JP4224783B2 - Fuel concentration measuring device and fuel concentration measuring method - Google Patents

Description

  The present invention relates to a fuel concentration measuring device and a fuel concentration measuring method, and more particularly to a fuel concentration measuring device and a fuel concentration measuring method supplied to a direct methanol type fuel cell using methanol as a fuel for power generation.

  A fuel cell is a power generation element that generates power by electrochemically reacting fuel and oxygen (oxidant gas). In recent years, fuel cells have attracted attention as power generation elements that do not pollute the environment because the product generated by power generation is mainly water. For example, fuel cells are used as drive power sources for driving automobiles and household cogeneration systems. Attempts to use have been made.

  Furthermore, the development of fuel cells as drive power sources for portable electronic devices such as notebook personal computers, mobile phones, and PDAs (Personal Digital Assistants) has been actively conducted, not limited to the above-described drive power sources for driving automobiles. Yes. In such a fuel cell, it is important that the required power can be stably output and the size and weight are portable, and various technologies have been actively developed to meet such demands. Yes.

The fuel cell is classified into various types depending on the difference in electrolyte, the fuel supply method, and the like. A direct methanol fuel cell that directly uses methanol as fuel without reforming methanol into hydrogen (Direct Methanol Fuel Cell) DMFC) has also been proposed. In a direct methanol type fuel cell, a reaction such as CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ occurs on the anode side, and a reaction such as 3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O occurs mainly on the cathode side. It is happening. Protons (H ⁺ ) generated on the anode side are transferred to the cathode side by the electrolyte, and a reaction of CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O occurs as a whole, and water and carbon dioxide are generated along with power generation.

  In a direct methanol type fuel cell, a power generation reaction at the anode does not proceed only by supplying pure methanol as a fuel. Therefore, it is necessary to supply a fuel in which water and methanol are mixed to the anode. As a fuel supply method at this time, a method of previously mixing methanol and water with an appropriate composition has been proposed. In addition, a fuel flow path that circulates fuel is installed, and pure methanol is replenished to replenish the methanol component that has been consumed and shortaged by the power generation reaction, and water generated at the cathode by the power generation reaction is recovered and mixed with the fuel. A method has been proposed.

  In the case where methanol and water are mixed in advance as fuel, the fuel cell system need not be provided with a mechanism for mixing methanol and water, so that the structure of the fuel cell system can be simplified. However, since the supplied methanol is previously mixed with moisture, the energy density of the supplied fuel itself is lowered. When a fuel with a high methanol concentration is used to increase the energy density of the fuel, the methanol crosses over the ion exchange membrane that conducts protons, not only lowering the power generation efficiency of the fuel cell, but also the MEA (Membrane) that is the power generator. and Electrode Assembly) are likely to deteriorate, and the life of the fuel cell is shortened.

  In addition, it is necessary to mix pure methanol and water in the production process before supplying the fuel cell to the fuel. When storing the fuel in a mixed state, the methanol concentration is stabilized over a long period of time. May cause problems. On the other hand, when water generated by power generation is recovered and reused for fuel mixing, it is necessary to install a sensor for measuring the methanol concentration in order to keep the methanol concentration in the fuel constant. As a fuel concentration measuring apparatus for measuring the concentration of methanol, an apparatus that measures the concentration of fuel by measuring the velocity of ultrasonic waves in the fuel with an ultrasonic transmitter and an ultrasonic receiver has been proposed (patent) Reference 1).

JP-A-11-23541

The measurement of the fuel concentration using ultrasonic waves enables precise concentration measurement. As shown in the graph of FIG. 6, the relationship between the fuel concentration and the sound speed is shown above when the fuel concentration is plotted on the horizontal axis and the sound speed is plotted on the vertical axis. Draw a convex curve. Therefore, even if the sound velocity of the ultrasonic wave is measured, the fuel concentration corresponding to the measured sound velocity v can be considered as binary values of d ₁ and d ₂ , and it is judged which of the binary values is the correct fuel concentration. It was difficult.

Accordingly, an object of the present invention is to provide a fuel concentration measuring apparatus and a fuel concentration measuring method capable of accurately and quickly measuring the alcohol concentration in the fuel.

