Arrangement for hydrodynamic measuring of density

FIELD: the invention refers to measuring technique particularly to flowing hydrodynamic density meters and may be used for measuring density of various mediums including commercial accounting with suppliers of fuel.

SUBSTANCE: the essence of the arrangement is in that the velocity of medium is measured with the method of zero-point difference of pressure and with the method of variable difference pressure velocity thrust is measured with the aid of a narrowing arrangement in working conditions of possible continuous changing. At measuring the velocity the medium passing through the first measuring site is not subjugated to compression and expansion.

EFFECT: essential expansion of the range of measurements, absence of leakage allows to measure velocity with maximum and identical accuracy on the whole range of measurements.

1 dwg

 

The invention relates to measurement techniques, in particular to the flow hydrodynamic density meters, and can be used to measure the density of different environments for liquids in open vessels, and in closed piping systems and vessels under pressure, including for commercial settlements with fuel suppliers.

The known device flow measurement density environments, such as [1. Civilis S. Densitometers. M Energy 1980, s], which includes a synchronous motor rotating at a constant speed impeller with spiral blades. Swirling flow transfers its energy to a cylindrical sleeve with inclined blades and axial shaft of the impeller. The measurement is carried out according to the indications depend on the density of the medium rotation angle liner associated with spring.

The disadvantages of these technical solutions is the large measurement error density, and the large size of the device.

A device for measuring the mass flow rate [2. Multivariable mass flow meter Multivariable model 3095 MV, the Prospect of Fischer - Rosemount 00813-0100-4716, Rev DA 11/98, phone (095) 2326968], including the measurement of the density and flow rate using the meter differential pressure mounted on narrowing unit (SU) in the stream environment.

The disadvantages of this device are:

special software on AspectJ for solving differential equations and adjustments, obtained by measuring other parameters of the flowing medium through SU;

- a relatively small range of speed measurement environment, providing a measurement error of 1%. In addition, the magnitude of the error in speed is not counted to the current value and the maximum scale value.

By construction, the closest analogue of one of the elements of the proposed density measuring device is a known device for determining the flow of homogeneous fluids [4. The flow meter PLU 103 And manufactured by Pierburg Luftfahrtgerate Union GmbH. Bataverstr. 80/ Postfach 100 261 D -4040 Neuss West-Germany.tel. (02101)523-1, factsheet], containing the pump motor with the motor in the circuit maintain a zero pressure differential, measuring the number of revolutions associated with the computer.

Closest to the proposed device adopted for the prototype, is a device for measuring the density when calculating mass flow [3. Method of measuring mass flow of a substance narrowing devices. Enterzone. W. It No. 12/2003]belonging to the class of hydrodynamic density meters.

The device [3] contains the SU in the main channel by measuring the differential pressure, the output of which is connected with the computer and also the Executive body and the valve located in the bypass channel entrance to the main channel outside the SU.

The disadvantages of the known the disorder [3] are:

- dimension of the main part of the velocity occurs at SU, which has a limited range;

- velocity of the medium is measured by the differential pressure on the quadratic dependence between them, which leads to a small range of measurement and the unevenness of the scale of the instrument;

the density of the medium is determined indirectly by the substitution ratio in the equation when calculating the mass flow rate;

- served periodic signal to open the valve of the bypass channel, i.e. there is a non-simultaneous measurement of velocity in the main channel and the bypass, which leads to additional error;

- there are unaccounted leakage through the bypass channel through the damper and volumetric flow meter, leading to error in the measurement of density and velocity;

for the density of the medium is searched for a value from the equations of the mass flow through the SU and the bypass;

- the presence of nonlinearity more than 1%, backlash and drift.

The aim of the invention is to remedy these shortcomings in the known devices.

For this purpose a device of the hydrodynamic measurement of the density of the medium containing a narrowing device for measuring differential pressure, the output of which is connected with the transmitter, characterized in that in series flow entered the pump flow and contour maintain a zero differential Yes the population by measuring differential pressure, the motor device maintain its speed and the pump-motor with the gauge of frequency of rotation of the shaft, the contour together with the gauge of frequency of rotation of the shaft is connected with the computer for processing measurement results, transform, and calculating the density of the medium.

A device running density measurement, in which method the zero differential pressure is measured velocity of the medium and at the same time in the same conditions, the measured pressure drop at SU.

Application device can also be open non-vessels, tanks and pipelines under pressure.

It employs two measuring area: one for measuring the flow speed of the medium, the other for measuring the differential pressure on SU and then calculating the density of the medium.

The drawing shows a diagram of the device.

The hydraulic path of the device consists of two measuring stations, which are: 1 - the first measuring section for measuring fluid velocity; 2 - input in the first measuring section; 3 - output from the first measuring section; 4 - pump-motor, for example, screw type; 5 - measuring section for measuring differential pressure; 6 - SU, for example, standard; 7 - entrance into the measuring section 5; 8 - output from the measuring section 5; 9 - connect the sustained fashion the pipeline; 10 - consumption booster; 11 - input pipeline.

Managing and measuring part of the device contains: 12 - zero-body differential pressure to measure the fluid velocity; 13 - motor, 14 - gauge of frequency of rotation of the shaft of the motor; 15 - device maintaining the rotation speed of the motor; 16 - meter pressure drop on CS; 17 - evaluator; 18 - meter output density.

