JP7630079B2 - Fluid Mixing Equipment - Google Patents

Description

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

In conventional fluid mixing devices, the ratio of each fluid is controlled by a flow control valve based on the flow 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 for generating evaluation gas during research and development of fuel cell stacks, where moisture is required for the injected gas.

Figure 4 shows the schematic configuration of a conventional fluid mixing device. In Figure 4, the thick lines represent piping. In Figure 4, the fluid mixing device 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 based on the flow rate measurement values and target flow rate values, and mixes them at a junction 408.

Patent No. 4854349

In the conventional configuration described above, the mixing ratio of multiple fluids is controlled based on the flow rate of each fluid. When the mixing ratio is controlled using a flow meter and a fluid control valve, the mixing ratio can be determined based on the flow rates 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 poses the problem of reduced accuracy of the mixing ratio when mixing fluids at low flow rates.

The present invention aims to provide a fluid mixing device that can achieve highly accurate fluid mixing control over a wider range of flow rates than conventional devices by using a first ultrasonic flow meter arranged upstream of a mixing section, a second ultrasonic flow meter 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, and performs mixing control based on conventional flow rate values when the flow rate is high, and switches to mixing control based on a mixing ratio obtained by measuring the mixing ratio based on ultrasonic propagation time when the flow rate is low or the variation in flow rate is large.

The fluid mixing apparatus of the present invention includes a pipe through which fluids flow, a fluid mixing section for mixing a first fluid and a second fluid to produce a mixed fluid, a first ultrasonic flowmeter for measuring a flow rate and a sound speed of the first fluid upstream of the fluid mixing section, a second ultrasonic flowmeter for measuring a flow rate and a sound speed of the mixed fluid downstream of the fluid mixing section, a flow rate type mixing ratio calculation section for calculating 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 for calculating a mixing ratio of the mixed fluid based on the sound speed of the first fluid and the sound speed of the mixed fluid, a mixing operation section disposed in the fluid mixing section and capable of changing the mixing ratio of the first fluid and the second fluid, and The fluid mixing device includes a target value setting unit which sets a target value of the mixing ratio to be changed by the mixing operation unit, 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 setting the difference between the mixing ratio calculated by the flow rate type mixing ratio calculation unit and the target value set by the target value setting unit as the operation amount, or setting the difference between the mixing ratio calculated by the sonic rate type mixing ratio calculation unit and the target value set by 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.

The present invention provides a fluid mixing device that can achieve highly accurate fluid mixing control over a wider range of flow rates than conventional devices by using an ultrasonic flow meter to measure the flow rates and sound speeds before and after fluid mixing and switching the fluid mixing control method based on the flow rates.

FIG. 1 is a configuration diagram of an ultrasonic flow meter according to a first embodiment. FIG. 1 is a configuration diagram of a fluid mixing device according to a first embodiment. A flowchart for explaining the processing of the fluid mixing apparatus in the first embodiment. Schematic diagram of a conventional fluid mixing device

(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.

However, when evaluating in a low-temperature environment, even if the water vapor becomes saturated, the change in moisture content before and after humidification is slight, and if the change in flow rate due to humidification becomes comparable to the variability in flow measurement, the accuracy of humidity control deteriorates. Furthermore, when the total flow rate is low, it generally becomes more difficult for a flow meter to maintain accuracy the lower the flow rate range relative to the full scale, so the accuracy of humidity control deteriorates further. The inventors came up with the subject matter of the present invention in order to solve this problem.

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

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.

(Embodiment 1)
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 3. FIG.

[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 according to 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 parts of each component will be omitted in the description.

In FIG. 1, an upstream ultrasonic sensor 2 and a downstream ultrasonic sensor 3 are arranged in the measurement flow path 1, and a temperature sensor 4 for measuring the temperature of the fluid flowing through the measurement flow path 1 is also arranged in the measurement flow path 1 to form a sensor section. In addition, 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 received signal at 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 time from the downstream ultrasonic sensor 3 to the upstream ultrasonic sensor 4 are calculated 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 the downstream propagation time, which is the time required for ultrasonic waves 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 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 the 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 the flow rate type mixing ratio calculation unit 131, and the sound speed calculated by the sound speed correction unit 18 is sent to the sound speed type mixing ratio calculation unit 132.

