US2911456A

US2911456A - Pyrometer

Info

Publication number: US2911456A
Application number: US559707A
Authority: US
Inventors: Volochine Theodore
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-11-23
Filing date: 1956-01-17
Publication date: 1959-11-03
Anticipated expiration: 1976-11-03

Description

T. VOLOCHINE Nov. 3, 1959 PYROMETER Filed Jan. 17, 1956 lNVE/VToR 77IEODORE VOL-OCH/NE 2,911,456 Patented Nov. 3, 1959 PYROMETER Theodore Volochine, Chevilly-Larue, France Application January 17, 1956, Serial No. 559,707

Claims priority, application Switzerland November 23, 1955 2 Claims. (Cl. 136-4) My invention has for its object a pyrometer or the like apparatus for receiving and measuring radiated thermal energy, of the type including a pile of thermocouples, the welds of which are distributed on the two opposlte sides of the pile, which latter is provided with a central body or core which is made of a good heat-conducting material and is adapted to absorb and to dissipate the calories first absorbed by the heat exposed Welds of the thermo-couples, a chamber surrounding entirely the thermopile with the exception of the area containing the heatreceiving welds. For the practical use of such an apparatus under satisfactorily efi'lcient conditions, said apparatus should fulfill the following conditions:

(a) it should be stable,

(b) it should operate independently of the ambient temperature and of the variations of said temperature,

(c) it should be highly sensitive,

(d) it should respond speedily.

The first two above-mentioned conditions are satisfied to a large extent by the special structure given to the most recent thermo-couple piles such as that described in the US. patent specification 2,565,105.

The apparatus according to my present invention has for its object to improve the conditions of stability and independence with reference to temperature and furthermore to satisfy the two last conditions of sensitivity and speedy response.

As a matter of fact, these conditions and d are not satisfied or are satisfied only to an imperfect extent by the conventional pyrometers. The latter include generally a mirror or a lens concentrating the heat radiations to be measured onto the heat-exposed welds of a thermopile. In the case of a mirror, a gate closed by a glass is provided for protecting the mirror. Thus, in both such embodiments, a large fraction of the heat radiations is absorbed by the glass or by the lens or is reflected thereby, which may detrimentally afiect the measures, the latter becoming erroneous if the lens or the glass is sullied during the operation, and what is more, this absorption or reflection of the heat radiations reduces the sensitivity of the apparatus and increases its inertia and consequently its delay of response.

The apparatus receiving and measuring radiated thermal energy according to the invention is characterized by the fact that it includes a tube provided with an inner reflecting surface, arranged in register with the axis of the heat-exposed welds and forming a collector of the thermal energy radiated into its outer end, said tube guiding said energy towards the heat-exposed welds while a casing surrounds the chamber containing the thermopile and the collecting tube, at least in the section adjacent the area inside which the heat-exposed welds are located and channels are formed in said casing so as to allow a cooling fluid to flow through them and to provide for constancy of the temperature of the chamber including the core and also of the adjacent section of the collecting tube.

Accompanying drawing illustrates diagrammatically and by way of example two preferred embodiments of my improved apparatus. In said drawing:

Fig. 1 is an axial cross-sectional view of the first embodiment.

Fig. 2 is a partial sectional view of the second embodiment which is a modification of the first embodiment.

My improved apparatus is similar to either apparatuses adapted to receive and to measure a radiated thermal energy, in so far as it includes a thermo-pile 1 constituted by a plurality of thermo-couples such as 2. Each thermocouple is constituted by two metal blades 3-4 connected at their cooperating ends through welds. These blades 3 and 4 are made of different metals or alloys such as manganine, on the one hand, and constantan on the other hand.

