Blade structure design method and fan

Abstract

The invention provides a blade structure design method which comprises the following steps: grading circumferentially distributed blades on the basis of the bearing load of the blades; and different materials and / or blade types and / or connecting structures are adopted for the blades of different grades. According to the bearing characteristics, careful grading and classification of the blades are carried out, the graded and classified blades serve as the design basis, and design of various blade characteristics can be carried out on the premise that the blade safety is guaranteed. The invention further provides a fan.

Description

Technical Field

[0001] The present invention relates to the field of aeroengines, and in particular to the field of aeroengine blade design. Background Art

[0002] In aviation turbofan engines, especially high bypass ratio turbofan engines, the design of force and torque transmission paths is very important. In a classic CFM56 series aircraft engine, an independent large support plate structure is set behind the fan. The support plate is used to provide support rigidity and transmit loads at the same time. At this stage, advanced aircraft engines in the world have cancelled structural features such as independent large support plates behind the fan, and replaced them with a fusion design of fan OGV and support plates. The fusion-designed OGV support plates and blades not only play the role of transferring loads, but also serve as outlet diversion functions.

[0003] With the further development of aero-engine material technology, basic research, and design technology, various OEM companies have launched more advanced new-generation aero-engine research and development. Among them, weight and noise are two important indicators of aero-engine advancement. At the same thrust level, lighter weight often means more competitiveness and higher commercial potential; while lower noise often means a better flight experience and a more comfortable flying environment for air passengers.

[0004] Safety and lightweight design are often contradictory. The use of lighter materials and structural features often means problems such as insufficient structural rigidity and insufficient strength margin; the use of noise-reducing blade design often means the introduction of noise-absorbing materials or features in structural design and material application, which poses a higher challenge to overall safety. Summary of the invention

[0005] An object of the present invention is to provide a blade structure design method.

[0006] The blade structure design method for achieving the above purpose includes the following steps: grading the circumferentially distributed blades based on the blade bearing load; using different materials and / or blade shapes and / or connection structures for blades of different grades.

[0007] In one or more embodiments, the blades are divided into first-level bearing, second-level bearing, third-level bearing, and fourth-level bearing according to the load-bearing load from large to small; the first-level bearing includes two blades located at 12 o'clock and 6 o'clock or closest to the 12 o'clock and 6 o'clock positions; the second-level bearing includes two blades located at 12 o'clock or closest to 12 o'clock and adjacent to the blade of the first-level bearing in the circumferential direction; the blades of the fourth-level bearing and the third-level bearing are alternately arranged in the circumferential direction, and the blades close to the second-level bearing are the blades of the fourth-level bearing, and the blades close to 6 o'clock or closest to the 6 o'clock position of the first-level bearing are the blades of the third-level bearing.

[0008] In one or more embodiments, the blades of the first-stage load-bearing and the second-stage load-bearing are made of titanium alloy, and the blades of the third-stage load-bearing and the fourth-stage load-bearing are made of aluminum alloy.

[0009] In one or more embodiments, the blades of the second-stage carrier, the third-stage carrier, and the fourth-stage carrier adopt the same aerodynamic blade profile.

[0010] In one or more embodiments, the blades in which the parts are loaded are hollow blades or partially hollow blades.

[0011] In one or more embodiments, the inner diameter and outer diameter of the first-stage, second-stage, and third-stage load-bearing blades all adopt a bolt connection structure, and the inner diameter of the fourth-stage load-bearing blade adopts an inner diameter bolt connection structure, and the outer diameter adopts a pin constraint structure.

[0012] In one or more embodiments, the bolt connection structure located at the inner diameter includes a first screw hole arranged at the radial inner end of the blade edge plate, and the first screw hole extends in the axial direction. The bolt connection structure located at the outer diameter includes a base arranged on the tip surface of the blade and a second screw hole located on the base, and the second screw hole extends in the radial direction.

