Scramjet combustion chamber without concave cavity and supporting plate and combustion stability enhancing method

Abstract

The invention discloses a scramjet combustion chamber without a concave cavity and a supporting plate and a combustion stability enhancing method, the combustion chamber comprises a combustion chamber main body and a main injection mechanism arranged on the wall surface of the combustion chamber main body, the main injection mechanism is used for injecting main fuel jet flow; the auxiliary injection mechanism is located on the upstream of the auxiliary injection mechanism and used for injecting auxiliary fuel jet flow, and plume of the auxiliary fuel jet flow forms a pneumatic type backflow area under the retarding effect of the main fuel jet flow; the ignition device is located between the main fuel jet flow and the auxiliary injection mechanism and used for igniting the auxiliary fuel in the pneumatic type backflow area, and the main flow fuel is continuously preheated and ignited while stable combustion of the auxiliary fuel is achieved. The combined jet flow combustor is applied to the field of scramjet engines, supersonic stable combustion is achieved on the basis of the pneumatic type backflow area formed through combined jet, meanwhile, the overall combustion stability is greatly enhanced through the continuous ignition and preheating effect of the pneumatic type backflow area on downstream main fuel jet flow, and combustion oscillation in the flow direction is greatly weakened.

Description

Technical Field

[0001] The present invention relates to the technical field of scramjet engines, and in particular to a scramjet combustion chamber without a cavity or a support plate, and a method for enhancing combustion stability. Background Art

[0002] Currently, scramjet engine combustion chambers mainly use two types of combustion stabilization devices: cavity and support plate.

[0003] A reentrant cavity is a non-invasive flame stabilizer with advantages such as low total pressure loss and low flow resistance. It is the most widely used flame stabilizer in supersonic airflow. The basic operating principle of the reentrant combustion stabilization process in a scramjet engine is as follows: the recirculation zone within the reentrant cavity has low flow velocity and high static temperature. Simultaneously, some upstream fuel is drawn into the recirculation zone and fully mixed with air, thus forming a stable combustion reaction zone within the reentrant cavity. Under this action, the flame propagates upward and downstream of the reentrant cavity, forming a global flame within the combustion chamber.

[0004] A strut is another common flame stabilizer besides the cavity. Taking a triangular strut as an example, the supersonic flow is compressed by the windward surface of the strut, forming two oblique shock waves. These oblique shock waves are then reflected by the combustion chamber sidewalls to form reflected shock waves. The sudden expansion of the flow path at the strut bottom results in two expansion fans and a recirculation zone immediately adjacent to the strut bottom. The two expansion fans form reattached shock waves at the tail of the recirculation zone. Studies have shown that the residence time of the fluid in the recirculation zone at the strut bottom is on the order of 1 ms, with the residence time increasing the closer to the strut axis of symmetry. Downstream of the recirculation zone is the strut wake, which contains a large number of coherent structures. Generally, chemical reactions occur primarily within the recirculation zone at the strut bottom and its downstream wake.

[0005] The recirculation zone at the bottom of the support plate is small in size and has limited flame stabilization capability. In comparison, the recirculation zone of the cavity is larger in size and has stronger flame stabilization capability. This is the main reason why cavities are more commonly used in ramjet engines. Under the impact of high-enthalpy and high-speed incoming flow, both of the above-mentioned two types of combustion stabilization devices inevitably bring about a large total pressure loss and flow resistance in the engine. In addition, due to the stagnation effect of the airflow and the local heat release concentration, the windward surface of the support plate and the inner wall of the cavity both generate a high heat flux, which brings severe tests to thermal protection. The above problems become more prominent under higher flight Mach number conditions. In addition, the introduction of the cavity device inevitably causes the engine flow path volume to increase, which brings inconvenience to the overall compact design of the aircraft. Summary of the Invention

[0006] In response to the above-mentioned deficiencies in the prior art, the present invention provides a scramjet combustion chamber without cavities or support plates and a method for enhancing combustion stability, which can effectively achieve continuous and stable combustion in the engine combustion chamber without the assistance of cavities or support plates.

[0007] To achieve the above-mentioned object, the present invention provides a scramjet combustion chamber without a cavity or a support plate, comprising a combustion chamber body and: a main injection mechanism for injecting a main fuel jet; an auxiliary injection mechanism, located upstream of the main injection mechanism, for injecting an auxiliary fuel jet, wherein the plume of the auxiliary fuel jet forms an aerodynamic recirculation zone under the obstruction effect of the main fuel jet; The ignition device is located between the main fuel jet and the auxiliary injection mechanism, and is used to ignite the auxiliary fuel in the pneumatic recirculation zone, thereby achieving stable combustion of the auxiliary fuel and continuously preheating and igniting the main fuel.

