BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to engines and in particular to intermittent detonation engines fueled by a liquid fuel in which the detonation products are used as the thrust producing medium.

2. Description of Related Art

A pulse detonation engine is an apparatus which produces a high pressure exhaust from a series of repetitive detonations within a detonation chamber. A fuel is detonated within the chamber, causing a wave which propagates at supersonic speeds. The speeds could approach or exceed Chapman Jouguet detonation velocities. The wave compresses the fluid within the chamber, increasing its pressure, density, and temperature. As the wave passes out an open rearward end of the detonation chamber, thrust is created. The cycle is then repeated.

At high speeds, such as Mach 2 to about Mach 3.5, such an engine would be theoretically more efficient than conventional turbojets because the engine does not require compressors or turbines. A pulse detonation engine supplying the same amount or more of thrust as a conventional gas turbine engine would theoretically weigh less. Also, a pulse detonation engine could be used as a propulsion system for a rocket.

Typically, pulse detonation engines have been described as gaseous fueled engines. Most aircraft today are fueled by liquid hydrocarbons such as JP-4, JP-5, or JP-10. Significant infrastructures are installed on these aircraft to store and deliver the liquid fuel to the aircraft's power source. Because of this, it highly desirous to have a pulse detonation engine that is fueled by liquid fuel and that can be easily integrated for use on an existing aircraft that uses liquid fuel.

BRIEF SUMMARY OF THE INVENTION

The pulse detonation engine of the present invention solves the main problem associated with integrating a pulse detonation engine with an existing aircraft. Since the pulse detonation engine of the present invention uses liquid fuel as a propellant, the engine can be easily integrated with an existing aircraft design, using the traditional liquid fuel infrastructure of the existing aircraft.

In a first embodiment of the present invention, a pulse detonation engine includes an outer tubular housing having a cylindrical bore and a plurality of outer housing ports. An inner tubular housing having a cylindrical bore and plurality of inner housing ports is rigidly and concentrically connected within the outer tubular housing. A detonation chamber is formed in the annulus between the inner and outer housings, the detonation chamber having an upstream end wall and an open downstream end.

An outer valve sleeve having a plurality of outer sleeve ports is concentrically and rotatably mounted to an exterior of the outer housing, the outer sleeve ports aligning with the outer housing ports when the outer valve sleeve is in an open position and not aligning with the outer housing ports when the outer valve sleeve is in a closed position.

A plurality of fuel injectors for injecting liquid fuel into the detonation chamber are rigidly disposed in the inner tubular housing, each fuel injector aligning with one of the inner housing ports. An inner protective sleeve having a plurality of inner sleeve ports is concentrically carried on an exterior of the inner housing. The inner protective sleeve oscillates along a longitudinal axis of the inner tubular housing between an open position and a closed position, the inner sleeve ports aligning with the inner housing ports when the inner protective sleeve is in the open position and not aligning with the inner housing ports when the inner protective sleeve is in the closed position.

An external drive system is used to rotate the outer valve sleeve and oscillate the inner protective sleeve. As the outer valve sleeve opens, air enters the detonation chamber through the outer housing ports. At the same time, the inner protective sleeve opens, and the fuel injectors inject liquid fuel into the detonation chamber through the inner housing ports. The liquid fuel and air form a fuel mixture, which is detonated by igniters that are disposed in the upstream end wall. The resulting detonation wave discharges out of the open downstream end of the detonation chamber, creating thrust for the engine.

In a second embodiment, a pulse detonation engine includes an outer tubular housing having a cylindrical bore and a plurality of outer housing ports. An inner tubular housing having a cylindrical bore and plurality of inner housing ports is rigidly and concentrically connected within the outer tubular housing. A detonation chamber is formed in the annulus between the inner and outer housings, the detonation chamber having an upstream end wall and an open downstream end.

