Thermal dispersion flow switch

Abstract

This utility model discloses a heat-dissipating flow switch, comprising: an electrical connector; a signal acquisition and processing unit; and a sensing probe unit. The sensing probe unit includes two probes, a heating probe and a non-heating probe, each probe being a cylindrical structure with an elliptical cross-section. The sensing probe unit is electrically connected to the input terminal of the signal acquisition and processing unit, and the output terminal of the signal acquisition and processing unit is electrically connected to the electrical connector. The heat-dissipating flow switch of this utility model uses an elliptical cylindrical probe, which can reduce the generation of turbulence, improve the flow state of the fluid, and enhance the sensitivity and stability of the probe in sensing fluid temperature.

Description

Technical Field

[0001] This utility model belongs to the field of flow measurement technology, specifically relating to a heat dissipation flow switch. Background Technology

[0002] The measurement and monitoring of liquid or gas flow rate are crucial parameters that need to be measured in industrial production processes, forming an important part of industrial manufacturing. They play a vital role in product quality assurance, energy supply, and computational metering. The reliability, stability, and environmental adaptability of flow switches all influence the development and progress of industrial technology.

[0003] With the rapid development of industrial and electronic technologies, aircraft avionics equipment is constantly being upgraded. Many types of sensors are used for measuring and monitoring the flow rate of liquids and gases, such as flow control sensors and impeller flow sensors. These sensors collect signals such as fluid temperature and pressure, converting them into flow rate or switching signals to measure the flow. However, due to the unstable flow state of liquids or gases, especially the significant impact of airflow during aircraft flight, the fluid state in fuel supply lines or environmental control systems becomes even more unstable, increasing the difficulty of accurately measuring and monitoring liquids or gases and affecting accuracy.

[0004] With the development of power electronics technology, the technical principles of flow switches are constantly being updated. Hot-wire flow switches use a thin metal wire with a heating current placed in the flow field to measure the fluid velocity and flow rate. However, hot-wire flow sensors are affected by multiple parameters, exhibiting cross-sensitivity, which affects their stability and sensitivity. Furthermore, the relationship between flow rate and electrical signal is non-linear, requiring compensation. Currently, various compensation technologies are constantly improving, greatly enhancing the accuracy of hot-wire flow sensors and expanding their measurement range. However, hot-wire flow switches suffer from poor consistency, making mass production difficult; significant thermal turbulence occurs when measuring low-velocity fluids; the hot wire has poor resistance to contamination and corrosion, resulting in high cost and easy damage; simultaneously, the surface of the hot-wire flow switch is easily contaminated by airborne dust, reducing its thermal radiation capacity and affecting accuracy; errors occur when the fluid velocity distribution is uneven; and electronic noise is generated during measurement, leading to a decrease in response speed. These factors limit their application in industry. Utility Model Content

[0005] The purpose of this invention is to provide a heat dissipation flow switch to solve the problems existing in the measurement of aircraft fluid flow.

[0006] This utility model is achieved through the following technical solution:

[0007] Thermal flow switches include:

[0008] Electrical connectors;

[0009] Signal acquisition and processing unit;

[0010] The sensing probe unit includes two probes, a heated probe and a non-heated probe, each probe being a columnar structure with an elliptical cross-section. The sensing probe unit is electrically connected to the input terminal of the signal acquisition and processing unit, and the output terminal of the signal acquisition and processing unit is electrically connected to an electrical connector.

[0011] In some embodiments, the long side of the elliptical cross-section of the probe is arranged along the fluid flow direction.

[0012] In some embodiments, the probe is provided with a sensing element.

[0013] In some embodiments, the device further includes a housing, the electrical connector being disposed at one open end of the housing and forming a closed cavity inside the housing, the signal acquisition and processing unit being disposed within the closed cavity, and the sensing probe being disposed at the other end of the housing.

[0014] In some embodiments, a mounting flange is provided at one end of the housing.

[0015] In some embodiments, a conduit is provided on the mounting flange, and the probe is disposed inside the conduit with one end extending outside the conduit.

[0016] In some embodiments, the signal acquisition and processing unit includes a power conversion circuit, a signal acquisition circuit, a comparison and amplification circuit, a filtering circuit, and a conversion output circuit;

[0017] The signal acquisition circuit is used to acquire signals from the heating probe and the non-heating probe. The comparison amplification circuit is used to output a voltage signal that is proportional to the temperature difference between the two probes. The conversion output circuit is used to output the voltage signal as a switching signal.

[0018] In some embodiments, the signal acquisition circuit employs a Wheatstone bridge circuit.

