RU2133028C1 - Gear measuring temperature of flame in zone of combustion of fuel sample - Google Patents

Abstract

FIELD: equipment testing combustible materials. SUBSTANCE: invention refers to gears measuring temperature T_coms of gas in zone of combustion of fuel sample burning in parallel layers, for instance, of polymer composite material. Gear has combustion chamber that houses fuel sample and light conductor which input ends borders on front end face of fuel sample, radiation pyrometer abutting on output end of light conductor and register. Combustion chamber is gas-tight and fuel sample is placed in armored sleeve. Polymer composite material including alkali metal is used in the capacity of fuel sample. Light conductor is produced from material sublimating in zone o combustion with rate of burning of fuel sample made from acrylic plastic, for example, and is placed in side sample along axis of the latter. Input and output of light conductor are arranged on sides of open and armored end faces of fuel sample. Plane of input section of light guide is aligned with plane of front end face of fuel sample. Spectropyrometer with working length of wave equal to that of wave of saturated central part of spectral line of alkali metal is used as radiation pyrometer. EFFECT: realization of continuous output of radiation from central part of saturated spectral line of alkali metal to optical system of specropyrometer in process of movement of zone of combustion which provides for measurement of temperature of flame in zone of combustion. 1 cl, 2 dwg

Description

The invention relates to techniques for testing combustible materials, and in particular to devices for measuring the temperature of a gas T _g in the combustion zone of fuel samples burning in parallel layers, for example, polymer composite material (PCM).

 Closest to the claimed solution is a device for measuring the temperature of the combustion products in the combustion zone, containing a combustion chamber with a sample of fuel and a light guide, the input end of which is adjacent to the front end of the fuel sample, a radiation spectropyrometer, the lens of which is located opposite the output end of the light guide, and registrar [1].

 The features of the prototype, which are common with the claimed invention, include a combustion chamber with a fuel sample and a light guide, a radiation spectropyrometer and a recorder.

The reason that prevents obtaining the required technical result in the prototype is the low information content, because for one test of a fuel sample, only one value of the gas temperature T _g in the combustion zone is determined, the corresponding pressure of the medium P _c in the combustion chamber, which does not allow to correctly assess the non-uniformity of the temperature T _g during the combustion of the sample. It should also be noted the complexity and low reliability of the registration of the measuring signal during flame pyrometry with small values of the emissivity ε _λ .
The invention consists in the following.

 The invention is aimed at solving the problem of creating a device that allows you to determine the gas temperature directly in the combustion zone of a fuel sample and find out the causes of uneven combustion of fuel samples.

 The technical result, which mediates the solution of this problem, consists in the continuous output of radiation from the central part of the saturated spectral line of an alkali metal to the optical system of the spectropyrometer in the process of moving the combustion zone and thereby provides measurement of the flame temperature in the combustion zone.

 This technical result is achieved in that the device comprises a combustion chamber with a fuel sample placed therein and a light guide, the input end of which is adjacent to the front end of the fuel sample, a radiation spectropyrometer adjacent to the output end of the light guide; the recorder, the combustion chamber is sealed, the fuel sample is placed in an armored glass, a polymer composite material including alkali metal is used as fuel, the light guide is made of material sublimating in the combustion zone at a speed equal to the burning rate of the fuel sample, for example, from plexiglass and installed inside the sample along the axis of the latter with the location of the entrance and exit of the light guide from the open and armored ends of the fuel sample.

 In FIG. 1 is a structural diagram of a device for measuring flame temperature in a combustion zone. In FIG. Figure 2 shows the waveforms of the signals of the spectropyrometer (curve 1) and the timer (curve 2).

The device contains a fuel sample 1 with an optical fiber 2 installed along its axis, and the sample is coated on the side surface with an armor coating 3, with the exception of the front end, and is placed in a large volume combustion chamber 4 filled with an inert gas under a certain pressure P _s . Pressure P _{s is} monitored by pressure sensor 5 (for example, type LH-410). A spectropyrometer 6 is located on one optical axis with a light guide 2, the optical system of which senses a radiation flux Φ _iλ coming from the light guide 2. A spectropyrometer 6 and a pressure sensor 5 are connected to separate inputs of a multi-channel recorder for 8 s through a strain gauge 7 (for example, type LX-7000) a timer (for example, a light-beam oscilloscope of the type N-700). The registrar records in time the signals of the spectropyrometer h _ic = f (t), the pressure sensor h _ig = f (t) and the timer in the form of a sinusoidal curve with a period of Δ = 0.02 s (Fig. 2).

 The device operates as follows.

