Rock Breaking Performance of a Pick Assisted by High-pressure Water Jet under Different Configuration Modes

In the process of rock breaking, the conical pick bears great cutting force and wear, as a result, high-pressure water jet technology is used to assist with cutting. However, the effect of the water jet position has not been studied for rock breaking using a pick. Therefore, the models of rock breaking with different configuration modes of the water jet are established based on SPH combined with FEM. The effect of the water jet pressure, distance between the jet and the pick bit, and cutting depth on the rock breaking performance as well as a comparison of the tension and compression stress are studied via simulation; the simulation results are verified by experiments. The numerical and experimental results indicate that the decrease in the rates of the pick force obviously increases from 25 MPa to 40 MPa, but slowly after 40 MPa, and the optimal distance between the jet and the pick bit is 2 mm under the JFP and JSP modes. The JCP mode is proved the best, followed by the modes of JRP and JFP, and the worst mode is JSP. The decrease in the rates of the pick force of the JCP, JRP, JFP, and JSP modes are up to 30.96%, 28.96%, 33.46%, 28.17%, and 25.42%, respectively, in experiment. Moreover, the JSP mode can be regarded as a special JFP model when the distance between the pick-tip and the jet impact point is 0 mm. This paper has a dominant capability in introducing new numerical and experimental method for the study of rock breaking assisted by water jet and electing the best water jet position from four different configuration modes.

Research on Properties of Woven Fabrics Treated by High Pressure Water Jet

The paper introduces a new technique for the treatment of the woven fabrics. Sprayed by high pressure water jet, the appearance, handle and stiffness of the fabric are improved. Other properties of the high pressure water treated fabrics like drape coefficient, air permeability, tenacity are also presented.

Numerical analysis on coal-breaking process under high pressure water jet

Based on the theory of nonlinear dynamic finite element,the control equation ofcoal and water jet was acquired in the coal breaking process under a water jet.The calculationmodel of coal breaking under a water jet was established;the fluid-structure couplingof water jet and coal was implemented by penalty function and convection calculation.The dynamic process of coal breaking under a water jet was simulated and analyzed bycombining the united fracture criteria of the maximum tensile strain and the maximal shearstrain in the two cases of damage to coal and damage failure to coal.

Application of high-pressure water jet technology and the theory of rock burst control in roadway

This paper puts forward using high-pressure water jet technology to control rock burst in roadway, and analyzes the theory of controlling rock burst in roadway by the weak structure zone model. The weak structure zone is formed by using high-pressure water jet to cut the coal wall in a continuous and rotational way. In order to study the influence law of weak structure zone in surrounding rock, this paper numerically analyzed the influence law of weak structure zone, and the disturbance law of coal wall and floor under dynamic and static combined load. The results show that when the distance between high-pressure water jet drillings is 3 m and the diameter of drilling is 300 mm, continuous stress superposition zone can be formed. The weak structure zone can transfer and reduce the concentrated static load in surrounding rock, and then form distressed zone. The longer the high-pressure water jet drilling is, the larger the distressed zone is. The stress change and displacement change of non-distressed zone in coal wall and floor are significantly greater than that of distressed zone under dynamic and static combined load. And it shows that the distressed zone can effectively control rock burst in roadway under dynamic and static combined load. High-pressure water jet technology was applied in the haulage gate of 250203 working face in Yanbei Coal Mine, and had gained good effect. The study conclusions provide theoretical foundation and a new guidance for controlling rock burst in roadway.

High Pressure Water-Jet Technology for the Surface Treatment of Al-Si Alloys and Repercussion on Tribological Properties

Recent developments in high pressure water-jet technology have brought the process to the forefront as a means of surface treatment. Water jet technology offers cleaning, cutting, processing as well as potential refinement of surface properties. By adapting the process parameters the surface characteristics can be changed while the profile remains the same. In the present study, water-jet technology was used for the surface treatment of Al-Si alloy to investigate its effect on tribological properties. Dry sliding wear behavior was investigated against AISI 52100 bearing steel ball using a reciprocating ball-on-flat configuration. Optical microscopy examination reveals that ploughing of grains, transgranular and intergranular propagation of cracks;are the mechanisms by which material is removed during water jet treatment. While, on the other hand, SEM observation of the wear track reveals that plastic deformation and delamination are the dominant wear mechanism during the wear process. Water jet treatment was compared to hot isostatic pressing in terms of its effects on wear resistance and surface porosity of Al-Si alloy. It was found that, hot isostatic pressing reduces the total amount of porosity at the expanse of hardness while water jet treatment produces a compressed surface having higher hardness and compressive residual stress, which ultimately increases wear resistance.

