Flow rate metering method for spiral throttling element

Abstract

A flow rate metering method for a spiral throttling element. A spiral flow channel is provided inside the spiral throttling element. The method comprises: introducing a calibration medium into the spiral throttling element for calibration; acquiring several flow rates Qv, the diameter d of the spiral flow channel, the effective length L of the spiral flow channel, the pressure drop DP of a fluid flowing through the spiral flow channel, and a fluid density ρ; and discovering the relationship k=f(Qv, d, L, DP, ρ), and obtaining a calculation formula of the flow rate Qv. For spiral flow channels of different sizes, a calculation formula of the flow rate can be obtained by using a small amount of calibration, thereby avoiding the mismatch of the calculation formula of the flow rate when the size of a spiral flow channel changes; a general calculation formula of the flow rate suitable for spiral flow channels of various sizes can be further obtained, thereby avoiding calibration of spiral flow channels of different sizes, reducing calibration costs and shortening the delivery period; and the precision of flow rate metering is relatively good, and can meet basic metering requirements.

Description

Flow measurement method of spiral throttling piece Technical Field

[0001] The present invention relates to the field of fluid measurement, and in particular to a flow measurement method for a non-standard throttling channel. Background Art

[0002] To significantly reduce fluid pressure, researchers previously proposed a labyrinthine throttling and pressure-reducing device. This device uses a spiral flow channel to reduce the pressure of high-pressure fluids (medicines). The spiral channel has a circular cross-section and an overall threaded shape. Depending on the needs, the device can be a single channel or multiple channels arranged inside and outside the flow channel. The throttling and pressure-reducing device is typically integrated into a flow meter to measure the flow rate of the liquid.

[0003] The flow measurement method / formula of a flow meter varies depending on its type; even if they are both differential pressure flow meters (such as Venturi flow meters and orifice flow meters), their specific flow calculation formulas are different. These differences are well known to those skilled in the art and will not be described in detail.

[0004] When using spiral flow channels for pressure reduction and metering, known empirical formulas are no longer suitable. Later, researchers proposed a series of solutions for measuring flow in spiral flow channels. However, these solutions were based on fixed-size spiral channels (the diameter and length of the spiral channel were both fixed values), and the flow measurement formulas did not incorporate the spiral channel's dimensional parameters. When the spiral channel's dimensions (diameter and length) were adjusted according to market demand, the algorithms used in these solutions again experienced large metering errors.

[0005] There are two approaches to solving this problem: one is to develop a corresponding algorithm for each size of spiral flow channel, and the other is to incorporate the spiral flow channel's dimensional parameters into the flow measurement algorithm. It is expected that the solution formed by the second approach will have wider adaptability to flow measurement for spiral flow channels of various sizes in the future.

[0006] Summary of the Invention

[0007] The present invention first solves the basic problem of adaptively measuring the flow rate of a spiral flow channel as the spiral flow channel size changes. The main technical solutions adopted to solve this problem are:

[0008] A flow measurement method for a spiral throttling element, wherein a spiral flow channel is provided inside the spiral throttling element, and the spiral throttling element is further equipped with a differential pressure sensor, wherein the differential pressure sensor is used to detect the pressure drop DP before and after the fluid flows through the spiral flow channel;

[0009] The key is to include the following steps:

[0010] Step 1: introducing a calibration medium into the spiral throttling element for calibration to obtain a plurality of calibration arrays, wherein the same calibration array includes the flow rate Qv, pressure drop DP, and Reynolds number Re at the same time;

[0011] Step 2: Calculate the flow coefficient k of the calibration medium flowing through the spiral throttling element according to the following formula ①;

[0012] d and L are the diameter and equivalent length of the spiral flow channel respectively, and n and m are the exponents of the two;

[0013] DP is the pressure drop of the calibration medium before and after flowing through the spiral flow channel;

[0014] ρ is the density of the calibration medium;

[0015] The values ​​of the exponents n and m are unknown at the beginning and need to be assigned manually (usually based on experience). Then, guided by the clear k-Re relationship, the values ​​of the exponents n and m need to be continuously adjusted until a reliable k = f(Re) relationship is obtained.

