PULSE DETONATION COMBUSTOR
BACKGROUND
[0001] The subject matter disclosed herein relates to a pulse detonation combustor,
and, more specifically, to an arrangement of pulse detonation tubes within a pulse
detonation combustor that accommodates thermal growth of the pulse detonation
tubes.
[0002] Gas turbine engines include one or more combustors, which receive and
combust compressed air and fuel to produce hot combustion gases. Certain turbine
engine concepts employ a pulse detonation combustor that includes one or more pulse
detonation tubes configured to combust the fuel-air mixture using a detonation
reaction. Within a pulse detonation tube, the combustion reaction is driven by a
detonation wave that moves at supersonic speed, thereby increasing the efficiency of
the combustion process. Specifically, air and fuel are typically injected into the pulse
detonation tube in discrete pulses. The fuel-air mixture is then detonated by an
ignition source, thereby establishing a detonation wave that propagates through the
tube at a supersonic velocity. The detonation process produces pressurized exhaust
gas within the pulse detonation tube that ultimately drives a turbine to rotate.
[0003] Unfortunately, due to the high temperatures and pressures associated with
detonation reactions, longevity of the pulse detonation tubes and associated
components may be significantly limited. Specifically, nozzles that direct exhaust gas
from the pulse detonation tubes to the turbine inlet may experience high thermal
stress, thereby limiting the useful life of such nozzles. In addition, thermal expansion
of the pulse detonation tubes requires complex mounting and sealing configurations to
maintain an entrance angle of exhaust gas into the turbine and efficiency of the
turbine engine.
[0004] Therefore, there is a need for a new and improved pulse detonation
combustor that addresses the high temperatures and pressures associated with
detonation reactions and the resulting complex mounting and sealing configurations
that facilitate thermal growth of the pulse detonation tube.
BRIEF DESCRIPTION
[0005] Certain embodiments commensurate in scope with the originally claimed
invention are summarized below. These embodiments are not intended to limit the
scope of the claimed invention, but rather these embodiments are intended only to
provide a brief summary of possible forms of the invention. Indeed, the invention
may encompass a variety of forms that may be similar to or different from the
embodiments set forth below.
[0006] Briefly, in accordance with one embodiment, a pulse detonation combustor
is provided. The pulse detonation combustor includes a plurality of nozzles
configured to support a gas discharge annulus in a circumferential direction; a
plurality of pulse detonation tubes extending to the plurality of nozzles; and a
plurality of thermal expansion control joints configured to facilitate independent
thermal growth of each pulse detonation tube.
[0007] In accordance with another embodiment, a pulse detonation combustor is
provided. The pulse detonation combustor includes a plurality of nozzles each
having a nozzle exit orifice and a nozzle inlet, wherein the plurality of nozzle exit
orifices are configured to form a gas discharge annulus. The combustor further
includes a plurality of pulse detonation tubes each coupled to a respective nozzle
inlet; and a plurality of thermal expansion control configured to facilitate independent
thermal growth of each pulse detonation tube.
[0008] These and other advantages and features will be better understood from the
following detailed description of preferred embodiments of the invention that is
provided in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] These and other features, aspects, and advantages of the present invention
will become better understood when the following detailed description is read with
reference to the accompanying drawings in which like characters represent like parts
throughout the drawings, wherein:
[0010] FIG. 1 is a block diagram of a turbine system having a pulse detonation
combustor including a pulse detonation tube and multiple nozzles configured to
interlock and provide for thermal growth of a pulse detonation tube in accordance
with certain embodiments of the present disclosure;
[0011] FIG. 2 is a partial cross-sectional side view of the pulse detonation
combustor, as shown in FIG. 1, in accordance with certain embodiments of the
present disclosure;
[0012] FIG. 3 is a perspective view of the pulse detonation combustor of FIG. 1,
showing a pulse detonation tube and nozzle assembly, in accordance with certain
embodiments of the present disclosure;
[0013] FIG. 4 is a cross-sectional view of a pulse detonation combustor in
accordance with certain embodiments of the present disclosure;
[0014] FIG. 5 is an enlarged cut-away perspective side view of the pulse
detonation combustor, as shown in FIG. 4, having thermal expansion control joints in
accordance with certain embodiments of the present disclosure;
[0015] FIG. 6 is a cross-sectional view of a pulse detonation combustor having
thermal expansion control joints in accordance with certain embodiments of the
present disclosure; and
[0016] FIG. 7 is a cross-sectional view of a pulse detonation combustor having
thermal expansion control joints in accordance with certain embodiments of the
present disclosure.
