The present invention relates generally to fan engines, more particularly, to acoustic liners and heat exchangers for electric fan engines.

Among the top challenges for today's aviation sector is to move towards a means of transport with improved environmental performance that is more efficient and less reliant on fossil fuels. Electric and hybrid-electric propulsion are seen today as among the most promising technologies for addressing these challenges .

The core part of an electric aircraft propulsion system is an electric fan engine, which require cooling and heat rejection to ambient atmosphere. Additionally, an acoustic noise that appears due to operation of the electric aircraft propulsion system should be absorbed.

An electric fan engine 1 (i.e. electric fan propulsion) - shown on FIG 1 - consists of an electric motor 2 (i.e. an electric drive) that are arranged along a central longitudinal axis 10 and connected by a shaft 4. The electric drive 2 drives a fan 3 by a shaft 4. Additionally, the electric fan engine 1 may comprise a gearbox 5 between the fan 3 and the shaft 4 to provide speed and torque conversions from the electric drive 2 to the fan 3. Also, the electric drive 2 may comprises power electronics .

The principle of operation of such electric fan engine is rather simple: While the electric drive 2 operates, it spins the shaft 4 and therefore, the fan 3 spins as well. The fan 3 powered by.the electric drive 2 creates flow of air 7. The air flows through the fan 3 and around it.

Electric fan engines 1 can be divided into at least two categories: ducted electric fan engines and unducted electric fan engines. A ducted electric fan engine - shown on FIG 2 - is the engine with a cylindrical shroud or duct 6 in which the fan 2 and sometimes electric drive 2 are mounted. The duct 6 reduces losses in thrust from the tips of the fan blades and varying the cross-section of the duct 6 allows the designer to advantageously affect the velocity and pressure of the airflow according to Bernoulli's principle. In an unducted electric fan engine there is no shroud or a duct around the fan.

Additionally, electric fan engines 1 can have a fan 3 positioned forward to the electric drive 2 (shown on FIG 1, 2) or behind the electric drive 2 (shown on FIG 3) relative to the flow 7 of the air. Typically, electric fan engines 1 with the fan 3 positioned behind the electric drive 2 is unducted electric fan engines.

Still any of mentioned above various types of electric fan engines / propulsions requires cooling, in particularly cooling of the electric drive 2, and heat rejection to ambient atmosphere as well as absorption of the acoustic noise created by the electric fan engine 1. Since electric fan engine concept is quite new there are not any proven solution existing to solve this problem.

The most obvious way to cool the electric drive 2 is to reject heat though the electric drive cowl to the atmosphere. But heat transfer rate though the wall of the cowl is limited by surface heat transfer coefficient and surface area of the cowl and might be insufficient for such a powerful system.

Additionally, components of such electric fan engine also produce acoustic excitations when operating, particularly the fan as it rotates at a given angular speed. Absorbing these acoustic excitations are a critical design consideration, as they may cause excessive external noise or vibrations in engine components not designed to absorb them. A conventional acoustic liner is often used to absorb a portion of these acoustic excitations. Such conventional acoustic liners can be located at various points along the fan duct.

In the US 2016/0017810 A1 (prior art) patent application it is claimed that excessive heat can be removed to the ambient atmosphere from an gas turbine engine through an acoustic liner heat exchanger 8 (shown on FIG 4), that is arranged on the surface of the elements of a gas turbine engine. The acoustic liner heat exchanger 8 comprises an acoustic structure 9, which comprises cells 11 arranged perpendicular to and between a perforated front plate 12 and a back plate 13, and a heat exchanger 14 that includes one or more channels 15 for a coolant 16.

It is claimed that the movement of the airflow 17 through the perforated front plate 12 of the acoustic structure 8 and inside the cells 11 due to main flow pressure oscillations have positive effect on the heat transfer rate. This is true in comparison with a case of imperforated front plate 12 of the acoustic structure where cells 11 located underneath and covered by back plate 13.