[0019] In some embodiments, the comparison amplifier circuit includes a resistor R111 connected to one output terminal of the Wheatstone bridge circuit and a diode V203, and a resistor R113 connected to the other output terminal of the Wheatstone bridge circuit. Resistors R111 and R113 are respectively connected to operational amplifier U1, and operational amplifier U1 is respectively connected to adjustable resistor RP102 and resistor R129.

[0020] In some embodiments, the filtering circuit includes capacitors C221, C223, and C224 connected to resistors R111 and R113, and a π-type filtering circuit connected to operational amplifier U1.

[0021] Compared with the prior art, this utility model has the following advantages and beneficial effects:

[0022] This utility model of a heat dissipation flow switch uses an elliptical cylindrical probe, which can reduce the generation of turbulence, improve the flow state of the fluid, and enhance the probe's sensitivity and stability in sensing fluid temperature.

[0023] This utility model of a heat-dissipating flow switch can be applied to aircraft environmental control systems to monitor the gas flow rate, improve the cabin environment, and enhance passenger comfort. It can also be applied to aircraft fuel supply lines to monitor fuel supply in real time, ensuring the normal operation of the fuel supply system, and has broad application prospects. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a top view of the heat dissipation flow switch structure according to an embodiment of this utility model.

[0026] Figure 2 This is a front view of the heat dissipation flow switch structure according to an embodiment of this utility model.

[0027] Figure 3 This is a bottom view of the heat dissipation flow switch structure according to an embodiment of this utility model.

[0028] Figure 4 This is a schematic diagram of the working state of the heat dissipation flow switch according to an embodiment of this utility model.

[0029] Figure 5 This is the circuit principle frame of the signal acquisition and processing unit in an embodiment of this utility model.

[0030] Figure 6 This is a circuit diagram of the comparison and amplification circuit of the signal acquisition and processing unit in an embodiment of this utility model.

[0031] Figure 7 This is a circuit diagram of the signal acquisition and processing unit conversion output circuit of this utility model embodiment.

[0032] in:

[0033] 10. Electrical connectors;

[0034] 20. Housing; 21. Mounting flange; 22. Conduit;

[0035] 30. Probe. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0037] The heat dissipation type flow switch adopts heat dissipation technology and has no moving parts. The product features small size, light weight, easy installation, low flow rate sensitivity, high reliability, low cost, strong compatibility, low power consumption, and short response time.

[0038] Thermal flow switches enable direct measurement and monitoring of fluids. Since changes in ambient temperature have an almost equal impact on both probes, the influence of ambient temperature on measurement and monitoring can be eliminated, and the output flow switch signal is more stable and reliable.

[0039] In some embodiments of this utility model, reference is made to... Figure 1 , Figure 2 , Figure 3 and Figure 4 The thermal flow switch includes an electrical connector 10, a signal acquisition and processing unit, and a sensing probe unit.

[0040] The electrical connector 10 is fixed to the cylindrical housing 20 with screws. A conductive rubber gasket seals the connection between the connector flange and the housing 20, creating a sealed cavity inside the housing. The electrical connector facilitates signal exchange between the thermal flow switch and the aircraft avionics system. The avionics system provides the necessary power to the thermal flow switch through the connector, ensuring its normal and stable operation. Simultaneously, the thermal flow switch transmits its output signal to the avionics system via the connector to monitor fluid flow.

[0041] The signal acquisition and processing unit is housed within the enclosed cavity of the housing.

[0042] The induction probe unit includes two probes 30, one heated probe and the other unheated probe. Both probes are elliptical cylindrical, meaning that the cross-section of the probe is elliptical. When fluid flows through the elliptical cylindrical probe, it can effectively reduce vibration and noise and reduce eddy currents, resulting in less interference with fluid flow and effectively improving measurement accuracy.

[0043] The measurement principle of heat dissipation flow switches is based on the heat dissipation effect. They are very sensitive to changes in fluid temperature and need to be able to sense fluid temperature stably. Using an elliptical cylindrical probe can reduce the generation of turbulence, improve the fluid flow state, and enhance the probe's sensitivity and stability in sensing fluid temperature.

[0044] The probe 30 has a sensing element inside. The two probes are independent of each other and do not come into contact with each other structurally, ensuring that the two probes do not affect each other.

[0045] Of the two probes, the heating probe is heated by an electric current, generating heat. Both probes are temperature-sensitive. One end of each probe extends into the fuel supply line of the fuel system. When fluid flows through the probe, according to Newton's law of cooling:

[0046] Q = aS△T;

[0047] In the formula, a is the convective heat dissipation coefficient, with units of W / m²K; S is the surface area of ​​the probe; and ΔT is the temperature change value.