DETAILED DESCRIPTION
[0017] One or more specific embodiments of the present invention will be
described below. In an effort to provide a concise description of these embodiments,
all features of an actual implementation may not be described in the specification. It
should be appreciated that in the development of any such actual implementation, as
in any engineering or design project, numerous implementation-specific decisions
must be made to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which may vary from one
implementation to another. Moreover, it should be appreciated that such a
development effort might be complex and time consuming, but would nevertheless be
a routine undertaking of design, fabrication, and manufacture for those of ordinary
skill having the benefit of this disclosure.
[0018] Embodiments of the present disclosure may increase the longevity of pulse
detonation combustors, and in particular the pulse detonation tubes, by providing for
thermal growth of the pulse detonation tubes during operation. Specifically, in certain
embodiments, a pulse detonation combustor includes multiple pulse detonation tubes,
each being coupled to a nozzle. Each of the multiple nozzles including a nozzle exit
orifice and a nozzle inlet. The pulse detonation tube is coupled to each nozzle inlet,
and configured to flow exhaust gas from a detonation reaction through the nozzle.
Furthermore, the pulse detonation tubes, each includes at least one thermal expansion
control joint that provides for mounting of the pulse detonation tube to its respective
nozzle to facilitate thermal growth of the pulse detonation tube during operation.
[0019] Certain embodiments may also employ an impingement cooling system
configured to provide a cooling flow to the pulse detonation tube, thereby reducing
temperature and thermal stress. Specifically, an impingement cooling system may
include multiple axial cooling slots in flow communication with each pulse detonation
tube. Such a cooling system may significantly reduce the temperature of the pulse
detonation tube and minimize thermal growth.
[0020] As used herein, a pulse detonation tube 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 tube. 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 pulse detonation tubes 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 wave. 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).
[0021] The geometry of the detonation combustor is such that the pressure rise of
the detonation wave expels combustion products out the pulse detonation combustor
exhaust to produce a thrust force. Pulse detonation combustion can be accomplished
in a number of types of combustion chambers, including shock tubes, resonating
detonation cavities and tubular/tubo annular/annular combustors. As used herein, the
term "chamber" includes pipes having circular or non-circular cross-sections with
constant or varying cross sectional area. Exemplary chambers include cylindrical
tubes, as well as tubes having polygonal cross-sections, for example hexagonal tubes.
[0022] Turning now to the drawings and referring first to FIG. 1, a block diagram
of an embodiment of a gas turbine system 10 is illustrated. The turbine system 10
includes a fuel injector 12, a fuel supply 14, and a pulse detonation combustor (PDC)
16. As illustrated, the fuel supply 14 routes a liquid fuel and/or gaseous fuel, such as
natural gas, to the turbine system 10 through the fuel injector 12 into the PDC 16. As
discussed below, the fuel injector 12 is configured to inject and mix the fuel with
compressed air. The PDC 16 ignites and combusts the fuel-air mixture, and then
passes hot pressurized exhaust gas into a turbine 18. The exhaust gas passes through
turbine blades in the turbine 18, thereby driving the turbine 18 to rotate. Coupling
between blades in the turbine 18 and a shaft 19 will cause the rotation of the shaft 19,
which is also coupled to several components throughout the turbine system 10, as
illustrated. Eventually, the exhaust of the combustion process may exit the turbine
system 10 via an exhaust outlet 20.
[0023] In an embodiment of the turbine system 10, compressor blades are included
as components of a compressor 22. Blades within the compressor 22 may be coupled
to the shaft 19, and will rotate as the shaft 19 is driven to rotate by the turbine 18. The
compressor 22 may intake air to the turbine system 10 via an air intake 24. Further,
the shaft 19 may be coupled to a load 26, which may be powered via rotation of the
shaft 19. As will be appreciated, the load 26 may be any suitable device that may use
the power of the rotational output of the turbine system 10, such as an electrical
generator or an external mechanical load. For example, the load 26 may include an
electrical generator, a propeller of an airplane, and so forth. The air intake 24 draws
air 30 into the turbine system 10 via a suitable mechanism, such as a cold air intake.