Fuel concentration measuring apparatus of the present invention to solve the aforementioned problems is a fuel concentration measuring device for measuring the alcohol concentration in the fuel, and the sound speed measuring unit for measuring the sound velocity of a sound wave propagating said fuel, wherein A dielectric constant measurement unit that measures the dielectric constant of fuel, an information processing unit that calculates the alcohol concentration in the fuel based on the sound velocity measured by the sound velocity measurement unit, and the dielectric constant measured by the dielectric constant measurement unit The sound velocity measurement unit measures the sound velocity of the sound wave, calculates alcohol concentrations d ₁ and d ₂ from the measured sound velocity and a curve indicating the relationship between the sound velocity and the alcohol concentration, and calculates the calculated d ₁ and d Of the _two, the one close to the alcohol concentration in the fuel corresponding to the dielectric constant measured by the dielectric constant measuring unit is set as the accurate alcohol concentration in the fuel .

By measuring the sound velocity of the sound wave propagating in the fuel and the dielectric constant of the fuel , the alcohol concentration in the fuel that can have a precise but binary calculation result that can be obtained from the relationship between the sound velocity and the alcohol concentration, By comparing the alcohol concentration in the fuel of a single calculation result obtained from the relationship between the dielectric constant and the fuel concentration, it is possible to obtain a precise and single alcohol concentration as the calculation result. Therefore, the alcohol concentration in the fuel can be measured accurately and quickly.

  The sound velocity measurement unit includes a transmission unit that transmits ultrasonic waves of a predetermined frequency and a reception unit that receives ultrasonic waves. The ultrasonic wave emitted by the transmission unit is propagated through the fuel, and the reception unit receives the ultrasonic waves. By doing so, the speed of sound in the fuel may be measured. By measuring the speed of sound waves propagating in the fuel by receiving and transmitting ultrasonic waves, it is possible to accurately measure sound waves. The dielectric constant measuring unit may have an electrode pair in which two electrodes are opposed to each other, and measure the electric capacity by inserting fuel between the electrodes of the electrode pair to measure the dielectric constant of the fuel. It is easy to measure the electric capacity by sandwiching the fuel between the electrode pair, so that it is easy to measure the dielectric constant of the fuel.

In addition, a fuel flow path that is filled with fuel and a degassing flow path branched from the fuel flow path are provided, and a position downstream of the fuel flow from the position where the degassing flow path of the fuel flow path branches. In addition, a sound speed measuring unit may be arranged. There is a possibility that gas such as carbon dioxide is mixed in the fuel, and when measuring the sound velocity of sound waves propagating in the fuel, if the gas stays in the fuel, the accurate sound velocity is measured. It becomes difficult. By branching the degassing channel from the fuel channel and measuring the sonic velocity downstream of the branching position with the degassing channel, the decrease in measurement accuracy due to the influence of gas is eliminated and the accurate sonic velocity is reduced. Measurement can be performed. If an accurate sound speed can be measured, the information processing unit can calculate an accurate alcohol concentration in the fuel.

In order to solve the above problems, a fuel concentration measuring method of the present invention is a fuel concentration measuring method for measuring an alcohol concentration in a fuel, wherein a sound velocity of a sound wave propagating through the fuel and a dielectric constant of the fuel are calculated. A step of measuring, a step of calculating alcohol concentrations d ₁ and d ₂ from the measured sound speed and a curve indicating a relationship between the sound speed and the alcohol concentration, and the measurement of the calculated alcohol concentrations d ₁ and d ₂ And the step of making the alcohol concentration in the fuel closer to the alcohol concentration in the fuel corresponding to the measured dielectric constant.

By measuring the sound velocity of the sound wave propagating in the fuel and the dielectric constant of the fuel , the alcohol concentration in the fuel that can have a precise but binary calculation result that can be obtained from the relationship between the sound velocity and the alcohol concentration, By comparing the alcohol concentration of a single calculation result obtained from the relationship between the dielectric constant and the fuel concentration, it is possible to obtain an accurate alcohol concentration in the single fuel as the calculation result. Therefore, the alcohol concentration in the fuel can be measured accurately and quickly.

