CN109781193B - In-situ calibration method for turbine flowmeter applied to test site - Google Patents
In-situ calibration method for turbine flowmeter applied to test site Download PDFInfo
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- CN109781193B CN109781193B CN201811499757.4A CN201811499757A CN109781193B CN 109781193 B CN109781193 B CN 109781193B CN 201811499757 A CN201811499757 A CN 201811499757A CN 109781193 B CN109781193 B CN 109781193B
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Abstract
The invention relates to an in-situ calibration method of a turbine flowmeter applied to a test site, which solves the problems of deviation and serious influence of the existing flowmeter calibration methodThe accuracy of the test data. A turbine flowmeter in-situ calibration method applied to a test site comprises the following steps: step one, establishing a calibration system; step two, converting output signals of the mass flowmeter; step three, calculating the slope k of a measuring channel of the mass flowmeter; step four, determining a calibration point of a tapping test; step five, carrying out a liquid discharge test; step six, processing the on-site tapping data; removing abnormal points; step eight, three times of six-gear tapping test; calculating a field in-situ calibration coefficient of the turbine flowmeter; step ten, calculating the measurement uncertainty of the maximum measuring range of the mass flowmeter
Step eleven, calculating the measurement uncertainty u of the turbine flowmeterqAnd the turbine meter calibration is complete.
Description
Technical Field
The invention relates to a turbine flowmeter calibration method, in particular to an in-situ turbine flowmeter calibration method applied to a test site.
Background
In the test of the liquid rocket engine, the flow is a key parameter which must be accurately measured, and the flow is closely related to performance parameters of the engine such as specific impulse, mixing ratio and the like. In order to obtain the flow data of the whole engine test process and improve the reliability of obtaining the test data, the flow measurement is generally carried out by adopting a mode of installing a plurality of flowmeters in series. Before the flowmeter uses, need carry out the aqueous medium check-up in the laboratory, but at the in-service use in-process, there is certain difference in laboratory check-up environment, pipeline installation and the actual service environment, and the physical properties parameters such as density, viscosity, temperature of check-up medium and experimental medium have the difference in addition, adopt water check-up coefficient to handle experimental flow data, can have certain deviation. For example, in a large liquid oxygen kerosene engine test, three large-caliber normal-temperature turbine flowmeters are adopted for measuring kerosene flow, and the maximum difference value between the three turbine flowmeters is about 3kg/s from the measurement data of multiple tests, so that the accurate provision of the test data and the development progress of subsequent products are seriously influenced.
Disclosure of Invention
The invention aims to solve the problems that the existing flowmeter calibration method has deviation and seriously influences the accuracy of test data, and provides a flow in-situ calibration method applied to a test field environment.
The technical scheme of the invention is as follows:
a turbine flowmeter in-situ calibration method applied to a test site comprises the following steps:
step one, establishing a calibration system;
the calibration system comprises a mass flowmeter and at least one turbine flowmeter which are arranged on a pipeline in series;
step two, converting output signals of the mass flowmeter;
converting a current signal output by the mass flowmeter into a voltage signal by adopting a method of adding a standard resistor;
step three, calculating the slope k of a measuring channel of the mass flowmeter;
applying I across the standard resistor1、I2Current signals, respectively obtaining I1、I2Corresponding mass flowmeter measurement channel acquisition value U1、U2，U1、U2The corresponding standard values are respectively the zero point and the maximum measuring range M of the mass flowmeter, the slope k of a measuring channel of the mass flowmeter is obtained by using an endpoint method, and the calculation formula is as follows;
step four, determining a calibration point of a tapping test;
determining a plurality of tapping test calibration points according to the flow design value of the rated section of the engine test and the flow design value of the reduced working condition section;
step five, carrying out a liquid discharge test;
selecting the minimum tapping test calibration point to perform a tapping test according to the plurality of tapping test calibration points determined in the step four, and obtaining an acquisition voltage value U of a measuring channel of the mass flowmeter and an output frequency f of the turbine flowmeter in the tapping process;
step six, processing the on-site tapping data;
after the tapping test is finished, calculating the measurement data q of the mass flow meter according to the collected voltage value U of the measurement channel of the mass flow meterZ；
qZ＝kU
Removing abnormal points;
flow rate q of mass flowmeterZThe output frequency f of the turbine flowmeter is in a linear corresponding relation, and abnormal points which do not conform to the linear relation are removed;
step eight, performing a liquid discharge test;
carrying out tapping tests of other tapping test calibration points according to the plurality of tapping test calibration points determined in the fourth step, and processing on-site tapping data according to the sixth step and the seventh step;
calculating a field in-situ calibration coefficient of the turbine flowmeter;
by the formula
Calculating a field in-situ calibration slope b and a field in-situ calibration intercept a; wherein rho-liquid density, kg/dm3；
Calculating a measurement theoretical value q of the turbine flowmeter according to the obtained field in-situ check slope b and the field in-situ check intercept am；
qm＝ρ(bf+a) (2)
Calculating a theoretical measurement value q of a turbine flowmetermMeasurement data q of mass flowmeterZA difference Δ q of;
step ten, calculating the uncertainty of the maximum measuring range of the mass flowmeter
；
Calculating the uncertainty of the maximum range of the mass flowmeter according to the known uncertainty u% and the maximum range M of the mass flowmeter
；
Step eleven, calculating the measurement uncertainty u of the turbine flowmeterq；
Uncertainty based on maximum range of mass flow meter
Measured theoretical value q of turbine flowmetermMeasurement data q of mass flowmeterZMaximum difference Δ q ofmaxCalculating the measurement uncertainty u of the turbine flowmeterqThereby completing calibration of the turbine flowmeter;
further, the calibration points in the fourth step are respectively 50%, 60%, 70%, 80%, 100% and 110% of the rated section flow of the engine test.
