High-efficiency cooling turbine structure and guide for micro-turbine engine

Abstract

The present invention discloses a micro-turbine engine high-efficiency cooling turbine structure and guide, belonging to the field of aviation engines. It includes a flame tube and a guide, the guide is located at the rear of the flame tube, a plurality of blades are arranged on the guide, and a plurality of blade cooling channels are arranged in each of the blades; the blade cooling channel is connected to the main cooling channel, and the cooling gas enters the blade cooling channel from the main cooling channel to cool the guide and then enters the annular cavity inside the guide; the lower part of the annular cavity is connected to the auxiliary cooling channel, and the auxiliary cooling channel is used to input low-temperature and high-pressure gas into the annular cavity; the rear part of the annular cavity is connected to the exhaust channel. Through the design of the main cooling channel combined with the auxiliary cooling channel, the main cooling channel is used to cool the guide and increase the temperature before the turbine, and the auxiliary cooling channel is used to prevent the gas in the main cooling channel from flowing back into the bearing cavity of the engine.

Description

Technical Field

[0001] The invention relates to a turbine cooling structure, in particular to a high-efficiency cooling turbine structure and a guide for a micro-sized turbine engine, belonging to the field of aviation engines. Background Art

[0002] Powder starting is one of the main starting methods for micro-turbine engines. It has many advantages such as fast starting and reliable process, and is widely used in military and other related fields. Powder starting refers to the process of using a powder starter to generate high-temperature and high-pressure gas, which impacts the compressor or turbine blades to drive the rotor to rotate, thereby completing the process of engine ignition and starting. Due to the problem of gunpowder residue, micro-turbine engines using powder starting often use channels without cooling or with large inlet and outlet areas to cool the turbine. In actual operation, excessive cooling bleed air will cause the engine thrust to decrease. In order to ensure engine performance and reduce the amount of bleed air, the inlet and outlet pressure difference of the cooling flow channel is low, resulting in a low air flow velocity and a low convective heat transfer coefficient in the cooling channel, resulting in limited cooling effect. Under the constraints of the cooling effect, the engine's turbine inlet temperature is difficult to be significantly increased, which in turn limits the engine's performance improvement. In order to further improve the engine performance while ensuring the reliability of the powder starting function, more effective and reliable cooling measures are needed to increase the engine turbine inlet temperature.

[0003] Most micro-turbine engines have integral turbines and guide vanes, which are limited by the channel size and make it difficult to use cooling solutions such as spoiler columns and impact air films. In addition, small turbine engines are mostly used in short-life unmanned aerial vehicles, which puts more stringent requirements on engine cost control. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a micro-turbine engine with an efficient cooling turbine structure and guide vane, which can effectively reduce the leading edge temperature of the guide vane without significantly affecting the engine thrust, thereby increasing the temperature before the turbine by a corresponding amount, greatly increasing the overall thermal cycle efficiency of the engine and improving the engine thrust performance.

[0005] In order to solve the above technical problems, the present invention provides a micro-turbine engine high-efficiency cooling turbine structure, comprising a flame tube and a guide, wherein the guide is located behind the flame tube, a plurality of blades are arranged on the guide, and a plurality of blade cooling channels are arranged in each of the blades; The blade cooling channel is connected to the main cooling channel, and the cooling gas enters the blade cooling channel from the main cooling channel to cool the guide and then enters the annular cavity inside the guide; The lower part of the annular cavity is connected to an auxiliary cooling channel, and the auxiliary cooling channel is used to input low-temperature and high-pressure gas into the annular cavity; The rear portion of the annular cavity is connected to the exhaust passage.

[0006] In the present invention, the blade cooling channel is a wedge-shaped structure.

[0007] In the present invention, the blade cooling channel includes an inlet section, a middle section and an outlet section, wherein the inlet section is located at the tip of the blade and the outlet section is located at the root of the blade; The distances t between the inlet section, the middle section and the outlet section and the blade surface are equal; the outer side shape line of the middle section is kept vertical, and the inner side shape line is inclined outward.

[0008] In the present invention, the blade includes a pressure surface and a suction surface, and the distribution density of the blade cooling flow channel close to the pressure surface is greater than that of the blade cooling flow channel close to the suction surface.

[0009] In the present invention, the exhaust channel includes a first exhaust channel and a second exhaust channel; The outlet of the first exhaust passage is located at the lower middle part of the front disk of the turbine rotor; The outlet of the second exhaust passage is located on the rear disk surface of the turbine rotor.

