RU2098771C1 - Method for measuring powder-like medium flow rate - Google Patents

Abstract

FIELD: instrumentation engineering; power industry. SUBSTANCE: powder-like medium flow is balanced by counter gas flow from excess pressure source in two pressure checkers of different parameters and flow rate is determined by pressure difference between gas spaces in checkers. EFFECT: higher efficiency. 1 dwg

Description

 The invention relates to instrumentation and can be used in energy and other industries.

A known method of measuring the flow rate of a powdery medium, which consists in the formation of acoustic vibrations in a controlled medium and determining by measuring the frequency of acoustic vibrations the speed of movement of the powdery medium, and by changing the amplitude of the amount of material [I]
The disadvantage of this method is the low accuracy of the measurements, due to the ambiguous relationship of changes in the frequency and amplitude of acoustic vibrations, respectively, with the speed of movement and the amount of material.

The closest analogue of the invention is a method of measuring the flow rate of a powdery medium, which consists in balancing the powdery medium with a counter flow of gas from a source of stabilized overpressure in the cavity of the pressure head, introduced counter-flow into the flow of the controlled powdery medium and determining the flow rate of the latter by the level of its entry into the pressure head [2]
The technical result of the invention is to improve the accuracy and reliability of measurements.

 This is achieved by the fact that in the method of measuring the flow rate of the powdery medium, which consists in balancing the powdery medium with a counter flow of gas from a source of overpressure in the cavity of the pressure head, introduced counterclockwise into the flow of a controlled powdery medium and determining the flow rate from the parameters of the medium in the pressure head, simultaneously balance the powdery medium with the same counter flow of gas in the cavity of the second pressure nozzle with different geometric dimensions introduced by Normally the stream in a controlled environment, and in determining the flow powdery medium determined pressure differential between the cavities with a gas pressure in the two nozzles.

 The method of changing the flow rate of the powder medium is implemented by the device shown in the drawing.

 The device contains pressure nozzles 1,2, the lower cavities of which 3, 4 are in communication with a differential pressure meter 5 and an overpressure source (not shown). Pressure nozzles are made in a single housing and introduced counter-through the wall of the pipe 6 into the flow of a powdery medium.

 The operation of the device is as follows. The source of excess gas (air) pressure generates gas flows in nozzles 1,2. Moreover, the working condition of the device is the selection of the initial gas flow rate, which determines the flow of powdered medium into the upper parts of the nozzles 1,2.

где
m₁ и m₂ массы частиц соответственно в насадках 1,2;
ρ_тв, V_тв соответственно плотность и скорость частиц;
ΔP₁, ΔP₂ перепад давлений на частицах соответственно в насадках 1,2;
f₁, f₂ суммарное эффективное сечение частиц в насадках 1,2;
Φ₁, Φ₂ коэффициенты сопротивления на частицах в насадках 1,2;
V₁, V₂ скорости газа в насадках 1,2.With an increase in the controlled flow rate, the amount of the supplied powdery medium in nozzles 1.2 increases, and with a decrease, it decreases accordingly. Subject to the equality of forces acting on particles of a powdery medium, the simplified equations for nozzles 1,2 have the form:

Where
m ₁ and m _{2 the} mass of particles, respectively, in nozzles 1,2;
ρ _tv , V _tv, respectively, particle density and velocity;
ΔP ₁ , ΔP ₂ differential pressure on the particles, respectively, in the nozzles 1,2;
f ₁ , f ₂ total effective section of particles in nozzles 1,2;
Φ ₁ , Φ ₂ drag coefficients on particles in nozzles 1,2;
V ₁ , V ₂ the gas velocity in the nozzles 1,2.

 After subtracting and transforming the equations, we obtain a relation from which it follows that the mass difference of the powdery medium in the internal cavities of the nozzles is proportional to the pressure difference between the cavities with gas and two pressure nozzles.

где
Δm_1,2 разность масс порошкообразной среды во внутренних полостях насадок;
ΔP перепад давлений между полостями с газом в двух напорных насадках;

разность скоростей газа в насадках;
P₀ давление в контролируемой среде;
Φ коэффициент сопротивления на частицах в насадках.

Where
Δm _1,2 the mass difference of the powdery medium in the internal cavities of the nozzles;
ΔP pressure difference between the cavities with gas in two pressure nozzles;

gas velocity difference in nozzles;
P ₀ pressure in a controlled environment;
Φ is the drag coefficient on the particles in the nozzles.

 In other words, with an increase in flow rate, the mass of particles in each of the nozzles increases, but since the geometric dimensions of the nozzles 1,2 differ, the degree of receipt (mass) of the powder in the nozzle also differs for each nozzle. With the flow of air (gas) coming from one source of overpressure, the air velocities in each nozzle will differ (since the hydraulic resistance of the powder column in the two nozzles is different).

 By measuring the pressure difference between the cavities of the nozzles, information is obtained on the mass of powder in the nozzle, i.e. about mass flow. In addition, the measurement of the differential pressure simplifies the design of the device that implements the method and increases its reliability, as it eliminates the possibility of contact of the measuring elements with a controlled environment.

Claims (1)

 A method for measuring the flow rate of a powdery medium, including balancing the powdery medium with a counter flow of gas from a source of overpressure in the cavity of the first pressure nozzle introduced counterclockwise into the flow of a controlled medium, and determining the flow rate using the parameters of the medium in the pressure head, characterized in that the powdery medium is simultaneously balanced by the same gas flow in the cavity of the second pressure nozzle with different parameters from the first one, introduced counter-flow into the flow of the controlled medium, and when determining the flow rate, the pressure difference between the cavities with gas in two pressure nozzles is determined.