Patent Application
20130202424
This disclosure relates to a fan section for a gas turbine engine, and, in particular, a conformal liner for the fan section.
One type of gas turbine engine includes a core engine having compressor and turbine sections that drive a fan section. The fan section includes circumferentially arranged fan blades disposed within a fan case. The fan section is subject to large temperature fluctuations throughout engine operation. A minimized clearance tight seal is desired between the tips of the fan blades and the fan case throughout engine operation at the various operating temperatures.
One system has been proposed to accommodate thermal expansion and contraction in a fan section having composite fan blades. The composite fan blades are arranged within a composite liner of generally the same material. Several pins at discrete circumferential locations along the liner are used to support the liner relative to a metallic fan case and permit the fan case to expand and contract relative to the composite liner.
A fan section of a gas turbine engine includes a fan case structure having a first coefficient of thermal expansion. A fan blade is arranged within the fan case structure and has a second coefficient thermal expansion. A continuous, ring-shaped liner surrounds the fan blade and includes a third coefficient of thermal expansion that is substantially similar to the second coefficient of thermal expansion and substantially different than the first coefficient of thermal expansion. A desired radial tip clearance is provided between the liner and the fan blade. An elastomeric adhesive operatively connects the liner to the fan case structure. The adhesive is configured to accommodate diametrical change in the liner and maintain the desired radial tip clearance throughout various fan section operating temperatures.
In a further embodiment of any of the above, the adhesive has a 300% elongation or greater.
In a further embodiment of any of the above, the adhesive is silicone rubber.
In a further embodiment of any of the above, the second coefficient of thermal expansion is greater than the first coefficient of thermal expansion by at least 10×10−6/° F. (18×10−6/° C.).
In a further embodiment of any of the above, the fan structure includes a composite fan case.
In a further embodiment of any of the above, the fan case structure includes a honeycomb structure operatively connected radially inward of and to the composite fan case.
In a further embodiment of any of the above, the fan case structure includes a composite septum interconnecting the adhesive and the honeycomb.
In a further embodiment of any of the above, the second and third coefficients of thermal expansion are within 1×10−6/° F. (1.8×10−6/° C.) of one another.
In a further embodiment of any of the above, the fan blade and the liner are constructed from the same series aluminum alloy.
In a further embodiment of any of the above, the desired radial tip clearance is about 0.030 inch at −65° F. (0.76 m at −54° C.) ambient.
In a further embodiment of any of the above, a rub strip is supported on and radially inward of the liner between the liner and the fan blade.
A fan case structure includes a composite fan case structure having a first coefficient of thermal expansion. A continuous, ring-shaped liner has a second coefficient of thermal expansion that is substantially different than the first coefficient of thermal expansion. The second coefficient of thermal expansion is greater than the first coefficient of thermal expansion by at least 10×10−6/° F. (18×10−6/° C.). An elastomeric adhesive operatively connects the liner to the fan case structure. The adhesive has a 300% elongation or greater. The adhesive is configured to accommodate diametrical change in the liner through various operating temperatures.
In a further embodiment of any of the above, the composite fan case structure includes a structure constructed from resin and at least one of carbon fibers and fiberglass. The liner is an aluminum alloy.
In a further embodiment of any of the above, the adhesive is silicone rubber.
In a further embodiment of any of the above, a rub strip is supported radially inward from and by the liner. The composite fan case structure includes a composite septum interconnecting the adhesive to a honeycomb structure that is supported by and radially inward from a composite fan case.
The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
An example gas turbine engine 10 is schematically illustrated in
A fan section 18 is arranged within a fan case structure 30, which provides a bypass flow path 28 between the fan case structure 30 and the core housing 24. In the example illustrated, the first shaft 20 rotationally drives circumferentially arranged fan blades 26 that provide flow through the bypass flow path 28. In one example, the fan blades 26 are constructed from an aluminum alloy. It should be understood that the configuration illustrated in
Referring to
In one example, the fan case structure 30 includes a composite fan case 32, which is constructed from carbon fiber and resin in one example. In one example, the septum 42 is a composite structure constructed from fiberglass and resin. As can be appreciated, composite structures have relatively low coefficients of thermal expansion and are dimensionally stable throughout the various operating temperatures.
A continuous, ring-shaped liner 44, which is an aluminum alloy, for example, is supported by the fan case structure 30, and in the example shown, by the septum 42, using an elastomeric adhesive 46. In one example, the adhesive 44 has a room temperature radial thickness 48 of 0.100 in. (2.54 mm) and greater than 300% elongation, which may be provided by a silicone rubber.
The liner 44 has a coefficient of thermal expansion that is substantially the same as the coefficient of thermal expansion of the fan blades 26 and substantially different than the fan case structure 30. In one example, the fan blades 26 and liner 44 have coefficients of thermal expansion that are within 1×10−6/° F. (1.8×10−6/° C.) of one another and are constructed from the same series aluminum alloy, which may be AM54027 in one example. In one example, the liner/fan blade coefficient of thermal expansion is greater than the fan case structure thermal expansion by at least 10×10−6/° F. (18×10−6/° C.)
The liner 44 includes a rub strip 36 that provides an abradable material immediately adjacent to tips 34 of the fan blades 26, providing a blade tip clearance 38. It is desirable to maintain a desired radial blade tip clearance throughout various fan section operating temperatures. In one example, a desired radial tip clearance is about 0.030 in. at −65° F. (0.76 mm at −54° C.) ambient, which is typically encountered during cruise altitude. Thus, the elastomeric adhesive 44 is selected to accommodate changes in a diameter 50 (only radial lead line is shown in
Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.
