RU2522144C2 - Apparatus for determining dryness, enthalpy, thermal and mass flow of wet steam - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to applied physics and can be used to determine parameters of wet steam. Disclosed is an apparatus for determining dryness, enthalpy, thermal and mass flow of wet steam, having a steam pipe with a static pressure measuring device and two flow parameter measuring devices, one of which is selective to vapour phase parameters of a stream, e.g. downstream a Pitot tube, and the other is selective to vapour and liquid parameters of a stream, e.g. opposite the stream from a Pitot tube, a controller for processing and storing signals from the measuring devices with connected outputs of the measuring devices, a flow energiser, as well as a constant stream cross-section area downstream the flow energiser, having receivers of all measuring devices. The apparatus further includes a steam sampling unit and a module for determining reference dryness values connected to the steam sampling unit and the controller.

EFFECT: high accuracy of determining parameters of wet steam.

1 dwg

Description

FIELD OF THE INVENTION

The invention relates to technical physics, and in particular to the field of determining the parameters of wet steam, and can be used to determine the degree of dryness, enthalpy, mass and heat flow rate of a stream of wet steam.

State of the art

An analogue of the invention is a device for determining the degree of dryness, enthalpy, mass and heat flow rate of a wet steam stream, comprising: a steam line with a static pressure meter and a flow rate meter that is selective for vapor phase parameters; a controller for processing and storing meter signals with connected meter outputs; steam sampling unit; a module for determining the degree of dryness connected to the steam sampling unit and to the controller [Patent No. 2444726 (RU), IPC G01N 25/60; “A device for monitoring thermal power, mass flow, enthalpy and degree of dryness of a wet steam stream”; Bulletin of inventions. 2012. No. 7].

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

steam line with a static pressure meter and a flow rate meter that is selective for the parameters of the vapor phase;

a controller for processing and storing meter signals with connected meter outputs;

steam sampling unit;

a module for determining the degree of dryness connected to the steam sampling unit and to the controller.

The disadvantages of the analogue are:

A. Low accuracy in determining the flow rate parameters of a wet steam stream.

B. Great delay in determining the degree of dryness - more than 25 seconds.

The prototype of the invention is a device for determining the degree of dryness, enthalpy, mass and heat flow rate of a stream of wet steam [RF Patent No. 2459198; “A device for controlling the degree of dryness, enthalpy, heat and mass flow rate of wet steam”; Kovalenko A.V .; Bulletin of inventions. 2012. No. 23], containing:

a steam line with a static pressure meter and two flow rate meters, one of which is selective for the parameters of the vapor phase, for example, a pitot tube directed along the stream, and the other is selective for the parameters of the vapor and liquid phases of the stream, for example, a pitot tube directed towards the flow;

a controller for processing and storing meter signals with connected meter outputs;

flow turbulator;

a section of a constant flow section located behind the turbulator, containing receivers of all meters.

With the essential features of the invention, the following set of features of the prototype coincides: “a steam line with a static pressure meter and two flow rate meters, one of which is selective for the parameters of the vapor phase, and the other for the parameters of the vapor and liquid phases of the stream;

a controller for processing and storing meter signals, with connected meter outputs;

flow turbulator;

a section of a constant flow section located behind the turbulator containing receivers of all meters ”. The disadvantage of the prototype is:

A. The error in determining the degree of dryness, enthalpy, heat and mass flow rates of wet steam, due to the lack of the ability to determine and correct the signal coefficient of the meter, selective to the parameters of the vapor phase, and the signal coefficient of the meter, selective to the parameters of both phases of the flow.

SUMMARY OF THE INVENTION

The problem to which the invention is directed, is: a device for determining the degree of dryness, enthalpy, heat and mass flow rates of wet steam.

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

A. Normalized accuracy of determining the degree of dryness, enthalpy, heat and mass flow rates of wet steam, due to the ability to automatically determine and correct the signal coefficient of the meter, selective to the parameters of the vapor phase, and the signal coefficient of the meter, selective to the parameters of both phases of the flow.