[0013] In one or more embodiments, the pin restraint structure comprises a pin hole disposed on the tip surface of the blade, and the pin hole extends in a radial direction.

[0014] In one or more embodiments, the cross-section of the pin hole is non-circular.

[0015] In one or more embodiments, the method also includes the following steps: drawing a curve graph of relative displacement at the blade damage safety gap and stiffness ratio, wherein the stiffness ratio is defined as the stiffness ratio of a certain level of load-bearing blade to another level of load-bearing blade, and determining the maximum or minimum value of the stiffness ratio of a certain level of load-bearing blade to another level of load-bearing blade during design based on the relative displacement at the blade damage safety gap.

[0016] Another object of the present invention is to provide a fan, comprising a plurality of blades distributed circumferentially, wherein the material and / or blade shape and / or connection structure of each blade is determined according to the above-mentioned blade structure design method.

[0017] The above-mentioned blade structure design method flexibly classifies the blades according to their load-bearing capacity. On the premise of clarifying the load-bearing capacity of blades at each level, suitable materials and structures are selected according to the rigidity and load-bearing capacity of blades at different levels. It can design blades with various requirements while meeting safety requirements, ensure the overall structural rigidity while meeting the strength margin of each OGV blade, and provide a design basis and guidance classification for subsequent lightweight design, noise reduction design, and cost reduction design. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0019] Figure 1 is a schematic diagram of the leaves after classification;

[0020] Figure 2A-2B It is a schematic diagram of the bolt connection structure at the inner diameter and outer diameter of the blade;

[0021] Figure 3 is a schematic diagram of the bolt connection structure at the inner diameter of the blade;

[0022] Figures 4A-4B It is a schematic diagram of the blade structure of the fourth-level load-bearing;

[0023] Figure 5 is a schematic diagram of the pin constraint structure located at the outer diameter;

[0024] Figure 6 It is a schematic diagram of the pin hole;

[0025] Figure 7 It is the damage safety displacement variation curve;

[0026] Figure 8 is the distribution diagram of yield safety factor of each OGV blade under alpha = 0.8 and 1.0;

[0027] Fig. 9 is the distribution diagram of yield safety factor of each OGV blade under alpha = 0.6 and 1.0;

[0028] Fig.10 It is the blade stress distribution cloud diagram of the first-stage load of the OGV blade;

[0029] Fig.11 It is a flow chart of the blade structure design method. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0031] It should be noted that these and other subsequent drawings are only examples and are not drawn to scale, and should not be used to limit the actual scope of protection required by the present invention.

[0032] Blades, such as the outlet guide vane (OGV) of the fan, should meet the overall rigidity requirements. Specifically, the overall deformation under the maximum torque condition is reasonable and meets the design expectations; it should also meet the strength requirements, which is manifested in a certain safety margin under normal aerodynamic load conditions, no yield under limited maneuvering load conditions, and no rupture under extreme load conditions. Since the blade stress caused by the aircraft maneuvering load is relatively low, it is necessary to ensure that the minimum yield safety factor of the entire circle of OGV blades is not less than 1.23 under the maximum aerodynamic load condition during the design stage.

[0033] However, the blades also need other design features, such as noise reduction design, lightweight design, cost reduction design, etc. Other design features often conflict with the safety of the blades. Based on the above restrictions, the blade structure design method disclosed in this disclosure classifies the load-bearing types of the fan OGV in detail, and adopts different materials and structural features according to different types of rigidity, strength and load-bearing.

[0034] Specifically, the blade structure design method includes the following steps: based on the blade load, circumferentially distributed blades are classified; and then different materials and / or blade shapes and / or connection structures are used for blades of different classifications.

[0035] As in Figure 1 In the illustrated embodiment, the fan OGV has a total of 48 blades in one circle, and the 48 fan OGV blades are divided into four levels according to the load-bearing capacity.

