Combined type flow transmitter

Abstract

The utility model discloses a combined type flow transmitter which comprises an acquisition module used for acquiring the current flow, flow direction and pressure of compressed air in a train pipe; a processing module; the data processing module is connected with the acquisition module and is used for processing data acquired by the acquisition module; and an output module; the data conversion module is connected with the processing module and is used for converting the data processed by the data processing module into current signals and outputting the current signals; the acquisition module comprises a thermal mass acquisition unit used for acquiring the flow rate and the flow direction of the compressed air in the vehicle pipe when the flow rate is low, and a pressure difference acquisition unit used for acquiring the pressure of the compressed air in the vehicle pipe when the flow rate is high; the advantages of differential pressure type and thermal type mass flow monitoring are combined, a thermal type mass calculation mode is adopted for monitoring when the flow is low, a differential pressure type calculation mode is adopted when the flow is high, and the advantages of wide measuring range, high precision, fast response, direction recognition and the like are all combined.

Description

Technical Field

[0001] The utility model relates to a transmitter, in particular to a composite flow transmitter. Background Art

[0002] There are various types of flow transmitters commonly used in the industrial field. However, currently, there are only two types of flow transmitters that are truly mass-produced and used in the rail transit air duct system in terms of principle. One is a differential pressure type flow transmitter, and the other is a thermal mass flow transmitter.

[0003] Among them, the differential pressure type flow transmitter has a fast response time and can detect the flow rate of 10 - 100% of the full scale, but it cannot identify micro flow rates.

[0004] Among them, although the thermal flow transmitter can monitor micro flow rates, its response time is long, and it is greatly affected by temperature, and a separate temperature compensation algorithm is required.

[0005] At present, domestic heavy-haul trains are regularly running at 20,000 tons and 10,000 tons. Due to the complex line, once the train pipe pressure fluctuates abnormally or leaks, it may cause abnormal release and braking of the train. In the lightest case, it may cause large longitudinal impulses of the train and emergency stops. In the most serious case, it may lead to the fracture of the coupler knuckle, train separation or derailment; when the train pipe of the heavy-haul train braking system undergoes abnormal emergency braking, a rapid response to the instantaneous flow rate and flow direction of the compressed air in the train pipe is required. However, both of the above two flow monitoring devices have their own limitations in the train braking system and cannot achieve a rapid response. Content of the Utility Model

[0006] Therefore, in order to solve the above deficiencies, the utility model provides a composite flow transmitter here. This flow transmitter combines the advantages of differential pressure type and thermal mass flow monitoring. When the flow rate is low, the thermal mass calculation method is used for monitoring, and when the flow rate is high, the differential pressure type calculation method is used, so that it combines all the advantages of the two flow monitoring methods, such as wide range, high precision, fast response, and direction recognition.

[0007] Specifically, a composite flow transmitter includes

[0008] An acquisition module, which is used to acquire the current flow rate, flow direction, and pressure of the compressed air in the train pipe;

[0009] A processing module; connected to the acquisition module, which is used to process the data acquired by the acquisition module; and

[0010] An output module; connected to the processing module, which is used to convert the data processed by the data processing module into a current signal and output it;

[0011] The acquisition module includes:

[0012] The thermal mass acquisition unit is used to acquire the flow rate and flow direction of compressed air in the train pipe at low flow rates, and

[0013] the differential pressure acquisition unit is used to acquire the pressure of compressed air in the train pipe at high flow rates.

[0014] Optionally, the thermal mass acquisition unit includes a thermal mass flow probe, a temperature acquisition circuit, a flow rate acquisition circuit, and a flow direction acquisition circuit.

[0015] The thermal mass flow probe is connected to the flow rate acquisition circuit and the flow direction acquisition circuit respectively as inputs.

[0016] The temperature acquisition circuit, the flow rate acquisition circuit, and the flow direction acquisition circuit are connected to the processing module as inputs.

[0017] Optionally, the differential pressure acquisition unit includes

[0018] a differential pressure flow probe for acquiring the pressure at the front end and the rear end of the baffle, and the baffle is installed in the train pipe.

[0019] Optionally, the flow transmitter further includes a compensation module connected to the processing module.

[0020] The compensation module includes a temperature compensation unit, an error compensation unit, and a zero point compensation unit.

[0021] The flow transmitter of the present utility model uses two types of flow monitoring, differential pressure type and thermal mass type, to acquire the current flow value. When the flow rate of compressed air in the pipe is low, the thermal mass method is used to calculate the current flow value; when the flow rate of compressed air is high, the differential pressure method is used to calculate the current flow value.

