JPS61207802A - Gas turbine engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Description: TECHNICAL FIELD This invention relates to gas turbine engine axial fans and compressors, and more particularly to the relationship of blade tips to adjacent shrouds or friction strips.

Background Art U.S. Patent No. 4, granted December 16, 1980
．． No. 239.452 and U.S. Pat. A shroud is disclosed having a groove proximate the tip.

As disclosed, for example, in the above-mentioned U.S. Pat. extends proximate the shroud or friction strip formed thereon. In some cases,
In the low pressure stage, where a soft abradable material such as synthetic rubber may be used, the grooves are formed by the blades moving radially outward during engine acceleration. Such a method helps ensure a tight fit of the members that fit together and avoid air leakage around the tip of the blade.

A problem that continues to plague engine engineers is how to minimize, if not prevent, such air leaks.

Although the structures disclosed in the two aforementioned US patents are directed to such a purpose, air leakage occurs in these as well.

The two aforementioned US patents also disclose other methods of reducing air leakage at the blade tips. The present invention improves upon the techniques disclosed in the two above-mentioned U.S. patents and improves engine operating efficiency beyond that obtained with previously known structures.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a gas turbine engine having an angled groove in the friction strip, shroud or engine case of the gas turbine engine proximate the tips of the fan or compressor blades. The shape of the tip of the blade and the inner surface of the groove when viewed in cross section are inclined with respect to the wall of the working medium flow path.

The present invention provides blades to eliminate gaps between the inner surface of the groove and the blade tips when the compressor or fan blades are displaced due to material growth caused by stable speed and temperature operating conditions. The tip of the groove and the inner surface of the groove are sloped.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention for use in a cold station, particularly a compression section, of a gas turbine engine is illustrated in which a flexible material is disposed on the inner peripheral surface of the engine case of the engine. and is abradable so that it can be ground by a rotating blade.

Thus, as disclosed in the above-mentioned U.S. Pat.
When the friction strip is accelerated to its maximum operating speed, it cuts into the friction strip to form a groove.

However, the shape of the groove may be formed by machining prior to operation of the engine. An improvement of the invention is the particular shape of the blade tip and cooperating groove.

Compression section 1 of axial flow compressor of gas turbine engine
A portion of 0 is shown in FIG. A flow path 16 for working medium gas extends axially through the compression section 10. An outer wall 18 having an inwardly facing surface 20 and an inner wall 22 having an outwardly facing surface 24 define the flow path 16 .

Multiple rows of axially spaced rotor blades, as illustrated by a single blade 26, extend radially outwardly from the rotor across the flow path to a position proximate the outer wall 18. Each blade 26 has an unshrouded tip 28 and is formed in the cross-sectional shape of an airfoil. Each blade thus has a compression side and a suction side, with an upstream end 30 and a downstream end 3 as shown.
2. A stator seal land 34 extends beyond the tips of the rotor blades in each row. Each seal land has a circumferentially extending groove 36 formed to a depth D in its inward facing surface 37.

Multiple rows of stator vanes, as shown by a single vane 38, extend inwardly across the flow path 16 from the stator.
It is cantilevered so as to extend radially inward to a position close to 22. Each vane has a tip 40 without a shroud in the illustrated embodiment and is shaped like an airfoil section. Each vane thus has a compression side and a suction side, and has an upstream end 42 and a downstream end 44 as shown. A rotor seal land 46 extends beyond the tips of each row of stator vanes. Each seal land 46 is formed with a groove 48 extending in the circumferential direction.

Under engine non-operating conditions, the blade tip 28
is in a state of being more distant than the inward direction. The dark MH of the tip 28 and the inward facing surface 20 allows assembly of these parts. In response to the centrifugal and thermally generated forces generated when the engine is accelerated to high operating speeds, the blade tips 28 grow radially outward and are disposed in the stator seal lands 34. Grind the groove 36.

The point of the blade closest to the bottom of the blade is called the "pinch point" and typically occurs when the engine is operated transiently at maximum speed or power conditions. When the engine reaches a region of thermal stability at a given operating speed, the outer wall, including the seal land, is relative to the blade tip to the point where the blade tip and inner surface 37 define a gap. axially and radially.

One problem with the conventional structure shown in FIG. 2, which shows a conventional structure, is that as the operating speed of the engine increases, the degree to which the blade 50 fits into the groove 54 increases and the vertical wall 53 of the groove increases. This means that air is pumped into the air, creating turbulence. The turbulent flow indicated by arrow A becomes an obstruction in the flow path of the working medium of the engine and adversely affects the performance of the engine. To avoid deleterious turbulence losses at maximum operating speeds, the maximum penetration depth of the blade tip must be controlled. Under low engine speed operating conditions, the blades do not fit into the grooves and air leakage easily occurs between the outer wall of the flow path and the tip of the blade.

It is desirable to accommodate a pressure gradient across the blade tip that causes air to leak from the high pressure side to the low pressure side due to the pressure generated by the pumping action at the blade tip. In the conventional construction shown, the full width of the blade acts on the air and tends to overpressurize the air, thus creating harmful turbulence.

