FR3075877A1 - SYSTEM FOR DETECTING A TEMPERATURE FAULT IN THE INTER-VEIN COMPARTMENT OF A DOUBLE FLOW TURBOREACTOR - Google Patents

Abstract

The invention lies in the field of monitoring the state of an aircraft and, more specifically, the state of a turbojet engine equipping the aircraft. It relates to a turbofan engine (10) equipped with a system (30) for regulating the turbojet engine and for detecting a temperature anomaly in the inter-vein compartment. According to the invention, the regulation and detection system (30) comprises a thermocouple (22), a cold junction temperature sensor (23) and a calculator (21), a hot welding (223) of the thermocouple (22). being positioned in a primary vein (14) of the turbojet engine and two cold welds (224, 225) of the thermocouple being positioned in an inter-vein compartment (132). The cold junction temperature sensor (23) is positioned in the inter-vein compartment (132) in the vicinity of the cold welds (224, 225). The computer (21) is positioned in a blower compartment (111). It is arranged to determine, on the one hand, a temperature in the primary vein (14) as a function of a tension between the two cold welds and a temperature measured by the cold junction temperature sensor (23) and, on the other hand, to determine a temperature anomaly in the inter-vein compartment (132) as a function of the temperature measured by the cold junction temperature sensor (23).

Description

SYSTEM FOR DETECTING A TEMPERATURE ANOMALY IN THE INTER-VEIN COMPARTMENT OF A DUAL-FLOW TURBOREACTOR

DESCRIPTION

TECHNICAL FIELD The invention relates to the field of monitoring the state of an aircraft and, more precisely, the state of a turbojet engine fitted to the aircraft. It relates to a turbofan engine, therefore comprising a primary flow stream and a secondary flow stream, equipped with a regulation system and a temperature anomaly detection system in the inter-vein compartment separating the primary vein of the secondary vein. The invention makes it possible in particular to detect a fluid leak in the inter-vein compartment of the turbojet engine on the basis of a change in temperature within the compartment.

PRIOR STATE OF THE ART

A turbojet engine comprises a fluid distribution system to perform numerous functions within the turbojet engine and even more generally in the aircraft. In particular, the fluid distribution system makes it possible to ensure the cooling of the different turbine stages from air samples from the compressor, to defrost the nacelle, to power the starter of the turbojet engine, or even to regulate the air pressure inside the aircraft cabin. To achieve these various functions, the fluid distribution system includes a large number of pipes, some of which can be housed at least in part in compartments of the turbojet engine. Certain fluids circulating in these pipes very often have a high temperature and pressure. The temperature of the fluid is typically greater than 100 ° C., or even greater than 500 ° C., and its pressure can exceed 10 bars.

The pipelines being subjected to severe thermomechanical stresses, they are liable to present leaks, resulting for example from cracking or disarming of the pipe. Not only are these leaks likely to cause a malfunction of the system supplied by the pipe, but they also risk damaging the turbojet engine, due to the high temperature of the fluid. This is particularly the case for a leak occurring in the inter-vein compartment of a turbofan engine. This compartment accommodates heat-sensitive equipment, in particular sensors intended to inform the full electronic authority digital engine regulation system, commonly called "FADEC", according to the English name "Full-Authority Digital Engine Control". In addition, the inter-vein compartment is likely to include structural elements whose mechanical properties are affected by an increase in temperature. In particular, elements made of aluminum or of composite material can exhibit low resistance at high temperatures.

Consequently, safety rules require that the appearance of fluid leaks in the fluid distribution system, in particular within the compartments, including the inter-vein compartment, be monitored. A first solution consists in placing a dedicated sensor in the compartment to be monitored and detecting any abnormal change in the measured parameter. In particular, a temperature sensor can be used to monitor an abnormal rise in temperature, which generally results from a leak of fluid at high temperature. This solution is for example described in the document US 2010/043540 A1. In order to more quickly detect the appearance of a fluid leak in a turbomachine compartment, it has been proposed, in the document FR 3 021350 A1, to determine a variation of the temperature between two instants and to compare this variation with a threshold. Since temperature sensors have a certain inertia, it has also been proposed, in document FR 3 031 141 A1, to measure a pressure or a pressure variation in the compartment and to compare this measurement with a threshold. In each of these solutions, at least one dedicated sensor is necessary to detect an increase in temperature or pressure and to deduce a fluid leak in the compartment. The introduction of additional sensors has a negative impact on the mass and cost of the turbojet engine.