The device operates as follows. The drawing shows one possible connection of the elements of the pump-motor 4, 6 - SU, 10 - stimulate consumption.

Circuit equipment 1, 2, 3, 4, 12, 13, 15 designed to maintain zero pressure drop ΔR≈0 on the measuring site 1 (on the pump-motor 4). Nonorgan 12 upon the occurrence of differential pressure on the pump-motor 4 sends a signal through the device 15 maintain the frequency of rotation of the motor shaft 13 to reduce the differential pressure. In this arrangement, the circuit responds to the change in the load pressure at the inlet 2 and outlet 3. The signal meter shaft speed of the motor 14 is fixed in the transmitter 17 to calculate the speed of flow of medium through the measuring section 1.

Controlled environment passes through the inlet pipe 11 through the pump 10, for example, centrifugal type, input 2 and the falls at the first measuring section 1 in the pump-motor 4. When the pressure exceeds inlet 2 over pressure output 3 negative signal by the pressure drop leads to an increase in the rotation speed of the pump-motor 4 for compensation signal by the pressure drop, with the positive sign of the differential pressure, the pump-motor 4 decreases the rotation speed to remove this signal. Thus, the pump-motor 4 operates in the zero difference at all rpm range.

Shaft rotation frequency of the pump-motor 4 connected to the shaft of the motor 13, is directly proportional to the fluid velocity passing through the pump-motor 4. Data on the frequency of rotation of the shaft of the motor is obtained from a measuring instrument 14 is transmitted to the computer 17 for processing the measurement results, transform, and obtain the desired form of the density of the medium.

The medium of plot 1 is pushed through the outlet 3 and the inlet 7 in the second measuring section 5, which is SU device 6, in which the measured pressure differential 16, and further to the output 8 of the device.

The data obtained by the pressure drop on SU and frequency of rotation of the pump-motor 4 or the rate of passage of the environment passed to the evaluator. If there are two simultaneously measured values produce the operation of calculating the density of the medium.

The first is the magnitude of the fluid velocity V passing through the first and the measuring section 1. Unreported leaks close to zero at zero differential on the pump-motor 4. The accuracy of the speed measurement high.

The volume of fluid per unit time of the pump-motor, becomes a known value that is directly proportional to the shaft speed of the controlled motor. I.e. the volume flow is equal to the unit volume (displacement) of the pump-motor multiplied by the rotational frequency f of the motor. Thus, the rotational speed of the shaft of the motor multiplied by a constant dimensional coefficient, and is the flow rate at the first measuring station. Next, the calculator 17 calculates the velocity V of the flow medium at the first site 1 is obtained from the volumetric flow rate Q by dividing the actual flow section F of the pump-motor. Get the speed V, is proportional to the rotation frequency f, via the ratio of V=K1f.

The second measured value is the pressure drop ΔP on the second measurement area obtained by SU meter 16. Received the information about the speed V in the transmitter 17 is further used to determine the magnitude of the density of the medium from the magnitude of the velocity head, equal to the value of the differential pressure on SU, at a known flow rate of the medium (calculated from the measurement data at the first measurement site) ΔP= ρV2.

Two values of the velocity of the medium, is proportional to the frequency f of rotation of the motor shaft, and the differential pressure ΔR, allow to solve the equation and obtain the density of the medium.

ρ=ΔP/K2V2=ΔP/K2K12f2.

The advantages of the proposed device purchased using the characteristics given in the characterizing part of the following formulas.

The introduction of an additional measurement station for receiving data from one and the other measuring sites of the two independent variables for the calculation of the dependency.

The combination of measurement methods: measurement of fluid velocity with high accuracy at zero differential pressure on the pump-motor according to the frequency of rotation of the shaft and measuring the velocity pressure of the medium by the method of alternating differential pressure on SU.

The flow measurement at zero differential pressure attached to the proposed technical solution the following benefits:

- significant expansion of the measurement range,

- there is no leakage at zero differential allows you to measure the speed with maximum and uniform accuracy over the entire measuring range,

- when measuring the speed environment is not subjected to compression and expansion, passing through the first measuring section,

- since the determination of the fluid velocity is carried is carried out using a volumetric pump-motor with zero differential, it provides a plug flow regime of the environment, such as gas-liquid mixtures,

- density is determined by calculating from the obtained data by the pressure drop from the other measuring station. When the calculation uses the same data volumetric flow rate as the flow speed of the medium by the first measuring section,

- proportional dependence of density on pressure differential for SU,

- determination of the density of the medium, it is at the moment zero differential pressure, eliminates amendments parameters (viscosity, pressure, temperature) and the environment

volume per 1 circulation pump is always the same and does not depend on the type of gas and liquid density, viscosity and temperature of the pumped medium, because the geometric volume of the circuit between the screws is always the same.

The hydrodynamic device measuring the density of the medium containing a narrowing device for measuring differential pressure, the output of which is connected with the transmitter, characterized in that in series flow entered the pump flow and contour maintain a zero differential pressure gauge differential pressure, the motor device maintain its speed and the pump-motor with the gauge of frequency of rotation of the shaft, the contour along with what smeltelim shaft speed associated with the computer for processing the measurement results, conversion and calculating the density of the medium.



 

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