CN110821850A - Centrifugal pump test data correction method - Google Patents

Abstract

The invention provides a centrifugal pump test data correction method which comprises the following steps of detecting and calculating lift H, power P and efficiency η parameters of a centrifugal pump at different flow rates Q, correcting formulas H (f), (Q), P (f), (Q) and η (f) (Q) obtained by a Polyfit function based on a least square method principle, correcting test data of the lift H, the power P and the efficiency η respectively by a method combining with an interpolation method, and correcting performance curves for the second time.

Description

Centrifugal pump test data correction method

Technical Field

The invention relates to the technical field of water pump tests, in particular to a method for correcting test data of a centrifugal pump.

Background

At present, a water pump performance test is an important link of water pump production, is an effective means for inspecting processing, manufacturing, assembling and performance quality of a water pump, and can play a key role in inspection and acceptance of pump products. An interpolation method is commonly adopted in the existing water pump performance test system to correct the error of pump test data, so that the performance curve of pump products is obtained. However, in some cases, the interpolation method corrects errors of pump test data, which results in poor accuracy, and thus the fitting data does not reach the standard.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a centrifugal pump test data correction method, which adopts a correction method combining a least square method and an interpolation method, reduces data errors in test tests, improves correction precision, and can ensure that the fitting degree has higher precision.

The present invention achieves the above-described object by the following technical means.

A method for fitting and correcting a performance curve of a centrifugal pump comprises the following steps:

detecting and collecting η parameters of the lift H, the power P and the efficiency of the centrifugal pump at different flow rates Q;

correcting detection parameters of the lift H, the power P and the efficiency η by adopting a method of combining a Polyfit function method and an interpolation method based on a least square method principle;

respectively establishing a Q-H curve, a Q-P curve and a Q- η curve according to the corrected parameters of the flow Q, the lift H, the power P and the efficiency η;

and fitting, correcting and outputting the performance curve.

Further, the test data is corrected, specifically:

calculating a correction value set y according to an n-order approximate expression obtained by a Polyfit function based on the principle of a least square method₁{h₁,p₁,η₁And y₂{h₂,p₂,η₂Calculating Q of two adjacent data points of the randomly selected target data point according to an interpolation method₂；

According to y₁{h₁,p₁,η₁And y₂{h₂,p₂,η₂Get the median value, calculate y_CorrectionA value;

respectively calculating an original data value y and a corrected value y_CorrectionRelative error values m, n, r;

and (3) judging: if the original data value y and the correction value y_CorrectionAnd (4) outputting the current correction data and correcting other data points when the relative error values m, n and r are all less than 5.5%. If the original data value y and the correction value y_CorrectionIf any value of the error values m, n and r is more than or equal to 5.5%, two adjacent data points of the target data point are randomly selected again, and the original data value y and the corrected value y are repeatedly calculated_CorrectionThe relative error values m, n, r and the judgment process.

Further, an n-order approximate expression obtained by a Polyfit function based on the principle of the least square method is adopted to correct and calculate the original test data, and the specific formula is as follows:

h(Q)＝-9e^-7Q³+0.0004Q²-0.1424Q+137.34

p(Q)＝-2e^-6Q³+0.001Q²-0.0019Q+60.84

η(Q)＝-4e^-9Q⁴+4e^-6Q³-0.0024Q²+0.6951Q+0.0515

the invention has the beneficial effects that: according to the centrifugal pump test data correction method, the correction method combining the least square method and the interpolation method is adopted, the possible measurement error of original data in test is eliminated, and the correction precision is improved.

Drawings

FIG. 1 is a flow chart of a method for correcting test data of a centrifugal pump according to the present invention;

FIG. 2 is a schematic diagram of the Q-H curve, Q-P curve, and Q- η curve fitting in an embodiment of the present invention.

Detailed Description

The invention will be further described with reference to the following figures and specific examples, but the scope of the invention is not limited thereto.

As shown in fig. 1, a method for fitting and correcting a performance curve of a centrifugal pump includes the following steps:

detecting and collecting η parameters of the lift H, the power P and the efficiency of the centrifugal pump at different flow rates Q;

selecting a target data point Q₁Respectively correcting detection parameters of the lift H, the power P and the efficiency η by adopting a method of combining a Polyfit function method based on a least square method principle and an interpolation method;

the approximate expression of the order n obtained by the Polyfit function based on the principle of the least square method is as follows:

h(Q)＝-9e^-7Q³+0.0004Q²-0.1424Q+137.34

p(Q)＝-2e^-6Q³+0.001Q²-0.0019Q+60.84

η(Q)＝-4e^-9Q⁴+4e^-6Q³-0.0024Q²+0.6951Q+0.0515

correcting the test data specifically as follows:

calculating a correction value set y according to an n-order approximate expression obtained by a Polyfit function based on the principle of a least square method₁{h₁,p₁,η₁And y₂{h₂,p₂,η₂Calculating Q of two adjacent data points of the randomly selected target data point according to an interpolation method₂；

According to y₁{h₁,p₁,η₁And y₂{h₂,p₂,η₂Get the median value, calculate y_CorrectionA value;

respectively calculating an original data value y and a corrected value y_CorrectionRelative error values m, n, r;

and (3) judging: if the original data value y and the correction value y_CorrectionAnd (4) outputting the current correction data and correcting other data points when the relative error values m, n and r are all less than 5.5%. If the original data value y and the correction value y_CorrectionIf any value of the error values m, n and r is more than or equal to 5.5%, two adjacent data points of the target data point are randomly selected again, and the original data value y and the corrected value y are repeatedly calculated_CorrectionThe relative error values m, n, r and the judgment process.

