SE518471C2 - Detonation device for pulse detonation motor, contains spiral for accelerating flame front of ignited fuel air mixture - Google Patents

Abstract

The combustion chamber (5) contains an acceleration path in the form of a spiral (50) for accelerating the flame front of the ignited fuel-air mixture. An Independent claim is also included for a method for generating detonations in a pulse detonation motor (PDM) using this device.

Description

: sony rasa »10 15 20 25 30 35 518 471 2. a Q a ~. | In the present invention, the necessary acceleration distance is created by forcing the burn front to accelerate in a spiral.

The invention will be described in more detail below with reference to the accompanying figures: Fig. 1 Robot with pulse detonation motor.

Fig. 2 Robot with pulse detonation motor cross-section.

F ig. 3 Work cycle of the pulse detonation motor Fig. 4 shows the work cycle air intake of the pulse motor.

Fig. 5 shows the pulse cycle supply of the pulse motor.

Fig. 6 shows the pulse cycle filling of the combustion chamber of the pulse motor.

Fig. 7 shows the operating cycle ignition of the pulse motor.

Fig. 8 shows an example of the air path through the pulse detonation motor.

Figure 1 shows a robot (1) with a payload (2), comprising i.a. steering and control unit, warhead and motor fuel, and a pulse motor (3). Figure 2 shows a cross-section of the robot (1). The pulse motor (3) comprises i.a. an air intake (4) and a combustion chamber (5). The air intake (4) in this embodiment is arranged concentrically around the payload (2) and formed with a number of guide rails or a number of adjacent spirally shaped pipes with successively decreasing pitch. Air is taken in through the air intake (4) and compressed along the way to the combustion chamber (5).

The combustion chamber (5) begins with a helical acceleration distance (50) and then merges into a straight cylindrical part (56). The acceleration distance (50) can e.g. comprise a number of guide rails or one or more adjacent helical tubes with successively increasing pitch angle. Holes, gaps or flanges can also be included in the walls of the coil to affect the mixture and cause turbulence before the flame front reaches.

Figure 3 shows an embodiment of the invention. The invention consists of an air intake (4), a combustion chamber (5), fuel supply (6) and ignition device (7). Air (40) is taken in through the air intake (4) and is passed through a spiral (41) with decreasing pitch angle, i.e. the cross-sectional areas (42) of the spiral decrease. This means that the intake air (40) is compressed. The fuel supply (6) takes place in a concentric space (51) where the fuel (60) (here it is assumed that the fuel is liquid) is sprayed in via a suction: Russian 10 15 20 25 30 35 518 471 3 nozzle pressure (61) or the like, depending on type of fuel. The fuel-air mixture continues into the combustion chamber (5). The first part of the combustion chamber (5) comprises a helical acceleration distance (50) with successively increasing pitch angle. After the acceleration distance (50), the combustion chamber ends in a straight chamber (56). At the beginning of the combustion chamber (5) there is also an ignition device (7) which ignites the fuel-air mixture when the combustion chamber (5) is full.

Figure 3 shows how the cross-sectional area (52,53,54,55) increases in the helical acceleration distance (50). The increase in area depends on the angle of inclination of the spiral and the narrowing of the payload (20). A too rapid area increase can cause an achieved detonation to return to a deflagration. The area increase in the spiral is therefore adapted to the special conditions that each fuel and fuel-air mixture exhibits.

Figures 4-7 show a duty cycle of a pulse detonation motor according to the above embodiment. In Figure 4, air (40) is taken in through the air intakes. The air is compressed by being taken in through a spiral (41) with decreasing pitch angle and thus decreasing cross-sectional area (42). In Figure 5, the air has passed the air intake (4) and the fuel injection (6) has injected fuel (60) into the compressed air. The fuel-air mixture continues to move in a spiral but now with an increasing pitch angle (Fig. 6). While mixing the fuel and air, turbulence is also created in the mixture. This is done by arranging holes, gaps or fl grooves in the spiral (50). The reason is that a turbulent mixture reaches detonation speed faster. After the fuel-air mixture has left the coil (50), it continues outside the straight part (56) of the combustion chamber. In Fig. 7, the mixture has filled the entire combustion chamber (5) and it is now the ignition that takes place. The igniter (7), which is suitably one or more spark plugs, ignites the mixture at the beginning of the combustion chamber (5). The flame front of the ignited mixture accelerates in the coil (50) and reaches detonation velocity as it leaves the coil (5). The detonation then continues through the straight part (56) of the combustion chamber at detonation speed and leaves the combustion chamber (5). When the reaction products leave the combustion chamber (5), a negative pressure is created which sucks in new air (40) through the air intake (4) and the process begins again.

Figure 8 shows an example of how air (40) is taken into the pulse detonation motor and then led into the various spirals and into the straight part of the combustion chamber. 10 518 471 _š .s ": 'I = .s".: Ï': n o o ~ en 4 Example of how the acceleration coil can be calculated. If the combustion chamber has a diameter of 15 cm, the average radius of the spiral can be set to r = 5 cm. The acceleration distance L of the spiral is: L = 2 - rr - r - N where N is the number of revolutions in the spiral. The increase of the pitch angle in the spiral is adjusted so that the detonation in the spiral is stable despite the increasing cross section of the spiral. If N is equal to 4, the acceleration distance to 125 cm is obtained. The axial length of the spiral is about 20 cm, ie. about 20% of the combustion chamber length if this is 100 cm.

Claims (11)

nn | an v ».;: 10 15 20 25 30 35 518 471 5 ø c | c c u ø o Q oc PATENT CLAIMS Pulse detonation engine (3) comprising air inlet (4) and combustion chamber (5) comprising fuel supply (6) and ignition device (7), characterized in that the combustion chamber (5) comprises an acceleration distance in the form of a spiral (50). Pulse detonation motor (3) according to claim 1, characterized in that the spiral (50) has a gradually increasing pitch angle, i.e. the cross-sectional area (52.53, 54, 55) becomes larger and larger. Pulse detonation motor (3) according to any one of claims 1-2, characterized in that the combustion chamber (5) comprises one or more spirals (50). Pulse detonation motor (3) according to one of Claims 1 to 3, characterized in that the air intake (4) comprises one or more spirals (41) with a gradually decreasing pitch angle. Pulse detonation engine (3) according to any one of claims 1-4, characterized in that the coil (50) in the combustion chamber (5) comprises a device which causes turbulence of the fuel-air mixture, e.g. holes, gaps or flanges. Pulse detonation engine according to one of Claims 1 to 5, characterized in that the fuel is a gas, e.g. acetylene or hydrogen, liquid, e.g. liquid droplets (aerosol) of aviation kerosene, or in solid form, e.g. a fine powder of boron or carbon. A method of effecting detonations in a pulse detonation engine comprising the following steps: -Supply air (40), -Supply fuel (so): m the air (40), -Mix the fuel (60) with the air (40), -Fire the fuel-air mixture, and characterized by causing the flame front of the ignited fuel-air mixture to accelerate in a spiral (50). Method according to claim 7, characterized in that the acceleration takes place in a spiral (50) with successively increasing pitch angle. A method according to any one of claims 7-8, characterized in that the flame front of the accelerating fuel-air mixture reaches detonation speed before leaving the coil (50). Method according to one of Claims 7 to 9, characterized in that compressed air is supplied to the combustion chamber (50). in that the air (40) is compressed by being led in a spiral (41) with successively decreasing Method according to claim 10, characterized by a pitch angle.