A ramjet stepped combustion chamber and method of designing the same

Abstract

The present application belongs to ramjet engine technical field, disclose a kind of ramjet engine stepped combustion chamber and its design method.Ramjet engine stepped combustion chamber includes combustion chamber front expansion section, ignition section and combustion chamber rear expansion section sequentially connected from front to back along the direction of flow, and the center cavity of each section is through from front to back;Annular two-stage stepped groove and annular one-stage stepped groove are sequentially arranged on the inner wall surface of ignition section from front to back along the direction of flow;Several igniter interfaces are evenly distributed in the circumferential direction of two-stage stepped groove.The design method forms two-stage backflow area through two-stage stepped groove, and the stepped groove reduces the flow rate of combustible gas, so that the combustible gas can burn stably, improve the temperature of ramjet engine combustion chamber, improve the ignition reliability of ramjet engine, and expand the ignition Mach number range of various types of igniters on ramjet engine.

Description

Technical Field

[0001] This invention belongs to the field of ramjet engine technology, specifically relating to a stepped combustion chamber for a ramjet engine and its design method. Background Technology

[0002] Ramjet engines utilize oxygen obtained from the atmosphere during the ascent process as an oxidizer for combustion. This oxygen is then used to promote combustion in the combustion chamber. However, due to the high velocity of the airflow entering the ramjet engine, with the time spent in the combustion chamber on the order of milliseconds, achieving mixing, ignition, and combustion of the combustible material in such a short time is extremely difficult. As ramjet engines have evolved and the Mach numbers used have increased, the challenges of ignition and stable combustion in the combustion chamber have become even greater.

[0003] Currently, there is an urgent need to develop a stepped combustion chamber for ramjet engines and its design method. Summary of the Invention

[0004] This invention utilizes externally input energy for stable ignition at low Mach speeds. One technical problem to be solved is to provide a stepped combustion chamber for a ramjet engine, and another technical problem to be solved is to provide a design method for a stepped combustion chamber for a ramjet engine.

[0005] The ramjet engine stepped combustion chamber of the present invention includes a front expansion section, an ignition section and a rear expansion section of the combustion chamber connected sequentially from front to back along the incoming flow direction, with the central cavity of each section being interconnected from front to back.

[0006] The pre-expansion section of the combustion chamber is a conical tube with its inner diameter gradually increasing along the flow direction. The inner diameter at the inlet of the pre-expansion section is... D 1. The angle between the generatrix of the cone in the front expansion section of the combustion chamber and the central axis is α; the rear expansion section of the combustion chamber is also a conical tube, with its inner diameter gradually increasing along the flow direction, and the inner diameter at the outlet of the rear expansion section is... D 2. The angle between the generatrix of the cone of the rear expansion section of the combustion chamber and the central axis is also α;

[0007] On the inner wall of the ignition section, along the flow direction, an annular two-stage stepped groove and an annular one-stage stepped groove are sequentially arranged from front to back; a stepped transition is used between the front expansion section of the combustion chamber and the two-stage stepped groove; a conical tube is used for transition between the two-stage stepped groove and the one-stage stepped groove, and between the one-stage stepped groove and the rear expansion section of the combustion chamber; the axial length of the two-stage stepped groove and the corresponding transition conical tube is... C 1. The axial length of the ignition section cavity is C 2. The axial length of the stepped combustion chamber of the ramjet engine is L; several igniter interfaces are evenly distributed around the circumference of the secondary stepped groove; the igniter interfaces are through holes.

[0008] The inner diameter of the second-stage stepped groove is larger than the inner diameter of the first-stage stepped groove, and the difference in radius between the two is... H 2; The inner diameter of the first-stage stepped groove is larger than the inner diameter at the outlet of the front expansion section of the combustion chamber, and the difference in radius between the two is... H 1; The inner diameter of the first-stage stepped groove is larger than the inner diameter at the outlet of the rear expansion section of the combustion chamber. D 2;

[0009] The parameters satisfy the following relationship:

[0010] .

[0011] Furthermore, the included angle α ranges from 0.5° to 2°.

[0012] Furthermore, an igniter is installed on the igniter interface.