An inner valve sleeve having a plurality of inner sleeve ports is concentrically and rotatably mounted to an interior of the inner housing, the inner sleeve ports aligning with the inner housing ports when the inner valve sleeve is in an open position and not aligning with the inner housing ports when the inner valve sleeve is in a closed position.

A plurality of fuel injectors for injecting liquid fuel into the detonation chamber are rigidly disposed on the outer tubular housing, each fuel injector aligning with one of the outer housing ports. An outer protective sleeve having a plurality of outer sleeve ports is concentrically mounted to an interior of the outer housing. The outer protective sleeve oscillates along a longitudinal axis of the outer tubular housing between an open position and a closed position, the outer sleeve ports aligning with the outer housing ports when the outer protective sleeve is in the open position and not aligning with the outer housing ports when the outer protective sleeve is in the closed position.

An external drive system is used to rotate the inner valve sleeve and oscillate the outer protective sleeve. As the inner valve sleeve opens, air enters the detonation chamber through the inner housing ports. At the same time, the outer protective sleeve opens, and the fuel injectors inject liquid fuel into the detonation chamber through the outer housing ports. The liquid fuel and air form a fuel mixture, which is detonated by igniters that are disposed in the upstream end wall. The resulting detonation wave discharges out of the open downstream end of the detonation chamber, creating thrust for the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a cross-sectional side view of a first embodiment of a liquid fueled pulse detonation engine having inner and outer sleeves according to the present invention, the inner and outer sleeves being shown in an open position.

FIG. 2

is a cross-sectional front view of the pulse detonation engine of

FIG. 1

taken along line II—II.

FIG. 3

is a cross-sectional side view of the pulse detonation engine of

FIG. 1

, the inner and outer sleeves being shown in a closed position.

FIG. 4

is a cross-sectional front view of the pulse detonation engine of

FIG. 3

taken along line IV—IV.

FIG. 5

is a cross-sectional side view of an alternate embodiment of a liquid fueled pulse detonation engine having inner and outer sleeves according to the present invention, the inner and outer sleeves being shown in an open position.

FIG. 6

is a cross-sectional front view of the pulse detonation engine of

FIG. 5

taken along line VI—VI.

FIG. 7

is a cross-sectional side view of the pulse detonation engine of

FIG. 5

, the inner and outer sleeves being shown in a closed position.

FIG. 8

is a cross-sectional front view of the pulse detonation engine of

FIG. 7

taken along line VIII—VIII.

FIG. 9

illustrates a military airplane powered by the pulse detonation engines of either

FIG. 1

or FIG.

5

.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to

FIGS. 1-4

in the drawings, the preferred embodiment of a pulse detonation engine

11

according to the present invention is illustrated. Pulse detonation engine

11

includes an outer tubular housing

13

and an inner tubular housing

15

. Outer tubular housing

13

has a plurality of outer housing ports

17

and a cylindrical bore with a longitudinal axis

19

. Inner tubular housing

15

is rigidly connected to outer tubular housing

13

within the bore, concentric with longitudinal axis

19

. Inner tubular housing

15

includes a plurality of inner housing ports

21

and a cylindrical bore with a longitudinal axis coaxial to axis

19

.

The location of inner tubular housing

15

within the bore of outer tubular housing

13

forms an annular detonation chamber

25

. The detonation chamber

25

has an upstream end wall

27

that is an integral part of outer tubular housing

13

. The detonation chamber has an open downstream end

29

.

An outer valve sleeve

33

is concentrically and rotatably mounted on an exterior of the outer tubular housing

13

. Outer valve sleeve

33

includes a plurality of outer sleeve ports

35

for registering with the outer housing ports

17

when valve sleeve

33

is in an open position (see FIG.

1

). A driven gear

37

is circumferentially disposed on an exterior of the valve sleeve

33

for receiving a drive gear

39

. The drive gear

39

is rotated by an external drive source to rotate outer valve sleeve

33

relative to outer tubular housing

13

.