The specified technical result is achieved by the fact that the device containing:

a steam line with a static pressure meter and two flow rate meters, one of which is selective for the parameters of the vapor phase, for example, a pitot tube directed along the stream, and the other is selective for the parameters of the vapor and liquid phases of the stream, for example, a pitot tube directed towards the flow;

a controller for processing and storing meter signals with connected meter outputs;

flow turbulator;

a section of a constant flow section located behind the turbulator, containing receivers of all meters;

contains:

steam sampling unit;

a module for determining reference values of the degree of dryness connected to the steam sampling unit and to the controller.

Signs that distinguish from the closest analogue are expressed by the following set of signs: "contains:

steam sampling unit;

a module for determining reference values of the degree of dryness connected to the steam sampling unit and to the controller. ”

Thus, the objective of the invention is solved.

List of drawings

Fig. 1. A device for determining the degree of dryness, enthalpy, heat and mass flow rate of wet steam.

Information confirming the possibility of carrying out the invention

In Fig. 1. shows the implementation diagram of the proposed device for determining the degree of dryness, enthalpy, heat and mass flow of wet steam. This device contains:

- steam line 1 with a static pressure meter 2 and two flow rate meters, one of which is selective for the parameters of the vapor phase, for example, a pitot tube 3 directed along the stream, and the other is selective for the parameters of the vapor and liquid phases of the stream, for example, a pitot tube 4 directed towards the flow ;

- a controller 5 for processing and storing meter signals with connected meter outputs;

- turbulizer flow 6;

- a section of a constant flow section (between the Z-Y marks) located behind the turbulator, containing receivers of all meters;

- steam sampling unit 7;

- a module for determining the reference values of the degree of dryness 8, connected to the node for sampling steam and to the controller.

The turbulizer 6 provides "behind itself" the presence of a turbulized portion of the wet steam stream, in which the liquid dispersed phase is evenly distributed over the entire cross section of the stream, and the speeds of both phases are equal.

The signal of the static pressure meter 2 (P _cm ) determines the tabular parameters of the coolant: ρ ”is the density of the vapor phase;

ρ 'is the density of the liquid phase;

i ”is the vapor phase enthalpy;

i 'is the enthalpy of the liquid phase.

For an unlimited discrete series of moments of time, for known values of the coefficients k and k _P , from the measured parameters of the controlled flow P _cm , ΔР, ΔР _p from the system of equations (1), (2), the values of the true volumetric vapor content (α) and the phase velocity of the stream are obtained (ω) in the homogenized measuring section after the turbulator:

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

$$k_p\cdot \Delta P_p={\rho }^{″}\cdot \frac{{\left(\omega \right)}^2}{2};\text{(2)}$$

where ΔP _P is the signal of the dynamic rarefaction meter;

k _p is the coefficient of the signal of the dynamic rarefaction meter;

ΔР - dynamic pressure meter signal;

k is the coefficient of the signal of the dynamic pressure meter.

Consumption flow density (ρ) within the homogenized measuring section corresponds to the "local density" of the flow (ρ _places ):

$$\rho ={\rho }_{me\mathrm{from}t}=\alpha \cdot {\rho }^{″}+\left(\mathrm{one}-\alpha \right)\cdot {\rho }^{\prime },\left[\text{kg / m3}\right]\text{(four)}$$

For the current (real) time instant, other parameters of the wet steam flow are also calculated, namely:

The degree of dryness (χ) of the controlled flow of wet steam (determined by the parameter of the true volumetric steam content in the homogenized area):

$$\chi =\frac{\alpha \cdot {\rho }^{″}}{\alpha \cdot {\rho }^{″}+\left(\mathrm{one}-\alpha \right)\cdot {\rho }^{\prime }};\left[b/R\right]\text{(5)}$$

Enthalpy (i) of a controlled flow of wet steam:

$$i=\chi \cdot i^{″}+\left(\mathrm{one}-\chi \right)\cdot i^{\prime };\left[\mathrm{to}\mathrm{to}\mathrm{but}l/\mathrm{to}g\right]\text{(6)}$$

