Metal/polymer laminate ducting and method of making same

(54) Title: METAL / POLYMER LAMINATED DUCT (57) Abstract:

AND METHOD FOR THEIR MANUFACTURE (30) Unionist Priority: 31/01/2007 us 11 / 700,797 (73) Owner (s): Senior Investments AG (72) Inventor (s): Leslie Fernandes (74) Attorney (s): Nellie Anne Daniel-Shores (86) International Order: pct US2OO8OO1198 de

29/01/2008 (87) International Publication: wo 2008 / 094577de

07/08/2008

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“METAL / POLYMER LAMINATED DUCT AND METHOD FOR ITS MANUFACTURING”

Fundamentals of the Invention

The present invention is generally related to duct structures for turbine engines and methods for their manufacture.

Related Technique

Gas turbine engines, especially those for aircraft propulsion applications, use ducts to extract air flow from part of the engine, for example, to provide a source of cooling air, which air flow must be returned to another part of the engine.

Such a structure that requires transport ducts is known as the air-oil cooler (to cool the lubricating oil for the engine). This device requires an inlet duct, which directs the cooling air, from the front (intake) of the turbine from a ventilation stream through the oil-air cooler. On the downstream side of the heat exchanger structure of the cooler, a discharge duct directs the “used” cooling air back into the ventilation stream.

The ducts that serve the air-oil cooler (and other such engine duct structures) typically need to be able to satisfy several design parameters: 1) the ducts must withstand temperatures ranging in the range and approximately -54 ° C (-65 ° F) ) to approximately 371 ° C (700 ° F); 2) the ducts must withstand relatively low pressure, for example, from approximately 55 to 124 kPa (8-18 psig); 3) the ducts must be fireproof and / or flame resistant; 4) the ducts must be resistant to vibration; 5) the ducts must be non-flammable; and 6) the ducts must be as light as possible.

Such internal engine duct structures have typically been formed as all-metal structures, often made from one or more high-performance materials, such as corrosion-resistant stainless steel (Cres) or titanium.

For example, Peyton et al., US 3,911,961 discloses the production of multilayer ducts for high temperature resistant ducts for aircraft, including external insulating sleeves formed from a sheet metal press and fabric impregnated with resin and an internal metal duct , separated by a space with air. Fischer et al., US 4,934,412 discloses a tubular cooling line for a turbine engine, which has an internal layer of thermosetting resin with fiber reinforcement, resistant to loads, surrounded by a thermal insulating layer of reinforced resin. fiber.

Norek, US 7,047,615 B2 discloses a method for producing turbine engine transport duct bodies without longitudinal welds by hydroforming two duct bodies one supported on the other with insufflating bellows fixed to the open ends of the duct body. This allows the manufacture of duct bodies with detailed characteristics and high pressure without using compression cylinders. Multilayer transit duct bodies can also be assembled with layers of different materials, for example, having a thermo-resistant layer within an outer layer of high resistance. They can also be assembled using cold shrinkage and thermal expansion. Additionally, anti-friction and anti-vibration coatings can be applied between the layers to improve performance.

It would be desirable to provide a duct structure, for example, for gas turbine engines, which is light, durable and resistant to heat, fire and vibration.

These and other desirable features of the invention will become apparent in view of the present specification, including the claims and drawings.

Summary of the Invention

The present invention comprises, in part, a laminated duct structure, for conducting air from a first location to a second location, in a gas turbine engine. The duct structure comprises an inner metallic layer; and a polymeric outer layer, attached to an outer surface of the metallic inner layer. Such a polymeric outer layer may be of fiberglass fabric impregnated with polyimide resin.

The inner metallic layer can be manufactured from one of the following materials: corrosion resistant steel; titanium. As mentioned, a preferred polymeric outer layer may comprise fiberglass fabric impregnated with polyimide resin.

The present invention also comprises, in part, a method for producing a laminated duct structure, for conducting air from a first position to a second position, in a gas turbine engine.

The method for producing a laminated duct structure comprises the steps of: forming the first and second portions of the first metallic inner layer, each having an inner surface and an outer surface;

forming the brittle first and second support components, for positioning within the first and second portions of the metallic inner layer;

positioning the first and second support members to structurally support the inner surface of each of the first and second portions of the first metallic inner layer, respectively;

aligning the first and second portions of the first metallic inner layer together; permanently joining the first and second portions of the first metallic inner layer together;

forming a polymeric outer layer on the outer surfaces of the first and second portions of the first metallic inner layer;

cure the polymeric outer layer; and removing the brittle first and second support members.

A preferred polymeric layer may comprise fiberglass fabric impregnated with polyimide resin.

The step of forming first and second members of the metallic inner layer can additionally comprise the step of forming the first and second members of the metallic inner layer from one of the following materials: corrosion resistant steel, titanium.

The step of forming the brittle first and second support members can further comprise the step of forming the brittle first and second support members from a mortar material.

The step of permanently joining the first and second members of the metallic inner layer may comprise the step of welding the first and second members of the metallic inner layer together.

