FR3057301A1 - METHOD FOR HEATING AND DRYING AN AIR INTAKE OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

The main object of the invention is a method of heating and drying an air inlet (24) of an internal combustion engine (10), in particular a gas turbine fitted to a helicopter turbine engine, characterized in that, to limit the retention of liquid in the air inlet (24) and thereby limit corrosion of the air inlet (24), it comprises a step of, through a system for heating and drying (50) internal to the engine (10), heating and drying the air inlet (24) of the engine (10).

Description

(57) The main object of the invention is a method of heating and drying an air inlet (24) of an internal combustion engine (10), in particular a gas turbine fitted to a turboshaft engine. helicopter, characterized in that, in order to limit the retention of liquid in the air inlet (24) and thus limit the corrosion of the air inlet (24), it comprises a step consisting in, by means of 'a heating and drying system (50) internal to the motor (10), heating and drying the air intake (24) of the motor (10).

METHOD FOR HEATING AND DRYING AN AIR INTAKE OF AN INTERNAL COMBUSTION ENGINE

DESCRIPTION

TECHNICAL AREA

The present invention relates to the field of turbomachinery, in particular to the field of aeronautical and industrial internal combustion engines and more specifically, but not exclusively, to that of aircraft gas turbines such as the turboshaft engines which equip helicopters.

The invention relates more precisely to a method of heating and drying an air inlet of an internal combustion engine, in particular a gas turbine fitted to a helicopter turbine engine.

PRIOR STATE OF THE ART

When using a gas turbine helicopter turbine engine under special conditions, for example in a salty environment, accelerated aging of certain parts of the engine air intake may occur due to corrosion of the metal occurring prematurely. This corrosion comes mainly from the presence of water retention, or of liquid containing water, for example a compressor washing product used at the end of the mission to keep the interior of the engine clean and thus its performance, during periods can be quite long. In addition, the degradations developing rapidly on this air intake seem to be more linked to the time spent in the event of a stopped engine than in the case of an engine running.

More specifically, this retention of water or liquid causes a deterioration of the corrosion protection system and an increase in the aggressiveness of the external environment in the air inlet, thereby causing premature corrosion.

Then, the presence of corrosion developing rapidly in the air intake of the engine can cause movement blockages of certain parts in the air intake, such as blades, by amalgams of material or even generate objects. foreigners (or FOD for "Foreign Object Damage" in English) which can then be ingested by the compressor.

There is therefore a need to implement a solution making it possible to slow down, or even stop, such corrosion.

Among the solutions known for combating the rapid development of corrosion, it is possible to use detergents containing corrosion inhibitors. However, such inhibitors are not strong enough to slow the onset of corrosion sufficiently.

It is also possible to modify the air inlet protection system by means of more efficient coatings with respect to corrosion protection. However, the installation of such coatings is delicate, both in time and in costs but also from a point of view of the manufacturability of the parts.

It can also be envisaged to change the geometry of the air intake of the engine. However, such a change is cumbersome in design and can only incorporate minor changes on pain of significantly impacting engine performance and weight.

Finally, a change in the materials of the air intake can be expected. However, the change of materials to materials with higher corrosion resistance or other types of properties can have serious consequences and may not satisfy the overall weight of the engine, the conditions of use of the control systems or the manufacturability of the parts initially produced.

Consequently, the possibilities of solutions envisaged above appear to be either ineffective, or time-consuming to set up, or too heavy or too dangerous for implementation on the engine without high risks of modification of the performance or reliability of the engine. .

STATEMENT OF THE INVENTION

The invention therefore aims to at least partially remedy the needs mentioned above and the drawbacks relating to the embodiments of the prior art.

The subject of the invention is therefore, according to one of its aspects, a method of heating and drying an air inlet of an internal combustion engine, in particular a gas turbine fitted to a helicopter turbine engine, characterized in that, in order to limit, in particular to avoid, the retention of liquid, in particular water, in the air inlet and thus to limit, in particular to avoid, corrosion of the air inlet, it comprises a step consisting of, by means of a heating and drying system internal to the engine, heating and drying the air intake of the engine.

Thanks to the invention, it may be possible to carry out heating and drying on the air intake of the engine by a simple action, making it possible to limit the effects of water or liquid retention in the engine. This solution does not require a major change for the engine, and turns out to be very quick and simple to deploy.

The method according to the invention may also include one or more of the following characteristics taken in isolation or according to any possible technical combination.

The heating and drying system can for example be an electric heating system internal to the engine.

The engine internal heating and drying system may preferably be an engine anti-icing system.

Said step of heating and drying the air inlet can preferably be carried out in the parking phase before stopping the engine.

In addition, said step of heating and drying the air inlet can be carried out after a washing phase of the engine compressor.

In addition, said step of heating and drying the air inlet can preferably be carried out for at least 2 minutes, in particular between 5 to 10 minutes.

Furthermore, said step of heating and drying the air inlet can very particularly be applied to a gas turbine fitted to a helicopter turbine engine.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be better understood on reading the detailed description which follows, of an example of non-limiting implementation thereof, as well as on examining the single, schematic and partial figure, of the attached drawing, showing in section an example of an anti-icing system for a helicopter turbine engine.

DETAILED PRESENTATION OF A PARTICULAR EMBODIMENT

The principle of the invention can advantageously be implemented for a gas turbine fitted to a helicopter turbine engine. As mentioned above, it aims to limit, or even avoid, the retention of liquid, in particular water, in the air intake of the engine so as to limit the effects of corrosion at the intake of air due to this presence of liquid.

