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Experimental Study on High Electrical Breakdown of Water Dielectric
By means of a coaxial apparatus, pressurized water breakdown experiments with microsecond charging have been carried out with different surface roughness of electrodes and different ethylene glycol concentrations of ethylene glycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows: (1) the breakdown stress formula is modified to E = 0.561MA-1/10t-1eff/NP1/8; (2)the coefficient M is significantly increased by surface polishing and ethylene glycol additive; (3) it is accumulative for the capacity of improving electrical breakdown strength for surface polishing,ethylene glycol additive, and pressurization, of which pressurization is the most effective method;(4) the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; (5) for pressurization and surface pohshing,the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric....
2020-07-08 08:49:41浏览：34
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Timing of advanced water flooding in low permeability reservoirs
It is very important to design the optimum starting time of water injection for the development of low permeability res-ervoirs. In this type of reservoir the starting time of water injection will be affected by a reservoir pressure-sensitive effect. In order to optimize the starting time of water injection in low permeability reservoirs, this effect of pressure change on rock permeability of low permeability reservoirs was, at first, studied by physical simulation. It was shown that the rock permeability decreases expo-nentially with an increase in formation pressure. Secondly, we conducted a reservoir engineering study, from which we obtained analytic relationships between formation pressure, oil production rate, water production rate and water injection rate. After our physical, theoretical and economical analyses, we proposed an approach which takes the pressure-sensitive effect into consideration and designed the optimum starting time of water injection, based on the principle of material balance. Finally, the corresponding software was developed and applied to one block of the Jiangsu Oilfield. It is shown that water injection, in advance of production, can decrease the adverse impact of the pressure-sensitive effect on low permeability reservoir development. A water-flooding pro-ject should be preferably initiated in advance of production for no more than one year and the optimum ratio of formation pressure to initial formation pressure should be maintained at a level between 1.05 and 1.2....
2020-07-08 08:49:41浏览：32
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States of Water in Hydrogels Containing with Glyceryl Methacrylate
Hydrogel materials were prepared by thermopolymerization with different content of glyceryl methacrylate and hydroxyethyl methacrylate. The different states of water in swelling hydrogels were described and studied by differential scanning calorimetry (DSC). It was found that the hydrophilicity of GMA was stronger than HEMA, the water content and bound water of GMA hydrogel are higher than HEMA hydrogel. With the increase of GMA content, the content of free water in hydrogel increased. When GMA content was lower than 50%, the increase of GMA content also increased the content of bound water; but when GMA content was higher than 50%, the increase of GMA content decreased the content of bound water, which was caused by the chain hydrogen bond formed on the GMA chain with hydroxyl group each other....
2020-07-08 08:49:41浏览：52
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Formation and utilization of water resources of Tarim River
The Tarim River is a typical inland river in arid area without runoff yield of itself, and water resources are all supplied by its headstreams. The method of time series analysis is applied to annual runoff series of three headstreams, namely the Aksu River, Yarkant River and Hotan River to analyze their dynamic variations. A model is established to estimate water consumption in the headstream areas. Quantitative results indicate that both total annual runoff of headstreams and water consumption in the headstream areas have an increasing trend. The dynamic trends of annual runoff of hydrologic stations along the mainstream of the Tarim River are also presented to estimate the intermittence drying-up time at each station. Water consumption model of the mainstream area is used to analyze the characteristics of water consumption in the upper and middle reaches. It is shown that water consumption in each river reach of the mainstream decreases with the decrement of inflow and increases with human activities....
2020-07-08 08:49:41浏览：63
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PRESSURE OF WATER SHORTAGE ON AGRICULTURE IN ARID REGION OF CHINA
The arid areas in China are mainly located in North China and Northwest China. The North China is themain region for food production. There is 31.19% of the total farmland and 26. 01% of the total population, but only6. 14% of the available water resources of China. Groundwater is over pumped (6. 53 × 109m3 every year) in the regionsof Beijing, Tianjin, and Hebei Province, so water supply could not meet the water demand there. The distribution of wa-ter in Northwest China is uneven, some inland rivers and lakes are dried up, and desertification has expanded since riverwater in the upper and middle reaches is diverted for irrigation. Up to 2050, population will be up to 1.6 × 109 in Chi-na, and industry will be developed fast, therefore 50% of the water supply will be used by industry and resident, andwater for agriculture will be decreased year by year. In the coming 50 years, water demand for agriculture will be in-creased by 5.6 × 109m3 in the Huanghe (Yellow) River valley, and by 1.7 × 109m3 in the Northwest China. It will beimpossible for the Huanghe River to meet the water demand, because it always dried up in the cold half year since 1984.To avoid water shortage of agriculture in the arid regions, it is necessary to divert water from the Changjiang (Yangtze)River in the south of China, and to use water efficiently. It is the best way to use drip irrigation in agriculture, recyclewater in industry and resident use, and control water pollution. Otherwise water shortage in the arid regions will restrictthe development of agriculture in China....
