水射流简答题

空化射流
一．概念和描述
1）Only happened in fluid. On any occasion, it will never appear in air or solid
2). Cavitation results from the local pressure decreasing in fluid. Therefore, it can be controlled through adjusting the degree of pressure decrease.
3).Cavitation relates to the cavity’s initiation and disappear;
4 ) . Cavitation is a dynamic phenomenon in which cavity(bubble) initiates, grows and collapse;
5). No matter the fluid’s states, stationary or flow, it is possible to appe ar cavitation;
6). Cavitation can occur not only inside the fluid, but at the interface of solid and fluid. 1）。

在任何场合，它永远不会出现在空气或固体仅发生在流体。

2）。

局部压力降低流体的气蚀的结果。

因此，它可以进行控制，通过调整压力下降的程度。

3）。

气蚀腔的萌生和消失;
4）。

气蚀是一种动态现象腔（气泡）启动，成长和崩溃;
5）。

不管流体的状态，静止或流动，有可能出现气穴现象;
6）。

空现象不仅内部的流体，但在固体和流体的界面。

二．Clarification澄清
1.Traveling cavitation 旅行气蚀
Single transient bubble in liquid forms, grows, and collapses.
This transient traveling bubble may appear at the low- pressure area along the solid surface, or at the core of moving vortex or high turbulent area of shearing field.
单瞬态泡在液体的形式，成长，并且崩溃。

这短暂的泡沫可能出现的低压区沿固体表面，或在移动涡或高湍流剪切场面积的核心。

2.Fixed cavitation固定气蚀
Bubble or cavity, at stable state, fixes on the solid surface.
Because of the fluid mixture or fluid back-flow at the end section of cavitation area, fixed bubble may grow and collapse.
Strong oscillation will appear.
泡泡或空腔，在稳定的状态，固定在固体表面上。

由于流体混合物或液体回流的气蚀区的端部，固定的气泡生长和收缩。

强会出现振荡。

3.Vortex cavitation涡气蚀
One of the earliest cavitation able to be observed by people.
It always appears at the tips of ship’s propellers and sometimes is called “tip cavitation”. Only when the bubble of this cavitation collapses at or near the solid surface, can strong cavitation erosion happen.
一个能够被人们所观察到的最早的汽蚀。

它总是出现在船舶螺旋桨的提示，有时被称为“尖气蚀”。

只有当气泡的气穴固体表面或接近崩溃，发生强烈气蚀侵蚀。

4.Vibratory cavitation 振动气蚀
Above, common feature: a fluid unit passes the cavitating area only one time
Vibratory cavitation: continuous big-amplitude and high-frequency pressure vibration.
A fluid unit will undergo cavitation- recycle for many times
以上，共同特点是：流体单元通过空泡面积只有一次
振动气蚀：连续大振幅和压力高频振动。

一种流体单元将进行多次循环气蚀
三．Cavitation erosion空蚀
Heterogeneous mixture of vapor and gas pockets or “voids,” frequently causes a rapid erosion of adjacent material structure
A very incomplete understanding of the mechanisms by which a “ cavitation field” causes rapid damage to adjacent solid material
异构混合物的蒸汽和气体的口袋或“空洞”，经常会导致迅速侵蚀相邻材料的结构
一个非常不完整的理解“气穴场”的机制，导致迅速伤害到相邻的固体材料
Mechanisms of Cavitation Damage空蚀破坏的机制
1.Micro-jet’s Action微射流的行动
Cavitation holds the promise of a new and exciting way to fabricate both top down and bottom up nanostructures. Cavitation bubbles are created when a liquid boils under less than atmospheric pressure.
气蚀持有一个新的和令人兴奋的方式来制作纳米结构自上而下和自下而上的承诺。

空化气泡时创建低于大气压力下液体沸腾。

The collapse process occurs supersonically and generates a host of physical and chemical phenomena. The collapse of a cavitation bubble near an object occurs asymmetrically and launches a reentrant microjet directly towards it.
超音速发生倒塌过程，并产生一系列的物理和化学现象。

