Composite heat shield

A composite heat shield includes a ceramic composite heat shield body comprising a pair of generally spaced-apart heat shield side panels, a heat shield bottom panel extending between the heat shield side panels and having a heat exposure surface, a heat shield top panel extending between the heat shield side panels in spaced-apart relationship with respect to the heat shield bottom panel and having at least one heat shield surface and at least one heat shield cavity defined between the heat shield bottom panel and the heat shield top panel.

TECHNICAL FIELD OF THE INVENTION

The disclosure relates generally to heat shields. More particularly, the disclosure relates to a composite heat shield and thermal barrier which is suitable for aircraft.

BACKGROUND OF THE INVENTION

Existing aircraft heat shields may be made from titanium, which has an upper temperature limit of about 1100 degrees F. Multiple segments may be built into the titanium heat shield to facilitate thermal expansion and contraction. Aircraft engines may be designed to operate more efficiently by running at idle exhaust temperatures which are higher than the heat capacity of titanium. Therefore, in order to maintain the idle exhaust temperature at a temperature level which is lower than the heat capacity of titanium, the engine may require operation at a higher thrust with a resulting higher fuel consumption level. This may result in an increased level of brake wear. An alternative to the use of titanium would be to use a stainless steel nickel alloy that is capable of handling the higher exhaust temperatures. This may result in an increased weight with a resulting higher fuel consumption level throughout the aircrafts life.

A conventional aft fairing pylon heat shield may be designed with a titanium exhaust plume suppressor with an internal thermal blanket to protect the systems, the diagonal brace and the surrounding aircraft structures from the engine exhaust. The design may require considerable tooling and detailed manufacturing processes to form and assemble the heat shield and the thermal blanket.

Therefore, a heat shield is needed which is simple in construction, is effective in protecting aircraft structures from aircraft engine exhaust and may reduce or eliminate the need for additional heat barriers.

SUMMARY OF THE INVENTION

The present disclosure is generally directed to a composite heat shield. An illustrative embodiment of the heat shield includes a ceramic composite heat shield body comprising a pair of generally spaced-apart heat shield side panels, a heat shield bottom panel extending between the heat shield side panels and having a heat exposure surface, a heat shield top panel extending between the heat shield side panels in spaced-apart relationship with respect to the heat shield bottom panel and having at least one heat shield surface and at least one heat shield cavity defined between the heat shield bottom panel and the heat shield top panel.

DETAILED DESCRIPTION

The disclosure is generally directed to a composite matrix ceramic (CMC) heat shield lower surface which may have a heat capacity higher than that of titanium. The ceramic heat shield may provide a one-piece (no segmented gaps) construction which may undergo minimal thermal expansion during aircraft engine thermal cycling and may have a high temperature capacity to thermally isolate structure and systems above the heat shield from engine exhaust on an aircraft. Consequently, an aircraft engine on which the heat shield is assembled may be operated at a lower idle thrust and higher temperature, resulting in decreased fuel consumption and brake wear.

Referring initially to FIGS.1and5-7, an illustrative embodiment of the heat shield is generally indicated by reference numeral2. The heat shield2may include a heat shield panel3which may include a wide panel end5and a narrow panel end6and have a generally elongated, conical shape when viewed from above or below. The heat shield panel3may have a generally concave lower surface3aand a generally convex upper surface3b. Multiple stiffening ribs4may be shaped in the heat shield panel3in generally spaced-apart, parallel relationship with respect to each other for structural reinforcing purposes.

As shown inFIGS. 5 and 6, thickened panel edge portions9may be provided in the opposite longitudinal edges of the heat shield panel3. A panel side flange10may extend outwardly from each panel edge portion9. A side skin attachment flange11may extend from each panel edge portion9at a generally acute angle with respect to the heat shield panel3. Therefore, each panel edge portion9may define the junction between the heat shield panel3; each side flange10; and the corresponding side skin attachment flange11. As shown inFIG. 1, the panel edge portions9and side skin attachment flanges11may converge and meet at the narrow panel end6of the heat shield panel3.

