Meridian flow channel for compact double duct compression system

Abstract

The present invention discloses a meridian flow passage for a compact dual-duct compression system, which belongs to the technical field of aero-engines. It comprises a fan rotor, wherein the upper part of the fan rotor outlet is connected to the outer duct flow passage, and the lower part is connected to the inner duct flow passage; the inner duct flow passage comprises an inner duct transition section diffuser, an oblique flow compressor rotor and an oblique flow compressor diffuser; the inner duct transition section diffuser is connected to the lower part of the fan rotor outlet; the oblique flow compressor rotor is connected between the inner duct transition section diffuser and the oblique flow compressor diffuser. The transition section between the fan rotor and the oblique flow compressor rotor is combined into one, and the inner duct transition section diffuser acts as both a transition section and a diffuser, which reduces the axial length of the system and simplifies the system structure. It is combined with the outer duct flow passage to realize the function of inner and outer duct dual pressure ratio compression of a turbofan engine.

Description

Technical Field

[0001] The invention relates to a meridian flow channel shape for a compression system, in particular to a meridian flow channel for a compact double-duct compression system, belonging to the technical field of aeroengines. Background Art

[0002] Due to the advantages of simple structure, low cost and high thrust-to-weight ratio, micro-turbojet engines are currently mostly used as power for cluster drones and intelligent patrol ammunition. However, miniaturization will also bring many adverse effects such as large relative processing and assembly errors, large relative tip clearance, and large boundary layer proportion, resulting in low engine component efficiency and high fuel consumption, which greatly limits the further improvement of aircraft performance. The current commonly used methods to reduce engine fuel consumption mainly focus on improving component performance, including compression ratio, efficiency, etc., but the limitations of miniaturization, low cost and other factors will make the performance improvement very limited, and the technical difficulty is huge.

[0003] The micro-turbofan engine developed on the basis of the micro-turbojet engine is also a technical means to reduce the engine fuel consumption rate. The most complex system of the turbofan engine is the compression system, which includes the fan rotor and stator, transition section, internal compressor rotor and stator, intermediate casing, outer casing, etc. It has many parts, complex structure and high cost. If conventional means are used for the miniaturization design of turbofans, it will bring about problems such as high difficulty in structural design technology and low engine thrust-to-weight ratio.

[0004] On June 19, 2013, the Chinese invention patent with application number 201310048204.8 and invention name "Single-rotor micro-turbofan engine with axial-flow oblique-flow tandem compound compression system" disclosed a compound compression system for a micro-turbofan engine, in which the axial-flow fan rotor and the oblique-flow compressor rotor are arranged in tandem, and the intermediate casing is arranged behind the axial-flow rotor, dividing the axial-flow rotor outlet airflow into two. Compared with the conventional design, it omits the axial-flow stator and transition section, shortens the axial length of the system, and simplifies the system structure. However, there is no transition section between the axial-flow rotor and the oblique-flow rotor, and the inlet and outlet height difference of the oblique-flow rotor is limited under the same outer diameter; there is no stator between the axial-flow rotor and the oblique-flow rotor to twist the airflow into the axial direction, and the incoming flow of the oblique-flow rotor has a large positive pre-swirl. The above two factors make it difficult to improve the pressure ratio of the oblique-flow rotor, and it is impossible to achieve the two-stage pressure ratio of the conventional design. In addition, the patent does not provide any specific explanation of the design of the outer duct diffuser blades. The airflow in the outer duct diffuser is subject to dual loads in the radial and circumferential directions, and conventional designs will produce greater flow separation.

[0005] On June 13, 2017, a Chinese invention patent with application number 201710100868.2 and invention name "dual pressure ratio centrifugal compressor" disclosed a dual pressure ratio compression system for a micro-sized turbofan engine. This patent uses a stepped outlet with high and low blades to achieve dual pressure ratio compression of the inner and outer ducts, and the impeller is an integral wheel. Similar to the patent with application number 201310048204.8, the internal pressure ratio of this configuration is limited to the range that can be achieved by a single-stage diagonal flow impeller, and the mass of the integral wheel is relatively large. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a radial flow passage for a compact double-duct compression system which has a simple and compact structure and can effectively reduce fuel consumption while maintaining a thrust-to-weight ratio.