2020-07-08 08:49:41浏览：53
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Quantificational analysis on progress of river water quality in China
In order to understand the dynamic change of water quality in a specific period of time,a type of possibility transition matrix based on the theory of Markov process was established.The transition possibility with a weight to calculate the degree of absolute advancement was given based on the result of water quality evaluation,the concept of relative advancement was presented.It was used to evaluate the extent of water quality changed in a period of time.The method was used to calculate the degrees of relative advancement for 4 rivers in China,and the results were analyzed....
2020-07-08 08:49:41浏览：30
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Testing and Analysis of the Speed of Water Jet in Water Jet Looms
In the water jet looms, the distribution of the speed of water jet at the axis of the shed and its regularity are obtained by the Laser Doppler Tester. Based on the above, the water jet system is analyzed and the main effective approaches to increase the filling insertion rate and to widen the reed space of the loom are pointed out....
2020-07-08 08:49:41浏览：40
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GSP气化煤粉输送问题及优化措施
为了实现GSP干煤粉气化工业装置煤粉密相输送系统的稳定输送,对锁斗与发料罐容积、锁斗阀、搅拌器、煤粉管线、疏松元件等影响煤粉稳定输送的因素进行研究.结果表明,通过调整锁斗疏松气标准状态下体积流量为900～1 200 m3/h,在疏松气管线上设置旁路,下料阀中设置吹扫气,发科罐上安装连续料位计,以及对发料罐中的煤粉管线进行固定,输送元件的布气板厚度增加2～3 mm,控制金属丝网孔隙为260 μm,实现了煤粉密相输送系统质量流量波动幅度小于5％....
2020-07-04 21:56:39浏览：1397
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论《内经》气化学说?
基于“气化”一词的本义，及其在《内经》中的涵义，提出《内经》中“气化”主体是指天地之气化的观点，气化是从气一元论的自然哲学思想认识人体生命时延伸出的重要学术范畴。《内经》气化思想主要包含天地之气化生万物，天地气化涵盖人体气化两方面内容，气化具有时序性、方位性和内部自稳性的特征。气化学说对临床有重要的指导作用。...
2020-06-12 16:20:27浏览：1398
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Effect of Mild-calcined Coal Gangue Addition on Hot Strength and Refractoriness Under Load of Ultra
This work explored the way to improve hot modulus of rupture (HMOR) and refractoriness under load ( RUL ) by adding mild-calcined coal gangue ( MCG )in Al203 - SiO2 ultra low cement (ULC) castables,making use of the in-situ effect of the MCG during heating-up.The influence of respective additions of 5％,10％ and 15％ of the MCG powders calcined at 700 ℃was investigated on HMOR at 1 400 ℃ and RUL of the castables.With increased addition of the MCG,HMOR and RUL become significantly enhanced.At 10％ of the MCG addition,HMOR reaches 3 MPa,as compared to 0.3 MPa in the case of no MCG addition.RUL of the specimens dried at 110 ℃ for 24 h can be increased by some 270 ℃ with 10％ of the MCG addition.RUL of the specimens preheated at 1 500 ℃ for 3 h maintaius the growth trend with the MCG addition increasing.The microstructure of the heated castable samples was investigated by means of SEM.The in-situ formed needle-like and interlaced mullite in the matrix is contributive to the improvement....
