Mass flow measuring method and mass flow meter

Abstract

The invention relates to a mass flow measuring method and a mass flow meter. The mass flow measuring method comprises the following steps: measuring the temperature of a flow tube of the mass flow meter; compensating a preset initial zero time delay based on the measured temperature of the flow tube and the temperature compensation coefficient of the flow tube; the mass flow is calculated by measuring the time delay of fluid flowing through the flow tube; and compensating the calculated mass flow based on the compensated initial zero time delay to obtain a compensated mass flow. According to the mass flow measuring method and the mass flow meter, dynamic temperature compensation can be carried out on zero drift of the mass flow meter, and therefore the measuring precision is improved.

Description

Technical Field

[0001] The present invention relates to the field of industrial measurement, and more specifically, to a mass flow measurement method and a mass flow meter capable of performing dynamic temperature compensation on zero drift of the mass flow meter. Background Art

[0002] When a fluid flows in a rotating tube, it generates a force on the tube wall. This force was discovered by Coriolis in 1832 when he was studying turbines. It is referred to as the Coriolis force. The mass flowmeter is a flow measurement instrument that measures the mass flow in a pipeline based on the Coriolis force. It can directly measure the mass flow of the medium passing through the flowmeter.

[0003] The mass flow meter includes a sensor and a transmitter. There are two parallel measuring tubes inside the sensor, with a drive coil in the middle and detection coils at both ends. When the transmitter provides an excitation voltage to the drive coil, the measuring tube vibrates back and forth. The fluid medium of the industrial process flows through the measuring tube of the sensor, which will produce a Coriolis force effect on the measuring tube, causing the two measuring tubes to torsionally vibrate. The detection coils installed at both ends of the measuring tube will generate two sets of signals with different phases. The phase difference of the two signals is proportional to the mass flow rate of the fluid flowing through the sensor, so the mass flow rate flowing through the measuring tube can be calculated.

[0004] With the improvement of automation level, many production processes have put forward new requirements for flow measurement. Chemical reaction process is controlled by the quality (not volume) of raw materials. The heating and cooling effects of steam and air flow are also proportional to the mass flow. Strict control of product quality, accurate cost accounting, and fuel quantity control of aircraft and missiles also require accurate mass flow measurement results.

[0005] The zero point of a traditional mass flow meter is a fixed value. However, the actual zero point will drift due to various factors, and the change of flow tube temperature is one of the factors.

[0006] Therefore, a mass flowmeter and flow measurement method capable of performing real-time temperature compensation for zero drift are needed. Summary of the invention

[0007] A brief overview of the present invention is given below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to give certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0008] A main object of the present invention is to provide a mass flow measurement method, comprising: measuring the temperature of a flow tube of a mass flowmeter; compensating for a predetermined initial zero time delay based on the measured temperature of the flow tube and a temperature compensation coefficient of the flow tube; measuring the time delay of a fluid flowing through the flow tube to calculate the mass flow; and compensating the calculated mass flow based on the compensated initial zero time delay to obtain a compensated mass flow.

[0009] According to one embodiment, based on the linear relationship or multi-order nonlinear relationship between the actual zero-point time delay and the temperature of the flow tube, the flow tube temperature compensation coefficient is obtained by calibration at multiple temperature points.

[0010] According to another embodiment, the temperature of the flow tube is the temperature of the fluid in the flow tube.

[0011] According to another aspect of the present invention, there is provided a mass flow meter, comprising: a sensor, which measures the time delay of the fluid flowing through the sensor and the temperature of the flow tube; a transmitter, which receives the measurement result from the sensor to calculate the mass flow; a controller, which compensates for a predetermined initial zero time delay based on the temperature of the fluid tube and the fluid tube temperature compensation coefficient; and compensates the mass flow calculated by the transmitter based on the compensated initial zero time delay to obtain a compensated mass flow.

[0012] According to one embodiment, based on the linear relationship or multi-order nonlinear relationship between the actual zero-point time delay and the temperature of the flow tube, the flow tube temperature compensation coefficient is obtained by calibration at multiple temperature points.