不对称的物体附近发生空化泡的崩溃和启动折返微喷，直接朝它。

If permanent air in the bubble, at the final stage of bubble collapse, the temperature will rise rapidly to a high level. As the collapsing duration is very short, the heat exchange is impossible to happen with the ambient fluid. When the super-hot air contacts with the metal surface, it will be heated to melting point
如果永久空气中的泡沫，泡沫崩溃的最后阶段，温度将迅速上升到一个较高的水平。

由于折叠的持续时
间很短，该热交换是不可能发生的，与环境流体。

超热空气与金属表面接触时，它会被加热到熔点。

四。

Cavitation Inception and Parameter Effects 空泡起始和参数影响
The cavitation inception means that at or near the place of lowest pressure, there appears micro-cavity(bubble)空化起始装置，压力最低处或附近的地方，出现微腔（气泡）
1.parameters effect参数效果
1）.Effects of Fluid Parameters流体参数的影响
(1) temperature温度；(2) pressure 压力；(3) other parameters其他参数
2）gas content气体含量
gas content , the number of bubble and the extent of the cavitating region, but the collapse voilence of individual bubble 个别气泡的气体含量，气泡的数量和程度的空泡地区，但
坍塌VOILENCE的
3）cavitation number空化数
If cavitation number is increased , the number and mean diameter of bubbles , collapsing pressure differential and collapse violence。

If the cavitation number is increased in a given situation by reducing the velocity and maintaining constant pressure, the damage will probably be decreased.
如果空化数增加时，气泡的数量和平均直径，崩压力差和崩溃暴力。

如果在一个给定的情况下，通过减
少的速度和保持恒定的压力，空化数增加的损害可能会下降。

2.Cavitation Bubble Dynamics空泡动力学
High-speed photography and acoustic measurements. 高速摄影和/声学测量。

1)Two characteristic effects:两个特征的影响：
the emission of shock waves upon the collapse of the bubble泡沫崩溃后排放的冲击波
The generation of a high-speed liquid jet directed towards the (solid) boundary 一种高速液体喷射的产生朝向（固体）的边界
2)Rayleigh analysis瑞利分析
(1）Cavitation damage is primarily a result of fluid-mechanical rather than corrosive effects
气蚀破坏主要是流体机械的结果，而不是腐蚀作用
(2）The analysis shows the potential for the generation of very high fluid pressure and velocities by cavitation bubble collapse
该分析显示了非常高的流体压力和速度的产生空化泡崩溃的潜在的
(3）The energy would become infinite at the completion of bubble collapse, when the originally finite bubble has become a mathematical point. Infinite energy is then ascribed to zero mass, so that no violation of the energy-conservation law is involved .
能量将变得无限大的气泡破裂完成后，原来有限的气泡时，已成为数学的角度。

无穷的能量，然后冲高
质量为零，所以没有涉及违反能量守恒定律。

While the Rayleigh model demonstrates the potential for very high, local, and transient pressure and velocities in the liquid as a result of bubble collapse, it does not provide a plausible mechanism for the transmission of the pressure and velocities to an eroded surface.
虽然瑞利模型表明在液体中的压力和速度非常高的地方，和瞬态的电位作为气泡破裂的结果，它不提供
一个合理的机制，用于传输的压力和速度的侵蚀表面。

Time of bubble collapse 泡沫崩溃的时间
ρ---- liquid density密度
p---- pressure压力
R0---- initial bubble radii气泡初始半径
3.Single Laser-produced Bubble Dynamics单激光产生的气泡动力学
The characteristic effects of bubble dynamics, in particular the formation of high-speed liquid jet and the emission of shock waves at the moment of collapse are recorded with high-speed photography with faming rates of up to one million frames/s .
气泡动力学特性的影响，特别是形成高速液体射流和冲击波排放崩溃的时刻警钟长鸣率高达100万帧/
秒的高速摄影记录。

