Fluid mixing device

Abstract

To enable fluid mixing control to be performed with high accuracy in a wide flow rate range.SOLUTION: A fluid mixing device comprises: a first ultrasonic flowmeter 111a and a second ultrasonic flowmeter 111b that measure flow rates and sound speeds before and after mixing first fluid with second fluid; flow rate adjustment valves 125 and 126 that adjust the flow rates of the first fluid and of the second fluid to change a mixing ratio; a flow rate-type mixing ratio calculation part 131 that calculates the mixing ration on the basis of the flow rates; a sound speed-type mixing ratio calculation part 132 that calculates the mixing ratio on the basis of the sound speeds; a target value setting part 133 that sets a target value of the mixing ratio; and a mixing control part 134 that calculates operation amounts of the flow rate adjustment valves 125 and 126 and transmits an operation signal. The device switches whether the operation mounts of the flow rate adjustment valves 125 and 126 are set to a difference between the mixing ratio measured by the flow rate-type mixing ratio calculation part 131 and the target value or are set to a difference between the mixing ratio measured by the sound speed-type mixing ratio calculation part 132 and the target value, on the basis of the flow rates measured by the first ultrasonic flowmeter 111a or the second ultrasonic flowmeter 111b.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a configuration of a fluid mixing device that mixes different fluids by controlling the mixing ratio of the fluids. [Background technology]

[0002] In conventional fluid mixing devices, the ratio of each fluid is controlled by a flow control valve based on the flow rate measurement of each fluid to be mixed (see, for example, Patent Document 1). This type of method is widely used when mixing gases in semiconductor manufacturing processes and when generating mixed gases simulating natural gas from each pure gas. In addition, by using a flow meter that is good at measuring under humid conditions, such as an ultrasonic flow meter, it is also possible to control the humidity and dew point of a humidifier that humidifies gas with moisture, and it is also used in generating evaluation gas during research and development of fuel cell stacks, where moisture is required for the injected gas.

[0003] Fig. 4 shows a schematic configuration of a conventional fluid mixing apparatus. In Fig. 4, thick lines represent piping. In Fig. 4, a fluid mixing apparatus 401 measures the flow rate of a first fluid flowing through a first supply line 404 and the flow rate of a second fluid flowing through a second supply line 405 using flow rate measuring devices 402 and 403, respectively, and controls the flow rates of the first fluid and the second fluid using fluid control valves 406 and 407, respectively, based on the flow rate measurement values ​​and target flow rate values, and mixes the first fluid and the second fluid at a junction 408. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4854349 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional configuration, the mixing ratio of multiple fluids is controlled based on the flow rate of each fluid. When the mixing ratio is controlled by a flow meter and a fluid control valve, the mixing ratio can be determined based on the flow rate of each fluid, which provides excellent responsiveness. However, when the flow rate value is low, the measurement accuracy of the flow meter generally deteriorates, which causes a problem of poor accuracy of the mixing ratio when mixing fluids at low flow rates.

[0006] The present invention aims to provide a fluid mixing device that mixes a plurality of fluids, which uses a first ultrasonic flowmeter arranged upstream of a mixing section, a second ultrasonic flowmeter of the same type arranged downstream of the mixing section, and a flow control valve or spray section that can adjust the fluid mixing ratio, so that when the flow rate is high, mixing control is performed based on conventional flow rate values, and when the flow rate is low or there is large variation in the flow rate, mixing control is switched to mixing control based on a mixing ratio obtained by measuring the mixing ratio based on ultrasonic propagation time. This fluid mixing device is capable of achieving highly accurate fluid mixing control over a wider flow rate range than conventional methods. [Means for solving the problem]