The plurality of outer sleeve ports

35

and outer housing ports

17

allow air and/or oxygen to enter the detonation chamber

25

during operation of pulse detonation engine

11

. In some instances, air may be used as the sole oxidizing agent. In other instances, pure oxygen or oxygen-rich air may be injected into detonation chamber

25

through outer housing ports

17

nearer to upstream end wall

27

. A higher concentration of oxygen near the upstream end wall

27

, which is where ignition takes place, can aid in the ignition of a fuel mixture.

Outer sleeve ports

35

and outer housing ports

17

are arranged in four axial groups, each group being circumferentially disposed 90 degrees apart from the adjacent groups (see FIGS.

2

and

4

). The outer sleeve ports

35

and the outer housing ports

17

are angled toward the upstream end wall

27

. The angled characteristic of each port

17

,

35

boosts the air or oxygen delivery to the detonation chamber

25

, especially when using ram air that flows past the exterior of outer tubular housing

13

.

A plurality of fuel injectors

45

are rigidly connected to the inner tubular housing

15

within the bore of the housing

15

. Each fuel injector

45

is aligned with one of the inner housing ports

21

to provide liquid fuel to the detonation chamber

25

. Fuel injectors

45

atomize liquid fuel to approximately four microns and deliver the fuel to detonation chamber

25

. The atomized liquid fuel is mixed in the detonation chamber

25

with air or oxygen that enters through the outer housing ports

17

to create a fuel mixture. Lines

46

(schematically shown) lead from a fuel tank source

48

to each fuel injector

45

.

An inner protective sleeve

47

is concentrically disposed on an exterior of the inner tubular housing

15

and is capable of translational movement along longitudinal axis

19

relative to inner tubular housing

15

. Inner protective sleeve

47

includes a plurality of inner sleeve ports

49

for registering with the inner housing ports

21

. The primary function of inner protective sleeve

47

is protection of the fuel injectors

45

during detonation. It is conceivable that inner protective sleeve

47

could have a valving function such as that provided by outer valve sleeve

33

, but when used with fuel injectors

45

, such a valving function is unnecessary.

The plurality of inner sleeve ports

49

and inner housing ports

21

allow fuel to enter the detonation chamber

25

during operation of pulse detonation engine

11

. Inner sleeve ports

49

and inner housing ports

21

are arranged in four axial groups, each group being circumferentially disposed 90 degrees apart from the adjacent groups. Each group of the inner housing ports

21

is radially aligned with each group of outer housing ports

17

(see FIG.

2

). The radial alignment of these ports

17

,

21

allows improved mixing of the liquid fuel and air as it enters the detonation chamber

25

.

A cylindrical guide member

51

is rigidly connected to the outer tubular housing

13

near open downstream end

29

, the guide member being concentric with longitudinal axis

19

. Inner protective sleeve

47

has a channel

53

located at one end for receiving guide member

51

.

Guide member

51

serves to guide the inner protective sleeve

47

during its translational movement between an open position (see

FIGS. 1 and 2

) and a closed position (see FIGS.

3

and

4

). In the open position, the inner sleeve ports

49

register with the inner housing ports

21

, thereby exposing the fuel injectors

45

and allowing fluid communication between the fuel injectors

45

and the detonation chamber

25

. In the closed position, the inner sleeve ports

49

no longer register with the inner housing ports

21

. When the inner sleeve

47

is closed, the sleeve

47

covers the fuel injectors

45

thus protecting them during detonation.

Inner protective sleeve

47

is oscillated by an external drive system. The external drive system, which may or may not be the same as that used with the outer valve sleeve

33

, is operably connected to a crank shaft

59

. A connecting rod

61

is connected to the crank shaft

59

and converts the rotational motion of the crank shaft

59

to translational motion along longitudinal axis

19

. A translation rod

63

is rigidly connected at one end to the connecting rod

61

and at another end to the inner protective sleeve

47

. The translation rod

63

passes through the bore of inner tubular housing

15

. As the crank shaft

59

is rotated by the external drive system, the translation rod

63

and the inner protective sleeve

47

oscillate along longitudinal axis

19

between the open position and the closed position.

