Device for detecting flow velocity of fuel gas in fuel gas pipe and range hood

Abstract

The invention relates to a device for detecting the flow rate of fuel gas in a fuel gas pipe and a range hood, and the device comprises a surface acoustic wave sensor which is tightly attached to the outer wall of the fuel gas pipe connected with a kitchen range, and is used for transmitting an excitation sound wave signal into the fuel gas pipe connected with the kitchen range, outputting a returned reflected wave frequency deviation signal delta f and a reflected wave amplitude attenuation rate beta; the signal analysis module is connected with the output end of the surface acoustic wave sensor, and is used for measuring the contents of methane, ethane and propane flowing through the gas pipe according to delta f and beta, and calculating the flow rate of the gas flowing through the gas pipe after the gas is converted into a standard methane heat value, and recording the flow rate as vstd; and the signal sending module is connected with the signal analysis module and is used for sending the vstd obtained by the signal analysis module to external equipment. Compared with the prior art, the method has the advantages that the actual components of the fuel gas in the fuel gas pipe can be measured without intrusive installation, and the fuel gas flow rate after the standard methane heat value is converted according to the actual components of the fuel gas can be obtained.

Description

Technical Field

[0001] The present invention relates to a detection device capable of detecting the gas flow rate and gas components in a gas pipe connected to a stove, and a range hood capable of being linked controlled with the stove. Background Art

[0002] Range hoods are essential appliances for daily cooking and smoke extraction. Combo products with a range hood and stove linkage function have become increasingly popular in recent years. However, existing range hood and stove linkage products have the following drawbacks:

[0003] First, these packaged products often only include the special models of certain manufacturers. Even if users choose range hoods and stoves from the same manufacturer, their choice of combinations will be limited, not to mention that some users have to choose range hoods and stoves from two different manufacturers.

[0004] Second, some products utilize infrared temperature sensors and other detection components installed on range hoods to perform non-contact temperature measurement of pots, burners, and other areas above the stove. These sensors attempt to determine the stove's open or closed status based on temperature changes. However, these infrared temperature sensors currently measure the average temperature of a large area encompassing the stovetop. The localized temperature rise at the moment of opening or closing has little impact on the results. Furthermore, the temperature measured when the pot lid is covered is easily averaged by the surrounding low-temperature area, leading to widespread misjudgment, such as accidental shutdowns and inactions. This can even cause the range hood to shut down mid-cooking, reducing the user experience. Furthermore, the temperature measurement method uses regional temperature changes to infer whether the stove is open or closed to adjust the range hood's status, which inherently lags behind the actual on / off state.

[0005] Third, some products install flow sensors on the stove to detect the stove's open / close status, or detect the flow rate in the pipeline by monitoring the knob position to determine the stove's open / close status, or measure the position of the stove's ignition knob to detect the stove's open / close status. However, these detection methods often require invasive installation of the detection components, which can easily lead to safety issues such as gas leaks. Furthermore, the content of methane, ethane, and propane in natural gas is not fixed; the content of these components can vary depending on the region and the source of the natural gas. For example, in some natural gas fields, the methane content may be higher, while the ethane and propane contents may be lower. Components like propane have a much higher calorific value than methane. Therefore, these differences in composition can result in different calorific values ​​for the natural gas supplied at different times at the same flow rate or velocity. This can also result in different fire levels even if the user turns the knob in the same position, making this solution inaccurate.

[0006] Therefore, the above-mentioned prior art needs to be further improved. Summary of the Invention

[0007] The first technical problem to be solved by the present invention is to provide a gas flow rate detection device in a gas pipe in response to the above-mentioned prior art. The detection device can measure the actual components of the gas inside the gas pipe and convert the gas flow rate after the standard methane calorific value is converted according to the actual components of the gas without the need for invasive installation.

[0008] The second technical problem to be solved by the present invention is to provide a range hood that can be linked controlled according to the gas flow rate inside the gas pipe connected to the stove, based on the above-mentioned existing technology. The detection of the gas flow rate inside the gas pipe does not require invasive installation and can measure the actual components of the gas inside the gas pipe and convert the gas flow rate after the standard methane calorific value is calculated based on the actual components of the gas.