[0036] The first-level load A is the two blades at 12 o'clock and 6 o'clock or the closest to 12 o'clock and 6 o'clock positions, which serve as the main fan OGV and provide the main rigidity and load, and the preferred material is TC4 titanium alloy. The second-level load B is the two blades located at 12 o'clock or the closest to 12 o'clock of the first-level load, which are adjacent to the circumferential blades, and provide auxiliary rigidity and load for the first-level load, and the preferred material is TC4 titanium alloy.

[0037] The blades of the fourth-stage load C and the third-stage load D are arranged alternately in the circumferential direction, and the blades close to the second-stage load are the blades of the fourth-stage load, and the blades close to the 6 o'clock position of the first-stage load or the closest to the 6 o'clock position are the blades of the third-stage load. In this way, the third-stage load includes 24 fans OGV arranged at intervals, preferably made of aluminum alloy; the fourth-stage load includes 22 fans OGV arranged at intervals, preferably made of aluminum alloy.

[0038] The material properties of aluminum alloy and titanium alloy are shown in the following table.

[0039]

[0040] The blade connection structure can also be further determined according to the above classification. For example, in some embodiments, the inner diameter and outer diameter of the blades of the first-level load-bearing, second-level load-bearing, and third-level load-bearing are all bolted, and the inner diameter of the blade of the fourth-level load-bearing is bolted, and the outer diameter is pin-constrained.

[0041] like Figure 2A and 2B As shown, the inner diameter of the first-stage bearing, the second-stage bearing, and the third-stage bearing blades are axially connected by 4 bolts, and the outer diameter is radially connected by 4 bolts. The tip surface of the blade at the outer diameter includes a pair of support seats 101, and the support seats 101 are provided with a pair of screw holes 102 for radial connection with bolts located at the casing, etc. The radial end of the blade edge plate 103 includes a flange edge 104, and the flange edge is provided with screw holes 102 for axial connection with bolts at the wheel, etc.

[0042] The connection form at the inner diameter of the blade of the fourth stage load is the same as Figure 3 The bolt connection structure is consistent with that shown, and the radial pin constraint structure at the outer diameter is as follows Figure 5 As shown, the blade tip surface at the outer diameter of the blade includes a pin hole 105 extending in the radial direction, which radially cooperates with the pin at the casing, etc., thereby constraining the circumferential and axial freedom of the blade carried by the fourth stage and releasing its radial constraint.

[0043] The radial pin hole 105 is preferably non-circular, such as Figure 6 As shown, the blades can be prevented from torsional deformation under aerodynamic loads.

[0044] In some embodiments, the second-stage, third-stage, and fourth-stage load-bearing blades are made to adopt the same aerodynamic blade profile, such as having the same leading edge angle, trailing edge angle, blade profile angle, chord length and other blade profile parameters, to ensure that the blade profile has excellent aerodynamic performance. The other three-stage load-bearing blades are designed with a flange structure on the outer edge surface, which is connected to the outer casing by 4 radial bolts. The first-stage load-bearing blades are designed to cancel the flange structure and directly use radial pins to reduce the overall weight.

[0045] In some embodiments, the blades of the third-stage load-bearing and the fourth-stage load-bearing may also be hollow blades or partially hollow blades.

[0046] The third-stage OGV blade mainly bears aerodynamic loads and can be designed with an adaptive hollow core to reduce noise, but the reduction in bending rigidity cannot exceed 5% compared with the solid blade configuration. The fourth-stage OGV blade can be designed with an adaptive hollow core to reduce noise compared with the third-stage OGV blade, and the reduction in bending rigidity cannot exceed 20%.

[0047] Figure 7 The blade damage safety displacement change curve obtained by the above design method is shown. When the fan working condition is the maximum aerodynamic load (such as the torque is the maximum working condition), the curve of the relative displacement at the blade damage safety gap and the stiffness ratio is drawn, the horizontal axis is the stiffness ratio, and the vertical axis is the displacement at the damage gap.

