Ladder type loop heat exchanger system for lubricating oil sealing air precooling

Abstract

This invention belongs to the field of aero-engines and provides a stepped annular heat exchange system for pre-cooling air used in lubricating oil sealing. The stepped annular heat exchange system is located within the outer bypass duct of the turbine casing and includes a heat exchange annular tube and a cantilever clamp. The heat exchange annular tube is clamped onto the cantilever clamp, and the front end of the cantilever clamp is fixed to the turbine casing mounting edge. The heat exchange annular tube includes an inlet pipe, a multi-loop annular tube, and an outlet pipe connected in sequence. The multi-loop annular tube includes multiple rows of semi-circular loop tubes connected in sequence along the airflow direction. The cantilever clamp is inclined along the airflow direction, so that the distance between the multiple rows of semi-circular loop tubes and the outer wall of the turbine casing increases sequentially along the airflow direction. The above-mentioned stepped annular heat exchange system has a simple structure and can pre-cool the air used for lubricating oil sealing in the bearing cavity in the ducting airflow path, thereby achieving a stable and reliable reduction in the air temperature used for lubricating oil sealing in the bearing cavity.

Description

Technical Field

[0001] This invention belongs to the field of aero-engines and relates to the design technology of lubricating oil seal air cooling, specifically to a stepped annular heat exchange system for pre-cooling lubricating oil seal air. Background Technology

[0002] The bearing cavity of an aircraft engine contains a large amount of lubricating oil used for bearing lubrication and cooling. To prevent oil leakage into the engine disk cavity, a sealing device needs to be installed between the bearing cavity and the surrounding air cavity. Air is drawn from the engine compression components to the sealing device to establish a suitable sealing pressure difference across the device, preventing oil leakage. An excessively large or small sealing pressure difference will cause unacceptable oil leakage. Furthermore, because the operating temperature of the lubricating oil within the bearing cavity is limited, the temperature of the air used for the oil seal must not exceed a certain limit to prevent excessive heat transfer to the lubricating oil system.

[0003] To simultaneously meet the pressure and temperature limitations of the lubricating oil seal, the commonly used design scheme is as follows: when the engine is operating at lower pressures or flying at high altitudes and low speeds, the compressor bleed air pressure is lower, so bleed air can be selected near the compressor outlet to prevent the pressure difference of the lubricating oil seal in the bearing cavity from being too small; when the engine is operating at higher pressures, both the compressor bleed air pressure and temperature are higher, so bleed air is selected near the compressor inlet to prevent the pressure difference of the lubricating oil seal in the bearing cavity from being too large and the temperature from being too high. This scheme requires a complex bleed air conversion device. However, due to the high temperature when bleed air is drawn from near the compressor outlet, and the need for electric or hydraulic drive, the bleed air conversion device often experiences conversion abnormalities under high-temperature environments in practical applications, making it difficult to reliably regulate the air temperature for the lubricating oil seal. Summary of the Invention

[0004] To address the problems of complex system structure and poor reliability in high-temperature environments caused by existing induced draft conversion devices in practical applications, which make it difficult to meet the requirements for regulating the temperature of the lubricating oil sealing air, this invention designs a stepped ring tube heat exchange system for pre-cooling the lubricating oil sealing air. This stepped ring tube heat exchange system has a simple structure and can pre-cool the air used for lubricating oil sealing in the bearing cavity in the induced draft airflow path, thereby achieving a stable and reliable reduction in the temperature of the air used for lubricating oil sealing in the bearing cavity.

[0005] The technical solution to achieve the purpose of the invention is as follows: A stepped ring tube heat exchange system for pre-cooling the air of the lubricating oil seal, the stepped ring tube heat exchange system is located in the outer bypass duct of the turbine casing, including a heat exchange ring tube and a cantilever clamp, the heat exchange ring tube is clamped on the cantilever clamp, and the front end of the cantilever clamp is fixed to the turbine casing mounting side.

[0006] The heat exchange loop includes an inlet pipe, a multi-loop loop, and an outlet pipe connected in sequence. The multi-loop loop includes multiple rows of semi-circular loop pipes connected in sequence along the airflow direction.

[0007] The cantilever clamp is inclined along the airflow direction, so that the distance between the multiple rows of semi-circular spiral tubes and the outer wall of the turbine casing increases sequentially along the airflow direction.

[0008] Furthermore, the outlet pipe is located behind the inlet pipe along the airflow direction; there are two sets of multi-loop pipes, and the two sets of multi-loop pipes are symmetrically arranged on both sides of the inlet pipe or the outlet pipe.

[0009] Furthermore, the multi-loop pipe is a four-loop pipe.

[0010] Furthermore, there is a gap between the first row of semi-circular loop tubes in the multi-loop annular tube and the turbine casing.

[0011] Furthermore, the cantilever clamp is a plate-like structure with one end open.

[0012] Preferably, the tilt angle of the cantilever clamp is 5° to 30°.

[0013] Furthermore, the inlet pipe is equipped with a throttling nozzle, and the outlet pipe is a circular vent pipe with ball heads at both ends.