The air 30 then flows through blades of the compressor 22, which provides
compressed air 32 to the PDC 16. In particular, the fuel injector 12 may inject the
compressed air 32 and fuel 14, as a fuel-air mixture 34, into the PDC 16.
Alternatively, the compressed air 32 and fuel 14 may be injected directly into the
PDC 16 for mixing and combustion.
[0024] As discussed in detail below, the present embodiment includes multiple
pulse detonation tubes within the PDC 16. The tubes are configured to receive
compressed air 32 and fuel 14 in discrete pulses. After a pulse detonation tube has
been loaded with a fuel-air mixture, the mixture is detonated by an ignition source,
thereby establishing a detonation wave that propagates through the tube at a
supersonic velocity. The detonation process produces pressurized exhaust gas within
the pulse detonation tube that ultimately drives the turbine 18 to rotate. In certain
embodiments, each pulse detonation tube is coupled to the turbine 18 via a nozzle
including a nozzle exit orifice. The nozzle exit orifices engage with one another via
mating surfaces(28) to form a gas discharge annulus. This configuration provides
mutual support for each nozzle exit orifice, thereby facilitating resistance to thermal
loads associated with the hot exhaust gas. Alternatively, the nozzles for each tube
may be integrally formed out of a single monolith, such as a casting or a single
machined block of metal. Further embodiments may employ a cooling system to
reduce the temperature of the pulse detonation tube, thereby increasing longevity of
the combustor. While the pulse detonation tubes are described with reference to a
PDC 16, it should be appreciated that the presently disclosed embodiments may be
utilized for other applications employing pulse detonation tubes.
[0025] FIG. 2 is a partial cross-sectional side view of the PDC 16 that may be used
in the turbine system 10 of FIG. 1. As previously discussed, the PDC 16 includes
multiple pulse detonation tubes (PDTs) 36. While only one PDT 36 is illustrated, it
will be appreciated that multiple PDTs 36 may be circumferentially positioned about a
centerline 38. Generally, PDCs 16 include PDTs 36 oriented axially and radially
away from the turbine 18, thus increasing the length of the turbine system 10
compared to traditional configurations employing deflagration-type combustors. As
discussed in detail below, a circumferential arrangement of PDTs 36 may decrease the
overall length of the turbine system 10 to a length more commensurate in scope with
traditional turbine systems. While a PDC 16 is employed in the present configuration,
it should be noted that alternative embodiments may employ a combustor including
both PDTs 36 and traditional deflagration-type combustors.
[0026] As illustrated, each PDT 36 is coupled to a respective nozzle 40. In
alternative embodiments, multiple PDTs 36 may be coupled to each nozzle 40. In the
present embodiment, each PDT 36 may include a flange 37 configured to mate with a
corresponding flange 39 of the nozzle 40. As illustrated, fasteners 4 1 serve to secure
the PDT flange 37 to the nozzle flange 39. Further embodiments may employ
alternative conventional means of attaching the PDT 36 to the nozzle 40 (e.g., welded
connection). Additionally, the nozzle 40 may be integral with the PDT 36. That is,
the PDT 36 and nozzle 40 may be combined into a single structure. As will be
described in greater detail below, each nozzle 40 comprises a nozzle exit orifice 42
having an inner flanged segment 44 and an outer flanged segment 46. In certain
embodiments, the nozzle exit orifices 42 contain unique features that allow them to be
interlocked, thereby establishing a combined gas discharge annulus that provides
mutual support for the individual nozzles 40, as well as a surface for mounting to a
frame. In other embodiments, the nozzles for each tube could be formed from a
single integral structure.
[0027] In operation, pressurized air 32 enters the PDC 16 through a compressor
outlet 48, including a diffuser 52 that directs airflow into the PDC 16. Specifically,
the diffuser 52 converts the dynamic head from high-velocity compressor air into a
pressure head suitable for combustion (i.e., decreases flow velocity and increases flow
pressure). In the present embodiment, the flow is redirected such that turbulence is
substantially reduced.
[0028] The pressurized air 32 is then directed into a flow path 49 between a PDC
casing 50 and the PDT 36. As illustrated, PDC casing 50 is coupled to a structural
member 68 providing support to PDC casing 50. As previously discussed, detonation
reactions generate significant heat output. Because the pressured air 32 is cooler than
the detonation reaction within the PDT 36, airflow along the outer wall of the PDT 36
transfers heat from the PDT 36 to the pressurized air 32. This configuration both
cools the PDT 36 during operation, and increases the temperature of air entering the
PDT 36.
