CN104019852A - Method for accurately testing feed water flow based on throttling element characteristic coefficient K - Google Patents
Method for accurately testing feed water flow based on throttling element characteristic coefficient K Download PDFInfo
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- CN104019852A CN104019852A CN201410218379.3A CN201410218379A CN104019852A CN 104019852 A CN104019852 A CN 104019852A CN 201410218379 A CN201410218379 A CN 201410218379A CN 104019852 A CN104019852 A CN 104019852A
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- throttling element
- characteristic coefficient
- element characteristic
- feedwater
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Abstract
The invention relates to the method for accurately testing feed water flow based on a throttling element characteristic coefficient K. The method is mainly characterized in that calculation is conducted through the simplified feed water flow formula (please see the instruction). By the adoption of the method for accurately testing feed water flow based on the throttling element characteristic coefficient K, flow errors generated by modeling and calculation can be eliminated to the maximum degree, the method is stable and reliable and can completely meet the thermal power generating unit adjustment and test requirements.
Description
Technical field
The present invention relates to a kind of method of testing of feedwater flow, be specifically related to a kind of feedwater flow method for accurate testing based on throttling element characteristic coefficient K.
Background technology
The feedwater flow of fired power generating unit is an important regulated variable in boiler drum level regulating loop, is also the important underlying parameter that Unit Economic index is calculated.The measuring and calculation method of fired power generating unit feedwater flow at present, for the ease of modeling and calculating fast, the influence factor of considering is less, most of fired power generating unit feedwater flow calculates maximum flow corresponding to maximum differential pressure that only adopts throttling element, adopt differential pressure evolution, and then carry out simple interpolation calculation, within the scope of the gamut of flow measurement, produce error in various degree thereby cause.Its computing formula is as follows:
In formula:
G
0-feedwater flow measured value t/h
Gmax-feedwater flow maximal value t/h
Δ p
0-throttling element differential pressure measurement value, kPa
Δ p
max-throttling element differential pressure maximal value, kPa.
Summary of the invention
The object of the invention is to overcome the defect of prior art, a kind of feedwater flow method for accurate testing based on throttling element characteristic coefficient K is provided, the method step is simple, and the feedwater flow calculating accurately and reliably.
For achieving the above object, the technical solution used in the present invention is:
Based on a feedwater flow method for accurate testing of throttling element characteristic coefficient K, it specifically comprises the steps:
Step 1 is measured specific operation down-off differential pressure value and fluid density;
Step 2 is measured step 1 the flow differential pressure value and the fluid density that obtain, brings formula 1 into and calculates:
（1）
In formula:
-flow differential pressure value, unit K pa;
-fluid density, the position kg/m of unit
3;
Q-feedwater flow, the t/h of unit;
K-throttling element characteristic coefficient.
Further, definite method of throttling element characteristic coefficient K is as follows:
By calculating and read correlation parameter, calculate throttling element characteristic coefficient K based on formula 2:
（2）
In formula:
D
0-throttling element opening diameter, m;
ε-expansibility factor; ε=1 in the time being water;
The ratio of β-throttling element aperture and inside diameter of straight pipe section (D), β=d/D;
C-efflux coefficient;
Re-Reynolds number, its computing formula is:
the flow velocity of-feedwater, unit: m/s;
the kinematic viscosity of-feedwater, unit: Pa.s.
Compared with prior art, the beneficial effect that the present invention obtains is:
Feedwater flow of the present invention only depends on three parameters of density of throttling element characteristic coefficient K, feedwater flow differential pressure and fluid, and these three parameters are easy to obtain accurately in actual computation, and throttling element characteristic coefficient K is determined value, relevant with throttling element, can be through once calculating and be widely used, pass through actual verification, there is minimum deviation in the feedwater flow drawing according to this model measurement and actual flow simultaneously.Farthest eliminate due to modeling and calculate the flow error producing, the feedwater flow method of testing that the present invention is based on throttling element characteristic coefficient K is reliable and stable, can meet the needs of fired power generating unit adjusting and experimental test completely.
Embodiment
Below in conjunction with specific embodiment 1, the present invention is described in more detail.
