METERING METHOD BASED ON CONVERTED SLIP RATIO FITTING FOR WET NATURAL GAS

Abstract

A metering method based on converted slip ratio fitting for wet natural gas is provided. The method includes fitting relationships between a gas Froude number and Venturi differential pressure and Venturi pressure loss with known data to obtain a gas Froude number calculation formula; dividing the known data according to a size of the gas Froude number, and performing piecewise fitting to obtain a piecewise converted slip ratio calculation formula under different gas Froude numbers; performing fitting on the dryness fraction and the converted slip ratio calculation formula; and acquiring, on the basis of the gas Froude number calculation formula, the converted slip ratio calculation formula, an overrated factor calculation formula and a dryness fraction calculation formula, some necessary real-time data to calculate a real-time flow rate of the wet gas. The method avoids using a ray flow meter and has advantages that include accurate metering and no radioactive pollution.

Claims

1. A metering method based on converted slip ratio fitting for wet natural gas, being implemented according to the following steps: step 1, acquiring a fitting array, wherein the fitting array comprises some one-to-one corresponding data comprising a gas Froude number Frg, Venturi pressure loss PL, Venturi differential pressure DP.sub.1, a converted slip ratio SS, a dryness fraction X and an overrated factor OR; step 2, fitting relationships between the gas Froude number Frg and the Venturi pressure loss PL and Venturi differential pressure DP.sub.1 according to Formula (1) as follows: $\begin{array}{cc}\mathrm{Frg}=F\left({\mathrm{DP}}_3\right),\mathrm{wherein}& \mathrm{Formula}\left(1\right)\end{array}$ ${\mathrm{DP}}_3={\mathrm{DP}}_1-\mathrm{PL},$ and a gas Froude number calculation formula is obtained by means of fitting; step 3, setting a division range according to a data size of the gas Froude number Frg, and dividing the fitting array into three sections, namely a high Frg section, a medium Frg section and a low Frg section; fitting, according to the section to which the fitting array belongs, relationships between the converted slip ratio SS and the Venturi pressure loss PL and the Venturi differential pressure DP.sub.1 in sections, as shown in Formula group (2) as follows: $\begin{array}{cc}\{\begin{array}{cc}\mathrm{SS}=f_1\left(k\right),& \mathrm{Frg}>x_2;\\ \mathrm{SS}=f_2\left(k\right),& x_1\mathrm{Frg}{x}_2;\\ \mathrm{SS}=f_3\left(k\right),& \mathrm{Frg}<x_1;\end{array},& \mathrm{Form}ula\mathrm{group}\left(2\right)\end{array}$ wherein x.sub.1, x.sub.2 are both natural numbers, x.sub.1<x.sub.2, $k={\mathrm{DP}}_1/{\mathrm{DP}}_3,$ and a piecewise converted slip ratio calculation formula is obtained by means of fitting; step 4, fitting a relationship between the overrated factor OR and the converted slip ratio SS according to Formula (3) as follows: $\begin{array}{cc}\mathrm{OR}=f_4\left(SS\right),& \mathrm{Formula}\left(3\right)\end{array}$ thereby obtaining an overrated factor calculation formula; fitting a relationship between the dryness fraction X and the converted slip ratio SS according to Formula (4) as follows: $\begin{array}{cc}X=f_5\left(SS\right),& \mathrm{Formula}\left(4\right)\end{array}$ thereby obtaining a dryness fraction calculation formula; step 5, acquiring a calculation array of wet gas to be measured, wherein the calculation array comprises some one-to-one corresponding data comprising real-time Venturi pressure loss PL.sup.s, real-time Venturi differential pressure DP.sub.1.sup.s, and a real-time gas phase density .sub.g, a real-time k.sup.s value is calculated according to Formula (5) as follows: $\begin{array}{cc}{k}^s=\frac{{\mathrm{DP}}_1^s}{{\mathrm{DP}}_1^s-{\mathrm{PL}}^s},& \mathrm{Formula}\left(5\right)\end{array}$ and a real-time DP.sub.3.sup.s value is calculated according to Formula (6) as follows: $\begin{array}{cc}{\mathrm{DP}}_3^s={\mathrm{DP}}_1^s-{\mathrm{PL}}^s;& \mathrm{Formula}\left(6\right)\end{array}$ step 6, calculating a real-time overrated factor OR.sup.s and a real-time dryness fraction X.sup.s; plugging the real-time DP.sub.3.sup.s value into the gas Froude number calculation formula obtained in step 2 to obtain a real-time gas Froude number Frg.sup.s, comparing the three values of Frg.sup.s,x.sub.1 and x.sub.2, and determining the section to which the calculation array belongs by taking the division range set in step 3 as a standard; plugging the real-time k.sup.s value into the corresponding section in the piecewise converted slip ratio calculation formula obtained in step 3 to calculate and obtain a real-time converted slip ratio SS.sup.s; plugging the real-time converted slip ratio SS.sup.s into the overrated factor calculation formula obtained in step 4 to calculate and obtain a real-time overrated factor OR.sup.s; plugging the real-time converted slip ratio SS.sup.s into the dryness fraction calculation formula obtained in step 4 to calculate and obtain a real-time X.sup.s; step 7, calculating an overrated gas mass flow rate M.sub.tp according to Formula (7) as follows: $\begin{array}{cc}{M}_{\mathrm{tp}}={\mathrm{CEd}}^2\sqrt{D{P}_1^s*{}_g},& \mathrm{Formula}\left(7\right)\end{array}$ wherein C and E are both constants, and d represents a diameter of the throat of a Venturi; step 8, calculating a real-time gas phase mass flow rate M.sub.g of wet gas to be measured according to Formula (8) as follows: $\begin{array}{cc}{M}_g=M_{\mathrm{tp}}/{\mathrm{OR}}^s;& \mathrm{Formula}\left(8\right)\end{array}$ and step 9, calculating a real-time liquid phase mass flow rate M.sub.l of the wet gas to be measured according to Formula (9) as follows: $\begin{array}{cc}{M}_l=\frac{M_g\left(1-X^s\right)}{X^s}.& \mathrm{Formula}\left(9\right)\end{array}$

