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1.
The effects of cavitation and abrasive acceleration in the self excited oscillation pulsed abrasive water jets are directly determined by its oscillating frequencies, so the wave speed in the jets and its effects on pulsed frequencies are discussed. The numerical results show that the oscillating frequencies of the jets increase obviously with decreasing wave speed, and the abrasive parameters have almost no effects on the wave speed, whereas the exit of air in fluid has significant consequences on the wave speed.It was found that these conclusions were applicable for design the nozzle of the jets. 相似文献
2.
This paper theoretically investigates the characteristics of cavitating bubbles in the pulsed abrasive water jet(PAWJ) and establishes the dynamic equations of cavitating bubbles. The effects of abrasive diameter and density on the spherical bubble collapse are also analyzed. It is found that the change of abrasive diameter rarely affects the bubble collapse when the abrasive diameter and density are small whereas the smaller abrasive greatly blocks the bubble collapse when the abrasive diameter and density are comparably big. It is also shown that when the abrasive density is increased, the fluid viscosity rises, and the kinetic energy of the abrasives near the collapsed bubble is enhanced and meanwhile the intensity of cavitating erosion is weakened. 相似文献
3.
The relationship between abrasive concentration, length of oscillating chamber, standoff distance and cutting depth, erosion rate as well as cutting specific energy was investigated by experiments in the submerge and surface conditions. The cutting and erosion capabilities of the pre-mixed abrasive water jet and the pulsed abrasive water jet were analyzed in contrast. It is shown that the maximum cutting depth and erosion rate of the pulsed abrasive water jet are respectively 1.67,1.72 and 1.39, 1.47 than the pre-mixed abrasive water jet in submerge and surface conditions. These results attained from the research are useful to increase the cutting efficiency, decrease the energy ratio and expand the application domains of the abrasive water jet. 相似文献
4.
The cutting property is studied with the grey theory and method for the premixed abrasive water jet.The relationship between the primary and secondary is obtained about the cutting specific energy influenced by pressure,the standoff distance,the abrasive concentration and transverse velocity.The guidance is provided for further research and pratical application. 相似文献
5.
前混合磨料射流超强的打击力主要是由高速磨料群提供的,因此,磨料速度测试是磨料打击力分布规律等研究的基础。针对传统研究方法的不足之处,笔者提出采用PIV技术结合自主编程设计的磨料中心识别程序,实现非接触式测试手段下磨料速度测试实验研究,并利用该方法简要分析了喷嘴结构对磨料速度的影响。结果表明,在一定范围内增加直线段长度有利于提高喷嘴出口处磨料的速度,表明在喷嘴直线段末端磨料依然处于明显的加速状态;增加收敛段长度对提高喷嘴出口处磨料速度有一定的作用,但磨料速度增幅不大;收敛角较大时,液相在收敛段前半段加速缓慢而在后半段过于剧烈,因磨料颗粒加速滞后于液相的原因导致喷嘴出口处磨料速度降低。 相似文献
6.
水体营养水平对3种沉水植物吸收磷的影响 总被引：2，自引：1，他引：1
为了研究太湖3种沉水植物对磷的吸收特性,在室内模拟条件下,研究了3种沉水植物轮叶黑藻、金鱼藻和伊乐藻在寡、富和超富3种营养水平条件下和不同光照条件下对无机磷吸收效果的影响。结果表明：在自然光照条件下,3种沉水植物对不同营养水平水体中活性磷均有一定的去除能力,且3种沉水植物间的去除能力具有一定的差异,去除能力表现为：金鱼藻>轮叶黑藻>伊乐藻;同种植物在不同营养水平下,去除磷能力不同,轮叶黑藻和伊乐藻在寡营养水质下对活性磷去除效果最强,不同营养水质下活性磷的去除能力表现为：寡营养>富营养>超富营养;而金鱼藻的去除能力表现为：富营养>寡营养>超富营养。与自然光照条件比较而言,3种沉水植物对活性磷的吸收作用能力减弱,这表明光照影响3种沉水植物对活性磷的吸收。 相似文献
7.
The stainless steel has excellent properties, but it is difficult-to-grind material. Because belt grinding shows many advantages, grinding experiments with four kinds of abrasive grain on stainless steel are carried out. The correlation mechanism between the abrasive grits and the workpiece, and influence factors on material removal rate are discussed. A scanning electric microscope was used to investigate the surface micro-shape characteristics of abrasive grit and workface. The material removal mechanism and the wearing types of abrasive belt are also analyzed. 相似文献
8.
