RU2488103C2 - Method of controlling detached vapour voidage and phase velocity of wet steam in steam pipe - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of controlling detached vapour voidage and phase velocity of wet steam in a steam pipe includes measuring static steam pressure, dynamic pressure and dynamic vacuum in an initial mode and in two flow modes varied based on flow rate, restoring the initial static pressure in the varied modes. Computation is then performed, said computation including measurement of dryness of wet steam.

EFFECT: enabling realisation of the method on a stream without measuring mass flow of wet steam.

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Description

FIELD OF THE INVENTION

The invention relates to technical physics, and in particular to the field of monitoring parameters of wet steam, and can be used to control the true volumetric steam content and phase velocities of wet steam in the steam pipe on the stream.

State of the art

An analogue of the invention is a control method, including: measuring static steam pressure, dynamic pressure and dynamic vacuum in a stream of wet steam; calculation of the totality of all measurements [Kovalenko A.V. On the issue of developing means for controlling the thermophysical parameters of a wet steam stream. - Sat Problems of a comprehensive study and pilot industrial implementation of thermal methods to enhance oil recovery. - M .: VNIIOENG, 1983, p. 59-68].

With the essential features of the invention, the following set of features of the analogue coincides: “measurement of static vapor pressure, dynamic pressure and dynamic vacuum; calculation ".

The disadvantage of an analogue is:

A. Insufficient accuracy due to the lack of control and compensation of disturbances from measuring instruments of dynamic pressure and dynamic rarefaction.

The prototype of the invention is a control method, including: measuring the mass flow rate, static vapor pressure, dynamic pressure and dynamic vacuum in the initial mode and in two changed flow conditions, restoring the original static pressure; calculation.

[A.S. USSR No. 1288568; “A method for determining the ratio of true volumetric steam content to volumetric flow rate steam content of the wet steam stream”; Kovalenko A.V., Shulman B.Kh., Demekhin E.A .; priority from 01.29.85, registered in the State Register of Inventions on 08/10/1986].

With the essential features of the invention coincides with the following set of features of the prototype:

“Measurement of static vapor pressure, dynamic pressure and dynamic rarefaction in the initial mode and in two modified flow conditions, restoration of the initial static pressure; calculation ".

The disadvantage of the prototype is:

A. Measurement of the mass flow rate of wet steam - on the stream, this parameter is not available for measurement.

SUMMARY OF THE INVENTION

The problem to which the invention is directed, is: a method for controlling the true volumetric steam content and the phase velocities of wet steam in the steam line in the stream.

When carrying out the invention, the following technical result can be obtained:

A. The method is implemented on the stream without measuring the mass flow rate of wet steam.

The specified technical result is achieved by the fact that the method includes: measuring the static vapor pressure, dynamic pressure and dynamic rarefaction in the initial mode and in two altered, by flow, flow conditions, restoration of the initial static pressure in the changed modes; calculation; includes: measuring the degree of dryness of wet steam.

Thus, the objective of the invention is solved.

List of drawings

Fig. 1. The control scheme of the true volumetric steam content and the phase velocities of wet steam.

Information confirming the possibility of carrying out the invention

Fig. 1 shows a diagram of the implementation of the method for monitoring the true volumetric steam content and the phase velocities of wet steam in the steam line in the stream.

A device implementing the proposed method contains:

- a section of the steam line, with a static pressure meter 1, a dynamic rarefaction meter 2, a dynamic pressure meter 3, and a degree of dryness meter (4);

- a control valve (5) at the inlet, and a control valve (6) at the outlet of the section;

- calculator 7.

The use of meters of static pressure, dynamic vacuum and dynamic pressure is shown in the prototype (A.S. USSR No. 1288568). As a measure of the degree of dryness, any known device capable of performing this function can be adopted (for example, the device according to the invention patent RU 2380694 C1).

Measure: static pressure with meter 1, dynamic pressure with meter 2, dynamic pressure with meter 3, dryness with meter 4. Measurements are carried out both in the initial mode and in two additional, different flow rates, differing in mass flow rate. The true volumetric vapor content and the velocity of the phases of the flow are calculated from the totality of the measured parameters in the initial and additional modes from the following system of twelve non-linear equations:

$${\chi }_i=\frac{{\alpha }_i\cdot {\rho }_i^{\text{'}\text{'}\text{'}\text{'}}\cdot {\omega }_i^{\text{'}\text{'}\text{'}\text{'}}}{{\alpha }_i\cdot {\rho }_i^{\text{'}\text{'}\text{'}\text{'}}\cdot {\omega }_i^{\text{'}\text{'}\text{'}\text{'}}+(\mathrm{one}-{\alpha }_i)\cdot {\rho }_i^{\text{'}\text{'}}\cdot {\omega }_i^{\text{'}\text{'}}};(\mathrm{one})$$

$$k\cdot \Delta P_i={\alpha }_i\cdot {\rho }_i^{\text{'}\text{'}\text{'}\text{'}}\cdot \frac{{\left({\omega }_i^{\text{'}\text{'}\text{'}\text{'}}\right)}^2}{2}+(\mathrm{one}-{\alpha }_i)\cdot {\rho }_i^{\text{'}\text{'}}\cdot \frac{{\left({\omega }_i^{\text{'}\text{'}}\right)}^2}{2};(2)$$

$$k_p\cdot \Delta P_{pi}={\rho }_i^{\text{'}\text{'}\text{'}\text{'}}\cdot \frac{{\left({\omega }_i^{\text{'}\text{'}\text{'}\text{'}}\right)}^2}{2};(3)$$

$$c=\frac{{\alpha }_i\cdot {\omega }_i^{\text{'}\text{'}\text{'}\text{'}}+(\mathrm{one}-{\alpha }_i)\cdot {\omega }_i^{\text{'}\text{'}}}{{\omega }_i^{\text{'}\text{'}\text{'}\text{'}}}i=\mathrm{one,}23(\mathrm{four})$$

where: α is the true volumetric vapor content;

ω '', ω 'are the velocities of the vapor and liquid phases of the flow;

ρ '', ρ 'are the densities of the vapor and liquid phases of the stream;

k - coefficient taking into account disturbance from the meter

dynamic pressure;

k _p - coefficient taking into account the perturbation from the dynamic rarefaction meter;

c - Benkov parameter (ratio of true volumetric steam content to volumetric flow rate steam content);

χ is the degree of dryness of the wet steam stream;

ΔP _p - dynamic vacuum;

ΔP - dynamic pressure.

