JPH11295119A - Flow detecting method of hydraulic machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a high-precision flow detection securely and inexpensively regardless of properties of a liquid to be detected, by improving S/N ratio of ultrasonic received signals. SOLUTION: In this flow detecting method, in which a velocity distribution on a prescribed section in the channel in a rainwater drainage pump is detected by a pulse-Doppler type ultrasonic current meter, and a flow rate Q is calculated by using the detected velocity distribution V(x) and a sectional area of the prescribed section, bubbles 105 are supplied into pumped storage by a particle supply means 102 on the lower part of a suction bell mouth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a flow rate of a hydraulic machine such as a pump or a water turbine, and more particularly to a method of detecting a flow rate of a hydraulic machine using an ultrasonic flowmeter.

[0002]

2. Description of the Related Art For example, when it is desired to detect the flow rate of a large-diameter pump at the site where the pump is installed, no fixed equipment for detecting the flow rate such as an electromagnetic flow meter, a throttle flow meter, and a weir is provided. In this case, it is convenient to perform detection from outside the pump using an ultrasonic flowmeter.

For example, in a method using an ultrasonic flow meter of the propagation difference type, a transmitter / receiver is provided at each of two places separated in the axial direction of an inner wall of a pump discharge pipe. Then, the reflected wave of the ultrasonic wave output from one of the transmitters at the opposing discharge pipe inner wall is received by the other receiver, and the ultrasonic wave output from the other transmitter is transmitted through the opposing discharge pipe. The reflected wave on the wall is received by one of the receivers, the average flow velocity in the discharge pipe is determined based on the difference in propagation time between the two cases, and the pump flow rate is calculated based on the average flow velocity. At this time, if the length of the straight pipe portion on the upstream side of the flow rate detection unit is sufficiently long, the flow velocity distribution in the cross section of the flow path to be detected will be substantially uniform. Since the length cannot be made too long for the above reasons, there is a radial flow velocity distribution on the cross section of the detection flow path. However, in the ultrasonic wave flow meter of the above-described propagation difference type, only the average value of the flow velocity over the measurement line through which the ultrasonic wave passes is detected, and the radial flow velocity distribution cannot be detected. Become
The detection accuracy was reduced.

To solve this problem, Japanese Patent Laid-Open No. 10-1
As described in Japanese Patent No. 25633, there has been proposed a method of detecting a flow velocity distribution in a cross section of a detection flow path using a pulse Doppler ultrasonic flow meter. That is, in this conventional technique, ultrasonic waves emitted obliquely to the pipe axis from a transmitter provided on the outer wall of the pump discharge pipe are scattered and reflected by particles contained in the detection liquid, and the scattered and reflected Sound waves are received by the receiver. Then, the velocity of each particle is obtained from the Doppler shift frequency included in the received signal, and the position of the particle is obtained from the reciprocation time of the ultrasonic wave to each particle, thereby detecting the radial flow velocity distribution. And by integrating this distribution over the entire tube,
Detect the flow rate.

[0005]

The above-mentioned prior art utilizes the reflection and scattering of ultrasonic waves by particles present in the liquid to be detected. Therefore, the presence of particles in the liquid is indispensable. However, for example, drainage pumps used during floods contain a large amount of sediment particles in the pumping, making it relatively easy to detect the flow rate. S of received signal
In some cases, the / N ratio decreases, and it becomes difficult to detect the flow rate. In addition, a circulating water pump that circulates cooling seawater at thermal power plants and nuclear power plants reduces the concentration of
Since it is lower than river water, flow rate detection becomes more difficult.
In particular, when the pump discharge pipe is made of a thick iron pipe, the transmission loss and attenuation of the ultrasonic wave increase, which also lowers the S / N ratio of the ultrasonic reception signal, which tends to further increase the difficulty. . In order to avoid this, there is a method of strengthening the transmitted wave, but this case is not preferable because the cost of the apparatus is greatly increased.

