JPH0476565B2 - - Google Patents
Info
- Publication number
- JPH0476565B2 JPH0476565B2 JP61106973A JP10697386A JPH0476565B2 JP H0476565 B2 JPH0476565 B2 JP H0476565B2 JP 61106973 A JP61106973 A JP 61106973A JP 10697386 A JP10697386 A JP 10697386A JP H0476565 B2 JPH0476565 B2 JP H0476565B2
- Authority
- JP
- Japan
- Prior art keywords
- flow rate
- differential pressure
- coefficient
- calculated
- equation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 claims description 16
- 239000012530 fluid Substances 0.000 claims description 8
- 238000000691 measurement method Methods 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 3
- 238000007429 general method Methods 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
Landscapes
- Measuring Volume Flow (AREA)
Description
＜産業上の利用分野＞
本発明は、オリフイスを用いた差圧式流量計の
流量補正に関するものである。
＜従来技術＞
流体管路に挿入されたオリフイスを用いた差圧
式流量計では、一般に差圧をΔPとしたとき、流
量Ｆは、Ｆ∝∝として計算される。例えば、
差圧範囲０〜1000mmH2Ｏ、流量範囲０〜10000N
m3／ｈとした場合、ΔP＝500mH2Ｏのときの流
量は7071Nm3／ｈという具合である。
＜発明が解決しようとする問題点＞
しかしながら、測定差圧に基づいて流量を高精
度で求める方法として、JISZ8762−1969の手法
を用いると、既に述べた一般的な方法との間に結
果において差を生ずる。
この原因は、一般的な方法では、レイノルズ数
の変化、流量係数の変化などを全く無視している
ため、及びオリフイスの設計は上の例では最大流
量（10000Nm3／ｈ）で行われているわけではな
く、常用流量で設計されているためである。
従つてJISZ8762−1969の手法による計算値と
Ｆ∝√による一般手法による計算値とは常用
流量値でのみ一致する事になる。
流量Ｆと差圧ΔPとの関係は、流体の場合、
Ｆ＝Ｋ・√
＝0.012522・α・D2・√・√ ……(1)
で定義される。ここで、αは流量係数、Ｄは管路
の直径、√は流体密度である。流量係数αは、
流体のレイノルズ数ReD（流量、粘度、管径によ
つて決まる）及び圧力取り出し口の位置で決まる
定数βをパラメータとして変化する定数であつ
て、この定数は、JISZ8762−1969の表４、表９、
表14、式(13)、式(17)、式(21)において、流量係数
αで示されている。
従つて、JISZ8762−1969の手法に従つた高精
度の流量測定では、流量によつて変化、するレイ
ノルズ数及びβをパラメータとして表４、表９、
表14、式(13)、式(17)、式(21)により流量係数αを
求めないと(1)式の流量Ｆが計算できないことにな
り、リアルタイムに流量の真値を求める測定手段
としては採用しにくい。
本発明は、JISZ8762−1969の手法で求めた計
算流量値を真値とし、差圧を測定して、その差圧
をJISZ8762−1969の手法によらないリアルタイ
ム演算を実行する事により、真値に近い値を求め
る測定方式の提供を目的とする。
＜問題点を解決するための手段＞
本発明方式の特徴は、流体管路に挿入されたオ
リフイスに発生する差圧ΔPに基づいて流量を算
出する差圧式流量計において、JISZ8762−1969
の手法により計算した流量Ｆを、Ｆ＝Ｋ・√
としたとき、上記係数Ｋを上記測定差圧ΔPをパ
ラメータとするｎ次の多項式
Ｋ＝ａ（ΔP）n-2＋ｂ（ΔP）n-1
＋ｃ（ΔP）n-2＋……＋Ｘ ……(2)
の演算により算出し、補正された測定流量F′を
F′＝Ｋ・√ ……(3)
でリアルタイムに算出することにある。
＜作用＞
本発明によれば測定差圧ΔPを入力し、あらか
じめ定数の決定されているｎ次の多項式、
Ｋ＝ａ（ΔP）n＋ｂ（ΔP）n-1
ｃ（ΔP）n-2＋……＋Ｘ
がリアルタイムに算出されて係数Ｋが決定され
る。
＜実施例＞
第１図は本発明方式による流量測定装置の基本
構成図である。１は流体Ｑが流れる管路、２は管
路に挿入されたオリフイスの両端に発生する差圧
ΔPを測定して４〜20mAの電流伝送信号を発信
する差圧伝送器、３は電流伝送信号を１〜5Vな
どの電圧信号に変換する信号変換器、４は電圧信
号を入力してＡ／Ｄ変換等のコンピユータ処理の
ためのデータ加工を行う入出力カードであり、加
工データを高速データバス５を介して演算手段６
に伝送する。
５はマイクロコンピユータ手段を有する演算手
段であり、ソフトウエア機能により差圧ΔPの関
数である(2)式による係数Ｋの演算並びにこの係数
と差圧ΔPによる(3)式による流量F′の計算を実行
し、入出力カード４を介して外部に発信する。
第２図は、演算手段６における信号処理の手順
を示すフローチヤートである。
次に、(2)式を２次の多項式で近似して係数Ｋを
求める実施例につき説明する。
この場合のＫの演算式は、
Ｋ＝ａ（ΔP）2＋ｂ（ΔP）＋ｃ ……(4)
となる。
<Industrial Application Field> The present invention relates to flow rate correction of a differential pressure type flowmeter using an orifice. <Prior Art> In a differential pressure flowmeter using an orifice inserted into a fluid pipe, the flow rate F is generally calculated as F∝∝ when the differential pressure is ΔP. for example,
Differential pressure range 0~ 1000mmH2O , flow rate range 0~10000N
m 3 /h, the flow rate when ΔP=500mH 2 O is 7071Nm 3 /h. <Problems to be Solved by the Invention> However, when using the method of JIS Z8762-1969 as a method for determining the flow rate with high precision based on the measured differential pressure, there is a difference in results between the method and the general method described above. will occur. The reason for this is that the general method completely ignores changes in Reynolds number, flow coefficient, etc., and the orifice is designed at the maximum flow rate (10000Nm 3 /h) in the above example. This is not because it is designed with a normal flow rate. Therefore, the value calculated by the JIS Z8762-1969 method and the value calculated by the general method using F∝√ match only in the normal flow rate value. In the case of a fluid, the relationship between flow rate F and differential pressure ΔP is defined as F=K・√=0.012522・α・D 2・√・√ ...(1). Here, α is the flow coefficient, D is the diameter of the conduit, and √ is the fluid density. The flow coefficient α is
