Turbine blade form

Abstract

The invention relates to working blades of turbojet engine turbines. A working blade comprises an airfoil portion of an outer surface and an airfoil portion of an inner surface which have an aerodynamic shape with a nominal profile formed in accordance with characteristic reference points, the characteristic points being smoothly connected by a quadratic spline, wherein the section of the airfoil in a direction along the radius of the turbine wheel is constant, and the blade may be made of single-crystal aluminium oxide (Al2O3), wherein the blade is produced by cutting a single crystal. The invention makes it possible to simplify the structure of a turbine and to reduce the cost of manufacturing same, while ensuring that the turbine is sufficiently efficient across a wide range of rotation speeds, and also makes it possible to increase the turbine inlet temperature without the need for cooling channels in the blade.

Description

[0001] Turbine blade shape

[0002] The invention relates to turbine blades of turbojet engines. Its application is most effective in low-power fan turbojet dual-circuit engines with a thrust of 1000 to 5000 N.

[0003] A turbojet engine contains a turbine that sets the engine rotor in motion. There are three types of turbine blades: active, reactive, and active-reactive. The most widely used type of blade profile in turbojet engines is the active-reactive type. The operation of a turbine with an active type of blade profile is characterized by lower operating peripheral speeds and lower efficiency compared to a reactive profile. The turbine wheel consists of a base on which a multitude of profiled blades are fixed, which form a single structure with the base. The need for low-power dual-circuit fan engines of 1000-5000 N has led to the need to improve the profile of the turbine blades, simplify the design of the engine turbine while maintaining a sufficiently high efficiency. The most critical for the efficiency of the turbine and labor-intensive to manufacture is its wheel with a large number of blades of a complex profile.

[0004] A design of a turbine blade of an active-reactive type is known (Invention Certificate RU 2 498 082 C2). A single-crystal turbine blade is manufactured by casting with directional crystallization and contains a blade airfoil, a final structural element of the blade airfoil, and a transition zone. The blade airfoil has a leading and trailing edge, C-shaped trough and C-shaped back sides, a midline, and a longitudinal axis. The final structural element of the blade airfoil contains the final side of the blade airfoil on the gas-air tract side, forming an angle with the longitudinal axis of the blade airfoil. The transition zone is located between the blade airfoil and the final side of the blade airfoil and forms a thickening of the blade airfoil.The transition zone extends around the leading edge between a point located on the back of the blade airfoil and on the end side of the end structural element of the blade airfoil upstream of the back of the C-shaped form, and a point located on the trough of the blade airfoil and on the end side of the end structural element of the blade airfoil upstream of the trough of the C-shaped form.

[0005] The disadvantage of this design is the technological complexity of manufacturing the blade, the need to use specialized technological equipment for this task. The efficiency of using the blade at a relatively high peripheral speed.

[0006] A design of a turbine blade of an active-reactive type is known (Invention Certificate RU 2 383 748 C2). The feather of a guide or nozzle blade, or a working blade of a blade machine, primarily a gas turbine, has at least one thickening of its profile on its radially inner end section and / or on its radially outer end section, which has a positive effect on the aerohydrodynamic characteristics. The thickening is made cut in the area of ​​the leading edge of the blade feather to form a front surface, respectively, a base surface. The thickening is made in the area of ​​the leading edge of the blade feather with a cut having a surface in the form of a circular or cylindrical segment. The invention is aimed at creating a blade having improved aerodynamic characteristics.

[0007] The disadvantage of this design is the complexity of blade profiling and the efficiency of the profile at high peripheral speeds.

[0008] A turbine blade design is known (Invention Certificate RU 2 342 538 C2). The turbine blade includes an aerodynamic profile, a base, a root and a dovetail joint. The blade has a nominal profile of the inner central part essentially in accordance with the X, Y and Z rectangular coordinate values ​​given in Table I. The Z values ​​are dimensionless values ​​from 0 to 1, converted to Z distances in inches by multiplying the Z values ​​by the blade height in inches. The X and Y values ​​are distances in inches that, after being connected by smooth continuous arcs, define the sections of the profile of the inner central part at each Z distance along the blade. The sections of the profile at the Z distances are connected smoothly with each other to form the said profile of the inner central part of the blade.The distances X, Y and Z can be proportionally changed depending on the same constant or number to obtain a proportionally increased or proportionally decreased profile of the inner central part. The nominal profile of the inner central part, determined by the distances X, Y and Z, is laid on the envelope with an accuracy of ±0.039 inches in directions normal to any place on the surface of the inner central section. The invention allows improving the aerodynamic efficiency. The disadvantage of this design is the extremely complex manufacturing process.