[0013] According to another embodiment, the temperature of the flow tube is the temperature of the fluid in the flow tube.

[0014] According to the mass flow measurement method and mass flow meter of the present invention, dynamic temperature compensation can be performed on the zero drift of the mass flow meter, thereby reducing the zero drift caused by the temperature change of the fluid (flow tube) and improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other purposes, features and advantages of the present invention will be more easily understood by referring to the following description of the embodiments of the present invention in conjunction with the accompanying drawings. The components in the accompanying drawings are only for illustrating the principles of the present invention. In the accompanying drawings, the same or similar technical features or components will be represented by the same or similar reference numerals. In the accompanying drawings:

[0016] Figure 1 is the actual zero-point delay Δt zero-actual and the distribution diagram of flow tube temperature changing with time;

[0017] Figure 2 shows the actual zero-point delay Δt zero-actualThe linear relationship between the flow tube temperature and

[0018] Figure 3 A comparison diagram of the mass flow error of the flow tube under temperature change conditions before and after compensation is shown;

[0019] Figure 4 A flow chart showing an exemplary process of a flow measurement method for dynamically compensating zero drift according to an embodiment of the present invention;

[0020] Figure 5 is a block diagram showing an exemplary structure of a mass flow meter according to one example of the present invention. DETAILED DESCRIPTION

[0021] Embodiments of the present invention are described below with reference to the accompanying drawings. Elements and features described in one drawing or one embodiment of the present invention may be combined with elements and features shown in one or more other drawings or embodiments. It should be noted that for the purpose of clarity, the representation and description of components and processes that are not related to the present invention and are known to those of ordinary skill in the art are omitted in the drawings and descriptions.

[0022] The measurement principle of the mass flow meter is first explained below.

[0023] A mass flow meter is a flow measurement instrument that measures the mass flow in a pipe based on the Coriolis force. The flow calculation of a traditional mass flow meter is shown in the following equation (1):

[0024] Massflow=FCF*(Δt flow -Δt zero )*(1-FT*T T ) (1)

[0025] The meanings of the parameters in equation (1) are as follows:

[0026] Massflow: mass flow

[0027] FCF: Flow calibration factor

[0028] Δt flow : Fluid delay, that is, the duration of the fluid passing through the flow tube, in nanoseconds (nsec)

[0029] Δt zero :Initial zero delay

[0030] FT: Overall temperature compensation coefficient

[0031] T T : Flow tube temperature.

[0032] Usually, Δtzero It is the set value entered by the factory calibration or the customer after installation, but in fact Δt zero The flow tube temperature change is one of the factors that affect the flow tube. Figure 1 The experiments shown confirm this. Figure 1 Shows the actual zero time delay Δt zero-acmal The distribution diagram of flow tube temperature changing with time. As can be seen from the figure, the actual zero point delay Δt zero-actual It has a negative linear relationship with the temperature of the flow tube.

[0033] Figure 2 It shows that Δt zero-actual The linear relationship between the flow tube temperature and Δt zero-actual Perform a linear fit to obtain Figure 2 , the two are basically in a linear relationship.

[0034] pass Figure 1 and Figure 2 It can be found that the trends of the flow tube temperature and the actual zero-point delay Δtzero-actual changing with time are basically consistent.

[0035] The mass flowmeter of the present invention performs dynamic temperature compensation on the zero drift. Furthermore, the zero drift can be temperature compensated in real time according to the temperature change of the flow tube.

