Double-duct axial flow-oblique flow combined compression system

Abstract

The invention discloses a double-duct axial flow-oblique flow combined compression system which is used for a power system of an unmanned aerial vehicle. According to the design of the small turbofan engine, a sunken transition section is arranged between an axial flow fan and an oblique flow impeller of the small turbofan engine, the radial size can be effectively reduced, and meanwhile the pressure ratio of an inner duct is effectively increased. By optimizing the structural design of the gas compressor, the thrust, efficiency and operation stability of the engine are improved, and meanwhile the weight and the occupied space are reduced. Compared with a microminiature turbojet engine, the microminiature turbofan engine has the advantages that the thrust is obviously increased and the oil consumption rate is obviously reduced under the condition that only a small amount of modification needs to be carried out on the structure. Therefore, a carrier applying the engine is remarkably improved in the aspect of voyage or load. The invention belongs to the technical field of microminiature turbine engines.

Description

Technical Field

[0001] The invention relates to the technical field of aeroengines, and in particular to a double-duct axial flow-oblique flow combined compression system. Background Art

[0002] In the late 20th century, with the rise of micro-mechanical technology (MEMS), the research on micro-turbofan engines gradually unfolded. In 1983, the British technical team, led by Jerry Jackman, successfully developed the world's first micro-turbojet engine, which laid an important foundation for the subsequent development of model aircraft enthusiasts and model aircraft. With the development of technology and the reduction of costs, micro-turbojet engines have gradually moved from the laboratory to the market and are widely used in the fields of model aircraft, drones, etc. With the continuous development of aviation technology, the performance requirements for aircraft engines are increasing. Due to size and structural limitations, the compressor of a micro-turbofan engine usually adopts a centrifugal or diagonal flow single-rotor design, which results in a relatively low boost ratio and low internal pressure. These factors directly affect key performance indicators such as thrust-to-weight ratio and fuel consumption rate, making it difficult for micro-fan jet engines to compete with large engines in terms of performance.

[0003] For example, the patent "Single-rotor micro-turbofan engine with axial-flow oblique flow tandem compression system" (CN201310048204.8) describes a composite compression system for a micro-turbofan engine, in which the axial-flow fan rotor and the oblique-flow compressor rotor are arranged in series, 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, the axial-flow fan stator and transition section are omitted in the inner channel, shortening the axial length of the system and simplifying the system structure. However, there is no transition section between the axial-flow fan rotor and the inner channel 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 fan 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 the inner channel pressure ratio is limited to the pressure ratio range that can be achieved by a single-stage oblique flow. Therefore, the fuel consumption rate of the engine has no obvious advantage over the turbojet engine.

[0004] On June 10, 2023, the application number is 202211109313.1, and the invention name is Compact Dual-Channel Compression System. It publicly invented a compact dual-duct compression system, which combines the transition section between the fan rotor and the oblique flow compressor rotor into one. The diffuser of the inner duct transition section 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 channel to realize the function of dual pressure ratio compression of the inner and outer ducts of the turbofan engine. However, the flow at the outlet of the inner duct transition section diffuser is relatively complex and has large non-uniformity. The non-uniform incoming flow will have a greater impact on the downstream. Due to the high relative Mach number, the tip area is more sensitive to the uniformity of the airflow. In addition, the swept design is adopted for the oblique flow compressor rotor matched after the inner duct diffuser. Although the mixing length of the outlet airflow in the tip area of ​​the inner duct transition section diffuser is increased, the increased swept back will lead to a reduction in the size of the impeller blades and a decrease in the work capacity. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a double-duct axial flow-oblique flow combined compression system in view of the defects involved in the background technology.

