High Speed Valveless Resonant Pulse Jet Engine

Abstract

A valveless resonent pulse jet engine particularly adapted to power target vehicles or pilotless aircraft at speeds of Mach 0.5 to Mach 1. This invention is an improved high-speed adaptation of my U.S. Pat. No. 3,517,510. The device of this invention continues to utilize a substantially cylindrical combustion chamber, a reduction cone and an exhaust tube, a multiplicity of reverse flow air fuel inlet tubes projecting through the reduction cone into the combustion chamber. Annular reverse flow vanes surround the bell mouth of the air inlet tubes thereby increasing static pressure at the air inlet as forward speed of the vehicle increases. An exhaust tube diffuser is employed in a similar fashion to assist the pulsating reverse flow of ambient air into the exhaust tube to increase thrust at high forward speeds.

Description

CROSS REFERENCE TO RELATED APPLICATION

The device of this invention is directly related to applicant's U.S. Pat. No. 3,517,510. Many of the construction features of the device of this invention are identical with the above referred to patent. The device of this invention is an improved high-speed adaptation of the previously patented device. Experimental results have shown that the previously patented device is highly satisfactory for low speed flight or stationary use as a space or orchard heat. At speeds from Mach 0.5 to Mach 1 flame moves aft in the exhaust tube and thrust is decreased and flame-out can occur. To insure and obtain satisfactory operating characteristics from Mach 0.5 to Mach 1 annular reverse flow vane has been constructed to surround the bell mouth of the intake tube to increase static pressure and inject air into the tube. To insure reverse flow into the exhaust nozzle a truncated conical exhaust tube diffuser is constructed around the exhaust nozzle to insure proper reverse flow of air or increase static pressure at the exhaust nozzle retaining the pulsating flame in the appropriate operating areas of the device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to a resonant valveless pulse jet engine designed for high-speed operation. Previously existing pulse jets generally lost thrust and operating characteristics deteriorated above Mach 0.5. The device of this invention is particularly designed with a view to retaining optimum thrust and operating characteristics at speeds above Mach 0.5. This is accomplished through the use of the annular reverse flow vanes and the exhaust tube diffuser.

DESCRIPTION OF THE PRIOR ART

The closest related prior art is your applicant's U.S. Pat. No. 3,517,510 issued June 30, 1970. For a general illustration of the state of the art, reference is made to Project Squid, Department of the Navy, Research Project, and Technical Memorandum No. PR.--4 concerning the background and development of the German V--1 Ing. Guenther Dietrich translated by A. Kahane, June 30, 1948, Princeton University, and Technical Memorandum No. CAL--27 by Joseph G. Logan, Jr., May, 1949, by Cornell Aeronautical Laboratories. The examples of valveless pulse jets are Schuberts and SNECMA.

SUMMARY OF THE INVENTION

The device of this invention basically incorporates the disclosure of my U.S. Pat. No. 3,517,510 with the addition of substantially circular annular reverse flow vane encircling the bell mouth of each fuel air inlet tube. This annular reverse flow vane is of substantially greater diameter than the bell mouth of the inlet tube. The vane collects air as the engine of this device obtains forward momentum and through reverse flow lip inject and increases static pressure at the air fuel inlet tubes. The second improvement of this invention pertains to the exhaust tube diffuser which is constructed on the engine at the nozzle end of the exhaust tube. Improvement in this area of the device comprises a substantially elongated truncated cone exhaust tube diffuser inlet or the base of the conical-like strucutre projects forward and catches and forces air into the exhaust nozzle as forward speed of the engine increases. Experiments conducted in a plenum chamber with previous device conclusively establishes the fact that at high speeds or at increased pressures at the air fuel inlet tubes causes the flame to move to the nozzle end of the exhaust tube. The exhaust tube diffuser of the invention of this device increases pressure or reverse flow into exhaust tube nozzle moving the flame back into the engine to the desired operating area and restores thrust of the engine. The diameter of the exhaust tube diffuser is directly proportional to the design speed of the engine. The higher the design speed, the larger the required diameter of the exhaust tube diffuser.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view partially in cross section of the engine of this invention.