[0016] Step 3: Calculate the flow rate Q of the fluid to be measured flowing through the spiral throttling element according to the following formula ②;

[0017] DP' is the pressure drop of the fluid to be measured before and after flowing through the spiral flow channel;

[0018] ρ` is the density of the fluid to be measured;

[0019] K is the flow coefficient of the fluid to be measured;

[0020] x1 and x2 are two segmentation values, which serve as segmentation values ​​for low Reynolds number, medium Reynolds number and high Reynolds number respectively;

[0021] a1, b1, a2, b2, and c are all fitting parameters, obtained by fitting the reliable k=f(Re) relationship in step 2;

[0022] Re is the Reynolds number of the fluid to be measured.

[0023] The difficulty of the above scheme lies in finding appropriate values ​​for n and m, which requires extensive data calculation and simulation. Since the credible k = f(Re) relationship is generally determined manually, there are many possible values ​​for n and m that can be ultimately chosen. Although the specific flow calculation parameters obtained by calibration and fitting for one spiral flow channel size may not be applicable to another size, the above scheme provides the same basic relationship. For other spiral flow channel sizes, the specific flow calculation parameters can be obtained by simply performing appropriate calibration. This is also beneficial for expanding the adaptability of flow measurement for different spiral flow channel sizes. Of course, the two segmented values ​​x1 and x2 are also manually specified.

[0024] On the basis of solving the above basic problems, in order to further adapt the flow measurement of spiral throttling pieces of different sizes, it is also necessary to solve the problem of the need for further calibration of spiral throttling pieces of unknown size. Furthermore, the present invention adopts the following technical solution to exempt the calibration of the flow calculation parameters of spiral throttling pieces of unknown size:

[0025] Changing the diameter d and / or the equivalent length L of the spiral flow channel, thereby changing the spiral flow channel to different characteristic dimensions;

[0026] Repeat steps 1 and 2 to obtain reliable k=f(Re) relationships under several different feature sizes;

[0027] Compare the normalization levels of k = f(Re) for different feature sizes and continue adjusting the values ​​of the exponents n and m until the k = f(Re) relationship for different sizes reaches a credible normalization level under the same set of n and m values; the normalization level is also determined manually;

[0028] Since each size of spiral flow channel corresponds to a credible k=f(Re) relationship, in order to facilitate the calculation of the flow coefficient K of the fluid to be measured in step three and improve the accuracy of the fitting structure; accordingly, in step three, the parameters a1, b1, a2, b2, and c are obtained by fitting the credible k-Re data corresponding to all spiral flow channels of different characteristic sizes in step two. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a schematic structural diagram of a flow meter equipped with a spiral throttling element;

[0030] FIG2 is a curve of a k=f(Re) relationship that is considered reliable for a spiral flow channel having a second characteristic size in a low Reynolds number range (Re<550);

[0031] FIG3 is a curve of a k=f(Re) relationship that is considered reliable for a spiral flow channel having a second characteristic size within a medium Reynolds number range (550≤Re<2853);

[0032] FIG4 is a curve of a k=f(Re) relationship that is considered reliable for a spiral flow channel having a second characteristic size in a high Reynolds number range (2853≤Re);

[0033] FIG5 is a curve of a k=f(Re) relationship that is considered reliable for a spiral flow channel having a third characteristic size in a low Reynolds number range (Re<550);

[0034] FIG6 is a curve of a k=f(Re) relationship that is considered reliable for a spiral flow channel having a third characteristic size in the medium Reynolds number range (550≤Re<2853);

[0035] Figure 7 shows the k-Re scatter plots for three sizes that achieve a credible normalization level;

[0036] FIG8 is a distribution diagram of the relative error Efs (%) between the back-calculated flow rate and the calibrated flow rate of the spiral flow channel having the first characteristic size;

[0037] FIG9 is a distribution diagram of the relative error Efs (%) between the back-calculated flow rate and the calibrated flow rate of the spiral flow channel having the second characteristic size;

[0038] FIG10 is a distribution diagram of the relative error Efs (%) between the back-calculated flow rate and the calibrated flow rate of the spiral flow channel having the third characteristic size;

[0039] FIG11 is a relative error distribution diagram between the fitted flow rate and the real flow rate of the spiral flow channel having the fourth characteristic size;

[0040] FIG12 is a relative error distribution diagram between the fitted flow rate and the real flow rate of the spiral flow channel having the fifth characteristic size;

[0041] FIG13 is a relative error distribution diagram between the fitted flow rate and the real flow rate of the spiral flow channel having the sixth characteristic dimension. DETAILED DESCRIPTION