[0008] In one embodiment, the injection pressure of the main injection mechanism is greater than the injection pressure of the auxiliary injection mechanism.

[0009] In one embodiment, the injection pressure of the main injection mechanism is 2 to 4 times the injection pressure of the auxiliary injection mechanism.

[0010] In one embodiment, the injection aperture of the main injection mechanism is larger than the injection aperture of the auxiliary injection mechanism.

[0011] In one embodiment, the injection aperture of the main injection mechanism is 1 to 2 times larger than the injection aperture of the auxiliary injection mechanism.

[0012] In one embodiment, the distance between the main injection mechanism and the auxiliary injection mechanism along the flow direction is more than 3 cm to ensure stable generation of the pneumatic recirculation zone and stable combustion of the auxiliary fuel in the pneumatic recirculation zone.

[0013] To achieve the above objectives, the present invention also provides a method for enhancing combustion stability, using the above-mentioned scramjet combustion chamber.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: 1. This invention achieves supersonic stable combustion based on the aerodynamic recirculation zone formed by the combined injection of fuel jets. It does not require mechanical combustion stabilization devices such as cavities and support plates, thus reducing heat protection requirements, simplifying combustion chamber design, and reducing flow channel internal resistance. 2. The continuous ignition and preheating effect of the aerodynamic recirculation zone on the downstream main fuel jet in the present invention greatly enhances the overall combustion stability, thereby significantly weakening the combustion oscillation along the stream direction and improving the combustion effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0016] Figure 1 Schematic diagram of the structure of a scramjet combustion chamber in an embodiment of the present invention; Figure 2 Schematic diagram of the principle of a scramjet combustion chamber according to an embodiment of the present invention; Figure 3 Schematic diagram of experimental results of achieving supersonic stable combustion in a scramjet combustion chamber according to an embodiment of the present invention; Figure 4 Schematic diagram of the flow bands colored by hydrogen mass fraction in an embodiment of the present invention.

[0017] Reference numerals: combustion chamber body 1, main injection mechanism 2, auxiliary injection mechanism 3, ignition device 4, main fuel jet 5, auxiliary fuel jet 6, pneumatic recirculation zone 7.

[0018] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0021] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0022] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; it can mean mechanical connection, electrical connection, physical connection, or wireless communication connection; it can mean direct connection or indirect connection through an intermediate medium; it can mean internal communication between two elements or interaction between two elements, unless otherwise specified. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] like Figure 1 、 Figure 2 The figure shows a scramjet combustor without a cavity or support plate disclosed in this embodiment. It primarily comprises a combustor body 1, a main injection mechanism 2, an auxiliary injection mechanism 3, and an ignition device 4, located on the wall of combustor body 1. The main injection mechanism 2 is used to inject a primary fuel jet 5, while the auxiliary injection mechanism 3 is used to inject a secondary fuel jet 6 and is located upstream of the main injection mechanism 2. The main and auxiliary injection mechanisms 2 and 3 are located in the same spanwise position, so that the plume of the secondary fuel jet 6, retarded by the primary fuel jet 5, forms an aerodynamic recirculation zone 7. The ignition device 4 can be a spark plug, etc. The ignition device 4 is located between the main fuel jet 5 and the auxiliary injection mechanism 3 and corresponds to the position of the pneumatic recirculation zone 7. It is used to ignite the auxiliary fuel in the pneumatic recirculation zone 7, so that the auxiliary fuel can achieve stably combustion in the pneumatic recirculation zone 7. At the same time, the combustion heat released by the auxiliary fuel covers the windward side of the main fuel jet 5, thereby achieving continuous preheating and ignition of the mainstream fuel, and finally achieving efficient and stable combustion of the main fuel downstream.

[0025] During the specific implementation, the distance between the main injection mechanism 2 and the auxiliary injection mechanism 3 along the flow direction is more than 3 cm to ensure the stable generation of the pneumatic recirculation zone 7 and the stable combustion of the auxiliary fuel in the pneumatic recirculation zone 7.

[0026] In this embodiment, the auxiliary fuel is a highly reactive, high-calorific-value fuel, such as hydrogen, to enhance the intensity of the auxiliary fuel's combustion heat release within the pneumatic recirculation zone 7. Furthermore, to strengthen the primary fuel's blocking effect on the auxiliary fuel and thereby create a more stable pneumatic recirculation zone 7, the injection aperture of the main injection mechanism 2 is larger than that of the auxiliary injection mechanism 3, and the injection pressure of the main injection mechanism 2 is greater than that of the auxiliary injection mechanism 3. For example, the injection pressure of the main injection mechanism 2 is 2 to 4 times the injection pressure of the auxiliary injection mechanism 3, and the injection aperture of the main injection mechanism 2 is 1 to 2 times greater than that of the auxiliary injection mechanism 3.