  By measuring the propagation speed of the ultrasonic wave propagating through the fuel, the sound velocity is measured, and by measuring the sound velocity of the sound wave propagating through the fuel by receiving and transmitting the ultrasonic wave, it is possible to accurately measure the sound wave. In addition, it is easy to measure the dielectric constant of the fuel by sandwiching the fuel between the electrode pair in which the two electrodes are opposed and measuring the dielectric constant by measuring the electric capacity between the electrodes.

There is a possibility that gas such as carbon dioxide is mixed in the fuel, and when measuring the sound velocity of sound waves propagating in the fuel, if the gas stays in the fuel, the accurate sound velocity is measured. It becomes difficult. By separating the gas mixed in the fuel from the fuel and measuring the sound velocity after separating the gas, it is possible to eliminate the decrease in measurement accuracy due to the influence of the gas and perform accurate sound velocity measurement Become. If an accurate sound speed can be measured, the information processing unit can calculate an accurate alcohol concentration in the fuel.

By measuring the sound velocity of the sound wave propagating in the fuel and the dielectric constant of the fuel , the alcohol concentration in the fuel that can have a precise but binary calculation result that can be obtained from the relationship between the sound velocity and the alcohol concentration, By comparing the alcohol concentration in the fuel of a single calculation result obtained from the relationship between the dielectric constant and the fuel concentration, it is possible to obtain a precise and single alcohol concentration as the calculation result. Therefore, the alcohol concentration in the fuel can be measured accurately and quickly.

  Hereinafter, a fuel concentration measuring apparatus and a fuel concentration measuring method to which the present invention is applied will be described in detail with reference to the drawings. The present invention is not limited to the following description, and can be appropriately changed without departing from the gist of the present invention. Note that although an example in which an aqueous solution in which methanol and water are mixed is used as the fuel in this embodiment, an aqueous solution in which other fuel and water are mixed may be used.

  FIG. 1 is an external perspective view showing a configuration example of a fuel concentration measuring device of the present invention, and FIG. 2 is a cross-sectional perspective view showing a cross section of the fuel concentration measuring device in a plane direction indicated by an arrow A in FIG. 3 is a cross-sectional view showing a cross section of the fuel concentration measuring device in the plane direction indicated by arrow A in FIG. The fuel concentration measuring device includes a casing 1 that forms the outer shape of the entire device, an ultrasonic unit 2 that transmits and receives ultrasonic waves of a predetermined wavelength, and a sound wave reflecting unit 3 that is a surface that reflects ultrasonic waves. And an information processing unit 4 that processes and transmits information, a temperature sensor 5 that measures the temperature of the fuel, and a dielectric constant measurement unit 6 that measures the dielectric constant of the fuel. An opening 7 is formed on one surface of the housing 1 so that a methanol aqueous solution obtained by mixing methanol and water as fuel passes through the inside of the housing 1. Although not shown in FIG. 1, it is assumed that the opening 7 is similarly opened on the surface facing the surface of the housing 1 where the opening 7 is opened.

  In addition, a fuel flow path 8 through which fuel passes is formed inside the casing 1, and the fuel that has flowed into the casing 1 from one opening 7 passes through the fuel flow path 8 and the other opening. It is configured to flow out from the part 7. The ultrasonic unit 2, the sound wave reflection unit 3, the temperature sensor 5, and the dielectric constant measurement unit 6 are arranged so as to be exposed to the fuel flow path 8, and each part comes into contact with the fuel passing through the fuel flow path 8. ing.