The invention has the advantages that:
1. the invention adopts the high-accuracy mass flowmeter as a calibration standard, can accurately obtain the equal volume flow of a plurality of turbine flowmeters arranged on a pipeline by measuring the flow and the density of the mass flowmeter, obtains the on-site real medium calibration slope and intercept of the plurality of turbine flowmeters, and solves the problem of data deviation of the turbine flowmeters under the same reference condition.
2. The method adopts real media to carry out field calibration on the turbine flowmeter in a test field environment, and eliminates the adverse effect of the difference of the installation environment and the check media on the flow measurement. In addition, the real medium is adopted, so that the repeated recycling of the calibration medium is realized, and the financial resources and the cost are saved.
3. By the calibration method, the difference value between the three flowmeters is reduced to be within 0.5kg/s from the original 3kg/s, the difference value is very close to the design value, and the measurement uncertainty of each flowmeter is better than 0.5%.
4. In an engine test, the turbine flowmeter is calibrated by the method, the measured value of any flowmeter can be used for providing test data, and the flow measurement precision is greatly improved.
Drawings
FIG. 1 is a schematic diagram of an in-situ calibration system for a turbine flowmeter applied to a test site.
Reference numerals: 1-turbine flow meter, 2-mass flow meter.
Detailed Description
The technical scheme of the invention is clearly and completely described in the following with the accompanying drawings of the specification.
In order to improve the measurement accuracy of the performance parameters of the engine, a kerosene flow in-situ calibration system taking mass flow as a calibration standard is established in the field environment of an engine test, and a turbine flowmeter is calibrated by using a real medium, so that the measurement accuracy of the kerosene flow is improved.
The output value of the mass flowmeter is mass flow, the flow measurement of the mass flowmeter can be approximately considered to be not influenced by the physical parameters of the measured medium and the flow state in the pipe, and the mass flowmeter is high in precision and suitable for being used as a calibration standard of a normal-temperature turbine flowmeter. The method comprises the steps of discharging liquid through a real medium, carrying out field in-situ calibration on a plurality of turbine flowmeters arranged on a conventional propellant supply pipeline by using a mass flowmeter, and obtaining in-situ real medium check coefficients of the turbine flowmeters under the test environment condition, so that the mass flow of the propellant in the test process is obtained.
The in-situ calibration system of the turbine flowmeter applied to the test site is shown in fig. 1, the test system adopts a method of measuring three turbine flowmeters in series, and the installation position of the turbine flowmeter is kept unchanged during in-situ calibration on the site. In-situ calibration of a real medium on site is carried out, according to the mass conservation principle, the mass flow of a propellant flowing through a turbine flowmeter is equal to that of a propellant flowing through a mass flowmeter, in-situ real medium calibration is carried out on the turbine flowmeter through tapping data to obtain a check coefficient, and test run data is processed by adopting the coefficient, as shown in a formula (2) and a formula (3);
qz＝qm＝ρ(bf+a) (2)
in the formula: q. q.sz-measurement data of the mass flow meter, kg/s;
qm-theoretical value measured of the turbine flowmeter, kg/s;
b-on-site in-situ calibration slope, L/Hz;
a-field in-situ check intercept, L;
rho-liquid density, kg/dm3；
f, the output frequency value of the turbine flowmeter, Hz.
