似膏体料浆管输中浆击分析与计算研究

为了缓解管输过程中浆击对管路产生的破坏作用,分别采用了FLUENT模拟和流体力学理论计算两种方式,研究了似膏体料浆在管输中的直接浆击现象,两种方式比较结果表明,理论计算有局限性,且只能静态的表达;FLUENT模拟能直观、动态地表达浆击的压强、速度变化过程;二者压力波速度场符合较好,压强场有一定差距。研究结果对后续提出缓解管道浆击影响和破坏的措施有较强的指导意义。

火电厂输灰管路浆体水击瞬变过程数值计算与分析

水力输灰在火电厂中获得越来越广泛的应用。在浆体水击瞬变过程基本方程的基础上,运用特征线方法建立了考虑含气量的伪均质浆体停泵水击瞬变过程数学模型。对某火电厂输灰复合管道计算了当水泵发生事故停泵时,水泵出口压力相对值,泵的无因次流量,泵的无因次转速,管道顶端最高点处的压力水头相对值的瞬变过程。通过对数值计算结果的分析,提出了在管道顶端最高点设置调压井和增大电机飞轮力矩的方法来降低管道中浆体水击的危害。

CFD技术在固液两相流浆体水击压强计算中的应用

采用计算流体力学(CFD)动网格方法的弹性光顺法与局部网格重划法对阀门关闭过程进行了动态模拟,对阀门突然关闭引起的固液两相流浆体水击压强进行了数值计算。通过改变阀门关闭速度分析了阀门关闭时间对水击压强产生的影响进行了分析,并比较了不同初始流速对水击压强的影响。结果表明:延长阀门关闭时间将减小浆体水击压强的最大值,关闭时间超过2s后减小效果可忽略不计;阀门关闭时间一定时,初始流速越大浆体水击压强最大值也越大。

某火电厂灰渣泵水击现象浅析

本文分析了某电厂输灰系统布置特点,针对除灰泵遇紧急状况停止运转时倒流灰浆对泵体产生的破坏现象进行分析,对灰渣泵水击现象进行模拟分析与计算,校核泵壳强度,并对其飞逸转速进行计算。通过理论分析与实际计算相结合,对该电厂输灰系统装置提出了改进措施。

Effect of impinging angle and rotating speed on erosion behavior of aluminum

Commercial aluminum（grade 1900） in rotary motion was exposed to slurry of sand in water.Samples were mounted at various angles and rotated at different speeds.Wear rate was calculated using mass loss measurement.The results show that wear rates increase with increasing impingement angle up to 90°.Contrary to the conventional understanding of maximum loss of ductile material at about 45° impingement angle,maximum wear rate was observed in case of the aluminum sample fixed at 90°.However,increasing rotation speed of the samples results in exponential increase in wear rate.The findings are substantiated with the metallographic study of worn surface.

Technological Evolution of Historic Structural Mortars

Mortars are among the first building materials used in constructions, even from prehistoric times （8th millennium BC）. Their study reveals a great source of information regarding the evolution of their technological characteristics and application techniques, the availability and exploitation of raw materials, as well the wider socio-economic aspects of each era. The aim of this paper is to comparatively evaluate the analysis results from approximately 1,000 structural mortar samples taken from various monuments and historic buildings of Greece, dated from the Hellenistic period, until the beginning of the 20th century. The analysis focused in the determination of their physico-mechanical and chemical properties, such as porosity, apparent specific gravity, mechanical strength, aggregates type and granulometry and chemical composition. Through the results＇ evaluation, significant remarks can be made upon the evolution of the raw materials used （binding system, aggregates, additives）, as well as regarding the final properties of historic structural mortars. It is concluded that hydrated lime was the main binding agent used for a long-lasting period of 2.5 millenniums, while mixed type binding systems based on lime and natural pozzolan were systematically used for producing durable mortars, resistant to humidity. In any case, it seems that ancient masons were fully aware of the significant role of mortars in constructions and were capable of exploiting the available raw materials and application techniques to the maximum.

Optimum Level of Replacement Slag in OPC-Slag Mortars

The present paper reports the testing of 14 OPC-slag mortars and 2 controls OPC and slag mortars. The main aim is to determine the optimum level of replacement slag for achievement to the highest early strength with reasonable flow. Variable was the level of GGBFS in the binder. In this experimental work, two types of sands were used that are： silica and mining sands. It is determined that the optimum level of replacement slag is 40% and use of silica sand in OPC is preferable to mining sand and reversely, use of mining sand is preferred in GG100 to silica sand. All mortars had W/B and S/B 0.33 and 2.25, respectively.