2. The metering method based on converted slip ratio fitting for wet natural gas according to claim 1, wherein in step 2, fitting is performed according to Formula (1) as follows: $\begin{array}{cc}\mathrm{Frg}=F\left({\mathrm{DP}}_3\right)=a_1*{\mathrm{DP}}_3^3+b_1*{\mathrm{DP}}_3^2+c_1*{\mathrm{DP}}_3+d_1,& \mathrm{Formula}\left(1\right)\end{array}$ a.sub.1, b.sub.1, c.sub.1, d.sub.1 are all natural numbers, and specific parameters are obtained by fitting the gas Froude number Frg, the Venturi pressure loss PL and the Venturi differential pressure DP.sub.1.

3. The metering method based on converted slip ratio fitting for wet natural gas according to claim 1, wherein in step 3, piecewise fitting is performed according to Formula group (2) as follows: $\begin{array}{cc}\{\begin{array}{cc}\mathrm{SS}=f_1\left(k\right)=a_2{k}^{b_2}+c_2,& \mathrm{Frg}>x_2;\\ \mathrm{SS}=f_2\left(k\right)=a_3{k}^{b_3}+c_3,& x_1\mathrm{Frg}{x}_2;\\ \mathrm{SS}=f_3\left(k\right)=a_4{e}^{b_{4}k}+a_5{e}^{b_{5}k},& \mathrm{Frg}<x_1;\end{array},& \mathrm{Form}ulagr\mathrm{oup}\left(2\right)\end{array}$ wherein a.sub.2,3,4,5, b.sub.2,3,4,5 and c.sub.2,3 are all natural numbers, and specific parameters are obtained by fitting the converted slip ratio SS, the Venturi pressure loss PL and the Venturi differential pressure DP.sub.1.

4. The metering method based on converted slip ratio fitting for wet natural gas according to claim 1, wherein in step 4, fitting is performed to obtain the overrated factor calculation formula according to Formula (3) as follows: $\begin{array}{cc}\mathrm{OR}=f_4\left(\mathrm{SS}\right)=a_6{\mathrm{SS}}^{b_6}+c_6,& \mathrm{Formula}\left(3\right)\end{array}$ a.sub.6, b.sub.6 and c.sub.6 are all natural numbers, and specific parameters are obtained by fitting the overrated factor OR and the converted slip ratio SS; and fitting is performed to obtain the dryness fraction calculation formula according to Formula (4) as follows: $\begin{array}{cc}X=f_5\left(\mathrm{SS}\right)=a_7{\mathrm{SS}}^{b_7}+c_7,& \mathrm{Formula}\left(4\right)\end{array}$ wherein a.sub.7, b.sub.7 and c.sub.7 are all natural numbers, and specific parameters are obtained by fitting the dryness fraction X and the converted slip ratio SS.

