PROPERGOL IGNITION SYSTEM

Abstract

Propellant Load Ignition System The invention relates to a propellant load ignition system (10) comprising: a container (101) in which the propellant load (104) is present, the container comprising a bottom (102) and an exhaust outlet (103) opposite the bottom; and a pyrotechnic igniter (110) fixed to the bottom of the container, the igniter comprising a body delimiting an initiation chamber in which a pyrotechnic load is present, an initiator capable of initiating said load, and a shimming element for maintaining the pyrotechnic load in a predetermined position relative to the initiator, the igniter (110) being capable of ejecting the gases resulting from the combustion of the pyrotechnic load towards the propellant load (104) in order to ignite it. The invention also relates to a system for controlling the combustion of a propellant load. Figure for the abstract: Fig. 1.

Description

Title of the invention: Ignition system for a propellant charge technical field

[0001] The invention relates to the general field of ignition systems for a propellant charge. It relates in particular to a system for controlling the combustion of such a charge. Previous technique

[0002] Propellant loading ignition systems are known which include an igniter containing a pyrotechnic powder that can be ignited by an initiator located nearby. The initiation of the pyrotechnic powder generates hot gases that come into contact with the propellant loading to ignite it.

[0003] Because it is difficult to control the interaction between the initiator and the pyrotechnic powder, and because the gases from the combustion of the powder can carry particles, known systems are difficult to model and do not allow for repeatable ignition and therefore combustion of the propellant charge. These drawbacks make it difficult to control the combustion of a propellant charge, for example, to accurately determine its burning rate.

[0004] There is therefore a need for a propellant loading ignition system which does not have the aforementioned disadvantages. Description of the invention

[0005] To this end, the invention relates to an ignition system for a propellant charge comprising: - an enclosure in which the propellant charge is present, the enclosure comprising a bottom and an exhaust outlet opposite the bottom; - a pyrotechnic igniter fixed to the bottom of the enclosure, the igniter comprising a body delimiting an initiation chamber in which are present a pyrotechnic charge, an initiator capable of initiating said charge and a shimming element configured to maintain the pyrotechnic charge in a predetermined position relative to the initiator, the igniter being capable of ejecting the gases from the combustion of the pyrotechnic charge towards the propellant charge in order to ignite it.

[0006] The ignition system according to the invention includes, in particular, a shimming element which keeps the pyrotechnic charge in position in the igniter's initiation chamber, thereby ensuring greater repeatability in the ignition of the propellant loading. This ignition system is therefore particularly advantageous for controlling the combustion of a propellant loading.

[0007] In one embodiment, the pyrotechnic charge may include at least one pyrotechnic block in the form of a perforated disc centered on an axis of the pyrotechnic igniter, defining a channel leading to an outlet of the igniter. The use of at least one pyrotechnic block of the aforementioned shape further improves the repeatability of ignition. In particular, several blocks can be placed side by side centered on the same axis. The blocks can be obtained from a compacted pyrotechnic powder.

[0008] In one embodiment, the shim may include an elastic return element, for example, a spring. The use of an elastic return element makes it possible to have a low-cost igniter. Such a shim makes it possible to maintain a return force against the pyrotechnic charge during ignition. Alternatively, the shim may be a wedge.

[0009] In one embodiment, the pyrotechnic igniter may further include a flap between the pyrotechnic charge and an outlet of said igniter configured to rupture when the pressure in the initiation chamber reaches a predetermined threshold. The use of such a flap further improves the repeatability of the propellant charge ignition. In addition, the flap protects the pyrotechnic charge from external elements when the igniter is stored, thereby increasing its service life.

[0010] In one embodiment, the bottom of the enclosure may have a shoulder that defines a recess in which the igniter is tightly mounted. During ignition, the gas generated in the igniter presses it against the bottom of the enclosure, and it is held in place within the recess. This arrangement allows for simple fixing of the igniter and also enables its easy replacement after use.

[0011] In one embodiment, a sealing gasket may be present between the bottom of the enclosure and the igniter. The seal between the igniter and the bottom further improves ignition repeatability by preventing gases from escaping through the bottom of the enclosure. The gasket also provides some flexibility in the igniter's attachment to the bottom to dampen vibrations.

[0012] In one embodiment, the igniter may further include a diffuser equipped with vents to eject the gases from the combustion of the pyrotechnic charge towards the propellant charge. The diffuser may have vents distributed circumferentially around the diffuser, the diffuser having, for example, a cylindrical shape. The use of such a diffuser makes it possible to direct the hot gases uniformly towards the propellant charge, and to further improve the repeatability of the ignition.

[0013] The invention also relates to a combustion control system for a charge of propellant, comprising: an ignition system for a propellant charge such as that shown above, at least one pressure sensor present in the chamber, and a processing unit configured to calculate the burn rate of the propellant charge from the pressure measured by the pressure sensor. This control system takes advantage of the repeatability of the ignition system to accurately calculate the burn rate of a propellant charge. Brief description of the drawings

[0014] Other features and advantages of the present invention will become apparent from the description below, with reference to the accompanying drawings, which illustrate an example of an embodiment without being limiting in any way. In the figures:

[0015] [fig. 1] Figure 1 is a schematic cross-sectional view of a propellant charge combustion control system incorporating an ignition system according to an embodiment of the invention.