[0029] The pressured air 32 ultimately flows to a distal end (not shown) of the
PDT 36 prior to entering an interior of the PDT 36. As the pressurized air 32 reaches
the distal end, an air valve periodically opens to emanate air pulses into the PDT 36.
In addition, the fuel injector 12 injects fuel into the air stream, either prior to entering
the PDT 36, or within the PDT 36, thereby establishing a fuel-air mixture 34 suitable
for detonation. Within the PDT 36, the fuel-air mixture 34 is detonated by an ignition
source, establishing a deflagration to detonation transition (DDT) that forms a
detonation wave. The detonation wave propagates through the fuel-air mixture
toward the nozzle 40 at a supersonic velocity. The detonation wave induces a
combustion reaction between the fuel and air, thereby generating heat and forming
exhaust products 54 upstream of the wave. As the detonation wave propagates
through the fuel-air mixture, the interior of the PDT 36 becomes pressurized due to
temporary confinement of the expanding exhaust products 54 within the PDT 36.
Specifically, the detonation wave heats the exhaust products 54 faster than the
expanding gas can exit the nozzle 40, thereby increasing pressure within the PDT 36.
After the detonation wave has substantially reacted the fuel and air within the PDT
36, the pressurized exhaust products 54 are expelled through the nozzle 40 into a
turbine rotor 55, thereby driving the turbine 18 to rotate.
[0030] The nozzle 40 converges in a cross-sectional area perpendicular to a
direction of gas flow through the nozzle to maintain a choked flow of the exhaust
products 54 from the PDT 36 to the nozzle exit orifice 42. For example, in certain
configurations, the cross-sectional area of the PDT 36 may be approximately four
times greater than a cross-sectional area of the nozzle exit orifice 42. In addition,
each nozzle may converge in cross-sectional area from the nozzle inlet to a throat, and
diverge in cross-sectional area from the throat to the nozzle exit orifice 42.
Furthermore, the nozzle 40 may transition from a substantially circular cross-section
of the PDT 36 to a shape having substantially flat circumferential sides at the nozzle
exit orifice 42. The substantially flat circumferential sides may enable the nozzle exit
orifices 42 to interlock, thereby forming a gas discharge annulus that supports the
nozzle exit orifices 42 during operation. As will also be described, the PDT 36 and
nozzle 40 may be oriented at an angle with respect to the turbine system centerline 38
that is at or near a turbine entrance angle. The exhaust products 54 are thereby
directed to the turbine 18 at a suitable orientation to obviate first stage turbine
nozzles.
[0031] FIG. 3 is a perspective view of an exemplary pulse detonation combustor,
and more particularly a tube and nozzle assembly 70, looking generally from the
turbine 18 toward the compressor 22. As discussed in detail below, the nozzle exit
orifices 42 are designed to tessellate and interlock with adjoining nozzle exit orifices
42 when assembled into a gas discharge annulus 65. This configuration may provide
structural support for each nozzle exit orifice 42, thereby protecting the orifices 42
from high thermal and mechanical stresses associated with the detonation process.
[0032] In the present configuration, the nozzles 40, and as a result the PDTs 36,
are oriented at an angle 56 with respect to a radial axis 58 extending from the turbine
system centerline 38. Specifically, the angle 56 defines the angular orientation of a
nozzle centerline 60 relative to the radial axis 58. In other words, the nozzles 40 are
oriented substantially tangent to the gas discharge annulus 65 formed by the assembly
of nozzle exit orifices 42. In alternative embodiments, the nozzles 40 may be oriented
at other suitable angles 56 relative to the radial axis 58. For example, angle 56 may
be approximately between 0 to 180, 30 to 150, 60 to 120, 60 to 90, or about 75 to 90
degrees. The orientation of the nozzles 40 imparts a circumferential velocity
component onto the flow of exhaust products into the turbine 18.