FIG. 2 is a cross sectional view of the device taken substantially on line 2--2 of FIG. 1 looking in the direction of the arrows. This view discloses primarily the bell mouth of the air fuel inlet tubes.

FIG. 3 is a sectional view of FIG. 1 taken substantially on line 3--3 looking in the direction of the arrows disclosing primarily the outer surface of annular reverse flow vanes.

FIG. 4 is a fragmented sectional view of the bell mouth nozzle of the air-fuel inlet tube surrounded by a fragmented sectional view of the annular reverse flow vanes and brackets.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For a description of the preferred embodiment, its method of construction, and operation, reference is made to the attached views and the following detailed description wherein identical reference characters refer to identical or equivalent components throughout the several views and the following detailed description.

The device of this invention may be constructed from various metals or alloys; however, the preferred embodiment was constructed from 321 or 347 type stainless steel AMS spec 5510, 5512 or 5570. Any of the number of acceptable methods could be employed for securing the components in a unitary structure; however, in the preferred embodiment, heliarc welding was primarily used in the construction. For a description of the construction of the device of the invention, one might well refer to my previous U.S Pat. No. 3,517,510. Many of the components and methods of construction are identical. Referring to FIG. 1, the device is constructed around a substantially cylindrical combustion chamber 11. Aft of the combustion chamber 11 is constructed or secured the combustion chamber reduction cone 12 to which is attached the elongated exhaust tube 13 which terminates at its aft end in the exhaust tube nozzle 14. Secured to the forward end of the combustion chamber 11 is combustion chamber forward wall 15. This wall is slightly arched to prevent fatigue of the metal; however, the desierd flow characteristic dictates a forward wall 15 constructed at substantially right angles to the axis of the exhaust tube 13.

A multiplicity of air and fuel inlet tubes 16 are equiangularly positioned in reduction cone 12 and project into the cylindrical combustion chamber 11. These air and fuel inlet tubes 16 are constructed on an axis parallel to the axis of combustion chamber 11 and the exhaust tube 13. Heliarc welding is a statisfactory method of securing the tubes 16 to reduction cone 12. Secured to the forward end of combustion chamber 11 is nose cone 17 into which is constructed with a cooling vent 18 and air exit vents 19 to assist in dissipating heat from the combustion chamber forward walls 15. The principal diagonal structure member in the midsection of the engine is vertical support plate 20. This plate 20 is welded to exhaust tube 13. Welded to the support plate 20 are the various fairing components of the device and air scoops 21 as well as air scoop support rings 22. Projecting forward from this vertical support plate 20 is outer circular fairing 23 which surrounds and may be secured to air and fuel inlet tubes 16 by connecting brackets 24.

The secondary exhaust deflection plates 25 with slightly dish configurations are secured to or constructed in exhaust tube fairing 26; air inlet holes 27 are constructed in exhaust tube fairing 26 to assist in the dissipating of heat from the space between fairing 26 and tube 13. To reinforce these two structures securing brackets 28 might well be employed for increased structural rigidity.

It is visualized that fueling for the device of this invention might be accomplished with structures as previously described in my U.S. Pat. No. 3,517,510. However, in view of the fact that the device of this invention is primarily designed for continuous operation at maximum thrust and high speeds, a somewhat simplified fueling method may be employed for providing gaseous or liquid fuels to power the device such as butane, propane, hydrogen, or a mixture of fuels. These liquid fuels would preferably be fed through a heat exchange fuel line 33 which encircles the exhaust tube 13 in a series of coils comprising a heat exchange 34. Liquified gaseous fuel passes through fuel nozzle feed line 39 into a supersonic fuel nozzle 40. These nozzles 40 are well known to the art and more completely described in my previous patent. For a brief description of this nozzle, reference is made to FIG. 4. Nozzle 40 has a minimum section 41 which projects into a nozzle flare 42. These nozzles 40, for optimum operation, must be positioned exactly at the beginning of the flare of the inlet tube bell mouth 43. To initiate operation of the device of this invention, gaseous fuel would preferably be injected into the device. After combustion is initiated by sparking plug 44 positioned in the combustion chamber forward wall 15 for maximum thrust, the device should be fueled with liquified gaseous fuel. Nose cone 17 is provided with spark plug access cover 45 and sparking plug 44 may be fired by a conventional vibrator ignition system. No timing of the spark is required and after initiation of combustion the ignition may be turned off in that the combustion is self-sustained.