  As shown in FIG. 2, the ultrasonic unit 2 is divided into a transmission unit 2 a that transmits predetermined ultrasonic waves and a reception unit 2 b that receives ultrasonic waves. The transmission unit 2 a and the reception unit 2 b include the fuel flow path 8. Are arranged in parallel on the same side. The sound wave reflecting unit 3 is a member that receives the ultrasonic wave transmitted from the transmitting unit 2a on the wall surface and reflects the ultrasonic wave toward the receiving unit 2b side. The transmitting portion 2a and the receiving portion 2b are each formed with a wall surface so as to be inclined with respect to the fuel flow path 8, and as shown in FIG. 3, the ultrasonic waves transmitted perpendicularly to the transmitting portion 2a wall surface are sound waves. The light is reflected by the reflector 3 and enters the wall surface of the receiver 2b perpendicularly. In the ultrasonic unit 2, the ultrasonic wave transmitted from the transmitting unit 2 a propagates the fuel passing through the fuel flow path 8 and reaches the sound wave reflecting unit 3, and the ultrasonic wave reflected by the sound wave reflecting unit 3 propagates the fuel. Then, the speed of the ultrasonic wave in the fuel is measured by measuring the time until it reaches the receiver 2b. Therefore, it is necessary to accurately set the length of the path through which the ultrasonic wave propagates.

  FIG. 2 shows an example in which the sound wave reflection unit 3 is disposed on the side surface opposite to the side surface of the fuel flow path 8 in which the transmission unit 2a and the reception unit 2b are disposed. However, the ultrasonic wave transmitted from the transmitting unit 2a propagates through the fuel passing through the fuel flow path 8 and reaches the sound wave reflecting unit 3, and the ultrasonic wave reflected by the sound wave reflecting unit 3 propagates through the fuel and receives the receiving unit 2b. The relative positional relationship between the transmitting unit 2a, the receiving unit 2b, and the sound wave reflecting unit 3 may be any as long as the configuration reaches. In addition, the transmitter 2a and the receiver 2b are arranged so as to sandwich the fuel flow path 8 without providing the sound wave reflection section 3, and the ultrasonic wave transmitted from the transmitter 2a passes through the fuel flow path 8 to the fuel. It is good also as a structure which propagates and reaches | attains the receiving part 2b directly.

The information processing unit 4 is an arithmetic device connected to the ultrasonic unit 2, the sound wave reflection unit 3, the temperature sensor 5, and the dielectric constant measurement unit 6 so as to be able to transmit information. The information processing unit 4 is based on the sound velocity of the ultrasonic wave propagating through the fuel measured by the ultrasonic unit 2, the temperature of the fuel measured by the temperature sensor 5, and the dielectric constant of the fuel measured by the dielectric constant measuring unit 6. To calculate the concentration of alcohol in the fuel. A method for calculating the alcohol concentration in the fuel will be described later.

  The temperature sensor 5 is a thermometer that measures the temperature of the fuel flowing through the fuel flow path 8, and an existing thermometer such as a thermocouple can be used. Since the fuel used in the fuel cell is a mixed solution of alcohol and water, the temperature sensor 5 needs to be able to accurately measure the temperature in the temperature region where both alcohol and water are in a liquid state.

  The dielectric constant measuring unit 6 includes, for example, two flat electrodes having the same area facing each other in the fuel, and the fuel flowing between the electrodes and the electrodes constitute a parallel plate capacitor. As shown in FIG. 2, electrode pairs may be formed on opposite side surfaces of the fuel flow path 8. The electric capacity of the parallel plate capacitor depends on the distance between the electrodes, the electrode area, and the dielectric constant of the substance existing between the electrodes. Therefore, the distance between the electrodes and the electrode area are measured in advance, and a voltage is applied between the electrodes. By measuring the electric capacity of the capacitor, the dielectric constant of the fuel existing between the electrodes can be measured.

Next, a method for calculating the alcohol concentration in the fuel in the information processing unit 4 will be described with reference to FIG. Figure 4 is the relationship between the ultrasonic speed of sound propagating through the alcohol concentration in the fuel in the fuel, and is a graph showing the relationship between alcohol concentration and the fuel dielectric constant in the fuel. The horizontal axis indicates the alcohol concentration in the fuel, the left vertical axis indicates the speed of sound of ultrasonic waves transmitted through the fuel, and the right vertical axis indicates the dielectric constant of the fuel. In addition, the upwardly convex curve in the graph is a graph showing the relationship between the alcohol concentration in the fuel and the speed of sound, and the straight line drawn in the graph is a graph showing the relationship between the alcohol concentration in the fuel and the dielectric constant. It is.