[0006] An object of the present invention is to provide an S / N of an ultrasonic reception signal.
An object of the present invention is to provide a flow detection method for a hydraulic machine capable of reliably and inexpensively detecting a flow with high accuracy regardless of the property of a liquid to be detected by improving the ratio.

[0007]

Means for Solving the Problems (1) In order to achieve the above-mentioned object, the present invention provides a method of pulsing a velocity distribution in a predetermined cross section of a flow path in a hydraulic machine or a flow path located before and after the hydraulic machine. Detected by Doppler ultrasonic flowmeter, in the flow rate detection method of the hydraulic machine to calculate the flow rate using the detected velocity distribution and the cross-sectional area of the predetermined cross section, on the upstream side of the predetermined cross section of the flow path, Solid particles or gas particles are supplied into the liquid to be detected by the particle supply means. In the pulse Doppler type ultrasonic anemometer, the ultrasonic wave transmitted from the transmitter is scattered / reflected and received by the receiver, and the Doppler shift frequency of the received wave is analyzed to calculate the flow velocity distribution. Generally, the degree of scattering / reflection at the boundary of an ultrasonic wave increases as the acoustic impedance (= density × sound velocity) of the medium greatly differs. In other words, if solid or gaseous particles with significantly different acoustic impedances exist in the liquid, the ultrasonic waves will be greatly scattered on the surface of those particles.
It will be reflected. In the present invention, the particles are positively supplied from the outside into the liquid to be detected by the particle supply means, thereby promoting the scattering and reflection of the transmitted wave and increasing the intensity of the received wave. The ratio can be improved. Therefore, regardless of the properties of the liquid to be detected, high-accuracy flow rate detection can be reliably performed. At this time, unlike the case where the intensity of the transmitted wave is increased, there is no significant cost increase.

(2) In the above (1), preferably,
The particle supply means supplies bubbles as the gas particles.

(3) In the above (1), preferably, the particle supply means includes an air source and an air supply pipe connected to the air source. Thereby, for example, air from an air source such as a compressor or a compressed air cylinder can be guided to the air supply pipe and supplied as gas particles into the liquid to be detected.

(4) In the above (1), preferably, the particle supply means includes a high-pressure liquid source, an ejector that sucks air and mixes the air with the high-pressure liquid from the high-pressure liquid source, and the ejector. And a discharge pipe connected to the discharge pipe. Thus, the high-pressure liquid in which air is mixed in the state of particles (bubbles) can be guided to the discharge pipe, and the air particles (bubbles) can be supplied to the detection target liquid while being contained in the high-pressure liquid.

(5) In the above (1), preferably, the particle supply means includes a foaming agent which generates a gas by a chemical reaction with water. Thereby, a gas can be generated by causing a chemical reaction between the blowing agent and water, and the gas can be supplied as particles into the liquid to be detected.

(6) In the above (1), preferably, the particle supply means includes an electrode for inducing an electrolysis reaction of water. Thereby, an electrolysis reaction of water is induced in the detection target fluid, and a large amount of hydrogen gas particles generated at that time can be supplied to the detection target fluid.

(7) In the above (1), preferably, the particle supply means is configured such that one end portion thereof penetrates a wall defining a flow path in the hydraulic machine and communicates with the flow path and the other end. The vicinity is provided with a communication pipe that can be opened to the atmosphere. Thereby, for example, when the pressure in the flow path of the hydraulic machine is lower than the atmospheric pressure, without using the power for supplying particles in particular,
Air particles can be mixed into the detection target fluid through the communication pipe.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration in a case where a flow rate detection device that implements the flow rate detection method according to the present embodiment is applied to detect the flow rate of a vertical drainage pump for rainwater drainage. FIG. 2 is a functional block diagram showing a function of performing arithmetic processing on a detection result in (described later).
Shown in