The invention provides an in-situ calibration method of a turbine flowmeter applied to a test site, which comprises the following steps:
step one, establishing a calibration system;
the calibration system comprises a mass flowmeter 2 and three turbine flowmeters 1 which are arranged on a pipeline in series;
step two, converting output signals of the mass flowmeter;
the output of the mass flow meter is 4 mA-20 mA current signal, the acquisition equipment can only acquire voltage signal, and the method of adding 200 ohm standard resistance is adopted to convert the output current signal I of the mass flow meter into a voltage signal U suitable for the acquisition system to acquire; the method comprises the following specific steps: connecting a four-core cable at the converter end of the mass flowmeter, wherein two cables are a positive power line and a negative power line, two cables are a positive signal line and a negative signal line, providing a +30V working power supply for the mass flowmeter through the positive power line and the negative power line, transmitting a current signal output by the mass flowmeter to the input end of the acquisition equipment through a transmission link through the positive signal line and the negative signal line, and additionally adding 200 ohm standard resistors at the signal input positive end and the negative end of the acquisition equipment;
step three, obtaining the slope k of a measuring channel of the mass flowmeter;
respectively applying I to standard resistors by using standard voltage source1＝4mA、I2Obtaining I as 20mA current signal1、I2Corresponding mass flowmeter measurement channel acquisition value U1、U2，U1、U2The corresponding standard values are respectively 0kg/s and the maximum measuring range of the mass flowmeter is 150kg/s, the flow measurement channel slope k of the mass flowmeter is obtained by using an endpoint method, and the calculation method is shown in a formula (4);
step four, determining a calibration point of a tapping test;
determining calibration points of a tapping test according to a kerosene flow value (110kg/s) of a rated section of an engine test and a kerosene flow design value (65kg/s) of a reduced-operating-condition section, wherein the calibration points are respectively 55kg/s (50%), 65kg/s (60%), 75kg/s (70%), 90kg/s (80%), 110kg/s (100%) and 120kg/s (110%), and six points are added, and the linearity of a flowmeter check equation in the whole measuring range and the accuracy of measured data can be improved by measuring a plurality of calibration points;
step five, carrying out a kerosene tapping test;
selecting a minimum tapping test calibration point of 55kg/s to perform a tapping test according to the plurality of tapping test calibration points determined in the fourth step, and recording an acquisition voltage value U of a measuring channel of the mass flowmeter and the output frequency f of the turbine flowmeter in the tapping process;
step six, processing the on-site tapping data;
after the tapping test is finished, processing tapping data; calculating the measurement data q of the mass flowmeter according to the collected voltage value U of the measurement channel of the mass flowmeterZ；
qZ＝kU
Removing abnormal points;
comparing the flow value q during data processing according to the formula (3)ZCorresponding relation with output frequency f of flowmeter, turbine flow meter is volume type sensor, flow qZIf the output frequency f is high, rejecting abnormal points if the corresponding relation of the flow and the frequency is abnormal;
step eight, three times of six-gear tapping test;
according to the plurality of tapping test calibration points determined in the fourth step, a complete cycle of six gears is formed from the flow rate of 55kg/s to the maximum flow rate of 120kg/s, and after each test is finished, data are processed according to the sixth step and the seventh step;
calculating a field in-situ calibration coefficient of the turbine flowmeter;
by the formula
Calculating a field in-situ calibration slope b and a field in-situ calibration intercept a; wherein rho-liquid density, kg/dm3；
Calculating a measurement theoretical value q of the turbine flowmeter according to the obtained field in-situ check slope b and the field in-situ check intercept am；
qm＝ρ(bf+a) (2)
Calculating a theoretical measurement value q of a turbine flowmetermMeasurement data q of mass flowmeterZA difference Δ q of;
step ten, evaluating uncertainty of maximum measuring range of mass flowmeter
；
Calculating the uncertainty of the maximum range of the mass flowmeter according to the uncertainty of 0.15% and the maximum range of 150kg/s of the mass flowmeter
；
Step eleven, calculating the measurement uncertainty u of the turbine flowmeterq；
Uncertainty of flow measurement based on mass flow meter
Measured theoretical value q of turbine flowmetermMeasurement data q of mass flowmeterZMaximum difference Δ q ofmaxRespectively calculating the uncertainty u of the flow measurement of the turbine flowmeter according to the formula (6)qThereby completing calibration of the turbine flowmeter;
according to the invention, the mass flowmeter is utilized, and the turbine flowmeter is subjected to field calibration in a test field environment, so that real performance data under the test condition of the turbine flowmeter is obtained, and further, accurate propellant flow is obtained. From the multiple engine test data, the measured value of the kerosene flow in the test process is consistent with the designed value. In a test field environment, the mass flow meter is used as a calibration standard, and the method can be widely applied to liquid rocket engine tests adopting conventional propellants.