[0014] Furthermore, both the inlet pipe and the outlet pipe are T-shaped tee pipes.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: The stepped annular heat exchange system designed in this invention can achieve pre-cooling of the air used for sealing the lubricating oil in the bearing cavity of an aero-engine, thereby reducing the air temperature used for sealing the lubricating oil in the bearing cavity. Simultaneously, the design of multiple rows of semi-circular loop tubes inclined along the airflow direction can solve the key technical problems of temperature rise of the airflow outside the upstream annular tube and weakened flow field in the downstream annular tube's external heat exchange.

[0016] Meanwhile, the stepped annular heat exchange system is located in the recessed area on the outside of the turbine casing, which can avoid its influence on the flow of the bypass. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0018] Figure 1 This is a schematic diagram of a stepped loop heat exchange system in a specific embodiment of the present invention;

[0019] Figure 2 This is a perspective view of the heat exchange loop pipe in a specific embodiment of the present invention;

[0020] Among them, 1. heat exchange loop pipe; 2. cantilever clamp; 11. inlet pipe; 12. multi-loop loop pipe; 13. outlet pipe; 100. turbine casing; 121. semi-circular loop pipe; 3. bolts. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0022] This specific embodiment discloses a stepped loop heat exchange system for pre-cooling the sealing air of lubricating oil. See [link to relevant documentation]. Figure 1 As shown, the stepped ring tube heat exchange system is located inside the outer bypass duct of the turbine casing 100, and includes a heat exchange ring tube 1 and a cantilever clamp 2. The heat exchange ring tube 1 is clamped on the cantilever clamp 2, and the front section of the cantilever clamp 2 is fixed to the mounting side of the turbine casing 100 by bolts 3.

[0023] In this embodiment, see Figure 1 As shown, in order to avoid the influence of the stepped ring tube heat exchange system on the airflow in the bypass duct, the stepped ring tube heat exchange system is set in the recessed area on the outside of the turbine casing 100, that is, at the position where the casing wall is close to the engine shaft center.

[0024] Among them, see Figure 2 As shown, the heat exchange loop 1 includes an inlet pipe 11, a multi-loop loop 12, and an outlet pipe 13 connected in sequence. The multi-loop loop 12 includes multiple rows of semi-circular loop pipes 121 connected in sequence along the airflow direction.

[0025] The cantilever clamp 2 is inclined along the airflow direction, so that the distance between the multiple rows of semi-circular loop tubes and the outer wall of the turbine casing 100 increases sequentially along the airflow direction. For example, when the distance between the first row of semi-circular loop tubes 121 and the turbine casing 100 is 4 to 5 mm, the distance between the subsequent rows of semi-circular loop tubes 121 and the turbine casing 100 along the airflow direction can be increased by 1 mm increments based on the first row of semi-circular loop tubes 121. This can also be understood as making the inclination angle of the cantilever clamp 2 5° to 30°.

[0026] Furthermore, the outlet pipe 13 is located behind the inlet pipe 11 along the airflow direction. See also Figure 2As shown, there are two sets of multi-loop ring pipes 12, and the two sets of multi-loop ring pipes 12 are symmetrically arranged on both sides of the inlet pipe 11 or the outlet pipe 13.

[0027] Furthermore, the aforementioned multi-loop pipe 12 is a four-loop pipe.

[0028] Further, see Figure 1 As shown, there is a gap between the first row of semi-circular loop tubes 121 in the multi-loop annular tube 12 and the turbine casing 100. In this embodiment, the wall thickness of the multi-loop annular tube 12 is 0.5 to 1.0 mm, and the distance between the first row of semi-circular loop tubes 121 and the turbine casing 100 is 4 to 5 mm.

[0029] Furthermore, see Figure 1 As shown, the cantilever clamp 2 is a plate-shaped structure with one end open. After the cantilever clamp 2 with one end open clamps the heat exchange ring pipe 1, it is pressed and suspended on the mounting side of the turbine casing 100 by bolts 3.

[0030] In an embodiment where no accompanying drawings are shown, the inlet pipe 11 is provided with a throttle nozzle, and the outlet pipe 13 is a circular vent pipe with ball-shaped ends.

[0031] In an embodiment where no accompanying drawings are shown, both the inlet pipe 11 and the outlet pipe 13 are T-shaped tee pipes.

[0032] When the above-mentioned stepped loop heat exchange system is in operation, please refer to... Figure 1 and Figure 2 As shown, the bleed air A from the high-pressure compressor outlet enters the heat exchange ring pipe 1 from the inlet pipe 11, and then splits to both sides into two symmetrical sets of multi-loop ring pipes 12. It flows in the multiple rows of semi-circular loop pipes 121 of each set of multi-loop ring pipes 12, and exchanges heat with the cold air B in the outer bypass duct of the turbine casing 100. After the temperature of the bleed air A is reduced, it is discharged from the outlet pipe 13 to form sealing air C for sealing the lubricating oil in the bearing cavity.

