Experiments on Breaking Rock With High-pressure Cavitating Water Jets

How to achieve the most efficient rock-breaking is the research direction of the rock-breaking technique. According to this problem, a series of experiments relating to the rock-breaking efficiency of cavitating water jets were carried out for different nozzles within different pump pressures and ambient pressures. The results show that the erosion depth increases proportionally with the pump pressure and decreases as the ambient pressure increasing on the same experimental condition. Erosion happens in the first few minutes, and after that, erosion does not increase with time. The erosiondepth of the convergent-straight nozzle is much lower than that of the convergent-divergent nozzle.     

Experimental Study of Flow and Heat Transfer in Heat Exchanger with Small Channels

The experimental study of the flow resistance and heat transfer characteristics are conducted for water and ethylene glycol solution (66% Wt) flowing in the heat exchanger with small rectangular microchannels . The heat exchanger having the channels of 0.4 mm in width, 2.0 mm in height, and 20 mm in length is heated by a hearing rod at the bottom surface, the upper and two side surfaces are adiabatic. During experiments, the Reynolds number are ranged from 2 to 2 500. The experimental results show that the flow friction factor decreases and Nusselt number increases with increasing Reynolds number for water and ethylene glycol solution. At a fixed Reynolds number, the Nusselt number for ethylene glycol solution with larger Prandtl number is greater than that for water. Meanwhile, the correlations of flow resistance and heat transfer in the heat exchanger with small channels are obtained for engineering application.     

一维稳态流非饱和土渗透系数垂直分布模型及其线性简化

渗透系数是控制地下水流动的重要参数,对渗透系数的空间分布规律进行研究具有重要的意义。基于Gardner模型获取了一维稳态流非饱和土渗透系数沿垂直分布模型,该模型用指数函数描述,受饱和渗透系数和无量纲的深度与流动率等因素的控制;该模型表明一维稳态流条件下均质典型土类的渗透系数其沿垂直方向变化趋势主要受比流量与饱和渗流系数的负数值二者之间的相对大小影响。分别采用泰勒级数方法和以地下水位处及地表处的渗透系数作为控制条件方法对一维稳态流非饱和土渗透系数沿垂直分布模型进行线性近似简化。采用泰勒级数方法获取的简化模型其计算误差随无量纲的深度增大而增大。简化后的模型具有形式简单、参数少等特点。通过算例对比简化模型与原模型的差异,计算结果表明:采用以地下水位处及地表处的渗透系数作为控制条件的方法进行线性近似简化的模型计算误差比采用泰勒级数方法获得的线性近似简化模型的计算误差小。     

Analysis of the Kinetic Theory of Submerged Abrasive Water Jets

Abrasive water jets can incise objects with strong rigidity under water. The analytical means of kinetic theory is optimal for theoretical problems of submerged abrasive water jets. The flow characteristics in submerged abrasive water jets were analyzed based on kinetic theory for multiphase flows. The impact characteristics of every phase in submerged abrasive water jets was analyzed and continuity and momentum equations subsequently were developed for solid, gas and liquids in submerged abrasive water jets. It is shown that if the distributing function of every phase were given, the law of its movement could be ascertained.     

A NUMERICAL STUDY ON NATURAL CONVECTION IN A CLOSED CAVITY PARTIALLY FILLED WITH POROUS MEDIUM

The present paper decribes numerical analytical results of natural convection in a closed cavity partially filled with porous medium by means of Forchheimer-Brinkman model. The effects of heated rate,permeability,height of porous region,heat conduction coefficients and aspect ratio on flow and heat transfar in the cavity are systematically investigated. Velocity and temperature fields in the cavity are given and dependence of average Nu on time is obtained.     

The Effect of Aspect Ratio on Natural Convection in a Cavity with Discrete Heaters at the Bottom and a Top Heat Sink

Numerical study is performed to analyse the influence of aspect ratio on the nat-ural convection of high Pr fluid in a cavity with five discrete heaters at the bottom and an isothermalheat snk at the top,The range of aspect ratio is from 0.082 to 0.333, Raw is 107 and Pr is 90.Inthe half of the eavity five independent flow cells seperated by zero stream lines can be observed atsmall aspect ratio,which gradually merge into a single flow when aspect ratio increases and finallybeeome a big cell at A = 0.333.The average nusselt number based on the cooling arca,Nuc,showsthe highest value at A=0.082.With the incrcase of A,Nuc decreases and arrives the lowest valuewhile A=0.138,then increases and reaches an extreme value as A=0.164.After that Nuc fluctu-ates with the variation of increasing rate of flow velocity.     

