Gas turbine engine blade containment system and a laminate material

A gas turbine engine blade containment system that includes a laminate material including first and second layers. The first layer is an inner layer within the second layer. The second layer includes a plurality of resiliently compressive springs extending transversely relative to the first layer, and each spring is encased in a crushable support material. The first layer includes a hard material to blunt a broken blade. The springs in the second layer are compressed and the crushable support material of the second layer is crushed to absorb energy of a broken blade.

This invention relates to laminate materials, particularly, but not exclusively, the invention relates to laminate materials for use in containment systems of layered containment systems. Specifically, but not exclusively, the invention relates to laminate materials for use in gas turbine engine blade containment systems.

The casings of gas turbine engines are manufactured to absorb energy from any blades or other components which break off from the spinning discs within the engine. One example of casing is one formed from solid ductile material. However, such casings have a disadvantage of being heavy and requiring a large thickness.

According to one aspect of this invention, there is provided a gas turbine engine blade containment system including a laminate material, the laminate material comprising first and second layers, wherein the second layer being arranged on the first layer, the second layer comprises a plurality of deformable members extending transversely relative to the first layer, each deformable member being encased in a crushable support material, the deformable members comprise springs, the first layer being an inner layer within the second layer.

In one embodiment, the crushable support material may comprise a matrix encasing the plurality of deformable members. The matrix may extend across substantially the whole of the second layer. In another embodiment, each deformable member may be encased in a discrete encasing member. The support material may be a polymeric material, a low density metal, or a metal foam.

The crushable support material may comprise a plurality of hollow elements embedded in a polymeric material. The hollow elements may comprise spheres of a breakable material, such as glass or rigid plastics material. Preferably, the hollow elements are filled with a gas such as air or argon. Alternatively, the crushable support material may comprise a foamed polymeric material. The foamed polymeric material may comprise a polymeric material having a plurality of cells. The cells may be open or closed. The polymeric material may comprise a resin material.

The springs may be coil springs and/or two-dimensional springs. The coil springs may comprise a helix, conveniently a single helix, or a multiple helix, or may be of rectangular form. Where the deformable members comprise coil springs, and the support material includes hollow elements, the hollow elements may be arranged within the coils of the springs.

The laminate material may comprise a third layer arranged over the second layer, such that the second layer is provided between the first layer and the third layer.

According to another aspect of this invention, there is provided a laminate material as described above.

According to a further aspect of this invention, there is provided a gas turbine engine incorporating a casing as described above.

Referring toFIG. 1, a gas turbine engine is generally indicated at10and comprises, in axial flow series, an air intake11, a propulsive fan12, an intermediate pressure compressor13, a high pressure compressor14, a combustor15, a turbine arrangement comprising a high pressure turbine16, and intermediate pressure turbine17and a low pressure turbine18, and an exhaust nozzle19.

The gas turbine engine10for an aircraft operates in a conventional manner so that air entering the intake11is accelerated by the fan12which produce two air flows: a first air flow into the intermediate pressure compressor13and a second air flow which provides propulsive thrust. The intermediate pressure compressor13compresses the air flow directed into it before delivering that air to the high pressure compressor14where further compression takes place.

The compressed air exhausted from the high pressure compressor14is directed into the combustor15where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive, the high, intermediate and low pressure turbines16,17and18before being exhausted through the nozzle19to provide additional propulsive thrust. The high, intermediate and low pressure turbines16,17and18respectively drive the high and intermediate pressure compressors14and13and the fan12by suitable interconnecting shafts. The fan12, the compressors13,14and the turbines,16,17,18are surrounded by casings designated generally by the numeral20.

It is a certification requirement of gas turbine engines that, should components such as fan blades, compressor blades, turbine blades or pieces thereof break away from the disc securing them to the shafts, these pieces must be contained. Should this happen the high energy of the blade or blade piece would cause it to strike the inside of the casing20of the gas turbine engine10. It is necessary to ensure that the energy of the blades is absorbed by the casing20and hence in one embodiment described below with reference toFIG. 2, the casing20comprises a containment system22(shown in more detail inFIG. 2) formed of a three layer laminate material24.