However, cell structure represents thermal resistance, which can hardly be compensated by oscillating flow movement through the perforated front plate and inside the cells leading to formal increase of heat transfer surface area. Anyway, heat transfer through such acoustic liner heat exchanger might be insufficient for powerful drive and power electronics of electric propulsion system, in particular for electric airplane propulsion system.

Accordingly, the object of the present invention is to provide another variant of the acoustic liner for an electric drive and a cooling system with the acoustic liner for an electric fan engine to maximize heat transfer. Therefore, the efficiency of the heat exchanging acoustic liner and the cooling system is improved.

The object of the present invention is achieved by a heat exchanging acoustic liner for an electric fan engine, as defined in claim 1 and a cooling system with a heat exchanging acoustic liner for an electric fan engine as defined in claim 6. Advantageous embodiments of the present invention are provided in dependent claims. Features of claims 1 and 6 can be combined with features of dependent claims, and features of dependent claims can be combined together.

In an aspect of the present invention, a heat exchanging acoustic liner for an electric fan engine is presented. The heat exchanging acoustic liner for an electric fan engine comprises at least one acoustic structure for the absorption of acoustic excitation and at least one coolant channel for heat exchange across the at least one acoustic structure operatively associated with the least one acoustic structure.

The at least one acoustic structure comprises cells arranged in direction to and between a front plate and a back plate, wherein, in accordance with the present invention, the both plates - the front and the back ones - are perforated. Furthermore, such at least one acoustic structure is adopted to provide airflows to the at least one coolant channel.

The at least one coolant channel for heat exchange across the at least one acoustic structure operatively associated with the back plate of the at least one acoustic structure.

In another aspect of the present invention, a cooling system with a heat exchanging acoustic liner for an electric fan engine, wherein the electric fan engine comprises an electric drive and a fan that are arranged on a shaft and wherein the fan is actuated by the electric drive, is presented.

The cooling system comprises at least one heat exchanging acoustic liner and a compressor to provide airflows through the at least one acoustic structure to the at least one coolant channel of the at least one heat exchanging acoustic liner.

As it was described above, the at least one heat exchanging acoustic liner comprises at least one acoustic structure for the absorption of acoustic excitation, wherein the at least one acoustic structure comprises cells arranged in direction to and between a front plate and a back plate wherein the front plate and the back plate are perforated, and at least one coolant channel for heat exchange across the at least one acoustic structure operatively associated with the back plate of the at least one acoustic structure.

Furthermore such at least one acoustic structure is adopted to provide airflows to the at least one coolant channel.

The present invention is based on the insight that the fan creates a flow of the air during its operation. Since the heat exchanging acoustic liner is located on the cowl of the electric drive, on the surface of the heat exchanging acoustic liner appears a boundary layer of flow of the air. After suction from this boundary layer of flow of the air created by the fan, airflows are ejected through the perforation holes of the front plate into the acoustic structure and further through the back plate into the coolant channel in the shape of distributed discrete airflows. These distributed discrete airflows imping the outer surface of the coolant channel that covers electric drive components that are supposed to be cooled down. Impinging cooling is known as one of most effective cooling techniques often used in turbine blades cooling due very high heat transfer rates achieved via jets surface interaction destroying the boundary layer and minimize the thermal resistance of the latter one. Acoustic excitations may lead to formation of oscillating airflows that can even increase the performance.

Furthermore, the compressor of the cooling system creates additional pressure drop that increase airflows through the at least one acoustic structure to the coolant channel of the at least one heat exchanging acoustic liner.

In addition to the cooling of the electric drive and reducing acoustic noise, suction of boundary layer of flow of the air from the surface of the heat exchanging acoustic liner through perforated acoustic structure allows reducing friction losses on the housing of the electric drive as a result of reduced boundary layer thickness. Moreover, ejection of the airflows through the at least one coolant channel in the rear part of electric drive reduces end losses.