Numerical simulation and on-site test of anincreasing pipe gas delivery capacity device

The theoretical analysis and experiment show that the wall oscillation can reduce the friction drag of the pipe. The operation mechanism, on-site test and numerical simulation of the Increasing Gas Delivery Capacity Device for the Pipe (IGDCDP) invented by the author are introduced in the paper. The on-site test shows that the IGDCDP can not only reduce the friction drag, but also enhance the gas delivery capacity obviously in the natural gas network. The numerical simulation results show that at the time of inducing some new vortex disturbance waves, the pressure pulse wave generated from the impinging edge has an effect on the oscillation cavity wall to cause oscillation with the large structured vortex rings, so the oscillation cavity is the main component that generating the pulsed jet.     

碰撞对玉米籽粒结构损伤的实验研究

对不同品种的玉米籽粒进行下落碰撞实验,测定玉米籽粒破碎率与下落高度的关系。对下落碰撞后未破碎的完整籽粒进行静态压缩实验,测定玉米籽粒经过碰撞后压缩特性的变化规律。结果表明:玉米籽粒破碎率随下落高度的增大而增大;下落碰撞后未破碎的完整籽粒的最大破坏力、最大破坏能随下落高度的增大而减小,即下落碰撞后未破碎的完整籽粒的结构损伤随下落高度的增大而增大。     

南通地区强降雪和积雪深度预报研究

为了预防和减轻强降雪过程对设施农业和生产生活可能带来的不利影响,提高预报和服务水平,利用常规高空和地面资料、ECWMF 0.75°x 0.75°再分析资料,对南通地区1951年以来共19次区域性暴雪过程从影响系统、大气层积、动力和水汽条件等方面进行分析总结,并以2013年的区域性暴雪为例说明诊断分析和预报过程。结果显示：(1)南通属于北亚热带季风气候,雨或雨夹雪转暴雪过程占多数,判断降雪量要关注转为纯降雪以后的降水量,积雪深度还要注意地表温度的高低,因此必须同时考虑强冷空气南下和强盛暖湿气流北上的综合影响；(2)形成强降雪的天气系统主要包括南北两支西风槽、中低空切变、西南急流和低空冷垫,实例是典型区域性暴雪天气形势；(3)500～850 hPa高度至少有两层强盛的SW急流,强烈辐合上升主要发生在700 hPa及以上高度,为暴雪的形成提供了动力和水汽条件,850 hPa以下为冷垫,850～700 hPa存在逆温, 850 hPa气温小于等于-4 ℃、2 m气温小于等于3 ℃时降雨向降雪转变,地表温度接近零度后积雪增长明显；(4)南通地区24 h平均SLR,纯雪过程≥10,雨转雪过程＜10、东南部＜ 5,一般可通过850 hPa、2 m气温及地表温度对降水相态转换和SLR做出预判；(5)从历史强降雪中寻找天气形势相似过程,对比层结、动力和水汽条件,然后对相似过程实况进行缩放来推断降水量和积雪深度,也是一种可行的方法。     

FEM Analysis of Stress Distribution Law in the Rocksalt Cavity''s Surrounding Rock

Basic on the FEM numerical analysis, the contour maps stress of rocksalt cavity's surrounding rock and the major principal stress's law changed with the depth and horizontal direction are analyzed. The influencing factors to the distribution of the stress surrounding rocksalt cavity, such as cavity's span, water pressure and the depth of rocksalt layer is also studied. The results show that major principal stress becomes big with the increase of rocksalt's depth. The cavity's influence to the stress's distribution will be clearer with the nearer to the cavity. The stress's centralization will be weaker with the accretion of water pressure in rocksalt's cavity. But the stress's centralization will be stronger, and the stress's value increases.     