The cavity induced by top-blow gas jets impinging on the bath surface is one of most important parameters, which has overwhelming influence on the rate of slag formation and metallurgical performance. Water model experiments are conducted through a 1/10 scaled-down top-blown convertor. Effects of lance height and gas flow rate on penetration behavior are studied, and also the influence mechanism of liquid surface tension on penetration depth is addressed based on the experiments and theory analysis. An energy utilization index (EUI) is defined to reflect how much the impinging kinetic energy of gas jets are transferred into bath for formation of cavity, and an improved model is proposed to predict penetration depth of jets. The results show that penetration depth increases with lowering lance height and increasing gas flow rate, and impact diameter increases with increasing lance height, but is little affected by gas flow rate. Influence of liquid surface tension on penetration depth is enhanced with increasing surface tension and penetration depth. The EUI increases with increasing lance height, and a function relationship of it with lance height is obtained based on the experiments. 相似文献
9.
In view of the process characteristics of thin slab casting with a vertical-arcmould and super thin submerged nozzles, the fluid flow laws in a mould and in scarch of reasonablesu bmerged nozzle patterns have been physieally simulated. The fluid flow states of several typiealnozzleS in moulds were studied through water model experimen ts. The shape and dimensions of asuitable submerged nozzle have heen optimized for industry trials. 相似文献
10.
不同灌水方式对水稻生育特性及水分利用率的影响 总被引：5，自引：2，他引：5
以冈优527、D优363、汕优63为材料,设4个不同水分灌溉方式,研究了不同灌溉方式下水稻生育特性、产量和水分利用率。结果表明:与淹水灌溉相比,湿润灌溉(前期) 浅水灌溉(孕穗期) 干湿交替灌溉(抽穗-成熟期)的灌溉方式,可促进叶片和根系生长,剑叶叶绿素含量和净光合速率高,有利于干物质积累;植株生理活动旺盛;其有效穗、结实率、千粒重、产量和水分利用率均高于淹水灌溉。湿润灌溉有利于根系生长,延缓根系和叶的衰老;产量和水分利用率比淹水灌溉略高。旱种抑制水稻根系生长和地上部干物质积累,产量和水分利用率比淹水灌溉显著降低。因此,湿润灌溉(前期) 浅水灌溉(孕穗期) 干湿交替灌溉(抽穗-成熟期)的灌溉方式更有利于稻株生长发育、产量和水分利用率的提高。冈优527、D优363的水分利用率显著高于汕优63。 相似文献
11.
Aiming at the status quote of long time for methane extraction and slow speed for laneway excavating in coal seams of Liziya south 2JHJ well, abrasive water jet slotting technology is adopted to improve the methane desorption and increase excavating speed in semi-coal laneway. Through analyzing damage model and protection against outburst mechanism, the process of Coal-Rock Mass being cut and fractured is studied. Through lab test on abrasive water jet cutting coal-bed gangue, a new abrasive water jet cutting device is successfully designed and made and all parameters are determined. It is showed that abrasive water jet can cut through a coal-bed gangue with thickness 60~80 mm and uniaxial compressive strength 62 MPa. After cutting coal seams by abrasive water jet, the surface area for methane is enlarged and then coal seams pressure fell rapidly. Therefore the permeability and desorption of coal seams are greatly increased. The results are as follows: the average productivity of single-hole was enhanced by 2.83 times. 相似文献
12.
Experimental analysis of abrasive belt grinding of glass fiber reinforced plastic composite material
Abrasive belt grinding experiments of glass fiber reinforced plastics composite material are carried out by using three different abrasive belts with different sizes,and the interaction principle between the abrasive and the workpiece is analyzed.The main factors of material removal rate and belt life of glass fiber reinforced plastics composite material are obtained through a large number of tests and test data.The extent and the main reason of belt plug are analyzed through the professional image analysis software (Image Pro Plus) for the first time.The results show that in the process of abrasive belt grinding,the material removal rate are affected by the factors for grinding pressure,belt speed,abrasive type and size,and the ceramic abrasive belt has the highest removal rate.The main factor for belt plug extent is grinding pressure.The most important wear form of abrasive belt is blunt,and the accumulation abrasive belt has the longest life,followed by ceramic abrasive belt. 相似文献
13.
[目的]为了在进行滨海及盐碱地湿地修复时筛选出耐盐的沉水植物,本文研究了六种常用沉水植物,苦草、轮叶黑藻、金鱼藻、穗花狐尾藻、篦齿眼子菜、小茨藻的耐盐性及四项生理指标。[方法]在室内模拟条件下,分别用不同浓度的NaCl溶液对六种沉水植物进行盐分胁迫,每周进行盐害症状的观测,并测定叶片叶绿素a、叶绿素b、脯氨酸、可溶性蛋白及丙二醛的含量。[结果]结果表明,在六种沉水植物中,耐盐性为小茨藻>篦齿眼子菜>金鱼藻>苦草、轮叶黑藻>穗花狐尾藻。其中小茨藻和篦齿眼子菜能在盐度为15‰和8‰的盐胁迫条件下存活。金鱼藻的最高耐受盐度为6‰,苦草和轮叶黑藻的盐度胁迫能力较弱均为4‰,穗花狐尾藻的盐度胁迫能力最弱,仅为2‰。[结论]该实验为沿海及盐碱化地区的水生态系统修复提供理论依据,为项目工程实践及沉水植物的抗盐生理学研究奠定基础。 相似文献
14.