In the concentration measuring apparatus and concentration measuring method of the present invention, the ultrasonic velocity 2 of the ultrasonic wave in the fuel passing through the fuel flow path 8 is measured by the ultrasonic unit 2 and the sound wave reflecting portion 3, and the fuel flow path 8 is measured by the temperature sensor 5. The temperature T1 of the fuel passing through the fuel is measured, the dielectric constant k1 of the fuel passing through the fuel flow path 8 is measured by the dielectric constant measuring unit 6, and information on the sound velocity v1, the temperature T1, and the dielectric constant k1 measured in each part is obtained. The information is transmitted to the information processing unit 4. The information processing unit 4, are recorded in advance in the storage device alcohol concentration and sonic, and relationships of the alcohol concentration and the dielectric constant in the fuel in the fuel as shown in FIG. 4, the sound velocity measured at each measurement unit v1 Based on the temperature T1 and the dielectric constant k1, the alcohol concentration in the fuel is calculated. When the relationship between the alcohol concentration and the sound speed in the fuel and the relationship between the alcohol concentration in the fuel and the dielectric constant depends on the temperature T1, the alcohol concentration in the fuel may be corrected based on the temperature T1.

When the measurement results dielectric constant of k1 is found to be the alcohol concentration in the fuel from the straight line indicating the relationship between the alcohol concentration of the dielectric constant and the fuel it is close to d4. However, as shown in FIG. 4, the relationship between the dielectric constant and the alcohol concentration in the fuel is a straight line with a gentle slope, and the calculation range of the alcohol concentration in the fuel is expanded depending on the measurement error range of the dielectric constant. . In addition, when detecting the dielectric constant, the electrode is formed of a conductor, so measurement is impossible if an ionic impurity is present in the object to be measured, and when an insulating film is formed on this electrode, the dielectric constant of the insulating film is reduced. It becomes dominant, and the rate of change due to the concentration of capacitance decreases, making it difficult to accurately detect the concentration. Therefore, even if the dielectric constant k1 is obtained by measurement and the alcohol concentration in the fuel is calculated only from the value of the dielectric constant k1, the reliability of the calculated alcohol concentration in the fuel is lowered.

The measurement if the result is a sound velocity is v1 is from curves showing the relationship between the alcohol concentration of the sound velocity and the fuel it can be seen that the alcohol concentration in the fuel is d3 or d4. However, the alcohol concentration in the fuel corresponding to the measured sound velocity v1 is considered to be binary of d3 and d4, and it is difficult to determine which of the binary concentrations is the accurate alcohol concentration in the fuel. .

Therefore, both measured acoustic velocity v1 and the dielectric constant k1, to calculate the alcohol concentration in the fuel corresponding to the speed of sound v1 and dielectric constant k1 in relation to the alcohol concentration of the sound velocity and the dielectric constant and the fuel as shown in FIG. 4 Thus, since the concentration is d3 or d4 and is close to d4, it is finally found that the alcohol concentration in the fuel is d4. From the alcohol concentration and the sound speed of the relationship between the fuel it can be to calculate the alcohol concentration precise fuel rapidly to perform the calculation of the concentration of alcohol in the fuel from the relationship between the alcohol concentration and the dielectric constant of the fuel Therefore, it is possible to accurately and quickly calculate the alcohol concentration in the fuel by measuring both the speed of sound and the dielectric constant.

  FIG. 5 is a cross-sectional perspective view showing a cross-sectional view of the fuel concentration measuring device in the plane direction indicated by arrow B in FIG. 1, and the vertical direction in the figure corresponds to the direction of gravity. Inside the housing 1, as shown in FIG. 2, the sound wave reflection unit 3 and the dielectric constant measurement unit 6 are disposed around the fuel flow path 8, and the information processing unit 4 is disposed below the housing 1. . A degassing channel 9 is formed in the upper part of the housing 1 in parallel with the fuel channel 8, and the fuel channel 8 and the degassing channel 9 are separated by a partition wall 10. Further, in the vicinity of the connection portion between the opening 7 formed in the housing 1 and the fuel flow path 8, the fuel flow path 8 and the degassing flow path 9 are connected by a communication flow path 11. A vent hole 12, which is a hole penetrating the housing 1, is formed in the upper part of the degassing flow path 9, and gas can flow in and out between the outside of the fuel concentration measuring device and the degassing flow path 9. ing. Thereby, the opening 7, the fuel flow path 8, the degassing flow path 9, and the communication flow path 11 communicate with each other and fluid can pass therethrough.