[0036] In the present invention, the initial zero point delay Δt of the mass flow meter zero is the function of the real-time temperature of the flow tube f(T T ). Then the flow calculation formula of the mass flow meter of the present invention is shown in the following equation (2):

[0037] Massflow=FCF*(Δt flow -f(T T ))*(1-FT*T T ) (2)

[0038] f(T T ) can have many forms, for example:

[0039] f(T T )=k*T T +b A)

[0040] f(T T )=Δt zero *(1-k*T T )

[0041] f(T T )=Δt zero +k*T T +b B)

[0042] f(T T )=k*(T T ) 2 +b*T T +c C)

[0043] f(T T )=Δt zero +k*(T T ) 2 +b*T T +c D)

[0044] f(T T )=a*ln(T T )+b......E)

[0045] Therefore, if the above formula A) is used, the following formula (3) can be used to calculate T T For Δt zero Perform real-time linear compensation:

[0046] Δt zero-dynamic =f(T T )=k*T T +b (3)

[0047] The meanings of the parameters in equation (3) are as follows:

[0048] Δt zero-dynamic : Zero delay after dynamic compensation

[0049] k, b: Flow tube temperature compensation coefficient corresponding to zero time delay

[0050] The values ​​of k and b can be obtained by Figure 2 It can be obtained by linear fitting as shown, or by zero-point calibration at two temperature points according to the following slope equation (4) and intercept equation (5):

[0051]

[0052] b=Δt zero1 -k*T T1 (5)

[0053] The meanings of the parameters in the above equation are as follows:

[0054] T T1 : Flow tube temperature at point 1

[0055] T T2 : Flow tube temperature at point 2

[0056] Δt zero1 : Zero point delay corresponding to the flow tube temperature at point 1

[0057] Δt zero2 : Zero point delay corresponding to the flow tube temperature at point 2

[0058] The mass flow rate obtained from the above equation is in the form of equation (6):

[0059] Massflow=FCF*(Δt flow -(k*T T +b))*(1-FT*T T ) (6)

[0060] Figure 3 The comparison diagram of the mass flow error of the flow tube under temperature change conditions before and after compensation is shown. The "X" represents the error of the flow calculated using the static zero point before compensation, where the static zero point used is 59.866 (nsec) obtained at about 20°C, and the "△" represents the error of the flow calculated using the dynamic zero point after compensation. It can be seen from the figure that the error after compensation is significantly smaller than the error before compensation.

[0061] The following describes how to calculate the flow tube temperature compensation coefficients k and b corresponding to the zero-point delay. Two zero-point experiments were conducted under two different tube temperature conditions, and the results are shown in the following table:

[0062]

[0063] Table 1: Zero point experiments at two different flow tube temperatures

[0064] Substituting the data in Table 1 into the above equations (4) and (5), we can calculate:

[0065] k=(56.823-59.976) / (39.90-19.77)=-0.1566

[0066] b=59.976-(-0.1566×19.77)=63.072

[0067] Then, the dynamic zero point derived from the above flow tube temperature compensation coefficient can be used to calculate the mass flow rate and mass flow rate error. In this case, the flow calibration coefficient FCF = 7406.5g / s / usec, and the overall temperature compensation coefficient FT = 4.31. According to the above equation (6):

[0068] Mass flow rate = 7406.5*(Δt flow -(-0.1566*T T +63.072))*(1-4.31*T T );

[0069] Error = (measured mass flow rate - reference mass flow rate) / (reference mass flow rate) * 100%)

[0070] as follows Figure 3 As shown, under the new temperature compensation zero point, all mass flow errors can be controlled within 0.2%.

[0071] According to the flow measurement method of the present invention, dynamic temperature compensation can be performed on the zero drift of the mass flow meter, thereby improving the measurement accuracy.

[0072] The above is based on the flow tube temperature and the actual zero point delay Δt zero-actual The linear relationship between (Formula A) is used as an example to illustrate. However, those skilled in the art will appreciate that the linear relationship between the flow tube temperature and the actual zero time delay Δt zero-actual The multi-order nonlinear relationship between them, such as the second-order nonlinear relationship or the third-order nonlinear relationship of formula C) and D), is used to obtain the flow tube temperature compensation coefficients k, b and c by calibration at multiple temperature points.

[0073] Figure 4 A flow chart showing an exemplary process of a flow measurement method 700 for dynamically temperature compensating for zero drift according to an embodiment of the present invention.

[0074] First, in step S702, the temperature of the flow tube of the mass flow meter is measured.

