Ultrasonic flow counter with sound deviation

The invention relates to an ultrasonic meter for determining the flow volume a flowing liquid by a propagation time measurement, in particular Differential transit time measurement, an ultrasonic signal in a measurement path a flow channel between two preferably switchable ultrasonic transducers extends laterally adjacent to the flow channel of the measuring section are arranged, wherein the iw injected perpendicular to the axis of the measuring section Ultrasonic radiation on reflectors iw perpendicular to the flow channel is deflected.

If you want to build an ideal ultrasonic meter with differential transit time measurement, would be the arrangement of the sound-emitting and the sound receiving element so arranged that<sl><li>a) the sound propagation direction is parallel to the main flow,</li><li>b) undergoes the flow no distraction by the transducer,</li><li>c) the sound beam sufficiently large areas of the flow area detected,</li><li>d) flat airfoil independent acoustic wavefronts without reflections present (piston profile)</li><li>e) the noise level outside the medium to be measured zero and</li><li>f) sound higher order modes are equal to zero.</li></sl>

Receivables a) - c) but would have the consequence that the level of the sound transducer to flow freely through the media.

Receivables d) - f) are real components of sound transducer and to achieve measuring tube never because this requirement theoretical constraints describe (z. B. ideal reverberant measurement path, piston vibrator without radial modes, etc.).

In the practical construction of an ultrasonic meter is clearly deviates from the ideal shape from by either the sound propagation direction not parallel to the flow aligns, or used flow guidance elements which flow the order the transducer passes.

In both cases, it comes through airfoil changes and vortices to changes in differential runtime behavior.

Ultrasonic meters that do not parallel to the flow direction of sound leadership, always have the problem only parts of the flow cross section for detect and are not airfoil independently. Turbulence can partly cause significant measurement errors.

Considering the ultrasonic meter with flow diversion and directly opposite Sound conversion elements so results in the following:

Within a defined measuring section this counter satisfies approximately the Ideal conditions. Sound direction is parallel to the flow direction and sound wave can basically cover the entire pipe cross section. In input and Lead-out area are formed but cross currents and eddies are no longer parallel flow to the acoustic wave propagation. These disorders may falsification generate the sound signal and the reciprocity principle is that different Flow behavior of input and outlet injured. also produced by the deflection a high flow resistance, the measuring dynamics greatly narrows.

Improvements could be accomplished by not transducers facing each other, but reflection elements are used, which are usually the sound at 90 ° deflects on parallel standing to the flow transducer. But here arises through the slanting reflecting element interference the airfoil. In particular, by the adhesion of the flow at Reflection member by the Coanda effect with difficult manageable vortex demolition the transition point from laminar to turbulent flow can be a reliable not achieve reproducible flow guidance.

The invention is therefore based on the object, an ultrasonic meter of the above kind set forth so that a higher measurement accuracy achieved becomes.

To achieve this object the invention provides that the reflectors with flow openings for the direct passage of the liquid in the Measuring section are provided between the reflectors. To the sound losses which occur by the flow openings, to minimize the reflectors preferably formed such that they on the one hand the entire cross-section of the fill the flow channel, but that flow openings strengthened in border areas and in Totschallbereichen the incident on the reflectors sound lobes the ultrasonic transducers are arranged.

In the middle, which normally constitutes the core region, one only needs very small openings. With the additional flow openings in peripheral and Totschallbereichen can reach a state with a high approximation, in which no cross-flow components, the liquid from a reflector to the other reflector is smooth strong, so that the total travel distance is exploited optimally between these reflectors. The flow openings, the iw cylindrical channels, as well as elongated slots may be, possibility to further embodiment of the invention in the range of angles arranged extending to the flow direction of the stage reflectors be. This design of the openings in substantially perpendicular to Longitudinal axis of the measuring section arranged step faces the reflecting surface the reflector for the sound waves not interrupted, because the end the overlying inclined surface to the beginning of the underlying Inclined surface coincide, and thus the flow openings for the Ultrasonic transducers coming sound waves are virtually invisible.

