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.

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.

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.

Dynamic effects of high-pressure pulsed water jet in low-permeability coal seams

Mine gas extraction in China is difficult due to the characteristics such as micro-porosity,low-permeability and high adsorption of coal seams.The pulsed mechanismof a high-pressure pulsed water jet was studied through theoretical analysis,experimentand field measurement.The results show that high-pressure pulsed water jet has threedynamic properties.What's more,the three dynamic effects can be found in low-permeabilitycoal seams.A new pulsed water jet with 200-1 000 Hz oscillation frequency andpeak pressure 2.5 times than average pressure was introduced.During bubble collapsing,sound vibration and instantaneous high pressures over 100 MPa enhanced the cuttingability of the high-pressure jet.Through high-pressure pulsed water jet drilling and slotting,the exposure area of coal bodies was greatly enlarged and pressure of the coal seamsrapidly decreased.Therefore,the permeability of coal seams was improved and gas absorptionrate also decreased.Application results show that gas adsorption rate decreasedby 30%-40%and the penetrability coefficient increased 100 times.This proves that high-pressurepulsed water is more efficient than other conventional methods.

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.

Numerical Investigation of Jet Impingement Cooling with Supercritical Pressure Carbon Dioxide in a Multi-Layer Cold Plate during High Heat Flux

Jet impingement cooling with supercritical pressure carbon dioxide in a multi-layer cold plate during the heat flux of 400 W/cm_(2) is investigated numerically.The generation and distribution of pseudocritical fluid with the high specific heat of supercritical pressure carbon dioxide and the mechanism of the heat transfer enhancement led by the high specific heat are analyzed.For a given nozzle diameter,the effects of the geometric parameters of a multi-layer cold plate such as the relative nozzle-to-plate distance,relative plate thickness,and relative upper fluid thickness on the average heat transfer coefficient are studied.The results show that the target surface is cooled effectively with supercritical pressure carbon dioxide jet impingement cooling.When the radial distance is less than 6 mm,the maximum wall temperature is 368 K,which is 30 K lower than the maximum junction temperature for a silicon-based insulated gate bipolar transistor,a typical electronic power device.There is a pseudocritical fluid layer near the target surface,where specific heat reaches above 34 kJ/(kg·K)locally.The drastic rise of the specific heat leads to obvious heat transfer enhancement.Within a certain range,the local heat transfer coefficient and the specific heat are linearly correlated and Stanton number remains constant over this range.The heat transfer coefficient is at a maximum when the relative nozzle-to-plate distance is 1.As the relative plate thickness increases from 0.5 to 3.5 or the relative upper fluid thickness increases from 0.5 to 2.5,the average heat transfer coefficient decreases monotonically.

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。

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。

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。

基于5DOF的隧道摄像头清洗装置控制系统设计

针对隧道内摄像头镜面污染严重,影响隧道监控管理的问题,基于高压水射流技术,提出了一种5自由度的机械臂清洗装置。分析系统的功能需求,采用电驱动的方式对机械臂的控制系统进行设计,基于比例积分微分控制(PID)原理设计了各关节的定位功能,并用物联网监控的方式开发了远程APP测控系统。通过室内实验确定了最优的清洗工艺参数,并进行了现场的清洗实验。实验结果表明:其能够实现隧道摄像头镜面的有效清洗,清洗装置各关节的定位相对误差在1.4%以内,为隧道内摄像头或者标识物的清洗提供了安全高效的机械化方式。

空化射流水力振荡器研制与试验

为解决油井井筒存在结垢现象后导致卡钻的风险与石油产出率降低的问题,利用淹没射流产生剪切空化,设计一种空化射流水力振荡器,与高压旋转射流除垢装置配套使用提升井筒除垢效率,利用数值模拟对空化射流水力振荡器内部相关结构参数进行优化,得到最优结构参数和振荡频率、幅值。通过开展现场试验,检验空化射流水力振荡器的具体参数是否符合井筒除垢要求。通过正交模拟得到射流喷嘴到喉管距离L=13.52 mm、喉管长度D=64.47 mm和射流喷嘴角度α=156.92°的最优参数,且该参数下的振荡频率为9.92 Hz。现场试验结果表明,空化射流水力振荡器与旋转冲洗器配合使用比传统水力振荡器与旋转冲洗器除垢速度最高提高16.2%。这表明空化射流水力振荡器对除垢装置的除垢效率有明显的提升,空化射流水力振荡器内部结构无相对运动部件使得振荡器运行稳定且装置维护成本低。所得结论可为水力振荡器的研究与工程应用提供技术指导。

