Boundary layer suction arrangement

Abstract

A suction arrangement for drawing off a boundary layer on an aircraft comprises a suction arrangement including an outer skin having suction surfaces in critical flow areas, and at least one air breathing engine providing suction. Bleed air is drawn from a comparatively high-pressure region of the engine by means of a branch line and the bleed air is used for driving a turbine of at least one turbo-supercharger assembly. A compressor of the turbo-supercharger assembly or assemblies serves as the suction source for drawing off a boundary layer at the suction surfaces in critical flow areas.

Description

FIELD OF THE INVENTION

The field pertains to a suction arrangement for drawing off boundary layers on an aircraft with a structure, the outer skin of which contains suction surfaces in critical flow areas, and with at least one air breathing engine, from which the suction power required for drawing off the boundary layer is obtained.

BACKGROUND OF THE INVENTION

A suction arrangement of the above-described type is known from DE 198 20 097 C2. In this known arrangement, the suction power for drawing off the boundary layer is generated by a jet pump arranged in the main flow of the engine. This suction arrangement provides the advantages that no moving parts are required in order to generate the suction power for drawing off the boundary layer, and that the arrangement consequently is highly unsusceptible to defects. However, one significant disadvantage of this known suction arrangement can be seen in the fact that a substantial power loss occurs due to the placement of the jet pump in the main flow of the engine. This power loss also cannot be completely prevented when the suction arrangement is not needed.

SUMMARY OF THE INVENTION

It is one object to develop a suction arrangement for drawing off boundary layers that makes it possible to achieve a highly efficient power conversion and to prevent power losses in operating states, in which the suction arrangement is not needed. In a suction arrangement for drawing off boundary layers this object is attained by suctioning bleed air from the high-pressure region of an engine using a branch line used for driving a turbine of a turbo-supercharger assembly. The compressor (also referred to as turbo pump) has a branch line that serves as the suction source for drawing off the boundary layer.

A turbo-supercharger assembly ensures a highly efficient power conversion, and the connection of a branch line for withdrawing the bleed air from the engine may be realized in such a way that no power loss occurs in the engine when the branch line is shut off, also improving efficiency.

In a bypass engine having a bypass structure 103, as illustrated in FIG. 2 with a core flow and a bypass flow, it is advantageous to withdraw the bleed air in the region of the high-pressure compressor because this makes it possible to obtain the maximum power possible for the turbo-supercharger assembly.

In one example, the pressure line of the compressor (turbo pump) of the turbo-supercharger assembly opens into the main flow of the engine at a point of low pressure. This location contributes to maintaining a low pressure differential between the suction channel system of the arrangement for drawing off boundary layers and the outlet of the pressure line, i.e., the pressure differential to be overcome by the compressor of the supercharger assembly, such that the power generated by the compressor may be optimally utilized.

In another example, several low-power supercharger assemblies are used instead of one heavy-duty turbo-supercharger assembly, wherein these supercharger assemblies are accommodated in the region of the engine suspension and/or the engine fairing. The advantage of these variations include comparatively low flow and heat losses due to shorter pressure and suction lines that may be used for connecting the turbine of the turbo-supercharger assembly to the engine.

It is also advantageous to realize the turbo-supercharger assembly in the form of a single-shaft machine having a plurality of turbo-supercharger assemblies using a common shaft, because machines of this type are available in the form of components with a simple design that can be inexpensively manufactured.

BRIEF DESCRIPTION OF THE FIGURES

Examples are described below with reference to the enclosed figures.

FIG. 1 illustrates an aircraft wing with suction surfaces for drawing off the boundary layer, as well as the aircraft engine arranged underneath said wing,

FIG. 2 illustrates a schematic cross section through the aircraft engine according to FIG. 1 with a suction arrangement according to the invention for drawing off boundary layers.

DETAILED DESCRIPTION

The examples described and drawings rendered are illustrative and are not to be read as limiting the scope of the invention as it is defined by the appended claims.

FIG. 1 shows an example of an aircraft structure, the outer skin of which contains suction surfaces in critical flow areas, namely an aircraft wing 4 that is provided with suction surfaces 41, 42. An engine 1 is mounted on the aircraft wing 4 by means of a suitable engine suspension 12. A suction line 23 for drawing off a boundary layer through the suction surfaces 41, 42 leads from the wing 4 to a region of the engine 1 that is identified by the reference symbol Z. A suction arrangement for drawing off boundary layers is provided in this region Z. It should be noted that the aforementioned suction surfaces may also be provided for drawing of boundary layers on the engine fairing.