According to the present invention, the tip of the blade is formed in such a shape that it is inclined with respect to the wall of the working medium flow path. This is best illustrated in FIG. When the grooves are machined as described above, they are formed to define the shape of the inner surface 37. When viewed in cross section of the groove, the axial extension of the inner surface 37 makes an angle α with respect to the flow path defined by the inward facing surface 20. Such a shape realizes two important features:

(1) In conventional construction, when any portion of the blade tip fits into the groove, the full width of the blade pumps air against the vertical walls of the groove. Therefore, the blade hardly fits into the groove before harmful turbulence occurs. In contrast, in the structure shown in Figure 3, when the engine operating speed reaches a speed that causes the tip of the blade to fit into the groove, only the rear portion of the tip of the blade directs air against the straight wall of the groove. Pump. The tip of the blade is therefore able to penetrate deeper into the groove before creating a turbulence limiting condition. Under low speed operating conditions, the tip of the blade in the present invention can fit into the groove, whereas in the conventional structure the tip of the blade cannot fit into the groove.

(2) By slanting the grooves in the proper direction, the blade tip and outer wall of the flow path are thermally stable under any given engine operating speed condition. Relative axial movement between the tip and the outer wall of the channel reduces the gap therebetween. Thus, by knowing the direction of axial growth of the engine case relative to the direction of axial movement of the blades, such as the direction of the arrow, gaps can be reduced.

FIG. 4 shows another example of how the tip of the blade may be shaped to address the air leakage problem described above. The tip of the blade 70 is formed into a serrated shape and has a plurality of grooves 72 parallel to each other. In each groove, the inner surface 74 is inclined with respect to the working medium flow path, and the same effect as described above can be obtained.

The preferred embodiment described in connection with FIG.
Chiknoros Corporation's Pratt & Tony Aircraft (Pratt &
Tests on the PW2037 engine manufactured by the Whitney Aircraft Division have shown that specific impulse fuel consumption is improved by perhaps 0.1-0.2%.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. This will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of the compression section of a gas turbine engine schematically illustrating the inclined grooves of the engine case or friction strip of the present invention. FIG. 2 is an enlarged partial view showing a non-slanted groove proximate the tip of a compressor blade of a conventional construction. FIG. 3 is an enlarged partial view showing one blade and the sloping groove formed in the engine case in accordance with the present invention. FIG. 4 is an enlarged partial view showing the tip and groove of a blade according to another embodiment of the present invention. 10... Compression section, 16... Channel, 18...
・Outer wall, 20... Inward surface, 22... Inner wall, 24.
... outward facing surface, 26... blade, 28... tip,
30... Upstream end, 32... Downstream end, 34.
...Seal Land. 36... Groove, 37... Inward surface, 38... Vane, 40... Tip, 42... Upstream end, 44...
downstream end. 46...Seal land, 48...Groove, 50...Blade. 52...Inner surface, 53...Vertical wall, 54...Groove, 7
0...Blade, 72...Groove, 74...Inner surface Patent Applicant: United Chiknorrhosis Corporation

Claims (2)

[Claims] (1) A gas turbine engine operated under high-power operating conditions and low-power operating conditions, including an engine case and a rotor rotatably supported within the engine case and having a plurality of radially extending blades. and a portion of the engine case has a circumferentially extending groove having an inner surface and a vertical wall, the inner surface facing the tip of the blade, and a portion of the engine case having a circumferentially extending groove having an inner surface and a vertical wall; The inner wall of the engine case and the outer surface of the rotor define a flow path for the working medium of the engine, and the inner surface of the groove is complementary to the shape of the engine case. is formed in an inclined shape with respect to the inner wall of the blade, so that when the engine is under the low power operating condition, a portion of the tip of the blade is disposed within the groove, whereby the groove is A gas turbine engine configured to pump air against the vertical wall, thereby inhibiting migration of the working medium from a high pressure side of the blades to a low pressure side of the blades. (2) a gas turbine engine capable of operating over a power range having an engine case and a plurality of radially extending blades forming a plurality of compression stages in a compression section of the engine; a plurality of axially spaced rotors rotatably supported within an engine case, the inner wall of the engine case and the outer surface of the rotor defining a gas flow path for the working medium of the engine; and the inner wall of the engine case has a groove extending over the tip of the blade as the tip of the blade moves radially outward when the engine is accelerated to high power operating conditions in the power range. the tip of the blade is axially inclined from a smaller diameter portion at the leading edge to a larger diameter portion at the trailing edge; The inner surface of the groove has a slope corresponding to the slope of the tip of the blade, so that when the engine is operated at low power operating conditions in the power range, the blade is lower than the inner surface of the groove. The blade is retracted so that only the larger diameter portion of the blade fits into the groove, so that the portion of the blade that fits into the groove is close to the tip and pumps the working medium of the engine. a gas turbine engine configured to minimize flow of the working medium over the tip from the high pressure side to the low pressure side of the blade.