5. The metering method based on converted slip ratio fitting for wet natural gas according to claim 1, wherein in step 3, the division range is artificially set

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 is a schematic diagram of an internal structure of a Venturi tube;

[0042] FIG. 2 is a schematic diagram of pressure changes during flowing of wet gas in a Venturi tube;

[0043] FIG. 3 is a Frg-DP.sub.3 curve corresponding to a test case;

[0044] FIG. 4 is a SS-k curve during fitting of a high Frg section corresponding to a test case;

[0045] FIG. 5 is a SS-k curve during fitting of a medium Frg section corresponding to a test case;

[0046] FIG. 6 is a SS-k curve during fitting of a low Frg section corresponding to a test case;

[0047] FIG. 7 is a OR-SS curve obtained by means of fitting in a test case; and

[0048] FIG. 8 is a X-SS curve obtained by means of fitting in a test case.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] The present disclosure will be further described below with reference to the examples and the accompanying drawings.

Example 1

[0050] A metering method based on converted slip ratio fitting for wet natural gas is implemented according to the following steps: [0051] step 1, acquire a fitting array, where [0052] the fitting array includes some one-to-one corresponding data including a gas Froude number Frg, Venturi pressure loss PL, Venturi differential pressure DP.sub.1, a converted slip ratio SS, a dryness fraction X and an overrated factor OR.

[0053] Step 2, fit relationships between the gas Froude number Frg and the Venturi pressure loss PL and Venturi differential pressure DP.sub.1 according to Formula (1) as follows:

[00011]$\begin{array}{cc}\mathrm{Frg}=F\left({\mathrm{DP}}_3\right).& \mathrm{Formula}\left(1\right)\end{array}$

[0054] In the formula, DP.sub.3=DP.sub.1PL, and [0055] a gas Froude number calculation formula is obtained by means of fitting.

[0056] Step 3, set a division range according to a data size of the gas Froude number Frg, and divide the fitting array into three sections, namely a high Frg section, a medium Frg section and a low Frg section; and [0057] fit, according to the section to which the fitting array belongs, relationships between the converted slip ratio SS and the Venturi pressure loss PL and the Venturi differential pressure DP.sub.1 in sections, as shown in Formula group (2) as follows:

[00012]$\begin{array}{cc}\{\begin{array}{cc}\mathrm{SS}=f_1\left(k\right),& \mathrm{Frg}>x_2;\\ \mathrm{SS}=f_2\left(k\right),& x_1\mathrm{Frg}{x}_2;\\ \mathrm{SS}=f_3\left(k\right),& \mathrm{Frg}<x_2;\end{array}& \mathrm{Formula}\mathrm{group}\left(2\right)\end{array}$

[0058] In the formula group, [0059] x.sub.1, x.sub.2 are both natural numbers, x.sub.1<x.sub.2, and

[00013]$k={\mathrm{DP}}_1/{\mathrm{DP}}_3.$

[0060] A piecewise converted slip ratio calculation formula is obtained by means of fitting.

[0061] Step 4, fit a relationship between the overrated factor OR and the converted slip ratio SS according to Formula (3) as follows:

[00014]$\begin{array}{cc}\mathrm{OR}=f_4\left(\mathrm{SS}\right),& \mathrm{Formula}\left(3\right)\end{array}$ [0062] thereby obtaining an overrated factor calculation formula.

[0063] Fit a relationship between the dryness fraction X and the converted slip ratio SS according to Formula (4) as follows:

[00015]$\begin{array}{cc}X=f_5\left(\mathrm{SS}\right),& \mathrm{Formula}\left(4\right)\end{array}$ [0064] thereby obtaining a dryness fraction calculation formula.

[0065] Step 5, acquire a calculation array of wet gas to be measured, where the calculation array includes some one-to-one corresponding data including real-time Venturi pressure loss PL.sup.s, real-time Venturi differential pressure DP.sub.1.sup.s, and a real-time gas phase density .sub.g.

[0066] A real-time k.sup.s value is calculated according to Formula (5) as follows:

[00016]$\begin{array}{cc}{k}^s=\frac{{\mathrm{DP}}_1^s}{{\mathrm{DP}}_1^s-{\mathrm{PL}}^s}.& \mathrm{Formula}\left(5\right)\end{array}$

[0067] A real-time DP.sub.3.sup.s value is calculated according to Formula (6) as follows:

[00017]$\begin{array}{cc}{\mathrm{DP}}_3^s={\mathrm{DP}}_1^s-{\mathrm{PL}}^s.& \mathrm{Formula}\left(6\right)\end{array}$