[0022] When the flow rate of compressed air in the pipe is low, the thermal mass monitoring principle is adopted, that is, when the fluid flows through a heating object (probe), the amount of heat dissipation of the heating object is in a certain proportional relationship with the flow rate of the fluid. This flow transmitter consists of two standard-grade thermal resistors (RTDs). One is used as a heat source, and the other is used to measure the fluid temperature. When the fluid flows, the temperature difference between the two is non-linearly related to the flow rate. Then, through microelectronic control technology for compensation, this relationship is converted into a linear output for measuring the flow signal. At the same time, the flow transmitter probe outputs a flow direction signal on another path.

[0023] When the flow rate of compressed air in the pipe is large, the differential pressure type flow monitoring principle is adopted, that is, a baffle is placed in the pipe, and the differential pressure formed between the dynamic pressure upstream of the baffle and the static pressure downstream is measured using the Pitot tube measurement principle. Combining the inner diameter of the pipe and the pipe pressure, the current flow rate of compressed air in the pipe is calculated through microelectronic technology. This method has good repeatability and is less affected by temperature.

[0024] The utility model has the following advantages:

[0025] The flow transmitter of the utility model combines the advantages of differential pressure type and thermal mass flow monitoring. It adopts the thermal mass calculation method for monitoring at low flow rates and the differential pressure calculation method at high flow rates, so that it combines all the advantages of wide range, high precision, fast response, direction recognition and other two flow monitoring methods.

[0026] The flow transmitter can solve the problem of slow response time of traditional transmitters, and can quickly collect the instantaneous flow rate and flow direction (millisecond level) of the compressed air in the train pipe when the train pipe of the braking system of a 20,000-ton heavy-haul train is abnormally emergently braked, which is convenient for judging the part causing the emergency braking of the heavy-haul train.

[0027] Since the flow monitoring of the braking system of heavy-haul trains has very harsh use conditions, which are mainly reflected in that the range should be as wide as possible (the flow peak can reach 60 L / s at the beginning of charging and exhausting, while it is as small as 1 L / s at the end), and high requirements are also placed on accuracy and repeatability. The utility model combines thermal mass and differential pressure type, which can enable the flow transmitter to have an error ≤ 2%F.S in the required wide range of -60 to 60 L / s, and at the same time has the function of direction monitoring. Description of the Drawings

[0028] Figure 1 It is the systematic structure block diagram of the flow transmitter of the utility model. Detailed Embodiment

[0029] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and should not be construed as a limitation of the present application.

[0030] In this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0031] As described in the background art,

[0032] There are many types of flow transmitters commonly used in the industrial field. However, in terms of principle, there are only two types of flow transmitters that are currently truly mass-produced and used in the rail transit air duct system. One is the differential pressure type flow transmitter, and the other is the thermal mass flow transmitter.

[0033] Among them, the differential pressure type flow transmitter has a fast response time and can detect the flow rate of 10-100% of the full scale, but it cannot identify the micro flow rate.

[0034] Among them, although the thermal flow transmitter can monitor the micro flow rate, its response time is long, and it is greatly affected by temperature, and a separate temperature compensation algorithm is required.

[0035] When the train pipe of the heavy-haul train braking system has an abnormal emergency braking, a rapid response to the instantaneous flow rate and flow direction of the compressed air in the train pipe is required. However, both of the above two flow monitoring devices have their own limitations in the train braking system and cannot achieve a rapid response.

[0036] For the above reasons, this embodiment provides a composite flow transmitter, as Figure 1 shown. This flow transmitter includes

[0037] a collection module, which is used to collect the current flow rate, flow direction and pressure of the compressed air in the train pipe;

[0038] a processing module, which is connected to the collection module and is used to process the data collected by the collection module; and

[0039] an output module, which is connected to the processing module and is used to convert the data processed by the data processing module into a current signal and output it;

[0040] The collection module includes:

[0041] a thermal mass collection unit, which is used to collect the flow rate and flow direction of the compressed air in the train pipe at low flow rates, and

[0042] a differential pressure collection unit, which is used to collect the pressure of the compressed air in the train pipe at high flow rates.

[0043] Furthermore, the thermal mass collection unit includes a thermal mass flow probe, a temperature collection circuit, a flow rate collection circuit and a flow direction collection circuit.

[0044] The thermal mass flow probe is connected to the flow rate collection circuit and the flow direction collection circuit respectively as inputs.

[0045] The temperature collection circuit, the flow rate collection circuit and the flow direction collection circuit are connected to the processing module as inputs.

[0046] Furthermore, the differential pressure collection unit includes

[0047] Differential pressure flow probe, used for collecting the pressures at the front end and the rear end of the baffle, and the baffle is installed in the train pipe.