[0006] The present invention adopts the following technical solutions to solve the above technical problems: A double-duct axial flow-oblique flow combined compression system, comprising a meridian flow passage, an axial flow compressor, an intermediate casing, an oblique flow impeller and a diffuser; The axial flow compressor is arranged in the meridian flow passage; The intermediate casing is arranged in the meridian flow passage located downstream of the axial flow compressor, and an outer duct is formed between its outer wall surface and the outer wall of the meridian flow passage, and an inner duct is formed between its inner wall surface and the inner wall of the meridian flow passage; the upstream of the intermediate casing is located at the outlet end of the axial flow compressor, so that the airflow at the outlet of the axial flow compressor is divided into two, one part flows into the outer duct, and the other part flows into the inner duct; The inner channel includes a transition section, an oblique flow section and a diffuser section from upstream to downstream; The oblique flow impeller is arranged in the oblique flow section and is located on the same central axis as the axial flow compressor; The diffuser is arranged in the diffuser section; The outer diameter of the downstream end of the outer wall of the meridian flow channel and the intermediate casing is larger than the outer diameter of the upstream end, and is S-shaped; the inner channel bends inwardly at the transition section and the oblique flow section.

[0007] As a further optimization solution for the dual-duct axial flow-oblique flow combined compression system of the present invention, the diffuser is a conformal channel diffuser.

[0008] As a further optimization solution of the double-duct axial flow-oblique flow combined compression system of the present invention, the axial flow compressor adopts a constant outer diameter design.

[0009] As a further optimization scheme of the double-duct axial flow-oblique flow combined compression system of the present invention, the median angle of the transition section does not exceed 35°.

[0010] As a further optimization scheme of a double-duct axial flow-oblique flow combined compression system of the present invention, the ratio of the average radius difference between the inlet and outlet of the meridian flow channel and the axial length of the transition section is 0.44~0.48 to avoid the influence of airflow separation on the engine.

[0011] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects: 1. By adding a sunken transition section between the axial flow fan and the diagonal flow compressor rotor, the radial length of the system is controlled, the inlet and outlet height difference of the diagonal flow rotor is increased, the system structure is simplified, and the working capacity of the diagonal flow rotor is increased; 2. The present invention selects a diagonal flow compressor and a conformal channel diffuser as the compressor form that matches the axial flow fan, which has advantages in improving the flow efficiency of the inner and outer ducts, and helps to improve the unit windward surface thrust, and is equivalent to the pressure ratio of the existing conventional axial flow + diagonal flow two-stage, rather than being limited to the range that can be achieved by a single-stage diagonal flow impeller; 3. The external airflow increases the total exhaust flow of the engine, and the available energy of the engine is distributed to a larger exhaust flow. The reduction in exhaust velocity is smaller than the increase in mass, so the total momentum of the exhaust increases. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the structure of a double-duct axial flow-oblique flow combined compression system; Figure 2 Schematic diagram of the relationship between the average radius difference ΔH between the inlet and outlet of the meridian flow channel and the axial length L of the transition section.

[0013] In the figure, 1-outer wall of the meridian flow channel, 2-inner wall of the meridian flow channel, 3-axial flow compressor, 4-mid-boundary casing, 5-transition section, 6-oblique flow section, 7-diffuser. DETAILED DESCRIPTION

[0014] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings: The present invention can be implemented in many different forms and should not be considered to be limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete, and will fully express the scope of the present invention to those skilled in the art. In the accompanying drawings, components are enlarged for clarity.

[0015] It should be understood that although the terms first, second, third, etc. can be used here to describe various elements, components and / or parts, these elements, components and / or parts are not limited by these terms. These terms are only used to distinguish elements, components and / or parts from each other. Therefore, the first element, component and / or part discussed below can become the second element, component or part without departing from the teaching of the present invention.

[0016] like Figure 1 As shown, the present invention discloses a double-duct axial flow-oblique flow combined compression system, including a meridian flow passage, an axial flow compressor, an intermediate casing, an oblique flow impeller and a diffuser; The axial flow compressor is arranged in the meridian flow passage; The intermediate casing is arranged in the meridian flow passage located downstream of the axial flow compressor, and an outer duct is formed between its outer wall surface and the outer wall of the meridian flow passage, and an inner duct is formed between its inner wall surface and the inner wall of the meridian flow passage; the upstream of the intermediate casing is located at the outlet end of the axial flow compressor, so that the airflow at the outlet of the axial flow compressor is divided into two, one part flows into the outer duct, and the other part flows into the inner duct; The inner channel includes a transition section, an oblique flow section and a diffuser section from upstream to downstream; The oblique flow impeller is arranged in the oblique flow section and is located on the same central axis as the axial flow compressor; The diffuser is arranged in the diffuser section; The outer diameter of the downstream end of the outer wall of the meridian flow channel and the intermediate casing is larger than the outer diameter of the upstream end, and is S-shaped; the inner channel bends inwardly at the transition section and the oblique flow section.