In the embodiment shown inFIG. 2, a first layer26, which is an inner layer, is formed of a hard material intended to blunt the approach of the broken blade to spread the load thereon.

The laminate material24also comprises a second layer28, arranged on the first layer26. The second layer28comprises a plurality of deformable members30in the form of coil springs32. The springs32are embedded in a matrix33of a support material34. The support material34can be polymeric foam material, a metal foam material, or a polymeric material incorporating hollow elements38such as beads or spheres containing air or other gas such as argon (seeFIG. 4).

The laminate material24comprises a third layer36, which is an outer layer, arranged on the second layer28and which is formed of a rigid material to maintain structural integrity and function. A suitable material could be steel or titanium. The outer layer36constitutes the outer casing member and is provided with flanges, or other suitable means, shown schematically at21to secure the containment system22to adjacent containment systems22to provide the casing20, or to secure the containment system22to other casings.

The casing20is generally cylindrical, or frustoconical, and is arranged substantially coaxially around the fan12, the compressors13,14or the turbines16,17and18.

The first and second layers26and28are therefore arranged substantially coaxially within the third layer36, or casing20.

It is to be noted that the coil springs32in the second layer28are arranged such that the axes of the coil springs32are arranged substantially perpendicularly to the first layer26and substantially perpendicularly to the third layer36, or casing20. The axes of the coil springs32are therefore arranged substantially radially relative to the axis of the casing20and hence the axis of rotation of the fan12, compressors13,14and turbines16,17and18. The coil springs32therefore extend in a direction transverse to the first layer26and the third layer36, or casing20.

As the broken blade, generally referred to as an impactor, strikes the first layer26, the impactor is blunted. Subsequently, the impactor rotates and there is then a further impact event when the blade root strikes the casing. Typically, this further impact can cause more damage than the initial impact. The impactor passes into the second layer28. As the impactor enters the second layer28, the springs32are deformed by being compressed by the force supplied thereto by the impactor and, at the same time, the support material34is crushed thereby also absorbing the energy of impact.

In the event that the energy of impact is sufficiently large, after passing through the second layer28, the impactor strikes the third layer36, where the impactor halts and is thus prevented from passing out of the containment system22. This is the ultimate load for which the containment system22is designed.

Referring toFIGS. 3 to 6, there are shown examples of several embodiments of one of the springs32embedded in the support material34. In the embodiment shown inFIG. 3, the support material34is formed of a foamed polymeric material, a metal foam or a low density metal.

As the impactor strikes the second layer28, the spring32is compressed and the support material34is crushed.

FIG. 4shows an embodiment in which the support material34incorporates a plurality of hollow spherical elements38formed of glass or rigid plastics material, and filled with a suitable gas, such as argon. The hollow elements38can be distributed randomly about the support material34, or can be arranged, as shown inFIG. 4, within the helical coils of the spring32. The provision of the hollow elements38allows the support material34to be crushed when it is struck by the impactor.

Referring toFIG. 5, there is shown an embodiment which is similar to the embodiment shown inFIG. 3, in which the spring32is of a rectangular configuration. Although not shown inFIG. 5, the support material34could incorporate hollow members similar to those shown inFIG. 4.

Referring toFIG. 6, there is shown an embodiment, in which the spring32is of a conical configuration. With this embodiment, the narrow end of the spring32is arranged adjacent to the inner layer26, and the wider end of the spring32is arranged adjacent to the outer layer36.

When the spring32shown inFIG. 6is initially struck by an impactor only the narrow end deforms at first. The stiffness of the conical spring32shown inFIG. 6increases as the wider end of the spring32deforms. This has the advantage of allowing the impact load to be transmitted gradually.