Damage is observed when the bubble is generated at a distance less than twice its maximum radius from a solid boundary. The impact of the jet contributes to the damage only at small initial distances (γ≤0.7)
Hammer pressure , about 0.1GPa观察到当气泡从固体边界的距离小于两倍的最大半径处产生伤害。

射流的影响纳入到的损伤，仅在小的初始距离（γ≤0.7）
锤压力，约0.1GPa
The largest erosive force is caused by the collapse of a bubble in direct contact with the
Bubbles in the range γ≤0.3 and γ=1.2 to 1.4 caused the greatest damage
最大的侵蚀力引起的直接接触的边界中的气泡的崩溃，其中的压力为几个GPA所在在材料表面上的行为。

范围内的气泡的γ≤0.3，γ=1.2〜1.4造成最大破坏的
Cavitation jet汽蚀射流
Application:应用：
Cleaning paint and rust from metal surfaces清洁金属表面的油漆和锈
Underwater removal of marine fouling 海洋防污水下拆除
Removing high explosives from munitions除去高炸药弹药
Augmenting the action of deep-hole mechanical bits used to drill for petroleum or geothermal energy resources 增强深孔机械位用于钻探石油或地热能资源的作用
Corresponding to the jet structures, the damaged patterns by the rectangular cavitating jets are different from those by circular cavitating jets 对应的喷射结构，由矩形空化射流损坏的图案是圆形空化射流不同
Cavitating jets cut kerfs effectively at ambient pressure up to 20.7Mpa
空化射流切割切口，有效地在环境压力高达20.7Mpa
All submerged water jets at atmospheric pressure cavitate if the jet velocities are greater than 14m/sec.全部淹没在大气压力下的水射流气蚀，如果喷射速度大于14m/sec。

Submerged cavitating jets removed approximately twice as much materials as the cavitating jets in air. There exists a threshold pressure淹没空化射流去除尽可能多的材料在空气中的空化射流的大约两倍。

存在一个阈值压力。

Practical applications实际应用
(1) self-oscillated cavitation nozzles used on cone bits 自振荡空化喷嘴牙轮钻头
(2) cavitation jets to remove silica scales 气蚀喉去除二氧化硅秤
(3) six-stage turbine to oscillate a piston to produce cavitation bubbles in the drilling fluid
六个阶段的涡轮机振荡活塞产生空化气泡，在钻井液中
(4) Injecting gas into the drilling mud to produce cavitation at greater depth. 气体注入到钻井泥浆中产生气蚀的深度更大
(5) To reciprocate pipe , a shoulder located above the bit would lift the liquid in the wellbore and produce low frequency pressure fluctuation. 往复运动管，肩膀位上方将解除在井孔中的液体，并产生低频压力波动。

(6) self-oscillating water injection自激振荡注水
(7) drilling nanoholes as small as a few nanometers 钻探纳米孔小几纳米
(8) Nanowelding
(9) Other aspects其他方面
磨料射流
1.Many techniques have been devised to increase the cutting capability已经设计出了许多技术，以提高切削能力:
(1) Cavitating jets空化射流
(2) High-frequency modulated jets高频调制射流
(3) Pulsating waterjets脉动水射流
(4) Use of polymer additives聚合物添加剂的使用
(5) High-velocity droplet jet高速度液滴喷射
(6) Elevated-temperature waterjets (hot jets) 升高温度的水进入（热喷流）
(7) Abrasive-waterjets磨料水射流
2.AWJ cutting systems offer the following advantages, in addition to those mentioned before for waterjet cutting磨料水射流切割系统具有以下优点，除了之前提到的那些水射流切割:
（1）Able to cut very hard materials能够削减非常坚硬的材料
（2）Lower power requirements低功耗的要求
（3）No delamination不分层
（4）Reduced striation减少条纹
3. The AWJ technique is suitable not only for conventional engineering materials such as metals and glass, but also for newly developed materials as mentioned below磨料水射流技术不仅适用于传统的工程材料，如金属和玻璃，但也用于新开发的材料，如下文所述:
ceramics, ceramic composites, metal matrix composites, laminates, high-specific-strength materials, and fiber-reinforced resin composites. 陶瓷，陶瓷复合材料，金属基复合材料，层压板，高比强度的材料，纤维增强树脂复合材料。

