Blade of axial compressor of tjet engine

Abstract

FIELD: engine construction.SUBSTANCE: invention relates to axial compressors of turbofan gas turbine engines. A solid blade design of a given geometry is used in a limited range of diameters D1 / D2 of no more than 2.5, the blade profile is described by arcs of circles with the geometric centre of the section located on one straight line along the blade length, the blade edges are also made straight.EFFECT: relative simplicity of technology, wherein the angle of inclination of the profile chord to the flow in combination with the chord length, the radii of the concave part of the section and the radii of the convex part of the profile section ensure a sufficiently good efficiency of the compressor wheel with sufficient strength and good head in a wide range of compressor rotor speeds.1 cl, 3 dwg

Description

[0001] This invention relates to axial compressors for fan-type gas turbine engines. Its most effective application is in axial compressors for low-power turbofan engines with a thrust of 1000 to 5000 N.

[0002] A fan-driven gas turbine engine typically contains a compressor that forces air into the engine's combustion chamber. Two types of compressors are used: axial and centrifugal. In an axial compressor, the required air pressure at the combustion chamber inlet is generated by forcing the air through a number of compressor impellers. The impeller of an axial compressor consists of a base on which are mounted multiple blades, either integral with the base or blades that are removable and attached to the base. The demand for low-power, dual-circuit fan engines (1000-5000 N) has led to the need to simplify the engine's compressor design while maintaining a sufficiently high efficiency. The impeller, with its large number of complex-shaped blades, is most critical to the axial compressor's efficiency and is labor-intensive to manufacture.

[0003] A compressor blade design is known (Invention Certificate RU No. 2150612 C1). The blade comprises a section with a constant chord and a profile curvature angle decreasing with height in accordance with the condition of constant theoretical pressure, as well as peripheral and root sections, comprising 10-15% of the latter's height with a profile curvature monotonically increasing by 10-20% toward the tips in accordance with the condition of increased theoretical pressure. The peripheral and root sections of the blade are designed with a profile chord monotonically increasing by 15-30% toward the tips. This design of the blade ensures minimal profile losses.

[0004] The disadvantage of this design is the technological complexity of manufacturing the blade, as well as the concentration of stress at the transition point of the profile from straight to enlarged at the periphery.

[0005] A compressor blade design is known (Invention Certificate RU No. 2529272 C1). The axial compressor blade comprises a leading edge, a trailing edge, a trough, and a back with spherical vortex generators formed on its surface and concave inside the blade. Each vortex generator is equipped with at least two supply channels with outlet openings of diameter (0.05…0.25) D, equidistant from the vortex generator symmetry axis oriented in the direction of the oncoming flow. The distance from the vortex generator symmetry axis to the outlet opening is (0.1…0.4) D. The inlet openings of the supply channels are located on the trough of the blade, and the outlet openings are located at a distance of (0.025…0.7) D from the leading edge of the vortex generator. The supply channels are made at an angle of 20°…110° to the blade chord, where D is the diameter of the vortex generator imprint.The invention will increase the range of non-separating flow around the blades by up to 3%, increase the air flow through the compressor by up to 2% and increase the compressor efficiency by up to 4% due to the creation of a stable vortex structure of the flow in vortex generators.

[0006] The disadvantage of the blade is the difficulty of producing a large number of through channels of small diameter, which results in the high cost of the impeller and the lack of prospects for use in low-power dual-circuit fan engines.

[0007] A known axial compressor blade (Invention Certificate RU No. 2516739 C1) is considered the closest analogue based on a number of features. The axial compressor blade comprises a blade with a root and an S-shaped cross-section at the blade root. To improve efficiency, the leading edge of the blade in the S-shape area is bent toward the blade back, and the inflection point of the profile centerline is located at a distance from the leading edge equal to 0.05-0.15 of the profile chord. The profile has good efficiency.

[0008] A disadvantage of this blade is the complexity of its profile, limiting its application to high- and medium-thrust engines. Its use in low-thrust engines is practically impossible due to the difficulty of manufacturing blades or vanes of this profile.

[0009] The purpose of this invention is to develop a simple structure of axial compressor blade for low-power turbofan twin-circuit engines with a thrust of 1000 to 5000 N, with simple production technology and relatively low cost.

[0010] The stated objectives are achieved by: using simple geometric shapes when constructing the blade profile, optimizing the blade chord angle to the air flow direction, optimizing the number of blades placed on the base of the compressor impeller for maximum performance and maximum efficiency of the compressor impeller. The geometric dimensions of the blade that correspond to the stated objective are related by the following dependencies: the axial compressor blade consists of a concave descending surface of radius R1 and a convex advancing surface of radius R2, while the leading edge 1 (see Fig. 1) and the trailing edge of the blade 2 are made straight and sharp, that is, the transition edge from the concave to the convex surfaces of the blade is not blunted by a radius or chamfer. The root section 3 and the tip section 4 of the blade profile have the same geometry. The profile chord length L (see.Fig 2) is constant, its length is determined by the adopted angle of inclination of the blade A and the thickness of the blade wheel, determined by the required pressure created by the blade wheel based on the results of gas-dynamic modeling. The angle of inclination of the chord of the profile with respect to the axis of the incident gas flow A lies in the range of 36-38°, the value in the specified range is determined based on the results of minimizing friction losses and turbulization of the working flow using gas-dynamic modeling, for example, by the method of successive approximations. The cone of the narrowing of the blade wheel B lies in the range of 30-35°, the value in the specified range is accepted based on the results of the structural arrangement of the compressor. The radius of curvature of the concave part of the blade is determined from the expression: R1=β⋅L; where β is the flow property coefficient 2.9-3.1. The coefficient of the properties of the working gas flow characterizes the pressure in the flow and the degree of its turbulization.As a first approximation, for further modeling of the bladed wheel performance characteristics, the recommended value of β is 3.0; in the process of further wheel design, the coefficient can be reduced down to 2.9 in order to increase the bladed wheel performance, or reduced to 3.1 in order to simplify the wheel manufacturing technology or for other technical reasons. The greatest blade thickness, t, determined by the perpendicular to the midpoint of the inner radius (the radius of the concave part of the blade surface), is taken by the expression: t=L / γ; where γ is the coefficient taking into account the blade material 11.2-12.2. As a first approximation, the coefficient γ is recommended to be selected from the middle of the specified range, 11.7; in further wheel strength calculations, it should be refined to the optimal value, shifting to a higher value of up to 12.2 units in the case of excess blade strength for the adopted blade material., if the blade strength is insufficient, it can be reduced to a lower value of up to 11.2 units. The values ​​of the compressor wheel outer diameter D1 and the inner diameter D2 are taken based on the calculation of the required volumetric flow rate of the pumped gas, while the ratio D1 / D2 should not exceed 2.5.

[0011] The essence of the invention is explained by the drawings: Fig. 1 is an isometric view of the impeller of an axial compressor; Fig. 2 is the main view of the compressor impeller with the dimensions of the blade profile; Fig. 3 is a view of the impeller from the right.

[0012] Thus, the proposed technical solution simplifies the profile of the compressor impeller blade, allowing the blade wheel to be manufactured as a single piece using widely available technological equipment, ensuring low production costs.

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