Respectively establishing a Q-H curve, a Q-P curve and a Q- η curve according to the corrected parameters of the flow Q, the lift H, the power P and the efficiency η;

and fitting, correcting and outputting the performance curve.

The following takes a centrifugal pump of a certain type as a specific embodiment.

The basic parameters of the centrifugal pump are as follows: flow rate Q290 m³H, head H102 m, speed n 1480r/min, specific speed n_s＝47.9。

The specific operation steps are as follows:

s01: test data were recorded. And operating the water pump test system, monitoring and acquiring test data under each working condition by using a flowmeter and a pressure sensor in the data acquisition module, converting the test data into electric signals and transmitting the electric signals to the test data correction module. The collected external characteristic data of a part of the centrifugal pump are shown in table 1.

TABLE 1 external characteristic data of centrifugal pumps

Flow rate Q (m)3/h)	Delivery lift (m)	Power (kW)	Efficiency (%)
				0	137.56	61.11931	0
104	124.42	68.53595	51.43
				152	120.46	77.62387	62.45
202	115.93	88.39608	72.17
				250	109.15	96.78278	76.8
372	83.92	111.89776	76

S02: and correcting the test measurement data. In the test data correction module, the set formula analyzes the test data points one by one.

As shown in fig. 2, the operation steps are as follows:

s02.1: randomly selecting an abscissa value Q of the target data point₁。Q₁∈[Q_min,Q_max]；

S02.2: for the target data point (Q)₁,H)、(Q₁,P)、(Q₁η) is analyzed, the correction is carried out according to the least square method, and the abscissa value Q of the point to be corrected is corrected₁H (Q), p (Q), and η (Q) are respectively substituted into h (Q), p (Q), and η (Q) to obtain h (Q) ═ h₁＝117.48，p(Q)＝p₁＝84.78，η(Q)＝η₁68.84 to obtain y₁{117.48，84.78，68.84}；

S02.3: the abscissa value Q of two data points adjacent to the point Q to be corrected_m152 and Q_n250 according to equation Q₂＝(Q_m+Q_n) /2, mixing Q₂H (Q), p (Q), η (Q) are respectively substituted into 201 to obtain h₂＝117.57、p₂＝84.62、η₂68.76 to obtain y₂{117.57，84.62、68.76}；

S02.4: it is substituted into the formula (y ═ y)₁+y₂')/2 to obtain a correction value y_Correction{117.53、84.7、68.8}；

S02.5: and calculating relative percentage error values m, n and r before and after data correction. If the relative error values m, n and r are less than 5.5%, entering S02.6;

s02.6: and correcting other data points, and repeatedly executing the step S02 until all the data points are corrected, and outputting corrected test data.

S03: and (5) fitting and correcting a performance curve.

S04: and (6) outputting the data. As shown in fig. 2.

The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.

Claims (3)

1. A centrifugal pump test data correction method is characterized by comprising the following steps:

detecting and collecting η parameters of the lift H, the power P and the efficiency of the centrifugal pump at different flow rates Q;

correcting detection parameters of the lift H, the power P and the efficiency η by adopting a method of combining a Polyfit function method and an interpolation method based on a least square method principle;

respectively establishing a Q-H curve, a Q-P curve and a Q- η curve according to the corrected parameters of the flow Q, the lift H, the power P and the efficiency η;

and fitting, correcting and outputting the performance curve.

2. A centrifugal pump test data correction method as described in claim 1, wherein correction value set y is calculated from an n-order approximation expression obtained from a Polyfit function based on the least square principle₁{h₁,p₁,η₁And y₂{h₂,p₂,η₂Calculating Q of two adjacent data points of the randomly selected target data point according to an interpolation method₂；

According to y₁{h₁,p₁,η₁And y₂{h₂,p₂,η₂Get the median value, calculate y_CorrectionA value;

respectively calculating an original data value y and a corrected value y_CorrectionRelative error values m, n, r;

and (3) judging: if the original data value y and the correction value y_CorrectionAnd (4) outputting the current correction data and correcting other data points when the relative error values m, n and r are all less than 5.5%. If the original data value y and the correction value y_CorrectionIf any value of the error values m, n and r is more than or equal to 5.5%, two adjacent data points of the target data point are randomly selected again, and the original data value y and the corrected value y are repeatedly calculated_CorrectionThe relative error values m, n, r and the judgment process.

3. A centrifugal pump test data correction method according to claim 2, characterized in that the approximate expression of order n obtained from the Polyfit function based on the least squares principle is as follows:

h(Q)＝-9e^-7Q³+0.0004Q²-0.1424Q+137.34

p(Q)＝-2e^-6Q³+0.001Q²-0.0019Q+60.84

η(Q)＝-4e^-9Q⁴+4e^-6Q³-0.0024Q²+0.6951Q+0.0515。

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