SI20391A - Measurement tube of ultrasonic instrument for measuring volumetric fluid throughput - Google Patents

Abstract

The measurement tube (1) of the ultrasonic instrument for measuring volumetric fluid throughput features ultrasonic transducers (T1) and (T2) with corresponding reflectors (R1) and (R2), drawn back from the fluid current. The transmitting or receiving surfaces of the ultrasonic transducers (T1) and (T2) are located in the focal points of the corresponding reflectors (R1) and (R2), which are either parabolic or part of the surface of rotational ellipsoids (E1) and (E2). Four different types of measurement tubes (1) are described, which allow the measurement of the volumetric fluid throughput involving all currently used measurement principles. According to the submitted invention factors like fluid stability, the absence of parasite ultrasonic waves, immunity to possible fluid pressure pulses and reduced disposal of small dust particles on the ultrasonic transducers and reflectors are achieved.

Description

Debeljak Zdravko, Janseva 12, SI-4240 Radovljica Hrovatin Rok, Dol pri Borovnici 88, SI-1353 Borovnica Schoolboy Borut, Frankovo naselje 160, SI-4220 Skofja Loka Zajec Damir, Janeza Puhaija 10, SI-4000 Kranj

FLUID VOLUME FLOW VOLUME FLUID MEASURING PIPE

The field of technology

The invention belongs to the field of technology of ultrasonic fluid flow meters. According to MPK, it is rankedGOlF 1/66.

Technical problem

The invention solves the technical problem of the construction of a measuring tube of an ultrasonic fluid flow meter, which would least disturb the velocity profile of the fluid flow and thus minimize parasite ultrasonic waves.

The state of the art

The solutions available so far include ultrasonic transducers either in the walls of the measuring tube (EP 440867, EP 559938) or in the deep pockets of the measuring tube (DE 4010148, DE 3941546). The emitted ultrasonic transducer emitted by the ultrasonic wave falls, after several reflections from reflections, onto the receiving ultrasonic transducer. Multiple flights in the direction transverse to the direction of flow are needed in order to determine more precisely the average velocity of the fluid. The disadvantages of these solutions are mainly fluid disturbances that cause the speed profile to be unstable. Fluid disturbance caused by changes in the transverse dimensions of the measuring tube causes an amplitude and phase oscillation of the signal, which again reduces the accuracy and stability of the meter. In addition, parasite waves impair the signal-to-noise ratio.

In some embodiments, parasite waves are further damped by obstructions (DE 3941544) or by indentations and protrusions on the walls of the measuring tube (DE 4010148).

Another embodiment of the literature cited has a measuring tube of circular or rectangular cross section with axially mounted ultrasonic transducers (EP 580099, EP 907069, EP 682773). One of the drawbacks of these solutions lies in the convoluted fluid flow paths, which can cause turbulence and increased pressure drop. They minimize this problem with special design solutions. Such embodiments require the use of ultrasonic transducers that sound the measuring tube homogeneously (cross-section).

The inventor is not satisfied with the existing solutions, so he proposes a new design of the measuring tube without fluid obstacles and with such installation of ultrasonic transducers, which does not produce parasitic ultrasonic waves.

Description of the new solution

The essence of the new solution lies in the flat walls of the measuring tube and ultrasonic transducers withdrawn from the fluid flow. With the help of ultrasound reflectors, the required shape of the ultrasound beam is achieved at the inlet of the fluid flow and upon arrival at another transducer (receiver). As there are more procedures for measuring the volume flux of fluid, depending on the paths of the ultrasonic beam, there are also more variants of measuring tubes according to the present invention. Figures 1 to 4 show four different variants of measuring tubes with their associated ultrasonic transducers, namely:

-3Figure 1: Longitudinal section of a measuring tube with a transmitter and receiver ultrasonic transducer and parabolic reflections, all of which are withdrawn from fluid flow.

Figure 2: Longitudinal section of the measuring tube as in Figs. 1 with only a shorter distance between the inverters.

Figure 3: Longitudinal section of a measuring tube with a transmitter and receiver ultrasonic transducer and elliptical reflectors, all of which are withdrawn from the fluid flow.

Figure 4: Longitudinal cross section of a measuring tube with a transmitter and receiver ultrasonic transducer and parabolic reflections, the path of the ultrasonic wave in the tube being in the direction of the fluid flow axis.

In the following, all four variants will be described in more detail. Because fluid flow measurement procedures represent a state of the art, the description will only cover as much as is necessary to understand the new solution.

The measuring tube 1 shown in Figure 1 has an upper wall 11 and a lower wall 12 straight. Both walls are parallel. There are two openings on the upper wall 11, each leading to a space with an ultrasonic transducer T1 or T2 and a reflectance R1 and R2 respectively. The placement of the transducers shall be such that the direction of transmission and reception of the ultrasonic wave towards the middle part of the measuring tube 1. The reflections Rl and R2 are parabolic. The ultrasonic waves emanating from the ultrasonic transducer Tl or T2, after reflection from the reflector Rl or R2, propagate into the fluid flow as a plane wave without divergence, which causes no parasitic waves to form in the measuring tube. The emitted ultrasonic wave, after multiple reflections from walls 11 and 12, enters the second opening and collects after reflection from the reflections R1 or R2 on the surface of the transducers T1 and T2, respectively, which are placed in the focus of the reflections R1 and R2 respectively.