In FIG. 1, the drainage pump is provided with a suction side in a suction tank 3 in which rainwater is stored, and is arranged so that its axis is substantially vertical. A drive shaft of a motor (not shown) installed outside the pump is provided. Pump shaft 2 connected to
And an impeller 1 fixed to the pump shaft 2, a casing 4 containing the impeller 1, a guide blade 6 fixed above the impeller 1 on the inner periphery of the casing 4, and a lower end of the casing 4. The connected suction bell mouth 5, a discharge column 7 having a lower end connected to the upper end of the casing 4, a discharge bend 8 connected to an upper end of the discharge column 7, and a relatively short bend connected to the discharge bend 8. A discharge pipe 9 having a straight pipe shape and a flow control valve 10 installed at a downstream portion of the discharge pipe 9 are provided.

The flow rate detecting device according to the present embodiment is for detecting the flow rate of the drainage pump having such a structure, and as shown in FIGS. A pulse Doppler ultrasonic flowmeter 101 for detecting a radial flow velocity distribution in the discharge pipe 9 provided with a transmitter / receiver 101a (to be described later in detail), and a radial flow velocity distribution detected by the ultrasonic flowmeter 101 A flow rate calculator 104 for calculating the flow rate based on the flow rate, a control device 103 for controlling the operation of the ultrasonic current meter 101 and the flow rate calculator 104, and air for rainwater sucked into the drain pump below the suction bell mouth 5 And a particle supply means 102 for supplying particles (bubbles).

The pulse Doppler ultrasonic current meter 101 is
An ultrasonic element 101aA provided so as to be able to transmit and receive waves at an angle θ [deg] with respect to the pipe wall of the discharge pipe 9, and the ultrasonic element 101aA
Transmitter / receiver 1 provided with resin plate 101aB for fixing
01a, a transmission pulse generator 101b for generating a pulse for flow velocity detection, a transmission amplifier 101c for amplifying the pulse and outputting the amplified pulse to the transmitter / receiver 101a, and a fluid transmitted from the transmitter / receiver 101a. A reflected wave scattered and reflected by the bubble 105 inside and received by the transmitter / receiver 101a (detailed later)
Receiving amplifier 101d for amplifying the
A Doppler shift frequency detector 101e for sequentially detecting a Doppler shift frequency of the reflected wave amplified by 1d due to the flow velocity of bubbles in the pumping water, and data of a plurality of Doppler shift frequencies detected by the Doppler shift frequency detector 101e And a sampling hold 101f that collectively outputs a predetermined number of data after holding for a predetermined period,
An A / D converter 101g for converting data output from the sampling hold 101f into a digital signal,
Data is input via the A / D converter 101g, and the variation of each bubble data due to noise, attenuation, turbulence, etc. is analyzed and processed stochastically, and one Doppler shift frequency value Δf is set for each bubble data. It has a frequency analyzer 101h that collects as [Hz], and a flow velocity distribution calculator 101i that calculates a flow velocity distribution in the discharge pipe 9 based on the Doppler shift frequency Δf from the frequency analyzer 101h.

The control device 103 includes all the components 101a to 101i of the ultrasonic current meter 101 and the flow rate calculator 1
04 and controls them, and outputs a control signal to them according to the operation status of these components.

The flow velocity detector 104 is adapted to output the discharge pipe 9 according to the velocity distribution calculated by the flow velocity distribution calculator 101i of the pulse Doppler ultrasonic flowmeter 101 and the flow path area in the discharge pipe 9.
It serves as a calculating means for calculating the flow rate in the inside (detailed later).

The particle supply means 102 includes an air source 102a installed on the pump installation floor, and an air supply pipe 102c connected to the air source 102a via a flow control valve 102b and through which compressed air is guided. The vicinity of the tip of the air supply pipe 102c is located below the suction bell mouth 5, and a plurality of air supply holes 102cA are formed in the upper outer peripheral portion thereof. Thus, a large number of bubbles 105 are supplied to the suction flow P into the drain pump. The air source 102a may be, for example, a reciprocating / rotary compressor, an air cylinder in which compressed air is compressed, or an air pipe supplied from another air source.

