Profibus-dp ultrasonic flowmeter based on domestic communication chip and flow calculation method

Abstract

The application discloses a kind of flow calculation method of Profibus-DP ultrasonic flowmeter based on domestic communication chip in the technical field of automation instrument, comprising the following steps: step 1) according to fluid Reynolds number, flow field is divided into three states of laminar flow, turbulent flow and transition flow;Step 2) respectively based on the linear velocity distribution of fluid in pipe under the condition of laminar flow and turbulent flow is calculated, the linear velocity distribution formula under the condition of laminar flow and turbulent flow is corrected by introducing correction factor;For transition flow state, the linear velocity calculation formula of transition flow is derived using linear interpolation method;Step 3) the linear velocity distribution formula after correction is combined with time difference method, and the flow velocity calculation formula is obtained, high-precision flow measurement is realized, and the application not only improves the accuracy of flow measurement, but also greatly reduces the product cost.

Description

Technical Field

[0001] This invention relates to the field of automated instrumentation technology, and in particular to an ultrasonic flow meter and a flow calculation method. Background Technology

[0002] Flow meters are indispensable measuring tools in the industrial field, widely used in industries such as petroleum, chemical, metallurgy, and heating, to accurately measure the flow rate of fluids in pipelines. Ultrasonic flow meters, as a non-invasive flow measurement device, have become an important branch of the flow meter industry due to their significant advantages such as high measurement accuracy and no pressure loss.

[0003] However, traditional ultrasonic flow meters have limitations in flow velocity detection. Currently, most ultrasonic flow meters use a single time-of-flight method for flow velocity measurement. This method fails to fully consider the differences in linear velocity distribution of fluid under different flow field states (such as laminar, turbulent, and transitional flow), nor does it correct for the influence of different operating conditions on flow velocity detection. Therefore, the applicable operating conditions of traditional ultrasonic flow meters are relatively limited, and the measurement accuracy is insufficient to meet the needs of complex industrial environments.

[0004] In terms of communication technology, traditional industrial sites commonly use imported chips for Profibus-DP communication, such as products from foreign brands like Siemens. While these imported chips are reliable, their high cost limits the progress of industrial automation upgrades in China. Although domestic products already exist, there is still significant room for improvement in performance and cost control.

[0005] With the continuous growth of domestic industrial automation demand, there is an urgent need for an ultrasonic flow meter solution that can meet the high-precision measurement requirements under complex working conditions while reducing production costs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a Profibus-DP ultrasonic flow meter and flow calculation method based on domestically produced communication chips. Through innovative flow velocity detection algorithms and the application of domestically produced chips, it not only significantly improves the accuracy of flow measurement but also greatly reduces product costs, providing strong support for the upgrading and transformation of domestic industrial automation.

[0007] The objective of this invention is achieved as follows: a flow calculation method for a Profibus-DP ultrasonic flow meter based on a domestically produced communication chip, comprising the following steps:

[0008] Step 1) Based on the fluid Reynolds number, the flow field is divided into three states: laminar flow, turbulent flow, and transitional flow;

[0009] Step 2) Calculate the linear velocity distribution of the fluid in the pipe under laminar and turbulent conditions based on fluid mechanics formulas, respectively, and introduce correction factors to correct the linear velocity distribution formulas under laminar and turbulent conditions; for the transitional flow condition, the linear velocity calculation formula for the transitional flow is derived by linear interpolation.

[0010] Step 3) The modified linear velocity distribution formula is combined with the time difference method to derive the flow velocity calculation formula, thereby achieving high-precision flow measurement.

[0011] Furthermore, step 1) specifically includes:

[0012] The Reynolds number method is used to classify flow field characteristics. The Reynolds number is calculated using the following formula: u m Where is the centerline velocity, D is the pipe diameter, nu is the kinematic viscosity of the fluid, the Reynolds number is laminar when it is between 0 and 2000, usually transitional when it is between 2000 and 4000, and turbulent when it is above 4000.

[0013] Furthermore, step 2) specifically includes:

[0014] After determining the flow field state, calculate the linear velocity at different locations in the pipe using the velocity distribution formula:

[0015] The formula for linear velocity distribution in laminar flow is: ;

[0016] k t R is the correction factor for laminar flow velocity distribution, R is the pipe radius, and r represents the radial position, i.e., the distance from a point to the central axis.

