Stair combustion chamber of ramjet engine and design method thereof

Abstract

The invention belongs to the technical field of ramjet engines, and discloses a ramjet engine stepped combustion chamber and a design method thereof. The ramjet stepped combustion chamber comprises a combustion chamber front expansion section, an ignition section and a combustion chamber rear expansion section which are sequentially connected from front to back in the incoming flow direction, and center cavities of all the sections are through front and back. An annular two-stage step groove and an annular one-stage step groove are sequentially formed in the inner wall face of the ignition section from front to back in the incoming flow direction. A plurality of igniter connectors are evenly distributed in the circumferential direction of the two-stage step groove. According to the design method, the two-stage backflow areas are formed through the two-stage stepped grooves, the flowing speed of combustible mixed gas is reduced through the stepped grooves, the combustible mixed gas can be stably combusted, the temperature of a combustion chamber of the ramjet is increased, meanwhile, the ignition reliability of the ramjet is improved, and the service life of the ramjet is prolonged. And the ignition Mach number range of various types of igniters on the ramjet engine is expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of ramjet engines, and particularly relates to a stepped combustion chamber of a ramjet engine and a design method thereof. Background Art

[0002] A ramjet engine uses oxygen obtained from the atmosphere during the climbing process as an oxidant for combustion. To promote the combustion process in the combustion chamber, since the airflow velocity entering the ramjet engine is fast and the residence time in the combustion chamber is only on the order of milliseconds, it is very difficult to achieve the mixing, ignition, and combustion of combustibles within an extremely short time. With the development of ramjet engines, the Mach number used is continuously widened, and the ignition difficulty of the combustion chamber and the stable combustion of the combustion chamber become more difficult.

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

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

[0005] The stepped combustion chamber of the ramjet engine of the invention includes a combustion chamber front expansion section, an ignition section, and a combustion chamber rear expansion section that are sequentially connected from front to back along the incoming flow direction, and the central cavities of each section communicate with each other from front to back; The combustion chamber front expansion section is a conical tube, and the inner diameter gradually increases along the incoming flow direction. The inner diameter at the inlet of the combustion chamber front expansion section is D 1, and the included angle between the conical generatrix of the combustion chamber front expansion section and the central axis is α; the combustion chamber rear expansion section is also a conical tube, and the inner diameter gradually increases along the incoming flow direction. The inner diameter at the outlet of the combustion chamber rear expansion section is D 2, and the included angle between the conical generatrix of the combustion chamber rear expansion section and the central axis is also α; On the inner wall surface of the ignition section, annular secondary stepped grooves and annular primary stepped grooves are sequentially arranged from front to back along the incoming flow direction; a step transition is adopted between the combustion chamber front expansion section and the secondary stepped grooves; a conical tube transition is adopted between the secondary stepped grooves and the primary stepped grooves, and between the primary stepped grooves and the combustion chamber rear expansion section; the axial lengths of the secondary stepped grooves and the corresponding transition conical tubes are C 1, the axial length of the inner cavity of the ignition section is C 2, the axial length of the inner cavity of the stepped combustion chamber of the ramjet engine is L; a plurality of igniter interfaces evenly distributed in the circumferential direction are arranged on the secondary stepped grooves; the igniter interfaces are through holes; The inner diameter of the secondary stepped grooves is greater than the inner diameter of the primary stepped grooves, and the radius difference between the two is H2; 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 radius difference 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; Each parameter satisfies the following relationship: 。

[0006] Furthermore, the range of the included angle α is 0.5° to 2°.

[0007] Furthermore, an igniter is installed on the igniter interface.