[0068] Step 6, calculate a real-time overrated factor OR.sup.s and a real-time dryness fraction X.sup.s; [0069] plug the real-time DP.sub.3.sup.s value into the gas Froude number calculation formula obtained in step 2 to obtain a real-time gas Froude number Frg.sup.s, compare the three values of Frg.sup.s,x.sub.1 and x.sub.2, and determine the section to which the calculation array belongs by taking the division range set in step 3 as a standard; [0070] plug the real-time k.sup.s value into the corresponding section in the piecewise converted slip ratio calculation formula obtained in step 3 to calculate and obtain the real-time converted slip ratio SS.sup.s; [0071] plug the real-time converted slip ratio SS.sup.s into the overrated factor calculation formula obtained in step 4 to calculate and obtain a real-time overrated factor OR.sup.s; and [0072] plug the real-time converted slip ratio SS.sup.s into the dryness fraction calculation formula obtained in step 4 to calculate and obtain the real-time X.sup.s.

[0073] Step 7, calculate an overrated gas mass flow rate M.sub.tp according to Formula (7) as follows:

[00018]$\begin{array}{cc}{M}_{\mathrm{tp}}={\mathrm{CEd}}^2\sqrt{{\mathrm{DP}}_1^s*{}_g}.& \mathrm{Formula}\left(7\right)\end{array}$

[0074] In the formula, C and E are both constants, and d represents a diameter of the throat of a Venturi.

[0075] Step 8, calculate a real-time gas phase mass flow rate M.sub.g of wet gas to be measured according to Formula (8) as follows:

[00019]$\begin{array}{cc}{M}_g=M_{\mathrm{tp}}/{\mathrm{OR}}^s.& \mathrm{Formula}\left(8\right)\end{array}$

[0076] Step 9, calculate a real-time liquid phase mass flow rate M.sub.l of the wet gas to be measured according to Formula (9) as follows:

[00020]$\begin{array}{cc}{M}_l=\frac{M_g\left(1-X^s\right)}{X^s}.& \mathrm{Formula}\left(9\right)\end{array}$

Example 2

[0077] This example differs from Example 1 only in that in step 2, fitting is performed according to Formula (1) as follows:

[00021]$\begin{array}{cc}\mathrm{Frg}=F\left({\mathrm{DP}}_3\right)=a_1*{\mathrm{DP}}_3^3+b_1*{\mathrm{DP}}_3^2+c_1*{\mathrm{DP}}_3+d_1.& \mathrm{Formula}\left(1\right)\end{array}$

[0078] In the formula, a.sub.1, b.sub.1, c.sub.1, d.sub.1 are all natural numbers, and the calculation can be obtained by means fitting after some Frg and DP.sub.3 are plugged.

Example 3

[0079] This example differs from Example 1 only in that in step 3, piecewise fitting is performed according to Formula group (2) as follows:

[00022]$\begin{array}{cc}\{\begin{array}{cc}\mathrm{SS}=f_1\left(k\right)=a_2{k}^{b_2}+c_2,& \mathrm{Frg}>x_2;\\ \mathrm{SS}=f_2\left(k\right)=a_3{k}^{b_3}+c_3,& x_1\mathrm{Frg}{x}_2;\\ \mathrm{SS}=f_3\left(k\right)=a_4{k}^{b_{4}k}+a_5{e}^{b_{4}k},& \mathrm{Frg}<x_1;\end{array}.& \mathrm{Formula}\mathrm{group}\left(2\right)\end{array}$

[0080] In the formula group, a.sub.2, a.sub.3, a.sub.4, a.sub.5, b.sub.2, b.sub.3, b.sub.4, b.sub.5, c.sub.2, c.sub.3 are all natural numbers, and specific parameters can be obtained by fitting some data including the converted slip ratio SS, the Venturi pressure loss PL and the Venturi differential pressure DP.sub.1.

Example 4

[0081] This example differs from Example 1 only in that in step 4, fitting is performed to obtain an overrated factor calculation formula according to Formula (3) as follows:

[00023]$\begin{array}{cc}\mathrm{OR}=f_4(\mathrm{SS})=a_{6}S{S}^{b_6}+c_6.& \mathrm{Formula}\left(3\right)\end{array}$

[0082] In the formula, a.sub.6, b.sub.6 and c.sub.6 are all natural numbers which are obtained by fitting the overrated factor OR and the converted slip ratio SS.

[0083] Fitting is performed to obtain the dryness fraction calculation formula according to Formula (4) as follows:

[00024]$\begin{array}{cc}X=f_5\left(\mathrm{SS}\right)=a_7{\mathrm{SS}}^{b_7}+c_7.& \mathrm{Formula}\left(4\right)\end{array}$

[0084] In the formula, a.sub.7, b.sub.7 and c.sub.7 are all natural numbers which are obtained by fitting the dryness fraction X and the converted slip ratio SS.