Thus, the present invention is proposed to provide a heat exchanging acoustic liner for an electric fan engine and a cooling system with a heat exchanging acoustic liner for an electric fan engine to maximize heat transfer together with acoustic excitation absorption and reduce friction loses of the electric fan engine.

Further embodiments of the present invention are subject of the further sub-claims and of the following description, referring to the drawings. In a possible embodiment of the heat exchanging acoustic liner for an electric fan engine the cells, the front plate and the back plate of the at least one acoustic structure are arranged in such way that they provide impinging airflows going through the back plate of the at least one acoustic structure into the at least one cooling channel.

Choosing appropriate sizes of perforation and mutual arrangements of perforation in the front and the back plates allows providing impinging airflows going through the back plate of the acoustic structure into the coolant channel. Impinging cooling is known as one of most effective cooling techniques due very high heat transfer rates achieved via jets surface interaction destroying the boundary layer of the surface the jets imping on and minimize the thermal resistance of the latter one.

Therefore, the electric drive can be effectively cooled with minimum amount of cooling air due to highly effective impinging cooling implementation.

In other possible embodiment of the heat exchanging acoustic liner, the at least one coolant channel is arranged by the back plate of the at least one acoustic structure and a surface of the electric drive that is supposed to be cooled down.

In such embodiment the airflows go through the perforated back plate of the acoustic structure impinging directly the surface of the electric drive that is supposed to be cooled down. Knowing the efficiency of the impinging cooling such embodiment allows direct cooling of the surfaces that require such cooling. Therefore, the efficiency of such cooling is increasing .

In enhanced embodiment of the heat exchanging acoustic liner, the cells of the acoustic structure are honeycomb shaped in cross-section .

Honeycomb structures, one of nature's unique designs, are widely used in such diverse applications as automotive, packaging, high-pressure containers, lightweight aerospace wing panels, and engine nacelles, and high-temperature turbine seals for ground power and aircraft jet engines, taking advantage of honeycomb's high structural strength with minimum weight.

Such honeycomb shaped cells are the most optimal structure to be manufactured and can ensure uniform and complete filling of the entire space of the acoustic structure between the front plate and the back plate.

In enhanced embodiment of the heat exchanging acoustic liner, the cells, the front plate and the back plate of the at least one acoustic structure are fabricated using an additive manufacturing method.

Typically, components with small moving pieces require strict manufacturing tolerances and highly controlled assembly processes to reduce the number of component defects. Using the additive manufacturing technology of today, manufacturers can print entire components, moving pieces and all, with extremely precise tolerances. Thus, improving product quality and reducing failure risk.

In other possible embodiment of the cooling system with a heat exchanging acoustic liner for an electric fan engine, the compressor is arranged on the shaft and actuated by the engine drive .

To provide higher reliability the compressor can be placed on the same shaft as the fan. In other words, the electric drive that brings the fan in movement will actuate the compressor as well. Operation of the compressor requires insignificant amount of energy that do not affect the performance of the electric fan engine in whole. On the other hand, such embodiment guarantees while the electric drive operates and requires cooling, the compressor actuated by the shaft does operate as well and, therefore, provides the required cooling to the electric drive.

Such embodiment allows to guarantee that the cooling system works at the same time as the electric fan engine operates.

In case of independent source of energy for the compressor to be kept working this source should be very reliable especially when such cooling system is used for specific applications - for example for airplanes.

In other enhanced embodiment of the cooling system the cells, the front plate and the back plate of the at least one acoustic structure of the at least one heat exchanging acoustic liner are arranged in such way that they provide impinging airflows going through the back plate of the at least one acoustic structure into the at least one coolant channel.

Impinging cooling is known as one of most effective cooling techniques due very high heat transfer rates achieved via jets surface interaction destroying the boundary layer and minimize the thermal resistance of the latter one. Therefore, this feature allows providing more effective cooling.

In other enhanced embodiment of the cooling system the at least one coolant channel of the at least one exchanging heat acoustic liner is arranged by the back plate of the at least one acoustic structure and a surface of the electric drive that is to be cooled down. Therefore, such impinging airflows go directly to the surface of the electric drive to be cooled down.