[0042] A method for measuring flow rate of a spiral throttle, wherein a spiral flow channel is provided inside the spiral throttle, as shown in FIG1 . The spiral flow channel is arranged in a threaded shape on the spiral throttle, and is a through hole with a circular cross section. The spiral flow channel may be one or more. When there are multiple spiral flow channels, the multiple spiral flow channels are arranged in a structure in which the inner and outer parts are sequentially nested, and the center lines of all the spiral flow channels coincide. The spiral throttle is also equipped with a differential pressure sensor, which is used to detect the pressure drop DP before and after the fluid flows through the spiral flow channel.

[0043] The specific steps include:

[0044] Step 1: A calibration medium is introduced into the spiral throttling element for a certain period of time for calibration. During this period, relevant data is acquired / calculated once at a certain interval, thereby obtaining several calibration arrays. The same calibration array includes the flow rate Qv, pressure drop DP, and Reynolds number Re at the same time. The Reynolds number Re is calculated by measuring other relevant parameters during flow. The specific formula is the existing technology and will not be repeated here.

[0045] Step 2: Calculate the flow coefficient k of the calibration medium flowing through the spiral throttling element by using the following formula ①;

[0046] d is the diameter of the spiral flow channel;

[0047] L is the equivalent length of the spiral flow channel;

[0048] n and m are both exponents;

[0049] DP is the pressure drop of the calibration medium before and after flowing through the spiral flow channel;

[0050] ρ is the density of the calibration medium;

[0051] The above exponents n and m are initially unknown. Based on experience, any set of n and m values ​​can be given and substituted into formula ①. The values ​​of n and m need to be continuously revised. Specifically, the values ​​of n and m are adjusted with the goal of obtaining a clear k-Re relationship, that is, with the goal of obtaining a clear k-Re functional relationship, until a reliable k = f(Re) relationship is obtained. The so-called reliable k = f(Re) relationship is also artificially determined. When the change of k with Re is relatively regular within a certain interval or overall, it is considered that the n and m values ​​at this time make k-Re reach a reliable k = f(Re) relationship. A more specific method for determining a reliable k = f(Re) relationship is to adjust the n and m values ​​and calculate several flow coefficients k of the calibration medium under each set of n and m values. Then, k-Re curves are plotted separately and a relatively smooth and continuous k-Re curve is selected for fitting to obtain a reliable k = f(Re) relationship. The k = f(Re) relationship can be global or segmented.

[0052] Step 3: Calculate the flow rate Q of the fluid to be measured flowing through the spiral throttling element according to the following formula ②;

[0053] DP' is the pressure drop of the fluid to be measured before and after flowing through the spiral flow channel;

[0054] ρ` is the density of the fluid to be measured;

[0055] K is the flow coefficient of the fluid to be measured;

[0056] a1 and b1 are low Reynolds number fitting parameters, obtained by fitting the reliable k=f(Re) relationship in step 2;

[0057] a2 and b2 are the fitting parameters of the medium Reynolds number, which are obtained by fitting the reliable k=f(Re) relationship in step 2;

[0058] c is the high Reynolds number fitting constant, obtained by fitting the reliable k=f(Re) relationship in step 2;

[0059] Re is the Reynolds number of the fluid to be measured;

[0060] x1 is the segmented value of low Reynolds number and medium Reynolds number;

[0061] x2 is the segmented value for medium and high Reynolds numbers.

[0062] For the spiral flow channels of different sizes (different diameters d and / or equivalent lengths L), relevant parameters of the spiral flow channels of corresponding sizes can be obtained by performing appropriate calibration each time.

[0063] In order to further simplify or even eliminate the calibration process for spiral flow channels of different sizes, the following steps can be performed:

[0064] Changing the diameter d and / or the equivalent length L of the spiral flow channel, thereby changing the spiral flow channel to different characteristic dimensions;

[0065] Repeat steps 1 and 2 to obtain reliable k=f(Re) relationships under several different feature sizes;

[0066] Compare the normalization degrees of k=f(Re) of different feature sizes, and continue to adjust the values ​​of the exponents n and m until the k=f(Re) relationships of different sizes reach a credible normalization degree under the same set of n and m values; combined with a more specific method for identifying a credible k=f(Re) relationship described above, a credible normalization degree identification method is: draw k-Re curves of credible k=f(Re) relationships under different feature sizes respectively, observe and compare the overlap of the k-Re curves of different feature sizes; if the overlap of the k-Re curves of different feature sizes is not good, adjust the values ​​of the exponents n and m until a k-Re curve with a high degree of overlap is matched, thereby specifying that the k=f(Re) relationships of different sizes reach a credible normalization degree. The so-called credible normalization degree is also artificially identified.