[0009] The technical solution adopted by the present invention to solve the first technical problem is: a gas flow rate detection device in a gas pipe, characterized by comprising:

[0010] The surface acoustic wave sensor is attached to the outer wall of the gas pipe connected to the cooker, and is used to send an excitation acoustic wave signal into the gas pipe connected to the cooker, and output a returned reflected wave frequency shift signal Δf and a reflected wave amplitude attenuation rate β;

[0011] The signal analysis module is connected to the output end of the surface acoustic wave sensor. It measures the content of methane, ethane, and propane flowing through the gas pipe based on the reflected wave frequency offset signal Δf and the reflected wave amplitude attenuation rate β output by the surface acoustic wave sensor. At the same time, it calculates the gas flow rate flowing through the gas pipe after converting it into the standard methane calorific value based on the content of methane, ethane, and propane flowing through the gas pipe, which is recorded as v std ;

[0012] The signal sending module is connected to the signal analysis module and is used to send the signal obtained by the signal analysis module to the std Send to external device.

[0013] As an improvement, the signal analysis module calculates and measures the content of methane, ethane and propane in the gas pipe and v std :

[0014] Step 1: First calculate the propagation attenuation constant α:

[0015]

[0016] Where L is the propagation path of the excitation acoustic wave signal generated by the surface acoustic wave sensor, which is a preset constant; β is the attenuation rate of the reflected wave amplitude output by the surface acoustic wave sensor;

[0017] Step 2: Calculate the imaginary part of the dielectric constant ε″ mix :

[0018]

[0019] ε′ mix is the dielectric constant, and when the first iteration is taken, ε′ mix =1.001; c is the electromagnetic wave speed, c=3×10 8 m / s; ω = 2πf0, f0 is the operating frequency of the surface acoustic wave sensor and is a constant;

[0020] Step 3. Solve the following linear equations to obtain x1, x2, and x3:

[0021]

[0022] Among them, x1 is the content of methane CH4; x2 is the content of ethane C2H6, and x3 is the content of propane C3H8;

[0023]

[0024] Step 4. Substitute x1, x2, and x3 calculated in step 3 into the following equation:

[0025]

[0026] Then the new dielectric constant ε′ is calculated m ix;

[0027] Step 5: Determine the new dielectric constant ε′ obtained in step 4 mix Compared with the dielectric constant ε′ obtained last time mix Is the absolute value of the difference less than 1×10 -6 If yes, output x1, x2, x3, and then go to step 6; if no, update the dielectric constant ε′ mix , then repeat steps 2 to 5 for iterative calculation;

[0028] Step 6: Calculate the gas flow rate v after converting to standard methane calorific value std :

[0029]

[0030] Among them, v real =K×Δf, where K is the calibration coefficient, which is a preset constant; Δf is the reflected wave frequency offset signal output by the surface acoustic wave sensor.

[0031] Preferably, L = 5 mm. f0 = 433 Hz. K = f0kηδ / G; wherein f0 = 433 MHz, k is the piezoelectric coupling coefficient, k = 0.032, δ is the thickness of the gas pipe wall; η is the gas viscosity; G is the shear modulus of the substrate in the surface acoustic wave sensor, G = 7.5×1010 Pa; K values ​​are calibrated through previous experiments and saved in advance.

[0032] The technical solution adopted by the present invention to solve the second technical problem is: a range hood, comprising a body, a fan system is provided in the body, and the feature is that the body is further provided with a signal receiving module that can match the signal sending module of the gas flow rate detection device in the gas pipe, when the signal receiving module receives the gas flow rate v sent by the signal sending module of the gas flow rate detection device in the gas pipe std Then, according to the gas flow rate v std To adjust the gear of the fan system, the specific control method is:

[0033] If v std Less than v a , judging that the current fire power of the stove is low fire power, and adjusting the gear of the fan system to low gear;

[0034] If v std Greater than or equal to v a Less than or equal to v b , judging that the current fire power of the stove is medium fire power, and adjusting the gear of the fan system to the medium gear;

[0035] If v std Greater than v b , judging that the current fire power of the stove is high fire power, adjusting the gear of the fan system to high gear;

[0036] v a 、v b is a preset constant, and v a <v b .