It is a constant that changes using the Reynolds number Re D of the fluid (determined by the flow rate, viscosity, and pipe diameter) and the constant β determined by the position of the pressure outlet. 9,
In Table 14, Equation (13), Equation (17), and Equation (21), it is indicated by the flow coefficient α. Therefore, in highly accurate flow measurement according to the method of JIS Z8762-1969, Table 4, Table 9,
The flow rate F in equation (1) cannot be calculated unless the flow coefficient α is determined using Table 14, equations (13), equations (17), and equations (21). is difficult to adopt. The present invention takes the calculated flow rate value obtained using the method of JIS Z8762-1969 as the true value, measures the differential pressure, and calculates the differential pressure in real time without using the method of JIS Z8762-1969. The purpose is to provide a measurement method that obtains close values. <Means for Solving the Problems> The feature of the present invention method is that it is a differential pressure type flowmeter that calculates the flow rate based on the differential pressure ΔP generated in an orifice inserted in a fluid pipe, and is based on JISZ8762-1969.
The flow rate F calculated using the method is F=K・√
Then, the coefficient K is an n-th order polynomial with the measured differential pressure ΔP as a parameter K=a(ΔP) n-2 +b(ΔP) n-1 +c(ΔP) n-2 +...+X... The purpose is to calculate the corrected measured flow rate F' by the calculation in (2) in real time using F'=K・√...(3). <Operation> According to the present invention, the measured differential pressure ΔP is input and the n-th order polynomial whose constant is determined in advance is expressed as K=a(ΔP) n +b(ΔP) n-1 c(ΔP) n-2 + ...+X is calculated in real time and the coefficient K is determined. <Example> FIG. 1 is a basic configuration diagram of a flow rate measuring device according to the method of the present invention. 1 is a pipe through which fluid Q flows, 2 is a differential pressure transmitter that measures the differential pressure ΔP generated at both ends of an orifice inserted in the pipe and transmits a current transmission signal of 4 to 20 mA, and 3 is a current transmission signal. 4 is an input/output card that inputs the voltage signal and processes data for computer processing such as A/D conversion, and transfers the processed data to a high-speed data bus. 5 to the calculation means 6
to be transmitted. 5 is a calculation means having a microcomputer means, which uses a software function to calculate the coefficient K according to equation (2), which is a function of differential pressure ΔP, and to calculate the flow rate F' according to equation (3) using this coefficient and differential pressure ΔP. is executed and sent to the outside via the input/output card 4. FIG. 2 is a flowchart showing the procedure of signal processing in the calculation means 6. Next, an example will be described in which the coefficient K is obtained by approximating equation (2) with a second-order polynomial. The calculation formula for K in this case is: K=a(ΔP) 2 +b(ΔP)+c (4).
