Turbine for an aircraft turbojet engine

Abstract

Turbine (27) for an aircraft turbofan engine (21), the turbine (27) having a main axis (X) and comprising a primary runner (35), at least one row of fixed blades (29) arranged in the primary runner (35) and distributed circumferentially around the axis (X), and at least one row of rotating blades (31) mounted on a disk (33) that rotates about the axis (X) and is axially offset from the at least one row of fixed blades (29). The turbine (27) further comprises at least one pollutant sensor (43) positioned in the primary runner (35), configured to measure at least one representative value of a quantity of solid particles in an airflow (F) flowing through the turbine (27). Figure to be published with the abbreviation: 2

Description

Title of the invention: Turbine for an aircraft turbojet engine Technical field of the invention

[0001] The invention relates to the field of safety and durability of propulsion turbomachines for aircraft. More specifically, the invention relates to a turbine for an aircraft turbojet, provided with at least one pollutant sensor. State of the prior art

[0002] [Fig.l] illustrates a prior art dual-flow turbojet engine 1, intended to equip an aircraft, in particular an airplane. The turbojet engine 1 extends along a main axis X and comprises, from upstream to downstream in the direction of gas circulation, a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6 and a low-pressure turbine 7. The low- and high-pressure compressors 3, 4, the combustion chamber 5 and the high- and low-pressure turbines 6, 7 form a so-called primary flow path 8. A so-called secondary flow path 9 extends around the primary flow path 8, downstream of the fan 2.

[0003] The terms axial, radial and circumferential are defined relative to a main axis X of the turbojet engine 1. The terms upstream and downstream are defined relative to the direction of circulation of the gases within the turbojet engine 1.

[0004] The low pressure compressor 3 and the low pressure turbine 7 together form a low pressure body, and are connected to each other by a low pressure shaft 11 centered on the main axis X. Similarly, the high pressure compressor 4 and the high pressure turbine 6 form a high pressure body, and are connected to each other by a high pressure shaft 13 centered on the axis X, coaxial with and arranged around the low pressure shaft 11.

[0005] On such a turbojet, the low and high pressure turbines 6, 7 recover part of the energy from the combustion of the gases for the operation of the fan 2, the compressors 3, 4 and the accessories powered by taking energy directly from the shafts.

[0006] In a known manner, the low-pressure turbine 7 comprises at least one series of fixed blades, or distributors, regularly arranged circumferentially and extending radially around the main axis X, forming a stator, and at least one series of radial rotary blades, mounted on at least one disc centered on the axis and mobile in rotation around the main axis X, forming a rotor. The low-pressure turbine 7 typically comprises several such series of fixed blades and axially alternating mobile blades.

[0007] During operation of the turbojet, the fixed and moving blades can be deteriorated and present deposits or incrustations linked to the presence of pollutant particles in the air flow and / or to oxidation or corrosion.

[0008] These events can significantly reduce the life of the turbine blades and may require early disassembly of the engine for maintenance and possibly replacement of parts in the event of non-compliance.

[0009] It is known that corrosion attacks are due to the presence of particles in the turbine, in particular those containing sulfur and sulfates, as well as to the pressure and temperature of the air flow flowing through the turbine. Corrosion attacks are thus very variable phenomena, and their frequency and severity can increase significantly over specific ranges of temperature, pressure and pollutant concentration.

[0010] It is common to install temperature and pressure probes in a turbojet engine, intended to monitor the correct operation of the machine, and the data from which are collected during the flight.

[0011] The presence of pollutants is estimated on a large scale based on knowledge of the aircraft trajectory and a map of pollutant concentrations in different regions crossed, taken for example from meteorological databases. However, this method remains very imprecise, which makes it difficult to have reliable forecasts on the degradation of the blades. In addition, the portion of polluting particles resulting from the operation of the combustion chamber, which releases sulfates in the form of sulfur dioxide and trioxide, is not taken into account by these models.