In other enhanced embodiment of the cooling system the cells of the at least one acoustic structure of the at least one heat exchanging acoustic liner are honeycomb shaped in cross- section.

The honeycomb structure is an optimal structure to evenly fill the space between the front and the back plates of the at least one acoustic structure and provide the airflows through the acoustic structure into the at least one coolant channels.

In other enhanced embodiment of the cooling system, the at least one acoustic structure of the at least one heat exchanging acoustic liner are fabricated using an additive manufacturing method.

Typically, components with small moving pieces require strict manufacturing tolerances and highly controlled assembly processes to reduce the number of component defects. Using the additive manufacturing technology of today, manufacturers can print entire components, moving pieces and all, with extremely precise tolerances. Thus, improving product quality and reducing failure risk.

For a more complete understanding of the present invention and advantages thereof, reference is now made to the following description taken in accompanying drawings. The invention is explained in more details below using exemplary embodiments which are specified in the schematic figures of the drawings, in which:

FIG. 1 schematically illustrates an electric fan engine;

FIG. 2 schematically illustrates a ducted electric fan engine;

FIG. 3 schematically illustrates an embodiment of the electric fan;

FIG. 4 schematically illustrates an acoustic liner heat exchanger (prior art);

FIG. 5 schematically illustrates a heat exchanging acoustic liner for an electric fan engine in accordance with the present invention;

FIG. 6 schematically illustrates an embodiment of the heat exchanging acoustic liner in accordance with the present invention;

FIG. 7 schematically illustrates cells of the acoustic structure that are honeycomb shaped in cross-section;

FIG. 8 schematically illustrates an embodiment of the heat exchanging acoustic liner in accordance with the present invention;

FIG. 9 schematically illustrates a cooling system with a heat exchanging acoustic liner for an electric fan engine in accordance with the present invention;

Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be noted that the illustrated embodiments are intended to explain, and not to limit the invention. It may be evident that such embodiments may be practiced without these specific details.

FIG 5 illustrates a heat exchanging acoustic liner 100 for a fan electric engine 1 to provide cooling for a fan electric engine 1, in particularly to the electric drive 2, in accordance with the present invention.

The heat exchanging acoustic liner 100 for the fan electric engine 1, in particularly for the electric drive 2, comprises at least one acoustic structure 101 for the absorption of acoustic excitation and at least one coolant channel 150 for heat exchange across the at least one acoustic structure 101.

The at least one acoustic structure 101 comprises cells 102, a front plate 103 and a back plate 104. The front plate 103 and the back plate 104 are perforated and have perforation holes 105 and 106 respectively.

The cells 102 are arranged in direction to and between the front plate 103 and the back plate 104. The cells 102 can be perpendicular to the front plate 103 and the back plate 104 (as it is shown on FIG 5) or can be made inclined to the front and back plates 103, 104 (as it is shown on FIG 6). In case the cells 102 are inclined to the front and back plates 103, 104, it is preferable to have such inclination at an acute angle to the central longitude axis 10. Additionally, in such case, it is preferable to have the perforation holes 105, 106 made inclined at the same angle to the central longitude axis 10. It is possible to vary an efficiency of the cooling by changing the angle of inclination of cells 102. - since the impinging will be affected.

The cells 102 can be of different shape and size. However, it is preferable to have cells 102 that are honeycomb shaped in cross-section as it is shown on FIG 7. This honeycomb form of the cells 102 allows to evenly fill with the cells 102 the entire space between the front and back plates 103, 104. Additionally, it is a conventional way to manufacture such honeycomb shaped in cross section cells.

The perforation holes 105 and 106 of the front 103 and back 104 plates respectively can be of the same diameter or of different diameters. However, in preferable case the perforation holes 105 of the front plate 103 should be not smaller than the perforation hole 106 of the back plate 104 to provide increasing of airflows 110 going through the perforation hole 106 of the back plate to the coolant channel 150.