Example 5

[0085] A metering method based on converted slip ratio fitting for wet natural gas is implemented according to the following steps: [0086] step 1, acquire a fitting array, where [0087] the fitting array includes some one-to-one corresponding data including a gas Froude number Frg, Venturi pressure loss PL, Venturi differential pressure DP.sub.1, a converted slip ratio SS, a dryness fraction X and an overrated factor OR.

[0088] Step 2, fit relationships between the gas Froude number Frg and the Venturi pressure loss PL and Venturi differential pressure DP.sub.1 according to Formula (1) as follows:

[00025]$\begin{array}{cc}\mathrm{Frg}=F\left({\mathrm{DP}}_3\right)=a_1*{\mathrm{DP}}_3^3+b_1*{\mathrm{DP}}_3^2+c_1*{\mathrm{DP}}_3+d_1.& \mathrm{Formula}\left(1\right)\end{array}$

[0089] In the formula, DP.sub.3=DP.sub.1PL, [0090] a.sub.1, b.sub.1, c.sub.1, d.sub.1 are all natural numbers, and specific parameters can be obtained by means fitting after some Frg and DP.sub.3 are plugged, [0091] thereby obtaining a gas Froude number calculation formula by means of fitting.

[0092] Step 3, set a division range according to a data size of the gas Froude number Frg, and divide the fitting array into three sections, namely a high Frg section, a medium Frg section and a low Frg section; and [0093] fit, according to the section to which the fitting array belongs, relationships between the converted slip ratio SS and the Venturi pressure loss PL and the Venturi differential pressure DP.sub.1 in sections, as shown in Formula group (2) as follows:

[00026]$\begin{array}{cc}\{\begin{array}{cc}\mathrm{SS}=f_1\left(k\right)=a_2{k}^{b_2}+c_2,& \mathrm{Frg}>x_2;\\ \mathrm{SS}=f_2\left(k\right)=a_3{k}^{b_3}+c_3,& x_1\mathrm{Frg}{x}_2;.\\ \mathrm{SS}=f_3\left(k\right)=a_4{e}^{b_{4}k}+a_5{e}^{b_{5}k},& \mathrm{Frg}<x_1;\end{array}& \mathrm{Formula}\mathrm{group}\left(2\right)\end{array}$ [0094] In the formula group, [0095] x.sub.1, x.sub.2 are both natural numbers, x.sub.1<x.sub.2, and

[00027]$k={\mathrm{DP}}_1/{\mathrm{DP}}_3.$ [0096] a.sub.2, a.sub.3, a.sub.4, a.sub.5, b.sub.2, b.sub.3, b.sub.4, b.sub.5, c.sub.2, c.sub.3 are all natural numbers, and specific parameters can be obtained by fitting some data including the converted slip ratio SS, the Venturi pressure loss PL and the Venturi differential pressure DP.sub.1, [0097] thereby obtaining a piecewise converted slip ratio calculation formula by means of fitting.

[0098] Supplementary description is made to step 3 with one example. For example, there are three fitting arrays as follows: [0099] the first fitting array includes: a gas Froude number Frg.sub.1, Venturi pressure loss PL.sub.1, Venturi differential pressure DP.sub.1,1 and a converted slip ratio SS.sub.1.

[0100] The second fitting array includes: a gas Froude number Frg.sub.2, Venturi pressure loss PL.sub.2, Venturi differential pressure DP.sub.1,2 and a converted slip ratio SS.sub.2.

[0101] The third fitting array includes: gas Froude number Frg.sub.3, Venturi pressure loss PL.sub.3, Venturi differential pressure DP.sub.1,3 and a converted slip ratio SS.sub.3.

[0102] After the division range of Frg is set:

[0103] For the first fitting array, Frg>x.sub.2, which belongs to a high Frg section range.

[0104] For the second fitting array, Frg x.sub.1, and Frgx.sub.2, which belongs to a medium Frg section range.

[0105] For the third fitting array, Frg<x.sub.1, which belongs to a low Frg section range.

[0106] Therefore, during fitting: [0107] the first fitting array should be fitted according to SS=f.sub.1(k)=a.sub.2k.sup.b.sup.2+c.sub.2, [0108] the second fitting array should be fitted according to SS=f.sub.2(k)=a.sub.3 k.sup.b.sup.3+c.sub.3, and [0109] the third fitting array should be fitted according to SS=f.sub.3(k)=a.sub.4e.sup.b.sup.4.sup.k+a.sub.5e.sup.b.sup.5.sup.k.