[0017] The formula for linear velocity distribution in turbulent flow is: ;

[0018] k c This is a correction factor for the turbulent velocity distribution;

[0019] With the parameter n fixed, if the Reynolds number is known, the corresponding value of n can be calculated.

[0020] Speed ​​is handled using linear interpolation in transition flow states. .

[0021] Furthermore, the correction factor is determined through the following steps:

[0022] In both turbulent and laminar flow conditions, the fluid velocity under specific operating conditions is measured by weighing. The measured velocity values ​​are substituted into the calculation formula containing correction factors to solve for the correction factors in both turbulent and laminar flow conditions. The linear velocity distribution formula is then adjusted using the correction factors.

[0023] Furthermore, the methods for obtaining the correction factor specifically include:

[0024] a) Calculate one velocity each under laminar and turbulent conditions using the weighing method;

[0025] b) The correction factor added to the time difference method is derived by combining the flow velocity calculated from the weighing; specifically including:

[0026] One set of experimental data each for laminar and turbulent flow conditions was obtained using the weighing method. v1 is the velocity measured in turbulent flow, and v2 is the velocity measured in laminar flow. Substitute these two data points into... and The correction factor can be calculated from this. and Then, the correction factor k is calculated. c and k t c is the speed of sound. This is a correction factor for laminar flow. This is a correction factor for turbulent flow.

[0027] 6. A Profibus-DP ultrasonic flow meter based on a domestically produced communication chip, used to implement the flow calculation method described in claim 1 or 2, characterized in that it comprises:

[0028] The flow acquisition module uses a DN20 reflective pipe section and a 1MHz ultrasonic transducer to convert flow data into current pulse signals.

[0029] The time measurement module measures the time difference between the ultrasonic upstream and downstream flow using the TDC-DP22 time measurement chip and transmits the measurement results to the flow acquisition main control module.

[0030] The main control module for traffic acquisition uses an MSP430 microcontroller to receive data transmitted from the time metering module and calculate cumulative and instantaneous traffic data.

[0031] The Profibus-DP communication module uses a GD32 microcontroller as the main control chip to control the domestic communication chip APC3 and transmit Profibus-DP protocol data through a 485 transceiver.

[0032] The display module uses an OLED display screen to show cumulative and instantaneous flow data.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention uses the domestically produced APC3 communication chip to replace the imported chip, and uses the domestically produced 485 transceiver CA-IS3092W as the physical layer chip for transmission, which significantly reduces the cost of the communication module.

[0035] This invention classifies the flow field according to the Reynolds number and uses different linear velocity distribution formulas for different flow field states. Combined with correction factors and time difference methods, the flow meter of this invention can achieve high-precision measurement under various complex working conditions. Compared with the traditional single time difference method or piecewise linearization compensation method, it has higher measurement accuracy and a wider range of applications.

[0036] This invention uses domestically produced chips and communication modules, which not only reduces costs but also improves the product's self-controllability, meeting the needs of domestic industrial automation upgrading and transformation.

[0037] In summary, this invention solves the problem of insufficient measurement accuracy of traditional ultrasonic flow meters under complex working conditions through innovative flow calculation methods and optimized hardware design. At the same time, it realizes the localization of communication modules, which has significant economic and social benefits. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the ultrasonic flow meter in this invention.

[0040] Figure 2 This is a simulation diagram comparing the linear velocity distribution and other flow field states when the pipe inner diameter is 14mm and the Reynolds coefficient is 3480 (i.e., the transition flow state).

[0041] Figure 3 This is a schematic diagram of the algorithm for solving different fluid states using the ultrasonic flow meter of the present invention.

[0042] Figure 4 This is a general design structure diagram of the hardware of the present invention.

[0043] Figure 5 This is a hardware structure block diagram of the ultrasonic metering module of the present invention.

[0044] Figure 6 This is a block diagram of the overall design of the Profibus communication module of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1

[0047] like Figure 1 As shown, the principle of ultrasonic flowmeter and several parameters during velocity measurement indicate that the linear velocity of the fluid is different at different positions in the pipe, and the propagation direction and the angle between the axis are determined.

[0048] A flow calculation method for a Profibus-DP ultrasonic flow meter based on a domestically produced communication chip includes the following steps:

[0049] Step 1) Based on the fluid Reynolds number, the flow field is divided into three states: laminar flow, turbulent flow, and transitional flow;

[0050] like Figure 1 The Reynolds number classification method is used to classify flow field characteristics. The Reynolds number calculation formula is as follows: u m Where is the centerline velocity, D is the pipe diameter, nu is the kinematic viscosity of the fluid, the Reynolds number is laminar when it is between 0 and 2000, usually transitional when it is between 2000 and 4000, and turbulent when it is above 4000.

