Stress release mechanism of deep bottom hole rock by ultra-high-pressure water jet slotting

To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.

Mechanism and numerical simulation of pressure stagnation during water jetting perforation

When perforating with an abrasive water jet, it is possible that the pressure in the hole （perforation） will be higher than that in the annulus because of water jet blasting against the hole wall, which also is the theoretical basis for the technology of hydro-jet fracturing. This paper analyzes the mechanism of generating pressure stagnation in water jet hole, and puts forward a new concept of hydroseal. Then, the distribution of pressure in the hole was simulated with the finite element method. The simulation results showed that the pressure in the hole was higher than that in the annulus. Also, the lower the annular pressure （confining pressure） and the higher the blasting pressure, the greater the pressure difference. An experiment indicated that the cement sample was lifted up under the pressure stagnation in the hole, which proved the finite element simulation results obviously.

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.

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.

Reaction thrust characteristics of high-pressure submerged water jet of cylinder nozzles

The shapes and geometrical parameters of nozzles are key factors for fluidics. The relationship among the reaction thrust, flow rate pressure, diameter do and length L of a cylinder nozzle is analyzed theoretically. The simulation of the flow field characteristics was conducted via the FLUENT computational fluid dynamics package. Effects of the inlet conditions and the nozzle dimensions on the reaction thrust of a water jet were addressed particularly. The reaction thrust experiments were performed on a custom-designed test apparatus. The experimental results reveal that a） the nozzle diameter and the inlet conditions exert great influence on the water jet reaction thrust; and b） for L≤4d0, where the nozzle is treated as a thin plate-orifice, the reaction thrust is independent of nozzle length; for L〉4d0, where the nozzle is treated as a long orifice, the reaction thrust can reach maximum under the condition of a certain flow rate. These findings lay a theoretical foundation for the design of nozzles and have significant value, especially for the future development of high-oressure water-let orooulsion technology.

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.

外科新技术—水刀(water jet scalpel)

介绍近年出现的外科新技术-水刀(waterjetscalpel)及其在肝胆外科、颌面外科、骨外科、神经外科、泌尿外科、耳鼻喉科和眼科手术中的应用。

Studies of flow field characteristics during the impact of a gaseous jet on liquid–water column

Both experimental and numerical studies were presented on the flow field characteristics in the process of gaseous jet impinging on liquid–water column. The effects of the impinging process on the working performance of rocket engine were also analyzed. The experimental results showed that the liquid–water had better flame and smoke dissipation effect in the process of gaseous jet impinging on liquid–water column. However, the interaction between the gaseous jet and the liquid–water column resulted in two pressure oscillations with large amplitude appearing in the combustion chamber of the rocket engine with instantaneous pressure increased by 17.73% and 17.93%, respectively. To analyze the phenomena, a new computational method was proposed by coupling the governing equations of the MIXTURE model with the phase change equations of water and the combustion equation of propellant. Numerical simulations were carried out on the generation of gas, the accelerate gas flow, and the mutual interaction between gaseous jet and liquid–water column.Numerical simulations showed that a cavity would be formed in the liquid–water column when gaseous jet impinged on the liquid–water column. The development speed of the cavity increased obviously after each pressure oscillation. In the initial stage of impingement, the gaseous jet was blocked due to the inertia effect of high-density water, and a large amount of gas gathered in the area between the nozzle throat and the gas–liquid interface. The shock wave was formed in the nozzle expansion section. Under the dual action of the reverse pressure wave and the continuously ejected high-temperature gas upstream, the shock wave moved repeatedly in the nozzle expansion section, which led to the flow of gas in the combustion chamber being blocked, released, re-blocked, and re-released. This was also the main reason for the pressure oscillations in the combustion chamber.

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.