The procedure and operation of the flow rate detection method according to the present embodiment using the flow rate detection device configured as described above will be described below. (1-1) Generation of Bubbles In a state where the prime mover is driven to rotate the pump shaft 2 and the impeller 1 is pumping rainwater, first, the air supply pipe 102
When the flow control valve 102b provided at the position c is opened, a large number of fine bubbles 105 are ejected from the air supply hole 102cA near the tip of the air supply pipe 102c. Bubbles 105 flow into the pump due to buoyancy and suction flow P acting on themselves, pass through the impeller 1 and the guide blades 6 together with water, and are guided to the flow velocity detecting section in the discharge pipe 9 via the discharge bend 8.

(1-2) Detection of Flow Velocity Distribution Next, a plurality of ultrasonic pulses (burst wave: initial frequency fo) generated from the transmission pulse generator 101b of the pulse Doppler ultrasonic flow meter 101 and amplified by the transmission amplifier 101c [Hz]) from the transmitter / receiver 101a on the flow velocity measurement line in a direction making an angle θ with the pipe wall of the discharge pipe 9 (FIG. 1, FIG.
(See the solid arrow in FIG. 2). This burst wave is scattered and reflected by bubbles 105 existing in the fluid and distributed at respective positions in the flow channel width direction. Here, as a general property of ultrasonic waves,
As the acoustic impedance (= density x sound velocity) of the medium greatly differs, the degree of scattering / reflection at the boundary increases, but as described in the above (1-1), the bubble 105 whose acoustic impedance differs greatly from water is generated. Particle supply means 10
By actively supplying from outside in step 2, scattering and reflection of burst waves are promoted.

The reflected waves scattered and reflected in this manner return to the transmitter / receiver 101a with a propagation time corresponding to the distance from the transmitter / receiver 101a (see FIGS. 1 and 2). 2 see broken line). FIG. 3 shows the principle of propagation and reflection at this time. In FIG. 3, a burst wave (= basic wave) transmitted from the transmitter / receiver 101a is a bubble 105A in the water flow (the distance LA in the transmission direction from the transmitter / receiver 101a, the flow velocity VLA, and so on). ), Bubble 105B (LB, VL
B), bubble 105C (LC, VLC), bubble 105D (L
D, VLD) and air bubbles 105E (LE, VLE). And each reflected wave (= scattered wave) 1
52A, 152B, 152C, 152D, 152E are:
Distance x (= LA, LB, LC, L) from transmitter / receiver 101a
D, LE) corresponding to the propagation times tA, tB, tC, t
At D and tE, the signal is returned to the transmitter / receiver 101a, received, and amplified by the receiving amplifier 101d.

Returning to FIG. 2, at this time, the Doppler shift frequency detector 101e transmits the burst wave and performs sampling time Ti (where i = 1, 2,..., 5, T1 ≒ tA, T2).
(TB, T3 ≒ tC, T4 ≒ tD, T5 ≒ tE), the reflected waves 152 are transmitted via the transmitter / receiver 101a.
A, 152B, 152C, 152D, and 152E are sampled. At this time, each of the reflected waves 152A to 152E is
Due to the Doppler effect proportional to the flow rates VLA to VLE of the bubbles 105A to 105E (more precisely, the components V'LA to V'LE inclined by the angle θ: see FIG. 3), the frequency shift Δf is shifted from the initial frequency fo. is recieving. The Doppler shift frequency detector 101e calculates the Doppler shift frequency ΔfA, ΔfB, ΔfC, Δf of each of the bubbles 105A to 105E.
D, ΔfE are calculated as sampling times T1, T2, T3, T4,
The data is sequentially output to the sampling hold 101f in association with T5. The sampling hold 101f holds each bubble 1
.., And hold them until a predetermined time after the end of the input of ΔfE, and after the end of the input of ΔfE,
ΔfE is output collectively. The data of ΔfA to ΔfE are digitally converted by the A / D converter 101g, and then converted into a value in which fine variations are aggregated by the frequency analyzer 101h, and input to the flow velocity distribution calculator 101i.