[0027] It is worth noting that although in this embodiment Figure 1 The main injection mechanism 2 and the auxiliary injection mechanism 3 shown in the perspective shown have only one injection hole, but in the specific application process, according to the configuration of the combustion chamber (rectangular cross-section or circular cross-section), the main injection mechanism 2 and the auxiliary injection mechanism 3 can include multiple injection holes distributed in an annular array or a linear array. It is only necessary to meet the requirement that for each continuous envelope of main fuel formed by the main injection mechanism 2 in the combustion chamber, it has at least one auxiliary fuel injection hole facing upstream.

[0028] This embodiment also discloses a method for enhancing combustion stability, primarily utilizing the scramjet combustor described above. In a specific application, the injection pressures and flow rates of the main and auxiliary injection mechanisms 2 and 3 are set based on the spacing between the main and auxiliary injection mechanisms 2 and 3, respectively, within the scramjet combustor. This allows the plume of the auxiliary fuel jet 6 to form an aerodynamic recirculation zone 7 under the retarding effect of the main fuel jet 5. The auxiliary fuel within the aerodynamic recirculation zone 7 is then ignited by the ignition device 4, achieving stable combustion within the aerodynamic recirculation zone 7. Simultaneously, the heat released by the combustion of the auxiliary fuel covers the windward side of the main fuel jet 5, enabling continuous preheating and ignition of the mainstream fuel, ultimately achieving efficient and stable combustion of the main fuel downstream.

[0029] The scramjet combustion chamber without a cavity or a support plate and the method for enhancing combustion stability in this embodiment are further described below with reference to specific examples.

[0030] In this example, experiments and numerical calculations were conducted using hydrogen as the upstream auxiliary fuel and ethylene as the downstream main fuel. The hydrogen injection pressure was 1.5 MPa and the flow rate was 2.6 g / s. The downstream ethylene injection pressure was 5.0 MPa and the flow rate was 30 g / s. In the experiments and numerical simulations, the supersonic inflow had a total temperature of 1650 K and a total pressure of 1.65 MPa. Spontaneous radiation photography was used to obtain the combustion flow field structure and flame distribution. The results are as follows: Figure 3 shown.

[0031] Under the action of the auxiliary fuel jet 6, stable self-sustaining combustion is achieved without devices such as cavities and support plates. It can be seen that a relatively obvious combustion area is formed between the two jets, namely the aerodynamic recirculation area 7. Figure 4 The flow band colored by the hydrogen mass fraction shows that the hydrogen is basically completely consumed in the aerodynamic recirculation zone 7 between the two jets, confirming the stabilizing combustion effect of the aerodynamic recirculation zone 7.

[0032] The above description is only a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the scope of protection of the present invention.

Claims

1. A scramjet combustion chamber without a cavity or a support plate, characterized in that: It includes a combustion chamber body and: a main injection mechanism for injecting a main fuel jet; an auxiliary injection mechanism, located upstream of the main injection mechanism, for injecting an auxiliary fuel jet, wherein the plume of the auxiliary fuel jet forms an aerodynamic recirculation zone under the obstruction effect of the main fuel jet; The ignition device is located between the main fuel jet and the auxiliary injection mechanism, and is used to ignite the auxiliary fuel in the pneumatic recirculation zone, thereby achieving stable combustion of the auxiliary fuel and continuously preheating and igniting the main fuel.

2. The scramjet combustor without a cavity or a support plate according to claim 1, characterized in that: The injection pressure of the main injection mechanism is greater than the injection pressure of the auxiliary injection mechanism.

3. The scramjet combustor without a cavity or a support plate according to claim 2, characterized in that: The injection pressure of the main injection mechanism is 2 to 4 times the injection pressure of the auxiliary injection mechanism.

4. The scramjet combustor without a cavity or a support plate according to claim 1, characterized in that: The injection aperture of the main injection mechanism is larger than the injection aperture of the auxiliary injection mechanism.

5. The scramjet combustor without cavity and support plate according to claim 4, characterized in that: The injection aperture of the main injection mechanism is 1 to 2 times larger than the injection aperture of the auxiliary injection mechanism.

6. The scramjet combustor without a cavity or a support plate according to any one of claims 1 to 5, characterized in that: The distance between the main injection mechanism and the auxiliary injection mechanism along the flow direction is more than 3 cm to ensure the stable generation of the pneumatic recirculation zone and the stable combustion of the auxiliary fuel in the pneumatic recirculation zone.

7. A method for enhancing combustion stability, characterized in that: A scramjet combustion chamber according to any one of claims 1 to 6 is used.

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