Cross-Ventilation of Underground Railway Tunnels

1979 ◽  
Vol 101 (1) ◽  
pp. 128-134
Author(s):  
A. E. Vardy
Keyword(s):  
Drag Force ◽  
Aerodynamic Drag ◽  
Pressure Fluctuations ◽  
Rapid Transit ◽  
Transit Systems ◽  
Low Speed ◽  
High Speeds ◽  
Large Pressure ◽  
Underground Railway ◽  
Small Holes

The aerodynamic merits and demerits of cross-ventilating adjacent tunnels in underground rapid transit systems are discussed. Three types of cross-ventilation are considered, namely (a) numerous small holes in the dividing wall between the tracks in a cut-and-cover tunnel, (b) a curtailed dividing wall and (c) passages linking separately bored tunnels. It is shown that considerable reductions in the air velocities expected on station platforms will result if the end regions of the tunnels are well cross-ventilated. Additionally, useful reductions in the aerodynamic drag force on trains can be expected if cross-ventilation is provided along the whole length of the tunnel. However, this is recommended only for low speed systems because interaction between passing trains will cause large pressure fluctuations at high speeds.

Unsteady Airflows in Rapid Transit Systems

1980 ◽  
Vol 194 (1) ◽  
pp. 341-348 ◽  
Author(s):  
A. E. Vardy
Keyword(s):  
Pressure Fluctuations ◽  
Theoretical Models ◽  
Relative Importance ◽  
Clear Indication ◽  
Rapid Transit ◽  
Night Time ◽  
Transit Systems ◽  
Sufficient Detail ◽  
Wind Velocities ◽  
System Characteristics

The measurement of pressure fluctuations on the London Transport Victoria Line is described and results are presented in sufficient detail for accurate comparisons to be made with theoretical models. Measurements were obtained during the night-time shut-down period, and so complicating effects due to other trains are absent. The results give a clear indication of the relative importance of several events such as entry to and exit from a station. The effectiveness of cross-passages for draught relief is clearly demonstrated. A computer program is used to simulate the airflows, and satisfactory correlation is obtained with the measured results at different train speeds. The program is used to predict system characteristics that were not measured during the tests. It is found that platform wind velocities and passenger pressure histories do not violate recommended acceptable limits even when the train passes through the station at 65 km/h without stopping.

scholarly journals A Planning Method for Partially Grid-Connected Bus Rapid Transit Systems Operating with In-Motion Charging Batteries

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2550
Author(s):  
Andrés E. Díez ◽  
Mauricio Restrepo
Keyword(s):  
Planning Method ◽  
Bus Rapid Transit ◽  
Rapid Transit ◽  
Infrastructure Planning ◽  
Transit Systems ◽  
Power Train ◽  
Medium Voltage ◽  
Grid Connection ◽  
Electric Bus ◽  
Decision Variables

This paper presents an electrical infrastructure planning method for transit systems that operate with partially grid-connected vehicles incorporating on-board batteries. First, the state-of-the-art of electric transit systems that combine grid-connected and battery-based operation is briefly described. Second, the benefits of combining a grid connection and battery supply in Bus Rapid Transit (BRT) systems are introduced. Finally, the planning method is explained and tested in a BRT route in Medellin, Colombia, using computational simulations in combination with real operational data from electric buses that are currently operating in this transit line. Unlike other methods and approaches for Battery Electric Bus (BEB) infrastructure planning, the proposed technique is system-focused, rather than solely limited to the vehicles. The objective of the technique, from the vehicle’s side, is to assist the planner in the correct sizing of batteries and power train capacity, whereas from the system side the goal is to locate and size the route sections to be electrified. These decision variables are calculated with the objective of minimizing the installed battery and achieve minimum Medium Voltage (MV) network requirements, while meeting all technical and reliability conditions. The method proved to be useful to find a minimum feasible cost solution for partially electrifying a BRT line with In-motion Charging (IMC) technology.

Creating the Wind Energy for Operating the 3-C-Section Blades Wind Car

2012 ◽  
Vol 622-623 ◽  
pp. 1188-1193 ◽  
Author(s):  
Hüseyin Çamur ◽  
Youssef Kassem
Keyword(s):  
Wind Speed ◽  
Angular Velocity ◽  
Wind Energy ◽  
Drag Force ◽  
Mechanical Energy ◽  
Main Shaft ◽  
Airflow Velocity ◽  
Low Speed ◽  
Low Wind Speed

The purpose of this work is to determine the drag characteristics and the torque of three C-section blades wind car. Three C-section blades are directly connected to wheels by using of various kinds of links. Gears are used to convert the wind energy to mechanical energy to overcome the load exercised on the main shaft under low speed. Previous work on three vertical blades wind car resulted in discrepancies when compared to this work. Investigating these differences was the motivation for this series of work. The calculated values were compared to the data of three vertical blades wind car. The work was conducted in a low wind speed. The drag force acting on each model was calculated with an airflow velocity of 4 m/s and angular velocity of the blade of 13.056 rad/s.

