Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DEVICE FOR INCREASING THE POi~IER OF MEDIA FLOWING ALONG
A BODY AT A HIGH SPEED OR A VERY FAST MOVING BODY IN A MEDIUM
AND USE THEREOF AS A HIGH PRESSURE NOZZLE
The invention relates to a device for increasing the power of
media f lowing fast along the wall surfaces of a body or, con-
versely, bodies moving very fast in a medium as well as uses of
the device.
Such devices have already been known for high pressure nozzles
in order to produce a high pressure liquid jet (US 1,703,029,
EP-A-0 121 951 and DE-A-3 443 263). It is often desirable not
to spread the so-called "jet angle" of the medium jet exiting
from the nozzle too far, but to keep it as narrow as possible.
In narrow high pressure jets, the energy content per surface
unit of the jet area is, as a rule, higher than in a very far
spread or, respectively, an atomizing jet. The efficiency of
the fast flowing gas or liquid is improved by channels extend-
ing axially along the nozzle opening in the lateral area or,
respectively, the inner wall surface of the nozzle bore.
It is the object underlying the invention to further improve
the power or, respectively, efficiency. It is not only the im-
provement of the "energetic" efficiency of the jet impinging on
an object which is considered, but other efficiencies of media
flowing fast in tubes and hoses, for instance, or of bodies
moving very fast in media are to be improved as well; this
makes it possible to improve the energy expenditure for the
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transport of the flowing medium or a rocket, for instance, or
to increase the velocity thereof, respectively.
The invention is characterised in claims 1 and 14; further con-
figurations are claimed in the subclaims. Preferred conf igura-
tions of the invention are explained in detail upon reference
to the following specification and the drawings.
The invention makes it possible to improve the power of the me-
dium flowing along the wall surface at high speed or the effi-
ciency of a body moving very fast through a medium in a sur-
prising manner: although the wall surface in the direction of
flow is not smooth, but definitely uneven (since recesses are
disposed therein), the power is improved.
According to the general principle of the present invention, at
least one wall surface of a solid body, laterally limiting the
fast flowing medium and guiding it in a specific direction, is
provided with a plurality of recesses extending at least over a
length or, respectively, distance in the direction of flow,
whose depth is substantially smaller than their length. The
depth of the recesses is preferably 0.01 to 2 mm, more particu-
larly 0.1 - 0.8 mm. Such recesses are preferably formed as
groove-shaped recesses in the manner of axial grooves which do,
however, not extend over the whole length of the wall surface
in the direction of flow, but whose length is substantially
smaller than the length of the respective wall surface so that
several such recesses are spaced apart from each other "one be-
hind the other". The depth of part of the recesses, at least,
diminishes in the direction of flow. The recesses may lead to a
retaining site in the flow channel or may form certain
"retaining sites" themselves so that the flow resistance of the
medium changes in the direction of flow and, more particularly,
alternates several times between different values.
If the wall surface of the solid body is formed as the inner
lateral area of a tube, it is recommended to form the recesses
into the lateral tube area such that they constitute marked
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guiding edges substantially in the direction of flow and are
distributed as uniformly as possible over the periphery of the
flow channel. It has been shown that at least four, better five
or six such axial grooves should be disposed in the flow chan-
nel for high pressure water jet nozzles having a small passage
- cross-section whereas even more, e.g. twelve axial grooves
should be provided for f ire extinguishing lances having higher
passage cross-sections.
It has been shown that the sum of the surface portions on the
respective wall surface, Which are constituted by recesses,
should be higher than 1 in proportion to the sum of the wall
surface portions which do not correspond to recesses. The pro-
portion of the surfaces associated with the recesses is pref-
erably 0.7, more particularly 0.8 and 0.9 with respect to the
overall surface, whereby the "roughness" of the wall surface
becomes very strong.
Moreover, it is recommended to make the flow area of the flow
channel diminish in the direction of flow so that there results
an opening angle a between 1° and 13°, more particularly be-
tween 2.8° and 3.8° against the direction of flow of the me-
dium.
A substantially greater improvement may be achieved if an addi-
tional abrupt flow resistance is generated at the end of the
flow channel by a small retaining or impact shoulder before the
medium flowing from said flow channel enters a passage opening,
having a substantially smaller cross-section, of a nozzle in-
sert of a hard material, in particular, through which the jet
then exits from the nozzle.
An arrangement of the axial grooves having a star-shaped cross-
section leads to favourable results.
Thus, it has been shown that the power of a narrow high pres-
sure water jet produced according to the invention could be im-
proved, completely surprisingly, by approximately 350 % over a
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water jet produced with conventional high pressure nozzles at
the same water pressure of 1200 bar. For instance, if a slot is
provided in rock formations with a conventional high pressure
nozzle having a cylindrical inner cross-section of the flow
channel under the above-mentioned pressure and with a flow rate
of 10 1/min water, a "cutting power" of 2 m2/h is achieved at a
specific slot depth. If this known nozzle is replaced with a
nozzle formed according to the invention, there not only re-
sults a higher flow rate between 11 and 11.5 1/min water at the
same pressure, but also a cutting power of 7 m2/h is achieved
for the same rock and under the otherwise same conditions. In
comparison with the conveying rate of 2 m2/h in the case men-
tioned first, this means a multiplication by 3.5.