[0051] Step 2) Calculate the linear velocity distribution of the fluid in the pipe under laminar and turbulent flow conditions based on fluid mechanics formulas, respectively, and introduce correction factors to modify the linear velocity distribution formulas for laminar and turbulent flow conditions; for the transition flow condition, the linear velocity calculation formula for the transition flow is derived using linear interpolation; specifically:

[0052] After determining the flow field state, calculate the linear velocity at different locations in the pipe using the velocity distribution formula:

[0053] The formula for linear velocity distribution in laminar flow is: ;

[0054] k t R is the correction factor for laminar flow velocity distribution, R is the pipe radius, and r represents the radial position, i.e., the distance from a point to the central axis.

[0055] The formula for linear velocity distribution in turbulent flow is: ;

[0056] k c This is a correction factor for the turbulent velocity distribution;

[0057] With the parameter n fixed, if the Reynolds number is known (the value of the Reynolds number is obtained by consulting relevant geometric parameters of fluids and pipes from Nikolaiz's experimental data), then the corresponding value of n can be calculated.

[0058] Speed ​​is handled using linear interpolation in transition flow states. .

[0059] Furthermore, the correction factor is determined through the following steps:

[0060] In both turbulent and laminar flow conditions, the fluid velocity under specific operating conditions is measured by weighing. The measured velocity values ​​are substituted into the calculation formula containing correction factors to solve for the correction factors in both turbulent and laminar flow conditions. The linear velocity distribution formula is then adjusted using the correction factors.

[0061] Specifically, the method for obtaining the correction factor is as follows:

[0062] a) Calculate one velocity each under laminar and turbulent conditions using the weighing method;

[0063] b) The correction factor added to the time difference method is derived by combining the flow velocity calculated from the weighing.

[0064] Calculate laminar flow velocity c is the speed of sound. This is a correction factor for laminar flow.

[0065] Calculate turbulent flow velocity , This is a correction factor for turbulent flow;

[0066] When the fluid is in laminar flow, u=u c， In turbulent flow, u=u t , Substitute into the following time difference calculation formula: The formula for calculating laminar flow time difference can be derived as follows: , simplify ,because ,therefore Therefore, we conclude ,at this time Because errors may occur in the coefficients during the formula simplification process, a correction factor is introduced. Ultimately obtain The formula for calculating turbulent time difference is: in ,because Therefore, we can obtain in ,at this time Because errors may occur in the coefficients during the formula simplification process, a correction factor is introduced. Therefore, the velocity in turbulent flow Therefore, the coefficients α and β can be corrected using the correction factor k. c and k t Correction;

[0067] The correction factor can be calculated using the weighing method, yielding experimental data for both laminar and turbulent flow conditions. v1 is the velocity measured in turbulent flow, and v2 is the velocity measured in laminar flow. Substitute these two data points into... and The correction coefficients α and β can be calculated from this, and because the coefficients... and With correction factor k c and k t This is relevant, therefore the correction factor k can be derived. c and k t ;

[0068] The correction factor and coefficient values ​​can be obtained by calculating using the above method.

[0069] Step 3) The correction factor k obtained in Step 2 c k t Substituting α and β into the formulas for the velocity distribution of streamlines in the transition from turbulent to laminar flow. , , Combining time difference When in turbulent flow, u=u t In laminar flow, u=u c During transition flow, u=u. The time difference under different states is then substituted into the formula. The flow rate can then be determined, enabling high-precision flow measurement.

[0070] Example 2

[0071] like Figure 4 As shown, the Profibus-DP ultrasonic flow meter based on a domestically produced communication chip of this invention mainly consists of three parts: an ultrasonic metering module, a Profibus-DP communication module, and a display section. The ultrasonic metering module acquires flow data through the ultrasonic metering pipe section and then sends the data to the Profibus-DP communication module via a serial port. 2 The data is displayed on the OLED screen using the C method. After receiving the data, the Profibus-DP communication module converts the received data into Profibus-DP format and transmits it to the Profibus-DP bus via the 485 bus.