Optimization of a High-pressure Water-Powder Mixing Prototype for Offshore Platforms

A new device is designed to promote the mixing of high-pressure water jets and powders in typical industrial applications.The water and powder mixing devices traditionally used on offshore platforms are detrimentally affected by the geometrical configuration of the water nozzle and the powder spraying pipe,which are parallel,resulting in small intersecting volumes of liquid and powder.By allowing the related jets to intersect,in the present work the optimal horizontal distance,vertical distance and intersection angle are determined through a parametric investigation.It is also shown that such values change if the number of water layers is increased from one to two.In such a case,the water and powder intersection volume can be greatly increased because the trajectory of the dry powder particles becomes more chaotic.

嵌岩低桩承台锁口钢管桩围堰设计与施工技术

昌九高铁扬子洲赣江公铁大桥西支主桥为(48+144+320+144+48)m无砟轨道钢箱桁组合梁斜拉桥。桥塔墩位于通航河道内,桥位处河床覆盖层浅,基岩强度高,基础由大直径钻孔桩和矩形嵌岩低桩承台组成,承台采用锁口钢管桩围堰施工方案。G33号主墩围堰平面设计尺寸54.56 m×28.52 m,锁口钢管桩采用Q345B材质∅1020 mm螺旋钢管,长28 m,钢管桩之间采用C-T形锁扣连接;围堰设置4层内支撑,单层内支撑设3道对撑,内支撑四角设型钢斜撑;基底设置混凝土垫层参与围堰结构受力。围堰采用XR360旋挖钻机在岩层中引孔,孔内换填细砂后插打钢管桩,钢管桩壁内、外两侧换填砂采用高压旋喷注浆加固。围堰设置智能化监测系统,对围堰受力、变形等进行实时动态监控。实践证明,该桥围堰结构安全可靠、止水效果良好、施工快捷高效。

高超声速大动压下整流罩分离测力风洞试验

针对高超声速试验模型整体式整流罩的反推火箭拔罩分离问题,开展了反推火箭喷流模拟方法和风洞测力试验装置设计研究,试验模拟了马赫数5、动压33 kPa时整流罩反推喷流干扰效应和分离距离影响,获得了反推喷流和分离距离影响下的整流罩气动特性。试验研究表明:反推火箭拔罩分离过程中,喷流干扰作用主导了整流罩的气动特性,使得法向力系数、轴向力系数和俯仰力矩系数分别出现了44.5%、32.4%和198.6%的最大变化量;在负迎角下,整流罩压心前移显著,使得静稳定设计的整流罩呈现出静不稳定性,不利于整流罩安全分离;分离距离越大,分离距离变化对整流罩气动特性的影响越弱;将分离初始迎角限定为小的正迎角,整流罩在分离过程中容易保持姿态稳定,有利于整流罩安全分离。

Sivells方法在高马赫数低总压喷管设计中的适用性分析

目前高超声速轴对称型面喷管广泛采用Sivells方法进行无黏型面设计,通过求解轴对称的von Kármán动量方程进行边界层修正。该方法在常规高超声速风洞、激波风洞等的高马赫数、高总压条件下已成功应用,但鲜有在高马赫数、低总压条件下的应用研究。在低总压条件下,采用该方法设计了马赫数6、8、10、12的轴对称型面喷管,通过数值模拟分析流场结构,并进行试验验证;模拟了喷管射流流场,通过对射流流场进行结构分析,判断设计方法的适用性。研究结果表明:马赫数6、8喷管流场与设计基本一致,射流流场品质较好,适合开展风洞试验;马赫数10、12喷管流场局部过度膨胀,马赫数高于设计值,其中马赫数10喷管的射流流场品质较好,马赫数12喷管的射流流场品质下降显著且马赫数轴向梯度增大。因此,在高马赫数、低总压条件下,Sivells设计方法仍适用于马赫数6、8喷管,马赫数10喷管处于临界状态,而不适用于马赫数12喷管。