[0010] In the present invention, the inlets of the main cooling channel and the auxiliary cooling channel, and the outlets of the first exhaust channel and the second exhaust channel are all far away from the mainstream area.

[0011] In the present invention, the pressure of the main cooling channel is the same as that of the auxiliary cooling channel, or the pressure of the main cooling channel is slightly lower than that of the auxiliary cooling channel.

[0012] The present invention also provides a guide, characterized in that it comprises a plurality of circumferentially spaced blades, each of the blades is provided with a plurality of blade cooling channels, and the blade cooling channels are wedge-shaped structures.

[0013] In the present invention, the blade cooling channel includes an inlet section, a middle section and an outlet section, wherein the inlet section is located at the tip of the blade and the outlet section is located at the root of the blade; The distances t between the inlet section, the middle section and the outlet section and the blade surface are equal; the outer side shape line of the middle section is kept vertical, and the inner side shape line is inclined outward.

[0014] In the present invention, the blade includes a pressure surface and a suction surface, and the distribution density of the blade cooling flow channel close to the pressure surface is greater than that of the blade cooling flow channel close to the suction surface.

[0015] The beneficial effects of the present invention are as follows: (1) through the design of combining the main cooling channel with the auxiliary cooling channel, the main cooling channel is used to cool the guide vane and increase the temperature before the turbine, and the auxiliary cooling channel is used to prevent the air in the main cooling channel from flowing back into the bearing cavity of the engine; through the small area of ​​multiple exhaust channels, a balance between the amount of cooling air and the cooling effect is achieved. Under the premise that the amount of bleed air only accounts for 1% of the total flow and has no obvious effect on the engine thrust, the maximum temperature of the leading edge of the guide vane can be reduced by more than 100K compared with no cooling, thereby increasing the temperature before the turbine by a corresponding amount, greatly increasing the overall thermal cycle efficiency of the engine and improving the engine thrust performance; (2) The blade cooling flow channel is a wedge-shaped structure, and the cross-section of the wedge-shaped channel is arranged according to the inlet and outlet conditions of the cooling channel and the radial temperature distribution of the airflow, so as to carry out targeted cooling of the guide vane. To reduce the temperature gradient on the blade surface, thereby reducing the thermal stress of the guide; and the blade cooling channel is a straight-through type, which has a simple structure and a high yield rate, and can greatly reduce the production cost of the product; (3) The blade cooling channel is provided with a small straight section near the inlet and outlet to ensure good forming processability; (4) The distribution density of the blade cooling channel on the blade is greater than the distribution density on the suction surface, which is beneficial to reduce the temperature gradient from the pressure surface to the suction surface, thereby reducing thermal stress; (5) The inlet of the cooling channel and the auxiliary cooling channel, and the outlet of the first exhaust channel and the second exhaust channel are all far away from the mainstream area. By designing the air system away from the mainstream area, it can effectively avoid being contaminated by gunpowder residue, thereby improving the anti-pollution ability of the cooling channel to meet the gunpowder starting requirements of micro-turbine engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] Figure 1 Schematic diagram of turbine structure for efficient cooling of micro turbine engine; Figure 2 This is the overall structure diagram of the guide; Figure 3 This is a schematic diagram of the cooling channel of the guide vane; Figure 4 Schematic diagram of the channel distribution on the pressure and suction surfaces of the guide vane.

[0018] In the figure, 1-flame tube, 2-combustion chamber casing, 3-main stream channel, 4-main cooling channel, 5-guide, 6-annular cavity, 7-turbine nut, 8-main shaft, 9-second exhaust channel, 10-turbine rotor, 11-first exhaust channel, 12-bushing, 13-bearing, 14-auxiliary cooling channel, 51-blade, 52-blade center, 53-blade tip, 54-blade root, 55-blade cooling channel, 511-blade surface, 512-pressure surface, 513-suction surface, 551-inlet section, 552-middle section, 553-exit section. DETAILED DESCRIPTION

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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 the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0026] like Figure 1 As shown, the micro-turbine engine high-efficiency cooling turbine structure provided in this embodiment includes a flame tube 1, a combustion chamber casing 2, a guide 5, a turbine nut 7, a main shaft 8, a turbine rotor 10, a bushing 12 and a bearing 13. Among them, the flame tube 1 is located in the combustion chamber casing 2, and a mainstream channel 3 is formed in the flame tube 1. The guide 5 is installed on the rear side of the flame tube 1, and a main cooling channel 4 is formed between the flame tube 1 and the combustion chamber casing 2, which can transport cooling gas to the guide 5.

