HIGH PRESSURE ABRASIVE-FLUID JET MIXING AND ACCELERATING NOZZLE FOR CUTTING AND DRILLING HARD MATERIAL

PRODUCTION D'UN MELANGE HAUTE PRESSION DE FLUIDE ET D'ABRASIF, ET BUSE DE CONCENTRATION DU JET POUR LE PERCAGE ET LE DECOUPAGE DE MATERIAUX MASSIFS

English Abstract

ABSTRACT
This invention disclosure describes a new hard material
cutting and drilling tool and cutting system method. This
technique, a high energy abrasive-fluid jet, cuts by
accelerating abrasive particles with high velocity eroding
fluid jet stream(s). The concept of using fluid-accelerated
abrasive particles for material removal has been demonstrated
with both wet sand-blasting techniques and gas powered
abrasive jet systems. In these methods, no deep penetration
can be achieved. Abrasive-fluid jet cutting is an extension
to these technologies which produce deep cuts in high
strength advanced composites for a wide range of applications.
The success of this new technique is achieved by reducing
nozzle wear, producing a coherent stream and maximizing the
abrasive particle exit velocity. The advantages of this new
technique include versatility in cutting a wide range of
material with deep kerfing capability with no fire hazards,
low power levels needed, high edge quality, no delamination,
no spallin, no thermal distortion, low noise, adaptability
to remote operations, contour cutting and availability of the
element used. The potentials for this technique include oil
well casing perforation and drilling, use as an augmenting
tool, cutting under water, steel platforms for off shore
drilling, cutting steel pipe-lines, rock, concrete, glass,
metal honeycomb, foams, laminated metal, etc., bore hole
mining applications and forming a bottle shape hole by jet
drilling.

Claims

CLAIMS
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1- An abrasive fluid cutting apparatus connected to a
source of highly pressurized fluid comprising: a
generally cylindrical nozzle assembly consisting of two main
parts one and two: part one including a high pressure tube
with an exit fluid jet orifice, a mixing chamber having a
plurality of inlets at one end thereof, one of said inlets
being connected at said one end to said source of high
pressure fluid; the other of said plurality of inlets being
equally spaced around said first inlet and connected to
said nozzle mixing chamber and to a source of abrasive
particles, and into said mixing chamber ending into a
converging entry zone, in said part two followed by a
reorientation zone (Kl) and acceleration zone (k2) said
nozzle assembly further comprising two narrow discharge
passages, said first of said two passages having an orifice
located at one end thereof adjacent the mixing chamber,
a transition zone diverging from said orifice into said
mixing chamber, the other of said two narrow passages
leading from said converging entry zone through said
reorientation and acceleration zones, said fluid flow
having a supersonic velocity fluid jet (with respect to
air) at said orifice entering said mixing chamber creating
a vacuum thereby causing the suction of said abrasive
particles and mixing said particles with said fluid jet in
said mixing chamber, said mixture subsequently reaching
said converging entry zone, reorientation zone and
acceleration zone;
2- Apparatus as defined in claim 1 wherein parameters
influencing optimum mixing nozzles, assembly design
criteria and nozzle assembly geometry defined by its
straight bore length (K) and diameter (S) of said two
narrow passages with values greater than 27;
Image




3- Apparatus as defined in claim 1 further comprising a
first inlet which includes a fluid supply conduit
communicating between said fluid inlet to a pressurized
fluid source created by one or more positive displacement
pumps (intensifier) activated by a power unit and
regulated by valves;
4- Apparatus as defined in claims 1 and 3 wherein the
other of said inlets further includes one or more abrasive
conduits communicating at one end thereof to said abrasive
inlet and at the other end thereof to said abrasive supply
source;
5- Apparatus as defined in claim 3 wherein said abrasive
supply source further includes a first air inlet opening
into in an abrasive conduit adjacent said abrasive source
and a second inlet opening in said abrasive conduit spaced
from said abrasive source, whereby said abrasive source
and external atmosphere communicate by operating an
adjustable valve connected into a second air inlet opening
for regulating the flow of air and filtering the abrasive
therethrough;
6- A process for use with apparatus of claim 5 comprises
the step of selectively controlling the rate of feed of
said flow particles into said fluid jet and the selection
of the types of abrasives fed, in response to the thickness
of the material, the degree of hardness and difficulty of
cutting the workpiece;
7- Apparatus defined in claim 1 wherein said mixing
chamber is further caracterised by a frustoconical inner
section and a cylindrical outer section, said inner section
being connected to said mixing chamber at the larger end
thereof and having a junction with said cylindrical section
at the smaller end thereof, both inner and outer sections
having the same longitudinal axis; the said conical shaped
section receiving the fluid mixed with the abrasive
particles coming from the mixing chamber accelerated to
high velocity by the fluid jet; the said straight bore
cylinder receiving abrasive particles maximizing momentum
transfer from the fluid to the abrasive particles in the
controlled nozzle environment;



