RU2680417C1 - Measuring system to determine the true volume gas content - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: invention relates to measuring systems for determining the physical properties of two-phase flows, namely, measuring systems for determining the true volumetric gas content of an oil-air emulsion flow in a pipeline. Measuring system includes a horizontal cylindrical section of the pipeline, at the input of which input the pressure and temperature of an oil-air emulsion measuring equipment, an electronic computing unit, volumetric flow and a differential pressure sensor are installed, moreover, the electronic computing unit is configured to calculate the true volumetric gas content of a two-phase oil-air emulsion by a certain ratio, which makes it possible to calculate the true volumetric gas content by direct calculation.

EFFECT: reduction of time spent on determining the true volumetric gas content in a two-phase oil-air emulsion flow through its direct calculation in real time.

1 cl, 1 dwg

Description

The invention relates to measuring systems for determining the physical properties of two-phase flows, namely, measuring systems for determining the true volumetric gas content of an oil emulsion oil emulsion stream in a pipeline. The invention can be used in the lubrication systems of an aircraft gas turbine engine, as well as in stationary gas turbine units and other power facilities. Also, the measuring system can be used to determine the gas content in other two-phase gas emulsions to control various technological processes.

The volumetric gas content in the oil-air emulsion is necessary to calculate its density, used in solving problems related to determining the parameters of gas-liquid media. As a rule, a long-term continuous real-time measurement of the true volumetric gas content of a two-phase flow is required at various operating modes of the equipment.

The operation of measuring systems for determining the gas content in a gas emulsion stream is based on various physical principles. Measuring systems make it possible to determine the true gas content in a pipeline section, in a local sample or in the volume of a pipeline section.

A known measuring system for determining the true volumetric gas content of a gas emulsion stream, including a generator that excites acoustic vibrations in a gas-liquid medium (RU 2115116, 1998). The disadvantage of this measuring system is the change in the hydrodynamic flow regime and the complexity of its implementation in pipelines of small diameter, for example, in the fuel or oil system of engines.

A known system for measuring the true volumetric gas content in the cross section of the pipeline containing a source and a detector of ionizing radiation (SU 1022002, 1983), but its use is limited by safety requirements. This system can be used only for gas emulsions that do not contain nitrogen, oxygen, helium, argon, krypton, xenon, which are not sensitive to infrared radiation.

A known measuring system for determining the volumetric gas content in a gas-liquid medium in the pipeline, including a horizontal measuring cylindrical section of the pipeline, temperature, pressure and flow sensors between the two sections of the section and an electronic computing unit configured to calculate the volumetric gas content according to the equation of state of an ideal gas, taking a two-phase gas-liquid system as a mixture of ideal compressible gas and incompressible fluid (US 6847898, 2005). A disadvantage of the known technical solution is the low accuracy of determining the thermodynamic characteristics of an emulsion, such as the speed of sound, adiabatic index, etc. In particular, the calculation of the speed of sound in a water-air emulsion without considering the compressibility of the liquid phase is 330 m / s, and taking into account compressibility it is 25 m / c, which is confirmed by its experimental measurement.

The closest analogue to the claimed invention is a measuring system for determining the true volumetric gas content of a two-phase oil-air emulsion stream in a pipeline (RU 152854, 2015), including a horizontal measuring cylindrical section of the pipeline, at the inlet of which there is a means for measuring the pressure and temperature of the oil-air emulsion, and an electronic computing unit electrically connected to a means of measuring pressure and temperature.

A disadvantage of the known technical solution is the need to use the method of successive approximations in solving two nonlinear equations with two unknowns for calculating the volumetric gas content. This method requires a significant investment of time to determine the true volumetric gas content and may not provide reliable results.

The technical problem to which the invention is directed is to reduce the time required to determine the true volumetric gas content in the flow of a two-phase oil-air emulsion.

The technical result achieved by the implementation of the present invention is to determine the true volumetric gas content of the flow of a two-phase oil-air emulsion through direct calculation in real time.