[0048] The convective heat transfer coefficient α is the main factor affecting the probe surface temperature. Convective heat transfer coefficient:

[0049] a = Nuλ / d;

[0050] In the formula, Nu is the Nusselt number; λ is the thermal conductivity; and d is the width of the probe.

[0051] When Nu is dissipating heat through convection, we have:

[0052] Nu = c(Vd / v)^m;

[0053] In the formula, c is a constant; V is the fluid velocity; v is the kinematic viscosity coefficient; and m is determined based on experimental data analysis.

[0054] Therefore, we can conclude that:

[0055] Q=cd^(m-1) / v^m·V^m·λS△T.

[0056] The liquid or gas flowing through the probe cools it, and the higher the flow rate, the more significant the cooling effect. Simultaneously, the rapid flow of the liquid or gas can lower the temperature of the heated probe to ambient temperature, i.e., the temperature of the non-heated end. Due to the presence of heat, the output signals of the two probes always differ, and the greater the fluid flow rate, the greater the difference in output signals between the two probes.

[0057] The signal acquisition and processing circuit of the thermal flow switch acquires and transforms the output signals of the two probes, and finally outputs a switching signal to realize the measurement and monitoring of fluid flow rate.

[0058] The signal acquisition and processing unit of the thermal flow switch is implemented through analog circuits. The signal acquisition and processing unit includes a power conversion circuit, a signal acquisition circuit, a comparison and amplification circuit, a filtering circuit, and a conversion output circuit. The signal acquisition circuit is used to acquire signals from the heating probe and the non-heating probe. The comparison and amplification circuit is used to output a voltage signal that is proportional to the temperature difference between the two probes. The conversion output circuit is used to output the voltage signal as a switching signal. The power conversion circuit provides the power supply voltage required for the operation of the thermal flow switch.

[0059] like Figure 5 The signal acquisition circuit uses a Wheatstone bridge circuit.

[0060] like Figure 6 The comparator amplifier circuit includes a resistor R111 and a diode V203 connected to one output terminal of the Wheatstone bridge circuit, and a resistor R113 connected to the other output terminal of the Wheatstone bridge circuit. Resistors R111 and R113 are respectively connected to operational amplifier U1, and operational amplifier U1 is respectively connected to adjustable resistor RP102 and resistor R129.

[0061] The filter circuit includes capacitors C221, C223, and C224 connected to resistors R111 and R113, as well as a π-type filter circuit connected to operational amplifier U1.

[0062] like Figure 7 The output conversion circuit includes resistor R7, capacitor C4, resistor R8, operational amplifier U2, resistor R9, and diode V3.

[0063] like Figure 5 The probe's output signal, based on the heat dissipation effect, is compared and amplified. A secondary power conversion is performed to obtain the DC voltage required for the analog circuit and output signal. Then, a Wheatstone bridge circuit is used to acquire signals from both the heated and non-heated probes. Resistors R1, R2, R3, and R4 are the four arms of the bridge. When the voltage between points B and C is zero, the bridge is balanced. At this point, the resistance values ​​of the four arms satisfy a simple relationship, which can be used to measure the resistance. Furthermore, changing the value of any resistor in the bridge causes the voltage difference between B and C to change accordingly. Therefore, based on the voltage between B and C and with other known unchanging resistances, the resistance value of the changing resistor can be determined.

[0064] The Wheatstone bridge circuit acquires signals from the heated and non-heated probes, then outputs a voltage signal proportional to the temperature difference between the two probes via a comparison and amplification circuit. Figure 6Signal inputs B and C are the outputs of the pre-amplifier Wheatstone bridge and serve as the inputs to the comparator amplifier circuit. The transient suppression diode V203 in the comparator amplifier circuit prevents circuit surges, acting as a protection circuit. After passing through the current-limiting resistor, C221, C223, and C224 filter the input signal. The signal is then amplified by the operational amplifier and output as a voltage signal. The subsequent stage uses a π-type filter circuit for further voltage filtering, and finally, a stable switching signal is output through the conversion output circuit. This enables the measurement and monitoring of fluid flow in the pipeline. The conversion output circuit is as follows: Figure 7 As shown.

[0065] The thermally ventilated flow switch uses electrical connectors conforming to the GJB599AⅢ series, featuring quick-connect via a three-pronged thread, anti-loosening function, small size, light weight, and electromagnetic shielding, enabling use in harsh environments. The electrical connectors achieve contact through pins and sockets, with high contact density ensuring stable, reliable, and interference-free signals.