The heat shield panel3and each panel edge portion9, side flange10and side skin attachment flange11may be a ceramic composite material having a high temperature capacity such as composite matrix ceramic (CMC), for example and without limitation. As shown inFIG. 6, the heat shield panel3and each side flange10and each side skin attachment flange11may include multiple laminated CMC plies7. A radius filler or “noodle”12may fill the interface between the plies7at the joint between the heat shield panel3, each side flange10and the corresponding side skin attachment flange11in each panel edge portion9, as is known to those skilled in the art. As shown inFIG. 7, in some embodiments an insulation coating14may be provided on the heat shield panel3and may additionally be provided on the panel side portions9, shown inFIG. 6, side flanges10and side skin attachment flanges11of the heat shield2.

Referring next toFIGS. 2-4of the drawings, the heat shield2may be a part of a heat shield assembly1. In the heat shield assembly1, a side skin16may be attached to each side skin attachment flange11of the heat shield2. Each side skin16may be diffusion-bonded SPF (superplastic forming) titanium, for example and without limitation and may be a continuous piece having no split line. Each side skin16may be attached to the corresponding side skin attachment flange11according to any suitable technique which is known to those skilled in the art. As shown inFIG. 3, in some embodiments multiple side skin fasteners17may extend through respective registering pairs of fastener openings (not shown) provided in the side skin attachment flange11and the side skin16, respectively. Securing nuts18may be provided on the respective side skin fasteners17and threaded against the interior surface of the side skin16.

As further shown inFIGS. 2-4, in some embodiments a nut plate22is attached to each stiffening rib4in the heat shield panel3and to the side skin16. Each nut plate22may be titanium, for example and without limitation and may include a generally rectangular nut plate panel23. A reinforcing lip24may extend from one or multiple edges of the nut plate panel23. A rib notch25may be provided in the reinforcing lip24to receive and engage the stiffening rib4in a snap-fit.

In typical application of the heat shield2, the heat shield panel3of the heat shield assembly1is attached to an aft pylon fairing (not shown) and wing structure (not shown) on a jet passenger aircraft according to the knowledge of those skilled in the art. In operation of the aircraft, exhaust gases (not shown) from the jet engine contact the generally concave lower surface3aof the heat shield panel3, which thermally insulates structures and systems (not shown) above the heat shield assembly1from the heat. Because the heat shield panel3may be capable of withstanding temperatures which are higher than the temperature capacity of titanium, the jet engine may be operated at a lower idle thrust and higher temperature, resulting in decreased fuel consumption and aircraft brake wear. Furthermore, because it may undergo minimal thermal expansion and contraction during thermal cycling of the jet engine, the heat shield2may be constructed in one piece as was noted hereinabove. Consequently, the jet engine can be designed with thermal cycles which are not limited by material restrictions.

Referring next toFIGS. 8 and 9, embodiments of the disclosure may be used in the context of an aircraft manufacturing and service method78as shown inFIG. 8and an aircraft94as shown inFIG. 9. During pre-production, exemplary method78may include specification and design80of the aircraft94and material procurement82. During production, component and subassembly manufacturing84and system integration86of the aircraft94takes place. Thereafter, the aircraft94may go through certification and delivery88in order to be placed in service90. While in service by a customer, the aircraft94may be scheduled for routine maintenance and service92(which may also include modification, reconfiguration, refurbishment, and so on).

As shown inFIG. 9, the aircraft94produced by exemplary method78may include an airframe98with a plurality of systems96and an interior100. Examples of high-level systems96include one or more of a propulsion system102, an electrical system104, a hydraulic system106, and an environmental system108. Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry.

The apparatus embodied herein may be employed during any one or more of the stages of the production and service method78. For example, components or subassemblies corresponding to production process84may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft94is in service. Also, one or more apparatus embodiments may be utilized during the production stages84and86, for example, by substantially expediting assembly of or reducing the cost of an aircraft94. Similarly, one or more apparatus embodiments may be utilized while the aircraft94is in service, for example and without limitation, to maintenance and service92.

Referring next toFIGS. 10-13, an alternative illustrative embodiment of the heat shield is generally indicated by reference numeral31. The heat shield31may include a generally elongated, conical-shaped heat shield body32which may include a main body portion32aand a tapered body portion32bwhich extends from the main body portion32a. The main body portion32aand the tapered body portion32bof the heat shield body32may have a monolithic composite construction, for example and without limitation. As shown inFIG. 13, a core cavity38may be provided in the tapered body portion32b. A core39, which may be a foam material, for example and without limitation, may be provided in the core cavity38.