The technical result is achieved due to the fact that the measuring system for determining the true volumetric gas content of the flow of a two-phase oil-air emulsion in the pipeline includes a horizontal measuring cylindrical section of the pipeline, at the inlet of which there is a means for measuring the pressure P _em and temperature T _{em of the} oil-air emulsion, and an electronic computing unit, electrically connected to a means of measuring pressure P _em and temperature T _em , and the measuring system further includes a device for measuring volumetric flow installed at the inlet of the measuring section, and a differential pressure sensor installed between the input and output of the measuring section, while the electrical outputs of the device for measuring volumetric flow and differential pressure sensor are connected to an electronic computing unit, and the electronic computing unit is made with the ability to calculate the true volumetric gas content of a two-phase oil-air emulsion according to the following ratio:

_um α = (ρ _w -K _{t.tr MOD?} P / Q ² _MOD) / (ρ _w -ρ _g)

Where:

α _em - true volumetric gas content;

ρ _W - the density of the oil in the oil-air emulsion at the measured T _em and R _em ;

To _ttr - coefficient taking into account the pressure loss in the pipeline, m ⁴ ;

ΔР _ISM - the measured pressure drop in the flow of oil-air emulsion between the input and output of the measuring section;

Q _ISM - the measured volumetric flow rate of the air-oil emulsion;

ρ _g - the density of air in the oil-air emulsion when measured T _em and R _em

moreover:

Where:

F _TP - the area of the _{bore of the} measuring section of the pipeline;

λ _tp - coefficient of friction loss of the measuring section of the pipeline;

l _tp is the length of the measuring section of the pipeline;

d _tp is the diameter of the measuring section of the pipeline;

ζ _m - the total coefficient of local pressure loss in the measuring section of the pipeline.

These essential features provide a solution to the technical problem with the achievement of the claimed technical result, since the addition of the measuring system to a device for measuring volumetric flow installed at the inlet of the measuring section, connected by an electrical output to the electronic computing unit, and a differential pressure sensor installed between the input and output of the measuring plot, also connected by an electrical output to the electronic computing unit, and the execution of elec ronnogo computing unit to calculate the true void fraction biphasic oil-air emulsion by a certain ratio allows one to measure the true void fraction biphasic emulsion oil-air stream by direct calculation in real time.

The present invention is illustrated by the following detailed description of a measuring system for determining the true volumetric gas content of a two-phase oil-air emulsion flow in a pipeline with reference to the figure, which shows a diagram of the measuring system.

A measuring system for determining the true volumetric gas content of a two-phase oil-air emulsion flow in a pipeline includes a horizontal measuring cylindrical section 1 of the pipeline, at the input 2 of which there is a means 3 for measuring pressure P _em and temperature T _{em of an} oil-air emulsion, and an electronic computing unit 4 for calculating the true volumetric gas content of two-phase emulsion oil-air, oil and air density, and electrically connected to the pressure measurement means 3 _um and R Temperature T _um. The measuring system further includes a device 5 for measuring the volumetric flow rate installed at the input 2 of the measuring section 1, and a differential pressure sensor 6 installed between the input 2 and the output 7 of the measuring section 1. The electrical outputs of the device 5 for measuring the volumetric flow rate and the differential pressure sensor 6 are connected to the electronic computing unit 4, and the electronic computing unit 4 is configured to calculate the true volumetric gas content of a two-phase oil-air emulsion according to the following wearing:

Where:

α _em - true volumetric gas content;

ρ _W - the density of the oil in the oil-air emulsion at the measured T _em and R _em ;

To _ttr - coefficient taking into account the pressure loss in the pipeline, m ⁴ ;

ΔР _ISM - the measured pressure drop in the flow of oil-air emulsion between the input and output of the measuring section;

Q _ISM - the measured volumetric flow rate of the air-oil emulsion;

ρ _g - the density of air in the oil-air emulsion when measured T _em and R _em

moreover:

Where:

F _TP - the area of the _{bore of the} measuring section of the pipeline;

λ _tp - coefficient of friction loss of the measuring section of the pipeline;

l _tp is the length of the measuring section of the pipeline;

d _tp is the diameter of the measuring section of the pipeline;

ζ _m - the total coefficient of local pressure loss in the measuring section of the pipeline.

The means 3 for measuring pressure P _em and temperature T _{em of an} oil-air emulsion can be made in the form of separate pressure and temperature sensors or in the form of a combined pressure and temperature sensor.

A device 5 for measuring the volumetric flow rate is installed at the input 2 of the measuring section 1. The differential pressure sensor 6 with inputs is connected to the input 2 and the output 7 of the measuring section 1. The means 3 for measuring pressure and temperature are installed at the input 2 of the measuring section 1, in the cross section in which true volumetric gas content of the two-phase oil-air emulsion flow. The flow of oil-air emulsion in the pipeline provides a pressure source 8, which is not an element of the measuring system.