[0066] A mounting flange 21 is provided at one end of the housing 20, and a cylindrical conduit 22 is provided on the other side of the mounting flange 21. Two probes 30 are provided inside the conduit 22, with one end of the probes 30 extending out of the conduit. The mounting flange 21 is used for the fixed installation of the heat dissipation flow switch on the aircraft pipeline.

[0067] The housing 20, mounting flange 21, and conduit 22 are integrally machined, and the strength of the heat dissipation flow switch meets the requirements of aircraft flight.

[0068] The sensing parts of both probes extend into the fluid inside the pipeline to sense the degree of heat dissipation. The two probes are fixed to the bottom of the cylindrical conduit by laser welding for easy assembly.

[0069] The entire housing, mounting flange, and ducts are made of stainless steel, with no moving parts, ensuring the reliability and stability of the aircraft during use.

[0070] Both probes of the heat dissipation flow switch are temperature sensitive. The sensing element inside the probe senses the heat dissipation on the outer surface of the probe, and the probe outputs a signal to the signal acquisition and processing unit for switching output.

[0071] The current flowing through the heating probe generates heat, which heats the sensitive element inside the probe. The fluid flowing through the probe cools it; the higher the fluid velocity, the more significant the cooling effect. The rapid flow of fluid attempts to lower the probe's temperature to ambient temperature. Because the current flowing through the resistor always generates heat, a difference in the output signals of the two probes persists. A greater fluid velocity results in a larger difference in the output signals. This difference is accurately acquired using a Wheatstone bridge, the parameters of which need to be designed and simulated according to actual application requirements. The signal acquisition and processing unit acquires and transforms the output signals from both probes, ultimately outputting a switching signal to measure and monitor the fluid flow rate.

[0072] Thermal flow switches can be applied to aircraft environmental control systems to monitor gas flow rates, improve the cabin environment, and enhance passenger comfort. They can also be applied to aircraft fuel supply lines to monitor fuel supply in real time, ensuring normal operation and enabling safe and stable flight.

[0073] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", and "outer" used to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only used to facilitate the description of this utility model and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0074] Furthermore, the use of terms such as "horizontal" or "vertical" in the description of this utility model does not imply that the component is required to be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0075] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0076] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A heat-dissipating flow switch, characterized in that, include: Electrical connectors; Signal acquisition and processing unit; The sensing probe unit includes two probes, a heated probe and a non-heated probe, each probe being a columnar structure with an elliptical cross-section. The sensing probe unit is electrically connected to the input terminal of the signal acquisition and processing unit, and the output terminal of the signal acquisition and processing unit is electrically connected to an electrical connector.

2. The heat-dissipating flow switch according to claim 1, characterized in that, The long side of the elliptical cross-section of the probe is positioned along the direction of fluid flow.

3. The heat-dissipating flow switch according to claim 1, characterized in that, The probe contains a sensing element.

4. The heat-dissipating flow switch according to claim 1, characterized in that, It also includes a housing, the electrical connector is disposed at one open end of the housing, and the interior of the housing forms a closed cavity, the signal acquisition and processing unit is disposed in the closed cavity, and the sensing probe is disposed at the other end of the housing.

5. The heat-dissipating flow switch according to claim 4, characterized in that, A mounting flange is provided at one end of the housing.

6. The heat-dissipating flow switch according to claim 5, characterized in that, A conduit is provided on the mounting flange, and the probe is located inside the conduit with one end extending outside the conduit.

7. The heat-dissipating flow switch according to claim 1, characterized in that, The signal acquisition and processing unit includes a power conversion circuit, a signal acquisition circuit, a comparison and amplification circuit, a filtering circuit, and a conversion output circuit. The signal acquisition circuit is used to acquire signals from the heating probe and the non-heating probe. The comparison amplification circuit is used to output a voltage signal that is proportional to the temperature difference between the two probes. The conversion output circuit is used to output the voltage signal as a switching signal.

8. The heat-dissipating flow switch according to claim 7, characterized in that, The signal acquisition circuit uses a Wheatstone bridge circuit.

9. The heat-dissipating flow switch according to claim 8, characterized in that, The comparison amplifier circuit includes a resistor R111 and a diode V203 connected to one output terminal of the Wheatstone bridge circuit, and a resistor R113 connected to the other output terminal of the Wheatstone bridge circuit. Resistors R111 and R113 are respectively connected to operational amplifier U1, which is connected to adjustable resistor RP102 and resistor R129 respectively.

10. The heat-dissipating flow switch according to claim 9, characterized in that, The filtering circuit includes capacitors C221, C223, and C224 connected to resistors R111 and R113, and a π-type filtering circuit connected to operational amplifier U1.

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