Dirt removal means for air cooled blades.

0001This invention relates to cooled blades of a rotor of a gas turbine engine and particularly for controlling foreign matter contained in the cooling air so as to pre­vent clogging of the cooling air holes or passages in the blade.

0002It is well known that engine parts, particularly the blades of the turbine of aircraft gas turbine engines are cooled by use of engine cooling air. For example, cooling of the turbine blades is attained by routing cooling air from the engine's compressor through a TOBI (turbine on­board injector) which is then fed through internal passa­ges formed within the blade. The air is ultimately dis­charged through openings in the turbine blades and may be returned to the engine's gas path.

0003Equally well known is the fact that foreign matter, either acquired through the ambient environment or self-­generated within the engine, ingests into the cooling airstream and has the propensity of clogging these cooling passages and openings referred to in the above. Obviously, aircraft that is operating in areas where dust is at high levels, such as in the sandy areas of certain geographic locations of the world, the problem becomes exasperated.

0004Many attempts have been made to alleviate these pro­blems and examples of such attempts are disclosed, for example, in U.S. Patents 3,356,340 granted to M. Bobo on Dec. 5, 1967, U.S. Patent 4,309,147 granted to W.E. Koster et al on Jan. 5, 1982, U.S. Patent 2,632,626 granted to F.A. McClintock on Mar. 24, 1953 and U.S. Patent 3,918,835 granted to G.J. Yamarik on Nov. 11, 1975, the latter two patents being assigned to United Technologies Corporation, the assignee of this patent application.

0005In each of these instances the cooling air passes through a tortuous route before reaching the turbine coo­ling passages so that the foreign particles in the coo­ling airstream are diverted from the turning cooling air­stream or the cooled air entrained dirt is admitted to a centrifugal field where the heavier foreign particles are centrifuged to a surface and retained there until the engine 40 is disassembled and cleaned. The 3,918,835 patent discloses a centrifugal type of dirt separator and provides an in­clined surface that directs the collected dirt particles toward the labyrinth seal where it migrates thereto and is carried through the seal by the leakage air.

0006In other types of dirt separators or removal schemes, mechanisms upstream of the turbine are provided so as to prevent the dirt from reaching the turbine blades. Histo­rically, such schemes would include a ramp mounted ahead of the TOBI. The ramp serves to deflect and prevents the dirt from making the sharp turn that is required for the cooling air to get into the TOBI. This has met with some success where the dirt particles are sufficiently large so that the inertia of the particle overcomes the velocity of the cooling airstream causing the particle to continue its travel while the air makes a turn. However, smaller sized particles would be influenced by the cooling stream velocity and would turn with the air and hence be carried into the blade cooling passages and holes. This resulted in dirt buildup in passages and clogging of holes which adversely affected the cooling ability of the cooling system. Obviously, this blockage can result in distress or failure of the airfoil or reduce the pressure of the cooling air supplied to the vane upstream of the turbine. To overcome the pressure loss it would be necessary to increase coolant outflow which, in turn, would increase the burner pressure drop and thereby adversely affect engine performance.

0007The object of the invention is to obviate the pro­blems enumerated in the above by designing the blade itself to carry its own dirt removal system, hence providing a method to make the cooled turbine blades tolerant to dirt or dust contaminating the cooling air.

0008A feature of one embodiment of the invention is to cast the aircraft turbine engine multipassage blade with internal baffles such that the baffles guide the entrained dirt into a preselected passage internally of the blade where the velocity of the cooling air in that passage car­ries the entrained dirt to a dirt removal hole formed in the tip of the blade.

0009In an other embodiment a stamped out sheet metal deflector or baffle is attached to the root of the blade so as to direct the dirt entrained air either into a high velocity passage in the blade itself or a high velocity passage in the turbine disk or in proximity thereto.

0010The baffle can be stamped out from a sheet metal stock and can be sized to attach the deflector as a "fix" to the underside of existing blades.

0011The turbine blade of the invention eliminates the need of the upstream air cleansing schemes that have been heretofore prevalent in the gas turbine engine technology.

0012The foregoing and other features and advantages of the present invention will become more apparent from the following description and accompanying drawings. <ul id="ul0001" list-style="none"><li>Fig. 1 is a view partly in section and schematic illustrating a prior art air cooled turbine blade design.</li><li>Fig. 2 is a view similar to Fig. 1 of an air cooled turbine blade according to one embodiment of the present invention.</li><li>Fig. 3 is a partial view of a turbine rotor in section and partly in schematic incorporating a turbine blade according to another embodiment of the present in­vention.</li><li>Fig. 4 is a partial view taken along the lines 4-4 of Fig. 3.</li><li>Fig. 5 is a bottom view of the blade of Fig. 3 showing the deflectors fabricated from sheet metal stock.</li><li>Fig. 6 is a partial view similar to Fig. 3 showing modification of the embodiment of Fig. 3.</li><li>Fig. 7 is a view in elevation of the stamped out sheet metal stock forming the deflector of Fig. 6.</li></ul>

0013For a detailed description of a cooled turbine blade for an aircraft gas turbine engine, reference should be made to U.S. Patent 4,479,532, granted to M.J. Pazder on Oct. 2, 1984, and assigned to the same assignee as this patent application.