[0048] By combining the thermal mass flow probe and the differential pressure flow probe, the above technical features can collect and calculate the current flow rate of the compressed air in the pipe in real time. Through comprehensive calculation by the processor and various precision compensations, the output module (which can be a DA chip) outputs a DC4-20mA current signal, corresponding to the current flow rate of -60 to +60 L / s in the pipe (the ± sign represents the flow direction); the above technical features can solve the problem of slow response time of traditional transmitters, and can realize the rapid collection of the instantaneous flow rate and flow direction (in milliseconds) of the compressed air in the train pipe when the train pipe of the braking system of a 20,000-ton heavy-haul train has an abnormal emergency brake, which is convenient for judging the part that causes the emergency brake of the heavy-haul train.

[0049] In order to improve the output accuracy of the sensor and the rapid conversion of the compressed air flow direction, in one embodiment, the flow transmitter further includes a compensation module connected to the processing module, and the compensation module includes a temperature compensation unit, an error compensation unit, and a zero-point compensation unit.

[0050] Exemplarily, the processing module can adopt a 32-bit GD32F103C8T6 single-chip microcomputer as the core controller. This processor has a built-in 12-bit ADC for acquisition, and the maximum main frequency is 108MHz.

[0051] The processor comprehensively calculates the flow signals collected by the two sensor probes after AD conversion. The output results are distinguished according to working conditions such as zero point, low flow rate, and high flow rate. Among them, the low flow rate and flow direction monitoring adopt the output of the thermal mass flow, and the high flow rate and start-up time (flow response time) adopt the output of the differential pressure type flow.

[0052] Exemplarily, the output module is a DA circuit. This part of the circuit converts the digital signal output by the processor into an analog signal and outputs a DC4mA~20mA current signal, where DC12mA is the zero point, DC4-12mA corresponds to -60 to 0 L / s, and DC12-20mA corresponds to 0 to +60 L / s (± represents the flow direction).

[0053] Exemplarily, the thermal mass flow acquisition module converts the flow signal of the sensor probe (thermal mass flow probe) into a voltage signal of 1.3-1.9V and sends it to the on-chip AD peripheral of the processor. The flow direction acquisition circuit converts the flow direction signal of the sensor probe into high and low levels through a comparator and sends it to the I / O port of the processor, and at the same time obtains the temperature signal (thermocouple).

[0054] The differential pressure type flow acquisition module introduces the pressure of the front and rear ends of the baffle by the sensor. The pressure sensor chip converts the pressure at both ends of the baffle into a DC 0.5 - 4.75V voltage signal and inputs it into the processor for processing. The minimum response time of its pressure sensor is 1ms.

[0055] The main technical indicators of the flow transmitter of the present utility model are as follows:

[0056] Measuring medium: Compressed air.

[0057] Working pressure: ≤1000 kPa.

[0058] Detection accuracy: ≤±2%FS (25°C).

[0059] Response time: ≤100ms.

[0060] Power supply voltage: 24V DC ±30%.

[0061] Output signal: -60L / s to +60L / s corresponding to DC 4 - 20mA.

[0062] The present utility model is specially designed for the monitoring of the braking system of heavy - haul trains. It can monitor the flow rate and flow direction of compressed air in the train pipe in real - time. When abnormal states such as leakage and pipe pressure fluctuations occur, it can respond quickly and give early warnings. Moreover, when an emergency braking occurs, it can also roughly judge the location of the emergency through the fast response time (within 100ms) of the composite sensor, ensuring the safe and stable operation of heavy - haul trains.

[0063] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present utility model. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present utility model. Therefore, the present utility model will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A composite flow transmitter, characterized in that: including a collection module, configured to collect the current flow rate, flow direction, and pressure of the compressed air in the train pipe; a processing module; connected to the collection module, and configured to process the data collected by the collection module; and an output module; connected to the processing module, and configured to output the data processed by the data processing module after converting it into a current signal; the collection module includes: a thermal mass collection unit, configured to collect the flow rate and flow direction when the flow rate of the compressed air in the train pipe is low, and a differential pressure collection unit, configured to collect the pressure when the flow rate of the compressed air in the train pipe is high.

2. The compound flow transmitter according to claim 1, wherein: the thermal mass collection unit includes a thermal mass flow probe, a temperature collection circuit, a flow rate collection circuit, and a flow direction collection circuit, the thermal mass flow probe is respectively connected to the flow rate collection circuit and the flow direction collection circuit as an input; the temperature collection circuit, the flow rate collection circuit, and the flow direction collection circuit are connected to the processing module as inputs.

3. The composite flow transmitter according to claim 1, characterized in that: the differential pressure collection unit includes a differential pressure flow probe, configured to collect the pressures at the front end and the rear end of the baffle, and the baffle is installed in the train pipe.

4. The compound flow transmitter according to any one of claims 1-3, characterized in that: further includes a compensation module connected to the processing module, the compensation module includes a temperature compensation unit, an error compensation unit, and a zero point compensation unit.

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