磨料水射流切割质量研究

对磨料水射流的切割质量进行了试验研究,通过改变水射流压力、切割进给速度来研究切割断面质量,对AWJ切割机理和切割过程进行了分析,探讨了AWJ切割断面的形貌特征及其形成机理,认为是射流断面磨料动能的分布不均和射流的偏转滞后造成了AWJ切割断面斜条纹和曲线及尖角处的尖端,提出了两种提高磨料水射流切割质量的方法。     

Effect of Main Parameters on Cutting of the Pulsed Abrasive Water Jet

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.     

Mechanism analysis of permeability based on promoting coal matrix shrinkage by water jet

High pressure pulsed water jet (HPWJ) is a new technology of effectively improving coal seam permeability. However, the mechanism of increased permeability is not yet clear, which restricts the application of HPWJ in different coal seams. From the perspective of improving permeability by coal matrix shrinkage, the impelled dynamic equations is established based on analysis of coal dynamic effects by water jet. According to theoretical analysis of the stress state of coal matrix, it is concluded that HPWJ can promote coal matrix shrinkage, and the relationship equation between jet impact-coal matrix is derived. Besides, the gas seepage function in the coal slotted by the HPWJ is gained by using PM model, which provides theoretical support for generalizing the technology in the coal mine.     

固定顶储罐液下喷射泡沫灭火技术

与液上喷射泡沫灭火系统的相比，液下喷射泡沫灭火系统具有安全可靠，灭火速度快，省投资等优点，但却存在单阀易渗漏问题。针对这一问题，提出了通过在单向阀和控制阀之间增设爆破片，或在灭火系统泡沫喷口处设置泡沫带以及改善单向阀密封性能等解决办法。     

发动机尾气射流特性研究

利用高速摄影仪实时拍摄发动机尾气的射流运动过程,通过Im age-Pro6.3专业图像处理软件,选择气体射流顶点为研究对象,根据自由射流理论,得到发动机尾气贯穿距离、射流锥角、射流速度随射流时间变化的规律。结果表明:尾气射流分为两个阶段,射流起始段和射流主体段。当发动机转速一定时,在整个射流过程中,射流贯穿距离随射流时间的增加而增加,射流锥角基本保持不变,射流速度随射流时间的增加而减小;当发动机转速提高时,射流贯穿距离、射流速度均有所减小,而射流锥角增大。在此基础上,确定了射流贯穿距离与射流速度之间的数学模型。     

Theoretically Investigation of Dynamic Characteristics of Spherical Bubble Collapse in Pulsed Abrasive Water Jet

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.     

MAGNETIC RESONANCE IMAGING FEATURES OF CERVICAL SPINAL CORD MENINGIOMAS

The records of four dogs with cervical spinal cord meningiomas were retrospectively reviewed. Signalment, history, laboratory findings, neurological examination, and histopathological findings were evaluated. Magnetic resonance imaging (MRI) was performed using a 1.0-T superconducting magnet and T2-weighted (W) and noncontrast and postcontrast T1-W spin echo pulse sequences. Meningiomas were located at the level of the second, third, and fifth cervical vertebrae and the C2-3 intervertebral space. All meningiomas appeared as focal masses that were hyperintense to the spinal cord on T2-W images and iso- to hypointense on the T1-W images. They could be identified as intradural and extramedullary in origin based on a broad-based dural margin seen on at least one of the imaging planes and a gradual expansion of the subarachnoid space cranial and caudal to the mass, best noted on the transverse and dorsal plane images. On dorsal plane T2-W images in three dogs, expansion of the subarachnoid space adjacent to the mass appeared similar to the myelographic "golf tee" sign. All meningiomas exhibited moderate, well-defined contrast enhancement with dural tails seen in three of the four dogs. One dog had extension into the intervertebral foramen along the nerve and ipsilateral atrophy of the muscles of the neck. By differentiating the meningiomas from intramedullary tumors and by clearly depicting the extent of the masses, MRI provided valuable information about treatment options and prognosis.     

固定顶油罐泡沫灭火系统的改进方法

针对固定顶油罐现有的3种泡沫灭火系统的缺陷,设计了一种新型泡沫灭火系统。该系统克服了液上泡沫灭火系统容易遭到破坏且效率不高、液下泡沫灭火系统容易污染油液并需要高压泵及半液下泡沫灭火系统不能重复使用和造价较高的不足。系统主要由软管、空心浮子、十字喷嘴和泄压管组成,造价低廉,灭火效率高,使用和维护成本低,性价比高,有较高的推广价值。     

单板干燥设备研究进展

通过对大量相关文献进行整理分类,从传热方式角度对单板干燥设备进行分析.分别阐述了喷气式单板干燥机和热压式单板干燥机存在的问题及其改进措施,并对今后单板干燥设备的研发与应用提出建议.     

哈公馆基坑支护与止水的施工工艺研究

对于高层、超高层建筑,基坑支护与止水施工技术措施是否科学、合理,对工程项目自身的质量与进度有重大影响,对工程经济效益提高与人身安全的保证起到关键性作用。文章结合哈公馆工程地质条件,对哈公馆基坑选择高压喷射注浆桩基坑支护与止水帷幕的施工方法,并详细介绍其支护与止水工程的设计施工技术和质量控制措施,取得良好的社会经济效益、技术效益,为解决基坑支护与止水难题提供一定借鉴意义。