[0009] The design of a turbine blade is known (invention certificate RU 2 178 086 C2). The gas turbine blade has a profile part consisting of the contours of the back, trough and edges. The contours of the back and trough are formed by sinusoidal spirals. The invention allows to reduce energy losses in the blade crowns, reduce the time of blade profiling and expand the area of ​​reliable construction of blade profiles.

[0010] The disadvantage of this design is the low efficiency of the blades when at relatively low turbine wheel rotation speeds.

[0011] A turbine blade design is known (invention certificate RU 2 518 767 C2) accepted for a number of features as the closest analogue. The turbine wheel contains turbine blades containing a profile part having an aerodynamic shape. This aerodynamic shape has a nominal profile corresponding to the data in the tables given in the description. The coordinate values ​​are smoothly connected by an arc of radius R to form a section of the profile part at each distance from the wheel rotation axis. The sections of the profile are smoothly connected to each other to form a complete aerodynamic shape. The proposed profile of the profile part of the blade ensures as a result an improvement in the efficiency and load-bearing capacity of the aerodynamic part and the blades as a whole.

[0012] The disadvantage of this design is the technological complexity of obtaining a smooth blade profile with a variable shape of its profile along the height of the blade; specialized technological equipment is required, which determines the high cost of blade production.

[0013] The objective of this invention is to develop a simple design of a turbine blade for low-power fan turbojet dual-circuit engines with a thrust of 1000 to 5000 N, which differs from its analogue in its simple production technology, efficient operation at low circumferential speeds, low production cost, and the possibility of manufacturing on universal process equipment with a comparatively high efficiency. The second claim of the invention allows for the production of single-crystal blades from a single-crystal aluminum oxide (Al2O3), which will increase the service life of the turbine blades and allow the working gas temperature to be raised by increasing the heat resistance of the blades. The stated objective is achieved by using an active blade profile that is constant in its height with a profile constructed using the characteristic base points shown in Fig.2 where the dimensions are given in millimeters, and the characteristic points are smoothly connected by a quadratic spline, while the section of the profile in the direction along the radius of the wheel is constant, while the blade has three characteristic surfaces, marked in Fig. 1: a convex surface (2), a concave surface (3), an extreme surface (1) the most distant from the axis of rotation of the turbine wheel. In the second embodiment, the blade is made by cutting from a single crystal of aluminum oxide (Al2O3), which allows to increase the working life of the turbine due to the greater heat resistance of the blades and the wear resistance of the single crystal of oxide.

[0014] The essence of the invention is explained by drawings. Fig. 1 shows a typical view of a turbine wheel with blades of this shape. Position (1) marks the surface of the blade that is most distant from the axis of rotation, position (2) the convex part of the blade, position (3) the concave part of the blade profile. Fig. 2 contains the shape of the blade section with the positions of the nodal points, the interpolation of the surface between the points is performed by a quadratic spline.

[0015] This invention will allow to produce turbine blades operating at relatively low circumferential speeds using widespread, universal technological equipment, for example, 5-axis CNC milling machines, will ensure low cost of production of turbine wheels of turbojet engines. The selected geometry of the blade allows to obtain maximum efficiency and high pressure under specified initial conditions. The use of monocrystalline aluminum oxide (Al2O3) for the manufacture of blades according to the second point of the formula of the invention will increase the service life of the turbine blades and increase the temperature of the working fluid (combustion products), thus increasing the efficiency of the turbine.

[0016] The description of this invention contains a specific embodiment of the turbine blade profile, but is not limited to it; scaling the blade profile and using a quadratic spline in its construction fall under the essence and scope of legal protection of the invention formula.

Claims

5 Invention formula 1. A working blade of a turbojet engine turbine (1), comprising a profile portion of the outer surface (2) and a profile portion of the inner surface (3), having an aerodynamic shape, with a nominal profile constructed according to characteristic base points shown in Fig. 2, in which the dimensions are given in millimetres, and the characteristic points are smoothly connected by a quadratic spline, while the section of the profile in the direction along the radius of the wheel is constant.

2. A blade according to item 1, which is made from a single crystal of aluminum oxide (Al2O3), wherein this blade is manufactured by cutting the single crystal.

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