Patent Application
20120192546
The present application relates generally to pulse detonation turbine engines and more particularly relates to a pulse detonation turbine engine with a catalytic converter positioned downstream of one or more pulse detonation combustors to minimize or reduce undesirable emissions therein.
Recent developments with pulse detonation combustors and engines have focused on practical applications such as generating additional thrust/propulsion for aircraft engines and to improve overall performance in ground-based power generation systems. Known pulse detonation combustors and engines generally operate with a detonation process having a pressure rise as compared to conventional engines operating with a constant pressure deflagration. Specifically, air and fuel are mixed within a pulse detonation chamber and ignited to produce a combustion pressure wave. The combustion pressure wave transitions into a detonation wave followed by combustion gases that produce thrust as they are exhausted from the engine. As such, pulse detonation combustors and engines have the potential to operate at higher thermodynamic efficiencies than generally may be achieved with conventional deflagration-based engines.
Undesirable emissions, however, currently may be an issue for any combustion process other than deflagration. Even when the chemical reactions reach equilibrium in a detonative combustion process, undesirable emissions such as carbon monoxide (CO) and nitrogen oxides (NOx) may be present at levels higher than produced by a comparable constant pressure combustor. Moreover, these emissions generally reduce the combustion efficiency of the pulse detonation combustor in a pulse detonation turbine engine. A reduction in levels of emissions such as carbon monoxide and nit oxides thus is an issue in the adaptation of a pulse detonation turbine engine as an energy/propulsion conversion device.
There is thus a desire for improved pulse detonation turbine engine designs. Such improved designs preferably may limit undesirable emissions while maintaining or increasing overall system efficiency. Moreover, such designs preferably may involve minimal downtime and maintenance costs.
The present application thus provides a pulse detonation turbine engine. The pulse detonation turbine engine may include one or more pulse detonation combustors to produce a flow of combustion gases, a turbine positioned downstream of the pulse detonation combustors such that the flow of combustion gases drives the turbine, and a catalytic converter positioned downstream of the pulse detonation combustors such that the flow of combustion gases passes therethrough.
The present application further provides a method of minimizing or eliminating one or more undesirable emissions in a flow of combustion gases in a pulse detonation turbine engine. The method may include the steps of generating the flow of combustion gases with the undesirable emission therein in one or more pulse detonation combustors, driving a turbine with the flow of combustion gases, and passing the flow of combustion gases through a catalytic converter to minimize or eliminate the undesirable emissions contained therein.
The present application further provides a pulse detonation turbine engine. The pulse detonation turbine engine may include one or more pulse detonation combustors for producing a flow of combustion gases, a high pressure turbine positioned downstream of the pulse detonation combustors such that the flow of combustion gases drives the high pressure turbine, a catalytic converter positioned downstream of the high pressure turbine such that the flow of combustion gases passes therethrough, and a low pressure turbine positioned downstream of the catalytic converter such that heat produced in the catalytic converter drives in part the low pressure turbine.
These and other features and improvements of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
As used herein, the term “pulse detonation combustor” refers to a device or a system that produces both a pressure rise and a velocity increase from the detonation or quasi-detonation of a fuel and an oxidizer. The pulse detonation combustor may be operated in a repeating mode to produce multiple detonations or quasi-detonations within the device. A “detonation” may be a supersonic combustion in which a shock wave is coupled to a combustion zone. The shock may be sustained by the energy release from the combustion zone so as to result in combustion products at a higher pressure than the combustion reactants. A “quasi-detonation” may be a supersonic turbulent combustion process that produces a pressure rise and a velocity increase higher than the pressure rise and the velocity increase produced by a sub-sonic deflagration wave, i.e., detonation and fast flames. For simplicity, the terms “detonation” or “detonation wave” as used herein will include both detonations and quasi-detonations.