[0008] The design method of the stepped combustion chamber of the ramjet engine of the present invention includes the following contents: a. Design the included angle between the conical generatrix and the central axis of the front expansion section of the combustion chamber, and the included angle between the conical generatrix and the central axis of the rear expansion section of the combustion chamber to reduce the influence of the inner wall boundary layer and avoid the axial reduction of the main flow channel; b. Design a second-stage stepped groove and a first-stage stepped groove in the ignition section to reduce the flow rate of the combustible mixture gas, form a stepped gas recirculation zone along the axis, and use the gas recirculation zone in 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 gas in the first-stage stepped groove; c. Connect the front end of the front expansion section of the combustion chamber to the tail end of the isolation section of the ramjet engine. The front expansion section of the combustion chamber is used to receive the combustible mixture gas formed by the mixture of fuel and air in the isolation section of the ramjet engine; d. Ignite the combustible mixture gas in the ignition section, convert the combustible mixture gas into combustion gas and stably burn; the specific steps are as follows: d1. The combustible mixture gas enters the ignition section from the front expansion section of the combustion chamber, forms a first-stage annular recirculation zone at the first-stage stepped groove, the speed of the combustible mixture gas in the first-stage annular recirculation zone decreases, and the temperature rises; the combustible mixture gas forms a second-stage annular recirculation zone at the second-stage stepped groove, the speed decreases again, and the temperature continues to rise; d2. The igniter ignites, and the ignition energy of the igniter is transferred to the second-stage stepped groove to ignite the combustible mixture gas in the second-stage stepped groove, so that a ring-shaped distribution of combustion gas is formed in the second-stage stepped groove; the ring-shaped distribution of combustion gas in the second-stage stepped groove ignites the combustible mixture gas in the first-stage stepped groove and forms a larger range of ring-shaped distribution of combustion gas, realizing the step-by-step and stable amplification of energy; finally, the combustion gas surrounds the inner cavity of the ignition section and burns continuously and stably; e. Further burn the combustible mixture gas in the inner cavity of the rear expansion section of the combustion chamber, improve the combustion efficiency of the combustible mixture gas, and discharge the combustion gas into the tail nozzle of the ramjet engine for work conversion.

[0009] The stepped combustor of the ramjet engine and its design method of the present invention form two low-speed recirculation zones for the combustible mixture gas by arranging two-stage annularly distributed stepped grooves on the combustor, and then input a certain amount of external energy to ignite it, forming an annularly distributed and stably burning flame, gradually amplifying the energy to finally achieve stable ignition of the combustor, effectively solving the problem of stable ignition of the ramjet engine.

[0010] In short, the stepped combustor of the ramjet engine and its design method of the present invention form two recirculation zones through two-stage stepped grooves. The stepped grooves reduce the flow velocity of the combustible mixture gas, enabling the combustible mixture gas to burn stably, increasing the temperature of the ramjet engine combustor. At the same time, the ignition reliability of the ramjet engine is improved, the ignition Mach number range of various types of igniters on the ramjet engine is expanded, and it has engineering practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1a is a schematic structural diagram of the stepped combustor of the ramjet engine of the present invention; Figure 1b is a schematic structural diagram of the stepped combustor of the ramjet engine of the present invention ( Figure 1a B-B sectional view); Figure 2 is a schematic diagram of the design parameters of the stepped combustor of the ramjet engine of the present invention ( Figure 1a A-A sectional view).

[0012] In the figure, 101. Front expansion section of the combustor; 201. Ignition section; 202. First-stage stepped groove; 203. Second-stage stepped groove; 204. Igniter interface; 301. Rear expansion section of the combustor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand the 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.

