Abstrict Measuring volume flows or mass flows in the intake system of motor
vehicle internal combustion engines plays an important role in reducing
harmful emissions. Therefore, an ultrasonic flow meter for measuring
a flow velocity of a fluid flowing in an essentially laminar flow
in the main flow direction is described. The ultrasonic flow meter
has at least two ultrasonic transducers, the ultrasonic transducers
being able to emit and/or receive ultrasonic waves at an angle .alpha.
to the main flow direction which is different from 90.degree.. Furthermore,
the ultrasonic flow meter has at least one turbulator situated upstream
from at least one ultrasonic transducer in the main flow direction
of the fluid, which generates longitudinal eddies in at least one
zone adjacent to the at least one ultrasonic transducer, in particular
in a protrusion in a wall of a flow pipe and thus improves the flow
of the fluid in this zone in the flow pipe. Wedge-shaped turbulators
protruding into the flow of the fluid or flow grooves are provided
in particular as turbulators. The ultrasonic flow meter is distinguished,
in comparison with devices known from the related art, by improved
signal-to-noise ratio and thus by higher measurement accuracy.
Claims 1. An ultrasonic flow meter for measuring a flow velocity of a
fluid flowing in an essentially laminar flow in a main flow direction,
comprising: at least two ultrasonic transducers capable of at least
one of emitting and receiving an ultrasonic waves at an angle .alpha.
to the main flow direction that is different from 90.degree.; and
at least one turbulator situated upstream from at least one of the
at least two ultrasonic transducers in the main flow direction of
the fluid, the at least one turbulator generating longitudinal eddies
in at least one zone adjacent to the at least one of the at least
two ultrasonic transducers.
2. The ultrasonic flow meter as recited in claim 1 wherein: the
at least one zone of the fluid in which the at least one turbulator
generates the longitudinal eddies includes one of at least one protrusion
of a flow pipe and a portion thereof.
3. The ultrasonic flow meter as recited in claim 2 wherein the
at least one protrusion includes a rounded edge.
4. The ultrasonic flow meter as recited in claim 1 wherein the
at least one turbulator is wedge-shaped.
5. The ultrasonic flow meter as recited in claim 1 wherein the
at least one turbulator includes at least one flow groove.
6. The ultrasonic flow meter as recited in claim 5 wherein the
at least one flow groove includes a wedge-shaped cross section.
7. The ultrasonic flow meter as recited in claim 1 wherein the
at least one turbulator includes a periodic structure perpendicular
to the main flow direction of the fluid.
8. The ultrasonic flow meter as recited in claim 1 wherein the
at least one additional turbulator is situated downstream from the
at least one of the at least two ultrasonic transducers with respect
to the main flow direction of the fluid.
9. The ultrasonic flow meter as recited in claim 1 further comprising:
at least one electronic terminal device; and an insertion sensor
insertable into the flowpipe, wherein the at least two ultrasonic
transducers and the at least one electronic terminal device are
integrated in the insertion sensor.
10. The ultrasonic flow meter as recited in claim 9 further comprising:
at least one additional electronic control device for at least one
of activating and reading at least one of the at least one of the
at least two ultrasonic transducer and the at least one turbulator,
the at least one additional electronic control device being integrated
into the insertion sensor.
11. The ultrasonic flow meter as recited in claim 9 further comprising:
at least one reflection element including at least one reflection
surface and being integrated into the insertion sensor, wherein:
the flow pipe includes at least one pipe wall, and the at least
one reflection element being located at a distance from the pipe
wall in such a way that the fluid can flow along both sides of the
at least one reflection surface on the at least one reflection element.
Description FIELD OF THE INVENTION
[0001] Ultrasonic flow meters are used in the automotive industry,
in particular in the intake system of internal combustion engines,
for measuring volume flow or mass flow.
BACKGROUND INFORMATION
[0002] Typically ultrasonic transducers are used which are capable
of both emitting ultrasonic waves into a fluid and receiving ultrasonic
waves. The propagation time of ultrasonic signals which are transmitted
from an emitter to a receiver is influenced by the flow of the fluid.