Experimental analysis of coal bed methane desorption and seepage under sonic vibrating of cavitation water jets

A way to enhance coal bed methane desorption and seepage by sonic vibrating of cavitataion water jets is proposed because the gas coal seams have the intrinsic properties of micro-porosity, low permeability and high adsorption. The mechanisms of how the sonic vibrating effects promote methane desorption and seepage are analyzed, and the contrast experiments of methane desorption and seepage under sonic vibrating effects are also provided. The results show: when the cavitation number is 0.020 0, under sonic vibrating effects, the volume of coal bed methane desorption increases by 36.9%, and the time for coal bed methane desorption reduces by 19.6%. The speed of coal seams methane seepage is significantly increased by 35.3% and arrives at 0.383 3 ml/s.     

Mathematical Model and Operation Analysis of Semi-submerged Rotary Orifice Sewage Source Heat Pump Intake Machine

To solve the flow instability and adjustment difficulty of filtering dirt-removing device in the sewage source heat pump system, which affect the efficiency of heat exchanger, semi-flooded rotary orifice sewage auto-strainer was generated. According to establishing the mathematical model, the effect is analysed of pollutant concentration and liquid level height of sewage and rotation period of orifice plate to filtered flow rate, filtered load and filtering surface block coefficient. The result shows that: in the certain condition of sewage liquid level height and orifice plate rotation period, the increase of sewage will decrease the filtered flow rate of orifice plate, and increase filtering surface block coefficient; The effect of pollutant concentration change in the sewage to orifice plate filtered flow rate could be adjusted by regulating the sewage liquid level height and orifice plate rotation period, and the moderating effect of orifice plate rotation period is better than that of sewage liquid level height.     

Simulation of thermocapillary flow in a two dimensional cavity with lattice Boltzmann method

Thermocapillary flow driven by an unbalanced surface tension plays the most important role for mass and heat transport in floating zone melt crystal growth under microgravity. The authors develop both a serial and a parallel codes with lattice Bhatnagar-Gross-Krook(BGK) model using two distribution functions, and numerically study the thermocapillary flow in a two dimensional square cavity with a single free surface under microgravity condition. The serial code is developed by combining collision and propagation step, using a temporary array to continuously read distribution functions, and its performance is improved two times faster than the code with separating the collision and propagation step. The MPI parallel code is proposed utilizing one dimensional partitioning and non-blocking communication. The accurate and reliable results are achieved with both the serial and parallel codes by comparing with CFD results simulated by the finite volume method; the MPI parallel code has high performance.     

浅埋式滴灌湿润锋发展规律试验研究

(目的)研究旨在根据苜蓿浅埋式滴灌的发展需求,针对滴头埋深、流量等因素对滴灌湿润体发展的影响规律开展了室内试验研究。(方法)利用新疆阿勒泰地区青河县阿苇灌区苜蓿浅埋式滴灌试验区的沙壤土对不同滴头埋深和流量,开展浅埋式滴灌条件下土壤湿润锋的发展过程、湿润锋特征值变化等的试验。设置了5 cm、10 cm、15cm共3个滴头埋深处理,滴灌流量控制在0.8L/h-2.5 L/h不等。(结果)结果表明,不同埋深不同流量下零通量面湿润锋形状近似为椭圆;湿润锋的水平、垂向运移距离分别随入渗时间的增长而增大且均与入渗时间呈幂函数关系;湿润锋水平、垂向运移距离的比值随滴头埋深增加而增大;湿润锋水平纵向运移距离随垂向深度增加呈现先增后减的趋势,纵向运移距离与垂向深度呈二次函数关系。(结论)上述结果对于浅埋式滴灌参数设计具有参考价值。     

Dropwise Condensation Heat Transfer Coefficient on the Horizontal Circular Surface with Radial Gradient Surface Energy

A theoretical model is developed for the dropwise condensation heat transfer on the horizontal circular surface with radial gradient surface energy based on the heat transfer model of individual condensate drop and the size distribution model of condensate drop on homogeneous condensation surface.The effect of variation of contact angle on the gradient surface on condensation heat transfer and condensate drop size distribution is taken account of in this model.The theoretical calculation method was obtained to predict the dropwise condensation heat transfer coefficient on the horizontal circular surface with radial gradient surface energy under various wall subcooled temperature,contact angle profile on wall surface,and working fluid.The effects of surface energy gradient,wall subcooled temperature,and thermophysical properties of condensate on the condensation heat transfer are discussed respectively.The calculation results show that the condensation heat transfer coefficient increases slightly with the increase of wall subcooled temperature.As latent heat and surface tension increasing,the condensation heat transfer coefficient increases.A larger surface energy gradient induces a larger condensation heat transfer coefficient.     

