JPH06108920A - Scram jet engine - Google Patents

Abstract

PURPOSE:To dissolve choke condition and the like by changing the amount of air which leaks from the forward part of a cowl and the amount of air which flows in a throat part, in response to the pressure inside a compression part. CONSTITUTION:A cowl 9 installed on the bottom surface last half part of an engine 3 is moved in longitudinal direction while being guided on rails on the bottom surfaces of side walls 4, 5, 6. The cowl 9 is driven by a cowl driving device which is not shown in figure and being arranged on the upper side of struts 7, 8, and it is moved along air flow direction. The cowl driving device is connected to a control device which is not shown in figure to receive supply of electric power from the control device. Pressure sensors are installed on the part of the compressed part sides of the side walls 4, 5, 6. Static pressure at the compressed part is detected by the pressure sensor at all times, and its information is inputted into the control device as electric signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scramjet engine, and more particularly to a technique for eliminating a choke phenomenon during operation.

[0002]

2. Description of the Related Art In recent years, as a propulsion engine for hypersonic aircraft, JP-A-2-115559 and JP-A-2-291 have been used.
As described in Japanese Patent No. 431, etc., development of a scramjet (supersonic combustion ramjet) engine is in progress. The scramjet engine allows the air taken in from the air intake (air intake) to pass through at supersonic speed inside the engine as well, and it can fly at supersonic speeds of 5 Mach or more that cannot be reached by a normal ramjet engine. Even if it is performed, the temperature of the air does not rise due to adiabatic compression, and the combustor does not melt.

[0003]

In an aircraft equipped with a conventional scramjet engine (hereinafter abbreviated as "engine"), the combustion pressure suddenly rises and the amount of air flowing from the air intake suddenly changes due to a change in the attitude of the aircraft. If it is increased to 1, the pressure (static pressure) in the throat part will rise abnormally. In that case, a choke phenomenon in which the airflow flowing into the air intake is dammed at the throat portion is often generated, and the flow velocity in the engine becomes a subsonic speed, resulting in an unstart (non-start) state. Then, due to the increase in static pressure in the throat portion, the vertical shock wave is pushed forward of the air intake, and the air intake efficiency of the air intake is reduced. As a result, the resistance increases, and the moments such as pitching and yawing change, which greatly affects the stability of the airframe.

In order to solve such a problem and restart the engine, it is necessary to eliminate the choke phenomenon. However, in the unstarted state, the engine is not started as a matter of course, so it is expected that the combustion pressure will decrease due to the control of the fuel injection amount and that the pressure at the throat part will decrease due to the decrease in the amount of inflowing air due to changes in the aircraft attitude. No, it was difficult to restart the engine. Even if it does not fall into unstart, when it is on the verge of choke, there are only methods such as lowering the combustion pressure by controlling the fuel injection amount and lowering the throat pressure by decreasing the inflowing air amount due to changes in the aircraft attitude. No, the control of the engine was very difficult.

Therefore, the present invention solves the above-mentioned problems of the prior art, and changes the amount of air overflowing from the front of the cowl and the amount of air flowing into the throat according to the pressure in the compression section, thereby maintaining the choked state. It is an object of the present invention to provide a scrumjet engine that solves such problems.

[0006]

In order to achieve the above object, the present invention provides a plurality of wedge-shaped side walls each having a cross-sectional area that decreases toward the front and the rear along the flow direction of the air taken in from the air intake. In a scramjet engine in which an air flow path composed of a compression section and a combustion section is partitioned, the upper end of the side wall is attached to the body of an aircraft, and the cowl is attached to the lower end of the side wall, the air flow through the cowl. A cowl drive device configured to move along a direction and driving the cowl, a pressure sensor for detecting static pressure in the compression section, and controlling the cowl drive device based on a detection result of the pressure sensor. It is characterized by including a control device.

[0007]

According to the present invention, when the choke phenomenon occurs or is about to occur in the engine, the static pressure in the compression portion of the air passage increases, and the value is detected by the pressure sensor. The control device controls the cowl drive device based on the detection result of the pressure sensor, and moves the cowl rearward along the air flow direction. Then, since the amount of air overflowing from the air intake increases, the amount of air flowing into the throat portion decreases, the static pressure in the throat portion decreases, and the choke phenomenon is eliminated. On the contrary, when the static pressure in the throat portion is reduced and supersonic combustion cannot be maintained, the cowl is moved forward along the air flow direction. Then, since the amount of air overflowing from the air intake decreases, the amount of air flowing into the throat portion increases, the static pressure in the throat portion rises, and supersonic combustion is restarted.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a scramjet engine according to the present invention will be described below with reference to the accompanying drawings.

