“缩腰型”配风方式在燃煤调整中的应用

分析了“缩腰型”配风缓解超温和减小汽温偏差的机理,通过实例分析证明了此种调整方式的有效性,为解决机组超温和汽温偏差提供了思路,可以帮助人们更好地理解二次风在炉中燃烧中的作用。

大淑村矿172103工作面防灭火技术研究

大淑村矿172103综放工作面为孤岛煤柱工作面,工作面与老巷连通较多,作为沿顶掘进、摸底回采工作面,上下端头不可避免留设三角煤柱,虽然煤层为不易自燃煤层,但推采过程中,多次发生过上隅角CO超标。通过采取堵、缩、注、洒的防自然发火措施,有效解决了上隅角CO超限问题,保证了工作面正常回采。

Parameter optimization for improved aerodynamic performance of louver-type wind barrier for train-bridge system

To improve the safety of trains running in an undesirable wind environment,a novel louver-type wind barrier is proposed and further studied in this research using a scaled wind tunnel simulation with 1:40 scale models.Based on the aerodynamic performance of the train-bridge system,the parameters of the louver-type wind barrier are optimized.Compared to the case without a wind barrier,it is apparent that the wind barrier improves the running safety of trains,since the maximum reduction of the moment coefficient of the train reaches 58%using the louver-type wind barrier,larger than that achieved with conventional wind barriers(fence-type and grid-type).A louver-type wind barrier has more blade layers,and the rotation angle of the adjustable blade of the louver-type wind barrier is 90–180°(which induces the flow towards the deck surface),which is more favorable for the aerodynamic performance of the train.Comparing the 60°,90°and 120°wind fairings of the louver-type wind barrier blade,the blunt fairing is disadvantageous to the operational safety of the train.

Risk for gastric neoplasias in patients with chronic atrophic gastritis:A critical reappraisal

Chronic atrophic gastritis （CAG） is an inflammatory condition characterized by the loss of gastric glandular structures which are replaced by connective tissue （non-metaplastic atrophy） or by glandular structures inappropriate for location （metaplastic atrophy）. Epidemiological data suggest that CAG is associated with two different types of tumors： Intestinal-type gastric cancer （GC） and type I gastric carcinoid （T I GC）. The pathophysiological mechanisms which lead to the development of these gastric tumors are different, It is accepted that a multistep process initiating from Helico- bacterpylori-related chronic inflammation of the gastric mucosa progresses to CAG, intestinal metaplasia, dysplasia and, finally, leads to the development of GC. The T I GC is a gastrin-dependent tumor and the chronic elevation of gastrin, which is associated with CAG, stimulates the growth of enterochromaffin-like cells with their hyperplasia leading to the development of T I GC. Thus, several events occur in the gastric mucosa before the development of intestinatype GC and/ or T I GC and these take several years. Knowledge ofCAG incidence from superficial gastritis, its prevalence in different clinical settings and possible risk factors as- sociated with the progression of this condition to gastric neoplasias are important issues. This editorial intends to provide a brief review of the main studies regarding incidence and prevalence of CAG and risk factors for the development of gastric neoplasias.

Effect of landform on aerodynamic performance of high-speed trains in cutting under cross wind

The effects of the different landforms of the cutting leeward on the aerodynamic performance of high-speed trains were analyzed based on the three-dimensional, steady, and incompressible Navier-Stokes equation and k-e double-equation turbulent model. Results show that aerodynamic forces increase with the cutting leeward slope decreasing. The maximum adding value of lateral force, lift force, and overturning moment are 147%, 44.3%, and 107%, respectively, when the slope varies from 0.67 to -0.67, and the changes in the cutting leeward landform have more effects on the aerodynamic performance when the train is running in the line No. 2 than in the line No. 1. The aerodynamic forces, except the resistance force, sharply increase with the slope depth decreasing. By comparing the circumstance of the cutting depth H=-8 m with that of H=8 m, the resistance force, lateral force, lift force, and overturning moment increase by 26.0%, 251%, 67.3% and 177%, respectively. With the wind angle increasing, the resistance force is nonmonotonic, whereas other forces continuously rise. Under three special landforms, the changes in the law of aerodynamic forces with the wind angle are almost similar to one another.

