编组站小能力驼峰空压动力系统规模设计探讨

编组站小能力驼峰空压动力系统规模设计探讨铁道部第三勘测设计院机械处蒋学锋小能力驼峰一般指设在区段站、工业站、港湾站及部分地方性编组站上或大型编组站的地区车场上，解体能力为２００～２０００辆，调车线一般为６～１６条的驼峰。随着大、中能力驼峰现代化建设的...

编组站驼峰空压动力站的优化设计

本文通过对以往设计或调研的编组站驼峰空压动力站进行回顾和分析,在确保编组站运营安全的前提下进行优化,得出合理的配置,为设计或使用单位提供一些参考,同时也是对国家节能减排政策的积极响应。

LGBK型一体化智能孔板流量计在动力空压站的应用

本文主要介绍LGBK型一体化智能孔板流量计在动力空压站内压缩空气、净环水系统设计上的应用。在动力空压站内净环水进水母管及压缩空气送外网母管设置了一体化智能孔板流量计,介质流量计测量力图达到在类似工程设计中有借鉴作用。

Comparative investigations of pressure waves induced by trains passing through a tunnel with different speed modes

Pressure waves induced by high-speed trains passing through a tunnel have adverse effects on train structures and passenger comfort. These adverse effects can be alleviated when the train passing through the tunnel with a speed mode of deceleration. Thus, to investigate the effect of speed modes on pressure waves, three-dimensional compressible unsteady Reynolds-averaged Navier-Stokes simulations and the sliding mesh are used to simulate pressure waves on train surfaces and tunnel walls when trains passing through a tunnel with three different speed modes(a constant speed at350 km/h, a uniform deceleration from 350 to 300 km/h, and another uniform deceleration from 350 to 250 km/h).Compared with the constant speed, the peak-to-peak of the train surface pressure under the other two speed modes reaches a maximum difference of 11.0%. The maximum positive pressure difference of the tunnel wall under different speed modes is caused by the different attenuation of the friction effect when the train enters the tunnel, and the maximum difference is 12.8%. The difference of the maximum negative pressure on the tunnel wall is caused by the different speed and pressure wave intensity of the train arriving at the same measuring point in different speed modes,and the maximum difference is 15.8%. Hence, it can be concluded that a speed mode of deceleration for trains passing a tunnel can effectively alleviate the aerodynamic effect in the tunnel, especially for the pressure on the tunnel wall.

Numerical Simulation of Wind Turbine Blade-Tower Interaction

Numerical simulations of wind turbine blade-tower interaction by using the open source OpenFOAM tools coupled with arbitrary mesh interface （AMI） method were presented. The governing equations were the unsteady Reynolds-averaged Navier-Stokes （RANS） which were solved by the pimpleDyMFoam solver, and the AMI method was employed to handle mesh movements. The National Renewable Energy Laboratory （NREL） phase VI wind turbine in upwind configuration was selected for numerical tests with different incoming wind speeds （5, 10, 15, and 25 m/s） at a fixed blade pitch and constant rotational speed. Detailed numerical results of vortex structure, time histories of thrust, and pressure distribution on the blade and tower were presented. The findings show that the wind turbine tower has little effect on the whole aerodynamic performance of an upwind wind turbine, while the rotating rotor will induce an obvious cyclic drop in the front pressure of the tower. Also, strong interaction of blade tip vortices with separation from the tower was observed.

Simulation of Airblast Load and Its Effect on RC Structures

In the analysis of a structure subjected to an explosion event, the determination of the blast load constitutes a crucial step. The effect of the blast load on the structure depends not only on the peak shock overpressure, but also the impulse (hence the duration). For structures with a regular geometry, the blast load may be fairly well estimated using appropriate empirical formulae; however, for more complex situations, a direct simulation using appropriate computational techniques is necessary. This paper presents a numerical simulation study on the prediction of the blast load in free air using a hydrocode, with focus on the sensitivity of the simulated blast load to the mesh grid size. The simulation results are compared with empirical predictions. It is found that the simulated blast load is sensitive to the mesh size, especially in the close-in range, and with a practically affordable mesh grid density, the blast load tends to be systematically underestimated. The study is extended to internal blast cases. An example concrete slab under internal explosion is analyzed using a coupled analysis scheme. The internal blast load from the simulation is examined and the response of the RC slab is commented.