It is possible to infer the flow velocity of the fluid from the
degree of influence of the propagation time.
[0003] British Published Patent Application No. 2 101 318 describes
an ultrasonic flow meter in which two ultrasonic transducers are
mounted on opposite sides of a pipe through which a fluid flows.
The transducers are situated slightly offset with respect to one
another, so that ultrasonic waves emitted by one transducer and
received by the second transducer propagate at an angle to the flow
direction of the fluid which is different from 90.degree..
[0004] In addition to the system described in British Published
Patent Application No. 2 101 318 A, ultrasonic flow meters are also
known in which ultrasonic waves emitted by an ultrasonic transducer
are initially reflected one time or multiple times before they are
received by a second ultrasonic transducer situated on the same
side of the pipe through which the fluid flows as the first ultrasonic
transducer. Such systems are described, for example, in European
Published Patent Application No. 0 477 418 in British Published
Patent Application No. 1 541 419 and in Japanese Published Patent
Application No. 59100820. In European Published Patent Application
No. 0 477 418 A1 a unit made up of two ultrasonic transducers and
one reflector system is integrated into a coherent unit which may
be installed in a measuring tube.
[0005] FIG. 1 shows the operating principle of these measuring
systems corresponding to the related art. A fluid 112 for example,
air, flows through a flow pipe 110 in an essentially laminar flow
at a flow velocity v.sub.FL 114. Two ultrasonic transducers 116
and 118 are mounted on opposite sides of flow pipe 110 in such a
way that first ultrasonic transducer 116 is able to emit ultrasonic
waves, which may be received by second ultrasonic transducer 118
these ultrasonic waves propagating at a velocity v.sub.UL 120 at
an angle .alpha. to flow velocity 114 which is different from 90.degree..
In the system depicted here, the ultrasonic waves of ultrasonic
transducer 116 propagate toward ultrasonic transducer 118 at a velocity
v.sub.UL,1 which is higher than in an unmoving fluid 112 due to
the motion of fluid 112 at velocity 114. v.sub.UL,1=v.sub.UL+vFLcos
.alpha. (1) v.sub.UL stands for the propagation velocity of the
ultrasonic waves in an unmoving fluid. In contrast, if ultrasonic
waves are emitted by ultrasonic transducer 118 and received by ultrasonic
transducer 116 these waves propagate at a velocity v.sub.UL,2 which
is lower than propagation velocity v.sub.UL in unmoving fluid 112.
v.sub.UL,2=v.sub.UL-v.sub.FLcos a (2)
[0006] Comparing a propagation time t.sub.1 which a signal needs
from ultrasonic transducer 116 to ultrasonic transducer 118 with
a propagation time t.sub.2 which an ultrasonic signal needs from
ultrasonic transducer 118 to ultrasonic transducer 116 allows flow
velocity v.sub.FL 114 of the fluid to be determined: v FL = L 2
cos .times. .times. .alpha. ( 1 t 1 - 1 t 2 ) ( 3 ) A similar calculation
of flow velocity v.sub.FL may also be performed for reflection systems
such as described in EP 0 477 418 A1 for example.
[0007] The systems described in the related art, however, all have
the problem that angle .alpha. in FIG. 1 must be sufficiently small
for a successful flow measurement, but at least substantially smaller
than 90.degree.. This results in the problem that it is not possible
to fit the surfaces of ultrasonic transducers 116 118 flush to
the inside surface of flow pipe 110. Protrusions 122 are thus formed
in flow pipe 110 in the area of ultrasonic transducers 116 118
which result in turbulences and flow separations. These turbulences
cause pressure fluctuations and may result in interfering signal
contributions which are superimposed on the actual ultrasonic signals
as noise.