Claims (2)
1. The in-situ calibration method of the turbine flowmeter applied to the test site is characterized by comprising the following steps of:
step one, establishing a calibration system;
the calibration system comprises a mass flowmeter and at least one turbine flowmeter which are arranged on a pipeline in series;
step two, converting output signals of the mass flowmeter;
converting a current signal output by the mass flowmeter into a voltage signal by adopting a method of adding a standard resistor;
step three, calculating the slope k of a measuring channel of the mass flowmeter;
applying I across the standard resistor1、I2Current signals, respectively obtaining I1、I2Corresponding mass flowmeter measurement channel acquisition value U1、U2，U1、U2The corresponding standard values are respectively the zero point and the maximum measuring range M of the mass flowmeter, the slope k of a measuring channel of the mass flowmeter is obtained by using an endpoint method, and the calculation formula is as follows;
step four, determining a calibration point of a tapping test;
determining a plurality of tapping test calibration points according to the flow design value of the rated section of the engine test and the flow design value of the reduced working condition section;
step five, carrying out a liquid discharge test;
selecting the minimum tapping test calibration point to perform a tapping test according to the plurality of tapping test calibration points determined in the step four, and obtaining an acquisition voltage value U of a measuring channel of the mass flowmeter and an output frequency f of the turbine flowmeter in the tapping process;
step six, processing the on-site tapping data;
after the tapping test is finished, calculating the measurement data q of the mass flow meter according to the collected voltage value U of the measurement channel of the mass flow meterZ；
qZ＝kU
Removing abnormal points;
flow rate q of mass flowmeterZThe output frequency f of the turbine flowmeter is in a linear corresponding relation, and abnormal points which do not conform to the linear relation are removed;
step eight, performing a liquid discharge test;
carrying out tapping tests of other tapping test calibration points according to the plurality of tapping test calibration points determined in the fourth step, and processing on-site tapping data according to the sixth step and the seventh step;
calculating a field in-situ calibration coefficient of the turbine flowmeter;
by the formula
Calculating a field in-situ calibration slope b and a field in-situ calibration intercept a; wherein rho-liquid density, kg/dm3；
Calculating a measurement theoretical value q of the turbine flowmeter according to the obtained field in-situ check slope b and the field in-situ check intercept am；
qm＝ρ(bf+a) (2)
Calculating a theoretical measurement value q of a turbine flowmetermMeasurement data q of mass flowmeterZA difference Δ q of;
step ten, calculating the uncertainty of the maximum measuring range of the mass flowmeter
Calculating the uncertainty of the maximum range of the mass flowmeter according to the known uncertainty u% and the maximum range M of the mass flowmeter
Step eleven, calculating the measurement uncertainty u of the turbine flowmeterq；
Uncertainty based on maximum range of mass flow meter
Theoretical measurement q of a turbine flowmetermMeasurement data q of mass flowmeterZMaximum difference Δ q ofmaxCalculating the measurement uncertainty u of the turbine flowmeterqThereby completing calibration of the turbine flowmeter;
2. the in-situ calibration method for the turbine flowmeter applied to the test field according to claim 1, characterized by comprising the following steps: the calibration points in the fourth step are respectively 50%, 60%, 70%, 80%, 100% and 110% of the rated section flow of the engine test.
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| CN113819981B (en) * | 2021-10-11 | 2024-01-12 | 西安航天动力试验技术研究所 | Kerosene flow uncertainty evaluation device and method for liquid oxygen kerosene engine test |
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| US4566307A (en) * | 1982-09-30 | 1986-01-28 | Electronic Flo-Meters, Inc. | Pipeline flow measurement proving system |
| JP2005017152A (en) * | 2003-06-27 | 2005-01-20 | Oval Corp | Flowmeter, flow rate calculation method, program and recording medium |
| US6996485B2 (en) * | 2004-06-18 | 2006-02-07 | Gilbarco Inc. | Nullification of measurement error, particularly within a dual turbine flow meter used in a fuel dispenser |
| CN202522295U (en) * | 2012-03-20 | 2012-11-07 | 西安航天动力试验技术研究所 | System for calibrating turbine flow meter under condition of large flow of low-temperature medium |
| CN203785748U (en) * | 2014-04-21 | 2014-08-20 | 北京航天试验技术研究所 | Circulating water flow calibration system for liquid-propellant rocket engine tests |
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