Numerical investigation of cavitating flow behind the cone of a poppet valve in water hydraulic system

Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using advanced RNG k-epsilon turbulence model. The flow was turbulent, incompressible and unsteady, for Reynolds numbers greater than 43 000. The working fluid was water, and the structure of the valve was simplified as a two dimensional axisymmetric geometrical model. Flow field visualization was numerically achieved. The effects of inlet velocity, outlet pressure, opening size as well as poppet angle on cavitation intensity in the poppet valve were numerically investigated. Experimental flow visualization was conducted to capture cavitation images near the orifice in the poppet valve with 30° poppet angle using high speed video camera. The binary cavitating flow field distribution obtained from digital processing of the original cavitation image showed a good agreement with the numerical result.

Comparison among sea surface roughness schemes

Based on the measurements from the US National Data Buoy Center 3-m discus buoy site No. 44004 （38.5°N, 70.47°W） from January 1 to March 31 of 2003, with the COARE algorithm （Version 3.0）, the results from four parameterization schemes developed recently for sea surface aerodynamic roughness length were compared with each other. Calculations of frictional speed u., drag coefficient Ca and wind stress r indicate that the calculated frictional velocities from the four schemes （8.50%-16.20%, the normalized standard error estimate, or NSEE）, the computed drag coefficients and wind stress （respectively 15.08%-28.67% and 17.26%,50.59% NSEE） are reasonable. Schemes YT96 and GW03 are consistent. The 002 scheme gives overestimated values for u, and Ca. Schemes TY01 and GW03 display discontinuous characteristics in handling young wave data.

Aerodynamic performance of high-turning curved compressor cascade with boundary layer suction

The impact of boundary layer suction on the aerodynamic performance of a high-turning compressor cascade was numerically simulated and discussed.The aerodynamic performance of a curved and a straight cascade with and without boundary layer suction were comparatively studied at several suction flow rates.The results showed that boundary layer suction dramatically improved the flow behavior within the flow passage.Moreover,higher loading over the whole blade height,lower total pressure loss,and higher passage throughflow were achieved with a relatively small amount of boundary layer removal.The integration of curved blade and boundary layer suction contributed to better aerodynamic performance than the cascades with only curved blade or boundary layer suction used,and the more favorable effect resulted from the weakening of the three dimensional effects of the boundary layer close to the endwalls.

Space Drive Propulsion Principle from the Aspect of Cosmology

This paper describes the propulsion principle using the concept of space drive and the pressure of the field induced by local rapid expansion of space based on the latest cosmology. Assuming that space vacuum is an infinite continuum, the propulsion principle utilizes the pressure field derived from the geometrical structure of space, by applying both continuum mechanics and general relativity to space. The propulsive force is a pressure thrust that arises from the interaction of space-time around the spaceship external environment and the spaceship itself; the spaceship is propelled by the pressure used against the space-time structure. As is well known in cosmology, the expansion rule of the universe is governed by the Friedman＇s equations and the Robertson-Walker metric. In this time, the propulsion principle of space drive is introduced from another angle （cosmology）, that is, the pressure of the field induced by local expansion of space is completely considered in the propulsion principle.