[0033] Furthermore, while twelve nozzles 40 are coupled to the PDC 16 in the
depicted embodiment, alternative embodiments may employ more or fewer nozzles
40. For example, certain PDC configurations may include more than 1, 2, 4, 6, 8, 10,
12, 14, 16, 18, 20, or more nozzles 40 and associated PDTs 36. Each nozzle exit
orifice 42 includes the inner flange segment 44 and the outer flange segment 46
which, when assembled, form inner and outer flanges about the gas discharge annulus
65. The inner flange provides a surface against which the inner frame member 62
may be mounted, and the outer flange provides a surface against which an outer frame
member 64 may be secured. Both the inner and outer frame members 62 and 64 are
secured to the turbine 18. In addition, a structural member 68 is illustrated and
provides structural support to secure the nozzles 40 to the PDC 16 such that thermal
expansion of the nozzles 40 and/or the PDTs 36 does not significantly alter the
position and orientation of the nozzle exit orifices 42 relative to the turbine 18. In this
configuration, nozzle exit orifices 42 may flow exhaust products 54 into the turbine
18 at an orientation configured to obviate first stage turbine nozzles. Additional
information regarding a pulse detonation combustor configuration, including a
plurality of pulse detonation tubes coupled to a plurality of nozzles, in which a
plurality of nozzle exit orifices are engaged with one another via mating surfaces can
be found in co-pending U.S. Patent application entitled, "Pulse Detonation
Combustor" by Kenyon et al., filed on November 30, 2009, bearing serial no.
12/627,942 and assigned to the same assignee, which application is incorporated
herein by this reference.
[0034] Referring now to FIGs. 4 and 5, illustrated in a cross-sectional view and
partial cross-sectional view, respectively, is a pulse detonation combustor, and more
particularly a pulse detonation tube and nozzle assembly, 80 including a thermal
expansion control joint configured to enable the pulse detonation tube 36 to thermally
expand during operation. As previously discussed, the PDT 36 may be coupled to the
nozzle 40 using a variety of techniques. As illustrated, the PDT 36 and nozzle 40 are
attached via a welded joint 82. As will be appreciated, the detonation process
generates heat that may induce significant thermal expansion of the PDTs 36. For
example, a 40 inch (102 cm) long PDT may increase in length by as much as 0.75
inches (2 cm). As illustrated, the nozzle exit orifice 42 is secured to the inner frame
member 62 by the inner flange segment 44, which is sandwiched between the inner
frame member 62 and an inner support member 84. Similarly, the outer flange
segment 46 is sandwiched between the outer frame member 64 and an outer support
member 86, thereby securing the nozzle exit orifice 42 to the outer frame member 64.
Because the inner frame member 62 and the outer frame member 64 are secured to the
turbine 18, the position of the nozzle exit orifice 42 is fixed with respect to the turbine
18. This configuration maintains the orientation of exhaust flow into the turbine 18
despite thermal growth of the nozzle 42 and/or the PDT 36. In the exemplary
embodiment, the PDC casing 50 is coupled to the structural member 68 and includes a
thermal expansion control joint 90 to facilitate thermal expansion, or growth, of the
PDT 36 while maintaining a position of a tube head end 92 with respect to the casing
50, and more specifically an outer cup 94 of an air valve 96 that periodically opens to
emanate air pulses into the PDT 36. More particularly, thermal expansion control
joint 90 is configured as a bellows expansion joint 100 integrally formed with the
PDC casing 50 whereby, during thermal growth of the PDT 36, the bellows expansion
joint 100 expands in an axial direction as indicated by arrows 102. A plurality of
alignment fins 104 may be provided extending from an outer surface 105 of the PDT
36 to maintain concentric alignment of the PDT 36 relative to the PDC casing 50
during thermal expansion of the PDT 36. Alignment fins 104 may be formed as a
ring 106 circumscribing the PDT 36, or alternatively, as a plurality of discrete pintype
protrusions 108 providing for a greater free flow of air through the flow path 49
between the PDC casing 50 and the PDT 36. By incorporating a thermal expansion
control joint 90 for each pulse detonation combustor, and more particularly each pulse
detonation tube and nozzle assembly, 80 each individual PDTs 36 is configured to
expand independently of the other PDTs 36.
[0035] Referring now to FIG. 6, illustrated in a cross-sectional view is a pulse
detonation combustor, and more particularly a pulse detonation tube and nozzle
assembly, 200 including a thermal expansion control joint configured to enable the
pulse detonation tube 36 to thermally expand during operation. As previously
discussed, the PDT 36 may be coupled to the nozzle 40 using a variety of techniques.