[0008] Another disadvantage of these turbulences and flow separations
is that contaminants or particles such as dust, oil, or water droplets
contained in the flowing medium tend to be deposited in the turbulence
zones. One possible remedy is to insert wedge-shaped adaptor elements
which fill up protrusions 122 of flow pipe 110 but are permeable
to ultrasonic waves. The disadvantage here, however, is that the
layer thickness of the wedge-shaped adapter elements varies over
the cross section of an emitted ultrasound beam. This makes resonance
adjustment for efficient ultrasound injection into the flowing medium
difficult. Furthermore, such a construction responds sensitively
to structure-borne noise injected into flow pipe 110.
SUMMARY OF THE INVENTION
[0009] The present invention therefore provides an ultrasonic flow
meter for measuring the volume flow and/or the mass flow of a fluid
which may be used in particular in the intake system of a motor
vehicle internal combustion engine.
[0010] The present invention is based on an ultrasonic flow meter
corresponding to the related art for measuring a flow velocity of
a fluid exhibiting an essentially laminar flow in a main flow direction.
At least two ultrasonic transducers are used, it being possible
for the ultrasonic transducers to emit ultrasonic waves into the
flowing fluid at an angle to the primary flow direction which is
different from 90.degree. or receive ultrasonic waves. The core
of the present invention is that at least one turbulator is situated
upstream from at least one of the ultrasonic transducers in the
main flow direction. This turbulator generates turbulences in at
least one zone of the fluid adjacent to the at least one ultrasonic
transducer.
[0011] These turbulators may be flow grooves, wedges, and/or steps
for example, or a combination of these elements. These elements
are advantageously interrupted once or multiple times across the
main flow direction.
[0012] The use of turbulators according to the present invention
in the vicinity of the ultrasonic transducers causes the formation
of eddies which reduce or stabilize burble zones in the design-related
pipe protrusions near the ultrasonic transducers. By locally generating
turbulences, the flow adjusts better overall to the contours of
the ultrasonic flow meter, thus reducing aerodynamically caused
interference signals. The flow meter signal thus becomes considerably
more accurate. This effect may be additionally reinforced by suitably
shaping the protrusions, in particular by forming rounded edges
on the protrusions.
[0013] The present invention may be applied to both linear systems
such as described, for example, in British Published Patent Application
No. 2 101 318 and reflection systems such as presented in European
Published Patent Application No. 0 477 418. Complete or partial
integration of the system into an insertion sensor which is insertable
into a flow pipe is possible and facilitates practical insertability
and replaceability of the ultrasonic flow meter. In particular,
an electronic control device may also be integrated into the insertion
sensor for activating and/or reading at least one ultrasonic transducer.
The electronic control unit for reading out at least one ultrasonic
transducer may, for example, contain electronics for preprocessing
received signals. Appropriate electronic plug-and-socket connections
may also be integrated for contacting the insertion sensor. Furthermore,
at least one reflection element having a reflection surface may
be integrated into the insertion sensor, making it possible to implement,
for example, one of the reflection systems described above. Advantageously,
the at least one reflection element is inserted into the flow pipe
in such a way that fluid is able to flow on both sides of the reflection
surface along the reflection body. This has the advantage in particular
that if the reflection element is not in contact with the wall of
the flow pipe, water droplets that may be contained in the flow
are precipitated on the flow pipe as a wall film before flowing
through the insertion sensor, the wall film then being able to flow
through the flow pipe without wetting or contaminating the reflection
surface and thus interfering with the reflection.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows a schematic diagram of a system for ultrasonic
flow measuring;.
[0015] FIG. 2 shows a cutaway diagram of a part of an embodiment
of a system for ultrasonic flow measuring, the section plane being
parallel to the main flow direction.
[0016] FIG. 3 shows a view of the system according to FIG. 2 from
below.
[0017] FIG. 4 shows a system similar to that according to FIG.
2 corresponding to the related art without turbulators.
[0018] FIG. 5 shows the formation of eddies in the system according
to FIGS. 2 and 3 in side view.
[0019] FIG. 6 shows the formation of eddies according to FIG. 5
from below.
[0020] FIG. 7 shows a cutaway diagram of an exemplary embodiment
alternative to the system according to FIG. 2 having turbulators
situated differently and reversed main flow direction, the section
plane being parallel to the main flow direction.
