Patent Application
20110047961
With the development of pulse detonation combustors (PDCs) and engines (PDEs), various efforts have been made to use this technology in practical applications. An example of such a practical application is the development of a “hybrid” engine that uses a combination of both conventional gas turbine engine technology and PDE technology to maximize operation efficiency. Other examples include use in aircrafts, missiles, and rockets.
Pulse detonation combustors are used, for example, in pulse detonation engines. In pulse detonation engines, thrust is generated by the supersonic detonation of fuel in a detonation chamber. The supersonic detonation increases the pressure and temperature in the detonation chamber until it is released resulting in thrust. The detonation process is efficient since all of the charge is burned while inside the detonation chamber. As with any engine that intakes air, inlet stability is an important aspect of maintaining proper operation of a pulse detonation engine. This presents a particular challenge in pulse detonation engines, which use open inlet tubes.
The operation of pulse detonation engines creates extremely high pressure peaks and oscillations within the combustor that may travel to upstream components, and generates high heat within the combustor and surrounding components resulting in damage and malfunction of the upstream components. Consequently, various valving techniques are being developed to provide inlet control and prevent the high pressure peaks from traveling to the upstream components.
For these and other reasons, there is a need for the present invention.
A pulse detonation combustor valve assembly is provided that includes a fixed valve portion having an inlet and a reciprocating valve portion. The valve assembly is coupled to a pulse detonation combustor. The reciprocating valve portion is exterior to the fixed valve portion and coaxially aligned with the fixed valve portion. The reciprocating valve portion is arranged to reciprocate with respect to the fixed valve portion to control inlet flow through the inlet of the valve assembly.
Embodiments of the invention are better understood with reference to the following drawings. Like reference numerals represent corresponding parts.
As used herein, a “pulse detonation combustor” (PDC) is understood to mean any device or system that produces both a pressure rise and velocity increase from a series of repeated detonations or quasi-detonations within the device. A “quasi-detonation” is a supersonic turbulent combustion process that produces a pressure rise and velocity increase higher than the pressure rise and velocity increase produced by a deflagration wave. Embodiments of PDCs include a means of igniting a fuel/oxidizer mixture, for example a fuel/air mixture, and a detonation chamber, in which pressure wave fronts initiated by the ignition process coalesce to produce a detonation or quasi-detonation. Each detonation or quasi-detonation is initiated either by external ignition, such as spark discharge or laser pulse, or by gas dynamic processes, such as shock focusing, auto ignition or by another detonation (i.e. cross-fire). PDCs are used in pulse detonation engines (PDEs), for example. As used herein, “engine” means any device used to generate thrust and/or power. As used herein, “detonation” includes both detonations and quasi-detonations.
Embodiments of the present invention will be explained in further detail by making reference to the accompanying drawings in which like reference numerals indicate corresponding parts. The drawings do not limit the scope of the invention in any way.
The fixed valve portion 103 is axially aligned with the reciprocating valve 104. The shape and size of the fixed valve portion 103 and the reciprocating valve portion 104 can be determined based upon the desired performance characteristics and the application. In the exemplary embodiment, the fixed valve portion 103 and the reciprocating valve portion 104 are cylinders arranged concentrically. In addition, fuel is supplied axially from a fuel injector 110 via a passage 102a arranged in the fixed valve portion 103.
In
Actuation of the reciprocating valve portion 104 can be accomplished by any suitable means including mechanical (cam, scotch yoke, spring-mass-damper systems), pneumatic, electromagnetic, hydraulic, etc. For purposes of discussion, push-rods 106 are shown as part of an exemplary actuation device. The valve assembly 100 can be supported by any suitable support structure.
In
The reciprocating valve portion 104 reciprocates with respect to the receptacle 101b in the fixed base member 101 to periodically occlude the inlet 208 to control flow through the valve assembly. In
Each of the valve assemblies shown in
The inlet passage 302 is not limited to an annular structure, and can be formed in any manner suitable to the application. Further, the inlet passage 302 can include one or more vanes 304. The vanes 304 provide structural support to the inlet passage 302 and can be configured to induce swirl in the incoming airflow. The swirl together with the aerodynamic member 101b and the curved portion 102b serve to prevent flow separation and thus reduce aerodynamic losses. The amount of swirl and the geometry of the aerodynamic member 101b can be adjusted to improve fuel-air mixing and promote more efficient detonations.
Referring to
In the previous exemplary embodiments, the fuel injector 110 is axially aligned with the fixed valve portion 103 and the reciprocating valve portion 104. However, fuel may also be supplied downstream of the reciprocating valve portion 104 by injectors 502 arranged in the inlet passage 302, as shown in
As previously noted, the actuator mechanism for each of the embodiments discussed may be selected from any number of known actuators. Also, the reciprocating valve portion 104 and the fixed valve portion 103 can be cylindrical or cylindrical through a portion of their length. However, embodiments of the invention are not limited to a cylinder and the valve assembly can be of any shape suitable for the application.
The embodiments described above provide for the reciprocation of the reciprocating valve portion 104 to modulate the flow through the inlet with very small pressure drop. The aerodynamic member 101b prevents flow separation and minimizes aerodynamic losses.
The reciprocating valve portion 104 and the fixed valve portion 103 according to the exemplary embodiments of the present invention significantly reduce the forces and loads experienced by upstream components, which simplifies operation and extends the operational life of the system. The valve assembly enables the detonation load to be balanced radially. Very little, if any, forces will be experienced axially. Therefore, the components coupled to the valve assembly (for example, its driving mechanism) will be shielded from the damaging pressure oscillations.
The valve assembly according to embodiments of the present invention enables the inlet passage to be opened and closed quickly. In operation, the reciprocating valve portion traverses a relatively short axial distance. However, the reciprocating valve portion and the fixed valve portion can have a relatively large opening. Therefore, the physical opening of the valve assembly will change rapidly with small reciprocating movement. As a consequence, flow through the valve assembly can be optimized.
Operation of the valve assembly will be discussed in more detail. As shown in
During the upstroke, the reciprocating valve portion begins to open as the tip exits the receptacle. The valve assembly is fully open once the tip has cleared the inlet opening and is fully open for the duration of time until the tip of the reciprocating valve portion begins to occlude the inlet, as shown in
As discussed above and shown in
Additionally, depending on the desired operational performance, the rate of reciprocation of the reciprocating valve portion can be constant or it can be variable based on various performance and operational requirements. Further, the rate of reciprocation can be changed or adjusted to change the fill profile of the combustor or other device chamber to be filled to achieve the desired operation. The rate of reciprocation can be controlled by any known means, such as through the use of a computer control system, stepper motors, and the like.
As described herein, embodiments of the arrangement of the valve assembly and the inlet passage provide for an efficient filling phase with very small pressure drop, which increases engine performance and/or efficiency. The valve assembly also balances mechanical loads from combustion pressure. The symmetry of the system allows for very strong components while being lightweight.
It is noted that the above embodiments have been shown and described with respect to a single pulse detonation combustor (or device chamber). However, the concept of the present invention is not limited to single pulse detonation combustor embodiments.
It is noted that although embodiments of the present invention have been discussed above with respect to aircraft and power generation applications, the present invention is not limited to this and can be in any similar detonation/deflagration device in which the benefits of the present invention are desirable.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
