically in the case of steady flow and gravity field. We discuss the following simulations results in section 3： The variations of the cavitation number and the supercavity＇s relative diameter with ventilation rate （subtopic 3.1）; The drag coefficient versus the cavitation number （subtopic 3.2）; Deformation of supercavity axis caused by gravitational effect for three different fixed Froude numbers-2.8, 3.4, 4.2 （subtopic 3.3）. In subtopic 3.2, we give the comparison results of the drag reduction ratio among numerical simulation and experiment conducted in hydrodynamic tunnel and towing tank respectively. In subtopic 3.3, we summarize our discussion of gravitational effect on the axis deformation of supercavity as follows： In the case of smaller Froude number, the inclination of the cavity axis increases monotonously with increasing horizontal length, and reaches its maximal value at the end of supercavity; This deformation can be almost completely negligible when the Froude number Fr〉7. The comparisons with the experimental data in the hydrodynamic tunnel and the towing tank indicate that the present method is effective for predicting the flows around ventilated supercavity; that the numerical results is in good agreement with the experimental one     

前馈式智能控制隧道通风系统

通过对前馈式通风控制3种方式的比选,简述了长大隧道采用前馈式智能通风控制的优点,建立了该系统的交通流基本参数和风压模型以及工程设计原则,通过工程实施隧道污染物控制在设定值范围。