[0007] The fluid mixing apparatus of the present invention includes a pipe through which fluids flow, a fluid mixing section that generates a mixed fluid by mixing a first fluid and a second fluid, a first ultrasonic flowmeter that measures the flow rate and sound speed of the first fluid upstream of the fluid mixing section, a second ultrasonic flowmeter that measures the flow rate and sound speed of the mixed fluid downstream of the fluid mixing section, a flow rate type mixing ratio calculation section that calculates a mixing ratio of the mixed fluid based on the flow rate of the first fluid and the flow rate of the mixed fluid, a sonic speed type mixing ratio calculation section that calculates the mixing ratio of the mixed fluid based on the sonic speed of the first fluid and the sonic speed of the mixed fluid, a mixing operation section that is disposed in the fluid mixing section and is capable of changing the mixing ratio of the first fluid and the second fluid, and a mixing ratio that is changed by the mixing operation section. a target value setting unit which sets a target value for a mixing ratio, and a mixing control unit which calculates an operation amount in the mixing operation unit and sends an operation signal to the mixing operation unit, wherein the mixing control unit switches between using the difference between the mixing ratio calculated in the flow rate type mixing ratio calculation unit and the target value set in the target value setting unit as the operation amount, or using the difference between the mixing ratio calculated in the sonic rate type mixing ratio calculation unit and the target value set in the target value setting unit as the operation amount, based on the flow rate measured by a first ultrasonic flowmeter or the flow rate measured by a second ultrasonic flowmeter. Effect of the Invention

[0008] The present invention provides a fluid mixing device that can achieve highly accurate fluid mixing control over a wider flow rate range than conventional devices by using an ultrasonic flowmeter to measure the flow rate and sound speed before and after fluid mixing and switching the fluid mixing control method based on the flow rate. [Brief description of the drawings]

[0009] [Figure 1] A configuration diagram of an ultrasonic flowmeter according to the first embodiment. [Diagram 2] FIG. 1 is a configuration diagram of a fluid mixing device according to a first embodiment. [Diagram 3] 1 is a flowchart illustrating the process of the fluid mixing apparatus according to the first embodiment. [Figure 4] Schematic diagram of a conventional fluid mixing device DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Foundations and other information that form the basis of the present invention) For a fuel cell to operate efficiently, it is necessary to maintain high humidity inside the stack and increase the conductivity of hydrogen ions. During fuel cell research and development, a humidified gas with a predetermined humidity level is sometimes injected into the stack to evaluate its performance in order to investigate the correlation between humidity and stack performance. To generate this humidified gas with the desired humidity level, a method is used in which the gas flow rate before and after humidification is measured using an ultrasonic flowmeter or similar device, the moisture content is calculated from the ratio, and the mixture rate is controlled by a flow control valve.

[0011] However, when evaluating in a low-temperature environment, even if the water vapor is saturated, the change in moisture content before and after humidification is small, and if the change in the flow rate of the humidified air becomes comparable to the variation in the flow rate measurement, the accuracy of the humidity control deteriorates. Furthermore, when the total flow rate is low, it is generally more difficult for a flow meter to maintain accuracy the lower the flow rate range is compared to the full scale, so the humidity control accuracy deteriorates further. In order to solve this problem, the inventors have come to form the subject of the present invention.

[0012] Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or duplicate description of substantially the same configuration may be omitted.

[0013] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present invention, and are not intended to limit the subject matter described in the claims.

[0014] (Embodiment 1) Hereinafter, the first embodiment will be described with reference to FIGS.

[0015] [1-1. Configuration] 1 is a block diagram and a cross-sectional view showing the configuration of the first ultrasonic flowmeter 111a or the second ultrasonic flowmeter 111b in the first embodiment of the present invention. Since the configuration and operation are the same for the first ultrasonic flowmeter 111a and the second ultrasonic flowmeter 111b, the first and second of each component will be omitted in the description.