FIG. 2 shows a schematic section through the region Z of the aircraft engine. The aircraft engine is identified as a whole by the reference symbol 1. This engine consists of a so-called bypass engine with a main flow H that is divided into a core flow K and a bypass flow M downstream of a so-called front fan. The core flow K flows to the engine outlet via the high-pressure compressor 11 and a high-pressure turbine. A high-pressure region in the vicinity of the high-pressure compressor 11 is identified by the reference symbol P. A branch line 10 for withdrawing high-pressure bleed air is connected to the engine 1 in this region. The branch line 10 leads to a turbo-supercharger assembly 2. The turbo-supercharger assembly is realized in the form of a single-shaft machine with a turbine 20 and a compressor (turbo pump) 24. The bleed air withdrawn from the high-pressure compressor 11 drives the turbine 20 and is then returned into the main flow H of the engine 1 via an exhaust line 21. The compressor 24 of the turbo-supercharger assembly 2 that is driven by the turbine 20 conveys the air from the suction line 23 into the main flow H of the engine 1 via a pressure line 25, wherein the pressure line 25 opens into the main flow H of the engine at a point of low static pressure U.

In an alternative example, instead of utilizing one heavy-duty turbo-supercharger assembly 2, several smaller turbo-supercharger assemblies are used. Such smaller supercharger assemblies are identified by the reference symbols 2a and 2b and drawn with broken lines in FIG. 2, for example. An advantage of utilizing smaller turbo-supercharger assemblies is that such assemblies are more readily accommodated in the engine suspension 12 or the engine fairing as shown in FIG. 2.

It should be noted that the term “comprising” does not exclude other elements or steps and the “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined.

It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

Alternative combinations and variations of the examples provided will become apparent based on the disclosure. It is not possible to provide specific examples for all of the many possible combinations and variations of the embodiments described, but such combinations and variations may be claims that eventually issue.

LIST OF REFERENCE SYMBOLS

• 1 Aircraft engine
• 2 Turbo-supercharger assembly
• 2 a Low-power turbo-supercharger assemblies
• 2 b Low-power turbo-supercharger assemblies
• 4 Wing
• 41 Suction surface of 4
• 42 Suction surface of 4
• 10 Branch line
• 11 High-pressure compressor
• 12 Engine suspension
• 20 Turbine
• 21 Exhaust line
• 23 Suction line
• 24 Compressor (turbo pump)
• 25 Pressure line of 24
• H Main flow
• K Core flow
• M Bypass flow
• P High-pressure region
• U Low-pressure region
• Z Region of 1 with the suction arrangement for drawing off boundary layers

Claims

1. A suction arrangement for drawing off a boundary layer on an aircraft with a structure, comprising: an outer skin including suction surfaces in critical flow areas;an air breathing bypass engine, the bypass engine comprising a nacelle, a front fan, a bypass structure, a bleed air branch line, and an engine outlet downstream from the front fan, a bypass structure dividing a main flow entering the nacelle and exiting the engine outlet into a core flow and a bypass flow, wherein the core flow of the bypass engine flows to the engine outlet via a high-pressure compressor region and a high-pressure turbine region, wherein an inlet of the bleed air branch line withdraws bleed air from a the high-pressure compressor region of the bypass engine and the bleed air from the bleed air branch line drives a turbine of a turbo-supercharger assembly, the turbo-supercharger assembly having a compressor serving as a suction source fluidically coupled to the suction surfaces of the outer skin for drawing off the boundary layer, wherein a pressure line from the compressor of the turbo-supercharger assembly fluidically couples the compressor of the turbo-supercharger assembly to the main flow exiting the engine outlet of the bypass engine at a location of lower static pressure than the high-pressure region of the bypass engine, and wherein an exhaust line fluidically couples an exhaust flow of the turbine of the turbo-supercharger assembly to the main flow exiting the engine outlet of the bypass engine.

2. The suction arrangement of claim 1, wherein at least one additional turbo-supercharger assembly is utilized and each of the turbo-supercharger assemblies are accommodated in a region of an engine suspension structure, an engine fairing, or both.

3. The suction arrangement of claim 2, wherein each of the turbo-supercharger assemblies use a common shaft.