[0014] Example: As Figure 1a , Figure 1b , Figure 2 shown, the stepped combustor of the ramjet engine in this embodiment includes a front expansion section 101, an ignition section 201, and a rear expansion section 301 of the combustor that are sequentially connected from front to back along the oncoming flow direction, and the central cavities of each section are continuously connected from front to back; The front expansion section 101 of the combustor is a conical tube, and its inner diameter gradually increases along the oncoming flow direction. The inner diameter at the entrance of the front expansion section 101 of the combustor isD 1. The included angle between the conical generatrix 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, and the inner diameter gradually increases along the oncoming flow direction. The inner diameter at the outlet of the rear expansion section 301 of the combustion chamber is D 2. The included 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 surface of the ignition section 201, along the oncoming flow direction, an annular secondary stepped groove 203 and an annular primary stepped groove 202 are arranged in sequence from front to back; a step transition is adopted between the front expansion section 101 of the combustion chamber and the secondary stepped groove 203; a conical tube transition is adopted 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 between 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 inner cavity of the stepped combustion chamber of the ramjet engine is L; a number of igniter interfaces 204 evenly distributed in the circumferential direction are arranged in the secondary stepped groove 203; the igniter interfaces 204 are through holes; The inner diameter of the secondary stepped groove 203 is greater than the inner diameter of the primary stepped groove 202, and the radius difference between the two is H 2; the inner diameter of the primary stepped groove 202 is greater than the inner diameter at the outlet of the front expansion section 101 of the combustion chamber, and the radius difference between the two is H 1; the inner diameter of the primary stepped groove 202 is greater than the inner diameter at the outlet of the rear expansion section 301 of the combustion chamber D 2; Each parameter satisfies the following relational expressions: .

[0015] Furthermore, the range of the included angle α is 0.5° to 2°.

[0016] Furthermore, an igniter is installed on the igniter interface 204.

[0017] The design method of the stepped combustion chamber of the ramjet engine in this embodiment includes the following contents: a. Design the included angle between the conical generatrix of the front expansion section 101 of the combustion chamber and the central axis, and the included angle between the conical generatrix of the rear expansion section 301 of the combustion chamber and the central axis, reduce the influence of the boundary layer on the inner wall surface, and avoid the axial reduction of the main flow channel; b. Design a secondary stepped groove 203 and a primary stepped groove 202 in the ignition section 201, reduce the flow velocity of the combustible mixture gas, form a stepped gas recirculation zone along the axis, and use the gas recirculation zone of the ignition section 201 as the ignition zone of the stepped combustion chamber of the ramjet engine to improve the ignition success rate of the combustible mixture gas in the primary stepped groove 202; c. Connect the front end of the front expansion section 101 of the combustion chamber to the tail end of the ramjet isolation section. The front expansion section 101 of the combustion chamber is used to receive the combustible mixture formed by the fuel and air in the ramjet isolation section. d. Ignite the combustible mixture in the ignition section 201, convert the combustible mixture into combustion gas and stably burn it. The specific steps are as follows: d1. The combustible mixture enters the ignition section 201 from the front expansion section 101 of the combustion chamber, forms a primary annular recirculation zone at the primary stepped groove 202. The velocity of the combustible mixture in the primary annular recirculation zone decreases and the temperature increases. The combustible mixture forms a secondary annular recirculation zone at the secondary stepped groove 203, the velocity decreases again and the temperature continues to increase. d2. The igniter ignites, and the ignition energy of the igniter is transferred to the secondary stepped groove 203 to ignite the combustible mixture in the secondary stepped groove 203, so that a ring-shaped distribution of combustion gas is formed 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 and forms a larger range of ring-shaped distribution of combustion gas, realizing the step-by-step and 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, further burn the combustible mixture, improve the combustion efficiency of the combustible mixture, and discharge the combustion gas into the ramjet tail nozzle for work conversion.

