A Diffuser Thermal Protection Design Method

Abstract

The present invention relates to the field of rocket engine high-altitude simulation test technology, and discloses a diffuser thermal protection design method, including: determining the switching position of the supersonic flow of gas and the subsonic flow of gas in the diffuser; dividing the diffuser into: a supersonic gas section, a subsonic gas straight section and a subsonic gas expansion section; arranging a coolant jacket around the diffuser; the coolant jackets corresponding to the supersonic gas section, the subsonic gas straight section and the subsonic gas expansion section are: a section A coolant jacket, a section B coolant jacket and a section C coolant jacket; the outer wall diameter of the section A coolant jacket is greater than the outer wall diameter of the section B coolant jacket. The present application increases the coolant flow velocity and heat transfer coefficient by surrounding the supersonic gas section and the subsonic gas straight section with coolant jackets of different thicknesses, so as to transfer heat out faster and avoid the rapid rise in temperature of the subsonic gas straight section, thereby making the diffuser more reliably thermally protected.

Description

Technical Field

[0001] The invention relates to the technical field of rocket engine high-altitude simulation test, and in particular to a diffuser thermal protection design method. Background Art

[0002] Passive ejection technology is a commonly used technology for rocket engines in high-altitude flight simulation tests. In passive ejection technology, a diffuser is generally set at the outlet of the rocket engine. Because the temperature of the high-temperature combustion gas ejected from the outlet of the rocket engine is as high as 3000K or more, the wall of the diffuser is generally cooled by water cooling. Specifically, a cooling water jacket of fixed thickness is set on the outer wall of the diffuser. The diffuser is generally composed of a straight tube section and an expansion section connected front and back. After the shock wave, the high-temperature combustion gas in the diffuser is converted from supersonic speed to subsonic speed, and the static temperature and density of the high-temperature combustion gas both increase, causing the heat flow of the high-temperature combustion gas to increase significantly, resulting in insufficient protection of the diffuser wall after the high-temperature combustion gas shock wave. Summary of the invention

[0003] In view of this, the present invention provides a diffuser thermal protection design method to solve the problem that the high-temperature combustion gas in the diffuser is converted from supersonic to subsonic after the shock wave, the static temperature and density of the high-temperature combustion gas both increase, causing the heat flow of the high-temperature combustion gas to increase significantly, resulting in insufficient wall protection of the diffuser after the high-temperature combustion gas shock wave.

[0004] The present invention provides a diffuser thermal protection design method, comprising:

[0005] Determine the position where the supersonic flow and subsonic flow of the fuel gas are switched in the diffuser;

[0006] When the position where the supersonic gas flow and the subsonic gas flow are switched is located in the straight section of the diffuser, taking the switching position as a reference, a position offset by a first set distance upstream of the gas flow is used as a boundary line between the supersonic gas region and the subsonic gas region;

[0007] According to the dividing line and the position of the expansion section of the diffuser, the gas channel in the diffuser is divided into: a gas supersonic section, a gas subsonic straight section and a gas subsonic expansion section from upstream to downstream of the gas flow; the diameter of the internal channel of the gas supersonic section is D;

[0008] A coolant jacket is arranged around the outer wall of the diffuser; the coolant jacket is provided with a coolant inlet and a coolant outlet; and coolant flows in the coolant channel of the coolant jacket;

[0009] The coolant inlet is arranged near the front end of the gas supersonic section; the coolant outlet is arranged near the rear end of the gas subsonic expansion section; the coolant jackets corresponding to the external positions of the gas supersonic section, the gas subsonic straight section and the gas subsonic expansion section are respectively: the A section coolant jacket, the B section coolant jacket and the C section coolant jacket;

[0010] The coolant jacket of section A and the coolant jacket of section B are provided with annular channels with fixed diameters; the coolant jacket of section C is provided with annular channels with variable diameters; and the outer wall diameter of the coolant jacket of section A is a first diameter, and the outer wall diameter of the coolant jacket of section B is a second diameter, and the second diameter is smaller than the first diameter; the inner wall diameter of the coolant jacket of section A is a third diameter, and the inner wall diameter of the coolant jacket of section B is a fourth diameter; the third diameter is equal to the fourth diameter;

