SU726428A1 - Variable cross-section converging element - Google Patents

Description

The invention relates to a measuring technique and can be used, in particular, to measure the flow rate of a medium in rectangular channels with variations in the temperature of this medium. Devices for measuring the flow rate of the medium are known in which the area of the orifice of the diaphragm automatically changes as the temperature of the medium changes so that the flow measurement results do not depend on the change in TeMnepaTSTJbi 1. In these devices, the aperture area of the diaphragm changes when the correction needle is moved, and the axis is fixed on the tightening lid of two bellows. In the space between the two bellows there is a portion of the gas of the same composition as the measured one. The change in gas temperature will be perceived by the gas enclosed between the bellows and cause the correction needle to move so that the orifice area of the diaphragm varies in proportion to Vf, where T is the temperature of the measured gas in Kelvin radii, i.e. const, where F. is the area of the orifice area of the restriction device. This is achieved by appropriate profiling of the correction needle. However, these devices have a complex structure and can work only in conditions of completely pure and non-aggressive media. The purpose of the invention is to eliminate these drawbacks. The goal is achieved in that the restriction element is designed as a nozzle formed by two bimetallic plates fixed at its ends opposite sides of the measuring channel with a gap relative to two other sides, with the active layers of the plates facing the nozzle axis, and the length of the plates is chosen from the ratios Γ fe.s W. L'toK-s,) is the plate length ;, is the plate thickness;

TQ - calculated (nominal)

gas temperature;

L - calculated (nominal)

wide passage section

nozzles corresponding to the coefficient of thermal linear expansion of the passive layer;

. with JI, the thermal linear expansion coefficient of the active layer.

Fig; 1 and 2 are schematic diagrams of a variable section restriction element.

It contains plates 1 that form a smoothly tapering element (nozzle) 2, fixed, on opposite sides of channel 3, which is rectangular in cross section with a two-sided T f Hx c TopoH, which allows the plates to be bent as the temperature changes. ;

The active layers of the plates 1 are facing nozzles, and the length of the plates is chosen from the condition. R

  const,

 ir

where F is the area of the orifice of the converging element (nozzle); T is the temperature of the measured gas in degrees Kelvin.

Narrowing element works as follows.

The active layers of the plates are reversed k6d7p (the Stoyu area of the nozzle junction through passage increases as the temperature of the flowing

environment. . ,, .-. , ...., ... ,, ,, .... ...,

To comply with the terms independent. Most of the flow versus temperature, the length of the plates is chosen according to the approximate formulas; ::: ;; - :::; ; : v ::,. ::.; ..., ..,. 1

  -Za const, .., VT. . fr

- calculated (nominal)

F., the area of the nozzle section ;.

(rated)

TQ is the calculated gas temperature,:.

yes

  . - - -. i .-, -

) -

a.fe

temperature change T T - T, tours

  and the height of the nozzle; L is the calculated (nominal) width of the passage section of the cross section at T (the bimetal deflection is

726428

(deviation of the free end of the plate from the calculated

(nominal) position).

Because

3 ()

Lt

--four

(X is the coefficient of thermal linear expansion of the passive layer;

c is the coefficient of linear thermal expansion of the active layer; C is the length of the plate; S is the plate thickness

., g

7rir-b5-b: ±: il:

uiT,

 Sb

Expanding the left side of the equality in the Taylor series and limiting it to the first two terms, we get:

.i.i,. | biid. ,,

 O2g.g,

or"

CL e.-s -y b (x,

Claims (1)

1. Kremlin PP, Flowmeters and quantity counters. 1975, p. 119-120 (prototype). +) lue /