[0037] Better, v a =0.5m / s, v b =1.2m / s.

[0038] The signal sending module and the signal receiving module are paired signal communication modules.

[0039] Compared with the prior art, the advantages of the present invention are as follows: the gas flow rate detection device in the gas pipe is provided with a surface acoustic wave sensor attached to the surface of the gas pipe. This non-invasive installation method does not require drilling holes in the gas pipe and has high structural reliability; and the surface acoustic wave sensor can detect low-speed flows of less than 0.03 m / s. Compared with the hysteresis detection of infrared and oil smoke sensors, the sensitivity of the present application scheme is greatly improved; at the same time, it can measure the actual composition of the gas inside the gas pipe, and convert the gas flow rate after the standard methane calorific value is converted according to the actual composition of the gas, thereby solving the problem of unstable natural gas supply source causing component changes and calorific value fluctuations and thus fire power fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the installation structure of the gas flow rate detection device in the gas pipe in an embodiment of the present invention.

[0041] Figure 2 Schematic diagram of the linkage structure of a cooker and a range hood in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0043] This embodiment first provides a gas flow rate detection device in a gas pipe, which includes:

[0044] The surface acoustic wave sensor 1 is attached to the outer wall of the gas pipe 2 connected to the stove. Figure 1 As shown, it is used to send an excitation sound wave signal into the gas pipe 1 connected to the stove, and output a returned reflected wave frequency offset signal Δf and a reflected wave amplitude attenuation rate β; the surface acoustic wave sensor 1 includes a piezoelectric substrate 11, a transducer 12, a reflection grid 13 and an emission detection circuit 14, wherein the piezoelectric substrate 11 is usually made of lithium tantalate (LiTaO3) material for generating surface shear waves; the transducer 12 is also called an interdigital transducer IDT, which generally includes multiple pairs of aluminum electrodes for determining the operating frequency f0, such as f0 = 433 MHz in this embodiment; the reflection grid 13 is composed of multiple groups, such as 50 groups, of periodic grooves to increase the reflection ability so that the reflection coefficient is greater than 95%; the emission detection circuit 14 is composed of a transmitting signal circuit and a detecting signal circuit; the core working principle of the surface acoustic wave sensor 1 is: using the changes in the acoustic wave characteristics (such as speed and wavelength) propagating on the surface of the piezoelectric substrate material to convert external physical or chemical parameters (such as pressure, temperature, and gas concentration) into a measurable frequency signal; in the actual detection process, the transducer 12 uses the transmitting and detecting circuit 14 to transmit a 433MHz radio frequency signal to excite the surface acoustic wave. When the gas in the gas pipe flows, the pipe wall shear stress τ is generated, causing the piezoelectric substrate to deform. The shear stress causes the surface wave velocity to change. At this time, the reflection grid 13 returns to the transducer, and the reflected wave frequency offset signal Δf and the reflected wave amplitude attenuation rate β are obtained;

[0045] The signal analysis module 3 is connected to the output end of the surface acoustic wave sensor and can be set close to the surface acoustic wave sensor 1 and also close to the outer wall of the gas pipe 2 connected to the stove. Based on the reflected wave frequency offset signal Δf and the reflected wave amplitude attenuation rate β output by the surface acoustic wave sensor, the content of methane, ethane and propane flowing through the gas pipe is measured. At the same time, based on the content of methane, ethane and propane flowing through the gas pipe, the gas flow rate flowing through the gas pipe after conversion to the standard methane calorific value is calculated, which is recorded as v std ;

[0046] The signal sending module 4 is connected to the signal analysis module 3 and can be set close to the signal analysis module 3 and also close to the outer wall of the gas pipe 2 connected to the stove, and is used to transmit the v obtained by the signal analysis module std Send to external device.