4.AWJs can be formed by 磨料射流喷头的分类:
（1）Single waterjet (side abrasive feed)单射磨料侧进式喷头
（2）Multiple waterjets (side abrasive feed) - convergent or parallel多射流磨料侧进式喷头
（汇聚式多射流侧进式喷头和平行多射流侧进式喷头）
（3）Multiple waterjets (central abrasive feed)多射流磨料中进式喷头
（4）Abrasive layer旋转引射式磨料射流喷头
（5）Direct injection of abrasive
waterjets are applied in special situations when wide kerfs are required. 单水射流系统是最发达和最常用的一个。

多水射流应用在特殊情况下，当需要宽的切口。

6.AWJs for cutting, turning, and drilling all consist of the same basic components 磨料水射流对于切削，车削，钻孔都包括相同的基本元件：:
（1）High-pressure pump 高压泵
（2）Abrasive delivery system磨料输送系统
（3）AWJ nozzle 磨料水射流喷嘴
（4）Traverse system 横动系统
（5）Catcher 捕手
7. Pressurized water through a sapphire orifice forms a coherent, high-velocity waterjet. The waterjet and a stream of solid abrasive are introduced into a mixing and accelerating tube constructed of very hard material. 通过蓝宝石孔压水，形成一个连贯，高流速的水射流。

水射流和固体磨料流引入非常坚硬的材料构成的混合和加速管。

8. The momentum transfer between the waterjet and the abrasive is complex. 水射流和磨料之间的动量转移是复杂的。

（1）Limited dynamic stability of the high-pressure waterjet. 有限的动态稳定的高压水射流。

（2）Hydrodynamic drag forces imposed by the water phase on the solid particles. 水相的固体颗粒上所施加的流体动力学曳力
（3）Cutting occurs as a result of erosion, shearing, failure under rapidly changing localized stress fields, or micromachining effects. 切割发生迅速变化的局部应力场，或微机械加工的影响下侵蚀，剪切，失败的结果。

（4）The cutting rate can be controlled by adjusting the parameters of the process. 切削速率，可以通过调整参数的过程控制。

9.The parameters involved in the AWJ cutting process 磨料水射流切割过程中涉及的参数: Hydraulic Parameters液压参数
（1）Water jet pressure (P) 水射流压力
（2）Jet hydraulic power (hhp) 喷气机液压功率
（3）Water jet orfice size (dn) 水喷孔的大小
（4）Water flow rate (qw) 水流量
Abrasive Parameters磨料参数
（1）Abrasive flow rate (ma) 磨料流量（MA）
（2）Abrasive particle size (dp) 磨料粒度（DP）
（3） Abrasive material磨料
Mixing Parameters混合参数
（1）Mixing tube length (lm) 搅拌筒长度（LM）
（2）Mixing tube diameter (dm) 搅拌筒直径（DM）
Traverse Parameters导线参数
（1）Traverse speed (u) 移动速度（U）
(2)Standoff distance (SOD) 防区外距离（SOD）
(3)Number of passes (N) 遍数（N）
(4)Jet angle (αc) 喷气角（αC）
Other Parameters
Method of abrasive feed (suction-forced) 方法磨料饲料（吸被迫）
Condition of abrasive (dry-slurried) 磨料条件（干浆状）
10.混合磨料射流&注射磨料射流
Premixed abrasive jet: 预混磨料射流：
1.Abrasive mixes with the water jet early in the system 磨料水射流混合系统中的早期Injection abrasive jet: 注射磨料射流：
2.Abrasive mixes with the waterjet in a mixing chamber just after the nozzle 磨料水刀在混合室混合后喷嘴
Comparison of the two kinds of jet: 射流两种比较：
Lengthen the time of acceleration (P) 延长加速时间（P）
Abrasive receives bigger energy (P) 磨料获得更大的能量（P）
Damage to equipment and lines (P) 设备和线路的损坏（P）
Complex structure of nozzle (I) 结构复杂喷嘴（I）
No additional parts in the pipelines (I) 在管道中不需要额外的部件（I）的
Applied at higher pressure (I) 施加在较高压力下（Ⅰ）
11. AWJ cutting & Parameters磨料水射流切割及参数
参数：
pressure, water flow rate, abrasive flow rate, abrasive particle size, traverse rate, number of passes, relative hardness and standoff distance的压力，水的流速，流速磨料，磨料粒度，进给速度，遍数，相对硬度和偏离距离
Difficult task of optimizing the AWJ cutting performance艰巨的任务磨料水射流切割性能优化
12.Applications of AWJ磨料水射流
For surface finish improvement: 对于表面光洁度改进：
Multipass finishing -- Traversing the jet 多道精加工 - 遍历喷射without lateral feed. 没有横向饲料。