An experimental and numerical approach-characterisation of power cartridge for water-jet application

Power Cartridges are pyrotechnic devices where hot combustion gases utilized to do mechanical work for disruption of suspected Improvised Explosive Devices(IEDs). It plays a vital role either in destroying the suspicious object or making them non-functional by generating the gas pressure on burning of propellant against the water column inside the barrel, Present work is focused on characterisation,numerical solution such as deformation; strain; stress using FEM(Finite Element Method), design qualification, performance and evaluation of power cartridge for disruptor application. Experimental trials for pressure-time(P-t) measurement in closed vessel(CV), various electrical parameters like all fire current(AFC), no fire current(NFC) and ignition delay have been measured. Further, mechanical properties for brass material have been determined. An attempt has been made to characterise the power cartridge by FEM and carrying out the experiments for water-jet application.

高承压性富水卵砾石地层中N-JET工法试验及质量效果分析

为探索研究高承压性富水卵砾石地层的止水帷幕施工,选取北京轨道交通某施工现场,采用N-JET工法施作超高压旋喷桩,以期完成不同桩径和不同角度的止水旋喷桩(墙)和封底工程的试验施工。同时结合超前桩体质量检测技术和实际开挖验证方法,揭示超高压旋喷桩(墙)和封底的止水效果。针对试验结果,进行了成功经验总结和不足原因分析,研判在北京相似水文地质条件工程中实际应用的可能性,并提出了下一步技术创新改进建议。

Prevention and treatment technologies of railway tunnel water inrush and mud gushing in China

Water inrush and mud gushing are one of the biggest hazards in tunnel construction. Unfavorable geological sections can be observed in almost all railway tunnels under construction or to be constructed, and vary in extent. Furthermore, due to the different heights of mountains and the lengths of tunnels, the locations of the unfavorable geological sections cannot be fully determined before construction, which increases the risk of water inrush and mud gushing. Based on numerous cases of water inrush and mud gushing in railway tunnels, the paper tries to classify water inrush and mud gushing in railway tunnels in view of the conditions of the surrounding rocks and meteorological factors associated with tunnel excavation. In addition, the causes of water inrush and mud gushing in combination of macroand micromechanisms are summarized, and site-specifc treatment method is put forward. The treatment methods include choosing a method of advance geological forecast according to risk degrees of different sections in the tunnel, determining the items of predictions, and choosing the appropriate methods, i.e. draining-oriented method, blocking-oriented method or draining-and-blocking method. The treatment technologies of railway water inrush and mud gushing are also summarized, including energy relief and pressure relief technology, advance grouting technology, and advance jet grouting technology associated with their key technical features and applicable conditions. The results in terms of treatment methods can provide reference to the prevention and treatment of tunnel water inrush and mud gushing.

Jetstream高压泵在油田行业径向水射流技术中的应用

近年来的开发实践表明,由水平井衍生的零半径径向射孔技术是低渗透油气藏增产、增效的有效技术,正发挥着重要的作用。而Jetstream始终提供最先进的高压水射流技术并与专业径向射孔设备公司保持着紧密的合作,推动高压水射流技术在径向射孔的成功应用。

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.

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。

喷水推进器进水流道格栅流固耦合特性研究

为了研究格栅部件对喷水推进船舶效率的影响,本文拟采用流固耦合的数值计算方法系统地对格栅表面受力及其强度特性进行计算,结合有限元方法和流固耦合理论,以STARCCM+和ABAQUS软件为工具,根据目前已知的格栅剖面设计方法,对目前格栅的剖面形式进行改进,形成新型对称剖面形式的格栅。基于上述计算流体力学与流固耦合计算方法对其进行周围流场、结构静力强度、结构动力强度进行计算与分析。结果表明:对称形式的格栅剖面对于降低格栅的变形与应力水平有一定的帮助,采用新型对称形式的剖面结构使格栅总体变形模式发生了变化,但是最大变形位置与最大应力出现在格栅的位置未发生明显变化,新型对称剖面形式格栅具有比较好的静强度与动强度特性,各栅条均匀承受流体载荷。

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。

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。