[0033] The aforementioned stepped annular heat exchange system can pre-cool the air used for sealing the lubricating oil in the aero-engine bearing cavity, thereby reducing the air temperature used for sealing the bearing cavity lubricating oil. Simultaneously, the design of multiple rows of semi-circular loop-shaped tubes inclined along the airflow direction solves the key technical problems of airflow temperature rise on the outer side of the upstream annular tube and weakened flow field for heat exchange on the outer side of the downstream annular tube. Furthermore, the stepped annular heat exchange system is located in the recessed area on the outer side of the turbine casing, which avoids its impact on the bypass flow.

[0034] This specific embodiment also provides a method for analyzing stepped loop heat transfer, including:

[0035] S1. A two-dimensional CFD calculation model of the cold air flow on the outer wall of the heat exchange loop 1 is established using a general method.

[0036] In the two-dimensional CFD calculation model, the outer wall temperature of heat exchange loop 1 is set as the hot gas inlet temperature;

[0037] S2. Obtain the convective heat transfer coefficient distribution on the outer wall of heat exchange loop 1 using a two-dimensional CFD calculation model;

[0038] S3. Based on the circumferential area of ​​heat exchange loop 1, the convective heat transfer coefficient distribution is weighted and averaged to obtain the convective heat transfer coefficient.

[0039] S4. A one-dimensional network method calculation model of the internal flow of heat exchange loop 1 is established using a general method. The convective heat transfer coefficient is used as the input parameter for the cold air flow on the outer wall of heat exchange loop 1 in the one-dimensional network method calculation model. The outer wall temperature of heat exchange loop 1 is output and used as the input parameter for the outer wall temperature of heat exchange loop 1 in the two-dimensional CFD calculation model.

[0040] S5. Repeat steps S3 and S4 for iterative calculation until the temperature difference between the outer wall surface of the heat exchange loop 1 obtained by the one-dimensional network method calculation model in two adjacent rounds is no greater than 1K.

[0041] S6. A three-dimensional CFD calculation model of hot gas flow on the inner wall of the heat exchange loop is established using a general method, and the calculation results of the one-dimensional network method for the flow inside the heat exchange loop are verified.

[0042] The above-described step-loop heat exchanger analysis method can quickly and effectively evaluate the heat exchange performance of the step-loop heat exchanger system, providing technical support for the optimized design of the step-loop heat exchanger system.

[0043] The above description is only a preferred embodiment 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 within the protection scope of the present invention.

[0044] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A stepped annular heat exchange system for pre-cooling lubricating oil sealing air, wherein the stepped annular heat exchange system is located within the outer bypass duct of a turbine casing (100), characterized in that: It includes a heat exchange ring tube (1) and a cantilever clamp (2), wherein the heat exchange ring tube (1) is clamped on the cantilever clamp (2), and the front end of the cantilever clamp (2) is fixed on the mounting side of the turbine casing (100); The heat exchange loop (1) includes an inlet pipe (11), a multi-loop loop (12), and an outlet pipe (13) connected in sequence. The multi-loop loop (12) includes multiple rows of semi-circular loop pipes connected in sequence along the direction of cold air flow in the outer duct. The cantilever clamp (2) is inclined along the direction of the cold air flow in the outer duct, so that the distance between the multiple rows of semi-circular loop pipes and the outer wall of the turbine casing (100) increases sequentially along the air flow direction.

2. The stepped loop heat exchange system for pre-cooling air in lubricating oil sealing as described in claim 1, characterized in that: The outlet pipe (13) is located behind the inlet pipe (11) along the direction of the cold air flow in the outer duct; there are two sets of multi-loop ring pipes (12), and the two sets of multi-loop ring pipes (12) are symmetrically arranged on both sides of the inlet pipe (11) or the outlet pipe (13).

3. The stepped loop heat exchange system for pre-cooling air in lubricating oil sealing as described in claim 1 or 2, characterized in that: The multi-loop pipe (12) is a four-loop pipe.

4. The stepped loop heat exchange system for pre-cooling air in lubricating oil sealing as described in claim 1, characterized in that: The first row of semi-circular loop tubes in the multi-loop annular tube (12) has a gap with the turbine casing (100).

5. The stepped loop heat exchange system for pre-cooling air in lubricating oil sealing as described in claim 1 or 4, characterized in that: The cantilever clamp (2) is a plate-shaped structure with one end open.

6. The stepped loop heat exchange system for pre-cooling air in lubricating oil sealing as described in claim 5, characterized in that: The tilt angle of the cantilever clamp (2) is 5°~30°.

7. The stepped loop heat exchange system for pre-cooling air in lubricating oil sealing as described in claim 1, characterized in that: The inlet pipe (11) is equipped with a throttle nozzle, and the outlet pipe (13) is a circular vent pipe with ball heads at both ends.

8. The stepped loop heat exchange system for pre-cooling air in lubricating oil sealing as described in claim 1, characterized in that: Both the inlet pipe (11) and the outlet pipe (13) are T-shaped tee pipes.

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