JPH06280679A - Combustor and its flame holding method - Google Patents

Abstract

(57) [Abstract] [Purpose] With regard to a combustor and its flame holding method, it promotes combustion and improves thrust while avoiding thermal blockage and ensuring a sufficient injection moment. [Structure] A strut 11 is provided in a duct 1 in which a supersonic air flow 4 is formed, and a subsonic region 5 formed in the subsequent flow.
A combustor 10 for holding flames in a strut 1
1, a shock wave forming means 12 for making a shock wave 17b incident on the subsonic region 5 is disposed, and the shock wave 17b causes a pressure increase in the subsonic region 5 to generate a supersonic air flow 4
Expand the ratio of subsonic region 5 in the area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustor used in an engine of an aircraft flying at supersonic speed and a flame holding method thereof.

[0002]

2. Description of the Related Art In recent years, a scramjet engine has been developed as an engine for aircraft flying at supersonic speed. Since the scramjet engine is an engine that compresses air by ram pressure when flowing in at high speed, its structure is simple, and further, combustion efficiency can be improved with increase in flight speed. It is attracting attention as an engine for supersonic aircraft.

Conventionally, as a combustor used in a scramjet engine, for example, as shown in FIG. 2, one having a rearward facing step 2 formed on a wall surface 1a of a cylindrical duct 1 having a rectangular cross section, and FIG. As shown in, duct 1
There is a structure in which a strut 3 that is a columnar member that connects the opposite surfaces is arranged.

In the structure having the rearward facing step 2, when supersonic air is circulated in the duct 1, the supersonic air flow 4 is separated in the wake of the step 2 in the subsonic state. A region 5 (hereinafter referred to as a subsonic region) is formed, and further, a region 6 (hereinafter referred to as a recirculation region) in which air locally circulates is formed therein. By injecting fuel into the recirculation region 6 and igniting the fuel, the combustion state can be maintained in the subsonic region 5.

As a method of jetting fuel into the combustor 7 having the above-described structure, a method of jetting fuel perpendicularly to the supersonic air flow 4 from the wall surface 1a of the duct 1 arranged at the backflow position of the backward step 2, There is a method in which the jet is jetted in parallel to the supersonic airflow 4 from the surface of the rearward facing step 2 which is arranged perpendicular to the supersonic airflow 4 toward the rear.

According to the first method, since the supersonic air flow 4 is agitated by the ejected fuel, the recirculation region 5 is expanded and the air and the fuel are efficiently mixed, so that the combustion is promoted. Will be. However, when the flight Mach number is low, combustion is rapidly performed, so that the pressure inside the duct 1 excessively rises, a strong shock wave appears, and the supersonic air flow 4 is impaired ( Hereinafter, it will be referred to as thermal blockage). When thermal blockage occurs, the air cannot be sufficiently sucked into the engine, and the thrust is significantly reduced. Further, even during flight at a high Mach number, there is an inconvenience that the injection moment by the jet flow ejected from the combustor 7 cannot be utilized as thrust.

According to the second method, the disadvantages of the above method are improved, but on the other hand, the fuel is supersonic air flow 4
The fuel is not satisfactorily mixed with the air because it is ejected without disturbing the recirculation region 6, and the recirculation region 6 is not expanded, so that the combustion state is maintained (hereinafter referred to as flame holding property). There is a problem that it cannot be improved.

Further, in the combustor 7 of FIG. 3, the supersonic air flow 4 is split into two by arranging the acute angle portion 3a of the strut 3 having a wedge-shaped cross section toward the upstream side.
By separating at the trailing edge 3b of the strut 3, the subsonic region 5 and the recirculation region 6 are formed in the wake of the strut 3. Then, the fuel is ejected from the fuel nozzle 8 provided on the rear end surface 3c of the strut 3 into the recirculation region 6 to mix the air and the fuel to improve the flame holding property.

[0009]

This combustor 7 is basically the same as the second method of the combustor 7 provided with the backward facing step 2 shown in FIG. 2, but the injection by the jet flow from the combustor 7 is performed. The moment can be obtained, and there is no inconvenience of causing thermal blockage. However, in the subsonic region 5, the width is gradually reduced from the rear end surface 3c of the strut 3 toward the downstream of the supersonic airflow 4, and the supersonic airflow 4 is reduced.
However, since a parallel flow is formed, it is difficult to efficiently mix air and fuel, and thrust cannot be sufficiently generated by combustion.

The present invention has been made in view of the above circumstances, and a combustor capable of promoting combustion and improving thrust while avoiding thermal blockage and ensuring a sufficient injection moment. The purpose is to provide a method for holding the flame.