[0047] In this embodiment, the signal analysis module calculates and measures the content of methane, ethane and propane in the gas pipe and v std :

[0048] Step 1: First calculate the propagation attenuation constant α:

[0049]

[0050] Wherein, L is the propagation path of the excitation acoustic wave signal generated by the surface acoustic wave sensor, which is a preset constant. In this embodiment, L=50×0.1mm=5mm; β is the attenuation rate of the reflected wave amplitude output by the surface acoustic wave sensor;

[0051] Step 2: Calculate the imaginary part of the dielectric constant ε″ mix :

[0052]

[0053] ε′ mix is the dielectric constant, and when the first iteration is taken, ε′ mix =1.001; c is the electromagnetic wave speed, c=3×10 8 m / s; ω = 2πf0, f0 is the operating frequency of the surface acoustic wave sensor, which is a constant. In this embodiment, f0 = 433 Hz;

[0054] Step 3. Solve the following linear equations to obtain x1, x2, and x3:

[0055]

[0056] Among them, x1 is the content of methane CH4; x2 is the content of ethane C2H6, and x3 is the content of propane C3H8;

[0057]

[0058] Step 4. Substitute x1, x2, and x3 calculated in step 3 into the following equation:

[0059]

[0060] Then the new dielectric constant ε′ is calculated m ix;

[0061] Step 5: Determine the new dielectric constant ε′ obtained in step 4 mix Compared with the dielectric constant ε′ obtained last time mix Is the absolute value of the difference less than 1×10 -6 If yes, output x1, x2, x3, and then go to step 6; if no, update the dielectric constant ε′ mix , then repeat steps 2 to 5 for iterative calculation;

[0062] Step 6: Calculate the gas flow rate v after converting to standard methane calorific value std :

[0063]

[0064] Among them, v real =K×Δf, K is the calibration coefficient, which is a preset constant, K=f0kηδ / G; where f0=433Hz, k is the piezoelectric coupling coefficient, k=0.032, δ is the wall thickness of the gas pipe; η is the gas viscosity; G is the shear modulus of the substrate in the surface acoustic wave sensor, G=7.5×10 10 Pa; the K value is calibrated through previous experiments and saved in advance; Δf is the reflected wave frequency offset signal output by the surface acoustic wave sensor.

[0065] This embodiment also provides a range hood that can be controlled in conjunction with a stove, comprising a body 101, wherein a fan system 102 is provided in the body 101. Figure 2 As shown, the range hood can be linked with the stove 103 below, and the gas flow rate detection device in the gas pipe with the above structure is installed on the outer wall of the gas pipe connected to the gas inlet at the bottom of the stove 103; the body 101 is also provided with a signal receiving module 104 that can be matched with the signal sending module 4 of the gas flow rate detection device in the gas pipe. When the signal receiving module receives the gas flow rate v sent by the signal sending module of the gas flow rate detection device in the gas pipe, the signal receiving module receives the gas flow rate v std Then, according to the gas flow rate v std To adjust the gear of the fan system, the specific control method is:

[0066] If v std Less than v a , judging that the current fire power of the stove is low fire power, and adjusting the gear of the fan system to low gear;

[0067] If v std Greater than or equal to v a Less than or equal to v b , judging that the current fire power of the stove is medium fire power, and adjusting the gear of the fan system to the medium gear;

[0068] If v std Greater than vb , judging that the current fire power of the stove is high fire power, adjusting the gear of the fan system to high gear;

[0069] v a 、v b is a preset constant, and v a <v b ;v a =0.5m / s, v b =1.2m / s.

[0070] The signal sending module and the signal receiving module are paired signal communication modules.