Advantageously, the invention uses in this particular example of implementation the engine anti-icing system to produce heating, by introducing hot air into the air stream at more than 50 ° C., and a drying of the air intake, in other words a system internal to the engine which was not initially planned for this operation on the engine. Examples of anti-icing or de-icing systems are for example described in the French patent applications of the Applicant FR 2 914 016 Al and FR 2 993 862 Al.

Thus, by way of example in connection with French patent application FR 2 914 016 A1, there is shown in FIG. 1, partially in section, an internal combustion engine constituted by a helicopter turbine engine 10 comprising a generator. gas 12 and a free turbine 14. The gas generator 12 comprises a shaft 16 on which is mounted a centrifugal compressor wheel 18 disposed in a compression stage 20, which shaft 16 also carries a turbine wheel 22.

In known manner, moreover, the turbine engine has an air inlet 24 by which a stream of incoming fresh air is guided towards the compression stage 20. The compressed air is then sent to a combustion chamber 26. The air inlet 24 of the turbine engine comprises a plurality of veins 28 in each of which the incoming fresh air flow penetrates radially or axially before being guided to enter axially into the compression stage.

The turbine engine 10 shown in this figure is provided with a deicing device 50 which allows the air inlet 24 of the turbine engine to be defrosted. In this example, the deicing device 50 comprises an essentially metallic enclosure 52 for the entry of air into the inlet veins 28 of the turbine engine 10, fixed to a casing 30 of the helicopter.

The enclosure here forms a plenum 52 whose axis coincides substantially with that of the shaft 16 of the gas generator 12 and whose height is at least equal to the axial length of the veins 28.  The plenum 52 comprises a portion extending radially and the end of which forms a first radial opening 54 opening towards the outside of the turbine engine 10 and through which the fresh air enters the deicing device 50.  As can be seen in the figure, the first opening 54 is provided with a first essentially metallic grid 56 making it possible in particular to filter the air entering the enclosure 52.  The enclosure 52 further comprises a second opening 58 intended to direct the fresh air towards the compression stage 20 via the veins 28, this second opening 58 extending in this case annularly around the axis of the shaft 16 of the gas generator 12.  The second opening 58 is further provided with a second essentially metallic grid 60 which is also annular.

The defrosting device 50 further comprises means 62 for generating microwaves in the essentially metallic enclosure 52 and more particularly in the space A delimited by the first and second essentially metallic grids. Said means comprise a magnetron 62 provided with a waveguide 64. According to the invention, the frequency of the microwaves generated is substantially equal to the resonance frequency of a water molecule, that is to say say about 2.45 Ghz. Thus, this space A constitutes a confinement zone for the microwaves, that is to say that they can rebound on the edges of the space A.

The operation of heating and drying the air intake via the anti-icing system can be carried out after a possible washing phase of the compressor, and in particular after the helicopter mission, in particular during the parking phase of the helicopter just before stopping the engine so that a dry engine can be kept when the helicopter is not in use. In certain engine configurations, the anti-icing system can use hollow blades or internal channels in the walls of the casings to route air into the air intake and thus introduce into the vein, hot air necessary when the engine is defrosted.

The anti-icing system is advantageously switched on for at least 2 minutes, and in particular for 5 to 10 minutes. It will then cause the temperature of the pre-rotation blades at the air inlet to increase (of the IGV type for “Inlet Guide Va née” in English), which are hollow blades into which air is brought. hot air taken downstream in the stream at the compressors. This allows to orient the air flow to improve engine performance, to warm the surface of the pre-rotation blades and to introduce hot air into the air stream to a temperature above 50 ° C, for example greater than 100 ° C, preferably greater than 120 ° C, and increase the temperature of the air stream, which can be more than 80 ° C at the surface of the materials.

This increase in air temperature in the vein, as well as the passage of air, will make it possible to evaporate the liquid which can be retained in the vein and thus considerably slow down the corrosion rate of the air inlet. of the motor.

While the anti-icing system is conventionally used only for specific icing conditions, and at no other time, taking into account the fact that the introduction of hot air into the air intake and its removal at level of the compressor causes a loss of engine performance, by the introduction of hot air upstream of the compressor, the invention proposes to put this anti-icing system into service for other conditions, namely for the evaporation of liquid retained in the air intake which can lead to corrosion, in particular when the helicopter is parked before it comes to a complete stop signifying the end of service.

Of course, the invention is not limited to the embodiment which has just been described. Various modifications can be made by those skilled in the art.

Claims (6)

1. A method of heating and drying an air inlet (24) of an internal combustion engine (10), characterized in that, to limit the retention of liquid in the air inlet (24) and thus limit corrosion of the air inlet (24), it comprises a step consisting in, by means of a heating and drying system (50) internal to the engine, heating and drying the inlet air (24) from the engine (10). 2. Method according to claim 1, characterized in that the heating and drying system (50) internal to the engine is an engine anti-icing system. 3. Method according to claim 1 or 2, characterized in that said step of heating and drying the air inlet (24) is carried out in the parking phase before stopping the engine (10). 4. Method according to one of the preceding claims, characterized in that said step of heating and drying the air inlet (24) is carried out after a washing phase of the engine compressor (10). 5. Method according to any one of the preceding claims, characterized in that said step of heating and drying the air inlet (24) is carried out for at least 2 minutes, in particular between 5 to 10 minutes. 6. Method according to any one of the preceding claims, characterized in that said step of heating and drying the air inlet (24) is applied to a gas turbine fitted to a helicopter turbine engine (10). S.61977