The following parameters are unknown in this system of twelve nonlinear equations: α ₁ , α ₂ , α ₃ , ω ₁ ^'' , ω ₂ ^'' , ω ₃ ^'' , ω ₁ ^' , ω ₂ ^' , ω ₃ ^' k, k _p , c.

The given system of equations can be solved as follows.

Fixing k _p at a point from the region of variation of this parameter, from equations of the form (3) we find the values of ω '':

$${\omega }_i^{\text{'}\text{'}}=\sqrt{\frac{2\cdot k_p\cdot \Delta P_{pi}}{{\rho }_i^{\text{'}\text{'}\text{'}\text{'}}}};(5)$$

из уравнений вида (1) и (4):Fixing “c” at a point from the region of possible variation of this parameter, for each i = 1, 2, 3, we find α _i , and $${\omega }_i^{\text{'}\text{'}}$$

from equations of the form (1) and (4):

$${\alpha }_i=\frac{{\chi }_i\cdot c\cdot {\rho }_i^{\text{'}\text{'}}}{{\chi }_i\cdot {\rho }_i^{\text{'}\text{'}}+{\rho }_i^{\text{'}\text{'}\text{'}\text{'}}-{\chi }_i\cdot {\rho }_i^{\text{'}\text{'}\text{'}\text{'}}}(6)$$

$${\omega }_i^{\text{'}\text{'}}=\frac{{\omega }^{\text{'}\text{'}\text{'}\text{'}}\cdot (c-{\alpha }_i)}{(\mathrm{one}-{\alpha }_i)}(7)$$

From equation (2), for example, for i = 3 we find the value of k:

$$k=\frac{{\mathrm{<figure-callout\; id="3"\; label="\alpha "\; filenames="00000015.png"\; state="\{\{state\}\}">\alpha </figure-callout>}}_3\cdot {\rho }_3^{\text{'}\text{'}\text{'}\text{'}}\cdot \frac{{\left({\omega }_3^{\text{'}\text{'}\text{'}\text{'}}\right)}^2}{2}+(\mathrm{one}-{\alpha }_3)\cdot {\rho }_3^{\text{'}\text{'}}\cdot \frac{{\left({\omega }_3^{\text{'}\text{'}}\right)}^2}{2}}{\Delta P_3}(8)$$

We substitute the found values of the parameters α ₁ , α ₂ , ω ₁ ^'' , ω ₂ ^'' , ω ₁ ^' , ω ₂ ^'' , k into equations of the form (2) for i = 1, 2.

As a result of this substitution, we obtain the values of "residuals" δ ₁ and δ ₂ :

$${\delta }_{\mathrm{one}}=k\cdot \Delta P_i-[{\alpha }_{\mathrm{one}}\cdot {\rho }_{\mathrm{one}}^{\text{'}\text{'}\text{'}\text{'}}\cdot \frac{{\left({\omega }_{\mathrm{one}}^{\text{'}\text{'}\text{'}\text{'}}\right)}^2}{2}+(\mathrm{one}-{\alpha }_{\mathrm{one}})\cdot {\rho }_{\mathrm{one}}^{\text{'}\text{'}}\cdot \frac{{\left({\omega }_{\mathrm{one}}^{\text{'}\text{'}}\right)}^2}{2}(9)$$

$${\delta }_2=k\cdot \Delta P_2-[{\alpha }_2\cdot {\rho }_2^{\text{'}\text{'}\text{'}\text{'}}\cdot \frac{{\left({\omega }_2^{\text{'}\text{'}\text{'}\text{'}}\right)}^2}{2}+(\mathrm{one}-{\alpha }_2)\cdot {\rho }_2^{\text{'}\text{'}}\cdot \frac{{\left({\omega }_2^{\text{'}\text{'}}\right)}^2}{2}(10)$$

From relations (5) - (8) it follows that the residuals δ ₁ and δ ₂ are functions of k _p and c:

$${\delta }_{\mathrm{one}}={\delta }_{\mathrm{one}}(k_p,\text{from})(\mathrm{eleven})$$

$${\delta }_2={\delta }_2(k_p,c)(12)$$

Thus, the original problem of solving a system of twelve non-linear equations with twelve variables is reduced to solving the following system of two non-linear equations:

$$|\begin{array}{l}{\delta }_{\mathrm{one}}(k_p,\text{c})=0(13)\\ {\delta }_2(k_p,\text{c})=0(\mathrm{fourteen})\end{array}$$

The system is solved by the Newton method with a relative error in the determination of unknown k _p and c not exceeding 0.001. The solution of the system converges in 4-5 iterations. The solution time on an ordinary personal computer does not exceed 1 s.

Claims (1)

A method for monitoring the true volumetric vapor content and the rates of the phases of the wet steam in the steam conduit on the stream, including: measuring the static pressure of the steam, dynamic pressure and dynamic rarefaction in the initial mode and in two changed flow rates, restoration of the initial static pressure in the changed modes; calculation; includes: measuring the degree of dryness of wet steam.

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