[0021] FIG. 8 shows a view of the system according to FIG. 7 from
below.
[0022] FIG. 9 shows a cutaway diagram of an embodiment of an ultrasonic
flow meter equipped with turbulators and integrated into an insertion
sensor, the section plane being parallel to the main flow direction.
[0023] FIG. 10 shows a cutaway diagram of a part of an embodiment
of an ultrasonic flow meter alternative to FIG. 2 having flow grooves,
the section plane being parallel to the main flow direction.
[0024] FIG. 11 shows a view of the system according to FIG. 10
from below.
[0025] FIG. 12 shows an embodiment alternative to FIG. 10 having
a rounded edge.
DETAILED DESCRIPTION
[0026] The principle of ultrasonic flow measuring has been explained
above with reference to FIG. 1. Linear systems (as in FIG. 1) or
reflection systems may be used, for example. FIGS. 2 through 3 show
a detail of an embodiment according to the present invention of
an ultrasonic flow meter. The detail includes only an area around
an ultrasound sensor 116 which is embedded into a wall of a flow
pipe 110. A fluid 112 having a main flow direction 210 which is
parallel to flow velocity 114 flows through flow pipe 110. As explained
previously with reference to FIG. 1 a protrusion 122 is formed
upstream from ultrasound sensor 116 within which burble zones of
the flow of fluid 112 are formed.
[0027] As the cutaway view having the section plane parallel to
main flow direction 210 in FIG. 2 and the view from below according
to FIG. 3 show, in this embodiment of the present invention, turbulators
212 are situated upstream from protrusion 122 on the wall of flow
pipe 110. In this case, turbulators 212 have five flat leaves having
a wedge-shaped cross section, which are equidistant from one another
on the wall of flow pipe 110 and protrude into the flow of fluid
112. The tip of the wedge-shaped cross section faces away from ultrasonic
transducer 116 while the wider side of each turbulator 212 faces
ultrasonic transducer 116.
[0028] The functioning of turbulators 212 is elucidated with reference
to FIGS. 4 through 6. FIG. 5 corresponds to FIG. 2 and FIG. 6 corresponds
to FIG. 3. FIG. 4 shows a cutaway view similar to FIG. 5 having
the section plane parallel to main flow direction 210; however,
no turbulators 212 are used, according to the related art.
[0029] As FIG. 4 shows, in an embodiment without turbulators 212
relatively large eddy zones 410 are formed in the area of protrusion
122 of flow pipe 110 the eddy zones in turn resulting in large
burble zones 412 of the flow of fluid 112 in the area of protrusions
122. These burble zones 412 may be extremely unstable, constantly
changing their extension across main flow direction 210. This results
in intense local pressure fluctuations, which are detected by ultrasonic
transducer 116 as interfering signal background.
[0030] On the other hand, when turbulators 212 are used as shown
in FIGS. 5 and 6 longitudinal eddies 510 are formed due to the
discontinuities across main flow direction 210 caused by turbulators
212. These longitudinal eddies 510 cause a more intense pulse exchange
between burble zone 412 and the remaining flow of fluid 112 which
considerably reduces burble zone 412 in the exemplary embodiment
according to FIGS. 5 and 6. Furthermore, the extension of burble
zone 412 across main flow direction 210 is stabilized, so that the
interfering signal background due to local pressure fluctuations
upstream from ultrasonic transducer 116 is reduced. At the same
time, the flow (symbolically represented by flow line 512 in FIG.
5) adheres better to the wall of flow pipe 110 and the wall of protrusion
122. The amplitude of pressure fluctuations upstream from ultrasonic
transducer 116 and the associated interference signals are thus
considerably reduced and the signal-to-noise ratio of the ultrasonic
flow measuring is substantially improved.
[0031] In FIGS. 2 3 5 and 6 turbulators 212 have a wedged shaped
design (i.e., flat leaves having a wedge-shaped cross section).
However, other designs of turbulators 212 are also conceivable.