[0027] The bearing 13 , the bushing 12 , the turbine rotor 10 , and the turbine nut 7 are assembled on the main shaft 8 in sequence, and the guide 5 is located at the front side of the turbine rotor 10 .

[0028] like Figure 1 and 2 As shown, the outer side of the guide 5 is connected to the main cooling channel 4, and the inner side is the annular cavity 6; the inlet of the main cooling channel 4 is arranged in the stagnation zone between the guide 5 and the combustion chamber casing 2. The guide 5 includes a plurality of blades 51 spaced apart along the circumferential direction, and each blade 51 is provided with a plurality of blade cooling channels 55 spaced apart. When the engine is working normally, the cooling air enters from the main cooling channel 4, cools the blades 51 of the guide 5 through the blade cooling channels 55, and then reaches the annular cavity 6 from the upper part of the annular cavity 6.

[0029] The inlet of the auxiliary cooling channel 14 is arranged on the bushing 12, and the outlet of the auxiliary cooling channel 14 is connected to the lower part of the annular cavity 6. In this embodiment, the auxiliary cooling channel 14 introduces low-temperature high-pressure air, so that the high-temperature air that has cooled the blades 51 flows downstream to prevent the high-temperature air from flowing back to the bearing 13.

[0030] The rear side of the annular cavity 6 is connected to the first exhaust channel 11 and the second exhaust channel 9 respectively, and the cooled gas flows out from the first exhaust channel 11 in one way and from the second exhaust channel 9 in the other way. The first exhaust channel 11 is located in the middle and lower part of the front disk of the turbine rotor 10. In this embodiment, the first exhaust channel 11 is the gap between the guide 5 and the turbine rotor 10. It is not limited to this in the implementation process, and the first exhaust channel 11 can also be formed by the gap between any stator and rotor.

[0031] The second exhaust channel 9 is located on the rear disk of the turbine rotor 10, and the second exhaust channel 9 is connected to the lower part of the annular cavity 6. In actual application, the second exhaust channel 9 can also be removed when the stress of the main shaft 8 and the turbine rotor 10 meets the conditions. If the stress of the main shaft 8 or the turbine rotor 10 is too large, the flow direction and outlet angle of the second exhaust channel 9 can be adjusted in a targeted manner so that the cooling gas flowing out of the second exhaust channel 9 can cool the main shaft 8 or the turbine rotor 10 to reduce its thermal stress.

[0032] In the gunpowder starting mode, since there is a large amount of gunpowder residue in the mainstream channel 3 when the engine starts, in order to prevent the gunpowder residue from contaminating the cooling channels and the exhaust channels, in this embodiment, the inlet of the main cooling channel 4 and the inlet of the auxiliary cooling channel 14, the outlet of the first exhaust channel 11 and the outlet of the second exhaust channel 9 are all far away from the mainstream channel 3, which can effectively prevent the cooling channels and the exhaust channels from being contaminated by gunpowder residue and meet the gunpowder starting requirements of the micro-turbine engine.

[0033] like Figure 3 As shown, in this embodiment, the blade cooling channel 55 includes an inlet section 551 (L1), a middle section 552 (L2), and an outlet section 553 (L3), and the three sections are at the same distance t from the blade surface 511. Among them, the middle section 552 is designed according to the minimum temperature gradient principle of the blade surface 511, and the inlet section 551 and the outlet section 553 can be removed or retained according to actual process conditions.

[0034] The design method of the side profile of the middle section 552 is as follows: the middle section 552 of the blade cooling channel 55 is wedge-shaped, and its outer side profile remains vertical, while the inner side profile is inclined outward, so that the cross-sectional area of ​​the flow channel of the middle section 552 gradually decreases from the blade tip 53 to the blade root 54; specifically, in terms of the cross-sectional shape, the length of the long side of the rectangular cross section remains unchanged, while the length of the short side gradually decreases from the blade tip 53 to the blade root 54. The above design is mainly adopted for the following considerations: Due to the structure of the flame tube 1 contracting inward, under the effect of the wall cooling airflow of the flame tube 1 of the combustion chamber, the airflow temperature at the outlet of the flame tube 1 presents a radial distribution law of low at both ends and high in the middle, and the highest temperature at the outlet of the combustion chamber is located at 1 / 3 of the blade height of the blade 51, close to the blade root 54; and in the process of the cooling airflow flowing from the inlet to the outlet of the cooling channel, the temperature of the airflow gradually increases and the cooling effect gradually decreases. The cooling effect at 1 / 3 of the blade height is poor, which is difficult to match the actual wall temperature distribution of the blade 51.

