CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority from Italian patent application no. 102021000005525 filed on March 9, 2021, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD The present invention relates to an anti-icing device for intake opening of the engine nacelle for turbojet or turbofan engines.

BACKGROUND OF THE INVENTION

The accumulation of atmospheric ice adversely affects the aerodynamic characteristics of the aircraft, alters the flow rate and regularity of the flow in the air intake of the engines, can occlude the static and dynamic intakes of the altimeters and speed indicators, and, in case of detachment of ice fragments from the air intake and ingestion by the engine, can cause extensive damage to the compressor blades.

Aim of the present invention is to make an anti-icing device for intake opening of the engine nacelle for turbojet or turbofan engines that is electrically powered and with low consumptions. Prior art document US 8,181,900.

SUMMARY OF THE INVENTION

The preceding aim is achieved by the present invention in that it relates to an anti-icing device for intake opening of nacelle engine for turbojet or turbofan engines wherein the intake opening is delimited at the front by a front annular portion formed by a first outer annular wall facing the outside of the nacelle itself and by a second inner annular wall facing the intake opening of the nacelle itself and connected with the first portion through a curved profile, the second inner annular wall being connected by a rear side facing the engine with one peripheral side of a sound-absorbing tubular wall delimiting part of the suction line of the nacelle, characterised in that the anti-icing device comprises: - a first Joule effect heater device coupled to the first outer annular wall, powered by the electric energy present on the aircraft and configured, when powered, to heat the outer surface of the first outer wall causing the ice formed on the first wall to lose its adhesion which is then removed due to kinetic effect by the airflow outside of the nacelle engine or falls by gravity during the aircraft landing operations;- a second Joule effect heater device coupled to the second inner annular wall, powered by the electric energy present on the aircraft and configured, when powered, to heat the outer surface of the second inner wall so that any ice that has formed on the second inner annular wall is transformed into a film of water which flows along the second annular wall towards the sound-absorbing tubular wall; a discontinuity element is provided exclusively between the second inner annular wall and the peripheral side of the sound-absorbing tubular wall and is configured to perform the detachment of the liquid film (F) that flows on the inner annular wall due to the kinetic speed of the airflow sucked by the engine directing the nebulized air particles (G) towards the engine itself.

.BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, a preferred embodiment is described below, by way of non limiting example, with reference to the accompanying drawings wherein:

Figure 1 is a schematic representation of an engine nacelle having an anti-icing system according to the present invention; and

Figure 2 shows, in a cross-section and enlarged scale, the anti-icing system according to the present invention;

Figures 3 and 4 disclose a variant of the anti-icing system.

PREFERRED EMBODIMENT

In figure 1, 1 denotes, as a whole, an anti-icing device for intake opening 2 of the engine nacelle 3 for turbojet or turbofan engines (not shown) wherein the intake opening 2 is delimited at the front by a front annular portion 4 formed by a first outer annular wall 5 facing the outside of the nacelle 3 itself and by a second inner annular wall 6 facing the intake opening (and axis A) of the nacelle itself and connected with the first wall by means of a curved profile 7 having a substantially C-shaped section.

The second inner annular wall 6 is connected by a rear side facing the engine with a peripheral side 8-a of a sound- absorbing tubular wall 8 delimiting part of the suction line 9 of the nacelle 3. In the example the peripheral side 8-a is straight but its shape may be different.

According to the present invention (see figure 2) the anti-icing device 1 comprises a first Joule effect heater device 10 coupled to the first outer wall 5, powered by the electric energy present on the aircraft and configured, when powered, to heat the outer surface of the first outer wall 5 in a predetermined temperature range (e.g. between 7°C ÷ 21°C) causing the ice formed on the first wall 5 to lose adhesion, which is removed due to kinetic effect by the airflow outside of the engine nacelle or falls by gravity during the aircraft landing operations.

The first Joule effect heater device 10 is manufactured using known technologies (e.g. by film resistors) and comprises several heating sectors independent of one another installed angularly around the outer annular wall 5. Each heating sector is divided into several areas for delivering a different amount of thermal energy.

They are provided sensors (not shown) adapted to detect the temperature Te of the first outer wall 5.

The anti-icing device 1 comprises a second Joule effect heater device 11 (also of the known type) coupled to the second inner annular wall 6, powered by the electric energy present on the aircraft and configured, when powered, to heat the outer surface of the second inner wall 6 in a predetermined temperature range so that any ice formed on the second outer annular wall 6 is transformed into a film of water F which moves along the second inner annular wall 6 towards the sound-absorbing tubular wall 8. The wall 6 can in turn be of the sound-absorbing type. The sound-absorbing surfaces 6 and 8, of the known type, are, for example, drilled with a pitch between the holes of approximately 3 mm.

The second Joule effect heater device 11 comprises several heating sectors independent of one another installed angularly around the inner annular wall 6. Each heating sector is divided into several areas for delivering a different amount of thermal energy.

They are provided sensors (not shown) adapted to detect the Ti temperature of the first internal wall 6. The first and second heater devices 10 and 11 are both protected by a coating layer that protects them from erosion and impact.

Still according to the present invention exclusively between the second inner annular wall 6 and the peripheral wall 8-a of the sound-absorbing tubular wall 8 a discontinuity element 12 is provided that is configured to perform the detachment of the liquid film F flowing on the inner annular wall 6 by means of the kinetic speed of the airflow sucked by the engine directing the atomized water particles G towards the engine itself.