Another topic is location of the perforation holes 105 and 106 relative to the cells 102. Such placement should be done based on the required conditions of the cooling. However, in preferable case the perforation holes 105 and 106 should be located under each other and preferable in the center of each cell 102. However, in some cases, some cells 102 can be performed without perforation holes at all on purpose. For example, the acoustic structure 101 can be divided on sections by using a chain of cells 109 without perforation holes.

The number of cells 102, their size and shape, as well as distance between the front plate 103 and the back plate 104, the size of perforation holes 105, 106, mutual arrangements of the perforation holes 105 of the front plate 103 and the perforation holes 106 of the back plate 104 should be defined by experts.

All parameters of the acoustic structure 101, including parameters mentioned above, should be chosen based on the particular conditions, including particular electric fan engine 1, the acoustic structure 101 is supposed to be used for.

Such acoustic structure 101 including the cells 102, the front plate 103 and the back plate 104 can be fabricated using an additive manufacturing method.

According to the present invention the at least one coolant channel 150 for heat exchange across the at least one acoustic structure 101 operatively associated with the back plate 104 of the at least one acoustic structure 101. Moreover, the at least one acoustic structure 101 is adopted to provide airflows 107, 110 to the at least one coolant channel 150.

The at least one coolant channel 150 can be formed with the back plate 104, that is perforated, and a coolant channel back plate 108. The heat exchanging acoustic liner 100 can have just one coolant channel along one or more acoustic structures 101. Or there can be plurality of the coolant channels 150 arranged in the heat exchanging acoustic liner 101 associated for one or more acoustic structures 101.

It can be plurality of the coolant channels 150 can be arranged along the central longitudinal axis 10 (as it is shown on FIG 8) and / or be in the transverse direction. The coolant channels 150 of the plurality can be of different size (length and width).

In the enhanced embodiment of the present invention the coolant channel back plate 108 of the coolant channels can de directly adjacent to the electric drive 2 to be cooled down, or even the surface of the electric drive 2 can work as the coolant channel back plate 108. Such construction allows proving direct cooling of the electric drive. Other way is to adjacent the coolant channel back plate 108 to the further cooling system, for example with a coolant other that air.

The number of the acoustic structures 101 in the heat exchanging acoustic liner 100 should be defined by experts and depends on the particular electric drive 2 it is supposed to be used, what surface should be cooled down and other parameters of the particular system such heat exchanging acoustic liners 100 are supposed to be used.

Also the heat exchange acoustic liner 100 can have different combinations of the acoustic structures 101 and the coolant channels 150: the heat exchange acoustic liner 100 can comprise several coolant channels 150 that are adjacent to one acoustic structure 101 or vise versa one coolant channel 150 adjacent to several acoustic liners 101. It depends on the conditions the heat exchanger acoustic liner 100 should work and on what parameters the heat exchanger acoustic liner 100 should provide .

According to the enhanced embodiment of the present invention the cells 102, the front plate 103 and the back plate 104 of the at least one acoustic structure 101 are arranged in such way that they provide impinging airflows 110 going through the back plate 104 of the at least one acoustic structure 101 to the coolant channel 150. The heat exchanging acoustic liner 100 works the following.

In general, the heat exchanging acoustic liner 100 should be placed / attached to /on the surface to be cooled down, for example to the surface of the electric drive 2, therefore the coolant channel back plate 108 is in direct contact with the surface to be cooled down. The heat exchanging acoustic liner 100 is placed in such way that the front plate 103 of the acoustic structure 101 are blown by flow of the air 7.

The flow of the air 7 blows along the front plate 104 of the acoustic structure 101 of the heat exchanging acoustic liner 100.

Due to the existing acoustic excitations and differences of the pressure inside and outside of the acoustic structure 101, the airflows 107 go through the perforation holes 104 of the front plate 103 into the cells 102 and further through the perforation holes 105, i.e. through the acoustic structure 101, into the coolant channel 150.