FIG. 7shows an exploded view of a further embodiment of a containment system22, which is suitable for noise absorption. The embodiment shown inFIG. 7comprises a first or inner layer26, a second or middle layer28, and a third or outer layer36. In the event that the containment system is required to absorb noise, the first layer26may be perforated. The third layer36can be formed of the same material as described above. The second layer28is formed of a plurality of discrete tubes40of the support material33. Each tube40has embedded therein a single spring32(seeFIG. 8). The tubes40are arranged in an hexagonal packed array.

Reference is made toFIG. 8which shows a single cylindrical tube40ofFIG. 7. The tube40is formed of a cylindrical annular wall42having a spring embedded in the wall42. The tube40has a hollow centre around which the wall42and the coils of the spring32extend.

The first layer26is formed of a material37defining perforations37A to enable the first layer26to absorb noise. The material37may be in the form of a sheet material to absorb noise.

The containment system38operates in the same way as described above. When an impactor strikes the first layer26, it passes into the first layer26to strike the tubes40of the second layer28. The springs32in the tubes40deform as the tubes40are crushed, thereby absorbing the force from the impactor. When the impactor passes through the second layer28, it strikes the third layer36where the impactor halts.

In all the above embodiments, the springs32can be formed of metal and manufactured in the standard way of making springs as would be known in the art.

The springs32could alternatively be formed of carbon fibre, in which case the springs32could be manufactured by wrapping the carbon fibre around a mandrel and then impregnating with a resin and then curing to set the carbon fibre spring in that shape.

The springs could vary in size from of the order of 10−2m to of the order of 10−9m in length. In the case of springs32having a length which is of the order of 10−9m, the springs32could be manufactured by nanotechnology methods as would be known by persons skilled in that art.

Various modifications can be made without departing from the scope of the invention. Referring toFIG. 9, there is shown a further embodiment of a containment system22. In this embodiment, the containment system22comprises only two layers namely the first or inner layer26and the second or outer layer28.

In this embodiment, shown inFIG. 9, the first layer26is generally the same as the first layer of the embodiment shown inFIG. 2. However, the second layer28of the embodiment shown inFIG. 9is generally thicker than the second layer28of the embodiment shown inFIG. 2, and has a sufficient thickness and stiffness to contain a detached fan blade, or portion of a detached fan blade.

The second layer28of the embodiment shown inFIG. 9comprises a plurality of the conical springs32shown inFIG. 6. The springs32are arranged such that they increase in stiffness in a radially outwards direction. To achieve this the conical springs32are arranged such that the narrow end is closest to the first layer26and the wider end is further from the first layer26.

Alternatively, or in addition, stiffness of the second layer28can be provided by varying the density of the second layer28so that the density increases in a radially outwards direction. This can be achieved by increasing the proportion of hollow elements38adjacent to the first layer26and decreasing their proportion in the radially outwards direction such that, the second layer28becomes substantially free of the hollow elements adjacent to the radially outer face of the second layer28.

The provision of an increased amount of the hollow elements38adjacent to the first layer26would provide a honeycomb configuration, and would have advantages associated with noise reduction.

The reduction in the proportion of hollow elements in the outward direction could be a gradual reduction or a stepwise reduction.

In the embodiment shown inFIG. 9, the containment system22is arranged in the gas turbine engine10such that the first layer26is closest to the axis of the gas turbine engine10. The second layer28constitutes a casing member and is provided with flanges21or other suitable means to enable the containment system22to be attached to adjacent containment systems22to form the casing20, or to be attached to other casings.

The casing20is generally cylindrical, or frustonconical, and is also arranged substantially coaxially around the fan12, compressors13,14or the turbines16,17and18. The first layer26is therefore arranged substantially coaxially within the second layer28, casing20. Again the coil springs32in the second layer28are arranged such that the axes of the coil springs32are arranged substantially perpendicularly to the first layer26and thus the axes of the coils springs32are arranged substantially radially relative to the axis of the casing20and hence the axis of rotation of the fan12, compressors13,14and turbines16,17and18.

Although the present invention has been described with reference to the use of coil springs other suitable springs may be used in the second layer providing the springs are resiliently compressible in the direction transverse to the first layer.