Embodiment 1
The mensuration of certain #1 of cogeneration plant unit feedwater flow, specific as follows:
First by according to test figure (in table 1) carry out the throttling element characteristic coefficient K value in discharge model that computational analysis must make new advances:
（2）
In formula:
D-throttling element opening diameter, m, d=0.186354m in the present embodiment;
ε-expansibility factor, ε=1 in the time being water;
The ratio of β-throttling element aperture and inside diameter of straight pipe section, β=d/D, β=0.6102 in the present embodiment;
C-efflux coefficient;
Re-Reynolds number, its computing formula is:
the flow velocity of-feedwater, unit: m/s;
the kinematic viscosity of-feedwater, unit: Pa.s;
Feedwater flow velocity can draw by flow rate calculation, the kinematic viscosity of feedwater can by feed water pressure and temperature calculate by (looking into the physical property table of water).
Calculating K is 1.318161.
Certain #1 of cogeneration plant unit feedwater flow of table 1 is measured raw data and K value result of calculation summary sheet
| Project | Unit | Operating mode one | Operating mode two | Operating mode three | Operating mode four | Operating mode five |
| Load | MW | 298.98 | 266.99 | 240.11 | 216.01 | 183.97 |
| Feedwater flow (CRT) | t/h | 863.04 | 788.03 | 721.43 | 613.20 | 513.81 |
| Feed pressure | MPa | 17.67 | 17.35 | 16.70 | 15.29 | 13.11 |
| Feed temperature | ℃ | 275.64 | 268.13 | 261.43 | 255.84 | 247.42 |
| Feedwater differential pressure | kPa | 42.54 | 35.47 | 29.72 | 21.47 | 15.08 |
| K | \ | 1.319166 | 1.318633 | 1.318204 | 1.31773 | 1.317074 |
| K mean value | \ | 1.318161 |
Then calculate five feedwater flows under operating mode by formula 1:
（1）
In formula: throttling element characteristic coefficient K=1.318161
-flow differential pressure value, unit K Pa
Ρ-fluid density, units/kg/m3
Q-feedwater flow, the t/h of unit.
The feedwater flow that this method of testing calculates the results are shown in Table 2
Table 2 feedwater flow contrast table
| Project | Unit | Operating mode 1 | Operating mode 2 | Operating mode 3 | Operating mode 4 | Operating mode 5 |
| Actual flow | t/h | 862.292 | 792.992 | 730.152 | 623.033 | 525.010 |
| K value calculated flow rate | t/h | 861.656 | 792.686 | 730.118 | 623.229 | 525.446 |
| CRT flow | t/h | 863.038 | 788.034 | 721.434 | 613.202 | 513.812 |
| K value error of calculation value | t/h | 0.6354 | 0.3051 | 0.0339 | -0.1965 | -0.4365 |
| CRT error | t/h | -0.7465 | 4.9577 | 8.71771 | 9.8301 | 11.1971 |
Calculate and find according to test figure, there is larger deviation in feedwater flow, be more than the result of calculation summary sheet of 5 operating modes, can find out: feedwater flow deviation, from-be reduced to-0.5 t/h～0.7t/h of 0.8t/h～12 t/h, has improved the precision that feedwater flow calculates after improving.
In the present embodiment, efflux coefficient C is for different restriction device algorithm differences, and the restriction device that the present embodiment is corresponding is ISO long-radius nozzle.In the present embodiment in the time that throttling element is a certain specific ISO long-radius nozzle (and opening diameter d
0, when aperture ratio β is a definite value of defined in example), described throttling element characteristic coefficient K is certain certain value (the K value that meets the ISO long-radius nozzle of the present embodiment under example condition is 1.318161).Certainly,, if the throttling element of selecting is other ISO long-radius nozzles, can calculate by formula of the present invention (2).
Formula in the present invention (1) is to shift onto and obtain based on following principle:
Conventional feedwater flow calculates formula:
In formula:
Q
m-mass rate, kg/s;
C-efflux coefficient;
D-throttling element opening diameter, m;
ε-expansibility factor; ε=1 in the time being water;
ρ-detected fluid density, kg/m3;
The ratio of β-throttling element aperture and inside diameter of straight pipe section, β=d/D;
Δ p-differential pressure, Pa.
But because parameter is too much, computing method complexity, seldom used by power plant, Given this, simplify this computing formula and obtain the particularly important of the simple change of place of equation accurately, the inventor finds, is directed to specific throttling, correlation parameter be specific constant or change less, obtain thus formula of the present invention (1).