[0016] 1, an upstream ultrasonic sensor 2 and a downstream ultrasonic sensor 3 are disposed in the measurement flow path 1, and further, a temperature sensor 4 for measuring the temperature of the fluid flowing through the measurement flow path 1 is disposed in the measurement flow path 1 to form a sensor section. Also, there are a measurement control section 11 that controls ultrasonic measurement using the upstream ultrasonic sensor 2 and the downstream ultrasonic sensor 3, a transmission section 12 that transmits a drive signal for driving the ultrasonic sensor, a switching section 13 that alternately switches the destination of the drive signal and the signal received by the ultrasonic sensor, a reception section 14 that receives the received signal, and an upstream propagation time that is the time required for ultrasonic waves to propagate from the upstream ultrasonic sensor 2 to the downstream ultrasonic sensor 3 and a downstream ultrasonic sensor 3 to the upstream ultrasonic sensor 4 based on a counter value from when the measurement control section 11 issues a drive signal to when the reception signal is received by the reception section 14. The sensor signal processing unit 20 is made up of a propagation time measuring unit 15 that measures a downstream propagation time, which is the time required for an ultrasonic wave to propagate to the ultrasonic sensor 2, a flow rate calculation unit 16 that measures the flow rate of the fluid flowing through the measurement flow path 1 by a known propagation time difference method or a propagation time reciprocal difference method based on the obtained upstream propagation time and downstream propagation time, a sound speed calculation unit 17 that calculates the sound speed of the fluid flowing through the measurement flow path 1 based on an average value of the obtained upstream propagation time and downstream propagation time, and a sound speed correction unit 18 that standardizes the sound speed to the sound speed at a predetermined temperature based on the temperature obtained by the temperature sensor 4. The flow rate calculated by the flow rate calculation unit 16 is sent to a flow rate-based mixing ratio calculation unit 131, and the sound speed calculated by the sound speed correction unit 18 is sent to a sound speed-based mixing ratio calculation unit 132.

[0017] FIG. 2 is a schematic diagram showing the configuration of a fluid mixing apparatus in a first embodiment of the present invention. The fluid mixing apparatus 101 includes a pipe 102 (first pipe) through which a first fluid (gas) flows, a fluid mixing unit 103 connected to the pipe 102 and configured to vaporize a second fluid in a liquefied state and mix it with the first fluid to generate a mixed fluid (gas), a pipe 104 (second pipe) connected to the fluid mixing unit 103 and through which the mixed fluid flows, a first ultrasonic flowmeter 111a disposed in the pipe 102 for measuring the flow rate and speed of sound of the first fluid, and a second ultrasonic flowmeter 111b disposed in the pipe 104 for measuring the flow rate and speed of sound of the mixed fluid of the first fluid and the second fluid.

[0018] The fluid mixing section 103 is composed of an inlet section 103a connected to the pipe 102, an outlet section 103b connected to the pipe 104, a pipe 122 connecting the inlet section 103a and the outlet section 103b, a pipe 121 through which the first fluid flowing in from the inlet section 103a branches at a branch section 122a and flows, a container 123 connected to the pipe 121 and containing a liquefied second fluid 7, a pipe 124 connected to the container 123 and further connected to the pipe 122 at a branch section 122b, a flow control valve 125 arranged between the branch sections 122a and 122b of the pipe 122, and a flow control valve 126 arranged in the pipe 124.

[0019] Furthermore, the system includes a flow rate type mixing ratio calculation unit 131 that calculates the mixing ratio of the first fluid and the second fluid based on the flow rates measured by the first ultrasonic flowmeter 111a and the second ultrasonic flowmeter 111b, a sonic speed type mixing ratio calculation unit 132 that calculates the mixing ratio of the first fluid in the mixed fluid based on the sound speed measured by the first ultrasonic flowmeter 111a and the second ultrasonic flowmeter 111b, a target value setting unit 133 that sets a target value of the mixing ratio in the mixing control of the first fluid and the second fluid, and a mixing control unit 134 that drives flow rate adjustment valves 125 and 126, which are mixing operation units, to control the mixing ratio.

[0020] The mixing control unit 134 here is composed of an output value selection unit 135 that selects whether the mixing ratio or the mixing ratio should be used as the output value based on the flow rate measured by the second ultrasonic flowmeter 111b, an operation signal calculation unit 136 that calculates the operation amount for driving the flow control valves 125, 126 based on the difference between the target value set by the target value setting unit 133 and the output value selected by the output value selection unit 135, and transmits the operation amount to the flow control valves 125, 126, and a control unit 137 composed of a microcomputer or the like that performs overall control.

[0021] [1-2. Operation] Next, the operation of the fluid mixing system in this embodiment will be described with reference to the flowchart shown in FIG.

[0022] First, the control unit 137 judges whether or not it is a sampling period, which is an execution interval of the mixing control (S101), and if it is a sampling period (Yes in process S101), it sets a target value r, which is a target mixing ratio of the fluid mixture that is determined separately (S102). If it is not a sampling period (No in process S101), the process ends.