[0013] The design method for a stepped combustion chamber in a ramjet engine according to the present invention includes the following:

[0014] a. Design the angle between the generatrix of the cone of the front expansion section of the combustion chamber and the central axis, and the angle between the generatrix of the cone of the rear expansion section of the combustion chamber and the central axis, to reduce the influence of the boundary layer on the inner wall surface and avoid axial reduction of the main flow channel;

[0015] b. Design a two-stage stepped groove and a first-stage stepped groove in the ignition section to reduce the flow velocity of the combustible mixture and form a stepped gas recirculation zone along the axial direction. Use the gas recirculation zone of the ignition section as the ignition zone of the stepped combustion chamber of the ramjet engine to improve the ignition success rate of the combustible mixture in the first-stage stepped groove.

[0016] c. Connect the front end of the combustion chamber front expansion section to the rear end of the ramjet engine isolation section. The combustion chamber front expansion section is used to receive the combustible mixture formed by the mixing of fuel and air in the ramjet engine isolation section.

[0017] d. Ignite the combustible mixture in the ignition section, converting it into combustion gas and ensuring stable combustion; the specific steps are as follows:

[0018] d1. The combustible gas mixture enters the ignition section from the front expansion section of the combustion chamber, forming a first-stage annular reflux zone at the first-stage stepped groove. In the first-stage annular reflux zone, the velocity of the combustible gas mixture decreases and the temperature increases. In the second-stage stepped groove, the combustible gas mixture forms a second-stage annular reflux zone, where the velocity decreases again and the temperature continues to rise.

[0019] d2. Ignition: The ignition energy of the igniter is transferred to the secondary stepped groove, igniting the combustible mixture within it. This results in a ring-shaped distribution of combustion gas within the secondary stepped groove. The ring-shaped combustion gas in the secondary stepped groove ignites the combustible mixture in the primary stepped groove, creating a larger area of ​​ring-shaped combustion gas, achieving a gradual and stable amplification of energy. Finally, the combustion gas surrounds the inner cavity of the ignition section, resulting in continuous and stable combustion.

[0020] e. In the rear expansion section of the combustion chamber, the combustible mixture is further burned to improve the combustion efficiency of the combustible mixture, and the combustion gas is discharged into the tail nozzle of the ramjet engine for power conversion.

[0021] The stepped combustion chamber for ramjet engines and its design method of the present invention, by setting two levels of annularly distributed stepped grooves on the combustion chamber, makes the combustible mixture form two low-speed recirculation zones, and then ignites it by externally inputting a certain amount of energy, forming an annularly distributed and stable combustion flame. The energy is amplified step by step to finally achieve stable ignition of the combustion chamber, effectively solving the problem of stable ignition of ramjet engines.

[0022] In summary, the stepped combustion chamber for ramjet engines and its design method of the present invention form two-stage recirculation zones through two-stage stepped grooves. The stepped grooves reduce the flow velocity of the combustible mixture, enabling the combustible mixture to burn stably, increasing the temperature of the ramjet engine combustion chamber, improving the ignition reliability of the ramjet engine, and expanding the ignition Mach number range of various types of igniters on ramjet engines, thus having practical engineering value. Attached Figure Description

[0023] Figure 1a This is a schematic diagram of the stepped combustion chamber of the ramjet engine of the present invention;

[0024] Figure 1b This is a schematic diagram of the stepped combustion chamber of the ramjet engine of the present invention. Figure 1a (BB cross-section view);

[0025] Figure 2 This is a schematic diagram of the design parameters for the stepped combustion chamber of the ramjet engine of the present invention. Figure 1a (AA cross-section view).

[0026] In the diagram, 101 is the front expansion section of the combustion chamber; 201 is the ignition section; 202 is the first-stage stepped groove; 203 is the second-stage stepped groove; 204 is the igniter interface; and 301 is the rear expansion section of the combustion chamber. Detailed Implementation

[0027] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] Example: Figure 1a , Figure 1b , Figure 2 As shown, the stepped combustion chamber of the ramjet engine in this embodiment includes a front expansion section 101, an ignition section 201 and a rear expansion section 301 connected sequentially from front to back along the incoming flow direction, with the central cavity of each section being interconnected from front to back.