Thereafter, the flow velocity distribution calculator 101i uses the sound velocity C detected in advance by a known method and separately set and inputted, and the position in the transmission direction of each of the bubbles 105A to 105E corresponding to the Doppler shift frequencies ΔfA to ΔfE. x (= LA, LB, L
C, LD, LE), x = CTi / 2 (where i = 1, 2, 2,
..., 5). Then, using the corresponding Doppler shift frequencies ΔfA to ΔfE, the initial frequency fo, and the sound velocity C, the component V ′ in which the Doppler effect is further inclined by the angle θ
Note that each bubble 1
The local flow velocities VLA to LE at the positions x (x = LA to LE) 05A to E are obtained by V (x) = CΔf / (2fo · cos θ). The obtained V (x) is input to the flow rate calculator 104.

(1-3) Flow Rate Detection Finally, the flow rate calculator 104 calculates the local flow velocity V (x) at the position x obtained above based on the radial position r = x sin θ, and calculates the local flow velocity V (x) at this position r. r),
This is used together with the radius R of the detection cross section (= D / 2: the internal diameter D is stored in advance or input via input means not shown) and the flow path height B (r) shown in FIG. hand,

[0027]

(Equation 1)

Then, the flow rate Q is calculated. The calculated flow rate Q is displayed to the operator via, for example, display means (not shown).

As described above, according to the present embodiment, after transmitting / receiving by the transmitter / receiver 101a, the transmitter / receiver 10a
It is possible to detect local flow velocities V (x) at many points on the flow velocity measurement line before receiving the wave at 1a, and to significantly improve the detection accuracy compared to the propagation velocity difference method that can detect only the average flow velocity over the flow velocity measurement line. it can. At this time, the particle supply means 102 actively supplies air bubbles 105 from the outside into the pumped water to promote the scattering and reflection of the transmission wave from the transmitter / receiver 101a. The intensity of the received wave received by the transmitter / receiver 101b can be increased as compared with the reflected wave from solid particles (fine sand, dust, etc.), and the S / N ratio of the received signal can be increased. Therefore, regardless of the properties of the liquid to be detected,
Highly accurate flow rate detection can be performed reliably. In particular, when the discharge pipe 9 is made of a thick iron pipe, the transmission loss and attenuation of the ultrasonic wave increase, and the S / N ratio of the ultrasonic reception signal decreases, which is particularly effective. At this time, unlike the case where the intensity of the transmitted wave is increased, there is no significant cost increase.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention. Such modified examples will be sequentially described below.

(1) Case of Supplying Gas-Liquid Mixed Water That is, as shown in FIG. 5, as a particle supply means 102A, a pump 110 which is a high-pressure liquid source, air is sucked and the air is supplied from the pump 110 This is a case in which an ejector (jet pump) 111 to be mixed with the liquid and a discharge pipe 112 connected to the ejector 111 and having a tip opening upward below the suction bell mouth 5 are provided. In the ejector 111, although not shown in detail, high-pressure water discharged from the pump 110 is supplied to the nozzle, and the high-speed water flow sucks air from a pipe 111a connected to the nozzle outlet. It becomes mixed water. Then, the gas-liquid mixed water recovers pressure by the conical diffuser downstream of the nozzle and is discharged to the discharge pipe 112, and the bubbles 105 are supplied to the pumping water while being included in the gas-liquid mixed water. In this modified example, the same effect as in the above embodiment is obtained.

(2) Using Chemical Reaction of Blowing Agent That is, as shown in FIG. 6, a solid blowing agent 113 which generates gas by a chemical reaction with water as the particle supply means 102B, Container 114 with built-in 113
Is provided. As the foaming agent 113, for example, dry ice that generates carbon dioxide gas upon contact with water is used. The container 114 is provided on the bottom surface of the suction tank 3, and its upper surface is covered with a net or a perforated plate. In addition, this container 1
14 is connected to a float 115 floating on the surface of the water by a mooring rope 116, so that it can be easily collected after the flow rate detection is completed. In this modified example, the same effect as in the above embodiment is obtained.