In enhanced embodiment of the present invention, the acoustic structure 101 - in particular the cells 102, the perforated front 103 and back 104 plates - is arranged in such way that, at the exit of the perforation hole 106, the airflows 110 into the cooling channel 150 takes the form of impinging jets.

In this preferable case, after suction from the flow of the air 7 created by the fan 3, airflows 107 are ejected through the perforation holes 105 of the front plate 103 into the acoustic structure 101 and further through the back plate 104 into the coolant channel 150 in the shape of distributed discrete airflows. These distributed discrete airflows 110 imping the outer surface 108 of the coolant channel that covers electric drive 2 components that are supposed to be cooled down. Impinging cooling is known as one of most effective cooling techniques often used in turbine blades cooling due very high heat transfer rates achieved via jets surface interaction destroying the boundary layer and minimize the thermal resistance of the latter one.

Existence of the acoustic excitations of the electric fan engine 1 may lead to formation of oscillating jet structures that can even increase the performance. FIG 9 illustrates a cooling system 200 with a heat exchanging acoustic liner 100 for an electric fan engine 2.

The cooling system 200 comprises one or more heat exchanging acoustic liners 100 and a compressor 201.

As it was described above the heat exchanging acoustic liner 100 comprises at least one acoustic structure 101 for the absorption of acoustic excitation and at least one coolant channel 150 for heat exchange across the at least one acoustic structure 101.

Each acoustic structure 101 comprises cells 102 arranged in direction to and between a front plate 103 and a back plate 104. Wherein the front plate 103 and the back plate 104 are perforated.

The cells 102 can be of different shape. However, in the preferable case the cells 102 of the at least one acoustic structure 101 of the at least one heat exchanging acoustic liners 100.

The at least one acoustic structure can be manufactured using an additive manufacturing method.

Moreover, the acoustic structure is adopted to provide airflows 107, 110 from outside of the heat exchanging acoustic liner 100 to the coolant channel 150 - in other words, from outside the acoustic structure 101 through the perforation holes 105 of the front plate 103 into the cells 102, and, further, through the perforation holes 106 of the back plate 104 into the coolant channel 150.

The at least one coolant channel 150 is operatively associated with the back plate 104 of the at least one acoustic structure 101.

The compressor 201 is to provide airflows 107, 110 from the outside of the heat exchanging acoustic liner 100 into the coolant channel 150 of the heat exchanging acoustic liner 100.

The compressor 201 still need an energy to be actuated. The compressor 201 may have its own source of energy to provide power for its operation. The characteristics of the compressor 201, for example size, power provided, and power required for operation, should be defined by experts and depends on working conditions of the electric fan engine 1 for which the cooling system 200 is supposed to be used.

For some applications - for example, for the electric fan engines used in airplanes - such power source for the compressor 201 should be very reliable. Such applications bring higher requirements for the reliability.

To provide higher reliability for the whole cooling system 200, the compressor 201 can be arranged on the shaft 4 and actuated by the same electric drive 2 that provides rotation the fan 3. Using such arrangements for the compressor 201, it means that the compressor 201 works and provides the airflow 107 through the at least one acoustic structure 101 while the electric drive 2 works and requires cooling.

In some embodiments the cooling system 200 can be arrange in such way that the coolant channel 150 is arranged by the back plate 104 of the acoustic structure 101 and the electric drive 2, i.e. the surface of the engine component to be cooled down. In other words, the coolant channel back plate 108 is the surface of the engine component to be cooled down. In case it is required the walls of the coolant channels 150 - i.e. walls that separate cooling channels 150 between each other can be created directly on the surface of the electric drive 2 and / or on the surface of any other electric component of the electric drive 2 that to be cooled down. It can be done with using additive manufacturing methods.

The cooling system 200 can comprise a plurality of the coolant channels 150 (as it is shown on FIG 8, 9). The characteristics of the coolant channels 150 should be chosen based on the need to ensure maximum efficiency of the impinging jets.