浅埋偏压黄土隧道地表旋喷桩加固工艺参数研究

在黄土隧道修建过程中,其洞口段因浅埋偏压、围岩软弱破碎等通常需要进行加固处理。地表旋喷桩法具有适用范围广、加固效果好等优点,被广泛应用于隧道浅埋偏压段软弱围岩地表加固工程。以浅埋偏压黄土隧道进口段初期支护侵限为研究背景,介绍了现场地表旋喷桩加固的施工过程;建立了侵限段三维加固模型并分析了地表旋喷桩加固前后的变形控制效果,说明了处治措施的合理性;对比分析了现场监控量测结果,验证了数值模拟的准确性;开展了地表旋喷桩的工艺设计参数优化分析。结果表明:由于偏压作用,地表最大沉降值偏离隧道中心线,且拱顶中心线处沉降>右拱肩处沉降>左拱肩处沉降;施加地表旋喷桩对于减小地表沉降十分有效,地表最大沉降值减小了45.5%;采用地表旋喷桩加固处理后,拱顶处加固效果最为显著,较加固前沉降减小了57.9%,同时加固后左、右拱肩沉降差值减小了17.4%;建议隧道浅埋偏压段地表旋喷桩加固工艺设计参数:桩直径为0.4~0.6 m、桩间距为1.2 m、横向加固范围为1.5~2倍洞径、竖向加固范围为洞身两侧旋喷桩与隧道拱底平齐。

地面井分层卸压的煤系气合采原理及方式探讨

为了进一步认识制约煤系气合采的因素,提高煤系合层排采各产层的产气贡献,分别从动力、通道和气源条件出发,分析了煤系气合采的必备因素。基于改变地应力状态提高储层导流能力以及分层改变储层流体压力,满足多层合采动力条件的原理,提出了地面井分层卸压的煤系气合采方式。该方式通过在地面进行定向钻井,在目标储层中进行高压水射流作业,人工创造卸压空间(缝、槽、穴等),改变地应力状态,降低有效应力伤害,增加储层导流通道的数量和开度,提高目标储层压降传递速率。待储层压力降至符合煤系气合采动力条件时进行合层排采,从而提高煤系合采各产气层的产气贡献。相较于常规增产改造措施,此方式能够减少煤系气储层在有效应力作用下的储层伤害,且有助于提高储层压降传递效率,增强煤系气的解吸和扩散,降低多层煤系气合采过程中的层间干扰。在以上研究基础上,认为地面井分层卸压的合采方式主要适用于储层地应力大、产层间距小的煤系气储层,且有望在薄互层煤系气储层增产改造及层间干扰严重的叠合共生煤系储层开发领域进行应用推广。

高压水射流辅助锥形PDC齿破碎花岗岩试验研究

深部地层岩石硬度高、研磨性强、可钻性差,地质条件复杂、施工难度大,高压水射流辅助钻井可有效延长钻头寿命,提高钻进效率。采用室内试验与理论分析相结合的方法,开展了高压水射流辅助锥形PDC齿破碎花岗岩试验,分析了高压水射流辅助锥形PDC齿和常规PDC齿破碎花岗岩特性,揭示了射流压力、喷射距离、喷嘴直径及喷射角度等因素对锥形PDC齿破岩效果的影响规律。研究结果表明:在高压水射流辅助破岩条件下,锥形PDC齿与常规PDC齿的破岩比能分别降低了17.36%与19.63%;射流压力越大,射流辅助锥形PDC齿破岩效果越好;在研究条件下,喷距范围为5~10 mm可使水射流辅助锥形PDC齿破岩效果最佳;当喷嘴直径为2 mm时,切削力离散系数最小;喷射角度为30°时,锥形PDC齿切削力与破岩比能达到最小值;喷射角度为20°时,切削力离散系数最小,切削力最稳定。研究结果可为适用于深部硬岩钻井的锥形PDC钻头水力结构设计与优化提供理论支撑。