(3) When Electrolysis is Used FIG. 7A is an enlarged side view showing the vicinity of the lower end of the suction bell mouth 5 in this modification, and FIG. FIG. FIG. 8 shows FIG.
It is sectional drawing by the DD cross section in (b). These FIG.
As shown in (a), FIG. 7 (b), and FIG. 8, in this modification, as the particle supply means 102C, electrode devices 118a to 118d for inducing an electrolysis reaction of water are provided. Each of the electrode devices 118a to 118d has a pair of positive and negative poles, and is connected to a power cable (not shown) provided outside.
Electric power flows through the positive electrode 19 and between the positive electrode and the negative electrode to generate bubbles 105 of hydrogen and oxygen by an electrolysis reaction of 2H ₂ 0 → O ₂ {+ H ₂ }. In this modified example, the same effect as in the above embodiment is obtained.

(4) When applied to an axial flow type pump having a horizontal axis FIG. 9 is a longitudinal sectional view showing a schematic configuration of this modified example.
Parts corresponding to those in FIG. 1 are denoted by the same reference numerals. In FIG. 9, in this modification, as the particle supply means 102D, an intake pipe 120 whose one end near the end penetrates the wall surface of the bend 8 and communicates with the flow path and the other end near the air can be opened to the atmosphere, This is a case where a valve 121 located near the other end is provided. In this modification, in the pump operating state, the pressure near the wall of the bend 8 to which the intake pipe 120 is attached is higher than the atmospheric pressure by (water head Hs of the difference between the pump shaft center height and the water surface) + (vanes) The dynamic pressure of the flow at the entrance of the car 1 is reduced by the amount of the head. That is, since the atmospheric pressure is higher than the pressure in the bend 8, when the valve 121 of the intake pipe 120 is opened, air is sucked into the pump through the intake pipe 120. The inhaled air becomes bubbles 105 and enters the impeller 1 and is agitated, and is further miniaturized and uniformly distributed.

According to this modification, the same effect as in the above embodiment can be obtained. In addition, the bubble 105 can be supplied without using power such as an air source and a bubble generator, and the amount of intake air can be controlled by the valve 121, so that cost reduction and simplification of operation can be achieved.

It is to be noted that the intake pipe 120 in this modified example is further applied to a vertical pump, and as shown in FIG. 10, an intake pipe 122 and a valve 123 whose one end portion penetrates the wall surface of the suction bell mouth 5 may be provided. . This, as above,
When the valve 123 is opened, air is sucked into the pump via the intake pipe 122, and the air bubbles 105 can be generated. However, at this time, when the water level is lower than the height of the impeller 1, the air can be constantly suctioned from the intake pipe 122. However, in the case where the water level is higher than the height of the impeller 1, as shown in FIG.
In the pump operation state, the sum of the water head Hs ′ of the difference between the suction pipe 122 and the water surface and the head loss at the suction portion of the suction bell mouth 5 is larger than the head of the dynamic pressure of the flow at the inlet of the impeller 1. It is necessary to control the water level.

Further, the intake pipe 122 is replaced with an intake pipe provided in a pump of a known preceding standby type pump described in, for example, Japanese Patent No. 2678203 for taking in air into the pump at the time of pumping off operation. You may.