It relates to the fact that efficiency of impinging cooling decreases with the length of the coolant channel 150. This is since the impinging airflows 110 hit the coolant channel back plate 108 and further moves along the coolant channel 150 along the central longitude axis 10 out of the electric drive 2 (such airflows shown on FIG 5 as 111), and therefore, affect the following airflows 110. So that, at some point of the coolant channel 150, impinging airflows 110 do not reach the coolant channel back plate 108. Therefore, the effect of impinging cooling decreases along the central longitude axis 10.

Therefore, at some point of the coolant channel 150 the airflows 111 that is parallel to the central longitude axis 10 should be removed from the coolant channel 150. It can be arranged by using a plurality of cooling channels 150 along the longitude axis 10 as it is shown on FIG 9.

Another embodiment of the cooling system 200 can comprise the coolant channels 150 located not directly on the components (f.e. a housing, a cowl) of the electric drive 2 to be cooled down, but on the surface of the further cooling system, for example, additional cooling channels with other coolant (f.e. with liquid in it). Therefore, the impinging airflows 110 will be cooling the liquid in this further cooling system while the liquid will be cooling the electric drive 2. Therefore, several different cooling systems can be combined and, consequently, the efficiency of the cooling can be increased.

The cooling system 200 with a heat exchanging acoustic liner 100 for an electric fan engine works as follows.

The electric fan engine 1 that comprises an electric drive 2 and a fan 3 that are arranged on a shaft 4 wherein the fan 3 is actuated by the electric drive 2. While the electric fan engine 1 works the flow of the air 7 blows over the electric drive 2 or a cowl / housing of the electric drive 2. And the electric drive 2 will require cooling. Additionally, some acoustic excitations will appear and will need to be absorbed. In such cases the cooling system 200 disclosed in the present invention can be used to cool the electric drive 2 and to get the acoustic excitations under.

Due to the perforated front plate 103, the airflows 107 will get into the cells 102 and further go through the back plate 104 forming impinging airflows 110. Due to the presence of the compressor 200 located behind (in direction of the electric drive 2), there is difference of pressure of the air that exists on the surface of the heat exchanging acoustic liner 100 and in the coolant channel 150. Therefore, such difference of the pressure provides airflows 107, 110 through the acoustic structure 101. Additionally, acoustic excitations fabricated by the electric drive 2 and the fan 3 and possibly by other parts of the electric fan engine 1 contribute to the creation of such airflows 107, 110 through the acoustic structure 101 into the coolant channel 150 as well. Further due to the structure of the acoustic structure 101, after suction of the flow of the air 7 from the surface of the front plate 103, the airflows 107 are ejected to the acoustic structure 101 and further into the coolant channel 150 in the shape of distributed discrete airflows 110, impinging the coolant channel back plate 108. Impinging cooling is known as one of most effective cooling techniques often used in turbine blades cooling due very high heat transfer rates achieved via jets surface interaction destroying the boundary layer and minimize the thermal resistance of the latter one.

While the present invention has been described in detail with the reference to certain embodiments, it should be appreciated that the present invention is not limited to those precise embodiments. Rather, in view of the present disclosure which describes exemplary modes for practicing the invention, many modifications and variations would present themselves to those skilled in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of eguivalency of the claims are to be considered within their scope.

Reference numerals

1 - electric fan engine

2 - electric drive

3 - fan

4 - shaft

5 - gearbox

6 - duct

7 - flow of the air

8 - acoustic liner heat exchanger

10 - central longitude axis

11 - cells

12 - front plate

13 - back plate

14 - heat exchanger

15 - coolant channel

16 - coolant

17 - airflows

100 - heat exchanging acoustic liner

101 - acoustic structure

102 - cells

103 - front plate

104 - back plate

105, 106 - perforation holes 107, 110, 111- airflows

108 - coolant channel back plate

109 - cells

150 - coolant channel

200 - cooling system

201 - compressor