Experimental Characterization of the Action of an Artificial Wind on a Wind Turbine and Optimization of the Storage Efficiency of Compressed Air in Hybrid PV/Wind Turbine Systems

The general idea of this work is to improve the performance of CAES （compressed air energy storage） for its application in solar and wind systems through a restitution technique by creating an artificial wind. The efficiency of compressed air storage is often presented as a limit to its application. The present work describes a series of manipulations carried out in order to increase the yield. As the action of the artificial wind on the wind turbine is characterized by a reduced attack surface, a treated wind, a constant direction, an adjustable speed, it is therefore a question of acting on all the controllable parameters of the artificial wind to find the best way to use it to produce more energy from a certain quantity stored in a tank. The main manipulations consisted in determining： the optimal number of points of attack of the wind turbine; the nature of the action （continuous or interrupted） of the wind; the frequency of wind action and the duty cycle.

Effects of Inlet Circumferential Fluctuation on the Sweep Aerodynamic Performance of Axial Fans/Compressors

Swept blades have been widely used in the transonic fan/compressor of aircraft engines with the aids of 3D CFD simulation since the design concept of controlling the shock structure was firstly proposed and successfully tested by Dr.Wennerstrom in the 1980s.However,some disadvantage phenomenon has also been induced by excessively 3D blade geometries on the structure stress insufficiency,vibration and reliability.Much confusion in the procedure of design practice leading us to recognize a new view on the flow mechanism of sweep aerodynamical induction: the new radial equilibrium established by the influence of inlet circumferential fluctuation(CF) changes the inlet flows of blading and induces the performance modification of axial fans/compressors blade.The view is verified by simplified models through numerical simulation and circumferentially averaged analysis in the present paper.The results show that the CF source items which originate from design parameters,such as the spanwise distributions of the loading and blading geometries,contribute to the changing of averaged incidence spanwise distribution,and further more affect the performance of axial fans/compressors with swept blades.

L2F Anemometry Measurements of the Inter-Row FlowField Within a Transonic Axial Compressor Providedwith Curved Windows

When measurements are performed in high speed, small-scale compressors, the use of curved glasswindows is required in order to avoid any mismatch between the measurement window and the casing. However, the glass curvature leads to optical distortions, which hinder acceptable measurementsand can even prevent the acquisition of any data. Thus, an original optical assembly, which consistsin inserting a simple and inexpensive corrective window between the frontal lens of the anemometerand the shroud window, is proposed. The way of determining the geometric characteristics and theposition of this corrective window, which restores very acceptable fool, is presented in the paper. Thereliability of this corrective optical assembly is highlighted by comparative measurements in a test case.Using such an optical setting, L2F measurements were realized along a section, downstream of the inletguide vane (IGV) of a transonic compressor stage. The spatial resolution leads to a good descriptionof the interaction of the wake with the oblique shock emanating from the leading edge of the rotor.A phenomenological study of the wake/shock interaction with a change of frame is realized using thestreamwise equation of the transport of vorticity.

Results and Analysis of a L2F Flow Field Investigation within a High-Speed High-Pressure Centrifugal Compressor

The paper describes experimental results obtained using a laser two-focus anemometry technique in a high-speed, high-pressure ratio unshrouded centrifugal compressor. Measurements in such a small impeller are extremely difficult as the flow is restricted to narrow passages and as the temperature rise is very high. Even if the working principle of laser anemometry is well documented in literature, some specialities of our LA system are discussed.A description and an analysis of the inlet now field, based on integral methods, are proposed. Some passage velocity contours are presented. Whereas a potential flow structure exists up to the high meridional curvature region, the throughfiow pattern is largely distorted in the radial part of the impeller.Noticeable differences in ftow pattern between both channels are found, particularly through the low momentum fluid zone. A qualitative study of the vortical mechanisms ascribes them to the tip clearance effects.