[0011]

In order to achieve the above object, the present invention proposes the following three means. The first means comprises a strut which traverses the supersonic air flow is disposed in a duct in which the supersonic air flow is formed, and combustion for flame holding in a subsonic region formed behind the strut. A combustor is proposed in which a shock wave forming means for generating a shock wave and for making the shock wave enter the subsonic region is provided on the side of the strut. A second means is that the strut is formed in a substantially wedge-shaped cross-sectional shape having an acute angle portion on the upstream side of the supersonic air flow and gradually reducing the channel cross-sectional area of the duct toward the downstream side and then rapidly expanding it. At the same time, the rear end face is provided with a recess opening downstream, and the recess is provided with a fuel injection port for ejecting fuel in the subsonic range and an ignition plug for igniting the injected fuel. At the same time, a combustor is proposed in which a communication hole is formed which penetrates the strut and communicates the recess with the supersonic airflow. Further, the third means proposes a flame holding method for a combustor in which a shock wave is injected into the subsonic region when performing combustion in the subsonic region formed inside the supersonic air flow.

[0012]

With the combustor according to the first aspect of the present invention, the supersonic airflow formed in the duct is provided with the struts that traverse the supersonic airflow. A sonic velocity region is formed, and combustion is performed in the subsonic velocity region. Then, when the shock wave generated by the shock wave forming means provided on the side of the strut is incident on the subsonic region, the pressure in the subsonic region is increased as the pressure in the wake of the shock wave increases. As a result, the subsonic range is expanded. Further, according to the combustor according to the second means, the supersonic air flow formed in the duct is diverted by the acute-angled portion of the strut having the substantially wedge-shaped cross section, and is gradually reduced in the duct having the flow passage cross-sectional area. Distributed. Then, by causing separation in the flow at the trailing edge of the strut, a subsonic region is formed in the wake of the strut. On the rear end surface of the strut, a recess opening downstream is formed, and since a communication hole penetrating the strut and communicating with the supersonic air flow is formed in the recess, the supersonic air flow is passed through the communication hole. Is partially taken into the recess, and the fuel injected from the fuel injection port and the air are premixed. At the rear end surface of the strut, the flow area of the duct is suddenly expanded, so expansion waves are generated, and the pressure in the subsonic region and the recess becomes lower compared to the supersonic airflow. . Due to this pressure difference, air is taken into the recess through the communication hole, and premixing is promoted. Further, according to the flame holding method for the combustor according to the third means, the shock wave is incident on the subsonic region formed in the supersonic air flow, so that the subsonic region is not stirred and the subsonic region is not stirred. Can be expanded, and combustion of the fuel performed within the subsonic speed will be promoted.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a combustor according to the present invention will be described below with reference to FIG. In this embodiment, the same parts as those of the conventional example shown in FIGS. 2 and 3 are designated by the same reference numerals to simplify the description. The combustor 10 of this embodiment is
This is common to the conventional example shown in FIG. 3 in that one strut 11 is arranged in the duct 1 having a rectangular cross section. However, the combustor 10 of the present embodiment has the strut 1
1 and a reentrant portion for deflecting the supersonic airflow 4 flowing along the wall surface 1a toward the inside of the duct 1 on the wall surface 1a of the duct 1 arranged on the side of the strut 11. 12 (shock wave forming means) is formed, which is different from the conventional example.

The strut 11 arranged in the combustor 10 of this embodiment is a columnar member having an isosceles triangular wedge-shaped cross section, and the acute angle portion 11a is directed to the upstream side and the acute angle portion 11a is formed. The vertical line from is the wall surface 1a of the duct 1.
It is arranged at a substantially central position of the duct 1 so as to be parallel to, and is formed so as to connect the one side surface of the duct 1 facing each other. On the rear end surface 11b of the strut 11, a recess 13 (recess) that opens toward the wake side is formed.
Is formed over the entire length in the longitudinal direction.

The recess 13 is located behind the strut 11 with respect to the supersonic air flow 4 and is also strut 1.
By making the side surface 11c of 1 into a partition, the rear edge 11 of the strut 11 is not affected by the supersonic air flow 4.
The supersonic air flow 4 separated by d forms a region in which the supersonic air flow 4 is settled therein, that is, a part of the recirculation region 6. The recess 13 is provided with a fuel ejection port 14 for ejecting the fuel that has circulated inside the strut 11 into the recess 13, and an ignition plug 15 arranged in the vicinity of the fuel ejection port 14. At the same time, a communication hole 16 that penetrates the strut 11 and communicates with the side surface of the strut 11 is formed. The communication hole 16 is, for example,
A plurality of struts 11 are arranged at intervals in the longitudinal direction so that a part of the supersonic airflow 4 can be taken into the recess 13.