  When the fuel flows into the fuel concentration measuring device of the present invention, the fuel that flows in from one opening 7 passes through the fuel flow path 8 and flows out from the other opening 7. At this time, the fuel passing through the fuel flow path 8 is filled up to the middle position of the communication flow path 11, and the flow rate of the fuel is adjusted so that the inside of the degassing flow path 9 is not completely filled with fuel. Therefore, fuel fills and passes through the fuel flow path 8, but gas exists in the degassing flow path 9.

  There is a possibility that the fuel that is the measurement target for measuring the alcohol concentration by the fuel concentration measuring device is mixed with gas such as carbon dioxide and carbon monoxide generated by power generation in the fuel cell. When gas is mixed in the fuel, in ultrasonic measurement, the reflection of the ultrasonic wave is reduced by bubbles staying at the measurement site, and accurate concentration detection becomes difficult. However, as described above, the fuel is filled in the fuel flow path 8, but the degassing flow path 9 is not filled with fuel, so that it is mixed in the fuel passing through the fuel flow path 8. The gas that is flowing is separated into the degassing flow path 9 through the communication flow path 11. Since the outside of the fuel concentration measuring device and the degassing channel 9 can flow in and out of the gas via the vent hole 12, the gas separated in the degassing channel 9 is outside the fuel concentration measuring device. Will be released.

  Therefore, by forming a fluid flow path branched from the fuel flow path 8 and connected to the outside inside the fuel concentration measuring device, the gas mixed in the fuel is efficiently separated and released to the outside. In the fuel flow path 8 on the downstream side of the connection flow path 11 with respect to the fuel flow, the amount of gas mixed in the fuel can be reduced, and the ultrasonic sound velocity and the fuel dielectric constant in the fuel can be accurately determined. It becomes possible to measure.

By measuring the dielectric constant of the wave sound velocity and fuel propagating in fuel, alcohol fuel that likely but are calculation results of the two values with a precision that can be obtained from the relationship between the alcohol concentration of the sound velocity and the fuel It is possible to obtain a precise and single alcohol concentration as the calculation result by comparing the concentration and the alcohol concentration in the fuel of the single calculation result obtained from the relationship between the dielectric constant and the alcohol concentration in the fuel. Become. Therefore, the alcohol concentration in the fuel can be measured accurately and quickly.

  The sound velocity measurement unit includes a transmission unit that transmits ultrasonic waves of a predetermined frequency and a reception unit that receives ultrasonic waves. The ultrasonic wave emitted by the transmission unit is propagated through the fuel and received by the reception unit. The speed of sound in the fuel may be measured. By measuring the speed of sound waves propagating in the fuel by receiving and transmitting ultrasonic waves, it is possible to accurately measure sound waves. The dielectric constant measuring unit may have an electrode pair in which two electrodes are opposed to each other, and measure the electric capacity by inserting fuel between the electrodes of the electrode pair to measure the dielectric constant of the fuel. It is easy to measure the electric capacity by sandwiching the fuel between the electrode pair, so that it is easy to measure the dielectric constant of the fuel.

In addition, a fuel flow path that is filled with fuel and a degassing flow path branched from the fuel flow path are provided, and a position downstream of the fuel flow from the position where the degassing flow path of the fuel flow path branches. In addition, a sound speed measuring unit may be arranged. There is a possibility that gas such as carbon dioxide is mixed in the fuel, and when measuring the sound velocity of sound waves propagating in the fuel, if the gas stays in the fuel, the accurate sound velocity is measured. It becomes difficult. By branching the degassing channel from the fuel channel and measuring the sonic velocity downstream of the branching position with the degassing channel, the decrease in measurement accuracy due to the influence of gas is eliminated and the accurate sonic velocity is reduced. Measurement can be performed. If an accurate sound speed can be measured, the information processing unit can calculate an accurate alcohol concentration.