In the example shown, the discontinuity element consists of an annular groove 13 extending for 360 degrees between facing edges of the inner annular wall 6 and the sound- absorbing tubular wall 8. The water film entering the annular groove 13 performs nebulization thereof.

Alternatively, the discontinuity element may consist of an annular protuberance 13 (not shown) extending for 360 degrees between facing edges of the inner annular wall 6 and the sound-absorbing tubular wall 8.

The sound-absorbing walls 6 and 8 are covered by a hydrophobic/ice phobic lining (of the known type, i.e. of the passive type that does not require external energy other than natural forces, such as gravity, wind or surface tension, to induce water/ice detachment or mitigate accumulation/formation thereof. A hydrophobic/ice phobic lining is generally made from a paint that is applied using known technologies) configured to make any water particles flow towards the rotating parts of the engine. An ice detection system 15 is provided on the front annular portion 4 comprising a plurality of optical fibres 16 each of which has a first end 16-a which passes through a hole drilled in the front annular portion 4 and is coplanar (flush) with the inner annular wall 6 and a second end 16-b which communicates with a light radiation generator/detector 16-c (such as a laser source) adapted to detect the reflected/refracted radiation from the ice that covers the inner tubular wall 6 and therefore the ends 16-a.

An electronic control device 18 (not necessarily housed in the wing as schematically shown but anywhere in the aircraft) is provided that communicates with the ice detection system 15 and receives the value of Te and Ti temperatures.

The electronic control device 18 also cooperates with other ice detector devices 16-d arranged on the aircraft and is configured to receive flight data of the aircraft, such as speed, altitude, air temperature, pressure, angle of attack, etc. as well as meteorological data (presence of clouds, information about the state of the cloud (water and ice content, temperature, etc.) The electronic control device 18 controls the first and second Joule effect heater devices 10, 11 to perform an ice removal operation.

The electronic control device 18 is adapted to determine, based on data from the meteorological radar and based on flight data, the type of clouds and information on the state of the clouds (water and ice content, temperature) which the aircraft is going to pass through. Based on the data thus determined, the electronic device 18 is configured to calculate in an open-loop and in real-time the value of the electric energy that the heater device 10 and 11 must supply to obtain a target temperature Te-target, Ti-target for the first outer annular wall 5 and the second inner annular wall 6 which guarantees the elimination of ice. The calculation is carried out knowing the mathematical physical model which represents an input-output model having as input the electric energy absorbed by the first and second Joule effect heaters 10/11 and as output the temperature of the first outer annular wall 5 and of the second outer annular wall 6. The result of the calculation is compared with the one loaded in the database (memory ROM) of the corresponding certifying electronic control device for the flight condition. The value of the electric energy defined by the flight condition loaded in the control unit database (expected) is the value sent to the heater device 10 and 11. The target temperature Te-target, Ti-target is compared with the temperature Te, Ti measured on the first outer annular wall 5 and on the second outer annular wall 6 and the error between the temperatures is used to control in a closed-loop (e.g. by a PID controller of the known type) the temperature itself in real-time.

In particular, the electronic control device 18 is configured to keep the first heater device 10 switched-off for a time interval following the engine start-up allowing, during the flight of the aircraft, the growth of ice on the external profile up to a certain thickness, and after such time interval has elapsed, the first heater device 10 is switched-on with an ON/OFF type of alternating operation so that a constant temperature is maintained within a regulation interval (ON/OFF De-ice cycling system). keep the second heater device 11 switched-on continuously following the engine start-up (anti-ice constant ON running wet).

The heater device is controlled by the electronic control device 18 by controlling the voltage or current or resistance.

If a current control is operated, it can be regulated by a law that takes into account the temperature Te or Ti.

The advantages of the device of the present invention are clear from the foregoing. Based on numerical modelling and on the tests carried out by the Applicant, it was verified that a synergistic effect is created between the first Joule effect heater device 10, the second Joule effect heater device 11, and the discontinuity element 12 and the hydrophobic/phobic ice treatment 8. This synergy helps reduce the power consumption required by the anti-icing system to the aircraft because it decreases the surface area of the engine intake opening exposed to ice formation in known ice flight conditions. The presence of the ice detection system 15 on the front annular portion 4 allows the performance of the anti-icing system to be controlled.

With reference to figure 3 and 4, the discontinuity element 20 is formed by a detachment edge 20 of the second internal annular wall 6 which forms a step with respect to the external surface 8b of the tubular noise-reducing wall 8. The external surface 8-b of the sound-absorbing tubular wall 8 has a radial distance greater than the radial distance of the detachment edge 20. The step improves the detachment of the film of water.

As shown in figures 3 and 4, the detachment edge 20 has a sawtooth pattern and is limited by a plurality of adjacent straight segments 20-a, 20-b which form internal angles varying from 10 to 70 degrees. REFERENCE NUMBERS

1 anti-icing device

2 intake opening

3 engine nacelle 4 front annular portion

5 first outer annular wall

6 second inner annular wall

7 curved profile

8 sound-absorbing tubular wall 9 suction line

10 first Joule effect heater device

11 second Joule effect heater device

12 discontinuity element

13 annular groove 14 hydrophobic/ice phobic lining

15 ice detection system

16 optical fibres 16-a first end 16-b second end 17 radiation generator/detector

18 electronic control device