[0067] Correspondingly, since multiple credible k=f(Re) relationships are generated in step two, there are several k-Re data at different sizes. In step three, the several k-Re data at different sizes are uniformly merged into a whole to fit the parameters a1, b1, a2, b2, and c in step three.

[0068] The above process of determining the indices n and m requires a large amount of calculations, and multiple observations and comparisons are required during the process, which is very time-consuming and labor-intensive. In order to guide the values ​​of the indices n and m, you can refer to the following scheme for adjustment:

[0069] Select any two spiral flow channels with different characteristic sizes, where the diameter of the spiral flow channel with the first characteristic size is d1 and the equivalent length is L1, and the diameter of the spiral flow channel with the second characteristic size is d2 and the equivalent length is L2;

[0070] Select several calibration arrays in the high Reynolds number range corresponding to two different characteristic sizes. According to experience, the flow coefficient k at high Reynolds numbers is likely to be constant. The relationship between Qv and (DP, ρ) is fitted according to the following formula ③:

[0071] K` is the coefficient that includes the characteristic dimensions of the spiral flow channel;

[0072] The coefficient obtained by fitting the spiral flow channel with the first characteristic size is K1`, which is a constant;

[0073] The coefficient obtained by fitting the spiral flow channel with the second characteristic size is K2`, which is a constant;

[0074] The values ​​of indexes n and m also satisfy the following formula ④;

[0075] In reality, there are many possible values ​​for n and m that satisfy Formula ④, and Formula ④ cannot directly calculate a unique value for n and m. However, it clarifies the relationship between nm, which will greatly reduce the number of adjustments to the n and m values, thereby reducing the calculation and comparison workload to a certain extent. After finding the values ​​of the exponents n and m according to the relationship in Formula ④, calibration verification can be performed using spiral flow channels of other different characteristic sizes, and the normalization degree can be observed and compared with the results of the first and second characteristic sizes. If the normalization degree is insufficient, the values ​​of the exponents n and m can be further adjusted within the above constraints until the k = f(Re) relationship of different sizes reaches a credible normalization degree and simultaneously meets the requirements of Formula ④.

[0076] Example 2:

[0077] Three spiral flow channels with different characteristic sizes are designed for calibration test. The sizes of the three spiral flow channels with different characteristic sizes are:

[0078] The spiral flow channel with the first characteristic size has a diameter d1 = 2 mm and an equivalent length L1 = 9056.22 mm;

[0079] The spiral flow channel with the second characteristic size has a diameter d2=3 mm and an equivalent length L2=4247.26 mm;

[0080] The spiral flow channel with the third characteristic size has a diameter d3 = 4 mm and an equivalent length L3 = 3101.21 mm;

[0081] According to the method of Example 1: as in step 1, appropriate calibration media are introduced into the spiral flow channels of the above three sizes respectively to obtain a number of calibration data. The Reynolds number span of the calibration data is 3-35000, and the total amount of data reaches hundreds of thousands. The following will further illustrate this embodiment with reference to the accompanying drawings.

[0082] Then calculate the flow coefficient k of the calibration medium according to the method of step 2. In the initial stage, a set of values ​​of n and m are given based on experience, and then they are continuously revised.

[0083] If the values ​​of n and m are determined for the three spiral flow channels of the above three sizes separately, since the reliable k=f(Re) relationship is artificial, there are many possible values ​​of n and m, and the values ​​of n and m for each size are also different. Take the spiral flow channel with the second and third characteristic sizes as an example:

[0084] A curve of a k=f(Re) relationship that is considered reliable and has a second characteristic dimension (d2=3 mm, L2=4247.26 mm) in the low Reynolds number range (Re<550) is shown in FIG2 , a curve in the medium Reynolds number range (550≤Re<2853) is shown in FIG3 , and a curve in the high Reynolds number range (Re≥2853) is shown in FIG4 ;