Subway Station Plate Evaporative Cooler Heat and Mass Transfer of Falling Film under Gas liquid Cross flow Condition

With the influence of the different gas Reynolds number and liquid Reynolds number on falling film heat and mass transfer of subway station plate evaporative cooler, the experiment was carried out by non contact infrared thermal imaging technology under gas liquid cross flow condition. The results indicated that during the increasing of liquid Reynolds number the thickness of liquid film increased and the temperature difference between liquid film inlet and outlet decreased in determined heating water temperature which weakened the heat transfer of liquid film. However, the increase of liquid Reynolds number strengthened the liquid film turbulence that enhanced heat transfer. Under the synergistic effect of these two factors, there was an optimal liquid Reynolds number which minimize thermal resistance and maximize heat and mass transfer coefficient of liquid film.     

Numerical Simulation Research on Stabilityof Dissolving Cavityfor the Low-depth-thin-layer Rock Salt

In order to extend life of salt well, avoid sinking and use the formed cavity reasonably, the factors of effecton cavity stability must be researched during the process of water mining of rock salt, so that the effective prevention measures can be put. The stability of dissolving cavity for the low depth thin layer rock salt has been researched by the ADINA non linear finite element method.The results show that the stability of dissolving cavity obviously becomes strengthened with the decrease of its height, and has a decreasing trendas with the span increase of the cavity . The effect of incidence on stability of the cavity is very little. The stability of cylindroid cavity is higher than that of converse taper cavity. The assorted model is a kind of transition shape. The influencing order of cavity stability is the ffollows, height>geometrical shape>span>incidence.     

Analysis and numerical simulation of fluid-structure coupling of gas drainage from boreholes

Gas drainage from boreholes is main method of utilization and management of Chinese coal seam gas. As the exploitation depth increases, stress field and other factors on the impact of gas seepage are increasingly apparent. Based on the basis of a series of assumptions of coal seam gas, porosity and permeability equations are described by considering stress, coal seam gas pressure change on the coal produced by deformation of the skeleton. The fluid-structure coupling equations are derived by using the basic theorem of porous media flow and the fluid structure coupling theory. The gas seepage field is simulated and analyzed by using multi-physics coupling analysis software. The effect of gas pressure distribution, different burial depths and different drilling parameters (drainage negative pressure, drilling radius) on gas seepage field is obtained. Analysis of simulation results can provide theoretical guidance for on-site gas drainage.     

Research of Flow Characteristics of Multi-jets in the Same Direction and in Great Velocitv Difference in Combustion Chamber

The flow characteristics of multi-jes in the same direction and in great velocitydifference in combustion chamber were researched by the cold mould simulating test of self-designedlow- calorie value gas burner.The results showed that the large negative pressure region and back-flow region would be produced by the multi-annular jets with high-velocity air involve intensivelythe central low-velocity gas jet and by virtue of the small main air volume resulting by some extentcirculation of gas jet.These have the advantage of realising homogeneously mixing between air jetsand gas jet and combusting steadily.     

A calculation method for coalbed permeability by using drainage data

In order to more accurately calculate the changes in the permeability of coalbed during production process, a calculation method for coalbed permeability based on production data is established by combining with material balance equations and production equations, and it gives the fact that the output data can be a good reflection of the inner permeability of coalbed. The average pressure of coalbed in production process can be calculated through material balance equation. Dimensionless water production index is introduced into the production equation in the stage only with water production. In the next stage with both gas and water, gas and water production ratio is introduced to eliminate the influence of flush-flow radius, skin factor as well as other uncertain factors on the calculation of CBM permeability. The relationship between permeability and surface cumulative liquid production can be described as a single-variable cubic equation by derivation. There is a trend that the permeability declines firstly and then increases after wells in Qinshui CBM field are calculated. The results show that reservoir permeability increase after drainage stage, but the growth rate decrease gradually. The regression result of the permeability ratio and surface cumulative fluid production agrees with the theoretical mathematic relationship.