The means 3 for measuring pressure P _em and temperature T _em , a device 5 for measuring volumetric flow and a differential pressure sensor 6 can be mounted using fittings on the inner surface of the measuring section 1 of the pipeline in order to minimize the influence of their position on the flow in the pipeline.

As a device 5 for measuring the volumetric flow rate, a volumetric flow sensor or an electric volumetric flow meter pump (RU 2540204, 2015) can be used, the controller of which contains an algorithm for determining the volumetric flow rate based on a previously obtained experimental dependence of the volumetric flow rate through the pump on pump speed and pressure drop across it.

In particular, the length of the measuring section 1 may be at least seven dimensions of its diameter. To improve the accuracy of measuring the differential pressure, the length of the section 1, it is advisable to choose the maximum possible.

The device 5 for measuring the volumetric flow rate and sensors 3, 6 are configured to generate electrical measuring signals corresponding to the flow parameters of a two-phase oil-air emulsion, and the electronic computing unit 4 may include algorithms for processing measurement results, for example, algorithms for averaging the parameter value over a given interval and for inertia compensation measurement channels in the form of a well-known equation:

_Armature X = X + τ _{MOD MOD MOD} dx / dt,

Where:

X _cor - the adjusted value of the parameter;

X _ISM - the measured value of the parameter;

τ _ISM ^- time constant of the measuring instrument;

DX _rev / dt - the value of the derivative of the measured parameter.

The computing unit 4 memory entered the measuring site characteristics 1 pipeline: length l _TP diameter d _TP, coefficient λ _TP friction losses, the total coefficient ζ _m local pressure loss, as well as coefficients of analytical expressions or two-dimensional tables dependencies density ρ _w oil and density ρ _{g of} air from pressure P _em and temperature T _em in an oil-air emulsion to obtain calculated current values of these quantities:

ρ _W = f ₁ (P _em , T _em );

ρ _g = f ₂ (P _em , T _em ),

Where:

f ₁ (R _em , T _em ) is a function expressing the dependence of ρ _W on R _em and T _em ;

f ₂ (R _em , T _em ) is a function expressing the dependence of ρ _g from R _em and T _em .

The values of the coefficients λ _tp and ζ _m can be determined by known relations (see, for example, I.E. Idelchik, "Handbook of hydraulic resistance", 3rd edition, Moscow, "Engineering", 1992, pp. 10-11, 29-32). In particular, the coefficient λ _tp can be determined taking into account the Reynolds number (Re) as:

λ _mp = 64 / Re.

The measuring system for determining the true volumetric gas content is as follows.

The computing unit 4 reads information from the device 5 for measuring the volumetric flow rate, means 3 for measuring pressure and temperature, and the differential pressure sensor 6. The obtained information is processed, for example, in terms of compensating for the inertia of measuring instruments and averaging the results over a given time interval, the density of oil and air is calculated from the data stored in the memory of electronic computing unit 4, and the true volumetric gas content α _{em is} determined by the relation (1) .

Next, from the device 5 for measuring the volumetric flow rate, means 3 for measuring pressure and temperature, and the differential pressure sensor 6, new parameter values are read and a new value of α _{em is} determined.

As is known, the nature of the flow in pipelines of microbubble gas-liquid media, which include a two-phase oil-air emulsion, is no different from the nature of the flow of a single-phase fluid (see, for example, the article by B.V. Boshenyatov “Hydrodynamics of microbubble gas-liquid media,” TPU news, 2005 , t. 308, No. 6, p. 160). Consequently, the mass flow rate can be determined from the Darcy-Weisbach formula for calculating pressure losses due to friction of the emulsion on the pipe wall, which, after switching from volume flow to mass flow and taking into account pressure losses at local resistances in the pipeline, has the following form:

Where:

P _em.n and P _em.k - pressure value at the input 2 and output 7 of the measuring section 1, respectively;

G _TP - the mass flow rate;

ρ _em is the density of the emulsion at the inlet to section 1 of the pipeline;

F _TP - the flow area of the measuring section 1 of the pipeline, equal to:

F _mp = πd ² _mp / 4.

Equation (2) shows that the magnitude G _TP can be calculated from the measured differential? P _MOD pressure in the portion 1 of the pipeline, equal to the difference of pressure values at its input 2 and the output 7, and the characteristics measuring section 1 (geometric data and the loss factor).

