RU2169350C2 - Process measuring and controlling parameters of flow of liquid or gas in vessel with elastic walls - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: process can be employed to measure flow rates in pipe- lines where installation of traditional flowmeters is difficult. Process measuring and controlling parameters of flow of liquid or gas in vessel with elastic walls includes excitation of elastic waves in the form of pulses along and against flow, measurement of time of passage by pulses of base distance from radiator to detector in two directions: along and against flow, determination of value of velocity and flow rate by difference of time of passage of base distance by these pulses. Characteristic feature of given process consists in excitation of ultrasonic pulses in elastic walls of vessel. In this case pair " radiator-detector " is located on analogous wall of vessel and velocity V of flow is found with the use of mathematical relation given in description of invention. Second pair " radiator-detector " is employed to excite and receive ultrasonic wave. Radiator and detector of that pair are placed in order opposite to that of first pair and at same base distance. EFFECT: enhanced measurement precision with simplified realization of process. 1 cl, 1 dwg

Description

 The invention relates to measuring equipment and can be used in monitoring systems and measuring the speed and flow rate of liquid and gaseous products transported through pipelines. Possible areas of application of this invention: production and transportation of oil and gas products, water supply, production of medical equipment and biomedicine.

 Most of the known methods for measuring the speed and flow rate of liquids in pipelines that are not related to mechanical flow disturbance and violation of the integrity of the pipeline are based on the use of ultrasonic sensors [see Birger A.B., Brashnikov I.S. Ultrasonic flow meters. M .: Metallurgy, 1964]. In this case, the pulse signal sent by the ultrasonic generator passes through the transported medium, the time of its passage is measured and compared with the time of passage of a similar signal in the opposite direction. To do this, use a measuring circuit with several acoustic channels (at least two) [see author St. USSR N 1247659, class G 01 F 1/66, 01.07.83, publ. 07/30/86. Bull. N 28; N 1453178, CL G 01 F 1/66, 04.06.79, publ. 01/23/89. Bull. N 3] or in the scheme with one channel change the relative direction of the ultrasonic wave and flow [see USSR author's certificate N 1206618, cl. G 01 F 1/66, 12.22.83, publ. 01/23/86. Bull. N 3].

 The closest in technical essence to the invention is a method of measuring the flow rate of liquids [see USSR author's certificate N 1247659, cl. G 01 F 1/66 from 01.07.83, publ. 07.30.86 Bull. N 28.], including the radiation of an ultrasonic pulse along the flow and against the fluid flow at different angles to the axis of the flow and the determination of the difference in the travel times of these pulses of the base distance.

 The described measurement method uses the following provisions.

 1. It is assumed that the signal passing in the medium under study is not distorted and is not delayed due to the influence of the walls of the vessel, which is not true, because the walls have finite elasticity and fluctuations in the density of the medium cause fluctuations in the walls. In addition, the attenuation of ultrasound leads to the fact that the main power of the wave is concentrated near the walls.

 2. The use of a formula for recalculating the difference in the propagation times of pulses into a measurable quantity.

 The disadvantages of this method is the complexity of the implementation and the lack of accuracy of the measurements, due to not taking into account the above factors and the approximate nature of the recalculation formula.

 The objective of the present invention is to improve accuracy while simplifying the implementation of the method by using the dependence of the speed of propagation of elastic waves in the walls of the vessel on the velocity of the fluid flow in the vessel.