Thus, for example, rectangular, quadrangular, or rounded cross-section
geometries of turbulators 212 may also be used. Furthermore, instead
of flat leaves, non-flat geometries may also be used (e.g., pyramids
or similar three-dimensional formations). It is advantageous, however,
if turbulators 212 as in the exemplary embodiment of FIGS. 2 3
5 and 6 have a possibly periodic structure perpendicular to main
flow direction 210 of fluid 112. This preferably produces stable
longitudinal eddies 510. In addition, alternatively or additionally,
parts of turbulators 212 may also be designed as lamellas or guide
vanes or guide blades in main flow direction 210.
[0032] FIGS. 7 and 8 show, respectively, a cutaway view having
a section plane parallel to main flow direction 210 and a view from
below of another embodiment of a part of an ultrasonic flow meter
according to the present invention. In principle, the system of
FIGS. 7 and 8 corresponds to the system of FIG. 5 for example;
however, in this case fluid 112 flows through the system in the
opposite direction, so that main flow direction 210 is from the
right to the left in this exemplary embodiment. Thus, this detail
corresponds, for example, to a detail around ultrasound sensor 118
in FIG. 1. Therefore, compared to the exemplary embodiment of FIG.
5 for example, in this exemplary embodiment a plurality of turbulators
212 are mounted on the opposite side of ultrasound sensor 118 on
the wall of flow pipe 110. Also in this case, turbulators 212 have
a wedge-shaped design, are situated periodically, and their tips
point against main flow direction 210. Like in the above-mentioned
exemplary embodiment, other embodiments of turbulators 212 are again
conceivable. The functioning of turbulators 212 is similar to the
functioning according to the above-mentioned exemplary embodiment.
Longitudinal eddies 510 are formed again, which reduce burble zone
412 within protrusion 122 upstream from ultrasonic transducer 118.
Furthermore, the flow of fluid 112 again symbolized by flow line
512 in FIG. 7 adheres better to the wall of flow pipe 110 and protrusion
122.
[0033] In an ultrasonic flow meter, both systems according to the
exemplary embodiment shown in FIGS. 2 3 5 and 6 and systems according
to the exemplary embodiment of FIGS. 7 and 8 may be used. It may
thus be advantageous to situate turbulators 212 upstream and downstream
in main flow direction 210 from a protrusion 122 of an ultrasonic
transducer 118. In this way, a response to the reversal of main
flow direction 210 for example, is also possible, whereby mass
flows and volume flows, for example, of refluxes of an internal
combustion engine may be measured using the same system.
[0034] FIG. 9 shows a preferred exemplary embodiment of an ultrasonic
flow meter 910. Instead of a diagonal measuring system, as in FIG.
1 for example, a reflection system is used here. Ultrasonic waves
912 are exchanged between two ultrasonic transducers 116 and 118
and reflected on a reflection surface 914 in this example. Generalizing
this principle, a plurality of reflection surfaces 914 and, accordingly,
multiple reflections, may also be used.
[0035] In the case of a reflection system of this type, protrusions
122 upstream from ultrasonic transducers 116 and 118 are also formed.
In the exemplary embodiment depicted in FIG. 9 these protrusions
122 are fused into a single protrusion. Also in this example, turbulators
212 may be advantageously used.
[0036] In the exemplary embodiment of FIG. 9 the components of
ultrasonic flow meter 910 are integrated into an insertion sensor
916. Insertion sensor 916 includes the two ultrasonic transducers
116 and 118 a space 918 between these ultrasonic transducers 116
118 and a reflection element 920 which is provided with reflection
surface 914. Space 918 may be used, for example, for integrating
an electronic terminal device and/or an electronic control device
of ultrasonic flow meter 910. The electronic terminal device and
the electronic control device thus become components of insertion
sensor 916. The signals of ultrasonic flow meter 910 may thus be
processed entirely or partially, for example, in insertion sensor
916.
[0037] Furthermore, insertion sensor 916 has a bracket 922 which
connects and holds the individual components in alignment. In this
exemplary embodiment, turbulators 212 are also secured by bracket
922 of insertion sensor 916 and thus form an integral component
of insertion sensor 916.