[0029] The combustion chamber front expansion section 101 is a conical tube with its inner diameter gradually increasing along the flow direction. The inner diameter at the inlet of the combustion chamber front expansion section 101 is... D 1. The angle between the generatrix of the cone of the front expansion section 101 of the combustion chamber and the central axis is α; the rear expansion section 301 of the combustion chamber is also a conical tube, with its inner diameter gradually increasing along the flow direction, and the inner diameter at the outlet of the rear expansion section 301 is... D 2. The angle between the conical generatrix of the rear expansion section 301 of the combustion chamber and the central axis is also α;

[0030] On the inner wall of the ignition section 201, along the flow direction, an annular secondary stepped groove 203 and an annular primary stepped groove 202 are sequentially arranged from front to back; a stepped transition is adopted between the combustion chamber front expansion section 101 and the secondary stepped groove 203; the transition between the secondary stepped groove 203 and the primary stepped groove 202, and between the primary stepped groove 202 and the combustion chamber rear expansion section 301, are all achieved through conical tubes; the axial length of the secondary stepped groove 203 and the corresponding transition conical tube is... C 1. The axial length of the inner cavity of the ignition section 201 is C 2. The axial length of the stepped combustion chamber of the ramjet engine is L; several igniter interfaces 204 are evenly distributed in the circumference of the secondary stepped groove 203; the igniter interfaces 204 are through holes.

[0031] The inner diameter of the secondary stepped groove 203 is larger than the inner diameter of the primary stepped groove 202, and the difference in radius between the two is... H 2; The inner diameter of the first-stage stepped groove 202 is larger than the inner diameter at the outlet of the front expansion section 101 of the combustion chamber, and the difference in radius between the two is... H 1; The inner diameter of the first-stage stepped groove 202 is larger than the inner diameter at the outlet of the rear expansion section 301 of the combustion chamber. D 2;

[0032] The parameters satisfy the following relationship:

[0033] .

[0034] Furthermore, the included angle α ranges from 0.5° to 2°.

[0035] Furthermore, an igniter is installed on the igniter interface 204.

[0036] The design method for the stepped combustion chamber of a ramjet engine in this embodiment includes the following:

[0037] a. Design the angle between the generatrix of the cone of the front expansion section 101 of the combustion chamber and the central axis, and the angle between the generatrix of the cone of the rear expansion section 301 of the combustion chamber and the central axis, to reduce the influence of the boundary layer on the inner wall surface and avoid axial reduction of the main flow channel;

[0038] b. Design a secondary stepped groove 203 and a primary stepped groove 202 within the ignition section 201 to reduce the flow velocity of the combustible mixture and form a stepped gas recirculation zone along the axial direction. Use the gas recirculation zone of the ignition section 201 as the ignition zone of the ramjet engine's stepped combustion chamber to improve the ignition success rate of the combustible mixture within the primary stepped groove 202.

[0039] c. Connect the front end of the combustion chamber front expansion section 101 to the rear end of the ramjet engine isolation section. The combustion chamber front expansion section 101 is used to receive the combustible mixture formed by the mixing of fuel and air in the ramjet engine isolation section.

[0040] d. Ignite the combustible mixture in ignition section 201, converting the combustible mixture into combustion gas and ensuring stable combustion; the specific steps are as follows:

[0041] d1. The combustible gas mixture enters the ignition section 201 from the front expansion section 101 of the combustion chamber, forming a first-stage annular reflux zone at the first-stage stepped groove 202. In the first-stage annular reflux zone, the velocity of the combustible gas mixture decreases and the temperature increases. In the second-stage stepped groove 203, the combustible gas mixture forms a second-stage annular reflux zone, where the velocity decreases again and the temperature continues to rise.

[0042] d2. Ignition by the igniter: The ignition energy of the igniter is transferred to the secondary stepped groove 203, igniting the combustible mixture within the secondary stepped groove 203, resulting in a ring-shaped distribution of combustion gas within the secondary stepped groove 203. The ring-shaped distribution of combustion gas within the secondary stepped groove 203 ignites the combustible mixture within the primary stepped groove 202, forming a larger area of ​​ring-shaped combustion gas, achieving a step-by-step stable amplification of energy. Finally, the combustion gas surrounds the inner cavity of the ignition section 201, undergoing continuous and stable combustion.

[0043] e. In the rear expansion section 301 of the combustion chamber, the combustible mixture is further burned to improve the combustion efficiency of the combustible mixture, and the combustion gas is discharged into the tail nozzle of the ramjet engine for power conversion.

