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.

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.

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.

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。

Investigation on Water Jet Treated Polyester/cotton Blended Cambric

Analytical examination was made to ascertain the effect of the high pressure water flow on the fabric properties.Polyester/cotton blended cambric was spurted by high pressure water flow. Fabric properties such as handle,thickness, tensile strength , stiffness and air permeability after the water treatment were investigated.

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。

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。

基于正交试验法的铝合金车体高压水清洗喷嘴结构优化

抑尘剂等复杂的化合物黏着在铝合金车体上,导致车体污染十分严重,高压水射流清洗方法能够有效去除铝合金车辆车体表面黏着的化合物。通过分析圆柱形、锥形、文丘里形和余弦形喷嘴的射流流场分布、射流出口速度、最大壁面静压、相同清洗宽度下压力值范围,得到余弦形喷嘴的清洗性能最佳,锥形喷嘴次之。基于正交试验法设计五因素、四水平正交试验表,得到常用清洗压力下余弦形喷嘴的最优结构参数:进口直径为40 mm、出口直径为20 mm、过渡段半径为40 mm、出射段长度为25 mm、过渡与余弦部分长度比为4。按照最优喷嘴结构参数进行建模,得到三组压力值下高压水出射速度比未优化前提高了2%,且优化效果随着入口压力值的提高而有所下降。在优化后的喷嘴结构参数下进一步计算得出入口压力为10 MPa时,靶距设置为250 mm能达到较好的清洗效果和节能作用。

THE PERFORMANCES OF HIGH PRESSURE JET OF PURE WATER AND POLYMER SOLUTION WITH CONICAL NOZZLE

In this paper, the effects of polymer additives and nozzle shape on the proper- ties of high pressure water jet discharging into the air are investigated by theory and experiments. Criteria of judging the jet quality are put forward. And, a method that can be used in analysing the fluid flow within the nozzle is developed. Then, the calculated results are compared with the experiments that we carried out; it is shown that the degree of agreement between the two is good. At last, the mechanism to improve on the jet quality with polymer additives is discussed.

密闭空间内高压过冷水射流冲击高温铅铋熔池能质传输数值模拟研究

蒸汽发生器传热管破裂(SGTR)事故是铅铋冷却快堆(LFR)最为严重的设计基准事故之一,将导致二回路高压过冷水通过管道破口高速射流注入一回路高温液态铅铋(LBE),强烈的相间热质传输可能引发蒸汽爆炸,严重威胁堆芯结构的完整性。为了揭示SGTR事故现象机理,本文基于VOF多相流模型、LES湍流模型和Lee相变模型,考虑容器内覆盖气体层作用,建立了密闭空间内高压过冷水射流冲击高温LBE多相流动与瞬态传热传质过程的三维数值计算模型,重点分析了过冷水温度及入口压力对射流发展和射流周围环境(即覆盖气体层和LBE区域)的影响。结果表明,典型的射流按相态可分为4个区域,即水-蒸汽过渡区、多相流区、末端水相区和蒸汽斑块区。射流沸腾主要发生在射流中心区域和两侧的相界面上,相变产生的蒸汽夹带残余水相沿着界面从射流的末端向顶部迁移,计算工况下最大沸腾速率通常在喷管出口处,为7090 kg/(m^(3)·s)。覆盖气体层和LBE区压力与过冷水温度和入口压力均呈正相关,LBE区压力会随着射流发展逐渐增加,同时蒸汽的迁移可能引起LBE区压力发生波动,在4.4 ms时间内在覆盖气体层和LBE区获得的最大压力分别为0.157 MPa和0.351 MPa。本文结果揭示了射流沸腾机理与压力演化特性,为铅铋冷却快堆SGTR事故系统安全评估提供了理论支撑。