[0038] Reflection element 920 is situated in flow pipe 110 at a
distance from the wall of flow pipe 110 so that fluid 112 may flow
around it on both sides. This distance between flow pipe 110 and
reflection element 920 allows any water droplets or other contaminants
contained in the flow to deposit on the wall of flow pipe 110 as
wall film 924 prior to flowing through ultrasonic flow meter 910.
This wall film 924 i.e., the liquid contained therein, may flow
through flow pipe 110 without wetting reflection surface 914 or
interfering with the reflection of ultrasonic waves 912. The above-described
device having insertion sensor 916 also has considerable advantages
over conventional devices regarding its susceptibility to interference
by liquids and contaminants.
[0039] Bracket 922 of insertion sensor 916 may be designed in particular
in such a way that it offers minimum flow resistance to the flow
of fluid 112. Furthermore, bracket 922 may be designed in such a
way that reflection element 920 together with bracket 922 forms
a trough-shaped unit. This unit may, for example, have a plurality
of additional openings through which fluid 112 outside of insertion
sensor 916 is connected to fluid 112 within insertion sensor 916.
Reflection element 920 may have a flat or even a curved design,
for example, to focus ultrasonic waves 912.
[0040] As in the above-named exemplary embodiments, alternative
types of turbulators 212 may also be used in the exemplary embodiment
of FIG. 9. Additional turbulators 212 may also be installed at different
points of insertion sensor 916 for example (e.g., via an additional
bracket) between ultrasonic transducers 116 and 118.
[0041] Instead of turbulators 212 used in the above-described exemplary
embodiments, which protrude into the flow of fluid 112 flow grooves,
for example, may also be used in main flow direction 210 of fluid
112. Exemplary embodiments of this type are illustrated in FIGS.
10 11 and 12. FIGS. 10 and 12 again show cutaway views of an area
of the exemplary embodiments having section planes parallel to main
flow direction 210. In contrast, FIG. 11 shows a view from below
of the area illustrated in FIG. 10.
[0042] In these exemplary embodiments, flow grooves 1010 are embedded
into the wall of flow pipe 110 upstream from ultrasonic transducers
116 in main flow direction 210. These flow grooves 1010 are depressions
in the wall of flow pipe 110 and have a wedge-shaped design both
in the plane of the drawing according to FIGS. 10 and 12 and perpendicularly
thereto in the plane of the drawing according to FIG. 11. These
flow grooves 1010 are again situated periodically perpendicular
to main flow direction 210 of fluid 112 the tips of wedge-shaped
flow grooves 1010 pointing against main flow direction 210. As in
the above-mentioned exemplary embodiments, the periodic arrangement
of flow grooves 1010 causes longitudinal eddies 510 to form in protrusion
122 upstream from ultrasonic transducer 116 (see, for example, FIG.
5). As in the above-described exemplary embodiments, the measuring
accuracy is thus substantially improved once again.
[0043] Alternative designs of flow grooves are also possible, for
example flow grooves having rounded walls, as long as these flow
grooves also have the effect of forming longitudinal eddies. A combination
of flow grooves with turbulators 212 protruding into the flow of
fluid 112 for example, according to one of the above-described
exemplary embodiments, is also conceivable.
[0044] Furthermore, as shown in the exemplary embodiment according
to FIG. 12 the combination of flow grooves 1010 (and also turbulators
212 protruding into the flow) with specially designed protrusions
122 is also possible. In this exemplary embodiment, the wall of
flow pipe 110 has a rounded edge 1210 in the area of protrusion
122. This rounded edge 1210 causes a more even flow in the area
of protrusion 122 and thus further improvement of the measuring
accuracy of ultrasonic flow meter 910. Other designs of the wall
shape of flow pipe 110 in the area of protrusions 122 are also conceivable,
for example, an extension of protrusion 122 beyond ultrasonic transducer
116. It is, however, advantageous if at least one rounded edge 1210
is involved, which results in a more even flow.
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