[0048] Blade damage safety clearance, or auxiliary installation section damage safety clearance, refers to the inverted trapezoidal structure design of the front section under the premise of the rear force and torque transmission installation system design of the commercial high bypass ratio engine, which releases the rotational freedom. Under normal load conditions, there is a gap between the middle pin and the hole. In special circumstances such as the fan blade flying off and the pin breaking on one side, the middle pin eats up the gap and participates in the load-bearing, which is the damage safety clearance.

[0049] Figure 7 The medium stiffness ratio is defined as the ratio of the blade stiffness of the fourth-level load to the blade stiffness of the third-level load, which is represented by alpha. The calculation results show that the smaller the stiffness ratio alpha, the greater the deformation at the damage safety gap, such as Figure 7 When alpha = 0.788, the deformation displacement at the damaged safety gap is approximately equal to 9 mm.

[0050] The high bypass ratio turbofan engine generally transmits axial force through the thrust rod and torque through the stator casing and the main mounting section. Therefore, under normal design conditions, the auxiliary mounting section on the outer ring of the fan OGV is designed as a trapezoidal structure, and there is a gap between the middle pin and the hole, and no torque is transmitted under normal aerodynamic load conditions. Generally, the damage safety gap reserved for the middle hole is no more than 10mm, and a 10% margin needs to be reserved during the design stage, so it should be ensured that the relative deformation of the damage safety gap of the entire fan OGV under the maximum torque load is no more than 9mm.

[0051] Therefore, in some embodiments, the rigidity design may require that the ratio of the rigidity of the fourth-stage load-bearing blade to the rigidity of the third-stage load-bearing blade be greater than 0.788.

[0052] In some embodiments, by drawing a curve graph of the relative displacement at the blade damage safety gap and the stiffness ratio, the stiffness ratio is defined as the stiffness ratio of a certain level of load-bearing blades to another level of load-bearing blades. According to the relative displacement at the blade damage safety gap, the maximum or minimum value of the stiffness ratio of a certain level of load-bearing blades to another level of load-bearing blades is determined during the design.

[0053] Figure 8 and Fig. 9 The three cases of alpha being 0.6, 0.8 and 1.0 were calculated respectively, and the curves of relative displacement at the damaged safety gap and stiffness percentage were plotted.

[0054] Figure 8 The yield safety factor distribution diagram of the fan OGV blade stress under the maximum aerodynamic load condition under alpha = 0.8 and 1.0 is shown. Each point on the curve in the figure represents a blade at a different position in the circumferential direction, and the distance from the point to the origin is the yield safety factor value. The solid curve is the yield safety factor of each blade under alpha = 0.8, the dashed curve is the yield safety factor of each blade under alpha = 1.0, and the dotted line in the middle is the standard of the yield safety factor equal to 1.23.

[0055] Fig. 9 The figure shows a comparison of the fan OGV blade stress under the maximum aerodynamic load condition (maximum torque) when alpha=0.6 and 1.0, and a yield safety factor distribution diagram is drawn based on the material mechanical properties. Fig. 9 Each point on the middle curve represents a blade at a different circumferential position. The distance from the point to the origin is the yield safety factor value. The solid curve is the yield safety factor of each blade when alpha = 0.6, and the dotted curve is the yield safety factor of each blade when alpha = 1.0. The dotted circle in the middle is the standard for a yield safety factor of 1.23.

[0056] pass Figure 8 and Fig. 9 The calculation results show that the smaller alpha is, the greater the stress of the first-stage load-bearing OGV is, and the smaller the corresponding yield safety factor is. Among them, when alpha = 0.6, the corresponding yield safety factor of the first-stage load-bearing blade is 1.19. Compared with the standard yield safety factor of 1.23, the difference does not meet the margin requirement. Through interpolation, when alpha = 0.66, the yield safety margin of the first-stage load-bearing OGV is 1.23, so alpha needs to be greater than 0.66 during design, that is, the ratio of the rigidity of the fourth-stage load-bearing blade to the rigidity of the third-stage load-bearing blade needs to be greater than 0.66. Different requirements are given through stiffness requirements and strength requirements.