In the examples illustrated, the therrno-couples are of the type disclosed in the above mentioned United States Patent 2,565,105; in other words, each pair of blades 3 and 4 is secured to a solid member 5 which is a good conductor of heat, the blades 3 and 4 being fitted with said solid member 5 inside the central body or core 6 made also of a metal which is a good conductor of heat. Obviously, shims 7 of a material which is electrically insulating are inserted between the solid member 5 and the blades 3 and 4 on the one hand and on the other hand between said blades 3 and 4 and the core 6. A number of thermo-couples 2 are arranged in juxtaposed relationship and are electrically interconnected in series. The terminals 21 of the thermo-couples are connected through wires 22 with adjusting or controlling means or else with recording or indicating means constituted e.g. by a galvanometer, which means are not illustrated.

As shown, a housing 8 has cup-like wall sections fitted to opposite faces of the thermo-pile 1. These sections form separate chambers housing the hot weld 10 and cold Weld 20. One of the sections has an aperture 9 in registry with and facing the heat-exposed welds 10 of the thermo-pile. The other section which houses the cold weld is closed. The opening 9 is in a line with said hot welds and the throat portion 11 of a tube 12 secured to the section of the housing in the aperture 9. Said tube 12 has an inner reflecting surface 13 which forms a collector for the thermal energy radiated into the outer end 14 of the tube. As a matter of fact, the inner surface 13 of the tube forms a mirror protected against corrosion, for instance through a corrosion-resisting deposit of gold or the like metal. Geometrically and practically, this has for its consequence that said collecting tube 12 catches all the heat rays entering its opening 14, whatever may be their angle of incidence, the cosine law being thus applied. This tube 12 is thus a substitute for the lenses and protecting gates generally used in conventional pyrometers.

As apparent from inspection of the drawing, 15 surrounds the chamber 8 and the major part of the length of the collecting tube 12. Channels 16 are formed inside said casing 15 so as to provide for the flow of a cooling fluid around the housing 8 and the tube 12. An input opening 17 is provided in the casing 15 so as to allow connection between the latter and a flexible tube or hose feeding a cooling fiuid into the channels 16. Furthermore, the casing 15 is provided with a tubular outlet section 18 surrounding coaxially the collecting tube 12. The annular space 19 separating the collecting tube 12 from the wall of said tubular section 18 opens at its outlet port for the cooling a casing outer end so as to form an fluid.

The cooling fluid fed round the chambered housing 8 and the collector tube 12 inside the casing 15 has for its object to produce substantial constancy of the temperature of the chambered housing 8 and of'the central body 6 or core of the thermo-pile and also of the collector tube 12.

When the 'pyrometer thus constituted isoperatlve, the heat-exposed welds located on one of the surfaces of the pile absorb a certain amount of heat which is conveyed through the blades 3 and 4 towards the central portion of the thermo-pile 1. This heat is then dissipated within the central body 6 and thence transferred to the chambered housing 8. The fluid stream surrounding the chambered housing 8 carries along with it the excess heat thus applied to said chambered housing 8, as it appears in the latter. Consequently, the welds 20 which are the cold welds and which are located on the surface of the thermo-pile 1 facing away from the hot or heatexposed welds 10 are kept also at a constant low temperature;

In the example illustrated, the cooling fluid used is preferably constituted by a gasiform fluid such as air or the like. However, if the apparatus described is to serve for measuring heat in vacuo, the port formed by the annular space 19 may be closed and an output nozzle be provided at any suitable point of the casing 15. In this case, the cooling fluid may beconstituted either by a gasiform fluid or by water or the like fluid.

It is of advantage furthermore to resort to a diaphragm 23 as in the modification shown in Fig. 2, said diaphragm, made of a material which 'is a good conductor of heat, closing the collecting tube '12 at its inner end. Said dia: phragm 23 is located in a manner such as to be in heat conducting relationship with the heat-exposed welds 10. This diaphragm '23 is preferably blackened on its surface facing outwardly while its inner surface is coated with 1 an electrically insulating layer which allows however a good transmission of heat towards the heat-exposed welds 10. Such a diaphragm 23 may be constituted by a silver sheet or by a foil of aluminium oxidized on its inner surface, etc. 7

In the case which has just been disclosed, the speed of response of the apparatus is ensured through the three following advantageous features.

