Experimental Investigation on Chip-break Influenced by Cryogenical Cold Air jet

In machine cutting, the replacement of traditionalKGcutting solution with cryogenical cold air jet not only possesses a good cooling and lubricating efficiency, but also can avoid the occurrenceof environmental pollution. In order to clarify the manner and performance of discharged cutting chip under cryogenical cold air jet condition, an experiment was carried out for steel grade 45 in the dry and cryogenical cold air jet cutting comparatively. The effects of cryogenical cold air jet on the breaking of cutting chip are discussed. Experimental results reveal that, in the valid ranges of pressure and temperature, the cryogenical cold air jet can widen the chip broken region effectively. Different insufflating angle of cold air behaves different influence on the chip-break. From the experiment, it has been gained that the optimized jet insufflatingangle, temperature effecting range and pressure working range of cold air, which provides the foundation of industrial manufacturing.     

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。     

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.     

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。     

Indexes optimization of outburst forecast while a rock cross-cut coal is uncovered by pulsed water jet

To obtain the best outburst prediction index of rock cross-cut coal uncovering slotted by pulsed water jet,the effects of the rigidity coefficient’s measured value and the initial velocity of gas diffusion to the integrative indexes D and K are analyzed based on the dynamic evolution of coal crake field under water jet. Thus the integrative indexes D and K are excluded. A grey relation model of outburst prediction indexes(K1,S and P)from 7 coal mine’ rock cross-cut coal uncovering in Chongqing,Sichuan and Henan is set up. And the grey relation degrees of the 3 prediction indexes to outburst hazard are calculated by using grey relational analysis method. The results show that the outburst hazard can be more accurately reflected by the cuttings desorption index K1 when a cross-cut coal uncovering slotted by pulsed water jet,and it should be considered as the best outburst prediction index.     

2012年春末内蒙古西部地区一次大到暴雨天气分析

本文利用常规气象观测资料,对2012 年5 月10 日发生在内蒙古西部地区的一次大到暴 雨天气过程进行分析,以期提高对春季大雨、暴雨天气的预报能力,实现防灾减灾的目的。     

Experimental study on landscape of CFRP cutting by abrasive water jet

To investigate the influence of operation parameters of abrasive water jet on surface roughness of carbon fiber reinforced plastic(CFRP),experimental studies were conducted.The three-dimensional landscape of cutting front was reconstructed according to the measured data byμscan laser confocal microscopy.Fourier spectral analysis was also adopted to study surface structure in detail.It is found that the morphology of cutting front is similar to that of other materials.In the smooth cutting zone,the fluctuation of amplitudes of surface profile is gentler,compared with that in the rough cutting zone.The lower part of the rough cutting zone was characterized by the periodical appearance of peaks and valleys.The roughness of surface increases with the increase of depth.While in the smooth cutting zone and part of rough cutting zone,roughness increases with the increase of traverse speed.For the thickness of samples,in the smooth cutting zone,the roughness increases with the increase of depth.The dominant harmonic component in the surface profile is concentrated in a narrow range from 0 to 10 Hz,and the relatively higher density of frequency from 10 to 50 Hz is shown in the rough cutting zone,which is caused by the interaction between perpendicular abrasive water jet and reflect jet.     

水砂射流冲蚀作用下临近燃气管道可靠性

为研究水砂射流冲蚀作用导致临近燃气管道的失效概率,分析了管材的临界应变与砂粒在管壁表面形成塑变脊的影响,推导出冲蚀磨损率预测方程。利用Fluent 软件模拟计算水管泄漏射流速度、冲蚀面积分布,并结合冲蚀磨损率预测方程构建冲蚀磨损速率方程。最后基于最小壁厚准则,建立了燃气管道失效概率的计算方法。研究结果表明:①通过临界间距判定分析,可获得不同水管内压、冲蚀时间下的临界间距;②增大水管内压、冲蚀时间、砂粒粒径,减少管道间距、管道壁厚均会导致燃气管道的失效概率增大,其中,管道间距对失效概率影响最为显著。研究结果可为失效场景定量风险评估以及水管与燃气管道并行敷设的间距设计提供参考。     

影响负压反馈射流喷头水力性能的重要参数正交试验

为了探究影响负压反馈射流喷头水力性能的重要参数对水力性能的影响程度,并选出综合水力性能最优下的重要参数组合,首先设计了4因素3水平正交试验,并根据试验要求分别加工出3种长度(4.2,5.6,7.0 cm)的喷管、3种直径(3,4,5 mm)的喷嘴,以及射流进口宽×深为4 mm×8 mm、位差1.80 mm、侧壁夹角20...     

辐射板强化喷管换热与红外抑制效果试验研究

试验研究了在发动机喷管中加装金属辐射板前后,喷管壁面温度、热喷流温度与喷管红外辐射特征的变化。结果表明,加装金属辐射板后,热喷流与喷管壁面之间的热量传递显著增强,热喷流中心温度降低,壁面温度明显升高,在90°方向上,热喷流3～5μm波段的红外辐射强度降低了38.5%。文中从热喷流、喷管壁面以及金属辐射板等相关部件的温度变化情况对红外辐射强度的变化原因进行了解释。 