[0012] It is therefore necessary, in order to improve the reliability and increase the operating time of a turbojet, to better anticipate and predict such attacks on the blades in order to implement maintenance operations when necessary. Presentation of the invention

[0013] The invention aims to overcome these drawbacks. To this end, the subject of the invention is a turbine for an aircraft turbojet, the turbine having a main axis and comprising a primary vein, at least one row of fixed blades arranged in the primary vein and distributed circumferentially around the axis and at least one row of rotary blades, mounted on a disk mobile in rotation around the axis, axially offset relative to the at least one row of fixed blades,

[0014] characterized in that the turbine further comprises at least one pollutant sensor, positioned at least partly in the primary stream and configured to measure at least one item of information representative of a quantity of solid particles in an air flow flowing in the turbine.

[0015] Such a turbine makes it possible to continuously or periodically measure an ex- position of the turbine blades to pollutant particles, during the operation of the turbojet, and thus to predict more precisely the possibility of corrosion and / or oxidation attacks on the blades and required maintenance procedures.

[0016] The turbine is for example a low pressure turbine.

[0017] The at least one pollutant sensor can be positioned at an upstream inlet of the turbine and be capable of measuring information representative of the quantity of solid particles at said upstream inlet.

[0018] Such a characteristic makes it possible to measure the entire flow entering the low pressure turbine and to take into account the pollutants coming from the combustion chamber and those naturally present in the ambient air.

[0019] Each pollutant sensor may comprise a tube for sampling a portion of the air flow flowing in the primary stream and a remote analyzer, arranged away from the primary stream.

[0020] The analyzer can for example be positioned in a part of the turbojet engine less exposed to high temperatures and high pressures, such as in the vicinity of the FADEC, on the fan casing.

[0021] Such a characteristic makes it possible to use a remote analyzer and therefore less exposed to the severe temperature and pressure conditions which prevail in the most exposed parts of the turbojet.

[0022] Each sampling tube may be coaxial with an air flow temperature measuring probe arranged in the primary vein.

[0023] Such a feature makes it possible to precisely correlate particle quantity measurements with temperature measurements, these parameters having inseparable roles in corrosion attacks on the blades. This also allows an advantageous gain in terms of integration in the turbomachine, the addition of pollutant sensors then resulting in additional bulk and low airflow disturbance, by using the same locations as temperature probes already present in the turbine.

[0024] Each pollutant sensor may comprise a probe for detecting particles in the air flow, arranged in the primary vein.

[0025] Such a feature makes it possible to reduce the bulk and load generated by the sampling tubes by placing the probe directly in the air flow to be analyzed.

[0026] Each particle detection probe may extend in the vicinity of an air flow temperature measurement probe disposed in the primary vein.

[0027] Such a characteristic makes it possible to precisely correlate particle quantity measurements with temperature measurements, these parameters having inseparable roles in corrosion attacks on blades.

[0028] The turbojet engine may comprise a plurality of pollutant sensors distributed circumferentially around an upstream inlet of the turbine.

[0029] Such a characteristic makes it possible to measure the presence of pollutants in the air flow over the entire circumference of the turbine, to take into account possible heterogeneities in the flow.

[0030] Each pollutant sensor may be configured to discriminate detected particles among a plurality of categories based on a diameter of each detected particle.

[0031] Such a characteristic makes it possible to separate the particles according to their size and to obtain more specific information on particles comprising sulfur or sulfites, which are more likely to cause corrosion problems.

[0032] The at least one pollutant sensor may comprise at least one laser nephelometry sensor.

[0033] Such a characteristic makes it possible to obtain real-time information on the particle concentration in the air flow, and if necessary to discriminate by particle size.

[0034] The invention also relates to a turbojet comprising a turbine as above. Brief description of the figures

[0035] [Fig-1] is a sectional view of a prior art turbojet engine,

[0036] [Fig.2] is a sectional view of a low pressure turbine of a turbojet according to the invention,

[0037] [Fig.3] is a schematic view of a pollutant sensor of the turbojet engine of the [Fig.2], and

[0038] [Fig.4] is a schematic view of a pollutant sensor according to another embodiment of the invention. Detailed description of the invention

[0039] [Fig. 2] is a detailed view of a turbojet engine 21 according to the invention, similar to the turbojet engine 1 described above except for the following.