[0085] A curve of a k=f(Re) relationship that is considered reliable and has a third characteristic dimension (d3=4 mm, L3=3101.21 mm) in the low Reynolds number range (Re<550) is shown in FIG5 , and a curve in the medium Reynolds number range (550≤Re<2853) is shown in FIG6 ;

[0086] As can be seen from Figure 2-6, after selecting appropriate values ​​of n and m, within a certain range of Reynolds numbers, the relationship between the flow coefficient k and the Reynolds number Re is clear and unambiguous, and the k-Re curve is relatively smooth and coherent, which can be considered a reliable k=f(Re) relationship;

[0087] It should be noted that the n and m values ​​determined for the second characteristic size are different from the n and m values ​​determined for the third characteristic size, which leads to insufficient normalization of the two reliable k=f(Re). This deficiency can be seen by comparing Figures 2 and 5, and Figures 3 and 6.

[0088] When selecting the credible k=f(Re) relationship as described above, it can also be done by setting relevant constraints.

[0089] The situation of the spiral flow channel with the other two characteristic dimensions is similar to that of the spiral flow channel with the third characteristic dimension. Since the values ​​of n and m are determined separately for each characteristic dimension, the data and curves corresponding to each dimension cannot be exhaustive, and therefore they are not described here.

[0090] The following is a unified determination of n and m values ​​for the spiral flow channels of the above three characteristic sizes. This process needs to solve the problem that after determining n and m values ​​for spiral flow channels of different characteristic sizes separately, there are huge differences in the reliable k = f (Re) relationship for each size. The goal of this process is to seek a highly normalized reliable k = f (Re) relationship for each size.

[0091] First, the reliable k=f(Re) curves selected when determining the n and m values ​​of the spiral flow channels of the above three characteristic sizes are plotted in the same coordinate system, and the normalization degrees of k=f(Re) of different characteristic sizes are compared and observed. The normalization degree can be determined manually or by setting relevant constraints.

[0092] Two spiral flow channels with first and second characteristic dimensions are selected to assist in determining the values ​​of n and m. The flow coefficient of the spiral flow channel with the first characteristic dimension is k1, and the flow coefficient of the spiral flow channel with the second characteristic dimension is k2.

[0093] set up

[0094] set up

[0095] For a spiral flow channel with fixed characteristic dimensions, when Qv, Dp, and ρ are known, K1` and K2` can be obtained relatively easily. According to experience, the flow coefficient k at high Reynolds numbers is likely to be a constant, and accordingly, K1` and K2` are also constants, which makes it possible to calculate K1` and K2` and explore the relationship between nm.

[0096] According to formula ③, Qv-(DP, ρ) is fitted. The results show that under high Norman number, there is a good linear relationship between Qv-(DP, ρ). K1` and K2` can be considered as constants, specifically K1` = 0.56 and K2` = 2.59795. Therefore, the specific expression of formula ④ is:

[0097] With formula ④ as the constraint condition, the values ​​of the exponents n and m are adjusted several times until the k=f(Re) relationship of different sizes reaches a credible normalization degree under the same set of n and m values. At this time, an appropriate set of n=2.55 and m=0.66 is selected. At this time, the credible k=f(Re) curves of the spiral flow channel with the above three characteristic sizes are plotted in the same coordinate system as shown in Figure 7. Figure 7 is a grayscale image. Although the data points corresponding to each characteristic size cannot be directly seen, it does not affect the observation of the degree of overlap of the data points corresponding to the three characteristic sizes. It can be seen from Figure 7 that the three credible k=f(Re) curves have a high degree of overlap, and it is determined that a credible normalization degree has been reached at this time.

[0098] Finally, the flow rate Q of the fluid to be measured flowing through the spiral throttling element is calculated according to formula ②;

[0099] The k and Re data corresponding to the credible k=f(Re) relationship of the three spiral flow channels with the first, second, and third characteristic sizes when n=2.55 and m=0.66 are integrated. FIG7 shows that the k and Re data corresponding to the credible k=f(Re) relationship of the three characteristic sizes are overall coherent and smooth, but there are actually obvious inflection points locally. Therefore, it is possible to consider performing segmented fitting: setting the segment value x1 of low and medium Reynolds numbers to 319, setting the segment value x2 of medium and high Reynolds numbers to 2858, and fitting the parameters a1, b1, a2, b2, and c in step 3. The results are a1=0.005445, b1=0.009238, a2=0.007605, b2=0.02169, and c=0.03883, that is:

[0100] The relationship between the flow coefficient K and the Reynolds number Re is:

[0101] The partial calibration data (including density, pressure drop, Reynolds number, etc.) with the first, second, and third characteristic dimensions are considered as the data of the fluid to be measured, and are substituted into Formula ② to respectively reverse calculate the flow rate to verify the flow measurement accuracy. Specifically: the flow rates of the three spiral flow channels with the first, second, and third characteristic dimensions are reverse calculated respectively, and the relative error Efs (%) between the reverse calculated flow rate and the calibrated flow rate is calculated. The resulting relative error distribution is plotted and shown in Figures 8, 9, and 10. As can be seen from Figures 8, 9, and 10, for the three spiral flow channels with the first, second, and third characteristic dimensions, the relative error between the reverse calculated flow rate and the calibrated flow rate is relatively small, basically meeting the measurement accuracy requirements.

[0102] Example 3:

[0103] Furthermore, in order to verify whether the method of the present invention can eliminate the calibration process for spiral flow channels of other different sizes, and whether the formula obtained by the above method is applicable to the flow calculation of spiral flow channels of other different sizes, three more spiral flow channels with different characteristic sizes are designed for calibration tests. The sizes of the three spiral flow channels with different characteristic sizes are:

[0104] The spiral flow channel having the fourth characteristic dimension has a diameter d4=4 mm and an equivalent length L4=2459.83 mm;

[0105] The spiral flow channel with the fifth characteristic dimension has a diameter d5=4.5 mm and an equivalent length L5=2459.83 mm;

[0106] The spiral flow channel having the sixth characteristic dimension has a diameter d6=5 mm and an equivalent length L6=2459.83 mm;

[0107] According to the method of Example 1: as in step 1, a suitable calibration medium (white oil) is introduced into the spiral flow channels of the fourth, fifth and sixth characteristic sizes respectively to obtain several real-time calibration arrays (including real-time flow Q t , real-time Reynolds number Re t , real-time differential pressure DP t , Q t -Re t -DP t have a one-to-one correspondence).

[0108] Then, the fitting results of Example 2 are used to calculate the fitting flow rates of the spiral flow channels with the fourth, fifth and sixth characteristic sizes. Specifically, the real-time Reynolds number Re t Directly substitute into the following formulas:

[0109] Calculate several real-time flow coefficients K t ;Q t -Re t -DP t -K t There is a one-to-one correspondence.

[0110] The real-time flow coefficient K t Substituting into formula ② (where n is 2.55 and m is 0.66), several fitting flow rates are calculated.

[0111] The above process involves a large amount of data, and it is not easy to intuitively see the accuracy of flow measurement. The data itself will not be displayed in detail here.

[0112] Calculate the fitted flow and real-time flow Q tThe relative error (%) between them is plotted, and the relative error (%)-real-time traffic distribution diagram is plotted, as shown in Figures 11, 12, and 13.

[0113] As can be seen from Figures 11, 12, and 13, for the three spiral flow channels with the fourth, fifth, and sixth characteristic dimensions, the relative errors between the fitted flow rates and the real-time flow rates are relatively small, which can basically meet the measurement accuracy requirements.

[0114] The full range error (600 L / h) of the spiral flow channel with the fourth characteristic dimension is (-1.19%)-(+1.13%);

[0115] The full range error (900 L / h) of the spiral flow channel with the fifth characteristic dimension is (-5.75%)-(+1.61%);

[0116] The full range (1000 L / h) error of the spiral flow channel with the sixth characteristic dimension is (-5.33%)-(+2.5%);

[0117] This example shows whether the fitting result of Example 2 is applicable to the flow calculation of spiral flow channels of other different sizes, thereby illustrating whether the method of the present invention can eliminate the calibration process for spiral flow channels of other different sizes and has good applicability.

[0118] Beneficial effects: By adopting the technical solution of the present invention, firstly, a flow calculation formula can be obtained for spiral flow channels of different sizes by using a small amount of calibration, thereby avoiding the situation where the flow formula does not match when the spiral flow channel size changes; further, a flow calculation formula applicable to a variety of spiral flow channel sizes can be obtained, eliminating the need to calibrate spiral flow channels of different sizes, reducing calibration costs, and shortening delivery cycles; the flow measurement accuracy is good and can meet basic measurement requirements.