Alongside the aforementioned formation of the flow openings, especially in the Marginal areas or Totschallbereichen can, conversely, an arrangement be the flow openings are provided such that they - just in the center of the sound cone lying - the sound cone of the ultrasound transducer distort through specific losses towards a rectangular function. in principle sends namely a piston vibrator with respect to its main lobe, a parabola-like Sound cone from. The demand for the sound cone for ideal propagation time delay measurement but is a rectangular function. With the openings in the reflective element you can now install targeted acoustic losses so that the reflected Shaft of a square wave comes close.

The inventive development of an ultrasonic meter with flow openings in the reflectors results in such a flow pattern, that no flow sections are formed, the undefined flow patterns include. You will lose on the other side through the flow openings Sound components that affect the increased attenuation of the received signal. If these attenuation losses but at a manageable level, which in practice is no problem, this results in no increase in measurement uncertainty. When dimensioning the openings such that one the edge and Totschallbereiche with larger openings provides as the core area, need the flow openings in the core area to only very small formed be. These serve primarily to adhesive flows, the angle at the lying plate occur, to stop. The through flow openings formed flow nozzles act as free radiator and direct the flow equal.

The inventive construction has a number of advantages. Firstly, no flow deflection required and on the other reduce the Totwasserräume with induced secondary flows to the converter trough. The Housing can over the rectangular inlets and outlets in the area of opposing transducer designed constructions much be made simpler. The actual measuring the effects of ultrasonic transit time generating flow section begins directly at the reflective level, thereby results in a very compact design.

Moreover, the inventive construction is also the possibility by the special design of the flow openings disorders of the airfoil to clean up in addition to the reflection plane. To this end may be provided with airfoils the flow openings, for example, characterized in that the ends of the openings on the reflection side expanded, the effect can be further improved even when the Flow openings formed tapered.

Finally, it is also within the scope of the invention, the inclination of the reflector sections so different to select that individual from Sections reflected reflected partial acoustic beam to the flow direction inclined be and on the cross section of the measurement path offset reflector sections incident. This results in a sound guide in which the principle of equality significantly improved for sound propagation in and against the flow direction and is made symmetrical, so that signal disturbances caused by induced secondary flows arise in the Totwasserbereichen be compensated. These different design of the inclination of individual reflector portions is thereby preferably in turn combined with the aforementioned construction in the flow openings in the range of perpendicular to the flow direction extending stages ie between two differently inclined reflector sections are arranged.

Further advantages, features and details of the invention result from the following description of some embodiments with reference to the Drawing. They show:<dl tsize="7"><dt>Fig. 1</dt><dd>a schematic view of a known ultrasonic counter with opposing transducers and flow diversion before these converters,</dd><dt>FIG. 2</dt><dd>a schematic view of an ultrasonic meter in which the ultrasonic radiation the laterally arranged next to the measuring section Ultrasonic meter by arranged in the flow channel reflectors is deflected,</dd><dt>Fig. 3</dt><dd>an enlarged partial section through one half of a corresponding FIG. 2 formed ultrasonic meter with inventively formed provided with flow openings reflectors,</dd><dt>Fig. 4</dt><dd>an ultrasonic meter according to the invention in which the reflectors have differently inclined reflector sections in order in both achieve operational directions symmetrical as possible ultrasound propagation times,</dd><dt>Fig. 5</dt><dd>an enlarged section of a stepped reflector portion corresponding to the detail in Fig. 5 in Fig. 4 for the formation of Airfoils to</dd><dt>Fig. 6</dt><dd>a schematic representation of the distortion of the sound cone in the range of flow openings to achieve a possible rectangular sound radiation characteristic in the range of Measuring distance.</dd></dl>

Figs. 1 and 2 show the basic structure of a known ultrasonic meter. In Fig. 1 while a typical ultrasonic meters is drawn, wherein the housing 1 with the two ultrasonic transducers 2 and 3 opposing is provided with angled inlet and outlet nozzles. 4 and 5 In the inlet area 13 and outlet portion 14 formed thereby cross currents and eddies that no longer parallel to the sound wave propagation in the direction of connection of the Ultrasonic transducer 2 and 3 flow.