[0023] Next, in the first ultrasonic flowmeter 111a, the flow rate Q1 calculated by the flow rate calculation unit 16 based on the upstream propagation time and downstream propagation time measured by the propagation time measurement unit 15 and the temperature measured by the temperature sensor 4, and the sound speed C1 calculated by the sound speed correction unit 18 are stored in chronological order (S103). Similarly, in the second ultrasonic flowmeter 111b, the flow rate Q2 and sound speed C2 are stored in chronological order (S104).

[0024] Next, from the flow rates Q1 and Q2 stored in chronological order, the standard deviation Sq1 of the flow rate Q1 within a predetermined time period and the standard deviation Sq2 of the flow rate Q2-Q1 are calculated and stored (S105).

[0025] Next, standard deviations Sq1 and Sq2 are added to a preset flow rate threshold value α, respectively, to calculate flow rate threshold values ​​α1 and α2 that take into account the measurement variability, and these are stored (S106).

[0026] Next, it is determined whether the flow rate Q1 and the flow rate Q2-Q1 are greater than the flow rate thresholds α1 and α2 (S107), and if both are greater (Yes in step S107), a mixing ratio M=Q1 / (Q1+Q2) based on the flow rate value is calculated (S108), and an operation amount u for driving the valve is calculated from a control function f with an argument being the difference (rM) between the target value r and the mixing ratio M (S109). If either or both of the flow rate Q1 and the flow rate Q2-Q1 are less than or equal to the flow rate thresholds α1 and α2 (No in S107), a mixing ratio N is calculated based on a known correlation between the sound speed value and the mixing ratio (S110), and an operation amount u for driving the valve is calculated from a control function f with an argument being the difference (rN) between the target value r and the mixing ratio N (S109).

[0027] Next, a drive signal is transmitted to the flow rate adjustment valve 125 and the flow rate adjustment valve 126 based on the manipulated variable u calculated in step S109 or step S111 (S112).

[0028] [1-3. Effects, etc.] As described above, in this embodiment, the fluid mixing apparatus 101 includes a pipe 102 (first pipe) through which a first fluid flows, a fluid mixing section 103 connected to the pipe 102 and in which the first fluid and the second fluid mix to form a mixed fluid, a pipe 104 (second pipe) connected to the fluid mixing section 103 and through which the mixed fluid flows, a first ultrasonic flowmeter 111a arranged on the pipe 102 for measuring the flow rate and sound speed of the first fluid, and a second ultrasonic flowmeter 111b arranged on the pipe 104 for measuring the mixed flow of the first fluid and the second fluid. and a second ultrasonic flowmeter 111b that measures the flow rate and speed of sound of the fluid. The fluid mixing section 103 here comprises two pipes 121, 122 connected to pipe 102 and through which the first fluid branches off and flows, a container 123 connected to pipe 121 and containing liquefied second fluid 7, a pipe 124 connected to container 123 and further connecting pipe 122 and pipe 104, a flow control valve 125 arranged in pipe 122, and a flow control valve 126 arranged in pipe 124.

[0029] As a result, the mixing control unit 134 can perform highly responsive fluid mixing based on the flow rate ratio when the fluid flow rate is sufficient, and switch to fluid mixing based on the speed of sound when the fluid flow rate is low, thereby enabling highly accurate fluid mixing over a wide flow rate range.

[0030] It should be noted that the above-described embodiment is intended to illustrate the technology of the present invention, and various modifications, substitutions, additions, omissions, and the like can be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0031] As described above, the fluid mixing device according to the present invention can realize highly accurate fluid mixing control over a wider flow rate range than conventional devices, and can adjust mixed gases such as hydrogen containing water vapor to the desired mixing ratio and flow rate, thereby enabling appropriate operation control and performance evaluation of fuel cell stacks. In addition, the fluid mixing device can be used in medical and industrial chemical applications where reliability in fluid mixing is required. [Explanation of symbols]