Another solution is to monitor the pressure within the pipes of the fluid distribution system. Some lines, such as the air intake lines of the aircraft, are fitted with pressure sensors. A drop in pressure in the pipeline can then be easily detected and associated with the presence of a fluid leak. However, not all pipes are fitted with a pressure sensor and systematic installation would entail significant additional costs. It is also possible to analyze the consequences of a leak on the systems supplied by the fluid. For example, when a burst pipe occurs, it increases the temperature of the exhaust gas (EGT) due to the additional air intake imposed on the engine. The increase in the temperature of the ejection gases is all the more important as the flow rate of the leak is high. Monitoring logic may consist of monitoring the temperature in comparison to the level of power supplied by the engine. However, this solution has the drawback of relying on measurements which do not always have great precision. A compromise is thus to be found between a sufficient detection rate and a limited false alarm rate. In practice, this solution is only applicable for the detection of large leaks.

Yet another solution is to use fire detection sensors. However, these sensors are not always positioned appropriately for the detection of a fluid leak. These sensors are generally positioned near the weakest elements thermally, for example computers, or near sources of fire, for example fuel lines. They can be relatively far from high temperature fluid lines. As a result, the leak may be detected late and some equipment or structural elements may be damaged.

In view of the above, the invention aims to provide a solution for detecting a temperature anomaly in the interveins compartment before this anomaly causes damage in the turbojet engine, while limiting the impacts in terms of size. , weight and costs. The invention also aims to provide a solution whose design, manufacturing and maintenance costs are compatible with use on an industrial scale.

PRESENTATION OF THE INVENTION For this purpose, the invention proposes to deport the cold solders of a thermocouple and the associated cold junction temperature sensor in the inter-vein compartment, in order to use the measurement provided by this temperature sensor. of cold junction as information relating to the temperature within the inter-vein compartment. A cold junction temperature sensor originally has the function of providing a reference temperature measurement, namely a temperature at the level of the cold welds, in order to deduce therefrom the absolute temperature of the hot junction of the thermocouple. The remote cold junction temperature sensor in the inter-vein compartment then performs a dual function. It should be noted that the absolute temperature of the cold welds is not useful information as such. Thus, the position of the cold junction temperature sensor can be determined only according to the need for measurement in the inter-vein compartment.

The principle of a cold weld offset and the associated cold weld temperature sensor has already been described in application FR 3 027 106 A1. This application describes a probe for measuring the temperature of the gases leaving an helicopter gas, in which the cold welds and the cold weld temperature sensor are housed in an insulated housing, positioned relatively close to the hot weld. This housing has a connector for electrically connecting the cold welds to a remote processing unit via conventional cables. This offset from the cold welds has the advantage of shortening the length of the electrical conductors produced from a pair of specific materials. The present invention is based on this principle of cold weld offset and further proposes to use the measurement of the temperature of cold welds to detect a temperature anomaly in the environment of these cold welds.

More specifically, the subject of the invention is a dual-flow turbojet engine comprising a primary vein, a secondary vein, an inter-vein compartment separating the primary vein from the secondary vein and a blower compartment externally delimiting the secondary vein, the turbojet engine comprising in addition a system for regulating the turbojet engine and a system for detecting a temperature anomaly in the inter-vein compartment. The control system includes a thermocouple, a cold junction temperature sensor and a computer. The thermocouple includes a hot weld positioned in the primary vein and two cold welds positioned in the inter-vein compartment. The cold junction temperature sensor is positioned in the inter-vein compartment in the vicinity of the cold welds. The computer is positioned in the blower compartment and is arranged to determine a temperature in the primary stream as a function of a voltage between the two cold welds and a temperature measured by the cold weld temperature sensor. The temperature anomaly detection system comprises a processing unit arranged to receive the temperature measured by the cold junction temperature sensor and to determine a temperature anomaly in the inter-vein compartment as a function of said measured temperature.