G _TP size can also be determined from the measured volumetric flow Q and density ρ _{edited um} emulsion by the relation:

Since the mass flow rate is the same for the emulsion flow in the pipeline, substituting relation (3) into relation (2) we obtain the following equality:

whence the ratio for calculating the density of the emulsion has the form:

moreover

Relation (4) includes only the known characteristics of the pipeline and the measured values of the differential ΔP pressure _measurement and volume flow rate Q _measurement .

Substituting the known expression for the emulsion density into relation (4):

ρ _em = (1-α _em ) ρ _w + α _em ρ _g ,

we get the ratio:

ρ _w -K _{t.tr MOD?} P / Q = α _{edited um} (ρ _f -ρ _g)

from which we obtain the expression for calculating the volumetric gas content:

_um α = (ρ _w - K _{t.tr MOD?} P / Q ² _MOD) / (ρ _w -ρ _g).

Thus, using the measured volumetric flow rate Q _ISM emulsions and the differential pressure ΔP _ISM pressure in section 1 of the pipeline with a length of l _tr and a diameter of d _tr , as well as the calculated current values of the density ρ _{l of} oil and density ρ _{g of} air, the true volumetric gas content α _em flow can be calculated two-phase oil-air emulsion according to the ratio (1).

Relation (1) allows us to calculate the true volumetric gas content α _{em by} direct calculation, which confirms the solution of the claimed technical problem with the achievement of the technical result — reducing the time spent on determining the true volumetric gas content in the flow of a two-phase oil-air emulsion through its direct calculation in real time.

The solution to the problem of determining the volumetric gas content of a two-phase oil-air emulsion flow is especially important for lubrication systems of gas turbine engines (GTE). A stable oil-air emulsion is formed in the bearings of the gas turbine engine, which is pumped into the oil tank by pumps (Gulienko A.I. et al. Features of the working process in the oil cavity of the supports of the rotor of a gas turbine engine // VI International NTK "Problems of chemical chemistry: from experiment to high-level mathematical models." Collection of selected reports. - M.: “Border”, 2016, - p. 38-46). Information on the air content in the oil-air emulsion allows you to reliably calculate the pressure loss in the pumping path, the hydraulic power of the pumping pumps and other parameters, based on which the diameter of the pipelines, the power of the electric drive for pump rotation, etc. are determined.

The proposed measuring system makes it possible to determine the current instantaneous value of the true volumetric gas content of a two-phase oil-air emulsion flow in a pipeline at steady-state and transient conditions, for example, in the pumping path of an oil-air emulsion from the supports of a gas turbine rotor.

As an additional technical result in the implementation of the claimed measurement system, the accuracy and reliability of determining the true volumetric gas content of α _em also increases, since direct calculation, taking into account friction pressure losses, unlike the sequential calculation method, guarantees the convergence of the calculation process, for example, when pressure drops in the pipeline .

Claims (16)

A measuring system for determining the true volumetric gas content of a two-phase oil-air emulsion flow in a pipeline, including a horizontal measuring cylindrical section of the pipeline, at the input of which there is a means for measuring pressure P _em and temperature T _{em of an} oil-air emulsion, and an electronic computing unit electrically connected to a pressure measuring instrument P _em and temperature T _em , characterized in that it further includes a device for measuring volumetric flow installed at the inlet of the measuring section, and a differential pressure sensor installed between the input and output of the measuring section, while the electrical outputs of the device for measuring the volumetric flow rate and the differential pressure sensor are connected to the electronic computing unit, and the electronic computing unit is configured to calculate the true volumetric gas content of the two-phase oil-air emulsions in the following ratio: _um α = (ρ _w - K _{t.tr edited} ΔP / Q ² _MOD) / (ρ _f - ρ _g) Where: α _em - true volumetric gas content; ρ _W - the density of the oil in the oil-air emulsion at the measured T _em and R _em ; To _ttr - coefficient taking into account the pressure loss in the pipeline, m ⁴ ; ΔР _ISM - the measured pressure drop in the flow of oil-air emulsion between the input and output of the measuring section; Q _ISM - the measured volumetric flow rate of the air-oil emulsion; ρ _g - air density in the oil-air emulsion at the measured T _em and R _em , and:

Where: F _TP - the area of the _{bore of the} measuring section of the pipeline; λ _Tr - coefficient of friction loss of the measuring section of the pipeline; l _Tr - the length of the measuring section of the pipeline; d _Tr - the diameter of the measuring section of the pipeline; ζ _m - the total coefficient of local pressure loss in the measuring section of the pipeline.

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