(1) The size given to the tube 12 and the arrangement of said tube 12 in the vicinity of the hot welds ensure efficiently the cooling of the latter as a consequence of the conductivity of the ambient air, which is held at a constant temperature by reason of the flow of fluid round the tube 12.

(2) The proximity of the hot welds 10 and of the cold welds 20 with reference to the core 6 having a large thermic capacity furthers the transfer of heat during the period of exposure to radiations as also in the absence of such radiations.

Q The apparatus described shows numerous advantages over all pyrometers of conventional structure. Thus, the cooling of the chamber 8 and of the collecting tube 12 provides for an increase in the stability of the thermopile and also in the stability of the surrounding media. As a matter of fact, the atmosphere of air or any other suitable gas surrounding the heat-exposed welds is kept at a constant temperature and there is no convectional movement of said atmosphere liable to produce irregularities in the measurements. a

Myimproved apparatus which allows cutting out the conventional lenses or protecting gates leads to a substantial improvement in sensitivity. I

This apparatus allows furthermore measuring heat in atmospheres subjected to an overpressure. As it can be executed in extremely reduced sizes, it may be located quite close the hot source of which the temperature is to be measured and it may even be in almost contacting relationship with said source of heat. Thus, the apparatus may be housed inside heat machines such for instance as gas turbines for which the operative temperature is critical and should in no case be higher than a predetermined upper limit.

For instance, my improved apparatus may be located in the vicinity of the output of the combustion chamber of a reaction jet engine in a manner such that its collecting tube may catch the radiations produced by the blading of the turbine distributor. In this case, a certain amount of air is shunted off the compressor of the reaction jet engine with a view to using it as a cooling fluid for the apparatus after which it is introduced into the combustion chamber through the annular port 19. Such an arrangement allows obtaining an instantaneous measure of the temperature at the points of the distributor which are the most exposed to heat while ensuring a complete protection of the thermo-pile with reference to carbonaceous deposits such as are formed through the combustion of the fuel.

(3) The arrangement of a blackened metal diaphragm 23 over the hot weld 10 produces a thermic contact with the chamber '8 and the tube 12 whereby the speed of response of the thermo-pile is still increased.

In the examples illustrated, the heat collecting tube 12 is of a geometrical cylindrical shape. Howevensaid tube 12 may as well be slightly frusto-conical or in the shape of any desired body of revolution.

In a modification, the casing 15 instead of surrounding the tube 12 through the major part of its length may surround only the portion of said tube 12 which lies near the chamber 8. The cooling of this portion of the tube 12 is sufficient for cutting out an exaggerated heating of the area 9 surrounding the heat-exposed welds 10 whereby the air is prevented from assuming a convectional movement round said hot welds 10.

One of the numerous other fields of application of my improved apparatus consists in measuring the temperature of very accurately defined areas on parts or on walls of a furnace inside a furnace operating in an atmosphere of a protecting gasiform fluidor under pressure.

What I claimis: I

1. A Pymmeter free of lenses, comprising a thermocouple having a heat-sensitive terminal, a housing for said thermocouple closed at all sides except for an opening adjacent said heat-sensitive terminal, a heatcollecting tube having its axis disposed coaxially with the axis of said opening and having its inner end opening onto said heat-sensitive terminal, said tube having the shape of a selected body of revolution and provided with an internal reflecting surface for collecting heat rays entering its outer end regardless of their angle of incidence, and a casing internally spaced from said housing to provide circulating space and including an air inlet and an air outlet surrounding said tube. g

2. A pyro meter'according to claim 1 wherein a dia phragm is interposed between the inner end of the tube and the heat-sensitive terminal. 7

* References Cited in the file of this patent UNITED STATES PATENTS 1,089,743 Brown Mar. 10, 1914 1,318,516 Wallis et a1. Oct. 14, 1919 1,714,664 Foster May 28, 1929 2,526,112 Biggle Oct. 17, 1950 2,565,105 Volochine Aug. 21, 1951