The Effect of Micro Air Movement on the Heat and Moisture Characteristics of Building Constructions

The research focuses on the effect of air movement through building constructions. Although the typical air movement inside building constructions is quite small （velocity is of order -10-5 m/s）, this research shows the impact on the heat and moisture characteristics. The paper presents a case study on the modeling and simulation of 2D heat and moisture transport with and without air movement for a building construction using a state-of-art multiphysics FEM software tool. Most other heat and moisture related models don＇t include airflow or use a steady airflow through the construction during the simulation period. However, in this model, the wind induced pressure is dynamic and thus also the airflow through the construction is dynamic. For this particular case study, the results indicate that at the intemal surface, the vapor pressure is almost not influenced by both the 2D effect and the wind speed. The temperatures at the inner surface are mostly influenced by the 2D effect. Only at wind pressure differences above 30 Pa, the airflow has a significant effect. At the extemal surface, the temperatttres are not influenced by both the 2D effect and the wind speed. However, the vapor pressure seems to be quite dependent on the wind induced pressure. Overall it is concluded that air movement through building materials seems to have a significant impact on the heat and moisture characteristics. In order to verify this statement and validate the models, new in-depth experiments including air flow through materials are recommended.

Quantum Entanglement Dynamics of Two Atoms in Quantum Light Sources

Quantum entanglement dynamics of two Tavis-Cummings atoms interacting with the quantum light sourcesin a cavity is investigated.The results show the phenomenon that the concurrence disappears abruptly in a finite time,which depends on the initial atomic states and the properties of squeezed states.We find that there are two decoherencefreestates in squeezed vacuum fields:one is the singlet state,and the other entangled state is the state that combinesboth excited states and ground states with a relative phase being equal to the phase of the squeezed state.

CFD Investigation of Compressible Low Angles of Attack Flow over the Missile

In modem missile design, the operation of a missile aerodynamics with angles of attack is required to serve a demand on the maneuverability. The key aero-physics is the development of vortices and its interaction to the control surface such as wing and fins. This paper thus presents the investigation of the missile flow field at 4° and 8° degrees of angles of attack. The Mach numbers for both case were varied from 0.6 to 5.5. Here, the Steady Reynolds-Averaged Navier-Stokes （SRANS） equations with standard κ-ε turbulence model were selected. The numerical results of aerodynamics coefficients （both force and moment） were compared against semi-empirical data computed using Missile DatCOM. The results revealed the development of vortices observed and their interaction with fin at the rear part of the missile.

Effects of Axial Non-uniform Tip Clearances on Aerodynamic Performance of a Transonic Axial Compressor

This paper presents a numerical investigation of effects of axial non-uniform tip clearances on the aerodynamic performance of a transonic axial compressor rotor （NASA Rotor 37）. The three-dimensional steady flow field within the rotor passage was simulated with the datum tip clearance of 0.356 mm at the design wheel speed of 17188.7 rpm. The simulation results are well consistent with the measurement results, which verified the numeri- cal method. Then the three-dimensional steady flow field within the rotor passage was simulated respectively with different axial non-uniform tip clearances. The calculation results showed that optimal axial non-uniform tip clearances could improve the compressor performance, while the efficiency and the pressure ratio of the com- pressor were increased. The flow mechanism is that the axial non-uniform tip clearance can weaken the tip leak- age vortex, blow down low-energy fluids in boundary layers and reduce both flow blockage and tip loss.

Aerodynamic Performance and Noise Characteristics of a Centrifugal Compressor with Modified Vaned Diffusers

Improvement of aerodynamic performance and reduction of interaction tone noise of a centrifugal compressor with vaned diffusers are discussed by experiments and visualization techniques using a colored off-film method. The focus of the research is concentrated on the leading edge shape of diffuser vanes that are deeply related to the generation mechanism of the interaction tone noise. The compressor-radiated noise can be reduced by more than ten decibels by using modified diffuser vanes which have 3-D tapered shapes on both pressure and suction sur- faces of the leading edge. Furthermore, by adopting the proposed modified diffuser vanes, the secondary flow which is considered to be an obstruction of diffuser pressure recovery can be suppressed, and also the pressure decrease observed in the throat part of the diffuser flow passage is reducible. Thus, the proposed diffuser vanes show a favorable result for both noise and the aerodynamic performance of the centrifugal compressor, and offer a few basic guidelines for the diffuser vane design.