[0040] The turbojet 21 comprises a low pressure turbine 27 visible in [Fig.2], located downstream of the combustion chamber and the high pressure turbine.

[0041] An air flow F, called the primary airflow, flows from the combustion chamber through the high-pressure turbine and the low-pressure turbine 27. Said air flow F comprises pollutant particles resulting from the combustion of the fuel in the combustion chamber, as well as pollutant particles present in the air entering the turbojet 21 and flowing in the primary and secondary airflows.

[0042] The low pressure turbine 27 comprises a plurality of series of fixed blades 29, or distributors, distributed circumferentially around the main axis X and axially offset from each other, forming a stator of the low pressure turbine 27.

[0043] The low pressure turbine 27 also comprises a plurality of series of moving blades 31, mounted on respective discs 33 centered on the main axis X, the moving blades 31 and the discs 33 forming a rotor of the low pressure turbine 27 mounted on the low pressure shaft.

[0044] The low-pressure turbine 27 comprises a primary vein 35, which is a substantially annular duct for the flow of air F, across which the fixed blades 29 and the moving blades 31 extend, which extends axially from an upstream inlet 37 of the low-pressure turbine 27 to a downstream outlet 39.

[0045] The low-pressure turbine 27 also comprises a plurality of temperature probes 41, capable of measuring a temperature of the air flow F flowing in the low-pressure turbine 27, and a plurality of pollutant sensors 43, capable of measuring at least one item of information representative of a quantity of solid particles in the air flow F flowing in the low-pressure turbine 27, through the primary vein 35.

[0046] The temperature probes 41 are for example arranged in the vicinity of the upstream inlet 37 of the low-pressure turbine 27, in the primary vein 35, and regularly distributed circumferentially on an external periphery 45 of the primary vein 35. For example, the temperature probes are located axially at the level of the first series of fixed blades 29, or else slightly upstream of this first series of fixed blades 29.

[0047] The low pressure turbine 27 comprises, for example, up to eight temperature probes 41 and eight pollutant sensors 43 circumferentially distributed on the external periphery of the primary vein 35.

[0048] Such a temperature probe 41 and such a pollutant sensor 43 are shown schematically in [Fig.3], according to a first embodiment of the invention.

[0049] Each temperature probe 41 is formed of an elongated element extending radially in projection from the external periphery 45 of the primary vein 35.

[0050] The temperature probes are for example connected to a common control module (not shown) by at least one connection cable 47, the control module centralizing and recording the measured data for analysis. The control module is advantageously remote, that is to say positioned away from the primary vein 35.

[0051] The temperature probes 41 are for example of the type designated under the English name Exhaust Gas Temperature sensors, or EGTsensors.

[0052] The information measured by the pollutant sensors 43 is for example a volume concentration of solid particles in the air flow, in particular for a predetermined range of particle sizes. Said range of particle sizes extends, for example, between a minimum particle detection diameter and a maximum particle detection diameter.

[0053] In the embodiment shown in [Fig. 3], each pollutant sensor 43 comprises a sampling tube 49 extending radially from the outer periphery 45 in the direction of the main axis X, in the primary vein 35 of the low pressure turbine 27, across the air flow F.

[0054] Each pollutant sensor 43 also comprises a conduit 51 opening in the bottom of the sampling tube 49, and an analyzer 53 connected to the other end of the conduit 51 and configured to analyze the information relating to the quantity of particles.

[0055] The sampling tube 49 is capable of sampling a portion F' of the air flow F and redirecting it into the conduit 51, in which the portion F' flows to the analyzer 53 where it is analyzed to obtain at least one piece of information relating to the quantity of pollutants.

[0056] Such an arrangement makes it possible to arrange the analyzer 53 away from the primary flow path 35 of the low-pressure turbine 27 and thus to protect it from vibrations and high temperatures. The analyzer 53 is for example arranged in a cold zone of the turbojet engine 21, for example at the level of the fan casing, with the instruments and digital control modules (or FADEC) of the turbojet engine 21.

[0057] The analyzer 53 is for example connected to the same control module as the temperature probes 41 by a connection cable 55, the pollutant presence and temperature data being recorded in a correlated manner for a common analysis.