0014For the sake of simplicity and convenience the de­tail of the blades is omitted from the drawings and only the essential portions necessary for an understanding of the invention will be detailed. As will be understood, the internal construction of the blade may utilize any of the heat transfer enhancement schemes that are known in this technology. Hence, it is contemplated that the airfoil would incorporate the requisite trip strips, pe­destals, vanes and the like to achieve the desired cooling.

0015The prior art design is illustrated in Fig. 1 showing the interior of the airfoil section taking a section through the longitudinal or spanwise axis. The airfoil section 10 of the blade is partitioned by a plurality of ribs into a plurality of subpassages. As noted, the blade comprises the leading edge 12, trailing edge 14, tip 16 and root end 18. Ribs 20,22 and 24 define four passages 26, 28, 30 and 32 extending in the spanwise direction, rib 20 is bifurcated defining additional subpassages for defining serpentine passages with rib 30. As is well known each of the passa­ges and the impingement sections are designed to accomplish well defined objectives, which are not dealt with in this patent application. The design of these high technology cooled turbine blades require a significant number of holes which also have well defined objectives.

0016It is apparent from the foregoing that the cooling air admitted into these passages is entrained with foreign matter, and this foreign matter more likely than not will adhere to the walls of the passages and/or clog the holes.

0017According to this invention and referring particular­ly to Fig. 2, which incorporates the high technology heat transfer enhancement techniques (not shown), the ribs are modified in such a manner as to form deflectors for the dirt entrained cooling air so that all or a significant amount of the dirt entrained air is directed to the trai­ling edge passage 36; the passages being rearranged to provide for the dirt removal.

0018As noted in Fig. 2, similar components have like reference numerals and where the component is modified a subscript "a" has been added. The angled rib portions 40, 42 and 44 are disposed at the root portion of the blade in proximity to the inlet of passages 26a, 28a and 30a and as noted are inclined from the root to the tip and extend in the chord direction and are cast into the blade. These rib portions 40, 42 and 44 serve to deflect the cooling air entrained with dirt in a direction toward the trailing edge passage 36. Passage 36 is specifically designed as a straight through passage and is directly communicating with the inlet air admitted into the root in passage 46. A dirt removal hole 48 is formed at the tip end of passage 36 to discharge the dirt entrained air into the engine's gas path. The purpose of designing passage 36 with as little, if any, turns is to assure that the velo­city of the cooling airstream is sufficient to flow the dirt directly out through the dirt removal hole 48.

0019The other passages 26a, 28a and 30a are thus sub­stantially free of dirt. In addition to providing for a dirt removal system directly in the blade, by selectively directing the dirt through the passage with the high velo­city cooling airstream, it is now possible to eliminate the many purge holes that heretofore have been designed with these blades. This obviates the problem of utilizing a large amount of air that is not being utilized solely for cooling and as experience has shown, the air velocity in some of these passages associated with the purge air holes is relatively low which impedes or limits the remo­val of dirt.

0020The airfoil section 10 of the blade of Fig. 3 is partitioned by a plurality of ribs 20, 22, 24 into a plurality of subpassages. As noted, the blade comprises the leading edge 12, trailing edge 14, tip 16 and root end 18. Ribs 20, 22 and 24 define multi passages including passage 56 and 58 extending in the spanwise direction.

0021As can be seen in Figs. 3, 4 and 5 deflecting mem­bers 50 are mounted to the root end of the blade and serve to deflect the dirt entrained air to one or more specific passageways.

0022The deflectors 50 are stamped out of sheet metal blank 52 and then is suitably attached to the root of the blade 10 by any well-known method such as brazing, welding, etc. The deflectors 50 which are defined by raised panels extending from the leading edge to the trailing edge and are positioned to overlie the passages intended to be protected. The dimensions of these panels will be predi­ cated on the size of the opening being protected. In this instance, the deflectors 50 deflect the dirt entrained cooling air into the trailing edge passage 56 and leading edge passage 58 and divert this contaminated air from the serpentine passages. The leading edge passage 58 and trailing edge passage 56 are formed so as to afford as little pressure losses as possible and receive air at sufficient velocity to carry the dirt to the dirt removal holes 60. The dirt free or substantially dirt free air can still get into the serpentine passages through the openings underneath the panels 50.

0023Figs. 6 and 7 illustrate a third embodiment of this invention utilizing a similar fabricated deflector where the dirt entrained air is directed to the high velocity passageway 70 and discharged away from the blade's inter­nal passageways through apertures 72 formed in the disk 74 of the turbine rotor. Again, as was the design of Figs. 3 to 5, the deflectors 76 are stamped out of a sheet metal stock 78 which is sized to overlie the passages at the root of the turbine blade. Also, the sheet metal plate 78 can be affixed to the blade in any suitable manner, by say brazing, welding or mechanical attaching means.

0024It is apparent from the foregoing that the embodi­ments of Figs. 3 through 7 can be utilized with existing internally cooled blades. Hence, such a design would be efficacious to "fix" an existing blade clogging problem.

0025Although this invention has been shown and described with respect to detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.