In the aircraft shown in FIG. 1, the lower surface 2 of the airframe 1
Is equipped with an engine 3. As shown in FIG. 2 (enlarged view of part A in FIG. 1), the engine 3 has a shape similar to that of the side wall 6 between the left and right side walls 4 and 5 having a receding angle and the center side wall 6. Struts 7, 8 are arranged, and a cowl 9 for covering the latter half of the side walls 4, 5, 6 and struts 7, 8 is attached to the lower surfaces of the struts 7, 8.

As shown in FIG. 3, the inner surfaces of the side walls 4, 5 and 6 and the struts 7 and 8 are formed in a wedge shape along the air flow direction and the cross-sectional area decreases toward the front and the rear. . Therefore, the cross-sectional area of the air flow path 10 defined by the side walls 4, 5, 6 and the struts 7, 8 is gradually reduced at the compression portion 11 which is the first half of the stroke, and the throat portion 12 having the smallest cross-sectional area is formed. At the boundary, the combustion section 13 will be gradually expanded in the latter half of the stroke.
Four pressure sensors 14 are attached to each of the side surfaces of the side walls 4, 5, 6 on the side of the compression unit 11. In the figure,
Reference numeral 15 is an oblique shock wave generated at the tips of the side walls 4, 5, 6 and the struts 7, 8.

As shown in FIG. 4, the cowl 9 has a side wall 4,
The rails 16 arranged on the lower surfaces of the rails 5 and 6 guide the rails to move back and forth. Inside the machine body 1, as shown in FIG. 5 (a sectional view taken along line BB in FIG. 3), the servo motor 17, the ball screw shaft 19 coupled to the rotary shaft 18 of the servo motor 17, and the ball screw shaft 19 are screwed together. A mating nut 20 is provided. The nut 20 is connected to the cowl 9 via a drive plate 22 penetrating a guide groove 21 formed in the struts 7 and 8, and constitutes a cowl drive device. The servo motor 17 is connected to the control device 23 and receives power supply from the control device 23. In the state of FIGS. 4 and 5, the cowl 9 is in a so-called nominal position in which the front edge of the cowl 9 coincides with the apex a of the throat portion 12 (shown by a broken line in the drawings).

On the other hand, as shown in FIG. 5, a linear encoder 24 is provided behind the ball screw shaft 19 to detect the front and rear position of the nut 20 and inform the control device 23 of the information as an electric signal. input. Further, the pressure sensor 14 described above constantly detects the static pressure of the compression unit 8 and inputs the information to the control device 23 as an electric signal.

The operation of this embodiment will be described below.

In this engine 3, supersonic air taken into the air passage 10 from the air intake 25 at its front end is dynamically compressed in the compression portion 11, and thereafter, in the combustion portion 13, a fuel injection device not shown. Fuel is injected from and burned continuously. Then, a high-temperature gas having a large energy is generated, which is expanded to the atmospheric pressure so as to have a hypersonic speed and ejected from the nozzle 26 which is the rear end of the engine 3.

By the way, when the combustion pressure is suddenly increased during the operation of the engine 3 or the amount of air flowing in from the air intake is suddenly increased due to a change in the attitude of the airframe, as described above, the static pressure in the throat portion is increased. Rises abnormally. As a result, as shown in FIGS. 6 and 7, a choke phenomenon occurs in which the air flow taken into the air flow path 10 is blocked by the throat portion 9. At this time, the overflowed air flows out from the front of the cowl 9 to the lower part, and at the same time, the static pressure in the compression section 11 also rises.

Then, in this embodiment, the static pressure in the compression section 11 of each air passage 10 is detected by the pressure sensor 14, and the information is input to the control device 23. The pressure sensor 1
Since four 4 are provided for each compression unit 11, the average value of the input information is calculated in the control device 23, and the influence of partial pressure abnormality or erroneous detection of the pressure sensor 14 is considered. Exclude. Next, in the control device 23, the required movement amount of the cowl 9 is calculated or the control map is searched according to the input static pressure value.

When the required movement amount of the cowl 9 is obtained, the control device 23 then drives the servo motor 17 to retract the cowl 9 as shown in FIG. Then cowl 9
The amount of air overflowing from the front of the vehicle increases, and as a result, the choke phenomenon is eliminated. At this time, the control device 2
In 3, the servo motor 17 is feedback-controlled based on the information input from the linear encoder 24 so that the actual movement amount of the cowl 9 matches the required movement amount.