Further, in the above-described embodiment and the modified example, the case where gas particles are supplied into the pumping water by the particle supply means has been described as an example. However, the present invention is not limited to this, and solid particles having significantly different acoustic impedances are supplied. Is also good. Again,
A similar effect is obtained. Further, in the above-described embodiment and the modified example, the case where the flow velocity detecting section (that is, the flow rate detecting section) is located in the flow path in the rainwater drainage pump has been described. However, the present invention is not limited to this. The same effect can be obtained in this case as well. Further, in the above-described embodiment and modified examples, the rainwater drainage pump is described as an example of the hydraulic machine, but the present invention is not limited to this, and a river water pump for pumping river water, and circulating cooling seawater in a thermal power plant or a nuclear power plant. It can be applied to a circulating water pump or the like. At this time, the river water and the cooling seawater are particularly effective because, for example, the mixture of solid and gas impurities is small and their particle concentrations are relatively low. Further, the present invention is not limited to a pump, and can be applied to other hydraulic machines such as a water wheel.

[0039]

According to the present invention, the S / S of the ultrasonic reception signal is
By improving the N ratio, highly accurate flow rate detection can be performed reliably and at low cost regardless of the properties of the liquid to be detected.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration in a case where a flow rate detection device that performs a flow rate detection method according to an embodiment of the present invention is applied to detect a flow rate of a vertical drainage pump for rainwater drainage.

FIG. 2 is a functional block diagram illustrating a function of performing arithmetic processing on a detection result obtained by the ultrasonic current meter.

FIG. 3 is a diagram illustrating the principle when a burst wave transmitted from a transmitter / receiver of an ultrasonic current meter returns after being scattered / reflected.

FIG. 4 is an explanatory diagram for calculating a flow rate.

FIG. 5 is a diagram showing a modification for supplying gas-liquid mixed water.

FIG. 6 is a view showing a modified example utilizing a chemical reaction of a foaming agent.

FIG. 7 is a diagram showing a modification using electrolysis.

FIG. 8 is a cross-sectional view taken along the line DD in FIG. 7 (b).

FIG. 9 is a view showing a modified example applied to an axial flow type pump having a horizontal axis.

FIG. 10 is a view showing a modification in which the structure of FIG. 9 is further applied to a vertical pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Ultrasonic velocimeter 101a Transmitter / receiver 102 Particle supply means 102A-D Particle supply means 102a Air source 102c Air supply pipe 103 Control device 104 Flow rate calculator (arithmetic means) 105 Bubbles (gas particles) 110 Pump (high-pressure liquid source) ) 111 ejector 112 discharge pipe 113 foaming agent 118a-d electrode device 120 intake pipe (communication pipe) 122 intake pipe (communication pipe)

Claims (7)

[Claims] A pulse Doppler ultrasonic flowmeter detects a velocity distribution in a predetermined cross section of a flow path in a hydraulic machine or a flow path located before and after the hydraulic machine, and detects the detected velocity distribution and the predetermined cross section. A flow rate detection method for a hydraulic machine that calculates a flow rate using the cross-sectional area of the flow path, wherein, on the upstream side of the predetermined cross section of the flow path, solid particles or gas particles are supplied into the liquid to be detected by the particle supply unit. Characteristic flow detection method for hydraulic machinery. 2. A flow rate detecting method for a hydraulic machine according to claim 1, wherein said particle supply means supplies bubbles as said gas particles. 3. The method for detecting a flow rate of a hydraulic machine according to claim 1, wherein said particle supply means includes an air source and an air supply pipe connected to the air source. Flow detection method. 4. A method for detecting a flow rate of a hydraulic machine according to claim 1, wherein said particle supply means includes a high-pressure liquid source, and an ejector for sucking air and mixing the air with the high-pressure liquid from the high-pressure liquid source. And a discharge pipe connected to the ejector. 5. A flow rate detecting method for a hydraulic machine according to claim 1, wherein said particle supply means includes a foaming agent for generating a gas by a chemical reaction with water. Method. 6. A method for detecting a flow rate of a hydraulic machine according to claim 1, wherein said particle supply means comprises an electrode for inducing an electrolysis reaction of water. . 7. A method for detecting a flow rate of a hydraulic machine according to claim 1, wherein said particle supply means communicates with said flow path through a wall defining one end of said flow path in said hydraulic machine. A method for detecting a flow rate of a hydraulic machine, comprising a communication pipe which is open to the atmosphere at the other end.