8- Apparatus defined in claim 7 wherein said passageway
frustoconical section further includes an orifice to lead
high pressure fluid toward said conical section, the use
of mixing diameters ranging between 1.25 fluid jet orifice
diameter to 15 orifice diameter producing thereby a high
velocity fluid jet and creating the vacuum inside the
mixing chamber allowing the suction of abrasive particles
and efficient cutting;
9- Apparatus defined in claim 8 further including an
orifice on the side wall of said frustoconical section
leading to abrasive supplying source;
10- Apparatus defined in claim 7 further comprising a
cylindrical outer section connected to the mixing chamber
and to end of nozzle assembly; having entry zone converging
in conical shape, reorientation zone Kl and acceleration
zone (K2) in the form of a long straight bore passage with
lengths ranging between 1.00 to 15.00 inches long with a
diameter between 0.008 to 0.30 inches;
11- Apparatus defined in claim 1 further comprising the
use of passages and proper particle diameters, ranging
between 2 1/2 and 15 particle diameters, further including
selectively controlling the rate of feed of said flow
particles into said fluid jet and the use of an orifice to
provide a gradual diverging inlet fluid jet of conical
shape or solid blade, in order to obtain the best cutting
performance for a wide range of materials;
12- The process in accordance with claim 6 further
caracterised by the step of introducing a fluid with a
supersonic velocity through an orifice into a nozzle's
frustoconical section to produce a gradually diverging
conical fluid jet in said section to create a vacuum
causing the drawing of abrasive particles mixing it with
the entering fluid supersonic jet in the mixing chamber,
the whole being propelled toward the second narrow passage
exit outlet, cutting any material on its way, the nozzle
being also operated without abrasive.
11

Description

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BACKGROUND OF THE INVENTION
The purpose oF this invention is to cut and drill hard
material by abrasive-fluid jet mixing and accelerating
using a high velocity fluid jet nozzle driven by pressures
up to 55,000 PSI. The high velocity fluid jet flow mixes
concentrically in a chamber in which different types of
abrasives are fed. The shape and size of that mixing
chamber affect the mixing efficiency and the jet cutting
capability. Proper selec~ion of the ratio of the fluid
jet orifice diameter to the exit jet diameter is essential
for an efficient cutting and abrasives suction.
The abrasives flow passage should uniformly change
without sharp turns or sudden reduction in area. As high
velocity fluid jets are turbulent with very high Reynolds
numbers; mixing is expected to occur over a short distance
from the fluid orifice exit.
The secondary mixing exit cone acts to prevent the
spread associated with the jet flows. This mixing cone
should be wear resistant, especially for tangential flow.
The entry angle of the abrasives downstream of the
fluid jet is important for good mixing despite the great
difference in momentum between the two phases of the jet.
The principal of cutting is believed to be due to the
super position of the fluid phase pressure on the abrasive
particle impact. An efficient jet should not have a third
gas phase. This is achieved by minimizing air suction.
Two basic types-of commercial sandblasting or AJM
nozzles can be distinguished. They are the venturi type
nozzles and the straight bore nozzles. In these types the
ratio ~/S does not exceed ~O and is much less for small
diameters in the range of 0.09 to 0.13 inches. These
nozzles when used as mixing sections for abrasive fluid
jet cutting experience rapid wear associated ~ith
decaying performance characteristics due to their
unfavorable geometric configuration.
For example, a reduction of 55% in depth of cut in
mi~d steel was observed when the nozzle wore out to 143%