For a detailed description of the improvements incorporated in the device which are elements in combination comprising the invention of this application, your attention is particularly invited to FIGS. 1, 3 and 4. The annular reverse flow vanes 46 surround inlet tube bell mouth 43 in the manner illustrated in FIGS. 1, 3, and 4. This annular reverse flow vanes 46 are arcuate conical-like structures with their largest diameter comprising the forward intake section 47 secured to the forward edge of air scoop 21. These annular reverse flow vanes 46 are constructed with an arcuate reduction cone 48 projecting into a reverse flow lip 49 which surrounds inlet tube bell mouth 43 and is secured to the bell mouth 43 by means of reverse flow vane brackets 50. These various components are perhaps best illustrated in FIG. 4. Examination of this structure of FIG. 4 in a measure illustrates the manner in which these annular reverse flow vanes 46 catch air and project it into the inlet tube bell mouths 43.

Another feature previously mentioned contributing substantially to the high speed performance of the device of this invention is the exhaust tube diffuser 60 secured to the exhaust tube nozzle 14. This exhaust tube diffuser 60 is a truncated conical structure, the base projecting forward around the exhaust tube 13 nozzle 14. The largest diameter in the forward edge comprises diffuser inlet 61. The channel between exhaust tube fairing 26 and exhaust tube diffuser 60 comprises a diffuser flow channel 62. The area of reverse flow into the nozzle 14 is designated as the diffuser intake 63. The diffuser 60 terminates at its aft end in diffuser exhaust cone 64. The device is made integral with exhaust tube nozzle 14 and exhaust tube fairing 26 by means of diffuser brackets 65.

Reference is made to my U.S. Pat. No. 3,517,510 for the relative diameters of the various components of the preferred embodiment, as well as for a description of the pulsating wave characteristics of this valveless resonant pulse-jet.

OPERATION OF THE DEVICE

When the device is fueled through nozzles 40, fuel and air are induced through the air and fuel inlet tubes 16 into combustion chamber 11. Ignition is initiated by sparking plug 44. Ignition causes a shock or thrust wave to move aft in the exhaust tube 13. The subsequent drop in pressure in the combustion chamber 11 causes induction of a new air and fuel charge through air and fuel inlet tubes 16. For low speed operation of the device of my previous invention, air scoops 21 reduced the static rate of flow of air passed the inlet tube bell mouth 43 adequately to provide air for operation of the device at stationary or moderate forward speed. At speeds above Mach 0.5 the old structure is not satisfactory. Accordingly, annular reverse flow vanes 46 surrounding bell mouth 43 and air inlet tubes 16 are required. These annular reverse flow vanes 46 will, at high forward speeds, catch and reverse the flow of air passed the intake end of the inlet tubes 16 and in effect, inject air into bell mouth 43. This characteristic of the various components of the annular reverse flow vanes 46 substantially improve the air and fuel intake characteristics at speeds above Mach .5.

A secondary component, however, is necessary to avoid combustion moving aft in the exhaust tube 13. This comprises exhaust tube diffuser 60. This diffuser 60 somewhat in the manner of annular reverse flow vanes 46 grasps and induces air adjacent the exit of exhaust tube nozzle 14. The rate of flow is decreased through diffuser flow channel 62 increasing static pressure. This increased static pressure permits air to reverse flow into the exhaust nozzle 14 restoring pressure at the nozzle 14 moving the flame forward in the exhaust tube 13 restoring thrust. The combination of the structure of the annular reverse flow vanes 46 and the exhaust tube diffuser 60 in combination with the overall device are the principal features of this invention.