[0016] [fig.2] Figure 2 shows a perspective view of an igniter according to a mode of realization of the invention.

[0017] [fig.3] Figure 3 is an exploded view of the igniter of figure 2.

[0018] [fig.4] Figure 4 is a cross-sectional view of the igniter of figure 2.

[0019] [fig.5] Figure 5 is a view similar to that of Figure 1, where the igniter has been triggered.

[0020] [fig.6] Figure 6 is a perspective view of a pyrotechnic block according to a mode of realization. Description of the implementation methods

[0021] Figure 1 shows a schematic cross-sectional view of a propellant charge combustion control system 1, which includes a propellant charge ignition system 10, a pressure sensor 20 and a processing unit 30 connected in particular to the pressure sensor 20 by a cable 31.

[0022] The ignition system 10 comprises a housing 101, here cylindrical about an axis A, having a bottom 102 and an exhaust outlet 103 opposite the bottom 102. The exhaust outlet 103 is on the side opposite the bottom 102. A propellant charge 104 is present in the housing 101 on its wall. The propellant charge 104 can, for example, be poured directly into the housing using known means or introduced in the form of one or more blocks. The propellant charge 104 is generally cylindrical in shape.

[0023] The ignition system 10 further includes a pyrotechnic igniter 110 which is here tightly mounted in the bottom 102 of the enclosure 101. In particular, the bottom 102 has a shoulder 102a defining a recess 102b in which the igniter 110 is mounted. During ignition, the igniter 110 is pressed against the shoulder 102a. allowing it to be held in place in the housing 102b. A sealing gasket 105 may be present around the igniter 110 between the base 102 and the igniter 110. The igniter 110 can alternatively be screwed directly into the bottom 102 of the enclosure 101.

[0024] The ignition system 10 may further include an axial locking element 106 for the distributor 110. For example, such an axial locking element for the distributor may include a nut and a shim, suitable for exerting pressure on the initiator so as to keep it pressed against the bottom 102 of the enclosure 101. The axial locking element 106 is located on the side opposite the shoulder 102a and allows the distributor 110 to be pressed against the shoulder 102a.

[0025] Figures 2 to 4 show different views of the igniter 110 which will now be described in more detail.

[0026] The distributor 110 here has a cylindrical geometry around an axis B (which coincides with the axis A of the ignition system 10 when the distributor is mounted in said system). In this example, it comprises a body 111 having a first part 111a intended to be mounted in the base 102, and a second part 111b which is mounted in the first part 111a, for example by crimping or screwing. In this example, the first part 111a thus has a maximum diameter greater than the maximum diameter of the second part 111b. This arrangement allows for easy and inexpensive mounting, while ensuring greater reliability of the distributor 110.

[0027] The body 111 defines an initiation chamber 112 (Figure 4) in which a pyrotechnic charge 113 and an initiator 114 are present. The pyrotechnic charge 113 is composed here of a plurality of pyrotechnic blocks 113a, each in the form of a perforated disc. The pyrotechnic blocks 113a are centered on the axis B of the igniter 110 and have an external diameter substantially equal to that of the initiation chamber 112. The perforations in the pyrotechnic blocks 113a together define a channel 113b which opens into an outlet of the igniter 110. The channel 113b is centered on the axis B and located opposite the initiator 114.

[0028] In one embodiment, each pyrotechnic block 113a may be in the form of a solid disc (without a central opening) and include grooves 121 that allow the passage of gases towards the periphery of the blocks, and a gap between the blocks and the body 111 that allows the gases to reach the igniter outlet. Figure 6 shows a pyrotechnic block 113a according to this embodiment.

[0029] In this example, the body 111, and more specifically the second part 111b of the body, comprises a diffuser 115 in the form of a tube opening into the initiation chamber 112 at one end and which is closed at the other end. More specifically, in this example, the diffuser 115 is located in the extension of the channel 113b formed by the pyrotechnic blocks 113a. In the illustrated example, the internal diameter DI of the The diffuser 115 is approximately equal to the diameter D2 of the channel 113b. The diffuser 115 directs the hot gases from the combustion of the pyrotechnic charge 113 towards the propellant charge 104. The diffuser 115 includes vents 115a in the form of perforations distributed circumferentially around the diffuser 115. The axis of each vent 115a is perpendicular to axis B. Alternatively, the axis of each vent may form an angle between 0° and 90° with axis B to direct the gases from the combustion of the pyrotechnic charge in a different direction towards the propellant charge 104. Preferably, the vents 115a are directed directly towards the propellant charge. The vents 115a allow for controlled diffusion of the hot gases towards the propellant charge, thus further improving the repeatability of charge ignition.