The recess 12 is, for example, a strut 1.
The wall surface 1a of the duct 1 arranged at the lateral position of 1 is formed by forming a step portion for reducing the flow passage area. That is, by forming the front surface of the stepped portion as the inclined surface 12a that gradually reduces the flow passage area along the longitudinal direction of the duct 1, the boundary position between the inclined surface 12a and the duct 1 wall surface 1a located in front of the inclined surface 12a. The concave corner portion 12 is formed on the bottom. Then, the oblique shock wave 17b formed by the concave corner portion 12 can be made incident on the subsonic region 5 behind the strut 11 formed obliquely rearward thereof.

The case of using the combustor 10 thus constructed will be described below. When the flight speed of the aircraft equipped with the combustor 10 becomes supersonic, the supersonic airflow 4 is formed in the duct 1. The supersonic air flow 4 is divided into two by the acute-angled portion 11a of the tip of the strut 11 arranged in the duct 1, and each of the supersonic air flow 4 is formed in a side wall of the strut 11 that gradually decreases in diameter. After being inserted, the trailing edge 1 of the strut 11
The flow path is suddenly expanded by opening at the 1d position. At this time, the two supersonic airflows 4 cannot be immediately merged, and each of the supersonic airflows 4 has a trailing edge 11 of the strut 11.
The strip-shaped subsonic region 5 is formed in the wake of the strut 11 by being separated at d. Also, the subsonic region 5
In the vicinity of the strut 11 and inside the recess 13,
A recirculation zone 6 in which air circulates is formed. Then, the fuel and the air are mixed by injecting the fuel into the recirculation region 6, and the ignition is easily performed by the operation of the spark plug.

In this case, in the acute angle portion 11a of the strut 11 and the concave angle portion 12 of the duct 1, the supersonic air flow 4 formed in parallel to the wall surface 1a of the duct 1 has a side surface of the strut 11. Since it is deflected by 11c and the inclined surface 12a of the stepped portion, diagonal shock waves 17a and 17b directed diagonally rearward are formed. Since the oblique shock waves 17a and 17b are compression waves accompanying the reduction of the flow passage area, the pressure behind them is increased. In particular, in the combustor 10 of the present embodiment, the oblique shock wave 17b formed by the concave portion 12 is arranged so as to be incident on the subsonic region 5 formed in the wake of the strut 11, A pressure rise is generated in the subsonic region 5. Then, when the pressure in the subsonic region 5 rises, the pressure in the entire subsonic region 5 rises, and as a result, the proportion of the subsonic region 5 in the duct 1 increases. . Along with this, the recirculation region 6 formed in the subsonic region 5 is also expanded, so that the mixing property of air and fuel is improved, and the flame holding property of combustion is improved. Become.

At the trailing edge 11d of the strut 11, since the flow passage area is rapidly expanded, the trailing edge 11d is formed.
The expansion wave 18 is formed obliquely rearward from d. The expansion wave 18 lowers the pressure behind the expansion wave 18, so that the expansion wave 18 is disposed between the regions arranged in front of and behind the expansion wave 18.
A pressure difference occurs between the front supersonic airflow 4 and the recess 13. Due to this pressure difference, a part of the supersonic air flow 4 is taken into the recess 13 through the communication hole 16 provided in the strut 11 so as to be sucked into the recess 13 and is converted into fuel before combustion in the recirculation region 6. The mixed air can be efficiently supplied.

As described above, according to the combustor 10 of this embodiment, the expansion wave 1 formed on the trailing edge 11d of the strut 11 is expanded.
8 to promote premixing in the recess 13 to improve the mixing property of the fuel and air in the recirculation zone 6, and the shock wave 17b to the subsonic zone 5 formed behind the strut 11. Is injected to expand the subsonic region 5 in which fuel can burn and the recirculation region 6 inside thereof, it is possible to efficiently generate thrust due to combustion of fuel. Moreover, since the supersonic airflow 4 is not agitated when the subsonic region 5 is expanded, there is no risk of unnecessarily damaging the injection moment, and sufficient thrust can be secured even during flight at a high Mach number.