Strength Development of Cement-Slag Mortars

In this experimental work, three groups of cement-slag mortars namely OPC, OPC-slag, and slag mortars were made. All were cured in both water and air under room temperature. Strength development was studied up to 90 days. The mortars were prepared using 0%, 50%, and 100% replacement with slag. The sensitivity for all groups was obtained against the curing regime with the highest being attributed to the slag mortars. The highest and lowest strengths at early ages were attributed to OPC and slag mortars when both were cured in water. The highest and lowest strengths were attributed to OPC-slag and slag mortars at later ages, respectively. The highest strengths for OPC-slag, OPC, and slag mortars were as 72.0, 64.0, and 21.5 MPa at 90 days when the specimens cured in water, respectively. Strength loss was observed for all groups at later ages when cured in air under room temperature. The maximum and minimum, of about 8.0% and 1.3%, occurred at 56 and 90 days for slag and OPC-slag mortars, respectively.

沙漠地质地区油气站基础施工技术

针对沙漠地质基础施工中地下水位高和粉砂土力学性质差等问题,本文以若羌至民丰高速公路服务区油气站建设为例,通过采用管井降水法、戈壁料换填法和对换填基础采用一次击入注浆法进行加固等成套技术,确保了油气站基础满足强度和抵抗变形的要求,达到了预期效果。

Quantification of Cement Content in Mortars Using the Background of X-Ray Diffraction Spectra

This study proposes a model to determine the content of cement in mortars using the background of X-ray diffraction （XRD） spectra taking advantage of the fact that fluorescence radiation for the Cu anticathode is different in cement paste and aggregates, and also that cement paste and aggregates have different crystallinity degrees. The method has been tested for limestone mortars with five different types of cement： I52,5N/SR, CEMII/A-L32,5N, IIIA42,5N/SR, IVA（V）32,5N/SR y CAC.

Effect of three-electrode plasma synthetic jet actuator on shock wave control

A three-electrode high-energy plasma synthetic jet(PSJ) actuator was used for shock wave control. This actuator is an enhanced version of the two-electrode actuator as a high-voltage trigger electrode is added to increase the cavity volume and the input energy while retaining a relatively low disruptive voltage. The electrical properties were studied using current-voltage measurements, and the energy consumption was calculated. To assess the jet strength, the penetration of PSJ was compared with empirical values, and the results show that the momentum flux ratio of PSJ for a capacitance of 0.96, 1.6, and 3 μF was approximately equal to 0.6, 1.0, and 1.3, respectively. The interaction of PSJ with shock waves was acquired using high-speed shadowgraph imaging. The shock was generated by a 25° compression ramp in Mach 2 flow, and PSJ actuator was placed up-stream of the compression ramp. Under the action of PSJ, the strength of the shock was notably weakened, and the near-wall part of the shock was entirely eliminated. The results show the good control effect of the three-electrode high-energy PSJ in high-speed flow.

Plasma perturbations in the coexisting environment of VLF transmitter emission, lightning strokes and seismic activity

We analyzed plasma perturbations occurring in the coexisting environment of powerful VLF transmitter emission, intense lightning strokes and strong seismic activity during pregnant period. The results suggest that anomalous electron bursts with energy dispersion in the range of ~100–350 keV, forming the "wisp" signature, are due to cyclotron resonance of electrons with monochromatic waves from the powerful NWC VLF transmitters during nighttime. The intense broad band VLF emissions (up-going 0+ whistlers) are observed while the DEMETER satellite goes through the region of intense thunderstorm activities at mid-latitudes. However, the effects of intense lightning activity and pregnant earthquake have little impact on this kind of stable energy-dispersed electron structures, despite the fact that they are presumably two primary reasons for the particle precipitation in the ionosphere. The case studied here provides us a valuable opportunity to address the various sources triggering the anomalous plasma perturbations in the ionosphere.

Three-dimensional Numerical Study of Laminar Confined Slot Jet Impingement Cooling using Slurry of Nano—encapsulated Phase Change Material

This Article presents a three dimensional numerical model investigating thermal performance and hydrodynamics features of the confined slot jet impingement using slurry of Nano Encapsulated Phase Change Material(NEPCM)as a coolant.The slurry is composed of water as a base fluid and n-octadecane NEPCM particles with mean diameter of 100 nm suspended in it.A single phase fluid approach is employed to model the NEPCM slurry.The thermo physical properties of the NEPCM slurry are computed using modern approaches being proposed recently and governing equations are solved with a commercial Finite Volume based code.The effects of jet Reynolds number varying from 100 to 600 and particle volume fraction ranging from 0% to 28% are considered.The computed results are validated by comparing Nusselt number values at stagnation point with the previously published results with water as working fluid.It was found that adding NEPCM to the base fluid results with considerable amount of heat transfer enhancement.The highest values of heat transfer coefficients are observed at H/W=4 and C_m=0.28.However,due to the higher viscosity of slurry compared with the base fluid,the slurry can produce drastic increase in pressure drop of the system that increases with NEPCM particle loading and jet Reynolds number.