[0035] Due to the above reasons, the wall temperature near the blade root 54 is higher than that at the blade tip 53, and the convective heat transfer capacity is weaker than that at the blade tip 53. In this embodiment, the cross-sectional area of ​​the middle section 552 of the blade cooling channel 55 is designed to gradually decrease from the blade tip 53 to the blade root 54, which can increase the cooling air flow velocity near the blade root 54, improve the Reynolds number and the convective heat transfer coefficient, and thus effectively address the problem of excessively high wall temperature near the blade root 54. Keep the channel area unchanged at other positions, appropriately weaken the cooling effect, so as to reduce the temperature gradient along the radial direction of the blade surface 511, thereby reducing thermal stress.

[0036] The heat exchange between the middle section 552 of the blade cooling flow channel 55 and the blade 51 mainly occurs on the long side of the rectangular cross section. Therefore, the design method of keeping the long side length unchanged and reducing the short side length in this embodiment can reduce the flow channel cross-sectional area of ​​the middle section 552 and improve the convection heat transfer coefficient while ensuring that the effective convection heat transfer area remains unchanged, thereby increasing the convection heat transfer amount. The above design can effectively control the wall temperature near the blade root 54, thereby reducing the temperature gradient of the blade surface 511 along the blade height direction.

[0037] like Figure 4 As shown, in this embodiment, the blade surface 511 includes a pressure surface 512 and a suction surface 513. Since the airflow temperature of the pressure surface 512 of the blade 51 is higher than the temperature of the suction surface 513, the cooling area (the number of blade cooling channels 55) and the position distribution of the pressure surface 512 and the suction surface 513 in this embodiment are designed and arranged according to the principle of minimum pressure gradient along the thickness direction of the blade 51. The blade cooling channels 55 on the pressure surface 512 side are more densely distributed than the blade cooling channels 55 on the suction surface 513 side, so as to reduce the temperature gradient of the blade 51 along the thickness direction.

[0038] From the perspective of the hot air flow characteristics in the mainstream channel 3, the hot air flow velocity near the pressure surface 512 of the blade 51 is low, the pressure is high, the temperature of the air flow near the wall is high, and the cooling air demand is large; the hot air flow near the suction surface 513 is accelerated, the air flow velocity is high, the pressure is low, the temperature of the air flow near the wall is low, and the cooling air demand is small. Therefore, in this embodiment, the blade cooling flow channel 55 on the pressure surface 512 side is more dense, which helps to improve the cooling efficiency of the pressure surface 512 wall and reduce the wall temperature.

[0039] In this embodiment, the blade cooling channel 55 adopts a vertical straight-through structure, which has a simple structure and good processability, and can greatly improve the one-time forming qualification rate of the product and reduce the production cost.

[0040] Since multiple blade cooling channels 55 are arranged on a single blade 51, the channel cross-sectional area is small; at the same time, through the gap control of the first exhaust channel 11 and the second exhaust channel 9, the inlet and outlet pressure difference of the blade cooling channel 55 can be appropriately increased, thereby increasing the cooling air flow velocity and enhancing the convective heat exchange effect without increasing the air intake amount too much.

[0041] In this embodiment, when the engine is running normally, the cooling air of the main cooling channel 4 enters the wedge-shaped cooling channel from the guide 5, cools the turbine guide 5, and is discharged from the first exhaust channel 11 and the second exhaust channel 9 respectively; at the same time, high-pressure air enters from the auxiliary cooling channel 14 to prevent the backflow of high-pressure airflow. If necessary, the cooling air flowing out of the second exhaust channel 9 can also further cool the main shaft 8 or the turbine disk, thereby eliminating or reducing the thermal stress of the main shaft 8 and the turbine disk.