The turbojet engine regulation system is for example a digital electronic full engine control system, commonly called "FADEC", according to the English name "Full-Authority Digital Engine Control". The processing unit of the temperature anomaly detection system can be integrated into the computer of the turbojet engine control system, also called the engine computer. In other words, the computer of the turbojet regulating system can integrate the function of detecting a temperature anomaly.

In a conventional control system of a turbojet engine, the cold junction temperature sensor is positioned in the blower compartment and, more precisely, at the level of the cold welds connecting the pair of electrical conductors of the thermocouple to the computer of the control system of the turbojet. In a turbofan engine according to the invention, on the contrary, it is necessary that the cold welds and the temperature sensor associated with them are removed from the blower compartment to be positioned in the interveins compartment, in order to provide a measurement of the temperature in this compartment. The temperature sensor thus performs a dual function, namely to provide a reference (or compensation) temperature for the turbojet regulating system and to provide a useful measurement of the temperature in the inter-vein compartment for the detection system. a temperature anomaly in the inter-vein compartment. A consequence related to the arrangement of the cold welds in the interveins compartment is that the electrical conductors of the thermocouple extending between the hot weld and the cold welds are shorter compared to an arrangement of the cold welds in the blower compartment. These electrical conductors are made with different pairs of metals and / or alloys. On the other hand, the electrical wiring between the cold welds and the computer can be carried out by simple electrical conductors, for example copper conductors. Electrical wiring thus presents a reduced cost compared to a traditional solution.

According to a particular embodiment, the turbojet regulating system comprises a housing housed in the inter-vein compartment, the cold welds and the cold welding temperature sensor being housed in the housing. The housing is called a "cold junction housing".

Advantageously, the cold junction box is insulated. Indeed, the inter-vein compartment is subject to strong thermal heterogeneities, both spatial and temporal. These heterogeneities are due to the radiation from the hot surfaces of the turbojet engine and to the fact that the inter-vein compartment is ventilated by air taken from the external environment. The cold junction box then provides thermal protection to the cold welds and to the cold weld temperature sensor and makes it possible to limit the potential temperature differences between the cold welds, as well as between each cold weld and the weld temperature sensor. cold.

The turbojet regulating system can comprise several thermocouples, each thermocouple comprising a hot weld and two cold welds. The cold welds are then preferably positioned in the same cold weld housing. The same cold junction temperature sensor can be used as the temperature sensor for all thermocouples.

The cold junction and the cold junction temperature sensor can be positioned in the vicinity of a fluid distribution pipe, said pipe being housed at least partially in the inter-vein compartment. The cold solders and the cold weld temperature sensor can in particular be positioned in the vicinity of a pipe for cooling a turbine, such a pipe being generally devoid of any means making it possible to detect the presence of a leak. When the fluid circulating in the pipeline has a sufficient temperature difference with the internal temperature of the inter-vein compartment, a fluid leak causes an increase in temperature and this increase can be associated with the presence of a leak. The temperature anomaly detection system then forms a fluid leak detection system.

The cold solders and the cold weld temperature sensor can also be positioned in the vicinity of heat-sensitive equipment, for example a structural element of aluminum or composite material, or an electronic component. The processing unit of the temperature anomaly detection system can be arranged to determine a temperature anomaly as a function of the temperature measured by the cold junction temperature sensor and of a maximum temperature supported by the sensitive equipment. heat, for example the maximum operating temperature of the electronic component.

The turbojet engine includes, for example, a service passage arm and an electric harness. The service passage arm mechanically connects the inter-vein compartment to the blower compartment by crossing the secondary vein. The electrical harness includes a set of electrical conductors electrically connecting the cold welds to the computer and connecting the cold weld temperature sensor to the computer and the processing unit. Each of the electrical conductors of the electrical harness can be made of copper.