By emphasizing the structural features of this improved device, I do not intend to specifically limit my claims to the exact structure described. What is desired to be claimed is all devices incorporating equivalent structures not departing from the scope of the appended claims or their equivalents.

Claims

I claim:

1. A self starting valveless pulse jet engine comprising:

a. a substantially cylindrical combustion chamber of circular cross section,

b. an elongated substantially cylindrical exhaust tube of circular cross section projecting aft from said combustion chamber constructed and arranged on a common axis with the axis of said combustion chamber,

c. a reduction cone intermediate said combustion chamber and said exhasut tube,

d. a multiplicity of straight air and fuel inlet tubes constructed in a single axis configuration mounted in said reduction cone projecting into said combustion chamber, the construction and arrangement of the combustion chamber, exhaust tube, and air fuel intake tube combination places the axis of each said element substantially parallel with the axis of each other said element,

e. an inlet tube bell mouth constructed in the respective intake ends of said air and fuel inlet tubes,

f. a multiplicity of annular reverse flow vanes spaced from and substantially encircling said inlet tube bell mouth, said annular reverse flow vanes having an arcuate configuration adapted to entrap and deflect air into said inlet tube bell mouths,

g. fuel supply means operably associated with said combustion chamber and,

h. ignition means operably associated with said combustion chamber.

2. The invention of claim 1 wherein said annular reverse flow vanes comprise:

a. an intake section projecting forward said intake section being flared and of substantially greater diameter than said fuel and air inlet tubes,

b. an arcuate reduction cone constructed in said annular reverse flow vanes projecting aft of said intake section, said arcuate reduction cone projecting aft at a progressively reduced diameter, said reverse flow vanes terminating in,

c. a reverse flow lip projecting forward substantially in the direction of the inlet tube bell mouth.

3. The invention of claim 1 including:

a. an exhaust tube nozzle secured to the aft end of said exhaust tube, and

b. an exhaust tube diffuser secured to and encircling said exhaust tube nozzle, said exhaust tube diffuser constructed and arranged to reduce the rate of flow of ambiant air adjacent said exhaust tube nozzle.

4. The invention of claim 3 wherein said exhaust tube diffuser comprises:

a. a diffuser inlet of substantially greater diameter than the diameter of said exhaust tube,

b. a diffuser flow channel projecting aft at a progressively reduced diameter, and said exhaust tube diffuser terminating in

c. a diffuser exhaust cone having a diameter less than the diameter of said diffuser inlet.

5. The invention of claim 1 wherein said combustion chamber includes a substantially flat forward wall normal to the axis of said exhaust tube.

6. The invention of claim 1 wherein the said air and fuel inlet tubes are substantially equiangular positioned in said combustion chamber.

7. The invention of claim 1 wherein the fuel supply means includes a convergent-divergent supersonic fuel nozzle positioned in the inlet end of said air and fuel inlet tubes.

8. The invention of claim 1 including a fuel nozzle positioned in substantially the center of said bellmouth at its juncture with said air and fuel inlet tube.

9. The invention of claim 5 wherein the said ignition means includes a spark plug positioned in the said forward wall at a position substantially in prolongation of the axis of one of the said air and fuel inlet tubes.

10. The invention of claim 1 wherein the dimensional proportions are relatively:

a. the diameter of the combustion chamber is substantially twice the diameter of the exhaust tube,

b. the combustion chamber, combustion chamber reduction cone, and exhaust tube combination is substantially fifteen (15) exhaust tube diameters in length,

c. the length of each of the air and fuel inlet tubes is one-fourth (1/4) the length of the combustion chamber, combustion chamber reduction cone, and the exhaust tube combination, and

d. the total cross-sectional intake area of the said air and fuel inlet tubes is one-third of the cross-sectional area of the said exhaust tube.