As illustrated, the PDT 36 and nozzle 40 are attached via a welded joint 82. As
previously described with regard to FIGs. 4 and 5, the detonation process generates
heat that may induce significant thermal expansion of the PDTs 36. Similar to the
previous embodiment, the nozzle exit orifice 42 is secured to the inner frame member
62 by the inner flange segment 44, which is sandwiched between the inner frame
member 62 and the inner support member 84. Similarly, the outer flange segment 46
is sandwiched between the outer frame member 64 and the outer support member 86,
thereby securing the nozzle exit orifice 42 to the outer frame member 64. The
position of the nozzle exit orifice 42 is fixed with respect to the turbine 18, thus
maintaining the orientation of exhaust flow into the turbine 18 despite thermal growth
of the nozzle 42 and/or the PDT 36. In this exemplary embodiment, the PDC casing
50 is coupled to the structural member 68 and includes the thermal expansion control
joint 90 to facilitate thermal expansion, or growth, of the PDT 36 while maintaining a
position of the tube head end 92 with respect to the casing 50. In the embodiment
illustrated in FIG. 6, the thermal expansion control joint 90 is configured as an
expansion joint 202 between a lower end of the outer cup 94 of the aid valve 96 and a
radial support member 204, positioned circumscribing the PDT 36. During thermal
growth of the PDT 36, the expansion joint 202 expands in an axial direction as
indicated by arrows 206 allowing for the outer cup 94 of the air valve 96 to move
axially and allow thermal growth of the PDT 36. The radial support member 204
provides a means to maintain concentric alignment of the PDT 36 relative to the PDC
casing 50 during thermal expansion of the PDT 36. By incorporating a thermal
expansion control joint 90 for each pulse detonation combustor, and more particularly
each pulse detonation tube and nozzle assembly, 200 each individual PDTs 36 is
configured to expand independently of the other PDTs 36.
[0036] Referring now to FIG. 7, illustrated in a cross-sectional view is a pulse
detonation combustor, and more particularly a pulse detonation tube and nozzle
assembly, 300 including a thermal expansion control joint configured to enable the
pulse detonation tube 36 to thermally expand during operation. As previously
discussed, the PDT 36 may be coupled to the nozzle 40 using a variety of techniques.
As illustrated, the PDT 36 and nozzle 40 are attached via a welded joint 82. As
previously described with regard to FIGs. 4, 5 and 6, the detonation process generates
heat that may induce significant thermal expansion of the PDTs 36. In this particular
embodiment, the nozzle exit orifice 42 is secured to the inner frame member 62 by the
inner flange segment 44, which is sandwiched between the inner frame member 62
and the inner support member 84. Similarly, the outer flange segment 46 is
sandwiched between the outer frame member 64 and the outer support member 86,
thereby securing the nozzle exit orifice 42 to the outer frame member 64. In this
particular embodiment, the nozzle exit orifice 42, while described as being secured to
the inner frame member 62 and the outer frame member 62, may be secured in a
manner including some degree of flexibility between the nozzle 40 and the frame
members 62, 64 to accommodate thermal growth of the PDT 36. Irrespective of
securement means, the position of the nozzle exit orifice 42 is fixed with respect to
the turbine 18, thus maintaining the orientation of exhaust flow into the turbine 18
despite thermal growth of the nozzle 42 and/or the PDT 36. In this exemplary
embodiment, the PDC casing 50 is coupled to the structural member 68 and includes
at least one thermal expansion control joint 90 to facilitate thermal expansion, or
growth, of the PDT 36 while maintaining a position of the tube head end 92 with
respect to the casing 50. In the embodiment illustrated in FIG. 7, the thermal
expansion control joint 90 is configured as a sliding expansion joint 302, whereby an
upper end portion 304 of the PDT tube 36 is configured to slide within a radial
support member 306, to accommodate thermal growth of the PDT 36. To
accommodate the sliding expansion joint 302, the radial support member 306, is
positioned circumscribing the PDT 36. The radial support member 306 has formed
integrally therein a sliding space 308, allowing movement therein of the PDT 36. The
PDC casing 50 may further include at least one expansion control joint 90, in the form
of expansion joints 310 formed in the outer casing 50. During thermal growth of the
PDT 36, the PDT tube 36 slides in an axial direction as indicated by arrows 312
within the sliding expansion joint 302. In addition, the outer casing 50 may expand in
an axially direction at the at least one expansion control joint 310, allowing for the
PDT 36 to move axially and allow for thermal growth of the PDT 36. The radial
support member 306 provides a means to maintain concentric alignment of the PDT
36 relative to the PDC casing 50 during thermal expansion of the PDT 36. By
incorporating a thermal expansion control joint 90 for each pulse detonation
combustor, and more particularly each pulse detonation tube and nozzle assembly,
300 each individual PDTs 36 is configured to expand independently of the other
PDTs 36. The tube end 304 has provisions for a sliding seal such as a piston ring, an
o-ring, a graphoil rope seal or a raised bump (or series of raised bumps) similar to
labyrinth seals.