2020-06-12 16:19:59浏览：1418
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Prediction of oxygen concentration and temperature distribution in loose coal based on B P neural ne
An effective method for preventing spontaneous combustion of coal stockpiles on the ground is to control the air-flow in loose coal. In order to determine and predict accurately oxygen concentrations and temperatures within coal stockpiles, it is vital to obtain information of self-heating conditions and tendencies of spontaneous coal combustion. For laboratory conditions, we de-signed our own experimental equipment composed of a control-heating system, a coal column and an oxygen concentration and temperature monitoring system, for simulation of spontaneous combustion of block coal (13-25 ram) covered with fine coal (0-3 mm). A BP artificial neural network (ANN) with 150 training samples was gradually established over the course of our experiment. Heating time, relative position of measuring points, the ratio of fine coal thickness, artificial density, voidage and activation energy were selected as input variables and oxygen concentration and temperature of coal column as output variables. Then our trained network was applied to predict the trend on the untried experimental data. The results show that the oxygen concentration in the coal column could be reduced below the minimum still able to induce spontaneous combustion of coal-6% by covering the coal pile with fine coal, which would meet the requirement to prevent spontaneous combustion of coal stockpiles. Based on the predic-tion of this ANN, the average errors of oxygen concentration and temperature were respectively 0.5% and 7 ~C, which meet actual tolerances. The implementation of the method would provide a practical guide in understanding the course of self-heating and spontaneous combustion of coal stockpiles....
2020-06-12 16:19:45浏览：1437
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Rock parameters inversion for estimating the maximum heights of two failure zones in overburden stra
In order to enter effective parameters of rock mass in a numerical model, the relationships between mechanical parameters of rock and rock mass were obtained by an inversion method and an orthogonal test, given our measurements of the maximum heights of two failure zones in the Longdong coal mine.Using the maximum heights of the caving zone and the water-conducting fractured zone as test indices the modulus of elasticity, the Poisson ratio, cohesion and tension strength as test factors and different values of reduction enhancement factors as test levels, an orthogonal test was designed to obtain an optimum simulation scheme. From the analysis of different values of reduction enhancement factors which affect the test indices, an optimum factor combination for modification of parameters could be inferred. By using modified parameters in our numerical simulation, the maximum heights oftbe caving zone and the water-conducting fractured zone in the extensive Xiyi area were determined as 15.06 m and 36.92 m. These values were almost the same as those obtained by similar material simulation (8.5 m and 37.0 m) and empirical prediction (8.4 m and 34.4 m). These results indicate that the modification of parameters is a rational method....
2020-06-12 16:19:23浏览：1426
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Principle and engineering application of pressure relief gas drainage in low permeability outburst c
With the increase in mining depth, the danger of coal and gas outbursts increases. In order to drain coal gas effectively and to eliminate the risk of coal and gas outbursts, we used a specific number of penetration boreholes for draining of pressure relief gas. Based on the principle of overlying strata movement, deformation and pressure relief, a good effect of gas drainage was obtained. The practice in the Panyi coal mine has shown that, after mining the Cllcoal seam as the protective layer, the relative expansion deformation value of the protected layer C13 reached 2.63%, The permeability coefficient increased 2880 times, the gas drainage rate of the C13 coal seam increased to more than 60%, the amount of gas was reduced from 13.0 to 5.2 m3/t and the gas pressure declined from 4.4 to 0.4 MPa, which caused the danger the outbursts in the coal seams to be eliminated. The result was that we achieved a safe and highly efficient mining operation of the C 13 coal seam....
2020-06-12 16:19:02浏览：1399
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Analysis of the Harmfulness of Water-Inrush from Coal Seam Floor Based on Seepage Instability Theory
A theory of seepage instability was used to estimate the harmfulness of water-inrush from a coal seam floor in a particular coal mine of the Mining Group, Xuzhou.Based on the stratum column chart in this coal mine, the distribution of stress in mining floors when the long-wall mining was respectively pushed along to 100 m and to 150 m was simulated by using the numerical software (RFPA2D).The permeability parameters of the coal seam floor are described given the relationship between permeability parameters.Strain and the water-inrush-indices were calculated.The water-inrush-index was 67.2% when the working face was pushed to 100 m, showing that water-inrush is possible and it was 1630% when the working face was pushed to 150 m, showing that water-inrush is quite probable.The results show that as long-wall mining is pushed along, the failure zone is enlarged, the strain increased, and fissures developed correspondingly, resulting in the formation of water-inrush channels.Accompanied by the failure of the strata, the permeability increased exponentially.In contrast, the non-Darcy flow β factor and the acceleration coefficient decreased exponentially, while the increase in the water-inrush-index was nearly exponential and the harmfulness of water-inrush in the coal mine increased accordingly....
2020-06-12 16:18:35浏览：1411
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