[0011] The inner wall of the coolant jacket of the C section and the outer wall of the coolant jacket of the C section are both conical; the cone angle formed by the inner wall of the coolant jacket of the C section is the first cone angle, and the cone angle formed by the outer wall of the coolant jacket of the C section is the second cone angle, and the angle of the second cone angle is smaller than the angle of the first cone angle. Beneficial effect: The present application adopts the above technical scheme, and by surrounding the coolant jackets of different thicknesses in the supersonic section of the gas and the subsonic straight section of the gas, the coolant flow area inside the coolant jacket outside the subsonic straight section of the gas with a higher temperature is smaller, thereby increasing the flow speed of the coolant and increasing the heat transfer coefficient, so as to transfer the heat generated by the gas in the subsonic straight section of the gas faster, avoid the rapid rise of the temperature of the subsonic straight section of the gas, and thus make the diffuser more reliable in thermal protection. In addition, in the subsonic expansion section of the gas, by setting the angle of the second cone angle smaller than the angle of the first cone angle, the flow rate of the coolant is faster, so that the gas is faster when it flows from upstream to downstream, thereby playing a better role in thermal protection for the diffuser.

[0012] Optionally, a computational fluid dynamics method is used to determine the Mach number distribution in the gas channel of the diffuser, thereby determining the position where the gas supersonic flow and the gas subsonic flow in the diffuser are switched. Beneficial effect: The present application adopts the above technical solution to accurately and reliably determine the position where the gas supersonic flow and the gas subsonic flow in the diffuser are switched.

[0013] Optionally, when the switching position between the supersonic flow of the gas and the subsonic flow of the gas is located in the expansion section of the diffuser, the diameter of the straight section of the diffuser is increased until the switching position is moved forward to the straight section of the diffuser. Beneficial effect: The present application adopts the above technical solution to move the switching position forward to the straight section of the diffuser, which facilitates the arrangement of the coolant jacket of section A and the coolant jacket of section B.

[0014] Optionally, the first set distance is 0.1D.

[0015] Optionally, the cross-sectional area of ​​the annular channel of the coolant jacket of section A is the first cross-sectional area, and the cross-sectional area of ​​the annular channel of the coolant jacket of section B is the second cross-sectional area; the second cross-sectional area is 0.5 to 0.7 times the first cross-sectional area. Beneficial effect: The present application adopts the above technical solution to ensure that the gas temperature in the supersonic section of the gas and the subsonic straight section of the gas is basically the same, to prevent the temperature from being too high, so as to provide effective thermal protection for the diffuser.

[0016] Optionally, the outer wall of the coolant jacket of section A and the outer wall of the coolant jacket of section B are transitioned by a tapered section.

[0017] Optionally, the outer wall of the coolant jacket of section A is connected to the inner wall of the coolant jacket of section A by a plurality of first reinforcing ribs arranged at intervals along the circumferential direction. Beneficial effect: The present application adopts the above technical solution to improve the overall strength of the coolant jacket of section A.

[0018] Optionally, the area between the position where the supersonic flow of the gas and the subsonic flow of the gas are switched as the midpoint, the position offset by the second set distance along the upstream of the gas flow as the starting point, and the position offset by the third set distance along the downstream of the gas flow as the end point is the shock wave zone; the outer wall of the coolant jacket corresponding to the shock wave zone and the inner wall of the coolant jacket are connected by a plurality of second reinforcing ribs arranged at intervals along the circumferential direction; a plurality of spacer ribs are arranged at intervals along the circumferential direction on the outer wall of the coolant jacket corresponding to the shock wave zone, and a gap is provided between the spacer ribs and the inner wall of the coolant jacket. Beneficial effect: The present application adopts the above technical solution. Since the shock wave hits the inner wall surface of the diffuser at the position where the supersonic flow of the gas and the subsonic flow of the gas are switched, causing the local maximum temperature, the cross-sectional area of ​​the coolant channel is further reduced by setting the spacer ribs, thereby further increasing the flow rate of the coolant, increasing the heat transfer coefficient, reducing the temperature of the inner wall surface of the diffuser, and providing more effective thermal protection for the diffuser.