[0018] The above embodiments only illustrate the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A ramjet stepped combustion chamber, characterized in that, The stepped combustor of the ramjet engine includes a front expansion section (101), an ignition section (201), and a rear expansion section (301) of the combustor that are sequentially connected from front to back along the oncoming flow direction. The central cavities of each section are connected through from front to back. The front expansion section (101) of the combustion chamber is a conical tube, and its inner diameter gradually increases along the oncoming flow direction. The inner diameter at the entrance of the front expansion section (101) of the combustion chamber is D 1. The angle between the conical generatrix and the central axis of the front expansion section (101) of the combustion chamber is α. The rear expansion section (301) of the combustion chamber is also a conical tube, and its inner diameter gradually increases along the oncoming flow direction. 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 and the central axis of the rear expansion section (301) of the combustion chamber is also α. On the inner wall surface of the ignition section (201), in the oncoming flow direction, an annular secondary stepped groove (203) and an annular primary stepped groove (202) are sequentially arranged from front to back; a step transition is adopted between the front expansion section (101) of the combustion chamber and the secondary stepped groove (203); a conical tube transition is adopted 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 lengths of the secondary stepped groove (203) and the corresponding transition conical tube are C 1, the axial length of the inner cavity of the ignition section (201) is C 2, the axial length of the inner cavity of the stepped combustion chamber of the ramjet engine is L; a number of igniter interfaces (204) evenly distributed in the circumferential direction are arranged on 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 that of the primary stepped groove (202), and the radius difference between them is H 2; the inner diameter of the primary stepped groove (202) is larger than the inner diameter at the outlet of the front expansion section (101) of the combustion chamber, and the radius difference between them is H 1; the inner diameter of the primary stepped groove (202) is larger than the inner diameter at the outlet of the rear expansion section (301) of the combustion chamber D 2; Each parameter satisfies the following relational expressions: 。 2. The stepped combustion chamber of a ramjet engine according to claim 1, characterized in that, The range of the included angle α is 0.5° to 2°.

3. The stepped combustor of a ramjet engine according to claim 1, wherein An igniter is installed on the igniter interface (204).

4. A design method for a stepped combustor of a ramjet engine, which is used for the stepped combustor of a ramjet engine described in any one of claims 1 to 3, characterized in that, The described design method includes the following contents: a. Design the included angle between the conical generatrix and the central axis of the front expansion section (101) of the combustor, and the included angle between the conical generatrix and the central axis of the rear expansion section (301) of the combustor to reduce the influence of the inner wall boundary layer and avoid the axial reduction of the main flow channel. b. Design a secondary stepped groove (203) and a primary stepped groove (202) in the ignition section (201) to reduce the flow velocity of the combustible mixture gas, form a stepped gas recirculation zone along the axis, and use the gas recirculation zone in the ignition section (201) as the ignition zone of the stepped combustor of the ramjet engine to improve the ignition success rate of the combustible mixture gas in the primary stepped groove (202). c. Connect the front end of the front expansion section (101) of the combustor to the tail end of the isolation section of the ramjet engine. The front expansion section (101) of the combustor is used to receive the combustible mixture gas formed by the mixture of fuel and air in the isolation section of the ramjet engine. d. Ignite the combustible mixture gas in the ignition section (201), convert the combustible mixture gas into combustion gas and stably burn it. The specific steps are as follows: d1. The combustible mixture gas enters the ignition section (201) from the front expansion section (101) of the combustor, forms a primary annular recirculation zone at the primary stepped groove (202). The velocity of the combustible mixture gas in the primary annular recirculation zone decreases and the temperature increases. The combustible mixture gas forms a secondary annular recirculation zone at the secondary stepped groove (203), the velocity decreases again, and the temperature continues to increase. d2. The igniter ignites, and the ignition energy of the igniter is transferred to the secondary stepped groove (203) to ignite the combustible mixture gas in the secondary stepped groove (203), so that a ring-shaped distributed combustion gas is formed in the secondary stepped groove (203). The ring-shaped distributed combustion gas in the secondary stepped groove (203) ignites the combustible mixture gas in the primary stepped groove (202) and forms a larger range of ring-shaped distributed combustion gas, realizing the step-by-step stable amplification of energy. Finally, the combustion gas surrounds the inner cavity of the ignition section (201) and burns continuously and stably. e. In the inner cavity of the rear expansion section (301) of the combustor, further burn the combustible mixture gas, improve the combustion efficiency of the combustible mixture gas, and discharge the combustion gas into the tail nozzle of the ramjet engine for work conversion.

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