[0110] Certainly, during respective fitting of the three sections, enough data is required to so as to obtain the corresponding parameters.

[0111] Step 4, fit a relationship between the overrated factor OR and the converted slip ratio SS according to Formula (3) as follows:

[00028]$\begin{array}{cc}\mathrm{OR}=f_4\left(\mathrm{SS}\right)=a_6{\mathrm{SS}}^{b_6}+c_6.& \mathrm{Formula}\left(3\right)\end{array}$

[0112] In the formula, a.sub.6, b.sub.6 and c.sub.6 are all natural numbers, and specific parameters are obtained by fitting the overrated factor OR and the converted slip ratio SS, [0113] thereby obtaining an overrated factor calculation formula by means of fitting.

[0114] Fit a relationship between the dryness fraction X and the converted slip ratio SS according to Formula (4) as follows:

[00029]$\begin{array}{cc}X=f_5\left(\mathrm{SS}\right)=a_7{\mathrm{SS}}^{b_7}+c_7.& \mathrm{Formula}\left(4\right)\end{array}$

[0115] In the formula, a.sub.7, b.sub.7 and c.sub.7 are all natural numbers, and specific parameters are obtained by fitting the dryness fraction X and the converted slip ratio SS, thereby obtaining a dryness fraction calculation formula by means of fitting.

[0116] Step 5, acquire a calculation array of wet gas to be measured, where [0117] the calculation array includes some one-to-one corresponding data including real-time Venturi pressure loss PL.sup.s, real-time Venturi differential pressure DP.sub.1.sup.s, and a real-time gas phase density .sub.g.

[0118] A real-time k.sup.s value is calculated according to Formula (5) as follows:

[00030]$\begin{array}{cc}{k}^s=\frac{{\mathrm{DP}}_1^s}{{\mathrm{DP}}_1^s-{\mathrm{PL}}^s}.& \mathrm{Formula}\left(5\right)\end{array}$

[0119] A real-time DP.sub.3.sup.s value is calculated according to Formula (6) as follows:

[00031]$\begin{array}{cc}{\mathrm{DP}}_3^s={\mathrm{DP}}_1^s-{\mathrm{PL}}^s.& \mathrm{Formula}\left(6\right)\end{array}$

[0120] Step 6, calculate a real-time overrated factor OR.sup.s and a real-time dryness fraction X.sup.s.

[0121] Plug the real-time DP.sub.3.sup.s value into the gas Froude number calculation formula obtained in step 2 to obtain a real-time gas Froude number Frg.sup.s, compare the three values of Frg, x.sub.1 and x.sub.2, and determine the section to which the calculation array belongs by taking the division range set in step 3 as a standard.

[0122] Plug the real-time k.sup.s value into the corresponding section in the piecewise converted slip ratio calculation formula obtained in step 3 to calculate and obtain the real-time converted slip ratio SS.sup.s, where the specific situation are as follows: [0123] when Frg>x.sub.2, the calculation array belongs to the high Frg section range, and related data (k.sup.s) should be plugged into SS=f.sub.1(k)=a.sub.2 k.sup.b.sup.2+c.sub.2 to calculate the converted slip ratio (in this case, all parameters in the formula are known).

[0124] When Frgx.sub.1 and Frgx.sub.2, the calculation array belongs to the medium Frg section range, and the related data (k.sup.s) should be plugged into SS=f.sub.2(k)=a.sub.3 k.sup.b.sup.3+c.sub.3 to calculate the converted slip ratio (in this case, all parameters in the formula are known).

[0125] When Frg<x.sub.1, the calculation array belongs to the low Frg section range, and the related data (k.sup.s) should be brought into a.sub.4e.sup.b.sup.4.sup.k+a.sub.5e.sup.b.sup.5.sup.k to calculate the converted slip ratio (in this case, all parameters in the formula are known).

[0126] Plug the real-time converted slip ratio SS.sup.s obtained by means of the above steps into the overrated factor calculation formula obtained in step 4 to calculate and obtain a real-time overrated factor OR.sup.s.

[0127] Plug the real-time converted slip ratio SS.sup.s into the dryness fraction calculation formula obtained in step 4 to calculate and obtain the real-time dryness fraction X.sup.s.