The above embodiment is only the preferred embodiments of the present invention, and is not the exhaustive of the feasible enforcement of the present invention.For persons skilled in the art, any apparent change of under the prerequisite that does not deviate from the principle of the invention and spirit, it having been done, within all should being contemplated as falling with claim protection domain of the present invention.
Claims (2)
1. the feedwater flow method for accurate testing based on throttling element characteristic coefficient K, is characterized in that: it specifically comprises the steps:
Step 1 is measured specific operation down-off differential pressure value and fluid density;
Step 2 is measured step 1 the flow differential pressure value and the fluid density that obtain, brings formula (1) into and calculates:
（1）
In formula:
-flow differential pressure value, unit K pa;
-fluid density, units/kg/m
3;
Q-feedwater flow, the t/h of unit;
K-throttling element characteristic coefficient.
2. a kind of feedwater flow method for accurate testing based on throttling element characteristic coefficient K according to claim 1, is characterized in that, definite method of described throttling element characteristic coefficient K is as follows:
By calculating and read correlation parameter, calculate throttling element characteristic coefficient K based on formula (2):
（2）
In formula:
D
0-throttling element opening diameter, m;
ε-expansibility factor; ε=1 in the time being water;
The ratio of β-throttling element aperture and inside diameter of straight pipe section (D), β=d/D;
C-efflux coefficient;
Re-Reynolds number, its computing formula is:
the flow velocity of-feedwater, unit: m/s;
the kinematic viscosity of-feedwater, unit: Pa.s.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105091957A (en) * | 2015-05-27 | 2015-11-25 | 东南大学 | A thermal power generating unit feedwater flow measuring method |
| CN108414400A (en) * | 2018-04-19 | 2018-08-17 | 泉州市法尔机械科技有限公司 | The determination method and decision-making system of oil viscosity |
| CN108871511A (en) * | 2018-06-29 | 2018-11-23 | 南京罕华流体技术有限公司 | A kind of linkage type industrial flow accurate measurement method |
| CN110426085A (en) * | 2019-08-29 | 2019-11-08 | 中电华创电力技术研究有限公司 | A kind of restrictive flow measuring device flow algorithms |
| CN109945936B (en) * | 2019-03-25 | 2020-06-09 | 中国电力工程顾问集团西北电力设计院有限公司 | Water and steam flow calculation method based on throttling device measurement |
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| CN101344105A (en) * | 2008-08-12 | 2009-01-14 | 大连海事大学 | Hydraulic system power measurement apparatus of V prick flow transducer based on MEMS |
| CN102818660A (en) * | 2012-08-10 | 2012-12-12 | 福州宏美实业有限公司 | Heat metering system for organic heat carrier |
| CN103424149A (en) * | 2013-08-06 | 2013-12-04 | 江苏科技大学 | Olive-shaped differential pressure flow meter |
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| CN101344105A (en) * | 2008-08-12 | 2009-01-14 | 大连海事大学 | Hydraulic system power measurement apparatus of V prick flow transducer based on MEMS |
| CN102818660A (en) * | 2012-08-10 | 2012-12-12 | 福州宏美实业有限公司 | Heat metering system for organic heat carrier |
| CN103424149A (en) * | 2013-08-06 | 2013-12-04 | 江苏科技大学 | Olive-shaped differential pressure flow meter |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105091957A (en) * | 2015-05-27 | 2015-11-25 | 东南大学 | A thermal power generating unit feedwater flow measuring method |
| CN105091957B (en) * | 2015-05-27 | 2018-04-03 | 东南大学 | A kind of fired power generating unit feedwater flow assay method |
| CN108414400A (en) * | 2018-04-19 | 2018-08-17 | 泉州市法尔机械科技有限公司 | The determination method and decision-making system of oil viscosity |
| CN108414400B (en) * | 2018-04-19 | 2021-02-26 | 泉州市法尔机械科技有限公司 | Oil product viscosity determination method and system |
| CN108871511A (en) * | 2018-06-29 | 2018-11-23 | 南京罕华流体技术有限公司 | A kind of linkage type industrial flow accurate measurement method |
| CN109945936B (en) * | 2019-03-25 | 2020-06-09 | 中国电力工程顾问集团西北电力设计院有限公司 | Water and steam flow calculation method based on throttling device measurement |
| CN110426085A (en) * | 2019-08-29 | 2019-11-08 | 中电华创电力技术研究有限公司 | A kind of restrictive flow measuring device flow algorithms |
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Application publication date: 20140903 |