Figure 2 is a schematic diagram showing the configuration of a fluid mixing device in the first embodiment of the present invention. The fluid mixing device 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 vaporizing a second fluid in a liquefied state and mixing 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 mixed fluid flows, a first ultrasonic flowmeter 111a arranged in the pipe 102 to measure the flow rate and sound speed of the first fluid, and a second ultrasonic flowmeter 111b arranged in the pipe 104 to measure the flow rate and sound speed of the mixed fluid of the first fluid and the second fluid.

The fluid mixing section 103 is composed of an inlet 103a connected to the pipe 102, an outlet 103b connected to the pipe 104, a pipe 122 connecting the inlet 103a and the outlet 103b, a pipe 121 through which the first fluid flowing in from the inlet 103a branches at a branching point 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 branching point 122b, a flow control valve 125 arranged between the branching points 122a and 122b of the pipe 122, and a flow control valve 126 arranged on the pipe 124.

Furthermore, the device 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 rate measured by the first ultrasonic flow meter 111a and the second ultrasonic flow meter 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 flow meter 111a and the second ultrasonic flow meter 111b, a target value setting unit 133 that sets a target value for the mixing ratio in the mixing control of the first fluid and the second fluid, and a mixing control unit 134 that drives the flow rate adjustment valves 125 and 126, which are mixing operation units, to control the mixing ratio.

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 is to be 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 it to the flow control valves 125, 126, and a control unit 137 that performs overall control and is composed of a microcomputer or the like.

[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.

First, the control unit 137 determines 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 mixing that is determined separately (S102). If it is not a sampling period (No in process S101), the process ends.

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).

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

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

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). If both are greater (Yes in step S107), the mixing ratio M = Q1/(Q1+Q2) is calculated based on the flow rate values (S108), and the manipulated variable u for driving the valve is calculated from a control function f whose argument is the difference (r-M) 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), the mixing ratio N is calculated based on the known correlation between the sound speed value and the mixing ratio (S110), and the manipulated variable u for driving the valve is calculated from a control function f whose argument is the difference (r-N) between the target value r and the mixing ratio N (S109).

Next, a drive signal is sent to the flow rate control valve 125 and the flow rate control valve 126 based on the operation amount u calculated in process S109 or process S111 (S112).

[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 and measuring the flow rate and sound speed of the first fluid, and a second ultrasonic flowmeter 112b arranged on the pipe 104 and 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 the pipe 102 and through which the first fluid branches off 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 connecting the pipe 122 and the pipe 104, a flow control valve 125 arranged in the pipe 122, and a flow control valve 126 arranged in the pipe 124.

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 range of flow rates.

The above-described embodiment is intended to illustrate the technology of the present invention, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

As described above, the fluid mixing device of the present invention can achieve highly accurate fluid mixing control over a wider flow rate range than conventional devices, so that mixed gases such as hydrogen containing water vapor can be adjusted to the desired mixing ratio and flow rate, allowing appropriate operation control and performance evaluation of fuel cell stacks. In addition, the device can be used as a fluid mixing device for medical and industrial chemical applications that require reliable fluid mixing.

REFERENCE SIGNS LIST 1 Measurement flow path 2 Upstream ultrasonic sensor 3 Downstream ultrasonic sensor 4 Temperature sensor 20 Sensor signal processing unit 111a First ultrasonic flowmeter 111b Second ultrasonic flowmeter 131 Flow-based mixing ratio calculation unit 132 Sonic-speed-based mixing ratio calculation unit 101 Fluid mixing device 102 Pipe 103 Fluid mixing unit 104 Pipe 121 Pipe 122 Pipe 123 Container 124 Pipe 125, 126 Flow rate adjustment valve (mixing operation unit)
134 Mixing control section

Claims (6)

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. 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. 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. The fluid mixing device according to claim 3, characterized in that the flow rate threshold is changed based on the standard deviation of the flow rate measured by the second ultrasonic flow meter within a predetermined time. The fluid mixing device according to any one of claims 1 to 4, characterized in that the mixing operation unit adjusts the flow rate of the first fluid flowing through the first pipe or the second fluid flowing through the second pipe by a flow rate control valve arranged in the pipe. 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.