When an open (front) surface of a fuel sample is ignited with a PCM, the process of burning the sample in parallel layers begins, in which the combustion front, remaining perpendicular to the axis of the sample, moves to the left. When the combustion front reaches the front end of the _fiber made of plexiglas, the radiation flux Φ _0λ from the saturated central part of the spectral line with a wavelength λ of an alkali metal, for example, sodium, is output in the form of a flux Φ _iλ to the optical system of the spectropyrometer 6. Production stream
Φ _iλ = Φ _i0λ • τ _iλ = τ $\genfrac{}{}{0ex}{}{\text{li}}{\text{1λ}}$ • Φ _i0λ , (1)
where τ _iλ is the current value of the transmittance of the optical fiber with a length l _i at a wavelength λ;
τ $\genfrac{}{}{0ex}{}{\text{li}}{\text{1λ}}$ - transmittance of a layer of a single thickness of the light guide at a wavelength λ. The value of τ _1λ in the visible region of the spectrum for plexiglass of the SOL and CT2 grades is 0.91 with a plexiglass layer thickness of 10 mm [2];
l _i - the current value of the length of the light guide.

The flux Φ _iλ forms at the output of the spectropyrometer a proportional electric signal displayed on the waveform in the form of deviations h _ic from the zero line registered on the phototape in the absence of flux Φ _iλ .
Plexiglas of the SOL and CT2 grades at high temperatures in the PCM combustion zone (1500 ^° C and above) sublimate (bypassing the melting stage) with the formation of gaseous products that clean the surface of the light-receiving end of the light guide from pollution. Due to the low thermal conductivity, PCM sublimes only a thin layer of the light guide located in the reaction layer of the fuel, where the combustion process actually proceeds. At the same time, plexiglass, as an optical material, retains its transparency in the process of fuel combustion. However, the transmittance of the optical fiber τ _iλ due to the continuous shortening of the fuel sample changes (increases), which distorts the optical flux entering the optical system of the spectropyrometer. Instead of the flux Φ _i0λ , the attenuated flux Φ _iλ enters the optical system, forming a reduced deviation h _ic , which, if no measures are taken, will lead to an underestimation of the measured temperature.

To eliminate this drawback, it is necessary to correct the obtained value of h _ic by multiplying it by a coefficient
a _i = 1 / τ _iλ = 1 / τ $\genfrac{}{}{0ex}{}{\text{li}}{\text{1λ}}$ , (2)
those. define h _ib = h _ic • a _i . (3)
With the calibration dependence spektropirometra h = f (T), where h and T - h, respectively, and beam deflection temperature T blackbody model (blackbody) can be meaningfully determine h _in dependence on the calibration value of the flame temperature, T _g = T.

The current value of the length of the optical fiber l _i corresponding to the time t _i in the process of burning the sample and substituted in (2) can be determined as follows.

Denote:
t _beg , t _con - time points corresponding to the beginning and end of combustion of the fuel sample;
Δt _i = t _i - t _beg is the burning time of the fuel sample corresponding to the time t _i ;
Δt = t _beg - t _con - the total burning time of the sample;
l _beg , l _con , l _i - values of the initial, final and current length of the light guide;
Δ _{arr. i} = l _{arr. beg.} - l _{arr. i} is the shortening of the sample corresponding to the time t _i ;
l _{arr. beg} , l _{arr. con} , l _{arr. i} - values of the initial, final and current length of the sample without taking into account the thickness of the armor coating;
Δl _i = l _beg - l _i - shortening of the LED corresponding to the time t _i , and
Δl _i = Δl _arr . _I ; (4)
v is the burning rate of the fuel.

причем l_{обр. кон} = 0.Then
l _i = l _beg - Δl _i , (5)
Where
Δl _i = V • Δt _i , (6)

with l _{arr. con} = 0.

The value of l _i obtained from (5) is substituted into (2) and a _{i is found} , and then, according to (3), h _{in is} calculated, from which the flame temperature T _g = T is found from the calibration curve.

List of used literature:
1. Kharazov V. G. Automation of high-temperature processes. - L .: Energy, 1974.

 2. Melnikov Yu.F. Lighting materials. - M .: Higher school, 1976.

Claims (2)

 1. A device for measuring the temperature of a flame in the combustion zone of a fuel sample, comprising a combustion chamber with a fuel sample and a light guide, the input end of which is adjacent to the front end of the fuel sample, a radiation spectropyrometer adjacent to the output end of the light guide, and a recorder, characterized in that the combustion chamber is sealed, the fuel sample is placed in an armored glass, a polymer composite material including alkali metal is used as fuel, the light guide is made n of material sublimating in the combustion zone at a speed equal to the burning speed of the fuel sample, and installed inside the sample along the axis of the latter with the location of the entrance and exit of the light guide from the open and armored ends of the fuel sample, the plane of the input section of the light guide aligned with the plane of the front end of the sample fuel, the working wavelength of the spectropyrometer is equal to the wavelength of the saturated central part of the spectral line of the alkali metal.  2. The device according to p. 1, characterized in that the light guide is made of plexiglass.

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