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。

火箭弹尾射流对发射平台壁面冲击研究

火箭弹发射时,火箭弹尾部燃气射流会形成波系结构复杂的燃气冲击流场。为分析燃气对发射平台的冲击,基于有限体积法,采用了Realizable k-ω模型,耦合了火箭弹的内弹道过程,建立火箭弹尾部燃气射流三维的数值模拟模型。以安装在发射平台上的火箭发射器为例,分别在火箭弹高角为15°和28°工况下射击时,通过尾部喷出的火药气体流场进行计算,分析尾部火药燃气射流对平台壁面的冲击作用,得到在不同高角射击下不同时刻的气流速度场以及对发射平台壁面的冲击压力,绘制出对壁面的压力曲线图,并且对壁面压力的冲击变化过程做出了分析研究并将其结果与试验对照,验证了数值模拟结果的准确性,在高角为28°时,相较与高角为15°其火药燃气射流对平台壁面的冲击作用明显更大。

万米深井钻柱减振增能提速方法研究

万米深井超深超长井段钻进过程中存在钻柱振动剧烈、能量传递困难、破岩效率低、钻头使用寿命短等问题,亟需开展万米深井钻柱减振与井底增能技术研究。根据超深层钻井环境的主要特征,结合近年来钻柱动力学研究结果,提出了以钻井过程中钻柱振动为能量来源提高井底钻井液射流压力的方法,在减小钻柱振动保护钻头的同时,提高钻头射流压力,实现井下增能破岩,解决井下振动强度大、井底水力能量不足的问题;并研制了井底钻柱减振增能装置,进行了现场试验。研究和试验结果表明:钻柱振动蕴含巨大的能量,该能量可以转化为破岩提速能量;设计的井底钻柱减振增能装置,可以提高钻井液射流压力,同时可以降低钻柱振动导致的安全风险,从而显著提高钻井速度。研究成果为万米深井减振提速技术开拓了新方向,为加快深部油气资源的勘探与开发提供了技术支持。

坚硬顶板高压磨料射流侧向切顶煤柱卸荷技术研究

针对坚硬顶板下临空巷道存在的高应力、大变形、难支护等问题,分析了磨料射流能量分布情况,研究了磨料颗粒及高压水射流的冲击破岩作用。基于“砌体梁”原理,建立不同岩性条件下的岩层周期破断力学模型,研究了巷道侧向切顶条件下上覆岩层断裂情况,采用数值模拟分析切顶前后煤柱应力变化情况,提出了磨料射流侧向切顶煤柱卸荷技术。现场试验结果表明,采用磨料射流切顶后巷道高度变形量减小38.7%,宽度变形量减小45.8%,巷道变形得到有效控制。同时,切顶后每日最大总能量降低85.5%,平均每日总能量降低82.6%。验证了磨料射流侧向切顶对坚硬顶板的弱化效果,为坚硬顶板弱化治理提供了一种新的技术手段。

高压射流破冰仿真研究

风力发电技术领域中风机覆冰已成为制约风电机组安全运营的重大隐患.为研究连续高压射流对冰层的冲击破碎,将该过程简化为细长圆柱,对有限大的冰块冲击破碎的过程,基于SPH方法建立高压射流破碎冰层有限元模型,观察射流撞击冰块发生失效破碎时冰块的碎裂程度.模拟了随时间变化的应力波演化以及与之相对应的冰层破坏效果.分析了不同射流速度、射流角度以及喷嘴口径对射流碎冰程度的影响,并为满足高效、节能的除冰方法选择射流速度为80m/s、射流角度为75°、喷嘴口径为2 mm的射流方式.