[0007] In order to solve the above technical problems, the present invention provides a compact dual-duct compression system with a meridian flow passage, including a fan rotor, wherein the upper half of the fan rotor outlet is connected to the outer duct flow passage, and the lower half is connected to the inner duct flow passage, so as to realize dual-duct compression;

[0008] The inner flow passage comprises an inner flow passage transition section diffuser, an oblique flow compressor rotor and an oblique flow compressor diffuser;

[0009] The inner channel transition section diffuser is connected to the lower half of the fan rotor outlet;

[0010] The oblique flow compressor rotor is connected between the inner duct transition section diffuser and the oblique flow compressor diffuser.

[0011] The beneficial effects of the present invention are as follows: (1) the transition section between the fan rotor and the diagonal flow compressor rotor is combined into one, and the inner channel transition section diffuser serves as both a transition section and a diffuser, thereby reducing the axial length of the system and simplifying the system structure. The diffuser is combined with the outer channel flow channel to realize the dual pressure ratio compression function of the inner and outer channels of the turbofan engine; (2) the use of the inner channel transition section diffuser can reduce the inlet radius of the diagonal flow compressor rotor, and the airflow at the fan rotor outlet is further decelerated and diffused, and the airflow direction is deflected to the axial direction. The above two factors can greatly improve the working capacity of the diagonal flow compressor rotor, and the inner pressure ratio can be equivalent to the conventional axial flow + diagonal flow two-stage pressure ratio; (3) the inner pressure ratio of the present invention is equivalent to the existing conventional axial flow + diagonal flow two-stage pressure ratio, rather than being limited to the range that can be achieved by a single-stage diagonal flow impeller. In this way, under the premise that the existing structural framework of the turbojet engine platform remains unchanged, the engine fuel consumption rate can be reduced by more than 30% under ground standard atmospheric conditions, while ensuring that the thrust-to-weight ratio is equivalent to that of the original turbojet engine.

[0012] In the present invention, the fan rotor and the mixed flow compressor rotor are located on the same central axis.

[0013] In the present invention, the meridional flow channel of the inner channel transition section diffuser is S-shaped, and the flow channel curvature changes from negative to positive; the blade tip of the inner channel transition section diffuser blade is arranged in the negative curvature area, and the blade root is arranged in the positive curvature area, and the entire blade presents a large forward swept shape.

[0014] In the present invention, the ratio of the average radius difference ΔHin between the inlet and outlet of the meridional flow passage of the inner channel transition section diffuser to the axial length Lin is 0.24 to 0.28, which can effectively avoid the influence of airflow separation on the engine.

[0015] In the present invention, the inclined flow compressor rotor adopts an inlet swept design, and the inlet swept angle α is 5° to 10° to avoid being affected by non-uniform incoming flow.

[0016] In the present invention, the outer duct flow passage includes an outer duct front diffuser and an outer duct rear diffuser which are connected to each other; the outer duct front diffuser is connected to the upper half of the fan rotor outlet.

[0017] In the present invention, the outer duct flow channel is S-shaped as a whole, and the flow channel curvature changes from positive to negative; the outer duct front diffuser blades are arranged in the positive curvature area, and the outer duct rear diffuser blades are arranged in the negative curvature area.

[0018] In the present invention, the outer duct front diffuser blades and the outer duct rear diffuser blades are straight-grained blades with independently designed root tip blade shapes to facilitate load control.

[0019] In the present invention, the outer duct front diffuser blade is designed with a strong root, and the blade tip inlet and outlet angle difference is 0°~10°; the outer duct rear diffuser blade is designed with a strong tip, and the blade root inlet and outlet angle difference is 0°~10°.