The step of forming a polymeric outer layer on the outer surfaces of the first and second portions of the first metallic inner layer can further comprise the step of forming the polymeric outer layer of polyimide, preferably glass fiber fabric impregnated with polyimide resin.

The curing step of the polymeric outer layer can comprise the step of placing the inner and outer layers mounted in an oven, heating it until the outer polymeric layer has been cured.

Brief Description of Drawings

Figure 1 is a perspective view of an oil-air cooler for a gas turbine engine, showing possible intake and discharge duct structures.

Figure 2 is a schematic flowchart that illustrates the steps in the process of forming the metallic “halves” or “skins” of the duct, according to a preferred embodiment of the invention.

Figure 3 is a schematic flowchart illustrating the process of assembling the metallic "halves" or "skins" of the duct according to a preferred embodiment of the invention, and the subsequent formation of the polymeric outer layer over it.

Detailed Description of the Invention

Although this invention is susceptible of modalities in many different forms, it is represented in the drawings and details here, a specific modality, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to the illustrated modality.

The present invention, in part, comprises a new laminated duct structure, suitable for use in a gas turbine engine, such as turbine engines for use in aircraft. A further aspect of the present invention comprises a method for producing the laminated duct structure.

An air-oil cooler 10, for a gas turbine engine, is shown in Figure 1. The cooler 10 includes heat exchanger 12, together with the intake duct Meo and discharge duct 16, which leads to one side and the other respectively. other, the air flow in the engine, in front of the combustion region (s) of the engine. The configurations of the heat exchanger 12, and the intake and discharge ducts 14 and 16, respectively, are shown simply as an example, and, being functions of the engine architecture as a whole, will vary according to the engine. Thus, the specific shape and configuration of the intake duct 14, and discharge duct are not part of the invention presented here, except as described and claimed here.

Referring to Figure 2, according to a preferred embodiment of the invention, a duct is formed by first creating a three-dimensional (“3D”) image 20 of the duct, using computer aided design techniques (“CAD”). The 3D image is used to, in turn, determine the inner molding line or inner surface contour (“IML”) and outer molding line or outer surface contour (“OML”) (collectively, numeral reference 30) of upper and lower portions (alternatively known as “skins” or “halves”, although not literally so) of the duct, which is then used to create the stamping die molds (for example, mold 40) for each of the upper and lower portions of the duct. Although in the schematic illustrations of Figures 2 and 3, the portions of the inner metallic layer of the duct are shown to be highly regular and symmetrical, in practice, the components of the metallic duct may be highly asymmetric (as generally reflected in Figure 1). Typically, for each metal portion of the duct structure, usually only two parts will be required to be formed separately and then joined.

As mentioned here, the metallic inner layer of the duct is preferably quite thin, for example, preferably on the order of 0.15 mm (0.006 ”) thick, such that the gap between the outer surface of the die 50 and the inner surface of the molds they will be of a similar dimension, although that dimension is representative, and the invention is not to be considered as being limited to it.

The molds 40 are used not only for stamping the actual metal portions of the duct, but also as molds for the support blocks 60, the use of which will be described in detail later. Preferably, support blocks 60 are made of any suitable brittle material, such as mortar material.

As mentioned above, the metal portion of the duct will be quite thin (for example, preferably on the order of 0.15 mm (0.006 ”) thick, and preferably formed from corrosion resistant steel (Cres) or titanium (Ti), although other metals that have similar performance characteristics for the application can also be used. After the two metallic portions (or “skins”), for example, skins 70, have been individually stamped, they are joined together with two welds positioned in the opposite, usually extending longitudinally 80 (for example, “pencil” welds), after the two corresponding support blocks 60 have been placed inside the respective metallic skins.

The support blocks 60 serve to provide support and rigidity to the metal duct, during the process steps described below. A layer 90 of polymeric material, preferably fiberglass fabric impregnated with polyimide resin or in a single thickness measure or multiple thickness measures, where each thickness measure is approximately 0.25 mm (0.010 ”) thick is applied to the outside of the metal duct and heat-cured, in an appropriate atmosphere, at a sufficient temperature and for a sufficient time, suitable for the material, to ensure that the polyamide is firmly attached to the outer surfaces of the metal skins.

Preferably, the fiberglass fabric with polyimide resin, in its uncured state, is cut in a desirable outline to fit over the inner metallic layer. Multiple layers or thickness measurements of this fabric can be used to add strength or pressure-bearing capabilities. As part of the curing process, the entire metal / polyimide assembly is wrapped with retractable tape, retractable wrap or vacuum bag to press the metal / polyimide layers together and join them together.

Once the curing process has been completed, the mortar support blocks 60 are broken from the final part 100, and the interior of the metal layer is cleared of debris and material released from the mold (if any).

The description and drawings presented so far are merely illustrative to explain the invention, and are not to be considered as limiting it, and those usually skilled in the art will be able to make modifications and variations on the present invention without departing from the scope of the invention. .