高燃压中型运载火箭发射地面低高度排导技术

综合高燃压中型运载火箭高密度发射燃气流地面排导需求及烧蚀风险分析,提出基于地面双面导流装置与高位挡流墙结合的地面低高度排导技术方案。利用火箭发射燃气动力学研究总结的燃气流膨胀特性以及导流型面设计方法,解决了地面低高度排导技术涉及的地面导流装置导流型面气动设计以及尺度控制两个关键问题。地面低高度排导技术方案设计与燃气流场瞬态仿真多轮叠代,实现了燃气流排导烧蚀范围合理控制,避免了燃气流低高度排导烧蚀反溅影响箭体。地面低高度排导技术采用专利支撑的喷水冷却防护方案实现高燃压中型运载火箭发射燃气流强烧蚀环境发射系统、发射设施综合防护。基于喷流缩比试验相似性控制方法研制了1∶10比例喷流缩比试验系统,通过喷流缩比试验验证确认高燃压中型运载火箭发射燃气流能够实现地面低高度安全、顺畅排导,同时与发射台、导流装置结构融合的阵列喷水方案能够行之有效解决高燃压中型运载火箭地面低高度排导强烧蚀难题。

低透气性煤层高压脉冲射流割缝-压裂增透技术应用研究

针对盘州平关镇大坪煤矿18采区20号煤层复杂地质条件及瓦斯抽采难题,提出一种高压脉冲射流割缝导向压裂增透技术。为验证该技术效果,分析了其增透技术机理,并设计了4种试验方案进行对比分析。结果表明,采用高压脉冲射流割缝导向压裂方案在瓦斯抽采效果方面显著优于其他方法,与普通抽采、高压脉冲射流割缝、高压水力压裂抽采瓦斯相比,其平均每日抽采瓦斯浓度分别提高了3.01倍、1.41倍和1.67倍;平均每日抽采瓦斯纯流量也相应提升了2.86倍、1.42倍和1.62倍。经过90 d的抽采,该方案的抽采影响半径达到了5.06 m,分别为普通抽采、高压脉冲射流割缝和高压水力压裂抽采方案的2.56倍、1.25倍和1.29倍;在抽采效果相同的条件下,钻孔施工时间分别比普通抽采、高压脉冲射流割缝和高压水力压裂方案缩短了60%、32%和20%,瓦斯抽采达标所需时间分别比普通抽采、高压脉冲射流割缝和高压水力压裂方案缩短了70%、50%和62%。高压脉冲射流割缝导向压裂技术对低透气性煤层瓦斯治理效果较为理想,可供类似矿井借鉴。

基于快速气相色谱电子鼻研究超高压射流处理脱脂乳的感官品质

以新鲜脱脂乳为原料,探究超高压射流(ultra-high pressure jet,UHPJ)处理对脱脂乳感官品质的影响。脱脂乳经100~300 MPa UHPJ处理后,采用电子眼、电子鼻、感官评价分别检测脱脂乳颜色、气味及综合风味变化。结果表明:脱脂乳的主要色号以4095白色为主,占比46.80%~53.83%;电子鼻共检测到酯类、酮类、醛类等42种挥发性风味成分,大部分风味成分呈乳香、果香、烘烤香、青草等气味,主成分分析结果显示,300 MPa处理脱脂乳样品和其他样品风味相差较大;感官评价结果显示,UHPJ处理脱脂乳的乳香和甜味较为突出,不同样品之间在甜味、蛋白胨味、铁锈味、烧焦味和寡淡味方面差异明显,250、300 MPa处理样品生成的二甲基硫等硫化物能够显著增强脱脂乳的烧焦味、蛋白胨味。综上,200 MPa UHPJ处理能较完整地保留脱脂乳中的风味成分,进而实现原料乳风味的保持。