[0037] As best illustrated in FIG. 7, the pulse detonation combustor, and more
particularly pulse detonation tube and nozzle assembly, 300 may include an internozzle
cooling configuration. As previously described, the pulse detonation process
generates high temperature exhaust products 54 that pass through the nozzle exit
orifices 42, thereby exposing the nozzles 40 to high thermal loads. Consequently, the
present embodiment includes a system configured to provide cooling to the individual
nozzles 40. A cooling manifold, such as the illustrated circumferential cooling
manifold 320, is formed proximate the nozzle 40. The circumferential cooling
manifold 320 extends axially and circumferentially about the nozzle 40 and provides
impingement cooling to the nozzle 40. One or more cooling slots, such as the
illustrated axial cooling slots 322, are formed proximate the nozzle 40 and provide
cooling thereto. As will be appreciated, alternative embodiments may include cooling
slots angled with respect to the axial direction. In operation, cooling air, from the
compressor 22 or an alternate air source (e.g., external compressor, air blower, etc.)
may be introduced to the circumferential cooling manifold 320, and more particularly
through the axial cooling slots 322, and then axially along the nozzle 40. The airflow
may serve to absorb heat from the inter-nozzle area, thereby cooling the nozzle 40.
[0038] In operation, cooling air enters the circumferential cooling manifold 320
and flows through the axially cooling slots 322. The cooling air impinges upon an
outer circumferential surface 4 1 of the nozzle 40. As the cooling air flows along the
outer circumferential surface 4 1 in the axial direction, heat from the exhaust products
is absorbed by the air, thereby cooling the nozzle 40. Like the inter-nozzle cooling
configuration may employ certain structures to enhance heat transfer between the
cooling air and the outer circumferential surface 41, such as fins, vanes, or baffles.
Further embodiments may utilize a cooling medium other than air, such as water,
nitrogen, or carbon dioxide.
[0039] Although the present embodiment discloses specific pulse detonation tube
and nozzle assembly embodiments, the disclosure is not limited to such designs.
Alternative configurations of the pulse detonation tube and nozzle assembly may
employ pulse detonation tube and nozzle configurations that provide for thermal
growth of the pulse detonation tube in a similar manner. It will be appreciated that
the orientation and configuration of the components employed are a function of the
design and operational requirements of the particular application. Those of ordinary
skill in the art are capable of determining and implementing the optimal
configuration, taking into account the necessary parameters and design criteria.
[0040] This written description uses examples to disclose the invention, including
the best mode, and also to enable any person skilled in the art to practice the
invention, including making and using any devices or systems and performing any
incorporated methods. The patentable scope of the invention is defined by the claims,
and may include other examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if they have structural
elements that do not differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from the literal languages
of the claims.
CLAIMS:
1. A pulse detonation combustor, comprising:
a plurality of nozzles configured to support a gas discharge annulus in a
circumferential direction;
a plurality of pulse detonation tubes extending to the plurality of nozzles; and
a plurality of thermal expansion control joints configured to facilitate
independent thermal growth of each pulse detonation tube.
2. The pulse detonation combustor of Claim 1, wherein the plurality of
nozzles are engaged with one another via mating surfaces.
3. The pulse detonation combustor of Claim 1, wherein the plurality of
nozzles are configured as a monolithic structure.
4. The pulse detonation combustor of Claim 1, wherein each pulse
detonation tube extends to a respective nozzle.
5. The pulse detonation combustor of Claim 1, wherein each of the
plurality of thermal expansion control joints is configured as a bellows expansion
joint.
6. The pulse detonation combustor of Claim 5, wherein the bellows
expansion joint is formed integral with a pulse detonation combustor casing
circumscribing the pulse detonation tube and provides for axial expansion of the
pulse detonation casing.