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of its original diameter. This wear rate was observed to
slow down when longer mixing nozzles were used instead of
the commercial nozzles. An improvement of 300% to 380%
in service life was observed when (K) was doubled.
The parameters that influence optimum nozzle design
criteria and nozzle geometry defined by its straight bar
lenght (K) and diameter (S) are:
the abrasive particle size (g)
the abrasive flow rate (6
the fluid jet orifice size (B)
the fluid jet driving pressure (P)
For example, the use of some abrasives with particle
size (g) will immediately constrain the choice of
minimum mixing nozzle diameter (S).
In addition, high fluid jet pressures may require longer
nozzles for maximum possible momentum transfer to the
abrasives in the controlled nozzle environment. The
optimum ratio (K/S) should then be a func~ion of all these
parameters.
Simplified mixing analysis can yield approximate
relationships in support of the previous argument. However,
very complicated theory will be required for an accurate
relationship among these parameters.
The success of the abrasive-fluid jet cutting and
drilliny nozzle relies on the satisfactory performance to
reduce nozzle wear, to produce a coherent stream and to
maximize the abrasive particle exit velocity. The ~:
achievement of the above criteria requires the availability
of a material for nozzle manufacturing such as baron carbid,
silicon carbid, tungsten carbid and alumina ceramics.
The use of optimum nozzle geometric configuration will
result in the use of inexpensive materials in simple ~ormsO
Explicit gains related to the optimized nozzle include the
improvement of cutting rates and quality, the reduction in
nozzle replacement costs and the cost reduction of hydraulic
power.

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Brief Description of the Drawings

The following drawings illustrate embodiments of the
invention:
Fig. 1 Venturi type nozzles and the straight bore
nozzles
Fig. 2 Nozzle friction loss zone and acceleration
zone
Fig. 3 Nozzle design showing length of entry
zone Ko~ length Kl, length K2 not to
exceed the accelerating length
Fig. 4 Single jet multiple abrasive feed
front view main section
Fig. 5 Single jet multiple abrasive feed
top view main section
Fig. 6 Alternative design
Fig. 7 Abrasive-fluid jet cutting system
Detailed Description of Nozzle (Y) Assembly
The nozzle (Y) in figures (4) and (6) consist primarlly
of three (3) major components:
1- high pressure tube with an exit fluid jet orifice
2- a mixing chamber
3- nozzle exit outlet
The high pressure fluid jet is formed through a jet
orifice to guarantee a high quality jet and a long life.
The exit cone is made of a wear resistant material special
for tangential abrasive flows. The adapter body shown in
Figure (4) is used to produce a gradual change in abrasives
flow area and minimize the size of the exit cone.
The seal material is required for efficient suction.
This controls the abrasives flow rate and allows changes
in the velocity of approach. The jet orifice holder can be
reached by simply unscrewing it after removing the high
pressure tube. The whole external body can be removed to
check wear of the protective parts.
The design shown in Figure (4) allows the abrasives to
enter the mixing chamber from three (3) entry holes. This
may be useFul when feeding three (3) different
abrasives or more~ either simultaneously or separately.
This is required while cutting concrete with steel rebars.

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Concrete requires large size abrasives while steel rebars
require small sizes. Another advantage of multiple feed
is the uniformity of mixing.
An alternative design is shown in Figure (6) which
attempt to reduce the distance (Y) and minimize the
volume of the secondary nozzle. This will be more
effective and also reduce exit nozzle replacement costs.

The nozzle geometry related to this invention is
similar to the straight bore type nozzle in Figure (1)
with proper relation between the length (K) and the
diameter (S). To illustrate the concept behind the proper
choice of these parameters the length (K) can be divided
into three (3) regions as shown in Figure (2).
These regions are:
region (1) - in this region, the abrasives are reoriented
to assume a predominantly axial velocity
vector rather than the random orientations
at which the abrasives are introduced. At
the end of this region, the abrasive
particle velocity is slower than the
surrounding fluid velocity, that is:
V6~ Va
region (2) - in this region, the abrasives are accelerated
by momentum transfer from the surrounding
fluid. The maximum possible velocity the
abrasives can attain is that of the surrounding
fluid, this means Va~ V~
region (3) - in this region, friction losses will
contribute to abrasives deceleration, so this
region should be avoided in the design.
Design Analysis Recommendation
1- the two (2? regions ~K~) and (K2) should be made of hard
material to withstand random angle abrasive particle impacts
or be made thick enough such that erosion will self machine
the inside contour.
2- the top entry region is not critical as long as no