[0019] Optionally, the second set distance and the third set distance are both 0.1D; the gap is greater than 2 mm. Beneficial effects: The present application adopts the above technical solution to avoid affecting the heat exchange effect of the coolant on the shock wave zone by specifically limiting the value of the gap.

[0020] Optionally, the coolant is cooling water. Beneficial effect: The application adopts the above technical solution, and the thermal protection cost is lower. 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 A schematic cross-sectional structure diagram of a diffuser provided in an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the cross-sectional structure of the diffuser provided in an embodiment of the present invention at the supersonic section of the gas;

[0024] Figure 3 It is a schematic diagram of the cross-sectional structure of the diffuser in the shock wave region provided in an embodiment of the present invention.

[0025] Description of reference numerals:

[0026] 1. Rocket engine; 2. Coolant inlet; 3. Gas channel; 4. Outer wall of coolant jacket of section A; 5. Inner wall of coolant jacket of section A; 6. Coolant channel; 7. Conical section; 8. Outer wall of coolant jacket of section B; 9. Inner wall of coolant jacket of section B; 10. Outer wall of coolant jacket of section C; 11. Inner wall of coolant jacket of section C; 12. First reinforcing rib; 13. Coolant outlet; 14. Second reinforcing rib; 15. Placeholder rib; 16. Gas supersonic section; 17. Gas subsonic straight section; 18. Gas subsonic expansion section. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0028] like Figures 1 to 3 A specific implementation of the diffuser thermal protection design method shown includes the following steps:

[0029] S1. Determine the position where the supersonic flow of the gas and the subsonic flow of the gas in the diffuser are switched; specifically, the Mach number distribution in the gas channel 3 of the diffuser can be determined by using a computational fluid dynamics method, and then determine the position where the supersonic flow of the gas and the subsonic flow of the gas in the diffuser are switched. Figure 1As shown, the diffuser is arranged at the rear of the rocket engine 1, and the gas ejected from the rocket engine 1 passes through the gas channel 3 inside the diffuser. The diffuser comprises: a straight tube section and an expansion section connected in sequence.

[0030] S2. When the switching position of the gas supersonic flow and the gas subsonic flow is located in the straight section of the diffuser, the switching position is used as a reference, and the position offset by a first set distance along the upstream of the gas flow is used as the boundary between the gas supersonic region and the gas subsonic region. Specifically, the first set distance is 0.1D.

[0031] Furthermore, when the switching position between the supersonic gas flow and the subsonic gas flow is located at the expansion section of the diffuser, the diameter of the straight section of the diffuser is increased until the switching position moves forward to the straight section of the diffuser.

[0032] S3. According to the dividing line and the position of the expansion section of the diffuser, the gas channel 3 in the diffuser is divided into: a gas supersonic section 16, a gas subsonic straight section 17 and a gas subsonic expansion section 18 from the upstream to the downstream of the gas flow; the diameter of the internal channel of the gas supersonic section 16 is D; the gas supersonic section 16 and the gas subsonic straight section 17 are separated by the dividing line between the gas supersonic zone and the gas subsonic zone, and the gas subsonic straight section 17 and the gas subsonic expansion section 18 are separated by the dividing line between the straight section and the expansion section of the diffuser.

