Patent Application
20090260343
The present invention generally relates to propellant gas generation and, more particularly, to a system and method of managing propellant gas generation by a solid propellant.
Solid propellant gas generators are used in rockets, missiles, interceptors, and various other vehicles and environments. For example, solid propellant gas generators may be used to generate propellant gas for both vehicle propulsion and direction control for missiles, munitions, and various spacecraft. A solid propellant gas generator typically includes a vessel that defines a combustion chamber within which one or more solid propellant masses are disposed. The solid propellant masses, when ignited, generate high-energy propellant gas. Depending upon the particular end-use system in which the solid gas generator is installed, the propellant gas may be supplied, or at least selectively supplied, to a rocket motor and/or reaction jets that may vary the thrust, pitch, yaw, roll or spin rate and other dynamic characteristics of a vehicle in flight, and/or to a gas turbine to generate backup power.
As is generally known, once a solid propellant mass is ignited, propellant gas generation continues until the entire mass is consumed. As is also generally known, the burn rate of a solid propellant mass may vary with the pressure in the combustion chamber. For example, if the combustion chamber pressure increases, the solid propellant burn rate increases. Conversely, if the combustion chamber pressure decreases, the propellant burn rate decreases. One way of controlling combustion chamber pressure, and thus propellant burn rate, is by controlling the effective flow area of a supply passage downstream of the combustion chamber. For example, if the effective flow area of the flow passage decreases, combustion chamber pressure increases, and vice-versa.
Various systems and methods have been developed for varying the effective flow area of a solid propellant gas generator supply passage. Such systems and methods include throttling propellant gas flow from the combustion chamber using a fixed or variable area orifice, throttling propellant gas flow from the combustion chamber via a variable position valve, and including multiple propellant grains, which are then selectively ignited. Although these systems and methods are effective, each suffers certain drawbacks. For example, the present systems and methods can significantly affect overall gas generator efficiency, and may rely on fairly complex, relatively heavy, and or relatively costly components and control systems.
Hence, there is a need for a system and method of controlling solid propellant burn rate and flexible vehicle attitude and divert control that does not significantly affect overall efficiency and/or does not rely on fairly complex, relatively heavy, and/or relatively costly components and control systems. The present invention addresses one or more of these needs.
In one embodiment, and by way of example only, a solid propellant management control system includes a vessel, a solid propellant, a plurality of reaction control valves, a throttling valve, and a controller. The vessel defines a combustion chamber. The solid propellant is disposed within the combustion chamber, and is configured to generate propellant gas upon being ignited. The reaction control valves are in fluid communication with the combustion chamber, are each coupled to receive reaction control signals, and are each responsive to the reaction control signals it receives to selectively move between a closed position and a full-open position. The throttling valve is in fluid communication with the combustion chamber and is coupled to receive throttling valve control signals. The throttling valve is responsive to the throttling control signals to move to a control position that results in a desired combustion chamber pressure. The controller is operable to selectively supply the reaction control signals and the throttling valve control signals.
In another exemplary embodiment, a method of managing propellant gas generation includes disposing a solid propellant in a vessel and disposing a plurality of reaction control valves downstream of, and in fluid communication with, the vessel. Each of the reaction control valves is movable between a closed position and a full-open position. A throttling valve is disposed downstream of, and in fluid communication with, the vessel, and is movable to a plurality of control positions. The solid propellant is ignited in the vessel to thereby generate propellant gas, and the throttling valve is moved to a control position to attain a desired propellant gas pressure.
Other independent features and advantages of the preferred solid propellant management control system and method will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. In this regard, although the systems and methods are described herein as being implemented in a vehicle, the systems and methods may also be used in energy storage and/or generation systems.
Turning first to
The reaction control valves 104 are each in fluid communication with the combustion chamber 114 via the manifold 122, and are each in fluid communication with a downstream thrust nozzle 124 (e.g., 124-1, 124-2, 124-3, . . . 124-N). The reaction control valves 104 are each coupled to receive reaction control signals from the controller 108, and are each responsive to the reaction control signals it receives to selectively move between a closed position and a full-open position to thereby prevent and allow, respectively, propellant gas flow to its associated thrust nozzle 124. It will be appreciated that the reaction control valves 104 may be implemented using any one of numerous valve types and configurations now know or developed in the future, and that the number of reaction control valves 104 may vary. Some non-limiting examples of suitable valve types include suitably configured poppet valves, pintle valves, and fluidic diverter valves. It will additionally be appreciated that the thrust nozzles 124, which may also vary in number and configuration, are preferably arranged to provide suitable attitude and divert control for the projectile body 110.