Several detection logics can be implemented to determine a temperature anomaly in the inter-vein compartment. According to a first embodiment, the processing unit is arranged to determine a temperature anomaly in the inter-vein compartment by comparison of the temperature measured by the cold junction temperature sensor with a predetermined threshold. Such a threshold can be determined as a function of the maximum temperature expected in the vicinity of the cold junction temperature sensor and / or of the maximum temperature supported by a heat-sensitive element installed nearby, independently of the external parameters and of the operating point. of the turbojet engine. The threshold is for example fixed at 50 ° C or at 100 ° C. This embodiment is simple to implement and makes it possible to effectively protect the heat-sensitive elements installed near the temperature sensor.

According to a second embodiment, the processing unit is arranged to determine a temperature anomaly in the interveins compartment by comparison of the temperature measured by the cold junction temperature sensor with a threshold determined as a function of external parameters of the turbojet engine. In particular, the threshold can be determined as a function of an air temperature at the inlet of the turbojet engine, also called temperature T12. This embodiment overcomes in part the conditions under which the aircraft equipped with the turbojet operates. The risk of false detection of an abnormal temperature rise may be limited in a very hot outdoor environment, as well as the risk of missing the detection of an abnormal temperature rise in a very cold outdoor environment.

According to a third embodiment, the processing unit is arranged to determine a temperature anomaly in the interveins compartment by comparison of the temperature measured by the cold junction temperature sensor with a threshold determined by means of a thermal model and operating parameters of the turbojet engine. The operating parameters of the turbojet engine may in particular include a temperature of the exhaust gases (EGT) of the turbojet engine, an air temperature at the inlet of the turbojet engine (T12) or a speed of rotation of a turbine of the turbojet engine, for example a high pressure turbine or low pressure turbine.

In each of the embodiments, a temperature anomaly can be declared when the temperature measured by the cold junction temperature sensor is higher than the threshold considered. The invention also relates to an aircraft comprising a turbojet as described above.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood with the aid of the description which follows, given solely by way of nonlimiting example and made with reference to the appended drawings in which: - Figure 1 schematically shows a turbojet engine for aircraft of a known type; - Figure 2 schematically shows a conventional installation of a regulation system of a turbojet; - Figure 3 shows, compared to Figure 2, an installation of a regulation system of a turbojet engine according to the invention.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 1 schematically represents a turbofan engine with double flow and with a double body for an aircraft of a known type. The turbojet engine 10 comprises a nacelle 11 of generally cylindrical shape and in which are housed a fan wheel 12 and a turbojet engine core 13. The nacelle 11 comprises a fan compartment 111 delimited internally by a fan casing 1111 and externally by a casing nacelle 1112. The heart 13 comprises an inter-vein compartment 132 and, from upstream to downstream, a low pressure compressor 133, a high pressure compressor 134, a combustion chamber 135, a high pressure turbine 136 and a low pressure turbine 137. The compressors 133, 134 and the turbines 136, 137 are mounted in rotation about an axis X. The blower 12 is mounted upstream of the core 13 and is intended to suck a flow of air at the inlet of the turbojet engine 10. This flow air is divided into a primary flow flowing in a primary flow flow channel, hereinafter referred to as "primary stream 14", and a secondary flow flowing in a dry flow channel wave, hereinafter referred to as "secondary vein 15". The primary vein 14 is formed within the heart 13 and is delimited internally by different surfaces of the rotating elements of the heart 13 and externally by an internal casing 1321 of the inter-vein compartment 132. The secondary vein 15 is delimited internally by an external casing 1322 of the inter-vein compartment 132 and externally by the fan casing 1111. The turbojet engine 10 also comprises an arm 16 for the passage of easements extending radially between the inter-vein compartment 132 and the blower compartment 111. The arm 16 is arranged to allow passage of electrical cables and fluid lines. It can also participate in the mechanical behavior of the turbojet engine.