Mass flow (G) of the controlled flow of wet steam:

$$G=\rho \cdot \sqrt{\frac{2\cdot k_p\cdot \Delta P_p}{{\rho }^{″}}}\cdot F;\left[\mathrm{to}g/\mathrm{from}e\mathrm{to}\right]\text{(7)}$$

Heat flow (Q) of the controlled flow of wet steam (determined by the parameter of the true volumetric steam content in the homogenized area):

$$Q=G\cdot i;\left[\mathrm{to}\mathrm{to}\mathrm{but}l/\mathrm{from}e\mathrm{to}\right]\text{(8)}$$

In the system of two equations (1), (2) and equation (7), the coefficient of the meter selective to the parameters of both phases (k) and the coefficient of the meter selective to the properties of the vapor phase of the stream (k _p ) are used. These coefficients are determined and corrected by the system automatically. This possibility is provided by the presence in the system of two meters of the flow parameter, one of which is selective for the parameters and properties of only the vapor (gas) phase of the stream, while the signal of the other meter is formed by the parameters and properties of both phases of the two-phase stream of wet steam. As well as the presence of a flow turbulator installed in front of the measuring section, and a meter of reference values for the degree of dryness.

As a reference point measure of the degree of dryness (χ), any known measuring means can be used, for example, the device according to patent No. 2380694 (RU), the device according to patent No. (application No. 2011129977) or another.

The requirement for such a (other) device is: the ability to obtain normalized values of the degree of dryness in an unlimited discrete series of time instants.

Thus, to solve the problem of determining the coefficients, equations of the form (1), (2), (3) are used:

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

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

$$\begin{array}{l}{\chi }_i=\frac{{\alpha }_i\cdot {{\rho }^{″}}_i}{{\alpha }_i\cdot {{\rho }^{″}}_i+\left(\mathrm{one}-{\alpha }_i\right)\cdot {{\rho }^{\prime }}_i};\text{(3)}\\ \text{i}=\text{one}\text{, 2}\end{array}$$

The solution of such a system of equations is possible on two "sets" of initial data that differ in values. In order to solve the problem, six nonlinear equations with six unknowns are obtained: α ₁ , ω ₁ , α ₂ , ω ₂ , k, k _p .

When solving this system of equations, it is necessary to take into account the fact that the pressure drops and static pressure are determined without significant delay, that is: the measurement and determination of the values of these parameters is performed at the current real time. The reference values of the parameter of the degree of dryness, at each current determination moment, is formed from the flow parameters in the time interval lagging from the current moment, for example, in the time interval τ seconds. That is, the argument χ is delayed by the current moment in time for the interval of the time interval τ sec. In this regard, the correct data set cannot be obtained at the current time. In each data set (for solving six equations of the form (1), (2), (3) for i = 1,2), the time for determining the measured pressure drops and static pressure should be less than the time for determining the degree of dryness by the amount of delay of this argument. I.e:

, $${\chi }_2^{t_2}$$

, $$\Delta P_1^{t_1-\tau }$$

, $$\Delta P_2^{t_2-\tau }$$

, $$\Delta P_{p_i}^{t_1-\tau }$$

, $$\Delta P_{p_i}^{t_2-\tau }$$

, $$\left(P_{cm}^{t_1-\tau },P_{cm}^{t_2-\tau },\right)$$

.- Measured parameters: $${\chi }_{\mathrm{one}}^{t_{\mathrm{one}}}$$

, $${\chi }_2^{t_2}$$

, $$\Delta P_{\mathrm{one}}^{t_{\mathrm{one}}-\tau }$$

, $$\Delta P_2^{t_2-\tau }$$

, $$\Delta P_{p_i}^{t_{\mathrm{one}}-\tau }$$

, $$\Delta P_{p_i}^{t_2-\tau }$$

, $$\left(P_{cm}^{t_{\mathrm{one}}-\tau },P_{cm}^{t_2-\tau },\right)$$

.