The throttling valve 106 is in fluid communication with the combustion chamber 112 via the manifold, and is in fluid communication with a downstream propellant gas flow ejector 126. The throttling valve is coupled to receive throttling valve control signals from the controller 108, and is responsive to the throttling valve control signals to move to a control position. That is, the throttling valve 106, in response to the throttling valve control signals, may be moved to a closed position, to a full-open position, or to any one of numerous valve positions between the closed and full-open positions. In the closed position, the throttling valve 106 fluidly isolates the propellant gas flow ejector 126 from the combustion chamber 114. Conversely, in any one of the open positions, the throttling valve 104 fluidly couples the combustion chamber 114 to the propellant gas flow ejector 126. Thus, if the solid propellant 116 is ignited and producing propellant gas, the control position of the throttling valve 106 may be used to control propellant gas flow to and through the gas flow ejector 126. Hence, the control position of the throttling valve 106 may concomitantly be used to control the pressure in the combustion chamber 114, and thus the burn rate of the propellant.
Before proceeding further, it is noted that the propellant gas flow ejector 126 is preferably configured such that when propellant gas is discharged from the propellant gas flow ejector 126 the attitude of the projectile body 110 is not affected. It will be appreciated that the propellant gas flow ejector 126 may be variously implemented to achieve this result. For example, as
Returning once again to
The controller 108 may be configured to implement either open loop control or closed loop control of the throttling valve 106. If it implements closed loop control, the system 100 may additionally include one or more sensors 128 (only one depicted in
As was previously noted, the position of the throttling valve 106 controls propellant gas flow rate to and through the gas flow ejector 126, and thus combustion chamber pressure, and propellant burn rate. The position of the throttling valve 106 may also be used, if needed or desired, to control the generation and shape of pressure pulses in the combustion chamber 114. As an illustrative example,
Thereafter, at time t1, the amount of thrust that is needed to propel and navigate the projectile body 110 decreases significantly. Thus, controller 108 moves the throttling valve 106 to a control position that results in the combustion chamber pressure being reduced to a pressure of P1. That is, the throttling valve 106 is moved to a more open position, relative to its position between times t0 and t1, resulting in more flow out the gas flow ejector 126. The throttling valve 106 remains in this position until time t2, at which time the flight computer 122 informs the controller 108 that more thrust is needed. In response, the controller 108 moves the throttling valve 106 to a more closed position, causing relatively less gas to flow out of the gas flow ejector 126 and combustion chamber pressure to increase to the P2 pressure.
The combustion chamber pressure is held at the P2 pressure until time t3, at which time the flight computer 122 informs controller 108 that even more thrust is needed. In response, the controller moves the throttling valve 106 to an even more closed position. As a result, even less gas flows out the gas flow ejector 126 and combustion chamber pressure increases to the P4 pressure. In accordance with this mission profile, the P4 pressure is maintained until time t4. It will be appreciated that the relative times and pressure magnitudes, and the pressure pulse shapes depicted in
In addition to the above, it is noted that in some instances the controller 108 may command all of the valves 104, 106, and 121 (if included) to open positions, or command various combinations of the valves 104, 106, 121 to open and closed positions, to control propellant burn rate, vehicle thrust, and/or maneuvering. For example, the controller 108 may command all of the reaction control valves 104 closed and the throttling valve 106 and main thrust nozzle control valve 121 (if included) opened, to maximize axial vehicle thrust. In addition, selected opposing reaction control valves 104 can be closed along with the throttling valve 106 and/or main thrust nozzle control valve 121 (if included) to maximize an attitude or divert maneuver. It will be appreciated that these are merely exemplary of numerous valve position combinations that may be implemented, and that the valve position combinations may vary depending, for example, on the types of valves that are used (e.g., fluidic valve, poppet valve, pintle valve, etc.).
The systems and methods disclosed herein provide for the selective or collective control of solid propellant burn rate, combustion chamber pressure and pulse shapes, and propellant gas flow. The systems and methods thus conserve propellant utilization, which can extend burn duration, range, and mission flexibility of projectile systems and backup power systems. The disclosed systems and methods provide increased efficiency and increased thrust control flexibility relative to current systems and methods, and do so with an overall lighter weight system.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