The Unsteady Fluctuating Pressure and Velocity in a Cross Flow Fan

This paper investigates the relations between the fluctuating pressure and velocity of the source by means of nu- merical method and sound pressure in the far field obtained with an noise experiment for a novel cross flow fan. The frequency characteristics of the fluctuating pressure and velocity in a cross flow fan are analyzed by means of spectral analysis and wavelet transform. The fluctuating pressures obtained by large eddy simulation on the casing wall are compared with that of experiments and show good agreement. From the spectral analysis of sound source, it is found that the pressure fluctuating peak is correspond with the sound pressure in the far field.

Internal flow structure,fault detection,and performance optimization of centrifugal pumps

This review mainly summarizes the latest developments in the internal flow field and external characteristics of centrifugal pumps.In particular,the latest findings of centrifugal pumps focused on turbulence and cavitation models,flow visualization methods,and fault detection based on noise and vibration.The external characteristics,cavitation,and vibration of the centrifugal pump were extensively discussed.In addition,advanced multi-objective optimization methods for improving impeller’s efficiency and reducing net positive suction head(NPSH)were briefed.Although some progress was made in this field,there remain many unsolved problems,such as monitoring and modeling of cavitation,rotational stall phenomenon,and discrepancies between simulation and measurement.In the future,researchers are encouraged to employ multi-dimensional flow visualization technologies and high-performance computing facilities to advance existing understandings on these issues and create new research directions.

Effect of Vane Opening on Aerodynamic Performance of the Ram-rotor Test System

In order to research the influence of adjustable vane on the aerodynamic performance of the ram-rotor test system, FLUENT soft-ware has been adopted to simulate the flow passage of the ram-rotor test system numerically. The vane opening is controlled by changing the stagger angle of the vane blades. Results show that flow uniformity of vane outlet is influenced by the vane openings, which has an impact on the aerodynamic loss to some extent. Total pressure ratio, adiabatic efficiency and mass flow rate can be regulated by different openings of the vane. Compared with -8° vane opening, top efficiency of the ram-rotor increases by about 13.8% at ＋6° opening. And total pressure ratio drops by 5.87%. The rising opening increases the relative Mach number at inlet of the ram-rotor and weakens the intensity of the tip clearance leakage, which comes to a decreasing aerodynamic loss.

Study of Polytropic Exponent Based on High Pressure Switching Expansion Reduction

Switching expansion reduction(SER) uses a switch valve to substitute the throttle valve to reduce pressure for high pressure pneumatics.The experiments indicate that the simulation model well predicts the actual characteristics.The heat transfers and polytropic exponents of the air in expansion tank and supply tanks of SER have been studied on the basis of the experiments and the simulation model.Through the mathematical reasoning in this paper,the polytropic exponent can be calculated by the air mass,heat,and work exchanges of the pneumatic container.For the air in a constant volume tank,when the heat-absorption is large enough to raise air temperature in discharging process,the polytropic exponent is less than 1;when the air is experiencing a discharging and heat-releasing process,the polytropic exponent exceeds the specific heat ratio(the value of 1.4).

Investigations on the Improving Aerodynamic Performances of Last Stage Steam Turbine and Exhaust Hood under Design and Off Design Conditions

The purpose of this paper is to improve the aerodynamic performances of the last stage turbine and the exhaust hood of a 600MW steam turbine under design and off design conditions. During operation, strong flow interactions between the turbine and the exhaust hood impose influences on the flow behavior in the hood and lead to the unsatisfactory aerodynamic performance of the turbine and exhaust hood. So the exhaust hood has the potential to be improved in terms of aerodynamic efficiency. Considering the flow interactions between the turbine and the exhaust hood, the profiles of the diffuser end-wall were optimized. The coupled model turbine and model exhaust hood calculations and experiments were carried out to validate the effects of the optimization. Model experiments show that the design modifications resulted in a substantial increase in the overall pressure recovery coefficient. The flow and aerodynamic performances of the full-scale last stage turbine and full-scale exhaust hood were simulated to explore the flow physics alterations to the modification of diffuser geometry. The wet steam was selected as the flow medium. The actual flow fields trader different operation conditions were analyzed.