The following techniques can be adopted in the combustor 10 and the flame holding method thereof according to the present invention. The strut 11 is provided at one central position of the duct 1, but instead of this, a plurality of struts 11 arranged at intervals are adopted. Although the shock wave forming means 12 has a concave corner portion, instead of this, a wedge-shaped cross-sectional member having an acute corner portion 11a similar to the strut 11 should be used. When a plurality of struts 11 are arranged, use the acute-angled portions 11a of the adjacent struts 11 as the shock wave forming means 12. The strut 11 has an isosceles triangular wedge-shaped cross-sectional shape, but instead of this, any outline having an acute angle portion 11a for deflecting the supersonic air flow 4 and capable of forming the subsonic region 5 Have a wedge-shaped cross section. Although the spark plug 15 is provided in the recess 13,
Instead, it should be arranged at an arbitrary position in the recirculation zone 6.

[0022]

As described above in detail, in the combustor according to the first means of the present invention, the struts are provided in the duct in which the supersonic air flow is formed, and in the subsonic region formed in the subsequent flow. In the combustor for holding flame, the shock wave forming means for injecting the shock wave into the subsonic region is arranged on the side of the strut, and therefore, the following effects are achieved. By increasing the pressure in the subsonic region by the incident shock wave and expanding the subsonic region, the combustible region of the fuel can be expanded and the thrust due to combustion can be efficiently extracted. Since the subsonic range can be expanded without agitation of the supersonic air flow, the injection moment is not unnecessarily impaired, and the stall of the supersonic air flow due to thermal blockage does not occur. In a wide range of flight speeds from low Mach number to high Mach number, sufficient thrust can be secured. Further, in the combustor according to the second means of the present invention, the strut has an acute angle portion on the upstream side of the supersonic air flow, and the flow passage cross-sectional area of the duct is gradually reduced toward the downstream and then rapidly expanded. In the concave portion that is formed in a substantially wedge-shaped cross-section and that opens downstream in its rear end surface, a fuel injection port that ejects fuel in the subsonic range, a spark plug that ignites the injected fuel, and a strut are provided. Since there is provided a communication hole penetrating therethrough to communicate the recess with the supersonic air flow, in addition to the effect of the combustor according to the first means, the expansion wave generated at the trailing edge of the strut causes the supersonic air to flow. There is an effect that a pressure difference is generated between the flow and the inside of the recess to promote the intake of air into the recess and improve the mixing property of the fuel and the air. Furthermore, in the flame holding method for the combustor according to the third means of the present invention, when the combustion is performed in the subsonic region formed inside the supersonic airflow, a shock wave is incident on the subsonic region. Therefore, by expanding the subsonic region by increasing the pressure due to the shock wave, the region in which fuel burns is expanded without stirring the supersonic air flow, and combustion efficiency is improved while avoiding thermal blockage and reduction in injection moment. There is an effect that it can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a combustor according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a conventional example of a combustor having rearward facing steps.

FIG. 3 is a longitudinal sectional view showing a conventional example of a combustor having struts.

[Explanation of symbols]

 1 Duct 4 Supersonic Air Flow 5 Subsonic Region 6 Recirculation Region 10 Combustor 11 Strut 11a Sharp Corner 11b Rear End Face 12 Recessed Corner (Shock Wave Forming Means) 13 Recess (Concave) 14 Fuel Injection Port 15 Spark Plug 16 Communication Hole 17a Oblique shock wave 17b Oblique shock wave (shock wave) 18 Expansion wave

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Niioka 5-8-2 Otemachi, Natori City, Miyagi Prefecture (72) Hideaki Kobayashi 1-3-2 Mikamimine, Taihaku-ku, Sendai City, Miyagi Prefecture

Claims (3)

[Claims] 1. A combustor in which struts are disposed in a duct in which a supersonic air flow is formed so as to traverse the supersonic air flow, and a flame is maintained in a subsonic region formed in the wake of the strut. A combustor, characterized in that a shock wave forming means for generating a shock wave and for making the shock wave incident on the subsonic region is disposed laterally of the strut. 2. The strut is formed in a substantially wedge-shaped cross-sectional shape in which an acute-angled portion is arranged on the upstream side of the supersonic air flow, and the flow passage cross-sectional area of the duct is gradually reduced toward the downstream side and then rapidly expanded. At the same time, the rear end face is provided with a recess opening downstream, and the recess is provided with a fuel injection port for injecting fuel into the subsonic region and an ignition plug for igniting the injected fuel. At the same time, the combustor according to claim 1, characterized in that a communication hole is formed through the strut for communicating the recess with the supersonic airflow. 3. A flame holding method for a combustor, characterized in that when a combustion is carried out in a subsonic region formed inside a supersonic air flow, a shock wave is injected into the subsonic region.