JPH1090295A - Flow velocity calculating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a device hardly influenced by the level fluctuation within a petroleum tank by storing sampled volume data successively in a volume data memory circuit, and calculating the flow velocity of petroleum by a flow velocity calculating circuit on the basis of a plurality of output data. SOLUTION: A volume data 102 is inputted to a volume data memory circuit 5, and a read-out data 104 outputted from the memory circuit 5 is inputted to a flow velocity calculating circuit 6. The flow velocity calculating circuit 6 outputs a flow velocity value data 104. When each volume data is V1 , V2 ... Vs , the flow velocity value is α, the difference between the straight line represented by the expression V=αt+β (β is constant) and each volume data V1 , V2 ...Vs is a1 , a2 ...as , α and β such that the straight line of the expression V=αt+βpasses the center of each volume data V1 , V2 ...Vs and the difference a1 , a2 ...as is minimized are determined by the flow velocity calculating circuit 6, whereby the flow velocity value α never influenced by the level fluctuation within a petroleum tank can be calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow velocity calculating apparatus for determining a volume change rate (flow velocity) in an oil tank, and more particularly to a flow velocity calculating apparatus which is hardly affected by a liquid level fluctuation in the oil tank.

[0002]

2. Description of the Related Art The volume change rate of a conventional oil tank (hereinafter referred to as "the rate of change").
Called flow velocity. As a method for determining ()), the liquid level in the oil tank, in other words, the volume, is sequentially measured by a level meter provided in the oil tank, and the flow velocity is obtained from these volume changes.

FIG. 5 is a configuration diagram showing an example of the inside of such a conventional oil tank. In FIG. 5, 1 is an oil tank, 2 is a level gauge, 3 is a float, 4 is oil, 100 is an inlet, and 101 is an outlet.

At the time of oil injection, the oil tank 1 has an inlet 1
Petroleum 4 flows in from 00, while oil 4 flows out from the outlet 101 when oil is taken out.

The oil 4 stored in the oil tank 1
Float 3 is installed on the surface of the liquid.
The volume of the oil 4 in the oil tank 1 is obtained based on the position.

The operation of the conventional example shown in FIG. 5 will be described with reference to FIG. FIG. 6 is a characteristic curve diagram showing the sampled volume data and the flow velocity calculated based on these volume data.

In the conventional example, generally, the flow velocity is obtained by moving average the volume data obtained from the level meter 2 in a flow velocity calculator (not shown).

For example, "A", "B", and "B" in FIG.
"C", "d" and "e" are volume data.
Each value is "v₁"," V_Two"," V_Three”,”
v_n-1"And" v_n "Means that the volume data
Flow velocity "f"₁"~" F_n-1"" Means sampling time "T"
Then f₁= (V_Two-V₁) / T (1) f_Two= (V_Three-V_Two) / T (2): f_n-1= (V_n-V_n-1) / T (3).

When the average of equations (1) to (3) is taken, FIG.
A flow velocity "f" as shown in the middle "f" can be obtained.
That is, f = (f ₁ + f ₂ +... + F _n-1 ) / (n-1) (4)

[0010]

However, when Equation (4) is further arranged, f = ((v ₂ −v ₁ ) / T + (v ₃ −v ₂ ) / T +... + (V _n −v _{n−) 1) / T) / (n} -1) = (v 2 -v 1 + v 3 -v 2 + ... + v n -v n-1) / T (n-1) = (v n -v 1) / T (n-1) (5), and the result in the middle of the volume data "v _2" ~ "
v _{n -1} "is not considered at all, and there is a problem that the result of the flow velocity calculation tends to be unstable.

For example, at the time of oil injection and oil extraction, and FIG.
If a strong wind blows against the oil tank 1 as shown in the middle "A", the liquid level of the oil 4 will fluctuate, and the volume data sampled at this time will also fluctuate. There was a problem that said it would be difficult.
Accordingly, an object of the present invention is to realize a flow velocity calculation device that is less susceptible to liquid level fluctuations in an oil tank.

[0012]

According to a first aspect of the present invention, there is provided a flow rate calculating apparatus for determining a flow rate of oil based on a change in a liquid level in an oil tank. Are sequentially stored, and a flow velocity calculation circuit that calculates and outputs the flow velocity of oil based on a plurality of output data of the volume data storage circuit.

According to a second aspect of the present invention, in the first aspect of the present invention, {12ΣnV _n -6 (N + 1) ΣV _n } is used by using the volume data (V _n ) stored in the volume data storage circuit. / N (N + 1) (N-1)
T (however, “Σ” indicates that accumulation is performed in the range of n = 1 to N). A flow velocity calculation circuit that calculates a flow velocity value using a calculation formula is provided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing one embodiment of a flow velocity calculating device according to the present invention.