Throughout the description, the axial direction X is the direction along a longitudinal axis of the turbojet engine, the vertical direction Z is the direction orthogonal to the axial direction X and oriented vertically when the turbojet engine equips an aircraft parked on the ground, and the transverse direction Y is orthogonal to the axial X and vertical Z directions. Furthermore, the radial direction designates any direction along an axis perpendicular to the longitudinal axis of the turbojet engine. The upstream and downstream directions are defined by reference to the general flow of gases in the turbojet engine.

The turbojet engine 10 is further equipped with a regulation system 20, which comprises a computer 21 also called an engine computer, produced for example by a digital electronic control system with full authority of the engine, commonly called "FADEC" for "Full- Authority Digital Engine Control ”. This system 20 notably comprises a set of sensors connected to the computer 21. The computer 21 is typically housed in the fan compartment 111 and the sensors can be positioned at different points of the turbojet engine 10, in particular at different points of the primary stream 14 and of the secondary vein 15. In particular, the regulation system 20 may include an ejection gas temperature sensor 22, also called an EGT sensor according to the English name "Exhaust Gas Temperature", intended to measure the temperature of the gases d ejection into the primary stream 14 downstream of the low pressure turbine 137. This sensor 22 is typically a thermocouple, because of the wide range of temperatures to which it is subjected.

FIG. 2 schematically represents a conventional installation of a system 20 for regulating the turbojet engine. As indicated above, the system 20 notably comprises a computer 21 housed in the fan compartment 111 and a thermocouple 22, the sensitive part of which is positioned in the primary stream 14. The thermocouple 22 comprises a first electrical conductor 221 and a second electrical conductor 222 electrically connected to each other at a first end to form the sensitive part of the thermocouple. This electrical connection is called "hot weld 223". Different pairs of specific materials can be used to form the electrical conductors 221, 222. It is, for example, a pair comprising a first electrical conductor made of a nickel and chromium alloy (especially marketed under the brand name "Chromel" ) and a second electrical conductor made of nickel, aluminum and silicon alloy (in particular sold under the brand name "Alumel"). The thermocouple is then of type K. The electrical conductors 221, 222 each extend to a connection point formed in the fan compartment 111, in the immediate vicinity of the computer 21. These connection points are called “cold welds 224 , 225 ". Each cold junction 224, 225 electrically connects a second end of an electrical conductor 221, 222 to an electrical conductor 226, 227. In some cases, the electrical conductors 221, 222 are directly connected to terminals of the computer 21. In any condition As a result, each electrical conductor 221, 222 extends inside at least part of the inter-vein compartment 132, over the entire length of an arm 16 for passage of easements, and over at least part of the blower compartment 111. The electrical conductors 226, 227 are made of the same material, for example copper. They connect to the computer 21 so as to allow the measurement of a voltage between the two cold welds 224, 225. The computer 21 also receives a measurement of the temperature of the cold welds 224, 225 by means of a sensor temperature, called "cold junction temperature sensor 23". The cold junction temperature sensor 23 and the two cold welds 224, 225 are placed in a housing 210 of the computer 21. When reading FIG. 2, it appears that the electrical conductors 221, 222 have a substantial length between the weld hot 223 positioned in the primary stream 14 and cold welds 224, 225 positioned in the blower compartment 111. These electrical conductors being formed in specific materials can present a significant cost. In addition, their integration into an electrical harness can be tricky. Application FR 3 027 106 A1 describes a probe for measuring the temperature of the gases leaving a helicopter gas turbine, in which the cold welds and the cold weld temperature sensor are housed in an insulated housing, positioned relatively close to hot welding. This housing has a connector for electrically connecting the cold welds to a remote processing unit via conventional cables. The invention proposes to use this principle of cold weld offset. In addition, it proposes to use the measurement of the temperature of the cold welds to detect a temperature anomaly in the environment of these cold welds.