However, the invention may also be applied to other ffields,
e.g. for pipeline tubes and turbines whose inner jacket is pro-
vided, around the periphery, with such flat recesses extending
in the axial direction and being spaced apart from each other
in said direction. The invention is also applicable to turbine
blades and guide blades of other turbo-machines.
There also result considerable improvements when the inner sur-
faces of suction tubes and manifolds of car or other carburet-
tors are provided with corresponding recesses which are not too
deep. The invention is also applicable to exhaust gas tubes and
exhaust elbows so that there surprisingly result improvements
of several percent in view of reduced fuel consumption with
better output power in the field of internal combustion engines
of motor vehicles, in particular. This result is completely
surprising since one had hitherto considered that the wall and
baffle surfaces exposed to the flowing medium should be config-
ured to be as even as possible.
The reason for the surprising results has not been analysed
sufficiently yet in theory nor science. It is assumed that
there occur boundary layer effects, i.e. that the invention in-
fluences the boundary layer between the flowing medium in the
region near the lateral area, on the one hand, and in regions
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more remote from the lateral area on the other hand such that
there occurs a more efficient distribution between the laminar
and turbulent flows and that less energy is withdrawn from the
medium flowing along the lateral area or, respectively, the
baffle and flow surface although one had to assume prima facie
that such "interruptions" of the wall surfaces or, respec-
- tively, the lateral areas achieve the opposite. Surprisingly,
less kinetic energy, for instance, is withdrawn from the flow-
ing medium in the invention. It is assumed that the so-called
transition line may be displaced far downstream by the inven-
tion, which helps in promoting the discontinuity surface in po-
tential flows. Turbulent effects are reduced.
It is correspondingly recommended to use the invention for flow
surfaces of aircraft and, above all, very fast flying missiles
like rockets wherein the medium surrounding these bodies cer-
tainly need not flow fast itself, but may stand still. However,
since the fast moving body has a high velocity, there also re-
sults a corresponding effect at the boundary layer between the
medium liquid or gas, on the one hand, and the body on the
other hand.
Embodiments of the invention will be explained in detail upon
reference to the drawing; therein:
Fig. 1 is a schematic part-longitudinal section through a high
pressure water jet nozzle in the longitudinal direction
and fig. la shows part of a cross-section through the
nozzle in respectively enlarged representation;
Fig. 2 is a schematic aspect of an inner lateral tube area
serving as a wall surface and comprising a system of
lozenge-like flat recesses in the wall surface;
Fig. 3 is a longitudinal section through a high pressure noz-
zle;
Fig. 4 is a cross-section according to A-A of fig. 3 and
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Fig. 4a is an enlarged part-section thereof;
Fig. 5 is an enlarged detail of the transition between an at-
tachment bushing and a following hard material insert of
the HP nozzle under flow conditions;
Fig. 6 is another cross-section of the flow channel of the at-
tachment bushing;
Fig. 7 is a schematic cross-section through a pipeline tube and
a partial aspect of its inner lateral area; and
Fig. 8 is a schematic cross-sectional drawing of an aircraft
wing.
Fig. 1 shows the longitudinal section through a part of a solid
body 1 configured as a nozzle tube, which may consist of hard
steel, for instance. The inner lateral area of tube 1 having
the diameter D constitutes the wall surface 2 for the medium,
e.g. water, flowing very fast through the tube cross-section.
In contrast to the conventional configuration of the wall sur-
face 2 which is smooth or merely interrupted by axial longitu-
dinal grooves, the wall surface 2 according to the invention is
interrupted by numerous recesses 3 spaced one behind the other
in the direction of flow (SR), which have, in this example, an
approximately lens-shaped cross-section and extend into the ma-
terial of tube 2 with a maximum depth t = 0.3 mm, namely not
over the whole axial length of tube 1, but merely over a length
being about five to fifty times the depth t. According to fig.
la, these recesses 3 may be configured in the form of a notch
having an approximately triangular cross-section with a notch
angle ~3 of between 80 and 100°, in particular. The base or, re-
spectively, the bottom of notch-like recesses 3 extends, as
bottom line 4, substantially in the axial direction or, respec-
tively, the flow direction SR of tube 1 and adopts, in the lon-
gitudinal section, the lens-shaped form shown in fig. 1,
whereby respectively part of the respective recess comprises a
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depth t diminishing in the direction of flow SR along wall sur-
face 2. Therefore such recesses 3 are disposed to be spaced
apart in the direction of flow on wall surface 2, one behind
the other. Also, such recesses 3 are distributed over the pe-
riphery of the inner lateral area or, respectively, wall sur-
' face 2; these recesses are indicated merely symbolically in
fig. 1 by recess lines 3' .