In FIG. 1, reference numeral 5 denotes a volume data storage circuit;
Is a flow velocity calculation circuit, 102 is volume data, 103 is read data, and 104 is flow velocity value data.

The volume data 102 is stored in the volume data storage circuit 5
The read data 103 output from the volume data storage circuit 5 is input to the flow velocity calculation circuit 6. Then, the flow velocity calculation circuit 6 outputs the flow velocity value data 104.

Here, the operation of the embodiment shown in FIG.
This will be described with reference to FIGS. FIG. 2 is a characteristic curve diagram for explaining the flow velocity calculation formula, FIG. 3 is a characteristic curve diagram showing the effect of the present invention, and FIG. 4 is a table showing flow velocity values in the embodiment and the conventional example.

In FIG. 2, "a", "b", "c", "d", and "e" are volume data, and these values are represented by "
_{V 1 "," V 2 "} ," V 3 "," V n-1 "and" V _n "
And

Further, the flow velocity is set to “α”, and “f” in FIG.
A straight line represented by V = αt + β (6) (where β is a constant), and a straight line represented by Expression (6)
And "g" in FIG. 2 which is the difference between
J, “ri,” “nu,” and “ru,” respectively,
a₁"," A_Two"," A _Three"," A_n-1"And" a_n"
And

Then, the above-mentioned “α” and “β” are determined so that the straight line represented by the equation (6) passes through the center of each volume data and the difference between each straight line and the volume data is minimized. The flow velocity value “α” which is not affected by the liquid level fluctuation in the oil tank can be calculated.

Further, the introduction of the equation will be described. First
From the "straight line passing through the center of each volume data represented by the formula (6)" be said to be a _{condition, Σa n = 0 (7)} ( where, "sigma" is accumulated in the range of n = 1 to N Is calculated.)

[0022] In addition, from the fact that a second condition, "the difference between each volume data is minimum," _{says, MinΣ | a n | (8} ) ( However, "MinΣ" Louis in the range of n = 1~N The calculated value is the minimum.)

The difference between equation (6) and each volume data is as follows: a _n = αt + β−V _n (9), and if the sampling time is “T” from the time axis in FIG. 2, it becomes “t = nT”. , equation (9) is _{a n = αnT + β-V} n (10).

[0024] Formula If (10) accumulates in the range of n = 1 to N according to Equation (7), Σan = (1 + 2 + 3 + ... + N) αT + Nβ-ΣV n = N (N + 1) αT / 2 + Nβ-ΣV n (11) Becomes

From equation (7), equation (11) becomes “0”, and 0 = N (N + 1) αT / 2 + Nβ−ΔV _n Nβ = ΔV _n −N (N + 1) αT / 2 β = ΔV _n / N− ( N + 1) αT / 2 (12)

On the other hand, "alpha" and "beta" are satisfies the equation ^{_{(8), MinΣa n 2 (}} 13) is also satisfactory.

[0027] ^{_{Thus, a n 2 = (αt +}} β-V n) becomes ^{2 = (αnT + β-V} n) 2 (14).

[0028] Here, by substituting the equation ^{_{(12), a n 2 =}} (αnT + ΣV n / N- (N + 1) αT / 2-V n) 2 = ((n- (N + 1) / 2) αT- ( _{V n -ΣV n / n))} 2 = (n- (n + 1) / 2) 2 α 2 T 2 +2 (n- (n + 1) / 2) (V n -ΣV n / n) αT + (V n - ^{_{ΣV n / n) 2 = (}} n 2 - (n + 1) n + ((n + 1) / 2) 2) α 2 T 2 -2 (nV n -nΣV n / N- (n + 1) V n / 2 + (n + 1) ΣV _n / 2N) αT + (V _n -ΣV _n / N) ² (15)

Further, the equation (15) is changed to n according to the equation (13).
= When accumulating in the range of ^{_{1~N, Σa n 2 = (Σn}} 2 - (N + 1) Σn + N ((N + 1) / 2) 2) α
_{^{2 T 2 -2 (ΣnV n -ΣnΣV}} n / N-ΣV n ((N + 1) /
2) + N (N + 1) ΣV _n / 2N) αT + Z (16) Here, “Z” is the accumulated value of the third term of the equation (15) and is a numerical value independent of “α”.