The problem is solved in that in the method of measuring and monitoring the parameters (speed and flow rate) of a liquid or gas flow in a vessel with elastic walls, including excitation of elastic waves in the form of a pulse along the flow and against the flow, measuring the time the pulse travels the base distance from the emitter to the receiver in two directions: along and against the flow, determining the magnitude of the velocity and flow rate by the difference in the times the pulses travel the base distance, ultrasonic pulses excite in the walls of the vessel, while and the emitter-receiver is located on the same wall of the vessel, and the flow rate V is determined from the ratio:
V = 2 (2π) ⁴ ΔtT ^-2 L ⁶ RS ^-1 λ ^-4 ,
Where:
S is the distance between the same source and receiver;
Δt is the time difference between two pulses of the base distance along and against the flow;
λ is the elastic wavelength in the pipe wall, which is the pulse carrier;
T = (ρ / E) ^1/2 a - unit of dimension of time;
L = [ρah / (2ρ _o )] ^1/2 - unit of dimension of length;
R = ρ $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ / [3 (1-μ ² ) ρ ² ] - a value that determines the degree of interaction of waves in a liquid and elastic waves in the walls of a vessel, the so-called cylindrical stiffness;
ρ is the density of the wall material;
ρ _o is the density of the liquid or gas;
a is the radius of the vessel;
h is the wall thickness of the vessel;
E - Young's modulus of the material of the walls of the vessel;
μ is the Poisson's ratio of the material of the walls of the vessel.

 In addition, it is possible to implement the method when a second pair of emitter-receiver is used to excite and receive the ultrasonic wave, while the emitter and receiver of the second pair are located in the reverse order with respect to the first pair, at the same basic distance.

 The invention is illustrated in the drawing, where 1 is a vessel with elastic walls; 2, 3 - sources of a pulse signal; 4, 5 - receivers of a pulse signal.

 The method is as follows. On the walls of the pipe 1 of the same name, in which a fluid or gas flow propagates at a speed of V, a pair of sensors are located at the same distance from each other, two of which 2, 3 are used as sources of a pulse signal, and two - 4, 5 - as receivers. The signal sent by source 2 and received by receiver 4 propagates in the vessel wall in the direction along the flow, and the signal sent by source 3 and received by receiver 5 propagates in the wall against the stream. The measured quantity is the time difference Δt of the propagation of two signals, arising from the difference in the velocities of the waves propagating in opposite directions. The determination of the flow rate is carried out in accordance with formula (1) (in SI units). Moreover, the dependence of the elastic wave velocity in the vessel wall on the flow velocity in the vessel allows the use of a measurement scheme in which the ultrasonic wave propagates along the vessel wall, and not at an angle to it, as in the known solutions. The exclusion from the calculation formula of the angle between the direction of propagation of the ultrasonic wave and the direction of the flow velocity can improve the measurement accuracy.

 Knowing the value of the flow rate in the pipeline and the cross-sectional area of the pipeline, it is easy to determine the flow rate and to control it.

 The economic effect of the use of the invention is achieved by taking into account additional factors leading to a more accurate assessment of the measured values and by simplifying the design of the measuring circuit.

Claims (2)

1. A method of measuring and monitoring the parameters of a fluid or gas flow in a vessel with elastic walls, including the excitation of elastic waves in the form of pulses along the flow and against the flow, measuring the time it takes for the pulses to travel the base distance from the emitter to the receiver in two directions: along and against the flow, determining the speed and flow rate by the difference in the times the pulses travel the base distance, characterized in that the ultrasonic pulses excite in the elastic walls of the vessel, while the emitter-receiver pair is Laga on the corresponding wall of the vessel and the flow velocity V is determined from the relation
V = 2 (2π) ⁴ ΔtT ^-2 L ⁶ RS ^-1 λ ^-4 ,
where S is the distance between the same source and receiver;
Δt is the time difference between two pulses of the base distance along and against the flow;
λ is the elastic wavelength in the pipe wall, which is the pulse carrier;
T = (ρ / E) ^1/2 a - unit of dimension of time;
L = [ρah / (2ρ _o )] ^1/2 - unit of dimension of length;
R = ρ $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ / [3 (1-μ ² ) ρ ² ] - a value that determines the degree of interaction of waves in a liquid and elastic waves in the walls of a vessel, the so-called cylindrical stiffness;
ρ is the density of the wall material;
ρ _o is the density of the liquid or gas;
a is the radius of the vessel;
h is the wall thickness of the vessel;
E - Young's modulus of the material of the walls of the vessel;
μ is the Poisson's ratio of the material of the walls of the vessel.  2. The method according to claim 1, characterized in that for the excitation and reception of the ultrasonic wave, a second pair of emitter-receiver is used, while the emitter and receiver of the second pair are located in the opposite order to the first pair at the same base distance.