Exemplary pulse detonation combustors, some of which will be discussed in further detail below, include an ignition device for igniting a combustion of a fuel/oxidizer mixture and a detonation chamber in which pressure wave fronts initiated by the combustion coalesce to produce a detonation wave. Each detonation or quasi-detonation may be initiated either by an external ignition source, such as a spark discharge, laser pulse, heat source, or plasma igniter, or by gas dynamic processes such as shock focusing, auto-ignition, or an existing detonation wave from another source (cross-fire ignition). The detonation chamber geometry may allow the pressure increase behind the detonation wave to drive the detonation wave and also to blow the combustion products themselves out an exhaust of the pulse detonation combustor. Other components and other configurations may be used herein.
Various combustion chamber geometries may support detonation formation, including round chambers, tubes, resonating cavities, reflection regions, and annular chambers. Such combustion chamber designs may be of constant or varying cross-section, both in area and shape. Exemplary combustion chambers include cylindrical tubes and tubes having polygonal cross-sections, such as, for example, hexagonal tubes. As used herein, “downstream” refers to a direction of flow of at least one of the fuel or the oxidizer.
Referring now to the drawings, in which like numbers refer to like elements throughout the several views,
The air inlet 110 may be connected to a source of pressurized air such as a compressor. The pressurized air may be used to fill and purge the combustion chamber 150 and also may serve as an oxidizer for the combustion of the fuel. The air inlet 110 may be in communication with a center body 180. The center body 180 may extend into the combustion chamber 150. The center body 180 may have any size, shape, or configuration. Likewise, the fuel inlet 120 may be connected to a supply fuel that may be burned within the combustion chamber 150. The fuel may be injected into the combustion chamber 150 so as to mix with the airflow.
An ignition device 190 may be positioned downstream of the air inlet 110 and the fuel inlet 120. The ignition device 190 may be connected to a controller so as to operate the ignition device 190 at desired times and sequences as well as providing feedbacks signals to monitor operations. As described above, any type of ignition device 190 may be used herein. The fuel and the air may be ignited by the ignition device 190 into a combustion flow so as to produce the resultant detonation waves. A portion of the airflow also may pass through the bypass duct 170. This portion of the airflow may serve to cool the tube 140, the combustion chamber 150, and the nozzle 130. Other components and other configurations may be used herein. Any type of pulse detonation combustor 100 may be used herein.
As described above, the flow of combustion gases 320 leaving the pulse detonation combustors 300 may have one or more undesirable emissions 325 such as carbon monoxide and nitrogen oxides therein. The pulse detonation turbine engine 250 thus may position a catalytic converter 360 between the high pressure turbine 340 and the low pressure turbine 350 so as to minimize or eliminate the undesirable emissions 325 therein. Generally described, the catalytic converter 360 works by using a catalyst to stimulate a chemical reaction in which the combustion emissions 325 are converted to less-toxic substances.
As is shown in
In use, the compressed flow of air 280 from the compressor 260 is mixed with the compressed flow of fuel 310 in the pulse detonation combustors 300 to produce the combustion gases 320. The combustion gases 320 drive the high pressure turbine 340 where mechanical work is extracted. The combustion gases 320 then pass through the catalytic converter 360 where the undesirable emissions 325 therein may be minimized and/or eliminated. Specifically, carbon monoxide may be oxidized and hence may release heat in an exothermic process. The heat produced in the catalytic converter 360 continues downstream with the flow of combustion gases 320 where useful work may be extracted in the low pressure turbine 350. As such, the catalytic converter 360 not only reduces the undesirable emissions 325, but also may improve the overall performance and efficiency of the pulse detonation turbine engine 250. Likewise, nitrogen oxide levels may be reduced therein. Other types of undesirable emissions 325 also may be reduced or eliminated.
The pulse detonation turbine engine 250 thus provides improved performance and efficiency with lower overall emissions. Not only are the undesirable emissions minimized 325, but these emissions 325 are used for this performance improvement. The use of the catalytic converter 360 also reduces the pressure and flow fluctuations exiting the high pressure turbine 340 so as to provide a lower pressure smoothed flow to the low pressure turbine 350. This smoothed flow thus facilitates the use of standard turbines herein.
It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