FIG. 3 schematically represents an installation of a system for regulating a turbojet engine according to the invention. The system 30 for regulating the turbojet engine differs from the system 20 in FIG. 2 in that the cold welds 224, 225 and the cold weld temperature sensor 23 are offset from the computer 21. These elements are housed in a housing, called "Cold junction box 31" positioned in the inter-vein compartment 132. In particular, this box 31 can be positioned close to heat-sensitive equipment, for example an electronic component, or close to a fluid for which leak monitoring is desired. The housing 31 is preferably insulated. The risks of temperature difference between the cold welds 224, 225 are then minimized. Each electrical conductor 221, 222 of the thermocouple 22 extends between the hot junction 223 positioned in the primary stream 14 and a cold junction 224, 225 housed in the inter-vein compartment 132, more particularly in the cold junction box 31. The electrical conductors 221, 222 are also formed by a pair of specific materials. A first electrical conductor 32 connects the cold junction 224 to the computer 21 and a second electrical conductor 33 connects the cold junction 225 to the computer 21. The electrical conductors 32, 33 do not need to be made of a particular material. They are for example made of copper. The cold junction temperature sensor 23 is also connected to the computer 21 by an electrical conductor 34. According to the technology of the temperature sensor, several electrical conductors can be used. They are for example made of copper. In the embodiment of Figure 3, the electrical connection between the computer 21 and the cold junction box 31 is made by means of electrical connectors. The computer 21 includes an electrical connector 211 and the cold junction box 31 includes an electrical connector 311. The various electrical conductors 32, 33, 34 connecting the cold junction box 31 to the computer 21 are grouped together in the form of an electrical harness. They end at one end with an electrical connector 35 capable of coupling to the electrical connector 211 of the computer 21 and at the other end with an electrical connector 36 capable of coupling with the electrical connector 311 of the cold junction box 31. Insofar as the electrical conductors 32, 33 can be made of a conventional material, for example copper, the creation of a harness with the electrical conductor 34 and possibly other electrical conductors is facilitated.

Analogously to the embodiment of FIG. 2, the cold junction temperature sensor 23 makes it possible to determine a temperature of the cold welds 224, 225. This measurement is fed back to the computer 21, or engine computer, which is arranged for determine, from this temperature and the voltage between the cold welds 224, 225, the absolute temperature at the hot weld 223. The computer 21 is further arranged to determine an abnormal temperature in the inter-vein compartment 132. To this end, it compares the temperature supplied by the cold junction temperature sensor to a threshold and generates a temperature anomaly indicator according to the result of the comparison. The engine computer 21 then also forms a processing unit for detecting a temperature anomaly. More generally, the system 30 for regulating the turbojet engine also forms a system for detecting a temperature anomaly.

Several logics for detecting a temperature anomaly in the inter-vein compartment are possible. According to a first embodiment, the computer 21 is arranged to compare the temperature within the cold junction box 31 with a predetermined threshold. This threshold can be determined as a function of the maximum temperature expected in the vicinity of the cold junction temperature sensor 23 and / or of the maximum temperature supported by a heat-sensitive element installed nearby. The threshold is for example fixed at 50 ° C or at 100 ° C.

According to a second embodiment, the computer 21 is arranged to compare the temperature within the cold junction box 31 to a parametric threshold, determined as a function of external parameters of the turbojet engine. The parametric threshold is for example determined as a function of an outside air temperature or as a function of an air temperature at the inlet of the turbojet engine (temperature T12). In particular, the parametric threshold can be fixed as being equal to the sum of the outside temperature observed and a predetermined deviation.

According to a third embodiment, the computer 21 is arranged to compare the temperature within the cold junction box 31 to a variable threshold, determined by means of a thermal model and operating parameters of the turbojet engine. By thermal model is meant a mathematical model making it possible to determine a value for the variable threshold as a function of at least one operating parameter of the turbojet engine. The operating parameters of the turbojet engine which can be taken into account by the thermal model are the temperature of the exhaust gases (EGT) of the turbojet engine, the temperature of the air entering the turbojet engine (T12), the rotation speed of the high pressure turbine of the turbojet engine and the speed of rotation of the low pressure turbine of the turbojet engine.