[0057] According to the above-mentioned first-level load, the main stress distribution cloud diagram of the blade is as follows Fig.10 As shown, according to the stiffness and strength calculation results, when alpha>0.788, the stiffness and strength requirements can be met.

[0058] Therefore, when designing the structural configuration, when the bending rigidity of the fourth-stage load-bearing blades is reduced by no more than 20% relative to the third-stage load-bearing blades, the overall fan OGV stiffness and strength can meet the requirements.

[0059] In combination with the introduction to the above-mentioned design method, it can also be understood that a fan is provided in which the blade material and / or blade shape and / or connection structure are determined according to the above-mentioned blade structure design method.

[0060] The present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or multiple times in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0061] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A blade structure design method, characterized in that: The steps include: Based on the blade bearing load, the circumferentially distributed blades are graded; Different materials and / or blade shapes and / or connection structures are used for blades of different grades.

2. The design method according to claim 1, characterized in that: The blades are divided into first-level bearing, second-level bearing, third-level bearing and fourth-level bearing according to the load-bearing load from large to small; the first-level bearing includes two blades located at 12 o'clock and 6 o'clock or closest to the 12 o'clock and 6 o'clock positions; the second-level bearing includes two circumferentially adjacent blades located at 12 o'clock or closest to 12 o'clock of the first-level bearing; the blades of the fourth-level bearing and the third-level bearing are alternately arranged circumferentially, and the blades close to the second-level bearing are the blades of the fourth-level bearing, and the blades close to 6 o'clock of the first-level bearing or closest to the 6 o'clock position are the blades of the third-level bearing.

3. The design method according to claim 2, characterized in that: The blades of the first-stage load-bearing and the second-stage load-bearing are made of titanium alloy, and the blades of the third-stage load-bearing and the fourth-stage load-bearing are made of aluminum alloy.

4. The design method according to claim 2, characterized in that: The second-stage load-bearing, third-stage load-bearing and fourth-stage load-bearing blades adopt the same aerodynamic blade shape.

5. The design method according to claim 2, characterized in that: The blades that carry the loads in some stages are hollow blades or partially hollow blades.

6. The design method according to claim 2, characterized in that: The inner diameter and outer diameter of the blades of the first, second and third stage loads are all connected by bolts, and the inner diameter of the blades of the fourth stage loads is connected by inner diameter bolts, and the outer diameter is restrained by pins.

7. The design method according to claim 6, characterized in that: The bolt connection structure located at the inner diameter includes a first screw hole arranged at the radial inner end of the blade edge plate, and the first screw hole extends in the axial direction. The bolt connection structure located at the outer diameter includes a base arranged on the tip surface of the blade and a second screw hole located on the base, and the second screw hole extends in the radial direction.

8. The design method according to claim 6, characterized in that: The pin restraining structure comprises a pin hole arranged on the tip surface of the blade, and the pin hole extends in a radial direction.

9. The design method according to claim 8, characterized in that: The cross section of the pin hole is non-circular.

10. The design method according to claim 1, characterized in that: The method also includes the following steps: drawing a curve graph of relative displacement at the blade damage safety gap and stiffness ratio, wherein the stiffness ratio is defined as the stiffness ratio of a certain level of load-bearing blades to another level of load-bearing blades, and determining the maximum or minimum value of the stiffness ratio of a certain level of load-bearing blades to another level of load-bearing blades during design based on the relative displacement at the blade damage safety gap.

11. A fan comprising a plurality of blades distributed circumferentially, characterized in that: The material and / or blade shape and / or connection structure of each blade are determined according to the fan blade structure design method as described in any one of claims 1-10.

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