Visual Recognition System of Elastic Rail Clips for Mass Rapid Transit Systems

2007 ◽  
Author(s):  
Hsiang-Yu Hsieh ◽  
Nanming Chen ◽  
Ching-Lung Liao
Keyword(s):  
Visual Recognition ◽  
Experimental Testing ◽  
Recognition System ◽  
Morphological Processing ◽  
Driving Safety ◽  
Rapid Transit ◽  
Grey Level ◽  
Railway Transportation ◽  
Transit Systems ◽  
Mass Rapid Transit

In recent years, the railway transportation system has become one of the main means of transportation. Therefore, driving safety is of great importance. However, because of the potential of multiple breaks of elastic rail clips in a fixed rail, accidents may occur when a train passes through the track. This paper presents the development of a computer visual recognition system which can detect the status of elastic rail clips. This visual recognition system can be used in mass rapid transit systems to reduce the substantial need of manpower for checking elastic rail clips at present. The visual recognition system under current development includes five components: preprocessing, identification of rail position, search of elastic rail clip regions, selection of the elastic rail clip, and recognition of the elastic rail clip. The preprocessing system transforms the colored images into grey-level images and eliminates noises. The identification of rail position system uses characteristics of the grey-level variation and confirms the rail position. The search system uses wavelet transformation to carry out the search of elastic rail clip regions. The selection system finds a suitable threshold, using techniques from morphological processing, object search and image processing. The recognition system processes characteristics and structures of elastic rail clips. Experimental testing shows the ability of the developed system to recognize both normal elastic rail clip images and broken elastic rail clip images. This result confirms the feasibility in developing such a visual recognition system.

Comparison of Mixture and Multifluid Models for In-Nozzle Cavitation Prediction

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Michele Battistoni ◽  
Sibendu Som ◽  
Douglas E. Longman
Keyword(s):  
Mixture Model ◽  
Bubble Dynamics ◽  
National Laboratory ◽  
Pressure Fluctuations ◽  
Argonne National Laboratory ◽  
Numerical Approach ◽  
Fuel Injectors ◽  
Cavitation Inception ◽  
Noncondensable Gases ◽  
Large Pressure

Fuel injectors often feature cavitation because of large pressure gradients, which in some regions lead to extremely low pressures. The main objective of this work is to compare the prediction capabilities of two multiphase flow approaches for modeling cavitation in small nozzles, like those used in high-pressure diesel or gasoline fuel injectors. Numerical results are assessed against quantitative high resolution experimental data collected at Argonne National Laboratory using synchrotron X-ray radiography of a model nozzle. One numerical approach uses a homogeneous mixture model with the volume of fluid (VOF) method, in which phase change is modeled via the homogeneous relaxation model (HRM). The second approach is based on the multifluid nonhomogeneous model and uses the Rayleigh bubble-dynamics model to account for cavitation. Both models include three components, i.e., liquid, vapor, and air, and the flow is compressible. Quantitatively, the amount of void predicted by the multifluid model is in good agreement with measurements, while the mixture model overpredicts the values. Qualitatively, void regions look similar and compare well with the experimental measurements. Grid converged results have been achieved for the prediction of mass flow rate while grid-convergence for void fraction is still an open point. Simulation results indicate that most of the vapor is produced at the nozzle entrance. In addition, downstream along the centerline, void due to expansion of noncondensable gases has been identified. The paper also includes a discussion about the effect of turbulent pressure fluctuations on cavitation inception.

Effects of inlet radial distortion on the type of stall precursor in low-speed axial compressor

2016 ◽  
Vol 232 (1) ◽  
pp. 55-67 ◽  
Author(s):  
Ali Arshad ◽  
Qiushi Li ◽  
Simin Li ◽  
Tianyu Pan
Keyword(s):  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Experimental Investigations ◽  
Inlet Flow ◽  
Blade Loading ◽  
Stall Inception ◽  
Low Speed ◽  
Modal Type ◽  
Stall Precursor

Experimental investigations of the effect of inlet blade loading on the rotating stall inception process are carried out on a single-stage low-speed axial compressor. Temporal pressure signals from the six high response pressure transducers are used for the analysis. Pressure variations at the hub are especially recorded during the stall inception process. Inlet blade loading is altered by installing metallic meshed distortion screens at the rotor upstream. Three sets of experiments are performed for the comparison of results, i.e. uniform inlet flow, tip, and hub distortions, respectively. Regardless of the type of distortion introduced to the inflow, the compressor undergoes a performance drop, which is more severe in the hub distortion case. Under the uniform inlet flow condition, stall inception is caused by the modal type disturbance while the stall precursor switched to spike type due to the highly loaded blade tip. In the presence of high blade loading at the hub, spike disappeared and the compressor once again witnessed a modal type disturbance. Hub pressure fluctuations are observed throughout the process when the stall is caused by a modal wave while no disturbance is noticed at the hub in spike type stall inception. It is believed that the hub flow separation contributes to the modal type of stall inception phenomenon. Results are also supported by the recently developed signal processing techniques for the stall inception study.

scholarly journals Aerodynamic Performance of Road Vehicles

2020 ◽  
Vol 9 (6) ◽  
pp. 642-645
Keyword(s):  
Wind Tunnel ◽  
Drag Force ◽  
Aerodynamic Drag ◽  
Aerodynamic Performance ◽  
Polished Surface ◽  
Anova Analysis ◽  
Road Vehicles ◽  
Car Model ◽  
Group Data ◽  
Scale Models

Aerodynamic drag has been experimentally estimated for scale models of a passenger car and a commercial truck in a wind tunnel. Polished surface has resulted up to 15 % reduction in drag force and add-on has resulted in 57% increase in drag force of a car model whereas 2.6 % reduction in drag force has resulted by using deflector in a commercial truck model. Anova analysis shows variation in mean of group data.

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