Detonation of the fuel mixture is performed by igniters

69

, which may be either spark-type or lasers. At least two igniters

69

are disposed in the upstream end wall

27

of the detonation chamber

25

. It is preferred to have at least four igniters

69

in the detonation chamber

25

, each igniter spaced 90 degrees apart. Only two of the four igniters

69

are shown in

FIGS. 1 and 3

. An alternate method of detonation could be supplied by injecting a preliminary detonation wave to start the main detonation.

In operation, the movements of outer valve sleeve

33

and inner protective sleeve

47

are timed to operate synchronously with fuel injectors

45

. During a normal cycle of the engine, the outer valve sleeve

33

opens, thus aligning outer sleeve ports

35

with outer housing ports

17

. At the same time, the inner protective sleeve

47

opens, thus aligning inner sleeve ports

49

with inner housing ports

21

. Air enters the detonation chamber

25

through outer housing ports

17

as atomized liquid fuel is delivered by the fuel injectors

45

through inner housing ports

21

. As the air and fuel enter the detonation chamber, the fuel mixture is formed.

Outer valve sleeve

33

closes so that outer sleeve ports

35

and outer housing ports

17

are no longer aligned. At the same time, the inner protective sleeve

47

moves along axis

19

into the closed position, thereby covering the fuel injectors

45

. The fuel mixture is detonated by igniters

69

. As the fuel mixture detonates, a detonation wave is formed that moves at five to seven thousand feet per second relative to the stationary reactants in front of the wave. The detonation wave is a high temperature, high pressure, detonation wave which discharges out open downstream end

29

, creating thrust. A reverberating expansion wave is created by the initial detonation wave. The expansion wave reflects off the upstream end wall

27

and discharges from the open downstream end

29

, creating additional thrust. The closure of outer valve sleeve

33

and inner protective sleeve

47

prevents hot products and hot metal from coming into contact with fuel or oxygen that has not yet been introduced into the detonation chamber

25

.

After detonation, the outer valve sleeve

33

moves again into the open position. During this portion of the cycle, however, no fuel is injected. Instead, ram air is allowed to flow through the outer housing ports

17

into the detonation chamber

25

. The ram air purges the detonation chamber

25

of any hot products and dilutes any trapped reactants. Immediately after purging, the outer valve sleeve

33

closes, and then the entire cycle is repeated. The rotational speed of outer valve sleeve

33

, the translational speed of inner protective sleeve

47

, and the injection rate of fuel injectors

45

are selected to create pulses at a rate of approximately 100 cycles per second.

Referring to

FIGS. 5-8

in the drawings, an alternate embodiment of a pulse detonation engine

111

according to the present invention is illustrated. Pulse detonation engine

111

includes an outer tubular housing

113

and an inner tubular housing

115

. Outer tubular housing

113

has a plurality of outer housing ports

117

and a cylindrical bore with a longitudinal axis

119

. Inner tubular housing

115

is rigidly connected to outer tubular housing

113

within the bore, concentric with longitudinal axis

119

. Inner tubular housing

115

includes a plurality of inner housing ports

121

and a cylindrical bore.

The location of inner tubular housing

15

within the bore of outer tubular housing

113

forms an annular detonation chamber

125

. The detonation chamber

125

has an upstream end wall

127

that is an integral part of outer tubular housing

113

. The detonation chamber has an open downstream end

129

.

An inner valve sleeve

133

is concentrically and rotatably mounted on an interior of the inner tubular housing

115

. Inner valve sleeve

133

includes a plurality of inner sleeve ports

135

for registering with the inner housing ports

121

when valve sleeve

133

is in an open position (see FIG.