Supersonic-Subsonic Transition in Relatively Narrow Channels

The flow structure in relatively narrow channels has a strong three-dimensional character with complex flow phenomena, including regions of localized separation, various vortical smictures, etc., all of which have to be considered when dealing with the problem of supersonic-subsonic transition. In this paper only the following three problems are considered: 1. the effect of channel width on transition from supersonic to subsonic velocities, 2. transition from supersonic to subsonic velocities in a system of shock waves - pseudoshock wave, 3. transition from subsonic to supersonic velocities in a critical cross section at the end of a duct with fully developed turbulent channel flow. Problems connected with vortical structures and flow separation were discussed by the same author elsewhere (see References).

Numerical Investigation of a High-subsonic Axial-flow Compressor Rotor with Non-axisymmetric Hub Endwall

The major source of loss in modem compressors is the secondary loss. Non-axisymmetric endwall profile contouring is now a well established design methodology in axial flow turbines. However, flow development in axial compressors is differ from turbines, the effects of non-axisymmetric endwall to axial compressors requires flow analysis in detail. This paper presents both experimental and numerical data to deal with the application of a non-axisymmetric hub endwall in a high-subsonic axial-flow compressor. The aims of the experiment here were to make sure the numerically obtained flow fields is the physical mechanism responsible for the improvement in efficiency, due to the non-axisymmetric hub endwall. The computational results were first compared with avail- able measured data of axisymmetric hub endwall. The results agreed well with the experimental data for estima- tion of the global performance. The coupled flow of the compressor rotor with non-axisymmetric hub endwall was simulated by a state-of-the-art multi-block flow solver. The non-axisymmetric hub endwall was designed for a subsonic compressor rotor with the help of sine and cosine functions. This type of non-axisymmetric hub end- wall was found to have a significant improvement in efficiency of 0.45% approximately and a slightly increase for the total pressure ratio. The fundamental mechanisms of non-axisymmetric hub endwall and their effects on the subsonic axial-flow compressor endwall flow field were analyzed in detail. It is concluded that the non-axisymmetric endwall profiling, though not optimum, can mitigate the secondary flow in the vicinity of the hub endwall, resulting in the improvement of aerodynamic performance of the compressor rotor.

Evolution of downsized crescent-shaped dune in wind tunnel experiment

The migration of a downsized crescent-shaped dune was investigated in a wind tunnel experiment.Quantified upwind influx and vertical oscillation of the sand bed were introduced to modulate the saturation level of the sand flux above the dune surface to affect dune evolution.The evolution was recorded by top-view photography and then abstracted as the evolution of self-defined characteristic quantities using a digital image processing algorithm.The results showed that,in contrast to the case for spanwise quantities,the evolution of streamwise quantities corresponds to a linear increase in the modulation magnitude more positively and in a monotonic and convergent manner.In contrast with quantities on the windward face,the changes in quantities with respect to the horns were nonmonotonic with time and almost uncorrelated with the variation in modulation strength,which reveals the distinctiveness of leeside evolution.

Investigation of modification design of the fan stage in axial compressor

The S2 flow path design method of the transonic compressor is used to design the one stage fan in order to replace the original designed blade cascade which has two-stage transonic fan rotors.In the modification design,the camber line is parameterized by a quartic polynomial curve and the thickness distribution of the blade profile is controlled by the double-thrice polynomial.Therefore,the inlet flow has been pre-compressed and the location and intensity of the shock wave at supersonic area have been controlled in order to let the new blade profiles have better aerodynamic performance.The computational results show that the new single stage fan rotor increases the efficiency by two percent at the design condition and the total pressure ratio is slightly higher than that of the original design.At the same time,it also meets the mass flow rate and the geometrical size requirements for the modification design.