qv=cεα/sqr(2δp/( 1-β^4)/ρ 1)
Where: c outflow coefficient;
ε expansion coefficient
Alpha throttle opening cross-sectional area, m 2
Delta p differential pressure output by throttling device, pa;
β diameter ratio
Density of fluid to be measured at ρ 1 I-I, kg/m3;
Qv volume flow, m3/h
According to the compensation requirements, it is necessary to increase temperature and pressure compensation. According to the calculation book, the calculation idea is to calculate the flow at any temperature and pressure according to the process parameters at 50 degrees. In fact, what is important is the conversion of density. The calculation formula is as follows:
q=0.0047 14 187*d^2*ε*@sqr(δp/ρ)nm3/h0c 10 1.325kpa
That is, the volume flow at 0 degree standard atmospheric pressure that needs to be displayed on the screen.
According to the density formula:
ρ=P*T50/(P50*T)*ρ50
Where: ρ, p and t represent values at any temperature and pressure.
ρ50, P50 and T50 represent process reference points with gauge pressure of 0.04MPa at 50 degrees.
Combining these two formulas, it can be compiled in the program.
2. Gas calculation (omitted)
Three. program analysis
1. Instantaneous quantity
Temperature quantity: it must be converted into absolute centigrade temperature; That is +273. 15.
Pressure quantity: it must be converted into absolute pressure for calculation. That is gauge pressure+atmospheric pressure.
According to the calculation formula, the compensation calculation is carried out, and the data is stored in the register of PLC. At the same time, monitor on intouch screen.
2. Cumulative quantity
The accumulation is triggered by a scanning rising edge within 2 seconds, that is, the compensation flow value (Nm3/h) is converted from 1800 units to a flow value every 2 seconds for accumulation and summation, and the screen has the function of resetting and clearing.
A, calculate the liquid level height (horizontal tank calculation formula)
H(m)=P/(ρ gas *g)？
P= value measured by differential pressure transmitter, in Kpa.
2=0.45~0.48: set according to the maximum density of the flowmeter after normal inflation, and the unit is g/cm:ρ gas.
2g=9.8 Gravity acceleration: m/s;
Second, calculate the storage tank volume.
: 1: If hr (R is the radius of the liner and container, in m, and the project is 1.2m).
Angle LAOB=2*arccos((r-h)/r), expressed in radians.
2aobaobs = π r * l/(2π)-(1/2) * R2 * sinl displays the product.
Volume =S* tank length: the tank length of this project is12.1m;
: 2: If h=r (R is the inner radius of tank container in m, and the project is 1.2m).
2 cross-sectional area S=( 1/2)*πr
Display volume =S* tank length: project tank length12.1m;
: 3. If h>R (R is the radius of inner tank container in m, and the project is 1.2m).
The angle L=2*arccos((h-r)/r), in radian AOB.
2 cross-sectional area s = π r * (2π-L)/(2π)+(1/2) * R2 * sinluoaobaob
Display volume =S* tank length: project tank length12.1m;
Second, the linear conversion formula (applicable to vertical storage tanks)
(v stands for pressure difference, V_H stands for the next pressure difference, V_L stands for this pressure difference, h stands for the next liquid level, and l stands for the current liquid level).
First, lower the next pressure difference and the current pressure to get the pressure value of a certain interval, and then lower the liquid level to get the value of in.
The size of the liquid level in this interval, and then subtract the current pressure difference from the pressure difference collected on site to get the actual pressure difference.
The pressure difference between the inlet and outlet of the pipeline P=0.5-0.07=0.43MPA. If the pipeline length is L and the specific resistance of the pipeline is S (which can be obtained from the look-up table of the inner diameter D and the inner wall roughness N), the flow rate Q = (1/2).
Speed v = 4q/(3. 14d 2)
Where p is the density of the oil; Gravity acceleration.