5

). A driven gear

137

is circumferentially disposed on an exterior of the valve sleeve

133

for receiving a drive gear

139

. The drive gear

139

is rotated by an external drive source to rotate inner valve sleeve

133

relative to inner tubular housing

115

.

The plurality of inner sleeve ports

135

and inner housing ports

121

allow air or oxygen to enter the detonation chamber

125

during operation of pulse detonation engine

111

. In some instances, air may be used as the sole oxidizing agent. In other instances, pure oxygen or oxygen-rich air may be injected into detonation chamber

125

through inner housing ports

121

nearer to upstream end wall

127

. A higher concentration of oxygen near the upstream end wall

127

, which is where ignition takes place, can aid in the ignition of a fuel mixture.

Inner sleeve ports

135

and inner housing ports

121

are arranged in eight axial groups, each group being circumferentially disposed 45 degrees apart from the adjacent groups. It should be noted, however, that a smaller number of axial groups could be used. The inner sleeve ports

135

and the inner housing ports

121

are angled away from the upstream end wall

127

. The angled characteristic of each port

121

,

135

boosts the air or oxygen delivery to the detonation chamber

125

, especially when using ram air that flows into an interior of inner tubular housing

115

.

A plurality of fuel injectors

145

are rigidly connected to the outer tubular housing

113

and are aligned with the outer housing ports

117

to provide liquid fuel to the detonation chamber

125

. Lines

146

supply fuel to the fuel injectors

145

from a fuel source

148

. Fuel injectors

145

atomize liquid fuel to approximately four microns and deliver the fuel to detonation chamber

125

. The atomized liquid fuel is mixed in the detonation chamber

125

with air or oxygen that enters through the inner housing ports

121

to create a fuel mixture.

An outer protective sleeve

147

is concentrically disposed on an interior of the outer tubular housing

113

and is capable of translational movement along longitudinal axis

119

relative to outer tubular housing

113

. Outer protective sleeve

147

includes a plurality of outer sleeve ports

135

for registering with the outer housing ports

117

. The primary function of outer protective sleeve

147

is protection of the fuel injectors

145

during detonation. It is conceivable that outer protective sleeve

147

could have a valving function such as that provided by inner valve sleeve

133

, but when used with fuel injectors

145

, such a valving function is unnecessary.

The plurality of outer sleeve ports

135

and outer housing ports

117

allow fuel to enter the detonation chamber during operation of pulse detonation engine

111

. Outer sleeve ports

135

and outer housing ports

117

are arranged in eight axial groups, each group being circumferentially disposed 45 degrees apart from the adjacent groups. However, a greater or lesser number of groups could be used. Each group of the outer housing ports

117

is radially aligned with each group of inner housing ports

121

(see FIGS.

6

and

8

). The radial alignment of these ports

117

,

121

allows improved mixing of the liquid fuel and air as it enters the detonation chamber

125

.

Outer protective sleeve

147

is adapted to oscillate along longitudinal axis

119

between an open position (see

FIGS. 5 and 6

) and a closed position (see FIGS.

7

and

8

). In the open position, the outer sleeve ports

135

register with the outer housing ports

117

, thereby exposing the fuel injectors

145

and allowing fluid communication between the fuel injectors

145

and the detonation chamber. In the closed position, the outer sleeve ports

135

no longer register with the outer housing ports

117

. When the outer sleeve

147

is closed, the sleeve

147

covers the fuel injectors

145

thus protecting them during detonation.

Although it is preferable to oscillate outer protective sleeve

147

along axis

119

, the sleeve

147

could be rotated about the axis

119

. If the outer protective sleeve

147

was rotated, its function would remain the same as if the sleeve

147

was being oscillated.