[0032] 1 Measurement flow path 2. Upstream ultrasonic sensor 3. Downstream ultrasonic sensor 4 Temperature Sensor 20 Sensor signal processing section 111a 1st ultrasonic flowmeter 111b 2nd ultrasonic flowmeter 131 Flow rate type mixing ratio calculation section 132 Sonic mixing ratio calculation unit 101 Fluid mixing device 102 Piping 103 Fluid mixing section 104 Piping 121 Piping 122 Piping 123 Container 124 Piping 125, 126 Flow control valve (mixing operation part) 134 Mixing control section

Claims

1. a fluid mixing section that mixes the first fluid and the second fluid to generate a mixed fluid; a first pipe that supplies a first fluid to the fluid mixing section; a second pipe for supplying the mixed fluid generated in the fluid mixing section; a first ultrasonic flowmeter disposed in the first pipe and configured to measure a flow rate and a sound speed of the first fluid; a second ultrasonic flowmeter disposed in the second pipe for measuring a flow rate and a sound speed of the mixed fluid; a flow rate-based mixing ratio calculation unit that calculates a mixing ratio of the mixed fluid based on a flow rate of the first fluid and a flow rate of the mixed fluid; a sonic mixing ratio calculation unit that calculates a mixing ratio of the mixed fluid based on the sonic speed of the first fluid and the sonic speed of the mixed fluid; a mixing operation unit disposed in the fluid mixing unit and capable of changing a mixing ratio of the first fluid and the second fluid; a target value setting unit that sets a target value of the mixing ratio to be changed by the mixing operation unit; a mixing control unit that calculates an operation amount in the mixing operation unit and sends an operation signal to the mixing operation unit; A fluid mixing apparatus comprising: The fluid mixing device according to claim 1, wherein the mixing control unit calculates the manipulated variable based on a difference between the mixing ratio measured by the flow rate type mixing ratio calculation unit and a target value set by the target value setting unit, or calculates the manipulated variable based on a difference between the mixing ratio measured by the sonic rate type mixing ratio calculation unit and a target value set by the target value setting unit, based on a flow rate measured by the first ultrasonic flowmeter or a flow rate measured by the second ultrasonic flowmeter.

2. The first ultrasonic flow meter and the second ultrasonic flow meter each have a measurement flow path through which a fluid flows; an upstream ultrasonic sensor disposed upstream of the measurement flow path; a downstream ultrasonic sensor disposed downstream of the measurement flow path; a propagation time measuring unit that measures an upstream propagation time, which is the time required for an ultrasonic wave emitted by the upstream ultrasonic sensor to be received by the downstream ultrasonic sensor, and a downstream propagation time, which is the time required for an ultrasonic wave emitted by the downstream ultrasonic sensor to be received by the upstream ultrasonic sensor; a flow rate calculation unit that calculates a flow rate based on the upstream propagation time and the downstream propagation time; 2. The fluid mixing apparatus according to claim 1, further comprising a sound speed calculation unit that calculates a sound speed based on an average value of the upstream propagation time and the downstream propagation time.

3. When the flow rate measured by the second ultrasonic flowmeter is greater than a predetermined flow rate threshold, the mixing control unit calculates the manipulated variable based on the difference between the mixing ratio measured by the flow rate type mixing ratio calculation unit and the target value set by the target value setting unit, 3. The fluid mixing device according to claim 1, wherein when the flow rate measured by the second ultrasonic flowmeter is equal to or lower than a predetermined flow rate threshold, the manipulated variable is calculated based on a difference between the mixing ratio measured by the sonic mixing ratio calculation unit and the target value set by the target value setting unit.

4. 4. The fluid mixing apparatus according to claim 3, wherein the flow rate threshold is changed based on a standard deviation of the flow rate measured within a predetermined time by the second ultrasonic flow meter.

5. 5. The fluid mixing apparatus according to claim 1, wherein the mixing operation unit adjusts a flow rate of the first fluid flowing through the first pipe or the second fluid flowing through the second pipe by a flow control valve arranged in the pipe.

6. the first fluid is a gas; the second fluid is a liquid; 6. The fluid mixing apparatus according to claim 5, wherein the fluid mixing section includes a container containing the second fluid, and vaporizes the second fluid to be mixed with the first fluid.

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