It is an external appearance perspective view which shows the structural example of the fuel concentration measuring apparatus of this invention. FIG. 2 is a cross-sectional perspective view showing an internal configuration of the fuel concentration measuring apparatus of the present invention shown in FIG. It is sectional drawing which shows the internal structure cut | disconnected in the surface direction of the fuel concentration measuring apparatus arrow A of this invention shown in FIG. It is a graph which shows the relationship between the sound speed of the ultrasonic wave in a fuel , and the alcohol concentration in a fuel, and the relationship between the dielectric constant of a fuel , and the alcohol concentration in a fuel. FIG. 2 is a cross-sectional perspective view showing an internal configuration of the fuel concentration measuring device of the present invention shown in FIG. Conventional is a graph showing the relationship between alcohol concentration and the sound velocity in the fuel in the case of measuring the alcohol concentration in the fuel in an ultrasonic system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing | casing 2 Ultrasonic unit 2a Transmitting part 2b Receiving part 3 Sound wave reflection part 4 Information processing part 5 Temperature sensor 6 Permittivity measurement part 7 Opening part 8 Fuel flow path 8 Opening part 9 Degassing flow path 10 Bulkhead 11 Communication flow path 12 Vent

Claims (8)

A fuel concentration measuring device for measuring alcohol concentration in fuel,
A sound speed measuring unit for measuring the speed of sound waves propagating in the fuel;
A dielectric constant measuring unit for measuring a dielectric constant of the fuel;
An information processing unit that calculates the alcohol concentration in the fuel based on the sound velocity measured by the sound velocity measuring unit and the dielectric constant measured by the dielectric constant measuring unit;
The sound speed measurement unit from measuring the sound velocity of the sound waves to calculate the speed of sound was measured, the speed of sound and the alcohol concentration d ₁ and a curve showing the relationship between the alcohol concentration, d _2,
Of the calculated d ₁ and d ₂ , the fuel concentration measurement is characterized in that the alcohol concentration in the fuel that is closer to the alcohol concentration corresponding to the dielectric constant measured by the dielectric constant measurement unit is the accurate alcohol concentration in the fuel. apparatus. The sound velocity measurement unit includes a transmission unit that transmits ultrasonic waves of a predetermined frequency, and a reception unit that receives ultrasonic waves,
2. The fuel concentration measurement according to claim 1, wherein the ultrasonic wave emitted from the transmitter is propagated through the fuel and the ultrasonic wave is received by the receiver so that the speed of sound in the fuel is measured. apparatus.   The dielectric constant measuring unit has an electrode pair in which two electrodes are opposed to each other, and measures the electric permittivity by sandwiching the fuel between the electrodes of the electrode pair to measure the dielectric constant of the fuel. The fuel concentration measuring device according to claim 1. A fuel passage filled with the fuel and a degassing passage branched from the fuel passage;
2. The fuel concentration measuring device according to claim 1, wherein the sonic speed measuring unit is disposed at a position downstream of the fuel flow path from the position where the degassing flow path branches. A fuel concentration measurement method for measuring alcohol concentration in fuel,
A step of measuring the sound waves of sound propagating through the fuel, the dielectric constant of the fuel,
Calculating alcohol concentrations d ₁ and d ₂ from the measured sound speed and a curve indicating the relationship between the sound speed and the alcohol concentration;
A fuel concentration measuring method comprising the step of setting an accurate alcohol concentration in the fuel that is closer to the alcohol concentration in the fuel corresponding to the measured dielectric constant among the calculated d ₁ and d ₂ .   6. The fuel concentration measuring method according to claim 5, wherein the speed of sound is measured by measuring a propagation time of an ultrasonic wave propagating through the fuel.   6. The fuel concentration measuring method according to claim 5, wherein the fuel is sandwiched between an electrode pair in which two electrodes are opposed to each other, and the dielectric constant is measured by measuring an electric capacity between the electrodes. Separating the gas mixed in the fuel from the fuel;
6. The fuel concentration measuring method according to claim 5, wherein the speed of sound is measured after separating the gas.

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