7. The pulse detonation combustor of Claim 6, wherein the pulse
detonation tube further includes at least one alignment fin on an exterior surface
providing concentric alignment of the pulse detonation tube relative to the pulse
detonation combustor casing.
8. The pulse detonation combustor of Claim 7, wherein the at least one
alignment fin is configured as a ring circumscribing the pulse detonation tube.
9. The pulse detonation combustor of Claim 7, wherein the at least one
alignment fin is configured as a discrete pin protruding from an outer surface of the
pulse detonation tube.
10. The pulse detonation combustor of Claim 1, wherein each of the
plurality of thermal expansion control joints is configured as a sliding expansion joint.
11. The pulse detonation combustor of Claim 10, wherein the sliding
expansion joint is configured to include at least one of a piston ring, a graphoil rope,
an o-ring, a labyrinth seal and a c-seal.
12. The pulse detonation combustor of Claim 10, wherein the sliding
expansion joint is configured to provide axial movement of an outer cup of an air
valve positioned at an uppermost end portion of each pulse detonation tube.
13. The pulse detonation combustor of Claim 10, wherein the sliding
expansion joint is configured to provide axial movement of the pulse detonation tube
relative to a radial support member fixed radially about the pulse detonation tube.
14. The pulse detonation combustor of Claim 1, wherein each nozzle is
oriented substantially tangent to the gas discharge annulus.
15. The pulse detonation combustor of Claim 1, wherein each nozzle is
oriented at an angle relative to a pulse detonation combustor longitudinal centerline
corresponding to a turbine entrance angle.
16. The pulse detonation combustor of Claim 1, further comprising a
plurality of cooling manifolds each having one or more axial cooling slots in fluid
communication with each of the plurality of nozzles.
17. A pulse detonation combustor, comprising:
a plurality of nozzles each having a nozzle exit orifice and a nozzle inlet,
wherein the plurality of nozzle exit orifices are configured to form a gas discharge
annulus;
a plurality of pulse detonation tubes each coupled to a respective nozzle inlet;
and
a plurality of thermal expansion control joints configured to facilitate
independent thermal growth of each pulse detonation tube.
18. The pulse detonation combustor of Claim 17, wherein the plurality of
nozzle exit orifices are engaged with one another via mating surfaces to form the gas
discharge annulus.
19. The pulse detonation combustor of Claim 17, wherein each pulse
detonation tube is coupled to the respective nozzle inlet by a welded connection.
20. The pulse detonation combustor of Claim 17, wherein each nozzle
converges in a cross-sectional area perpendicular to a direction of gas flow through
the nozzle from the nozzle inlet to the nozzle exit orifice.
21. The pulse detonation combustor of Claim 17, wherein each of the
plurality of thermal expansion control joints is configured as a bellows expansion
joint.
22. The pulse detonation combustor of Claim 21, wherein the bellows
expansion joint is formed integral with a pulse detonation combustor casing
circumscribing the pulse detonation tube and provides for axial expansion of the
pulse detonation casing.
23. The pulse detonation combustor of Claim 21, wherein the pulse
detonation tube further includes at least one alignment fin on an exterior surface
providing alignment of the pulse detonation tube relative to the pulse detonation
combustor casing.
24. The pulse detonation combustor of Claim 21, wherein the at least one
alignment fin is configured as at least one of a ring circumscribing the pulse
detonation tube or a discrete pin protruding from an outer surface of the pulse
detonation tube.
25. The pulse detonation combustor of Claim 17, wherein each of the
plurality of thermal expansion control joints is configured as a sliding expansion joint.
26. The pulse detonation combustor of Claim 25, wherein the sliding
expansion joint is configured to provide axial movement of an outer cup of an air
valve positioned at an uppermost end portion of each pulse detonation tube.
27. The pulse detonation combustor of Claim 25, wherein the sliding
expansion joint is configured to facilitate axial movement of the pulse detonation tube
relative to a radial support member fixed radially about the pulse detonation tube.
28. The pulse detonation combustor of Claim 17, further comprising a
plurality of cooling manifolds each having one or more cooling slots in fluid
communication with the plurality of nozzles.
29. The pulse detonation combustor of Claim 28, wherein each of the
cooling manifolds is disposed adjacent to an outer circumferential surface of the
nozzle, and the cooling slots are configured to cool the outer circumferential surface
of nozzle.