带钢表面高压水射流清洗机理及试验研究

高压水射流技术是冷轧带钢表面清洗的有效技术手段,为了探究高压水射流清洗带钢表面污垢的工作机理,基于计算流体力学理论建立了高压水射流打击力模型,分析了打击力与喷嘴压力和流量的关系。通过正交理论,开展了带钢清洗效果的试验验证,并对不同工况参数下带钢清洗后的表面形貌进行了分析。结果显示,工作压力对于提高带钢清洗后的表面质量影响最为显著。此外,适当增大清洗角度和喷射距离也有助于提高清洗后带钢的表面质量,为优化清洗工艺提供了重要的参考依据。

超深埋隧洞防渗排水措施与衬砌外水压力分布规律

高外水压力是制约超深埋水工隧洞建设的关键性难题之一,以排水孔为中心的综合堵排措施是降低外水压力的主要举措。为克服传统排水孔实体单元法整体网格划分难度大和计算效率较低的问题,首先,基于ABAQUS平台开发了两节点排水孔线单元模型,并验证其在隧洞工程数值模拟分析中的正确性和有效性;其次,建立了考虑防渗排水措施的围岩-衬砌三维有限元模型,研究多种防渗排水措施下的隧洞渗流场及衬砌外水压力分布规律;最后,探讨了防渗灌浆圈与排水孔设计参数对外水压力分布的影响,提出了防渗灌浆圈与排水孔间隔布置的原则。研究结果表明:所开发的两节点排水孔线单元具有较高的精度,在排水孔数目繁多的模型中具有极高效率;排水孔数目越多、深度越大、排距越小,衬砌外水压力越低;排水孔能够有效降低衬砌的外水压力,而防渗灌浆圈降外压能力有限;在排水孔末端间隔一定厚度围岩后再施作防渗灌浆圈,可更有效发挥两者的降压作用。

不同风场中特高压换流站阀厅屋盖风压特性试验研究

特高压(ultra high voltage,UHV)换流站阀厅的金属屋面系统在风荷载作用下易发生屋面表层风揭事故。为深入探讨该类建筑屋面的风压极值特性,基于风洞试验分别探讨了大气边界层(atmospheric-boundary-layer,ABL)风、壁面射流、均匀湍流三种风场作用下的屋面风压特性,比较了平均风剖面、风速、风向、湍流强度等因素对屋面风压的影响。结果表明:阀厅屋盖迎风前缘负风压最大,且控制风向角在45°左右;壁面射流风场下平均风压系数与脉动风压系数均超过大气边界层风场的结果;风速对阀厅屋盖的负风压系数均值和极值影响较小,而湍流度对风压系数的极值影响较大;大气边界风场时,JGJ/T 481—2019《屋盖结构风荷载标准》的最不利风压系数建议值偏于安全;而在壁面射流风场下,阀厅屋盖全风向最不利风压系数在所有区域都大于JGJ/T 481—2019的建议值,设计中应加以重视。

柔性钻具水力导向射流喷嘴流场分析

现有柔性钻具钻井技术和水力喷射径向钻井技术在控制钻进方向上存在困难或有局限性。为实现钻井导向可控,设计了一种能够水力导向的高压射流喷嘴结构。建立导向喷嘴流体数值模型,利用数值模拟的方法进行流场分析,研究喷嘴倾角、喷嘴直径、喷嘴开启个数等参数对导向力、射流速度的定量关系,给出了导向力方向确定方法。结果表明:随着关闭喷嘴个数的增加,喷嘴导向力呈指数逐渐增大;轴向倾角越大,喷嘴导向力和最大喷射速度越大;喷嘴内径减小时,导向力和喷射速度都显著增大。通过数值模拟验证了射流喷嘴水力导向的可行性,分析结果和导向力的拟合公式对水力导向喷嘴钻进方向的研究具有指导意义。

高压注浆法修复桩基断桩效果分析研究

文章以扶海-马塘220 kV线路改造工程中输电杆塔混凝土灌注桩基础为研究对象,通过有限元计算分析了采用高压注浆法修复混凝土灌注桩断桩的效果,并与断桩和正常桩的性能进行对比。通过有限元计算结果可知,高压注浆法修复断桩的抗压、抗拔承载力分别可达正常桩的93%和84%以上,证明了采用高压注浆法修复混凝土灌注桩断桩的可行性及有效性。同时,分析了断桩缺陷位置和缺陷厚度对高压注浆法修复断桩效果的影响规律。