SU1046665A1 - Moist vapor dryness degree determination method - Google Patents

Abstract

A METHOD FOR DETERMINING THE DEGREE OF HUMID VAPOR DRYNESS, which consists in measuring the static pressure in a steam line and two control parameters functionally related, with a degree of steam dryness, followed by determining the degree of dryness according to measurement results, which is different in quality the control parameters use the dynamic vacuum created by the flow and the change in the amount of flow movement in the section of the steam line with different cross sections. (L N o: CX) O5 ate

Description

The invention relates to a measurement technique, in particular, to methods for measuring the degree of dryness of wet steam. A known method for measuring the degree of dryness of wet steam consists in measuring the salinity of the source water and the separated heavy phase of the wet steam. The degree of dryness is determined by the ratio of the salt content of the source water and the salt content of the separated liquid phase of wet steam 1. However, the accuracy of this method is low due to the presence of a number of uncontrollable factors, such as the degree of dissociation of water, affecting the conductivity of the sample, etc. . The closest to the invention by its technical nature is a method for determining the degree of dryness of wet steam, which consists in measuring the static pressure in the steam line and two-control parameters, functionally related to the degree of steam dryness, followed by measuring the degree of dryness Gz. However, according to a known method, it is necessary to separate the pairs into phases, and after measuring the flow rates of the individual phases, to achieve their ideal mixing. Greater inertia in the liquid line (separator, hydraulic seal, measuring vessel) is the cause of self-oscillations and a decrease in measurement accuracy. A constructive implementation of the method is bulky and metal consuming .... The purpose of the invention is to improve the accuracy of measuring the degree of dryness of wet steam. This goal is achieved by the fact that according to the method for determining the degree of dryness of wet steam, which consists in measuring the static pressure in the steam line and two control parameters functionally related to the degree of dryness of steam, followed by the determination of the degree of dryness by measurement results, the dynamic vacuum created by the flow and the change in the amount of flow in the section of the steam pipe with different cross sections. The drawing shows a technical scheme for implementing the proposed measurement method. . The device, realizing the proposed method, contains a measuring channel 1, connected in series in the pipeline and having two sections with different values of the living section, respectively S | .and Sp .. The lengths of the sections are selected so that within each of these sections there are sections in which the measured flow would be free from the influence of local resistances, the transitional zones from sections to section S-fj and resistances interface of the measuring channel with the pipeline. In both sections of the measuring channel, in zones free from the influence of local resistances, one receiver 2 and 3 of static pressure are contained. One of the sections also contains a pressure receiver 4, the inlet of which is от open in the direction of flow. The outputs of the static pressure receivers 2 and 3 are connected to the inputs of the differential pressure gauge 5. The outputs of the static pressure receiver 3 and the receiver, 4 pressures are connected to the inputs of the differential pressure gauge 6. The output of the static pressure receiver 3 is also connected to the input of the mandmeter 7. Operation of the device implementing the proposed method The measurement is as follows. The wet steam transported through the pipeline in the sections and the measuring channel with cross sections - and d due to the continuity of the two-phase flow takes the corresponding cross sections of the speed of movement of both its phases. At some distance from local resistances and transitions from one section to another in the areas of pressure receivers, with the accuracy required for practical calculations, the motion speeds of both phases of wet steam can be equal. Phase transformations during the transition from Sj to Sfi can be neglected, since their maximum value (of the order of 0.01.% Does not have a noticeable effect on the value of the measured parameters. In steam and steam pipelines, based on technical and economic considerations, wet steam transported with relatively high steam content (degree of dryness not lower than 0.3). At that, the conditions of the dispersive ring mode are fulfilled and the two-phase flow of wet steam is an indissoluble flow of saturated steam with droplets suspended in its volume liquid, i.e., uninterrupted vapor and finely dispersed liquid phase. The speed of the vapor phase (.V) is significantly higher than the speed of the liquid phase. At that, the ratio of speeds V and V obeys a known pattern and the technique is referred to as true phase velocities () -hi- ...; where CL is the true volumetric steam content / С is the phase slip constant.