[0017] The diffuser is preferably a conformal channel diffuser, and the axial flow compressor is preferably designed with a constant outer diameter.

[0018] The median angle of the transition section does not exceed 35°. The ratio of the average radius difference between the inlet and outlet of the meridian flow channel and the axial length of the transition section is 0.44-0.48 to avoid the influence of airflow separation on the engine. In this embodiment, the axial flow compressor 3 and the oblique flow compressor impeller 6 are located on the same central axis.

[0019] The inner duct of the present invention includes a transition section, an oblique flow section and a diffuser section, and an axial flow fan is in the main channel. A section of a novel downward-sinking curved pipe is used to connect the axial flow fan and the oblique flow compressor. When the compressor is working, the airflow is introduced into the first-stage axial flow compressor of the main channel, and after being pressurized by the working blades, it flows into the outer duct through the intermediate casing to provide additional air for the core engine, and the inner duct enters the oblique flow impeller of the second-stage oblique flow compressor through a downward-sinking transition section, and after being further pressurized by the oblique flow impeller, it enters the conformal channel diffuser, where it is decelerated and pressurized, and finally flows into the combustion chamber.

[0020] In this embodiment, the axial flow fan section adopts a flow channel design with equal outer diameter, so that the tip speed of each stage is increased, the power added by the last stage blade is increased, and the number of stages is reduced.

[0021] In this embodiment, the outlet diameter of the oblique flow impeller is 292 mm, the impeller inlet / outlet diameter ratio ranges from 0.5 to 0.7, and the ratio of width to outer diameter is from 0.23 to 0.26. The diffuser matched therewith adopts a conformal channel diffuser with an oblique flow inlet.

[0022] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0023] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A double-ducted axial flow-oblique flow combined compression system, characterized in that: It includes a meridian flow passage, an axial flow compressor, an intermediate casing, a diagonal flow impeller and a diffuser; The axial flow compressor is arranged in the meridian flow passage; The intermediate casing is arranged in the meridian flow passage located downstream of the axial flow compressor, and an outer duct is formed between its outer wall surface and the outer wall of the meridian flow passage, and an inner duct is formed between its inner wall surface and the inner wall of the meridian flow passage; the upstream of the intermediate casing is located at the outlet end of the axial flow compressor, so that the airflow at the outlet of the axial flow compressor is divided into two, one part flows into the outer duct, and the other part flows into the inner duct; The inner channel includes a transition section, an oblique flow section and a diffuser section from upstream to downstream; The oblique flow impeller is arranged in the oblique flow section and is located on the same central axis as the axial flow compressor; The diffuser is arranged in the diffuser section; The outer diameter of the downstream end of the outer wall of the meridian flow channel and the intermediate casing is larger than the outer diameter of the upstream end, and is S-shaped; the inner channel bends inwardly at the transition section and the oblique flow section.

2. The double-ducted axial flow-oblique flow combined compression system according to claim 1 is characterized in that: The diffuser is a conformal channel diffuser.

3. The double-ducted axial flow-oblique flow combined compression system according to claim 1, characterized in that: The axial flow compressor adopts a constant outer diameter design.

4. The double-ducted axial flow-oblique flow combined compression system according to claim 1, characterized in that: The median angle of the transition section does not exceed 35°.

5. The double-ducted axial flow-oblique flow combined compression system according to claim 1, characterized in that: The ratio of the average radius difference between the inlet and outlet of the meridian flow channel and the axial length of the transition section is 0.44-0.48, so as to avoid the influence of airflow separation on the engine.

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