[0119] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention. Such changes fall within the scope of protection of the present invention.

Claims

1. A flow metering method for a spiral throttling device, wherein a spiral flow channel is provided inside the spiral throttling device, and the spiral throttling device is also equipped with a differential pressure sensor, and the differential pressure sensor is used to detect the pressure drop DP before and after the fluid flows through the spiral flow channel; Features The following steps are involved: Step 1: introducing a calibration medium into the spiral throttling element for calibration, and obtaining a plurality of calibration arrays, wherein the same calibration array includes the flow rate Qv, the pressure drop DP, and the Reynolds number Re at the same time; Step 2: Calculate the flow coefficient k of the calibration medium flowing through the spiral throttling element according to the following formula ①; d is the diameter of the spiral flow channel; L is the equivalent length of the spiral flow channel; n and m are both exponents; DP is the pressure drop of the calibration medium before and after flowing through the spiral flow channel; ρ is the density of the calibration medium; Guided by obtaining a clear k-Re relationship, adjust the values ​​of the exponents n and m until a reliable k=f(Re) relationship is obtained; Step 3: Calculate the flow rate Q of the fluid to be measured flowing through the spiral throttling element according to the following formula ②; DP' is the pressure drop of the fluid to be measured before and after it flows through the spiral flow channel; ρ` is the density of the fluid to be measured; K is the flow coefficient of the fluid to be measured; a1 and b1 are low Reynolds number fitting parameters, obtained by fitting the reliable k=f(Re) relationship in step 2; a2 and b2 are the medium Reynolds number fitting parameters, obtained by fitting the reliable k=f(Re) relationship in step 2; c is the high Reynolds number fitting constant, obtained by fitting the reliable k=f(Re) relationship in step 2; Re is the Reynolds number of the fluid to be measured; x1 is the segmented value of low Reynolds number and medium Reynolds number; x2 is the segmented value for medium and high Reynolds numbers.

2. The spiral throttling element flow measurement method according to claim 1, characterized in that: Changing the diameter d and / or the equivalent length L of the spiral flow channel, thereby changing the spiral flow channel to different characteristic dimensions; Repeat steps 1 and 2 to obtain reliable k=f(Re) relationships under several different feature sizes; Compare the normalization degree of k=f(Re) of different feature sizes, and continue to adjust the values ​​of exponents n and m until the k=f(Re) relationship of different sizes reaches a credible normalization degree under the same set of n and m values; In the step three, the parameters a1, b1, a2, b2, and c are obtained by fitting the reliable k-Re data at all different characteristic sizes in step two.

3. The spiral throttling element flow measurement method according to claim 2, characterized in that: In the step 2, the values ​​of the indexes n and m are adjusted, and several flow coefficients k of the calibration medium under each set of n and m values ​​are calculated. Then, k-Re curves are drawn respectively, and a relatively smooth and continuous k-Re curve is selected for fitting to obtain a reliable k=f(Re) relationship.

4. The spiral throttling element flow measurement method according to claim 3, characterized in that: The k-Re curves of reliable k=f(Re) relationships under different characteristic sizes are plotted respectively, the coincidence of the k-Re curves of different characteristic sizes is observed and compared, and the values ​​of the exponents n and m are adjusted until a k-Re curve with a high degree of coincidence is matched, thereby specifying the k=f(Re) relationship of different sizes to achieve a reliable normalized degree.

5. The spiral throttling element flow measurement method according to claim 2 or 4, characterized in that: In step 2, the value adjustment method of the indexes n and m is as follows: Select any spiral flow channels with two different characteristic sizes, the diameter of the spiral flow channel with the first characteristic size is d1, the equivalent length is L1, and the diameter of the spiral flow channel with the second characteristic size is d2, the equivalent length is L2; Select several calibration arrays of high Reynolds number intervals corresponding to two different characteristic sizes, and fit the relationship between Qv-(DP, ρ) according to the following formula ③: K` is the coefficient that includes the characteristic dimensions of the spiral flow channel; The coefficient obtained by fitting the spiral flow channel with the first characteristic size is K1`, which is a constant; The coefficient obtained by fitting the spiral flow channel with the second characteristic size is K2`, which is a constant; The values ​​of index n and m also satisfy the following formula ④;

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