In the embodiment of FIG. 3, it has been considered that the processing of the temperature in order to determine a temperature anomaly in the inter-vein compartment was carried out by the computer 21 of the system 30 for regulating the turbojet engine, it that is to say the engine ECU. However, this processing could be carried out by a processing unit separate from the computer 21. This processing unit can be dedicated to the detection of a temperature anomaly. The processing unit can also be integrated into an aircraft condition monitoring system, called “Aircraft Condition Monitoring System” (ACMS).

Claims (10)

1. Double-flow turbojet engine comprising a primary vein (14), a secondary vein (16), an inter-vein compartment (132) separating the primary vein from the secondary vein and a blower compartment (111) delimiting the secondary vein externally , the turbojet engine (10) further comprising a system (30) for regulating the turbojet engine and a system for detecting a temperature anomaly in the inter-vein compartment (132), the regulating system comprising a thermocouple (22), a cold junction temperature sensor (23) and a computer (21), the thermocouple comprising a hot junction (223) positioned in the primary vein and two cold junction positioned in the inter-vein compartment, the cold junction temperature sensor (23) being positioned in the inter-vein compartment (132) in the vicinity of the cold welds (224, 225), the computer (21) being positioned in the blower compartment (111) and é so arranged to determine a temperature in the primary vein (14) as a function of a voltage between the two cold seals and a temperature measured by the cold junction temperature sensor, the temperature anomaly detection system comprising a processing unit (21) arranged to receive the temperature measured by the cold junction temperature sensor (23) and determine a temperature anomaly in the inter-vein compartment as a function of said measured temperature. 2. The turbojet engine as claimed in claim 1, in which the system (30) for regulating the turbojet engine comprises a housing (31) housed in the interveins compartment (132), the cold welds (224, 225) and the cold weld temperature sensor. (23) being housed in the housing (31). 3. The turbojet engine as claimed in claim 2, in which the system (30) for regulating the turbojet engine comprises several thermocouples, each thermocouple comprising a hot weld and two cold welds, the cold welds of each thermocouple being positioned in the housing (31). 4. Turbojet engine according to one of the preceding claims, in which the cold welds (224, 225) and the cold weld temperature sensor (23) are positioned in the vicinity of a fluid distribution pipe, said pipe being housed at least partly in the inter-vein compartment (132). 5. A turbojet engine according to one of the preceding claims, in which the cold solders (224, 225) and the cold weld temperature sensor (23) are positioned in the vicinity of an electronic component. 6. Turbojet engine according to one of the preceding claims, further comprising an arm (16) for passage of easements and an electrical harness, the easement passage arm mechanically connecting the inter-vein compartment (132) to the blower compartment (111). by crossing the secondary stream (15) and the electrical harness comprising a set of electrical conductors (32, 33, 34) electrically connecting the cold solders (224, 225) to the computer (21) and connecting the cold weld temperature sensor ( 23) to the computer (21) and to the processing unit (21). 7. The turbojet engine as claimed in one of the preceding claims, in which the processing unit (21) is arranged to determine a temperature anomaly in the inter-vein compartment (132) by comparison of the temperature measured by the temperature sensor of cold junction (23) with a predetermined threshold. 8. The turbojet engine as claimed in one of claims 1 to 6, in which the processing unit (21) is arranged to determine a temperature anomaly in the inter-vein compartment (132) by comparison of the temperature measured by the temperature sensor. cold junction temperature (23) with a threshold determined as a function of an air temperature at the inlet of the turbojet engine. 9. Turbojet engine according to one of claims 1 to 6, in which the processing unit (21) is arranged to determine a temperature anomaly in the inter-vein compartment (132) by comparison of the temperature measured by the temperature sensor. cold junction temperature (23) with a threshold determined by means of a thermal model and operating parameters of the turbojet engine. 10. Aircraft comprising a turbojet engine (10) according to one of the preceding claims.