In the structure diagram of an ultrasonic meter according to FIG. 2, the ultrasonic transducer 2 and 3 laterally next to the actual measuring section 6 of the housing 1 arranged. The sound in and -ausstrahlung is essentially perpendicular to the axis of the measuring section 6, with reflectors 7 and 8 necessary for the ensure deflection of the ultrasonic radiation parallel to the flow direction. Also here formed by the slanting reflectors 7 and 8 of the disorders The airfoil 13 ', 14', in particular, by the adhesion of the flow at Reflector by the so-called Coanda effect with difficult manageable vortex demolition.

According to the invention in accordance with an ultrasonic meter with the construction principle Fig. 2 - as in the embodiments of Figures 3 to 6 individuals. shown is - a special training of the reflectors 7 ', 8', 7 '', 8 '' are provided, wherein in the iw the entire cross section of the measuring casing 1 passing through reflectors are flow openings 9, 9 ', 9' 'is formed. These Flow openings for the direct passage of the liquid in the measuring section 6 between the reflectors 7 ', 8' or 7 '', 8 '' have a number of advantages. So is firstly no flow deflection required and Totwasserräume with induced secondary flows are reduced to the converter trough. One has a simple construction of the housing without the side intakes and outlets as in the ultrasonic meter of FIG. 1. The design of the openings Disturbances of the flow profile can be additionally adjusted. Of the the actual measuring effects generating flow section so the area in the measuring section 6 starts directly to the reflection planes resulting in a very compact design results.

While in the simplest embodiment of FIG. 3, the cylindrical and round Holes or formed as slots flow openings 9 formed substantially equally large and uniformly distributed arranged are, you will be in practice more tend the openings to be distributed such that they are larger or more numerous in peripheral and Totschallbereichen than in Core area of ​​the incident on the reflectors sound lobes. This is illustrated in Figure but not illustrated, since, depending on the type of transducer and the training the sound lobes, the arrangement can be designed differently so far. It can also be provided that the openings 9 respectively in the range of Stages of the reflectors are so in the perpendicular to the longitudinal axis of the Housing 1 extending walls of these levels (as in the case of the flow openings 9 'in Fig. 4). In this way, the side borders of seen the ends of adjacent sections of the reflectors directly to each other , so that absolutely no sound loss through the flow passage openings occurs upon impact of beam from the transducer.

In the embodiment of FIG. 4 is a variant in the the reflectors 7 '' and 8 '' in two differently inclined portions divided in such a way are that each of a reflector portion, the part sound lobes 11a, 11b and 12a, 12b are directed to the respective other reflector portion, such as This is shown in detail. Characterized in that the bundle which above the free jet is reflected occurs on the second reflector bottom and vice versa, there is the advantage that the principle of equality for the propagation of sound in and against the flow direction is significantly improved and thus the Signal interference caused by secondary flows induced in the Totwasserbereichen arise, be compensated. Here, it is also possible for only the opening 9 form 'as a flow passage.

In all cases, as shown in Fig. 5 is indicated, the respective flow opening 9, 9 ', 9' 'in the flow exit area with a flow separation edge forming Fase be 13 provided. The flow separation edge formed thereby causes that of leaving the gap open jet through the obliquely formed Surface of the reflection element is not deflected. This effect can be still characterized reinforce that the flow aperture is shown 9 'as shown in Fig. 5 conical forms.

Apart from a basic principle of the arrangement of the flow passages 9, 9 ', 9' 'such that they more numerous in peripheral and Totschallbereichen or are arranged with larger opening widths than in the core area, you can only very little in the core openings need serve the Adhesive flows to prevent occur at the slanting reflectors, you can see the arrangement and distribution of the flow passage openings also optimize specifically to the effect that through the flow passages 9, 9 'or 9' '- as indicated in Fig. 6 - targeted acoustic losses be obtained by starting with one of the usual ultrasonic main lobes Piston vibrator with parabolic similar sound lobe of the demand for the ideal Runtime measurement for a more rectangular function of beam spread more to comply. The built-in sound loss through this Case, not the area of ​​a stage arranged flow opening 9, 9 ', 9' 'in accordance with Fig. 6 results in a loss of sound radiated sound S in the middle of the parabola-like sound beam to the more rectangular distribution S '' leads. S 'is the reflected sound in the reflection plane.

The invention is not limited to the embodiments illustrated. As stated above, the formation of the flow openings 9, 9 ', 9' 'and their Distribution on the reflectors in different ways depending carried what specific benefits you respond with their help especially and strengthen would like.