Claims

1. A gas flow rate detection device in a gas pipe, characterized in that include: The surface acoustic wave sensor is attached to the outer wall of the gas pipe connected to the cooker, and is used to send an excitation acoustic wave signal into the gas pipe connected to the cooker, and output a returned reflected wave frequency shift signal Δf and a reflected wave amplitude attenuation rate β; The signal analysis module is connected to the output end of the surface acoustic wave sensor. It measures the content of methane, ethane, and propane flowing through the gas pipe based on the reflected wave frequency offset signal Δf and the reflected wave amplitude attenuation rate β output by the surface acoustic wave sensor. At the same time, it calculates the gas flow rate flowing through the gas pipe after converting it into the standard methane calorific value based on the content of methane, ethane, and propane flowing through the gas pipe, which is recorded as v std ; The signal sending module is connected to the signal analysis module and is used to send the signal obtained by the signal analysis module to the std Send to external device.

2. The gas flow rate detection device in a gas pipe according to claim 1, characterized in that: The signal analysis module calculates and measures the content of methane, ethane and propane in the gas pipe and v std : Step 1: First calculate the propagation attenuation constant α: Where L is the propagation path of the excitation acoustic wave signal generated by the surface acoustic wave sensor, which is a preset constant; β is the attenuation rate of the reflected wave amplitude output by the surface acoustic wave sensor; Step 2: Calculate the imaginary part of the dielectric constant ε″ mix : ε′ mix is the dielectric constant, and when the first iteration is taken, ε′ mix =1.001; c is the electromagnetic wave speed, c=3×10 8 m / s; ω = 2πf0, f0 is the operating frequency of the surface acoustic wave sensor and is a constant; Step 3. Solve the following linear equations to obtain x1, x2, and x3: Wherein, x1 is the content of methane CH4; x2 is the content of ethane C2H6; x3 is the content of propane C3H8; Step 4. Substitute x1, x2, and x3 calculated in step 3 into the following equation: Then the new dielectric constant ε′ is calculated m ix; Step 5: Determine the new dielectric constant ε′ obtained in step 4 mix Compared with the dielectric constant ε′ obtained last time mix Is the absolute value of the difference less than 1×10 -6 If yes, output x1, x2, x3, and then go to step 6; if no, update the dielectric constant ε′ mix , then repeat steps 2 to 5 for iterative calculation; Step 6: Calculate the gas flow rate v after converting to standard methane calorific value std : Among them, v real =K×Δf, where K is the calibration coefficient, which is a preset constant; Δf is the reflected wave frequency offset signal output by the surface acoustic wave sensor.

3. The gas flow rate detection device in a gas pipe according to claim 2, characterized in that: Said L=5 mm.

4. The gas flow rate detection device in a gas pipe according to claim 2, characterized in that: The f0=433 MHz.

5. The gas flow rate detection device in a gas pipe according to claim 2, characterized in that: K = f0kηδ / G; where f0 = 433 Hz, k is the piezoelectric coupling coefficient, k = 0.032, δ is the thickness of the gas pipe wall; η is the gas viscosity; G is the shear modulus of the substrate in the surface acoustic wave sensor, G = 7.5×10 10 Pa; K values ​​are calibrated through previous experiments and saved in advance.

6. A range hood comprising a body, a fan system disposed therein, characterized in that: The body is also provided with a signal receiving module that can match the signal sending module of the gas flow rate detection device in the gas pipe according to claim 1 or 2. When the signal receiving module receives the gas flow rate v sent by the signal sending module of the gas flow rate detection device in the gas pipe, std Then, according to the gas flow rate v std To adjust the gear of the fan system, the specific control method is: If v std Less than v a , judging that the current fire power of the stove is low fire power, and adjusting the gear of the fan system to low gear; If v std Greater than or equal to v a Less than or equal to v b , judging that the current fire power of the stove is medium fire power, and adjusting the gear of the fan system to the medium gear; If v std Greater than v b , judging that the current fire power of the stove is high fire power, adjusting the gear of the fan system to high gear; v a 、v b is a preset constant, and v a <v b .

7. The range hood according to claim 6, characterized in that: v a =0.5m / s,v b =1.2m / s。 8. The range hood according to claim 6, characterized in that: The signal sending module and the signal receiving module are paired signal communication modules.

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