The phase slip constant is a function of the static pressure (P) in. steam line and is determined by tables or empirical formula

, 71 + 0,00142253Р, (2) 5

The true volumetric steam content characterizes the fraction of the cross section occupied by niapOM, and is determined from the known values of the density of the vapor phase p, the density of the liquid phase (p-) / constant-Uyu slip phases (c) and the effective dynamic density of wet steam (). effective dynamic density is the kinetic characteristic of wet steam, satisfying -15 the known physical dependence (2 s 9.) - t / C1 c p-a (p- in order to use the formula (4) fg value. (Ci 9i P -. determined earlier by the measured static pressure value. Consider the known physical relationship characterizing the change in the amount of motion of a two-phase flow of wet steam in the section of the steam line with cross sections 5g and Vo can be recorded. P-VVP3 / -9 ", . Re, where DR is the static drop, pressures on the steam line section with cross sections Sf and Sjj (change in the amount of flow movement). By selecting the ratio to Sjj, it is possible to measure the resulting small difference, and at the same time they accept equality ..% - two seconds. for rd, the relative values are entered, the values of which from the cross section of 5m to the cross section of Sn are practically unchanged. - pV.p, -. v "From (5) we obtain a mathematical expression that allows us to determine the parameter # 1 through pressure drop in two flow sections (LP) at a known value of the speed of movement Flow - l (where, / Su Considering the real ranges of steam content of wet steam and the fact that the vapor phase, being the conveyor of the fine liquid phase, is inseparable (at least V-c-i .piWT

U () JSQ- o. T ol U oG

where V is the flow rate

Y vapor phase velocity

 - the speed of the liquid phase,

o1 - true volume paroso. holding,

under the assumption of the condition: V – V (the acceptance of this condition allows, without introducing simplifications, the use of the true values of the speeds and allows to obtain compact expressions for physical dependencies, not input, to understand the fictitious speed).

From the expression (3), the true volumetric steam content is L8-4 Cp-P) C p9. () Pe with a degree of dryness of 0.3 and more and that is interspersed. liquid, the phase does not alter the properties of the vapor phase (its density, VYa..ZKOSTY, etc.), the assumption was made that it was experimentally tested that a sensor was placed on the flow. dynamic dilution (the receiving window directed in the direction of the flow motion) is entrained by the vapor phase; the liquid phase does not have a practically noticeable effect. In other words, the pressure drop across the dynamic dilution sensor depends almost exclusively on the speed of the vapor phase Iv) and its density (p). This dependence can be represented as follows: II Vf ill-, where DR is the differential pressure at the sensor of dynamic rarefaction; . . - calibration factor. From the expression (9) and the accepted condition (V - V) J) .7 Thus, the measured flow rate (. (), The ratio of the true velocities phases (H), true volumetric steam content (o1), density of the steam flow phase (P), density of the flow phase (P), phase slip constant (s ;. Using certain values, the average flow density is known about the known physical dependence -; stream bone () P f). - GsmG4 -r -j re MrV ...

Considering the well-known phyic dependence

 - at

- th-x - tgg-X),

R o) CM. g

where PP is the degree of dryness wet

pair, convert expressions for X through pcAL tP9 p

, - -b-- ™

Thus, the problem of determining the degree of dryness is solved by measuring three parameters: P, g P, g kP.

Pr and measures. Measured parameters, MPa; . KPA - dR 1.5 KPA.

Design parameters: 5i

1.963495 U

5, - ,, 4. 41786 4 X

m

-)

XIO

m

The degree of dryness of the wet as a result of the calculation is 0.7537.

Using the proposed method for measuring the degree of wet steam dryness, as compared to the known methods, it is possible to accurately measure the degree of wet steam dryness of high parameters for regulation, control or accounting (combined with the flow rate for commercial calculation, as well as using oil. industrial capability (in combination with the flow control of the heat injected into the oil-bearing formation, which will ensure accurate regulation of the steam-thermal effect.

Claims (1)

METHOD FOR DETERMINING THE DEGREE OF WET VAPOR DRY, which consists in measuring the static pressure in the steam line and two control parameters functionally related to the degree of dryness of the steam, followed by determining the degree of dryness from the measurement results, that is, in order to increase accuracy, the dynamic rarefaction created by the flow and the change in the momentum of the flow in the section of the steam pipeline with different sections are used as control parameters. e se> .1046665