[0058] The sampling tube 49 is advantageously arranged in the vicinity of one of the temperature probes 41, in particular at the same level axially.

[0059] Advantageously, the sampling tube 49 is coaxial with the elongated element of the temperature probe 41, said elongated element extending into the sampling tube.

[0060] Such an arrangement makes it possible to have a good correlation between the measurements of temperature and the presence of pollutant particles, in order to better estimate the risks of corrosion.

[0061] Advantageously, the analyzer 53 is capable of discriminating the detected particles among a plurality of particle size categories. For example, the analyzer 53 may be adapted to classify the detected particles among the following categories: particles with a diameter greater than 1 micrometer, particles with a diameter greater than 2.5 micrometers, particles with a diameter greater than 5 micrometers, particles with a diameter greater than 10 micrometers.

[0062] This makes it possible to isolate the particles most likely to lead to corrosion attacks, such as particles containing sulfur or sulfates, from their characteristic size.

[0063] According to another embodiment, shown in [Fig.4], each pollutant sensor 43 comprises a particle detection probe 57 directly arranged in the primary vein 35 of the low pressure turbine 27, across the air flow F.

[0064] Thus, the measurements of the information relating to the quantity of particles are made in situ in the low pressure turbine 27, without requiring a remote arrangement.

[0065] Each particle detection probe 57 is connected to the control module by a respective cable 55.

[0066] The measurement of the information relating to the quantity of particles in the air flow is for example carried out using the laser nephelometry method, which makes it possible to measure a volume concentration of particles in the air flow and to discriminate the particles according to their size.

[0067] The combined measurement of the temperature of the air flow entering the low pressure turbine 27 and its concentration of pollutant particles makes it possible to accurately predict the occurrence of a risk of corrosion attack and to implement appropriate processes.

[0068] The invention described in the context of a low pressure turbine can be generalized to any type of turbojet turbine, and in particular to the case of a high pressure turbine.

Claims

Claims

1. Turbine (27) for a turbojet engine (21) for an aircraft, the turbine (27) having a main axis (X) and comprising a primary duct (35), at least one row of fixed blades (29) arranged in the primary duct (35) and distributed circumferentially around the axis (X) and at least one row of rotary blades (31), mounted on a disc (33) movable in rotation around the axis (X), axially offset relative to the at least one row of fixed blades (29), characterized in that the turbine (27) further comprises at least one pollutant sensor (43), positioned at least partly in the primary duct (35) and configured to measure at least one item of information representative of a quantity of solid particles in an air flow (F) flowing in the turbine (27).

2. Turbine (27) according to the preceding claim, in which at least one pollutant sensor (43) is positioned at an upstream inlet (37) of the turbine (27) and is capable of measuring information representative of the quantity of solid particles at said upstream inlet (37).

3. Turbine (27) according to one of the preceding claims, in which each pollutant sensor (43) comprises a sampling tube (49) of a portion (F') of the air flow (F) flowing in the primary vein (35) and a remote analyzer (53), arranged away from the primary vein (35).

4. Turbine (27) according to the preceding claim, in which each sampling tube (49) is coaxial with a temperature measuring probe (41) of the air flow (F) arranged in the primary vein (35).

5. Turbine (27) according to claim 1 or 2, in which each pollutant sensor (43) comprises a particle detection probe (57) in the air flow (F), arranged in the primary vein (35)).

6. Turbine according to the preceding claim, in which each particle detection probe (57) extends in the vicinity of a temperature measurement probe (41) of the air flow (F) arranged in the primary vein (35).

7. Turbine (27) according to one of the preceding claims, comprising a plurality of pollutant sensors (43) distributed circumferentially around an upstream inlet (37) of the turbine (27).

8. Turbine (27) according to one of the preceding claims, in which each pollutant sensor (43) is configured to discriminate the particles detected from a plurality of categories based on a diameter of each detected particle.

9. Turbine (27) according to one of the preceding claims, in which the at least one pollutant sensor (43) comprises at least one laser nephelometry sensor.

10. Turbojet (21) comprising a turbine (27) according to one of the preceding claims.