Present main method of organic wastewater treatment are physico- chemical method, biochemical method and combination method, but there are many problems need to be resolved, such as organic matter can not be treated thoroughly, fee is high, and operation is complicated. Cavitation jets is a efficient and simple new technology on organic wastewater treatment. It use local high temperature and high pressure produced bubbles collapse to degrade organic matter, and it is better in capacity usage ratio than ultrasonic cavitation. Principle of eavitating jets is giuen, then discussed mechanism of organic wastewater treatment by cavitating jets from free radical reaction, direct thermal decomposition and supereritieal water oxidation, and influence of nozzle stricture is analyzed, jet cavitation number, pumping pressure, confining pressure and physieoehemieal property of organic wastewater on cavitation effect. 相似文献
15.
A mono-liquid model is established according to formative character of the premixed abrasive water jet. The hydraulic structure is analyzed by the model. The relationship that is obtained between the axial shaft line velocity and the forget distance by the law of conservation of momentum is verified with the experiment. 相似文献
16.
On the base of the summarizing the relative researches, the complicated chemical effects of cavitating water jet, direct pyrogenation, free radicel oxidation and supercritical water oxidation, are investigated, which the local and instantaneous high temperature and pressure is generated as the bubbles in cavitating water jets collapse. The ranges of chemical reaction as the bubble collapses are divided. The affected factors of the chemical effects of cavitating water jets are discussed. 相似文献
17.
Stress wave effect in numerical simulation on rock breaking under high pressure water jet 总被引：1，自引：0，他引：1
The evolvement of rock damage struck by a high pressure water jet is characterized by nonlinear properties, thus making it a complicated dynamic problem. Based on a nonlinear finite element and elastic plasticity theory, a computational model was established. The dynamic load striking the rock by a high pressure water jet was simulated by the dynamic contact method. Furthermore, the propagation of a stress wave in the same rock was simulated at different impact velocities. The results show that the propagation velocity of a stress wave is proportional to the impact velocity of the high pressure water jet. The effects of a stress wave in sandstone and coal impacted by high pressure water jets of the same velocity were simulated.The effect of a stress wave in coal was stronger than in sandstone, while the region of propagation of stress wave in coal was smaller. 相似文献
18.
Experimental analysis of the abrasive belt follow-up grinding of Zirconium-4 alloys tubes and pipes 总被引：1，自引：1，他引：0
Abrasive belt grinding experiments of Zr-4 nuclear power tube are carried out by using three different abrasive belts with same size, and the interactive generating mechanism between abrasive and workpiece is analyzed, the main factors of material removal rate and surface roughness of Zr-4 alloys are obtained. With the help of the advanced test facilities, the abrasive grain abrasion and surface topography of the workpiece are observed. The metallographic structure and microhardness of the layer of burnt surface during Zr-4 alloys Grinding are analyzed. Some conclusions are given as follows: the material removal rate and surface roughness are mainly affected by the factors of belt speed, grinding pressure, hardness of the contact wheel and abrasive type, of which, the belt speed is the strongest factor. The adhesion wear of the Zirconium corundum and aluminium oxide abrasive grit is more serious, the most important wear form of silicon carbide is abrasion wear. With the onset of grinding burn, the mechanical properties of Zr-4 alloys are deteriorated obviously. The results provide a theoretical and experimental basis for technical optimization in the grinding of Zr-4 alloys with efficiency and high quality. 相似文献
19.
Cavitating water jets were used to degrade complicated organic compounds sampled from landfill leachate from a sanitary landfill in Chongqing, P. R. China. The law of chemical oxygen demand (COD) and the impact of factors such as pumping pressure, confining pressure, cavitating time and pH were evaluated in the experiment. We concluded that a cavitating water jet can degrade complicated organic compounds. Cavitating water jets therefore can improve biological oxygen demand (BOD)5/COD. The optimal cavitating condition was also obtained: at a pH 9.0, confining pressure 0.6MPa, cavitating time 90mins and pumping pressure 10MPa,the COD, BOD5 and BOD5/COD increase to 124.8%, 293.3% and 52.44% respectively. Chromaticity decreases while SS increase to 191.5%. These changes create good conditions for subsequent treatment. 相似文献
20.
On the base of non equilibrium thermodynamic theory and phase equilibrium principle, the physical mechanism of surface water evaporation and vapor diffusion is analyzed in the convective drying of porous material, and the thermodynamic condition of convective drying process is established. A new driving potential of water evaporation and vapor diffusion is set up and the effect of the drying medium temperature and humidity on the driving potential is discussed. 相似文献