[0030] According to the invention, the igniter 110 includes a bracing element such as a spring 116 configured to maintain the pyrotechnic charge 113 in a predetermined position relative to the initiator 114. In the illustrated example, the spring 116 bears on one side against a bottom wall 117a of the igniter and on the other side against the pyrotechnic charge 113 to press the latter against a wall 117b of the igniter 110 opposite the bottom wall 117a. The bracing element (spring 116) is arranged here around the initiator 114, which allows it not to interfere with the initiation and combustion of the pyrotechnic charge 113. Other configurations are possible; in particular, the pyrotechnic charge 113 may not be pressed directly against the wall 117b. In addition, other types of shimming elements can be used, for example a wedge.

[0031] The initiator 114 can be crimped directly into the base wall 117a, or screwed into it. The initiator 114 here includes two electrical conductors 114a to allow its activation by means of an electric current. A centering element 114b is provided to hold the initiator 114 in position within the igniter 110.

[0032] In this example, a damper 118 is positioned between the pyrotechnic charge 113 and the diffuser 115, which is configured to rupture when the pressure in the initiation chamber 112 reaches a predetermined threshold. The damper 118 can be metallic, for example, aluminum, brass, copper, or stainless steel. The damper 118 can have a thickness between 50 µm and 500 µm, depending on the material and the predetermined pressure threshold chosen.

[0033] In this example, the igniter 110 is connected to the processing unit 30 by a cable 32 connected to the conductors 114a. The processing unit 30 can then also act as a control unit for the igniter 110 and trigger it. Alternatively, a separate control unit can be used to control the ignition of the igniter 110.

[0034] The pressure sensor 20 is fixed to the bottom of the enclosure 102 and extends into the interior of the enclosure 102 to measure the pressure. The processing unit 30 can thus calculate the combustion rate of the propellant charge 104 from the pressure measurement.

[0035] Figure 5 illustrates an ignition sequence of the control system 1. Initially, the processing unit 30 sends an electric current through the cable 32 to the initiator 114, which triggers the initiator 114, igniting the pyrotechnic charge 113. The hot gases from the combustion of the pyrotechnic charge 113 increase the pressure in the initiation chamber 112 to the pressure threshold at which the gate 118 ruptures. The hot, pressurized gases can then enter the diffuser 115 and be ejected through the vents 115a towards the propellant charge 104 to ignite it. Once ignited, the propellant charge 104 burns, and the gases escape through the exhaust outlet 103 of the ignition system 10.Throughout the ignition sequence and afterwards, the pressure sensor 20 records the pressure variations in the chamber 102 as a function of time and transmits them to the processing unit 30 which can calculate the combustion rate of the propellant charge 104 accurately and repeatably.

[0036] It should be noted that to control a propellant loading, the ignition system can be positioned vertically with the exhaust outlet 103 directed upwards as illustrated in figures 1 and 4, or horizontally.

Claims

Demands

1. Ignition system (10) for a propellant charge comprising: - a container (101) in which the propellant charge (104) is present, the container comprising a bottom (102) and an exhaust outlet (103) opposite the bottom; and - a pyrotechnic igniter (110) fixed to the bottom of the container, the igniter comprising a body (111) delimiting an initiation chamber (112) in which a pyrotechnic charge (113) is present, an initiator (114) capable of initiating said charge and a shimming element (116) configured to maintain the pyrotechnic charge in a predetermined position relative to the initiator, the igniter being capable of ejecting the gases from the combustion of the pyrotechnic charge (113) towards the propellant charge (104) in order to ignite it.

2. System according to claim 1, wherein the pyrotechnic loading (113) comprises at least one pyrotechnic block (113a) having the form of a perforated disc centered on an axis (B) of the pyrotechnic igniter and which defines a channel (113b) opening to an outlet of the igniter.

3. System according to claim 1 or claim 2, wherein the shimming element (116) comprises an elastic return element.

4. System according to any one of claims 1 to 3, wherein the pyrotechnic igniter (110) further comprises a seal (118) between the pyrotechnic charge (113) and an outlet of said igniter configured to rupture when the pressure in the initiation chamber reaches a predetermined threshold.

5. System according to any one of claims 1 to 4, wherein the bottom (102) of the enclosure has a shoulder (102a) which defines a housing (102b) in which the igniter (110) is tightly mounted.

6. System according to any one of claims 1 to 5, wherein a sealing gasket (105) is present between the bottom (102) of the enclosure (101) and the igniter (110).

7. System according to any one of claims 1 to 6, wherein the igniter (110) further comprises a diffuser (115) provided with vents (115a) to eject the gases from the combustion of the pyrotechnic charge (113) towards the propellant charge (104).

8. System (1) for controlling the combustion of a propellant charge (104), comprising: an ignition system (10) for a charge of propellant according to any one of claims 1 to 7, at least one pressure sensor (20) present in the enclosure (101), and a processing unit (30) configured to calculate a combustion rate of the propellant charge (104) from the pressure measured by the pressure sensor (20).

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