[0072] like Figure 5As shown, the hardware of the ultrasonic metering module mainly includes an LDO voltage regulator module, a time measurement module, an OLED display module, an MCU module, a peripheral expansion interface, and an ultrasonic transducer. The ultrasonic metering module is connected to the Profibus-DP communication module via the peripheral expansion interface.

[0073] like Figure 6 As shown, the linear voltage regulator circuit converts the 5V power supply to 3.3V, which then powers the microcontroller, communication ASIC, and 485 transceiver. Since the 485 transceiver requires both 3.3V and 5V, an auxiliary power supply circuit is designed to provide the 5V voltage. The microcontroller used is the domestically produced GD32F103RBT6 as the local slave user. The communication ASIC is an APC3, which acts as the FDL controller, controlled by the microcontroller, and also controls the CA-IS3092 485 transceiver as the physical layer chip, responsible for connecting the PROFIBUS-DP cable.

[0074] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for calculating the flow rate of a Profibus-DP ultrasonic flow meter based on a domestically produced communication chip, characterized in that, Includes the following steps: Step 1) Based on the fluid Reynolds number, the flow field is divided into three states: laminar flow, turbulent flow, and transitional flow; Step 2) Calculate the linear velocity distribution of the fluid in the pipe under laminar and turbulent conditions based on fluid mechanics formulas, respectively, and introduce correction factors to correct the linear velocity distribution formulas under laminar and turbulent conditions; for the transitional flow condition, the linear velocity calculation formula for the transitional flow is derived by linear interpolation. Step 3) The modified linear velocity distribution formula is combined with the time difference method to derive the flow velocity calculation formula, thereby achieving high-precision flow measurement; Step 2) specifically includes: After determining the flow field state, calculate the linear velocity at different locations in the pipe using the velocity distribution formula: The formula for linear velocity distribution in laminar flow is: ; k t R is the correction factor for laminar flow velocity distribution, R is the pipe radius, and r represents the radial position, i.e., the distance from a point to the central axis. The formula for linear velocity distribution in turbulent flow is: ; k c This is a correction factor for the turbulent velocity distribution; With the parameter n fixed, if the Reynolds number is known, the corresponding value of n can be calculated. Speed ​​is handled using linear interpolation in transition flow states. ; The correction factor is determined through the following steps: In both turbulent and laminar flow conditions, the fluid velocity under specific working conditions is measured by weighing method. The measured velocity values ​​are substituted into the calculation formula containing correction factors to solve for the correction factors in turbulent and laminar flow conditions respectively. The linear velocity distribution formula is then adjusted using the correction factors. The methods for obtaining the correction factor specifically include: a) Calculate one velocity each under laminar and turbulent conditions using the weighing method; b) The correction factor added to the time difference method is derived by combining the flow velocity calculated from the weighing; specifically including: One set of experimental data each for laminar and turbulent flow conditions was obtained using the weighing method. v1 is the velocity measured in turbulent flow, and v2 is the velocity measured in laminar flow. Substitute these two data points into... and The correction factor can be calculated from this. and Then, the correction factor k is calculated. c and k t c is the speed of sound. This is a correction factor for laminar flow. This is a correction factor for turbulent flow.

2. The flow calculation method of the Profibus-DP ultrasonic flow meter based on a domestically produced communication chip according to claim 1, characterized in that, Step 1) specifically includes: The Reynolds number method is used to classify flow field characteristics. The Reynolds number is calculated using the following formula: u m Where is the centerline velocity, D is the pipe diameter, nu is the kinematic viscosity of the fluid, the Reynolds number is laminar when it is between 0 and 2000, usually transitional when it is between 2000 and 4000, and turbulent when it is above 4000.

3. A Profibus-DP ultrasonic flow meter based on a domestically produced communication chip, used to implement the flow calculation method described in claim 1 or 2, characterized in that, include: The flow acquisition module uses a DN20 reflective pipe section and a 1MHz ultrasonic transducer to convert flow data into current pulse signals. The time measurement module measures the time difference between the ultrasonic upstream and downstream flow using the TDC-DP22 time measurement chip and transmits the measurement results to the flow acquisition main control module. The main control module for traffic acquisition uses an MSP430 microcontroller to receive data transmitted from the time metering module and calculate cumulative and instantaneous traffic data. The Profibus-DP communication module uses a GD32 microcontroller as the main control chip to control the domestic communication chip APC3 and transmit Profibus-DP protocol data through a 485 transceiver. The display module uses an OLED display screen to show cumulative and instantaneous flow data.

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