[0020] In the present invention, the ratio of the average radius difference ΔHout of the meridional flow passage from the inlet of the outer duct front diffuser to the outlet of the outer duct rear diffuser to the axial length Lout is between 0.38 and 0.42. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the structure of the meridian flow channel for the compact double-duct compression system;

[0023] Figure 2It is a schematic diagram of the positive and negative distribution areas of the curvature of the diffuser flow channel in the inner channel transition section, as well as the difference in average radius between the inlet and outlet ΔHin and the axial length dimension Lin;

[0024] Figure 3 It is a schematic diagram of the positive and negative distribution areas of the curvature of the duct composed of the duct front diffuser and the duct rear diffuser, as well as the inlet and outlet average radius difference ΔHout and the axial length dimension Lout;

[0025] Figure 4 Schematic diagrams of blade profiles of the 4 blades of the outer duct front diffuser and the 5 blades of the outer duct rear diffuser in each section, (a) is the blade profile of the outer duct front diffuser at the root tip, (b) is the blade profile of the outer duct rear diffuser at the root tip;

[0026] Figure 5 Schematic diagram of the inlet sweep angle α of the inclined flow compressor rotor 6.

[0027] In the figure, 1-fan rotor, 2-intermediate casing, 3-inner duct transition section diffuser, 4-outer duct front diffuser, 5-outer duct rear diffuser, 6-oblique flow compressor rotor, 7-oblique flow compressor diffuser. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0031] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0032] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0033] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0035] like Figure 1 As shown, the compact dual-duct compression system meridian flow channel shape provided in this embodiment includes a fan rotor 1, an intermediate casing 2, an inner duct transition section diffuser 3, an outer duct front diffuser 4, an outer duct rear diffuser 5, an oblique flow compressor rotor 6 and an oblique flow compressor diffuser 7. The outlet of the fan rotor 1 is divided into two by the intermediate casing 2, and the upper half is connected with the outer duct front diffuser 4 and the outer duct rear diffuser 5 in sequence to form the outer duct flow channel. The lower half of the fan rotor 1 outlet is connected with the inner duct transition section diffuser 3, the oblique flow compressor rotor 6, and the oblique flow compressor diffuser 7 in sequence to form the inner duct flow channel, thereby realizing dual duct compression. The oblique flow compressor rotor 6 is located between the inner duct transition section diffuser 3 and the oblique flow compressor diffuser 7.

[0036] In this embodiment, the fan rotor 1 and the inclined flow compressor rotor 6 are located on the same central axis, and the diffuser 3 in the inner channel transition section between the two acts as a transition section on the one hand to achieve a smooth transition of the flow channel; on the other hand, it also acts as a diffuser to decelerate and diffuse the airflow at the outlet of the fan rotor 1 and deflect the airflow direction to the axial direction.

[0037] In this embodiment, the diffuser 3 of the inner channel transition section is different from the conventional axial flow stator: in the radial direction, the curvature of the flow channel changes greatly. In order to avoid separation, the airflow should have a pressure difference pointing to the center of the circle to resist the centrifugal force; in the circumferential direction, the airflow needs to be twisted from a certain tangential angle to the axial direction, and there should also be a pressure difference pointing to the center of the circle to resist the centrifugal force. The existing conventional design can provide the required pressure difference in the circumferential direction by twisting the blades, but cannot provide the required pressure difference in the radial direction. Therefore, this embodiment makes the following further limitations on the design of the diffuser 3 of the inner channel transition section, as shown in the attached figure. Figure 1 and 2 As shown:

[0038] Define the positive and negative curvature of the flow channel. In this embodiment, the positive and negative curvature are defined as follows: along the flow direction, if the curve is concave, the curvature is positive, and if the curve is convex, the curvature is negative. According to the curvature distribution of the flow channel of the diffuser 3 in the inner channel transition section, the flow channel is divided into a positive curvature area and a negative curvature area. According to the position of the center of the circle, in the negative curvature area, the direction of the fluid pressure difference should point to the hub; in the positive curvature area, the direction of the fluid pressure difference should point to the hub. Therefore, the meridian flow channel of the diffuser 3 in the inner channel transition section is S-shaped, and the flow channel curvature changes from negative to positive. The blade tip (at the wheel rim) is arranged in the negative curvature area, and the blade root (at the wheel hub) is arranged in the positive curvature area, and the entire blade presents a large forward swept shape.

[0039] In the radial direction, the negative curvature area has a pressure difference pointing to the hub because the blades in the upper part slow down and expand the gas, and the positive curvature area has a pressure difference pointing to the rim because the blades in the lower part slow down and expand the gas. In this way, the swept design of the blades makes the airflow obtain a pressure difference in the radial direction, avoiding airflow separation.