Further, by modifying the equation ^{_{(16), Σa n 2 =}} (N (2N + 1) (N + 1) / 6- (N + 1) N (N + 1) / 2 + N (N + 1) 2/4) α 2 T 2 - _{2 (ΣnV n - (n +} 1) ΣV n / 2) αT + Z = (n (2N + 1) (n + 1) / 6 + n (n + 1) 2/4) α 2 T 2 -2 (ΣnV n - (n + 1) ΣV n / 2 ) αT + Z = n (n + 1) (n-1) α 2 T 2/12 -2 (ΣnV n - (n + 1) become _{ΣV n / 2) αT + Z} (17).

[0031] Here, equation ^{(17) Y = Aα 2 -2Bα} + Z (18) A = N (N + 1) (N-1) T 2/12 (19) B = (ΣnV n - (N + 1) ΣV n / 2) When T (20) is substituted, Y = A (α ² −2αB / A + B ² / A ² ) + W = A (α−B / A) ² + W (21) (where W is a numerical value independent of α) There is.)

Since the minimum value is obtained when “α = B / A” in the equation (21), the equations (19) and (2) are added to the equation (21).
0), α = {({nV _n- (N + 1) ΣV _n / 2) T} / {N (N + 1)
^{(N-1) T 2/} 12} = {12ΣnV n -6 (N + 1) Σ
_{V n} / N (N +} 1) become (N-1) T (22 ).

That is, by calculating the flow velocity value "α" from the sampled volume data using the equation (22), all the sampled volume data is used for the calculation in the equation (22). The result of the flow velocity calculation does not become unstable.

For example, FIG. 3 shows an example of a flow velocity value calculated in the conventional example and a flow velocity value calculated in the embodiment. FIG.
The broken line of "a" in the middle is based on the conventional example, and the solid line of "b" in FIG. 3 is based on the embodiment.

Further, the liquid level is affected assuming a strong wind such as a typhoon or the like, and the value of the level meter fluctuates, so that when calculating the volume, it is "about ± 100 [kL / H] higher than the actual volume. It is assumed that there is a fluctuation of the liquid level to such an extent that an error "1" occurs.

In FIG. 3, during the time axis "0" to "50", there is no oil inflow or outflow, and the time axis "51".
Up to "97", the state where oil flowed in at a flow rate of "3600 [kL / H]".

The variation range of the flow velocity value in the state shown in FIG. 3 is as shown in FIG. As can be seen from FIG. 4, according to the embodiment, the accuracy is improved about 10 times compared with the conventional example. In other words, it is less susceptible to liquid level fluctuations in the oil tank.

As a result, using the volume data (V _n ), {12ΣnV _n −6 (N + 1) ΣV _n } / N (N + 1) (N−1)
T (however, “Σ” indicates that accumulation is performed in the range of n = 1 to N). By calculating the flow velocity value using the formula, it is hardly affected by the liquid level fluctuation in the oil tank. Become.

[0039]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. Volume data (V
_n) using _{{12ΣnV n -6 (N + 1} ) ΣV n} / N (N + 1) (N-1)
T (however, “Σ” indicates that accumulation is performed in the range of n = 1 to N). By calculating the flow velocity value using the calculation formula, it is hardly affected by the liquid level fluctuation in the oil tank. A flow velocity calculator can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing one embodiment of a flow velocity calculating device according to the present invention.

FIG. 2 is a characteristic curve diagram for explaining a flow velocity calculation formula.

FIG. 3 is a characteristic curve showing the effect of the present invention.

FIG. 4 is a table showing flow velocity values in an example and a conventional example.

FIG. 5 is a configuration diagram showing an example of the interior of a conventional oil tank.

FIG. 6 is a characteristic curve diagram showing volume data and a flow velocity calculated based on the volume data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oil tank 2 Level meter 3 Floating 4 Oil 5 Volume data storage circuit 6 Flow rate calculation circuit 100 Inlet 101 Outlet 102 Volume data 103 Read data 104 Flow velocity value data

Claims (2)

[Claims] 1. A flow rate calculating device for determining a flow rate of oil based on a change in a liquid level in an oil tank, a volume data storage circuit for sequentially storing sampled volume data, and a plurality of output data of the volume data storage circuit. And a flow rate calculation circuit for calculating and outputting the flow rate of the oil based on the flow rate. 2. Using the volume data (V _n ) stored in the volume data storage circuit, {12ΣnV _n -6 (N + 1) ΣV _n } / N (N + 1) (N−1)
A flow rate calculating circuit for calculating a flow rate value by using a calculation formula of T (where "Σ" indicates that accumulation is performed in the range of n = 1 to N). The flow velocity calculation device according to claim 1.