SU1372200A1 - Gas temperature measuring device - Google Patents

Abstract

The invention relates to thermometry and permits an increase in the measurement accuracy and an extension of the range of measurable fluids. In the water-cooled housing 1 there are flow channels, made in the form of pipes 2 and 3 of constant diameter, adjoining behind the working section of the device with pipe 4 of the suction line. The T-rails of the walls of pipes 2,3 and the gas in them are determined by thermal converters 6.7, which are moved to the cross-sections of the entrance of the pipes, and the moment when the readings of the thermal converter 6, located in pipe 2, approach the beginning of spreading ash fuels. Thermal converters 6, 7 are placed on the axis f of pipes 2 and 3, the diameters of which differ at least twice, at an equal distance from their input ends. 2 sludge. with

Description

FIG. 2

The invention relates to thermometry and can be used to measure the temperature of a gas,

The aim of the invention is to improve the measurement accuracy and expand the range of measured temperatures.

Figure 1 shows a device for measuring the temperature of a gas, a general view; figure 2 - section aa in figure 1 (in the area of the work area).

The device comprises a water-cooled case 1, a pipe 2 of the first flow channel, a pipe 3 of the second flow channel, a pipe 4 of the suction line, a pipe 5 of the installation channel and thermocouples 6 and 7 made, for example, on the basis of thermocouples, the thermocouple 6 located in pipe 2 of the first flow channel, and the thermocouple 7 is located in the pipe 3 of the second flow channel. The distances from the input end of the pipe 2 to the cross section of the installation of the thermal converter 6 and from the input end of the pipe 3 to the cross section of the installation of the thermal converter 7 are equal.

The pipe 2 of the first flow channel and the pipe 3 of the second flow channel behind the working section of the device are connected by pipe 4 of the suction line.

The diameter of the pipe 2 is more than 2 times the diameter of the pipe 3.

The device works as follows.

Thermal converters 6 and 7 are pushed to the maximum depth of the working section, then cooling is turned on and a device for measuring temperature is entered into the test zone of the furnace or combustion chamber, where the gas temperature is about 2000 K. Record thermometer 6 and 7, which determine the temperature of the pipe walls 2 and 3 suction channels, since in the absence of suction the gas temperature in the suction channels is equal to the temperature of the cooled walls.

Suction is turned on, at which the measured gas flows through pipes 2 and 3 of the suction channels with a speed of 70–80 m / s and the gas temperature decreases along the length of the suction channels due to intensive cooling.

Thermal converters 6 and 7 move to the inlet sections of pipes 2 and 3 of suction channels. Until the thermal converter 6 reads

The stroke of the larger diameter pipe 2 does not come close to the temperature at which the ash begins to soften of this fuel. Then, readings of thermocouples 6 and 7 are taken and retf is determined according to a known relationship.

Thermocouples 6 and 7 measure the temperature of the gas in the pipes 2 and 3 of the suction channels at their installation sites.

Gas through pipes 2 and 3 suction channels enters the pipe 4 suction pipe.

Heat transfer in the flow channel is described by the dependence

d); 6; 0, - exp - (4- St (x) dxJ,

L 0 (1)

where br is the excess temperature of the gas above the wall temperature; 6; - exceeding the gas temperature at a distance x from the entrance to the suction channel over the wall temperature;

St (x) 6C, (x) / (pWCp), where “to (x) is the local coefficient of heat transfer from the gas to the channel wall; p is the gas density; W is the gas velocity in the canape; C is the specific heat of gas,

At constant diameter along the length of the channel, expression (1) can be written

 9; 9, exp - St (x) dxl (2

about

or for sections of two suction channels of different diameters with the same value of x

9, 0

exp

| | | st (x) (3)

e, in g exp - -g- J St (x) cbc. (3) The magnitudes of the integrals (St (x) dx in

formulas (З) and (З) are equal to each other.

Divide (h) by (W) and build both sides of the resulting equation in,

degree d / (d, - d):

e, 7

 --еГ

exp -j-j St (x) dx.

(four)

Substituting (4) into formula (3), we obtain an equation that allows to determine 9 g:

, (-l -} (5)

The effect of the magnitude on the total error in the measurement of the temperature ha for an is determined by the formula

Sir b.S T, + b.ST + b, 5 (d, / d.i),

(in

hundred

where o T; - relative error of temperature measurement T ;; d (d, / d) - relative error

setting the values of d, / dj; b; - influence coefficients, в-. lcdies partial derivatives of the function Tg (T ,, T,. In this case

B

 five

in

 ABOUT

.

20

At the same time, an error 51 over 27 is guaranteed to be provided with d, / dj 2.

Thus, a practically acceptable range of ratio is

2 . 20.

From the specified range of d, / d values, the value of 2 has the advantage, since it allows us to simplify the formula for determining T (5) and reduce it to form (6), which simplifies the procedure for determining T (there is no need to raise the value in brackets in formula (5).

Accepted in d, / di 2, a calculation formula is obtained for determining T,.:

Coefficients b ,, b, b, decrease

from oo to o at 1 00.

i Maximum ratio value

d, / d2 is determined by the practical feasibility of the device.

Having a larger diameter of the device equal to 20 mm, it is practically possible to realize the diameter of the smaller channel at least I mm, otherwise the temperature measurement in it is difficult (the diameter of the thermocouple should not exceed 10 μm). Almost di / d is difficult to implement more than 20.

Formula

A device for measuring the temperature of the gas, comprising a housing, two parallel flow channels with different hydrodynamic resistances and two identical thermal converters placed on the axis of the flow channels at an equal distance from their input ends, in order to increase the accuracy measuring and extending the range of measured temperatures, the casing is made water-cooled, and the flow channels are made in the form of pipes of constant diameter, and the ratio of the diameters of the pipes of the flow channels differs not m her than doubled.

Fy

Claims (1)

Claim A device for measuring gas temperature, comprising a housing, two parallel flow channels with different hydrodynamic resistances and two identical thermocouples placed on the axis of the flow channels at an equal distance from their inlet ends, characterized in that, in order to improve the measurement accuracy and expand the range of measured temperatures , the casing is made water-cooled, and the flow channels are made in the form of pipes of constant diameter, and the ratio of the diameters of the pipes of the flow channels differs no less than m twice. FIG. 1