Abrasive size -- Use of finer abrasive with 磨料粒度 - 使用更细的磨料additional passes. 其他通行证。

For surface finish improvement (cont’d):
Abrasive material -- Softer abrasive materialsImproved surface roughness.
Abrasive condition -- Slurried abrasive to be more effective.
改善表面光洁度（续）：
研磨材料 - 较软磨料materialsImproved表面粗糙度。

磨料条件 - 淤浆磨料是更有效的。

13.Hole piecing
⏹Techniques of hole piercing with AWJs depend largely on the target material
⏹Penetration rate decreases significantly as the depth increases
⏹High-pressure (200 to 400MPa) fracture or cracking due to shock loading or
hydro-fracking
孔接头
技术与AWJs穿孔在很大程度上取决于目标材料
普及率随着深度的增加显着降低
高压（200〜400MPa级）断裂或开裂由于冲击负荷或水力压裂
Hole trepanning
⏹This process begins with either a predrilled hole or by piercing with the AWJ
⏹The AWJ moves to the perimeter of the hole and approaches it at a very shallow angle
⏹Jet deflection affects the uniformity of the surface waviness
孔穿孔
这个过程首先是预钻孔或穿孔与磨料水射流
磨料水射流孔的周边移动，并接近在一个很浅的角度
射流偏转影响的表面波纹度的均匀性
Milling of holes
⏹Some advantages of hole milling:
⏹Holes smaller than the jet diameter can be drilled.
⏹Hole edges are of uniform roughness.
⏹High accuracy and repeatability of hole diameters and positions are possible.
⏹ A simple method for blind hole drilling is provided.
铣削孔
铣孔的一些优点：
小于射流直径的孔可钻。

孔边缘粗糙度均匀。

高精确度和可重复性的孔的直径和位置是可能的。

盲孔钻探提供一种简单的方法。

6 Advantages of AWJ Cutting
⏹Suitable for many operations (linear cutting, turning, milling, drilling)
⏹ Able to machine very soft and very hard materials
⏹Able to machine multi-material composites selectively
⏹Able to cut stacks of different materials
⏹Minimal deformation stresses
⏹No thermal effects
⏹Reasonable material removal rates
⏹Multidirectional machining
⏹No heavy clamping needed for workpiece
⏹No direct "hard" contact with workpiece
⏹Ideal for automation, robotics, and remote control
磨料水射流切割的优点
适用于许多操作（线切割，车削，铣削，钻孔）
能够对机器非常柔软，非常硬的材料
能机多材料复合材料的选择性
能切割不同材质的堆叠
最小的变形强调
无热效应
合理的材料去除率
多向加工
没有重型夹紧工件所需
没有直接的“硬”与工件接触
非常适于自动化，机器人和远程控制。