The heat shield body32of the heat shield31may include a pair of spaced-apart heat shield side panels33. A heat shield bottom panel34, which may have a generally curved configuration, may extend between the heat shield side panels33. The heat shield bottom panel34may be attached to the heat shield side panels33at respective panel junctions35. Side flanges36may extend outwardly from the respective panel junctions35. The heat shield bottom panel34may have a generally concave heat exposure surface34aand a generally convex interior surface34b.

A heat shield top panel40may extend between the heat shield side panels33in spaced-apart relationship with respect to the heat shield bottom panel34. The heat shield top panel40may include a pair of top panel sections41which are joined longitudinally to each other along a top panel center line42. The top panel sections41of the heat shield top panel40may have a pair of respective heat shield surfaces41adisposed at a generally obtuse angle or sloped position with respect to each other and a pair of interior surfaces41bwhich are opposite the respective heat shield surfaces41a. Upper flanges37may extend from the respective heat shield side panels33, beyond the plane of the heat shield surfaces41aof the respective top panel sections41.

A heat shield partition46may extend between the heat shield side panels33of the heat shield body32and may be generally disposed between the heat shield bottom panel34and the heat shield top panel40. A lower heat shield cavity49may be defined between the heat shield partition46and the heat shield top panel40. An upper heat shield cavity50may be defined between the heat shield partition46and the heat shield bottom panel34. The lower heat shield cavity49and the upper heat shield cavity50may thermally insulate the heat shield surfaces41aon the respective top panel sections41of the heat shield top panel40from the heat exposure surface34aon the heat shield bottom panel34.

As shown inFIG. 13, a drain inlet opening55may be provided in the heat shield top panel40at the tapered body portion32bof the heat shield body32. A drain outlet opening56may be provided in the heat shield bottom panel34at the tapered body portion32b. A drain conduit54may extend through the tapered body portion32band establish communication between the drain inlet opening55and the drain outlet opening56.

In typical application of the heat shield31, the heat shield body32may be attached to an aft pylon fairing (not shown) and wing structure (not shown) on a jet passenger aircraft according to the knowledge of those skilled in the art. In operation of the aircraft, exhaust gases (not shown) from the jet engine contact the generally concave heat exposure surface34aof the heat shield bottom panel34, which thermally insulates structures and systems (not shown) above the heat shield31from the heat. The lower heat shield cavity49and the upper heat shield cavity50may further thermally insulate the structures and systems from the heat. Because the heat shield31may be capable of withstanding temperatures which are higher than the temperature capacity of titanium, the jet engine may be operated at a lower idle thrust and higher temperature, resulting in decreased fuel consumption and aircraft brake wear. Furthermore, because it may undergo minimal thermal expansion and contraction during thermal cycling of the jet engine, the heat shield31may be constructed in one piece as was noted hereinabove. Consequently, the jet engine can be designed with thermal cycles which are not limited by material restrictions. Liquid (not shown) which collects on the heat shield top panel40may be drained from the heat shield surfaces41aof the respective top panel sections41through the drain conduit54(FIG. 13).

Referring next toFIG. 14, an alternative illustrative embodiment of the heat shield is generally indicated by reference numeral31a. The heat shield31ahas a more attenuated or less curved heat exposure surface34aas compared to the heat exposure surface34aof the heat shield31which was heretofore described with respect toFIGS. 10-13. This results in a lower volume of the lower heat shield cavity49as compared to that of the heat shield31. Therefore, the curvature of the heat exposure surface34aand volume of the lower heat shield cavity49may be selected depending on the thermal insulation requirements as dictated by airplane exhaust and engine fan flow characteristics.

It will be appreciated by those skilled in the art that the simplicity of construction of the heat shield31may reduce the part count of the heat shield31from ˜30 to a single piece. Furthermore, the heat shield31may not require a thermal blanket. The reduction in part count may result in a direct translation to cycle time reduction. Moreover, because the thermal blanket is eliminated, internal support structures for the thermal blanket, such as internal support gussets and stringers and other mounting hardware may be eliminated. The simple one-piece construction of the heat shield31may result in a weight reduction of 24 lbs. per airplane. The heat shield part count reduction and elimination of the thermal blanket may result in a reduction of total cost expenditure. As a secondary effect, there may be a significant cost reduction related to recurring and non-recurring dollars due to part count and part card reduction; engineering design, development and testing; and manufacturing direct charging. Elimination of the thermal blanket may result in elimination of the need to perform sonic, thermal and fatigue testing which may otherwise be required for the thermal blanket.