[0040] At the same time, due to the limited pressure change in the radial direction caused by the blade sweep design, airflow separation cannot be avoided under large curvatures. Therefore, this embodiment limits the ratio of the geometric parameter of the flow channel - the average radius difference ΔHin and the axial length Lin. The larger the ratio, the better it is to shorten the axial length, but the curvature is large and the flow is difficult to control; on the contrary, the smaller the curvature, the easier it is to control the flow, but the axial length is large. Therefore, taking into account the axial length and curvature, the ratio is limited to between 0.24 and 0.28. The ratio in this embodiment is 0.27.

[0041] like Figure 1 and 5As shown, unlike conventional axial flow stators, the outlet flow of the diffuser 3 in the inner channel transition section is more complicated and has greater non-uniformity. The non-uniform incoming flow will have a greater impact on the downstream. The tip area is more sensitive to the uniformity of the airflow due to the high relative Mach number. For this reason, the inclined flow compressor rotor 6 adopts a swept design to increase the mixing length of the outlet airflow in the tip area of ​​the diffuser 3 in the inner channel transition section, while taking into account the work done by the inclined flow compressor rotor 6. The sweep angle should not be too large. The limited sweep angle range is determined by taking into account the uniformity of the incoming flow and the work capacity of the impeller. The sweep angle is usually limited to 5°~10°. In this embodiment, the sweep angle is 7°. The specific sweep angle parameters are shown in the attached figure. Figure 5 It should be noted that the larger the backsweep, the longer the airflow mixing length and the more uniform the incoming flow, but the larger the backsweep, the smaller the impeller blade size and the lower the work capacity.

[0042] Similarly, the curvature changes in the radial direction and the circumferential direction also exist in the airflow of the outer duct. Unlike the inner duct, the outer duct is slender and cannot arrange the blade tip and blade root in the negative curvature area and the positive curvature area respectively like the diffuser 3 of the inner duct transition section. Therefore, for the outer duct, a split design is adopted, which is respectively the outer duct front diffuser 4 and the outer duct rear diffuser 5. The outer duct flow channel composed of the outer duct front diffuser 4 and the outer duct rear diffuser 5 is S-shaped as a whole, and the flow channel curvature changes from positive to negative, as shown in the attached figure. Figure 1 and 3 shown.

[0043] First, according to the definition in the previous article, the flow channel is divided into a positive curvature zone and a negative curvature zone, and blades are set in the two zones respectively. The diffuser 4 in front of the outer duct is in the positive curvature zone, and the diffuser 5 after the outer duct is in the negative curvature zone. In order to facilitate load control, the diffuser blades are all straight-grained blades with independently designed root tip blades. Generally, the airflow is not easy to separate in the concave parts of the flow channel wall profile, while it is easy to separate in the convex parts; therefore, a large load is used in the concave area, that is, the difference in the inlet and outlet angles of the blade is large, so that the airflow is fully decelerated and diffused; a small load is used in the convex area, and the difference in the inlet and outlet angles of the blade is small to avoid large flow separation. As shown in the attached figure Figure 1 and 4 As shown, in the positive curvature area, the front diffuser 4 of the outer duct is designed with a strong root, and the load of the blade of the front diffuser 4 of the outer duct is mainly concentrated at the blade root, that is, the difference in the inlet and outlet angles of the blade tip is small, usually 0°~10°, and the difference in the inlet and outlet angles of the blade root is large; in the negative curvature area, on the contrary, the rear diffuser 5 of the outer duct is designed with a strong tip, and the main diffusion load of the blade of the rear diffuser 5 of the outer duct is concentrated at the blade tip, that is, the difference in the inlet and outlet angles of the blade root is small, usually 0°~10°, and the difference in the inlet and outlet angles of the blade tip is large. That is, in the outer duct, the pressure difference of the airflow in the radial direction is achieved through the root tip load distribution.

[0044] like Figure 1 and 3As shown, taking the axial length and curvature into comprehensive consideration, the ratio of the average inlet and outlet radius difference ΔHout of the duct composed of the duct front diffuser 4 and the duct rear diffuser 5 to the axial length Lout is limited to be between 0.38 and 0.42.