[0033] S4. A coolant jacket is provided around the outer wall of the diffuser; the coolant jacket is provided with a coolant inlet 2 and a coolant outlet 13; a coolant flows in the coolant channel 6 of the coolant jacket; specifically, the coolant is cooling water. The coolant inlet 2 is provided near the front end of the supersonic section 16 of the gas; the coolant outlet 13 is provided near the rear end of the subsonic expansion section 18 of the gas; the coolant jackets at the outer positions corresponding to the supersonic section 16 of the gas, the subsonic straight section 17 of the gas and the subsonic expansion section 18 are respectively: the A section coolant jacket, the B section coolant jacket and the C section coolant jacket. The coolant jacket of section A and the coolant jacket of section B are provided with annular channels of fixed diameter; the coolant jacket of section C is provided with annular channels of variable diameter; and the diameter of the outer wall 4 of the coolant jacket of section A is the first diameter, and the diameter of the outer wall 8 of the coolant jacket of section B is the second diameter, and the second diameter is smaller than the first diameter; the diameter of the inner wall 5 of the coolant jacket of section A is the third diameter, and the diameter of the inner wall 9 of the coolant jacket of section B is the fourth diameter; the third diameter is equal to the fourth diameter. Specifically, the cross-sectional area of ​​the annular channel of the coolant jacket of section A is the first cross-sectional area, and the cross-sectional area of ​​the annular channel of the coolant jacket of section B is the second cross-sectional area; the second cross-sectional area is 0.5 to 0.7 times the first cross-sectional area. The outer wall 4 of the coolant jacket of section A and the outer wall 8 of the coolant jacket of section B are transitioned by a tapered section 7. Specifically, the cone angle of the tapered section 7 ranges from 40 degrees to 80 degrees.

[0034] Further, such as Figure 2 As shown, the outer wall of the coolant jacket of section A is connected to the inner wall of the coolant jacket of section A by a plurality of first reinforcing ribs 12 arranged at intervals along the circumference, which may be welded. The plurality of first reinforcing ribs 12 may be evenly distributed along the circumference.

[0035] Further, such as Figure 3As shown, the area between the position where the supersonic flow of the gas and the subsonic flow of the gas are switched as the midpoint, the position offset by the second set distance along the upstream of the gas flow as the starting point, and the position offset by the third set distance along the downstream of the gas flow as the end point is the shock wave zone; specifically, the second set distance and the third set distance can both be 0.1D. The outer wall of the coolant jacket corresponding to the shock wave zone and the inner wall of the coolant jacket are connected by a plurality of second reinforcing ribs 14 arranged at intervals along the circumference, which can be specifically welded, and the plurality of second reinforcing ribs 14 can be evenly distributed along the circumference. In the area where the first reinforcing rib 12 and the second reinforcing rib 14 may overlap, the first reinforcing rib 12 and the second reinforcing rib 14 are arranged to overlap. A plurality of spacer ribs 15 are arranged at intervals along the circumference on the outer wall of the coolant jacket corresponding to the shock wave zone, and the larger the cross-sectional area of ​​the spacer rib 15, the faster the flow rate of the coolant. A gap is provided between the spacer rib 15 and the inner wall of the coolant jacket; specifically, the gap is greater than 2 mm. The place-occupying ribs 15 are streamlined on the end surface facing the flow of the coolant to reduce the flow resistance of the coolant. The number of the place-occupying ribs 15 is n times the number of the second reinforcing ribs 14, where n is an integer not less than 1. When n is 1, the place-occupying ribs 15 and the second reinforcing ribs 14 can be arranged in an interlaced manner. Multiple place-occupying ribs 15 can be evenly distributed along the circumferential direction.

[0036] The inner wall 11 of the C-section coolant jacket and the outer wall 10 of the C-section coolant jacket are both conical; the cone angle formed by the inner wall 11 of the C-section coolant jacket is a first cone angle, and the cone angle formed by the outer wall 10 of the C-section coolant jacket is a second cone angle, and the angle of the second cone angle is smaller than the angle of the first cone angle.