[0128] Step 7, calculate an overrated gas mass flow rate M.sub.tp according to Formula (7) as follows:

[00032]$\begin{array}{cc}{M}_{\mathrm{tp}}={\mathrm{CEd}}^2\sqrt{{\mathrm{DP}}_1^s*{}_g}.& \mathrm{Formula}\left(7\right)\end{array}$

[0129] In the formula,

[00033]$$\begin{gathered} E=\frac{\sqrt{2}.Math.}{4\sqrt{1-{}^4}}. \\ =d/D. \end{gathered}$$ [0130] C represents a Venturi outflow coefficient, [0131] d represents a diameter of the throat of the Venturi, and [0132] D represents a diameter of a straight tube section of a Venturi inlet.

[0133] Step 8, calculate a real-time gas phase mass flow rate M.sub.g of wet gas to be measured according to Formula (8) as follows:

[00034]$\begin{array}{cc}{M}_g=M_{\mathrm{tp}}/{\mathrm{OR}}^s.& \mathrm{Formula}\left(8\right)\end{array}$

[0134] Step 9, calculate a real-time liquid phase mass flow rate M.sub.l of the wet gas to be measured according to Formula (9) as follows:

[00035]$\begin{array}{cc}{M}_1=\frac{M_g\left(1-X^s\right)}{X^s}.& \mathrm{Formula}\left(9\right)\end{array}$

Test Case:

[0135] A test is performed according to the method mentioned in Example 5.

1. Fitting Between Frg and DP.SUB.3

[0136] Fitting is performed on several gas Froude numbers Frg, Venturi pressure loss PL, Venturi differential pressure DP.sub.1, and DP.sub.3=DP.sub.1PL.

[0137] Several coordinate points (Frg, DP.sub.3) are obtained, which are distributed in a plane rectangular coordinate system as shown in FIG. 3. The relationship between Frg and DP.sub.3 by means of fitting is: [0138] Frg=5DP.sub.3.sup.30.002819DP.sub.3.sup.2+0.2341DP.sub.3+1.728+1.534e, the degree of fitting thereof is R.sup.2=0.996, and e is natural number e.

2. Piecewise Fitting

[0139] According to experience, it is set that x.sub.1=3.500 and x.sub.2=9.170, and [0140] the division standard for the high Frg section is Frg>9.170; [0141] the division standard for the medium Frg section is 3.500Frg9.170; and [0142] the division standard for the low Frg section is Frg<3.500.

[0143] Several coordinate points (SS, k) are obtained by means of calculation, and coordinate points (SS, k) of the high, medium and low Frg sections are distributed in the plane rectangular coordinate system, which are shown in FIG. 4, FIG. 5 and FIG. 6 respectively.

[0144] Piecewise fitting is performed on the coordinates (SS, k) of each section to obtain:

[00036]$\begin{array}{cc}\{\begin{array}{cc}\mathrm{SS}=1.509k^{-11.44}+26.73,& \mathrm{Frg}>x_2;\\ \mathrm{SS}=2.928k^{-9.465}+20.24,& x_1\mathrm{Frg}{x}_2;\\ \begin{array}{c}\mathrm{SS}=413.9e^{-0.8947k}+\\ 7.842*10^{16}{e}^{-39.15k},\end{array}& \mathrm{Frg}<x_1;\end{array}.& \mathrm{Form}ula\mathrm{group}\left(2\right)\end{array}$

[0145] The degrees of fitting, namely R.sup.2, of the above three formulas are 0.990, 0.996 and 0.853 respectively.

3. Fitting of Overrated Factor and Dryness Fraction Calculation Formulas

[0146] See FIG. 7 for a scatter diagram of some overrated factors OR and corresponding converted slip ratios SS. Fitting is performed to obtain: OR=f.sub.4(SS)=a.sub.6SS.sup.b.sup.6+c.sub.6=4.159SS.sup.0.8443+1.038, and the degree of fitting R.sup.2=0.997.

[0147] See FIG. 8 for a scatter diagram of some dryness fractions X and corresponding converted slip ratios SS. Fitting is performed to obtain: [0148] X=f.sub.5(SS)=a.sup.7SS.sup.b.sup.7+c.sub.7=2.152SS.sup.0.5501+1.059, and the degree of fitting R.sup.2=0.997.
4. Real-Time Data is Acquired, a Real-Time Converted Slip Ratio SS.sup.s, a Real-Time Overrated Factor OR.sup.s, [0149] a real-time dryness fraction X.sup.s and an overrated gas mass flow rate M.sub.tp calculated in sequence, and a real-time gas phase mass flow rate M.sub.g and a real-time liquid phase mass flow rate M.sub.l are obtained by means of calculation. Moreover, relative errors Err.sub.g and Err.sub.1 are calculated respectively with real-time gas and liquid phase mass flow rates as reference. See Tables 1-1, 1-2 and 1-3 for statistical results.