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obstructions to the abrasive flow exists. The length
of this section should not allow excessive jet
spreading before entry to the straight bore and
should not be less than a few particle diameters.
3- the rest of the nozz1e length should not exceed the
accelerating length. The nozzle thickness in this
region can be less than that of Region (1). Also
cheaper wear resistant materials can be used. The
nozzle design can then be made of two (2~ separate
sections as shown in Figure (3).
4- for efficient momentum transfer, the fluid jet dialneter~
the particle size and the nozzle diameter should be
close in dimension so as to satisfy the two conditions
S~
S~ ~
But the relation between B and g can be ~>~ 9
5- the abrasives are prefered to enter the top of the
nozzle with minimum turbulence and with as "axial" a
velocity vector as possible. This will accelerate the
reorientation process with reduced wear rates in region
(1). However, the length of the second region remains
the most influential in terms of cutting performance.
6- the second region (K~) can be a simple straight bore
cylinder eas~ to manufacture and replace with minimum
downtime cost.
Abrasive-fluid Jet Cutting Process Description
The high velocity fluid (up to 3000 ft/sec) flowing in
the mixing chamber, as shown in the nozzle assembly design
of Figure ~4), causes vacuum which draws abrasives from an
abrasive storage source. The hose connecting the nozzle
assembly to the abrasive source is Flexible and can be up to
200 ft long with an I.D. of 0.5 inch. The fluid jet is
produced using high pressure (up to 60,000 PSI) developed by
a positive displacement pump (intensifier). The jet is
formed through a jet orifice of openings ranging between
0.003 to 0.05 inch diameter.

In the drawings, the numbers correspond to:


4: venturi type nozzles
5: straight bore type nozzle
6: section (2)
7: section (3)
8: friction loss zone K3
9: V~ Va
10: V~
11: Va
~ ~ a
13: V~
14 Va
15: ~Qct~on (1)
16: entry zone
17: reorientation zone Kl
18: reorientation zone (Kt), acceleration zone (K2), friction
loss zone (K3)
19: acceleration zone (K2)
20: fluid jet
21: length of entry zone Ko
22: length K1
23: length K2
24: distance of 2.50 cm
25: " 6.75 cm
26: " 1.00 cm
27: " 0.90 cm
28: " 16.20 cm
29: " 3.70 cm, hight of the bottom body part
30: " 10.00 cm, hight of upper body part
31: " 6.90 cm
32: " 2.20 cm
33: " 2.30 cm
34: " 2.30 cm
35: " 0.55 cm
36: " 0.80 cm
37: " 0.35 cm. This is the maximwn hight of fluid
jet orifice


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38: security protective rubber
39: distance of 0.40 cm
40: " 2.55 cm screw (3)
41: seal
42: distance of 1.15 cm inside diameter of the mixing chamber
43: " 0.50 cm
44: " 4.50 cm
45: " 3.30 cm
46: fluid entry high pressure tube
47: abrasives
48: 53 angles
49: distance of 1.00 cm out diameter of the abrasive hose
50: distance of 1.50 cm w~dth of the protective plate
51: " 1.00 cm
52: " 3.20 cm
53: " 1.50 cm of screw head
54: " 2.30 cm
55: " 0.20 (min) to 0.25 (max) cm of the Tungsten
carbide tube
56: distance of 0.50 cm
57: " 7.50 cm
58: circle diameter of 7~50 cm
59: circle diameter of 1.00 cm
60: diameter of high pressure tube 1.25 cm
61: screw (6) holding the protective rubber
62: seal
63: seal
64: distance of 2.9C cm
65: " 4.00 cm
66: " 1.50 cm width of the protective plate
67: abrasives supply source
68: abrasives filter
69: power unit
70: intensifier units
71 liquid supply source
72: nozzle assembly
73: liquid kerfing out of the nozzle assembly
74: depth of that supersonic active kerfing approximately
one meter deep in hard material.



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The foregoing description of my invention is not to be
interpreted as limiting to the preferred embodiment
described and illustrated herein, but applicant is
considered entitled to any other emoodiment of the
nozzle assembly and apparatus as a whole which falls
within the scope of his invention.