[0037] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A diffuser thermal protection design method, characterized in that: include: Determine the position where the supersonic flow and subsonic flow of the fuel gas are switched in the diffuser; When the position where the supersonic gas flow and the subsonic gas flow are switched is located in the straight section of the diffuser, taking the switching position as a reference, a position offset by a first set distance upstream of the gas flow is used as a boundary line between the supersonic gas region and the subsonic gas region; According to the dividing line and the position of the expansion section of the diffuser, the gas passage (3) in the diffuser is divided into: a gas supersonic section (16), a gas subsonic straight section (17) and a gas subsonic expansion section (18) in order from the upstream to the downstream of the gas flow; the diameter of the internal passage of the gas supersonic section (16) is D; A coolant jacket is disposed around the outer wall of the diffuser; the coolant jacket is provided with a coolant inlet (2) and a coolant outlet (13); coolant flows in the coolant channel (6) of the coolant jacket; The coolant inlet (2) is arranged near the front end of the supersonic gas section (16); the coolant outlet (13) is arranged near the rear end of the subsonic gas expansion section (18); the coolant jackets at the outer positions corresponding to the supersonic gas section (16), the subsonic gas straight section (17) and the subsonic gas expansion section (18) are respectively: a section A coolant jacket, a section B coolant jacket and a section C coolant jacket; The coolant jacket of section A and the coolant jacket of section B are provided with annular channels with fixed diameters; the coolant jacket of section C is provided with annular channels with variable diameters; and the diameter of the outer wall (4) of the coolant jacket of section A is a first diameter, and the diameter of the outer wall (8) of the coolant jacket of section B is a second diameter, and the second diameter is smaller than the first diameter; the diameter of the inner wall (5) of the coolant jacket of section A is a third diameter, and the diameter of the inner wall (9) of the coolant jacket of section B is a fourth diameter; and the third diameter is equal to the fourth diameter; The inner wall (11) of the C-section coolant jacket and the outer wall (10) of the C-section coolant jacket are both conical; the cone angle formed by the inner wall (11) of the C-section coolant jacket is a first cone angle, and the cone angle formed by the outer wall (10) of the C-section coolant jacket is a second cone angle, and the angle of the second cone angle is smaller than the angle of the first cone angle.

2. The diffuser thermal protection design method according to claim 1, characterized in that: The Mach number distribution in the gas passage (3) of the diffuser is determined by using a computational fluid dynamics method, and the position where the supersonic gas flow and the subsonic gas flow in the diffuser are switched is further determined.

3. The diffuser thermal protection design method according to claim 1, characterized in that: When the switching position between the supersonic gas flow and the subsonic gas flow is located at the expansion section of the diffuser, the diameter of the straight section of the diffuser is increased until the switching position moves forward to the straight section of the diffuser.

4. The diffuser thermal protection design method according to claim 1, characterized in that: The first set distance is 0.1D.

5. The diffuser thermal protection design method according to claim 1, characterized in that: The cross-sectional area of ​​the annular channel of the coolant jacket of section A is the first cross-sectional area, and the cross-sectional area of ​​the annular channel of the coolant jacket of section B is the second cross-sectional area; the second cross-sectional area is 0.5 to 0.7 times the first cross-sectional area.

6. The diffuser thermal protection design method according to any one of claims 1 to 5, characterized in that: The outer wall (4) of the coolant jacket of section A and the outer wall (8) of the coolant jacket of section B are transitioned by a tapered section (7).

7. The diffuser thermal protection design method according to any one of claims 1 to 5, characterized in that: The outer wall of the A-section coolant jacket and the inner wall of the A-section coolant jacket are connected via a plurality of first reinforcing ribs (12) arranged at intervals along the circumferential direction.

8. The diffuser thermal protection design method according to claim 7, characterized in that: The area between the position where the supersonic flow of the fuel gas and the subsonic flow of the fuel gas are switched as the midpoint, the position offset by a second set distance along the upstream of the fuel gas flow as the starting point, and the position offset by a third set distance along the downstream of the fuel gas flow as the end point is the shock wave zone; the outer wall of the coolant jacket corresponding to the shock wave zone and the inner wall of the coolant jacket are connected by a plurality of second reinforcing ribs (14) arranged at intervals along the circumferential direction; a plurality of spacer ribs (15) are arranged at intervals along the circumferential direction on the outer wall of the coolant jacket corresponding to the shock wave zone, and a gap is provided between the spacer ribs (15) and the inner wall of the coolant jacket.

9. The diffuser thermal protection design method according to claim 8, characterized in that: The second set distance and the third set distance are both 0.1D; and the gap is greater than 2 mm.

10. The diffuser thermal protection design method according to any one of claims 1 to 5, characterized in that: The coolant is cooling water.

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