The essential difference and advantage over the solutions so far is that the walls 11 and 12 of the measuring tube are 1 straight and without obstructions, which means that they do not cause turbulent disturbances in fluid flow. Due to the convergence of the sound beam, no parasite waves are produced before entering the fluid stream. Fluid stability of the velocity profile of the current means greater stability of the meter, and the absence of parasite waves increases the accuracy of the meter.

The embodiment of the measuring tube 1 shown in Figure 2 differs from the previous one only in that the ultrasonic transducers Tl and T2 are located above the middle part of the measuring tube 1 and emit and receive ultrasonic waves into and out of the direction (terminals) of the measuring tube 1. The advantage of this embodiment is the reduced full length of the measuring tube 1.

In the case of the measuring tube 1 shown in Figure 1, the change in the direction of the ultrasonic wave is less than 90 degrees, while in the case of the variant shown in Figure 2 it is greater than 90 degrees.

-4, which means a narrower beam and a smaller opening in the upper wall 11 of the measuring tube 1. A smaller opening means again a smaller fluid disturbance, which is especially important when measuring the flow of liquids, so this design is more suitable for changing the flow of liquids than it is for changes. The gas flow can advantageously be utilized by the variant shown in FIG. 2.

Measurement tube 1 shown in Figure 3 has reflections RI and R2, which are part of the sheath of rotary ellipsoids El and E2. The ultrasonic transducers Tl and T2 are located in the focal points Gl 1 and G21 of the rotational ellipsoids El and E2. The rotating ellipsoids are arranged so that they have a common focal point G12 and G22 respectively. The lower wall 12 of measuring tube 1 is positioned to mirror the upper wall 11 of measuring tube 1 through the top G12 of the ellipsoid El 1. The wave resulting from the ultrasonic transducer Tl or T2 is converged towards the lower wall after reflection from the RI or R2 reflector. 12 of the measuring tube 1 and then to the mapped focal point Gl2 or G22 on the upper wall 11 of the measuring tube 1. After reflection, the wave propagates divergently to the reflector RI or R2, which then converges it to the receiving transducer T1 and T2, respectively.

The advantage of this solution is, in addition to fluid stability, the absence of parasite waves due to the convergent entry of ultrasonic waves into the opening of the measuring tube.

Figure 4 shows the fourth variant of measuring tube 1. In this case, too, the ultrasonic transducers Tl and T2, with their respective reflections RI and R2, are positioned out of the fluid flow. Both reflectors are parabolic. The ripple emanating from the reflector is a straight, non-divergent wave that enters the fluid parallel to the axis of the fluid flow. This parallel wave does not cause parasite waves in the measuring tube 1 to propagate obliquely into the pipe walls. The ultrasonic transducers Tl and T2, with their respective reflections RI and R2, are removed from the ends of the measuring tube so that fluid can enter and exit the measuring tube 1 smoothly and are separated from the fluid by walls 111 and 112 respectively.

The advantages of the proposed solutions are, in addition to those already mentioned, the lower sensitivity of ultrasonic transducers to possible fluid pressure shocks and the deposition of fine dust particles present in the fluid stream but too small to be eliminated by the sieve at the inlet.

Processes for changing the free-flowing fluid flow, except for the process for which a novel solution is shown in FIG. 3 are understood without special explanation, and the procedure for changing the fluid volume flow in which the transmitter or receiver ultrasonic transducer is in one of the focal points of the rotary ellipsoid is described in file DE 19549162.

Iskraemeco, d.d.

Claims (5)

Patent claims CLAIMS 1. A tube (1) of an ultrasonic fluid flow meter, characterized in that the ultrasonic transducers (T1) and (T2) with the associated reflections (R1) and (R2) are withdrawn from the fluid stream. Measuring tube (1) according to claim 1, characterized in that the reflections (Rl) and (R2) are parabolic, that the emitting or receiving surface of the ultrasonic transducer (Tl) lies at the focal point of the reflection (R1), of the ultrasonic transducer (T2) and in the focus of the reflector (R2) and that the direction of transmission and reception of the ultrasonic wave is directed towards the middle or middle part of the measuring tube (1). Measuring tube (1) according to claim 2, characterized in that the transducers (Tl) and (T2) with the associated reflectors (Rl) and (R2) are located above the middle part of the tube (1) and emit and receive ultrasonic waves in and out of connection of measuring tube connections (1) Measuring tube (1) according to claim 2, characterized in that the reflections (R1) and (R2) give a straight, non-divergent ultrasonic wave whose axis is parallel to the axis of the fluid flow. Measuring tube (1) according to claim 1, characterized in that the reflections (R1) and (R2) are parts of the sheath of rotary ellipsoids (El) and (E2) having in common other focal points (G12) and (G22), the emitting and receiving surfaces of the ultrasonic transducers (Tl) and (T2), respectively, lie on the focal points (Gl 1) and (G21) of the respective reflections (R1) and (R2). Iskraemeco, d. d.