TABLE-US-00001 TABLE 1-1 Statistical table for real-time gas and liquid phase mass flow rates and relative errors (high Frg section) Testing point M .sub.g Err .sub.g M .sub.l Err .sub.l High Frg section TP40 26.145 1.00% 6.483 8.47% TP6 26.814 0.50% 0.229 61.45% TP27 27.254 0.34% 4.068 2.35% TP35 27.689 0.36% 5.901 6.66% TP57 29.574 4.99% 12.269 20.46% TP61 29.646 5.01% 12.301 20.69% TP11 28.383 0.82% 1.077 14.12% TP56 29.404 3.19% 12.149 15.07% TP51 29.196 1.41% 11.940 8.60% TP50 29.100 0.17% 11.696 3.35% TP47 29.292 1.50% 10.501 6.80% TP42 29.383 1.75% 9.595 10.53% TP41 29.671 1.64% 8.492 12.93% TP34 29.960 1.27% 7.641 13.10% TP30 30.252 1.01% 6.804 13.81% TP26 30.712 0.19% 5.345 10.82% TP22 31.021 0.23% 4.088 11.09% TP18 31.369 0.60% 2.780 8.73% TP17 31.611 0.76% 1.953 4.83% TP10 31.775 0.71% 1.581 6.65% TP5 32.029 0.92% 0.538 28.15%

TABLE-US-00002 TABLE 1-2 Statistical table for real-time gas and liquid phase mass flow rates and relative errors (medium Frg section) Testing point M .sub.g Err .sub.g M .sub.l Err .sub.l Medium Frg section TP71 13.598 21.97% 7.401 44.37% TP67 16.322 12.76% 8.883 33.82% TP59 14.194 3.71% 7.719 9.84% TP64 16.934 5.74% 9.215 21.35% TP62 16.305 0.46% 8.870 7.28% TP66 18.666 10.33% 10.157 30.39% TP7 17.073 0.03% 0.179 53.64% TP20 19.352 0.05% 1.552 1.62% TP32 19.736 1.55% 4.146 11.70% TP46 18.649 8.36% 8.978 45.84% TP28 21.365 0.32% 3.215 3.10% TP52 21.472 6.03% 11.180 23.88% TP16 23.774 0.31% 1.478 10.51% TP23 24.104 0.36% 2.937 8.55% TP58 25.596 2.99% 13.448 9.52%

TABLE-US-00003 TABLE 1-3 Statistical table for real-time gas and liquid phase mass flow rates and relative errors (low Frg section) Testing point M .sub.g Err .sub.g M .sub.l Err .sub.l Low Frg section TP72 5.460 23.81% 2.676 53.03% TP37 5.929 0.51% 1.322 4.30% TP33 6.049 1.00% 1.261 10.81% TP9 5.983 3.93% 0.383 170.24% TP69 7.895 23.80% 3.335 51.87% TP14 6.777 1.81% 0.612 51.36% TP21 6.856 1.47% 0.756 39.57% TP38 7.105 1.26% 1.538 5.96% TP44 7.155 1.65% 1.703 6.95% TP48 7.573 3.53% 2.196 17.12% TP54 7.888 5.37% 2.506 23.21% TP13 7.847 1.24% 0.507 38.43% TP25 8.771 1.82% 0.808 19.03%

[0150] It can be seen from Tables 1-1, 1-2 and 1-3, that the relative error between the gas phase mass flow rate calculated by using the method of Example 5 and a true value is relatively small, and the relative error fluctuation of the liquid phase mass flow rate is relatively large. However, for metering of the wet gas (high gas volume fraction), the stable gas phase mass flow rate with a smaller error has practical guiding significance.

[0151] Beneficial effects: fitting is performed with known data by using the method of the present disclosure to obtain the converted slip ratio calculation formula, the overrated factor calculation formula and the dryness fraction calculation formula in sequence. Then, virtual metering is performed in combination with pressure data measured by using a Venturi flow meter, gas density parameters of the wet gas, etc. to calculate flow data of the wet gas, and dependence on a ray flow meter is avoided. The advantages of accurate metering, small errors and no radioactive pollution are achieved.

[0152] Finally, it should be noted that the above description are merely preferred examples of the present disclosure. Under the inspiration of the present disclosure, those of ordinary skill in the art can make various similar representations without departing from the spirit and claims of the present disclosure, and such transformations fall within the protection scope of the present disclosure.