[0075] Next, in step S704, the predetermined initial zero time delay is compensated based on the measured temperature of the flow tube and the flow tube temperature compensation coefficient.

[0076] In step S706, the time delay of the fluid flowing through the flow tube is measured to calculate the mass flow rate.

[0077] Finally, in step S708, the calculated mass flow is compensated based on the compensated initial zero time delay to obtain a compensated mass flow.

[0078] According to the flow measurement method of the present invention, dynamic temperature compensation can be performed on the zero drift of the mass flow meter, thereby improving the measurement accuracy.

[0079] Figure 5 is a block diagram showing an exemplary structure of a mass flow meter 900 according to one embodiment of the present invention.

[0080] like Figure 5 As shown, mass flow meter 900 includes a transmitter 902 , a sensor 904 , and a controller 906 .

[0081] Transmitter 902 receives measurements from sensor 904 to calculate mass flow.

[0082] The sensor 904 measures the time delay of the fluid flowing through the sensor 904 and the temperature of the flow tube or the fluid in the flow tube.

[0083] The controller 906 compensates for the predetermined initial zero time delay based on the temperature of the flow tube or the fluid and the flow tube temperature compensation coefficient.

[0084] The controller 906 compensates the mass flow calculated by the transmitter 902 based on the compensated initial zero time delay to obtain a compensated mass flow.

[0085] In the above description of specific embodiments of the present invention, the features described and / or shown for one embodiment may be used in one or more other embodiments in the same or similar manner, combined with the features in other embodiments, or replace the features in other embodiments.

[0086] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0087] In addition, the method of the present invention is not limited to being executed in the time sequence described in the specification, and may also be executed in other time sequences, in parallel or independently. Therefore, the execution order of the method described in this specification does not limit the technical scope of the present invention.

[0088] Although the present invention and its advantages have been described above by the description of specific embodiments, it should be understood that various changes, substitutions and conversions can be made without exceeding the spirit and scope of the present invention defined by the appended claims. Moreover, the scope of the present invention is not limited to the specific embodiments of the process, equipment, means, method and steps described in the specification. It will be easily understood by those of ordinary skill in the art from the disclosure of the present invention that the process, equipment, means, method or step to be developed in the present and future that performs the function substantially the same as the corresponding embodiment herein or obtains substantially the same result as the corresponding embodiment herein can be used according to the present invention. Therefore, the appended claims are intended to include such processes, equipment, means, methods or steps within their scope.

Claims

1. A mass flow measurement method, comprising: Measuring the temperature of the flow tubes of mass flow meters; Compensating for a predetermined initial zero time delay based on the measured temperature of the flow tube and a flow tube temperature compensation coefficient; Measuring the time delay of the fluid flowing through the flow tube to calculate the mass flow rate; as well as The calculated mass flow is compensated based on the compensated initial zero time delay to obtain a compensated mass flow.

2. The mass flow measurement method according to claim 1, characterized in that: Based on the linear relationship or multi-order nonlinear relationship between the actual zero-point time delay and the temperature of the flow tube, the flow tube temperature compensation coefficient is obtained by calibration at multiple temperature points.

3. The mass flow measurement method according to claim 2, characterized in that: The flow tube temperature is the temperature of the fluid in the flow tube.

4. A mass flow meter, characterized in that: include: a sensor that measures a time delay of a fluid flowing through the sensor and a temperature of a flow tube; a transmitter that receives measurements from the sensor to calculate mass flow; A controller, the controller compensating for a predetermined initial zero time delay based on a temperature of the flow tube and a flow tube temperature compensation coefficient; And based on the compensated initial zero time delay, the mass flow calculated by the transmitter is compensated to obtain the compensated mass flow.

5. The mass flow meter according to claim 4, characterized in that Based on the linear relationship or multi-order nonlinear relationship between the actual zero-point time delay and the temperature of the flow tube, the flow tube temperature compensation coefficient is obtained by calibration at multiple temperature points.

6. The mass flow meter according to claim 5, characterized in that The flow tube temperature is the temperature of the fluid in the flow tube.

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