Outer protective sleeve

147

is moved by an external drive system. The external drive system, which may or may not be the same as that used with the inner valve sleeve

133

, is operably connected to a crank shaft

159

. A connecting rod

161

is connected to the crank shaft

159

and converts the rotational motion of the crank shaft

159

to translational motion parallel to longitudinal axis

119

. A translation rod

163

is rigidly connected at one end to the connecting rod

161

and at another end to the outer protective sleeve

147

. The translation rod

163

is located outside of outer tubular housing

113

. As the crank shaft

159

is rotated by the external drive system, the translation rod

163

causes the outer protective sleeve

147

to oscillate along longitudinal axis

119

between the open position and the closed position.

Detonation of the fuel mixture is performed by igniters

169

, which may be either spark-type or lasers. At least two igniters

169

are disposed in the upstream end wall

127

of the detonation chamber

125

. It is preferred to have at least four igniters

169

in the detonation chamber, each igniter spaced 90 degrees apart. Only two of the four igniters

169

are shown in

FIGS. 5 and 7

. An alternate method of detonation could be supplied by injecting a detonation wave to start the main detonation.

In operation, the movements of inner valve sleeve

133

and outer protective sleeve

147

are timed to operate synchronously with fuel injectors

145

. During a normal cycle of the engine, the inner valve sleeve

133

opens, thus aligning inner sleeve ports

135

with inner housing ports

121

. At the same time, the outer protective sleeve

147

opens, thus aligning outer sleeve ports

135

with outer housing ports

117

. Air enters the detonation chamber

125

through inner housing ports

121

as atomized liquid fuel is delivered by the fuel injectors

145

through outer housing ports

117

. As the air and fuel enter the detonation chamber

125

, the fuel mixture is formed.

Inner valve sleeve

133

then closes so that inner sleeve ports

135

and inner housing ports

121

no longer align. At the same time, the outer protective sleeve

147

moves along axis

119

into the closed position, thereby covering the fuel injectors

145

. The fuel mixture is detonated by igniters

169

. As the fuel mixture detonates, a detonation wave is formed that moves at approximately five to seven thousand feet per second relative to the stationary reactants in front of the wave. The detonation wave is a high temperature, high pressure, detonation wave which discharges out open downstream end

129

, creating thrust. A reverberating expansion wave is created by the initial detonation wave. The expansion wave reflects off the upstream end wall

127

and discharges from the open downstream end

129

, creating additional thrust. The closure of inner valve sleeve

133

and outer protective sleeve

147

prevents hot products and hot metal from coming into contact with fuel or oxygen that has not yet been introduced into the detonation chamber

125

.

After detonation, the inner valve sleeve

133

moves again into the open position. During this portion of the cycle, however, no fuel is injected. Instead, ram air is allowed to flow through the inner housing ports

121

into the detonation chamber

125

. The ram air purges the detonation chamber

125

of any hot products and dilutes any trapped reactants. Immediately after purging, the inner valve sleeve

133

closes, and then the entire cycle is repeated. The rotational speed of inner valve sleeve

133

, the translational speed of outer protective sleeve

147

, and the injection rate of fuel

1

injectors

145

are selected to create pulses at a rate of approximately 100 cycles per second.

FIG. 9

illustrates a military airplane

181

that has pulse detonation engines

183

as shown in

FIGS. 1-8

. Airplane

181

has a fuselage

185

and wings

187

.

The present invention provides all of the advantages normally associated with pulse detonation engines coupled with the capability of using liquid fuel. Pulse detonation engines are generally capable of providing increased thrust when compared to conventional gas turbine engines. However, gaseous fuel is usually considered the primary fuel source for most pulse detonation engines. By providing fuel injectors and a protective sleeve to protect the fuel injectors during detonation, liquid fuel can be successfully utilized with the pulse detonation engine of the present invention. This is highly significant since typical aircraft use liquid fuel and have extensive infrastructure to support the use of liquid fuel. The use of liquid fuel with a pulse detonation engine allows the engine to be easily incorporated into existing aircraft designs.

It should be apparent from the foregoing that an invention having significant advantages has been provided. While the invention is shown in only a few of its forms, it is not just limited but is susceptible to various changes and modifications without departing from the spirit thereof.