[0044] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A stepped combustion chamber for a ramjet engine, characterized in that, The ramjet engine stepped combustion chamber includes a front expansion section (101), an ignition section (201), and a rear expansion section (301) connected sequentially from front to back along the incoming flow direction, with the central cavity of each section being interconnected from front to back; The combustion chamber front expansion section (101) is a conical tube with its inner diameter gradually increasing along the flow direction. The inner diameter at the inlet of the combustion chamber front expansion section (101) is... D 1. The angle between the generatrix of the cone of the front expansion section (101) of the combustion chamber and the central axis is α; the rear expansion section (301) of the combustion chamber is also a conical tube, with its inner diameter gradually increasing along the flow direction, and the inner diameter at the outlet of the rear expansion section (301) of the combustion chamber is... D 2. The angle between the conical generatrix of the rear expansion section (301) of the combustion chamber and the central axis is also α; On the inner wall of the ignition section (201), along the flow direction, an annular secondary stepped groove (203) and an annular primary stepped groove (202) are sequentially arranged from front to back; a stepped transition is adopted between the front expansion section (101) of the combustion chamber and the secondary stepped groove (203); a conical tube is used for transition between the secondary stepped groove (203) and the primary stepped groove (202), and between the primary stepped groove (202) and the rear expansion section (301) of the combustion chamber; the axial length of the secondary stepped groove (203) and the corresponding transition conical tube is... C 1. The axial length of the inner cavity of the ignition section (201) is C 2. The axial length of the stepped combustion chamber of the ramjet engine is L; several igniter interfaces (204) are evenly distributed in the circumference of the secondary stepped groove (203); the igniter interface (204) is a through hole; The inner diameter of the secondary stepped groove (203) is larger than the inner diameter of the primary stepped groove (202), and the difference in radius between the two is... H 2; The inner diameter of the first-stage stepped groove (202) is larger than the inner diameter at the outlet of the front expansion section (101) of the combustion chamber, and the difference in radius between the two is H 1; The inner diameter of the first-stage stepped groove (202) is larger than the inner diameter at the outlet of the rear expansion section (301) of the combustion chamber. D 2; The parameters satisfy the following relationship: ； The ramjet engine stepped combustion chamber is provided with two levels of annular stepped grooves on the combustion chamber, so that the incoming combustible gas mixture forms two low-speed recirculation zones, and then is ignited by the ignition section (201) to form an annularly distributed and stably burning flame. The flame amplifies the energy step by step, and finally achieves stable ignition of the combustion chamber.

2. The stepped combustion chamber of a ramjet engine according to claim 1, characterized in that, The included angle α ranges from 0.5° to 2°.

3. The stepped combustion chamber of a ramjet engine according to claim 1, characterized in that, An igniter is installed on the igniter interface (204).

4. A design method for a stepped combustion chamber of a ramjet engine, used in any one of the stepped combustion chambers of a ramjet engine according to claims 1 to 3, characterized in that, The design method includes the following: a. Design the angle between the generatrix of the cone of the front expansion section (101) of the combustion chamber and the central axis, and the angle between the generatrix of the cone of the rear expansion section (301) of the combustion chamber and the central axis; b. Design a secondary stepped groove (203) and a primary stepped groove (202) in the ignition section (201) to reduce the flow rate of the combustible mixture and form a stepped gas recirculation zone along the axial direction. Use the gas recirculation zone of the ignition section (201) as the ignition zone of the stepped combustion chamber of the ramjet engine. c. Connect the front end of the combustion chamber front expansion section (101) to the rear end of the ramjet engine isolation section. The combustion chamber front expansion section (101) is used to receive the combustible mixture formed by the mixing of fuel and air in the ramjet engine isolation section. d. Ignite the combustible mixture in the ignition section (201), converting the combustible mixture into combustion gas and stabilizing combustion; the specific steps are as follows: d1. The combustible gas mixture enters the ignition section (201) from the front expansion section (101) of the combustion chamber, forming a first-stage annular reflux zone at the first-stage stepped groove (202). The velocity of the combustible gas mixture decreases and the temperature increases in the first-stage annular reflux zone. The combustible gas mixture forms a second-stage annular reflux zone at the second-stage stepped groove (203), where the velocity decreases again and the temperature continues to rise. d2. Ignition by the igniter: The ignition energy of the igniter is transferred to the secondary stepped groove (203), igniting the combustible mixture in the secondary stepped groove (203), resulting in a ring-shaped distribution of combustion gas in the secondary stepped groove (203); the ring-shaped distribution of combustion gas in the secondary stepped groove (203) ignites the combustible mixture in the primary stepped groove (202), forming a larger area of ​​ring-shaped combustion gas, achieving a step-by-step stable amplification of energy; finally, the combustion gas surrounds the inner cavity of the ignition section (201) for continuous and stable combustion; e. In the inner cavity of the rear expansion section (301) of the combustion chamber, the combustible mixture is further burned to improve the combustion efficiency of the combustible mixture, and the combustion gas is discharged into the tail nozzle of the ramjet engine for power conversion.

Images