на момент времени (t₁-τ) - первый набор данных;The scheme for solving this system of equations. According to the measured parameters (initial mode): - χ ₁ (reference value of the degree of dryness) at time (t ₁ ) and P _cm , ΔP ₁ , $$\Delta P_{p_{\mathrm{one}}}$$

at time (t ₁ -τ) - the first data set;

1. For time t ₁ -τ from equation (3) determine α ₁ :

$${\alpha }_{\mathrm{one}}=\frac{{\chi }_{\mathrm{one}}\cdot {{\rho }^{\prime }}_{\mathrm{one}}}{{{\rho }^{″}}_{\mathrm{one}}-{\chi }_{\mathrm{one}}\cdot {{\rho }^{″}}_{\mathrm{one}}+{\chi }_{\mathrm{one}}\cdot {{\rho }^{\prime }}_{\mathrm{one}}}$$

2. Take k _p = 1,0 (or other value from the range of its probable values).

3. From equation (2) at the accepted value of k _p determine the flow rate in the homogenized section of the steam pipe:

$${\omega }_{\mathrm{one}}=\sqrt{\frac{2\cdot k_p\cdot \Delta P_{P_{\mathrm{one}}}}{{{\rho }^{″}}_{\mathrm{one}}}}$$

4. From equation (1), using certain values of k _p and ω ₁ , get the value of k:

$$k=\left[{\alpha }_{\mathrm{one}}\cdot {{\rho }^{″}}_{\mathrm{one}}+\left(\mathrm{one}-{\alpha }_{\mathrm{one}}\right)\cdot {{\rho }^{\prime }}_{\mathrm{one}}\right]\cdot \frac{{\left({\omega }_{\mathrm{one}}\right)}^2}{2\cdot \Delta P_{\mathrm{one}}}$$

на момент времени (t₂-τ) - второй набор данных;According to the measured parameters of another (changed mode): - χ ₂ (reference value of the degree of dryness) at time (t ₂ ) and, P _cm , ΔP ₂ , $$\Delta P_{p_2}$$

at time (t ₂ -τ) - the second data set;

5. For time t ₂ -τ from equations (1), (2), (3), for i = 2, and fixed values of the coefficients k _p , k determined by the parameters of the initial mode, the residual (δ) of the velocity values is determined flow obtained respectively from equations (1) and (2):

$$\delta =\sqrt{\frac{2\cdot k\cdot \Delta P}{{\alpha }_2\cdot {\rho }_2{}^{″}+\left(\mathrm{one}-{\alpha }_2\right)\cdot {\rho }_2{}^{\prime }}}-\sqrt{\frac{2\cdot k\cdot \Delta P_{p_2}}{{\rho }_2{}^{″}}}$$

If the residual value δ> | 0.001 |, then the accepted value of k _{p is} changed (increased or decreased), for example, by 0.001 and returned to step 3 of the calculation algorithm.

Increase or decrease k _p by 0.001:

- if the decrease is greater than the deductible and the difference is greater than | 0.001 |, then increase;

- if the reduction is less than the deductible and the difference is greater than | 0.001 |, then decrease.

If δ <= | 0.001 |, then the values of the coefficients k _p , k are “approved” and, using the system of equations (1), (2), as well as formulas (4), (5), (6), (7), (8) calculate the current values of the degree of dryness, enthalpy, mass and heat flow rate of the wet steam stream.

Calculation of the current discrete values of the flow parameters is performed, for example, every 100 ms.

The determination of the coefficients k _p , k is advisable to carry out with a noticeable change in the current value of any of the measured parameters (for example, by 5% or more) with respect to its previous value in the past time interval.

Updating the coefficient values is possible in any current polling cycle of the measured parameters. The technical criterion for launching the coefficient calculation algorithm is the availability of initial information for solving: a system of six equations of the form (1), (2), (3).

Claims (1)

A device for determining the degree of dryness, enthalpy, mass and heat flow rate of wet steam, comprising a steam line with a static pressure meter and two flow rate meters, one of which is selective for the parameters of the vapor phase, for example, a pitot tube directed along the stream, and the other is selective for the parameters of the steam and liquid phases of the flow, for example, a pitot tube directed towards the flow, a controller for processing and storing meter signals with connected meter outputs, a flow turbulator, a section of a constant flow section located behind the turbulator containing receivers of all meters, the device also comprising a steam sampling unit and a module for determining reference values of the degree of dryness connected to the steam sampling unit and to the controller.