According to fig. 2, the inner lateral tube area 2 is consti-
tuted by a net-like system of webs 2' which, in an aspect seen
from the tube interior, keep lozenge-like recesses 3 spaced
apart from each other, which in their turn comprise bottom
lines 4 substantially extending in the direction of flow SR;
these bottom lines 4 respectively connect those lozenge corners
of each lozenge which are spaced farthest apart. In this con-
figuration of the invention, the greater part of the wall sur-
faces is occupied by recesses 3 Whereas the sum of webs 2*,
which constitute the actual wall surface 2, is substantially
smaller in comparison. Since very narrow webs 2' are used, the
sum of the recesses 3 projected onto the wall surfaces becomes
substantially larger, with about 80 to 95 % of the overall in-
ner lateral tube area, than the remaining wall surface 2 con-
stituted by webs 2'.
According to fig. 3, high pressure water nozzle D comprises a
screw insert 10 made of INOX, i.e. stainless steel, for in-
stance, into which an annular insert 5 of a hard material like
sapphire, in particular, is glued, whose passage opening 6 com-
prises a diameter d of about 1 mm. In the direction of flow, an
attachment bushing 7 is disposed before insert 5, which is to
be considered a body 1 whose wall surface 2 diverts the flow of
the liquid, water in the present case, led through it under
high pressure. The diameter D of flow channel 8 is substan-
tially larger, i.e. 1.5 mm, than diameter d in the region of
the transition towards the cylindrical passage opening 6 of in-
sert 5 so that a retaining or, respectively, impact shoulder 9
is formed at that transition, which prima facie further in-
creases the flow resistance.
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Furthermore, flow channel 8 comprises an opening angle a
against the direction of f low SR. This opening angle should be
between 2 and 13°; an especially preferred opening angle is 3-
4°.
_ Moreover, the flow channel 8 is configured to have a hexagonal
cross-section according to fig. 4, meaning that it comprises
six axial grooves (Fl, F2, F3 ...) having relative sharp guide
edges 4 which extend in the axial direction or, respectively,
the direction of flow SR. According to the length 1 of flow
channel 8, the depth t of these axial grooves is about 0.1 to
0.8 mm at the entrance end of flow channel 8 so that the above-
mentioned opening angle is respected, and diminishes to zero
towards retaining shoulder 9 at insert 5.
Fig. 4a represents a schematic cross-section of the upper half
of attachment bushing 7 shown in fig. 4 in order to illustrate
that axial grooves F1, F2 etc. are formed due to the hexagonal
cross-sectional structure of the inner lateral areas, which are
generated in the region of recesses 3 between the even portions
of the inner lateral tube area and the imaginary semicircle
which would be generated in the known cylindrical or, respec-
tively, conical cross-sections of the flow channel 8 of such
attachment bushings 7. This semicircle does not exist in the
invention because recesses 3 are pressed or milled into body 1
of bushing 7 or carved out therefrom in any other manner.
Therefore the depth t of recesses 3 is measured from this semi-
circle to the "groove base" which is constituted by edge 4 of
the respective notch-shaped axial groove F1, F2, which extends
in the longitudinal direction. The surfaces of axial grooves
F1, F2, F3 preferably also comprise recesses 3 of the type
shown in fig. 1 or 2, which is not shown in fig. 3, but indi-
cated in fig. 4a.
Fig. 5 indicates the expected course of the flow pattern of the
flowing medium which leaves the nozzle or, respectively, insert
4 as a jet S. It is assumed that a thin "boundary layer" is
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disposed about the "core" of jet S, which opposes a certain re-
sistance to the widening of the "core" transversely with re-
spect to the jet direction SR and thereby "holds" the energy of
the liquid jet "together" in a small region with the above-
mentioned effect of an improved efficiency and higher kinetic
energy density.
According to fig. 6, the cross-section of flow channel 8 is not
hexagonal, but star-shaped. The axial grooves or, respectively,
recesses 3 have an approximately triangular cross-section; they
protrude from the approximately conical clearance zone of flow
channel 8 into the material of body 1, i.e. attachment bushing
7.
The cross-section of flow channel 8 selected according to the
invention is for instance produced in that a polygonal tool is
pressed or, respectively, driven into a bushing or sleeve 7
having a conical flow cross-section so far that there result
the cross-sectional shapes of figs. 4 to 6 with the recesses 3
or, respectively, axial grooves F1, F2, F3 formed thereby.
Pocket-like recesses 3, which extend in a planar manner over a
length 1 far in the axial direction or, respectively, flow di-
rection SR of the tubular body 1 of fig. 7, constitute concave
recesses, for instance, whose width b should be less than the
length 1, but noticeably larger than their depth t.
Fig. 8 indicates that it is expedient to dispose the above-
mentioned recesses 3 at least on that wall surface 2 of the
body 1 serving as an aircraft wing where the air flow is di-
verted in the direction of flow SR. Surprisingly, the flow
about wall surface 2 on the respective part of the upper side
of the wing is promoted such that, on the whole, a more effi-
cient flow about the wing may be achieved in order to obtain a
low-separation and, therefore, also a more eddy-free course of
the air flow as it flows about the profile. The optimum depth,
position, dimension and number of recesses may be determined by
some tests in dependence upon the shape of the wing profile and
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the velocity at which the aircraft flies or, respectively, at
which the air flowing about the wing moves.