When the choke phenomenon is eliminated and the air again passes through the air passage 10 at supersonic speed, the compression unit 1
The static pressure within 1 naturally drops. When the control device 23 detects this from the information from the pressure sensor 14, the control device 23 then drives the servo motor 17 in the opposite direction to the previous one to return the cowl 9 to the original position and restart the engine 3. In this embodiment, since the cowl 9 is moved by the servo motor 17, the change in the amount of air flowing into the throat portion 12 can be made continuous, and the choked state can be eliminated while keeping the internal flow of the engine stable. it can.

On the other hand, when the static pressure in the throat portion 12 is reduced and supersonic combustion cannot be maintained, the control device 23 moves the cowl 9 in the air flow direction according to the static pressure value input from the pressure sensor 14. Move forward along. Then, the amount of air overflowing from the front of the cowl 9 decreases, and the throat portion 1
The static pressure of 2 rises and supersonic combustion is restarted.

The inventors conducted a high-speed wind tunnel test at a speed of 4 Mach using the models shown in FIGS. 9 and 10 to find the wall surface C _P (static pressure coefficient) of the engine side wall. In these figures, 27 and 28 are side walls and 29 is a strut for air injection. Further, 30 is an upper plate corresponding to the lower surface of the machine body, and 31 is a cowl that moves back and forth. Air corresponding to the fuel of the actual machine can be injected from the strut 29 to perform a simulation when the combustion pressure rises. Further, the cowl 31 can be moved back and forth by 20 mm from the nominal position.

As a result of the test, when the air injection from the strut 29 is not performed, it is confirmed that the engine is started without falling into the choked state even at the nominal position as shown in FIG. Further, when air is injected from the strut 29, as shown in FIG. 12, the chowl 31 falls into the choke state at the nominal position, but the cowl 31 is 20 mm
It was confirmed that the choke state was resolved by retracting. The flow direction distances in FIGS. 11 and 12 are expressed with the distance from the tips of the side walls 27, 28 to the throat apex a being 100%.

Above, the description of the concrete embodiment is completed.
Aspects of the invention are not limited to this example. For example, the cowl drive device may be a single hydraulic cylinder, or may be a combination of an electric motor and a link mechanism. A simple device such as an amplifier may be used as the control device, or the number of pressure sensors for one compression unit may be other than four.

[0023]

As is apparent from the above description, according to the present invention, the cowl, which is a constituent element of the scramjet engine, can be moved back and forth, and the cowl can be moved according to the static pressure in the compression portion of the air passage. Since the vehicle is moved in the front-rear direction, when a choke phenomenon occurs in the engine during operation and the engine is unstarted, the cowl is retracted to increase the amount of air overflowing from the compression unit. Then, the amount of air flowing into the throat portion is reduced, the static pressure in the throat portion is reduced, the choke phenomenon is eliminated, and the engine can be restarted. On the contrary, when the static pressure in the throat portion decreases and supersonic combustion cannot be maintained, the cowl is advanced to reduce the amount of air overflowing from the compression portion. Then, the amount of air flowing into the throat portion increases, the static pressure in the throat portion increases, and supersonic combustion can be resumed.

[Brief description of drawings]

FIG. 1 is a perspective view showing a hypersonic aircraft.

FIG. 2 is an enlarged view of part A in FIG.

FIG. 3 is a cross-sectional view showing an embodiment of a scramjet engine according to the present invention.

FIG. 4 is a side view of the same.

5 is a sectional view taken along line BB in FIG.

FIG. 6 is a cross-sectional view showing a choked state in the example.

FIG. 7 is a side view of the same.

FIG. 8 is a side view showing an operating state of the cowl in the embodiment.

FIG. 9 is a cross-sectional view showing a model used for a high-speed wind tunnel test.

FIG. 10 is a side view of the same.

FIG. 11 is a graph showing the results of a high speed wind tunnel test.

FIG. 12 is a graph showing the results of a high speed wind tunnel test.

[Explanation of symbols]

 1 Airframe 3 Scrumjet Engine 4, 5, 6 Sidewall 7, 8 Strut 9 Cowl 10 Air flow path 11 Compressor 12 Throat 13 Combustion 14 Pressure sensor 17 Servomotor 19 Ball screw shaft 20 Nut 23 Controller 24 Linear encoder 25 Air intake

Claims (1)

[Claims] 1. An air flow path composed of a compression section and a combustion section is defined by a plurality of wedge-shaped side walls whose cross-sectional area decreases toward the front and the rear along the flow direction of the air taken in from the air intake. , A scrumjet engine having the upper end of the side wall attached to an aircraft body and the cowl attached to the lower end of the side wall, configured to move the cowl along the air flow direction and drive the cowl. A scrumjet engine, comprising: a cowl drive device, a pressure sensor that detects static pressure in the compression portion, and a control device that controls the cowl drive device based on a detection result of the pressure sensor.