基于高水压射流的盾构泥饼切割试验研究

为解决高水压射流清理泥饼布置方式无依据等问题,研制泥饼压制设备和高水压射流装置,并以强风化泥质粉砂岩作为试验材料,开展高水压射流切割泥饼试验,研究射流压力、流量、传输介质等参数对泥饼切割宽度和深度的影响。主要结论有:1)随着冲刷距离的增大,泥饼切割宽度先增大然后逐渐减小至0,而切割深度则逐渐减小;2)射流压力相同的情况下,当流量从49.1 L/min增大至110.0 L/min时,高水压射流对泥饼的切割宽度增大,当流量从110.0 L/min增加至202.8 L/min时,切割宽度反而减小,切割深度则随着流量的增加而增大;3)射流流量相同的情况下,水压力越大,则切割宽度和深度也越大;4)在水中进行泥饼切割时,高水压射流对泥饼的作用以冲刷为主,难以产生有效的切割。

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。

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。

第三系半成岩富水砂岩隧道水平高压旋喷桩复合结构超前预加固研究

在诸如第三系半成岩地层等富水软弱均质地层的隧道建设中,常采用水平高压旋喷桩进行洞内超前预加固,但水平旋喷桩往往因自身抗拉强度低在承受较大荷载时容易发生断裂破坏。依托云南临沧至清水河高速公路王家寨隧道工程,提出了一种在桩体内插入小直径钢管的水平高压旋喷复合结构。通过力学理论分析、数值模拟与现场监测,对比分析了水平高压旋喷桩素桩与复合结构的力学机制与对围岩加固作用,并对钢管布置形式及直径进行优化设计。研究表明:在300 kPa水压下,复合结构相比素桩的挠度值降低了34.8%,最大拉应力降低了37.5%,受力模式明显改善,承受的极限水压力荷载大幅提升至700 kPa,对围岩拱顶沉降、应力也有一定削减作用;增加拱顶钢管布置密度可有效降低桩体拉应力,而减少钢管直径则会导致钢管拉应力增大;建议实际工程中拱顶间隔1根桩体布置108 mm钢管,拱肩间隔2~3根布置89 mm钢管,边墙可不设钢管。

高含量低透性近水平煤层控制性水力割缝技术

基于高压水射流割缝的技术原理和特点,针对云南省朱家湾煤矿煤层“硬度系数大、瓦斯含量高、低透气、抽放时间紧”的特点,结合矿井目前的实际采掘部署和生产情况,提出工作面“钻割一体化”的瓦斯治理增透措施,并在矿区内已经施工抽采钻孔的工作面开展试验研究.通过现场研究表明:采用“钻割一体化”增透技术,能有效提高煤层裂隙发育程度,改变和降低煤层原始应力和瓦斯含量,增大煤层瓦斯流动空间,成功消除煤层的突出危险性.试验数据显示,煤层在水力割缝后单孔瓦斯抽采量增加到原来的3.7倍,工作面抽采达标时间缩短一半,成功缓解了矿井采掘接替紧张的局面.该试验的成功,为本矿井及类似矿井的瓦斯治理提供依据和经验.

三轴搅拌桩组合高压旋喷桩入岩落底式止水帷幕施工技术

某房建深基坑工程支护形式采用排桩+落底式止水帷幕,场地地质条件上部为富水深厚砂层,下部为强风化岩层,止水帷幕需穿透强风化岩0.5 m,以隔断强透水层。通过对地质情况及现有设备条件分析,采用大功率桩机先行施工三轴搅拌桩,养护后进行桩体质量抽芯验证,再针对不同缺陷程度采用高压旋喷桩分别进行补强的组合工艺施工止水帷幕。基坑开挖结果表明,该落底式止水帷幕效果良好,能有效隔断强透水层,与灌注排桩结合形成深基坑支护结构体系具有较高的经济性、适用性。

基于高压水射流的钢筋混凝土破拆技术研究及应用

高压水射流技术的发展为钢筋混凝土建(构)筑物向绿色化拆除提供了新的技术保障。为了探究高压水射流技术在钢筋混凝土建(构)筑物拆除工程中的应用效果,采用理论分析、设计计算和室外试验,开展了基于高压水射流技术的钢筋混凝土结构体局部破拆模拟试验。试验结果表明:与传统机械破拆方法相比,高压水射流破拆效率提高50%以上,破碎程度高,破拆界面平整。同时,水射流破拆不会产生大量的粉尘,减少了对环境的污染,避免了碎石飞溅对作业人员的生命安全产生威胁。钢筋混凝土建(构)筑物高压水射流技术的应用可为国内外同类工程提供重要参考依据。