[0045] In this embodiment, the transition section between the fan rotor 1 and the diagonal flow compressor rotor 6 is combined into one. The internal transition section diffuser 3 acts as both a transition section and a diffuser, thereby reducing the axial length of the system and simplifying the system structure. The addition of the internal transition section diffuser 3 reduces the inlet radius of the diagonal flow compressor rotor 6, and the outlet airflow of the fan rotor 1 is further decelerated and diffused, and the airflow direction is deflected to the axial direction, thereby greatly improving the working capacity of the diagonal flow compressor rotor 6, and the internal pressure ratio can be equivalent to the two-stage pressure ratio of conventional axial flow + diagonal flow.

[0046] This embodiment adopts a simple and compact meridian flow channel form to realize the dual pressure ratio compression function of the inner and outer ducts of the turbofan engine. Under the premise that the existing structural framework of the turbojet engine platform remains unchanged, the inner pressure can be comparable to the pressure ratio of the conventional axial flow + oblique flow two stages, rather than being limited to the range that can be achieved by a single-stage oblique flow impeller. By adopting the present invention for turbofanization modification, the engine fuel consumption rate can be reduced by more than 30% under standard ground atmospheric conditions, and the thrust-to-weight ratio can be comparable to that of the original turbojet engine.

[0047] The present invention provides a concept of a compact dual-duct compression system with a meridian flow channel. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention. All components not specified in this embodiment can be implemented using existing technologies.

Claims

1. A compact double-duct compression system with a meridian flow passage, comprising a fan rotor, characterized in that: The upper part of the fan rotor outlet is connected to the outer flow channel, and the lower part is connected to the inner flow channel; The inner flow passage comprises an inner flow passage transition section diffuser, an oblique flow compressor rotor and an oblique flow compressor diffuser; The inner channel transition section diffuser is connected to the lower half of the fan rotor outlet; The diagonal flow compressor rotor is connected between the inner duct transition section diffuser and the diagonal flow compressor diffuser; The meridional flow channel of the diffuser in the inner channel transition section is S-shaped, and the flow channel curvature changes from negative to positive; along the flow path direction, the curvature is positive when the curve is concave, and negative when the curve is convex; The blade tip of the diffuser blade in the inner channel transition section is arranged in the negative curvature area, and the blade root is arranged in the positive curvature area, and the entire blade presents a large forward swept shape.

2. The meridian flow passage for a compact double-duct compression system according to claim 1, characterized in that: The ratio of the average radius difference ΔHin between the inlet and outlet of the meridional flow channel of the inner channel transition section diffuser to the axial length Lin is 0.24-0.

28.

3. The meridian flow passage for a compact double-duct compression system according to claim 1, characterized in that: The inclined flow compressor rotor adopts an inlet swept design, and the inlet swept angle α is 5°~10°.

4. The meridian flow passage for a compact double-duct compression system according to claim 1, characterized in that: The fan rotor and the diagonal flow compressor rotor are located on the same central axis.

5. The meridian flow passage for a compact double-duct compression system according to claim 1, characterized in that: The duct includes a duct front diffuser and a duct rear diffuser connected to each other; The outer duct front diffuser is connected to the upper part of the fan rotor outlet.

6. The meridian flow passage for a compact double-duct compression system according to claim 5, characterized in that: The outer duct is generally S-shaped, and the curvature of the duct changes from positive to negative; The outer duct front diffuser blades are arranged in the positive curvature area, and the outer duct rear diffuser blades are arranged in the negative curvature area.

7. The meridian flow passage for a compact double-duct compression system according to claim 5, characterized in that: The outer duct front diffuser blades and the outer duct rear diffuser blades are straight-grained blades with independently designed root tip blade shapes.

8. The meridian flow passage for a compact double-duct compression system according to claim 7, characterized in that: The outer duct front diffuser blade is designed with a strong root, and the blade tip inlet and outlet angle difference is 0°~10°; The outer duct rear diffuser blade is designed with a strong tip, and the blade root inlet and outlet angle difference is 0°~10°.

9. The meridian flow passage for a compact double-duct compression system according to claim 5, characterized in that: The ratio of the average radius difference ΔHout between the inlet and outlet of the meridional flow passage from the inlet of the front diffuser of the outer duct to the outlet of the rear diffuser of the outer duct to the axial length Lout is between 0.38 and 0.42.

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