【表】
正規化した差圧ΔPの０〜100％につき10％ごと
に流量をJISZ8762−1969の手法で求め、その場
合の係数Ｋを算出した対応表を表１に示す。[Table] Table 1 shows a correspondence table in which the flow rate is determined in 10% increments of the normalized differential pressure ΔP from 0 to 100% using the method of JIS Z8762-1969, and the coefficient K in that case is calculated.
【表】
表１に基づきＫの値及びΔPの値により正規方
程式を立てて(4)式の定数ａ，ｂ，ｃを求めると、
ａ＝0.00167
ｂ＝−0.00550
ｃ＝1.00238
となる。この結果を(4)式、(3)式に代入して得た流
量F′とＦを比較すると表２のようになる。
表２において明らかなように、計算により求め
られた流量F′とJISZ8762−1969の手法により求
められた流量Ｆとの誤差は極めて小さく、F′はＦ
に対して0.1％以内の一致精度を実現することが
できた。
＜発明の効果＞
以上説明したように、本発明によれば測定差圧
ΔPに基づいてΔPの関数の形で係数Ｋをリアルタ
イムに演算することができるので、JISZ8762−
1969の手法による流量計算結果とほぼ同等の測定
精度で流量測定が連続的に可能となり、精度の高
い流量測定又は流量制御システムを低コストで実
現することが可能となる。[Table] Based on Table 1, a normal equation is set up using the value of K and the value of ΔP to find the constants a, b, and c in equation (4), and the following results are obtained: a=0.00167 b=−0.00550 c=1.00238. Table 2 shows a comparison of the flow rates F' and F obtained by substituting this result into equations (4) and (3). As is clear from Table 2, the error between the calculated flow rate F' and the flow rate F determined by the method of JISZ8762-1969 is extremely small, and F' is F'.
We were able to achieve a matching accuracy of within 0.1%. <Effects of the Invention> As explained above, according to the present invention, the coefficient K can be calculated in real time in the form of a function of ΔP based on the measured differential pressure ΔP.
It becomes possible to continuously measure the flow rate with almost the same measurement accuracy as the flow rate calculation result using the 1969 method, and it becomes possible to realize a highly accurate flow measurement or flow control system at low cost.
第１図は本発明方式による流量測定システムの
基本構成図、第２図は演算手段の動作説明図であ
る。
１……流体管路、２……差圧伝送器、３……信
号変換器、４……入出力カード、５……高速デー
タバス、６……演算手段。
FIG. 1 is a basic configuration diagram of a flow rate measuring system according to the present invention, and FIG. 2 is an explanatory diagram of the operation of the calculation means. DESCRIPTION OF SYMBOLS 1... Fluid pipe line, 2... Differential pressure transmitter, 3... Signal converter, 4... Input/output card, 5... High-speed data bus, 6... Arithmetic means.
Claims (1)
差圧ΔPに基づいて流量を算出する差圧式流量計
において、JISZ8762−1969の手法による計算値
流量Ｆを、Ｆ＝Ｋ・√としたとき、上記係数
Ｋを上記測定差圧ΔPをパラメータとするｎ次の
多項式、 Ｋ＝ａ（ΔP）n＋ｂ（ΔP）n-1 ＋ｃ（ΔP）n-2＋……＋ｘ の演算により算出し、補正された測定流量F′を
F′＝Ｋ・√でリアルタイムに算出することを
特徴とする差圧式流量測定方式。[Claims] 1. In a differential pressure flowmeter that calculates the flow rate based on the differential pressure ΔP generated in an orifice inserted into a fluid pipe, the calculated flow rate F according to the method of JIS Z8762-1969 is expressed as F=K・When √, the coefficient K is calculated as an n-th polynomial with the measured differential pressure ΔP as a parameter, K=a(ΔP) n +b(ΔP) n-1 +c(ΔP) n-2 +...+x Calculate and correct the measured flow rate F′ by
A differential pressure flow rate measurement method that is characterized by real-time calculation of F'=K・√.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10697386A JPS62263416A (en) | 1986-05-10 | 1986-05-10 | Differential pressure type flow rate measuring system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10697386A JPS62263416A (en) | 1986-05-10 | 1986-05-10 | Differential pressure type flow rate measuring system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62263416A JPS62263416A (en) | 1987-11-16 |
| JPH0476565B2 true JPH0476565B2 (en) | 1992-12-04 |
Family
ID=14447238
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10697386A Granted JPS62263416A (en) | 1986-05-10 | 1986-05-10 | Differential pressure type flow rate measuring system |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62263416A (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5629120A (en) * | 1979-08-17 | 1981-03-23 | Sumitomo Metal Ind Ltd | Flow measuring method |
-
1986
- 1986-05-10 JP JP10697386A patent/JPS62263416A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5629120A (en) * | 1979-08-17 | 1981-03-23 | Sumitomo Metal Ind Ltd | Flow measuring method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62263416A (en) | 1987-11-16 |
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