[0042] The cooling effect of the cooling air mainly comes from the convective heat transfer between the airflow and the hot wall. According to the existing formula for the convective heat transfer coefficient in the tube, the faster the flow rate of the cooling air in the channel, the stronger the corresponding cooling effect. On the other hand, in order to ensure that the engine thrust is not affected, the cooling air bleed volume cannot be too large. In order to increase the airflow velocity with a smaller bleed volume, the cooling flow channel is designed in a multi-channel, small cross-sectional area form, and the inlet and outlet pressure difference of the cooling flow channel is appropriately increased by controlling the exhaust channel gap to achieve a balance between the bleed volume and the cooling effect.

[0043] Through the design of the above cooling structure, this embodiment can ensure that the maximum temperature of the leading edge of the blade 51 in the guide vane 5 is reduced by more than 100K compared with no cooling, under the premise that the bleed air volume only accounts for 1% of the total flow rate and has no obvious effect on the engine thrust. As a result, the temperature before the turbine is increased by a corresponding amount, greatly increasing the overall thermal cycle efficiency of the engine and improving the engine thrust performance.

[0044] The present invention provides a concept for efficiently cooling the turbine structure and guide of a micro-turbine engine. 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 considered as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A micro-turbine engine with high efficiency cooling turbine structure, characterized by: It comprises a flame tube and a guide, wherein the guide is located at the rear of the flame tube, a plurality of blades are arranged on the guide, and a plurality of blade cooling channels are arranged in each of the blades; The blade cooling channel is connected to the main cooling channel, and the cooling gas enters the blade cooling channel from the main cooling channel to cool the guide and then enters the annular cavity inside the guide; The lower part of the annular cavity is connected to an auxiliary cooling channel, and the auxiliary cooling channel is used to input low-temperature and high-pressure gas into the annular cavity; The rear portion of the annular cavity is connected to the exhaust passage.

2. The micro-turbine engine high-efficiency cooling turbine structure according to claim 1 is characterized in that: The blade cooling channel is a wedge-shaped structure.

3. The micro-turbine engine high-efficiency cooling turbine structure according to claim 2 is characterized in that: The blade cooling channel includes an inlet section, a middle section and an outlet section, wherein the inlet section is located at the tip of the blade and the outlet section is located at the root of the blade; The distances t between the inlet section, the middle section and the outlet section and the blade surface are equal; the outer side shape line of the middle section is kept vertical, and the inner side shape line is inclined outward.

4. The micro-turbine engine high-efficiency cooling turbine structure according to any one of claims 1 to 3, characterized in that: The blade comprises a pressure surface and a suction surface, and the distribution density of the blade cooling flow channels close to the pressure surface is greater than that of the blade cooling flow channels close to the suction surface.

5. The micro-turbine engine high-efficiency cooling turbine structure according to any one of claims 1 to 3, characterized in that: The exhaust passage comprises a first exhaust passage and a second exhaust passage; The outlet of the first exhaust passage is located at the lower middle part of the front disk of the turbine rotor; The outlet of the second exhaust passage is located on the rear disk surface of the turbine rotor.

6. The micro-turbine engine high-efficiency cooling turbine structure according to claim 5, characterized in that: The inlets of the main cooling channel and the auxiliary cooling channel, and the outlets of the first exhaust channel and the second exhaust channel are all far away from the mainstream area.

7. The micro-turbine engine high-efficiency cooling turbine structure according to any one of claims 1 to 3, characterized in that: The pressure of the main cooling channel is the same as that of the auxiliary cooling channel, or the pressure of the main cooling channel is slightly lower than that of the auxiliary cooling channel.

8. A guide, characterized in that: Based on the micro-turbine engine efficient cooling turbine structure described in claim 1, the guide includes a plurality of circumferentially spaced blades, each of the blades is provided with a plurality of blade cooling channels, and the blade cooling channels are wedge-shaped structures.

9. The guide according to claim 8, characterized in that: The blade cooling channel includes an inlet section, a middle section and an outlet section, wherein the inlet section is located at the tip of the blade and the outlet section is located at the root of the blade; The distances t between the inlet section, the middle section and the outlet section and the blade surface are equal; the outer side shape line of the middle section is kept vertical, and the inner side shape line is inclined outward.

10. The guide according to claim 8 or 9, characterized in that: The blade comprises a pressure surface and a suction surface, and the distribution density of the blade cooling flow channels close to the pressure surface is greater than that of the blade cooling flow channels close to the suction surface.

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