Abstract:
A jet engine is constructed of a fanjet; a plurality of ramjets provided around said fanjet; a plurality of air flow spaces between said fanjet and said plurality of ramjets; and a cooling jacket provided around said plurality of ramjets.

Description:
FIELD 
     The present invention relates to jet engines. More particularly, the present invention relates to a jet engine which is capable of fuel-efficient subsonic and supersonic propulsion. 
     BACKGROUND 
     Jet aircraft utilize a variety of jet engines depending on the type of aircraft. Subsonic passenger jet aircraft are typically fitted with multiple fanjets, each of which includes a housing having a front intake, a rear nozzle and a central shaft rotatably mounted in the housing between the intake and nozzle. Multiple compressor fans are provided on the shaft inside the housing, and a combustion chamber is situated in the housing behind the compressor fans. In operation, air enters the fanjet through the intake of the housing. The compressor fans compress and expel the air into the combustion chamber. Jet fuel is injected into the combustion chamber and ignited with the compressed air, and the resultant expanding gases are violently ejected through the nozzle, propelling the aircraft forward. 
     Other types of aircraft, including military aircraft and other types of high-speed or supersonic aircraft, for example, commonly utilize ramjets, which have no compressor fans or other moving parts. Ramjets operate by utilizing compressed air that flows into the ramjet due to the aircraft moving forwardly at high speeds. Because fanjets utilize some of the burning fuel to rotate the compressor fans, ramjets are typically more fuel efficient at high speeds due to the lack of moving parts. 
     SUMMARY 
     The present invention is generally directed to a jet engine. An illustrative embodiment of the jet engine includes a fanjet and a plurality of ramjets provided around the fanjet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a longitudinal sectional view of an illustrative embodiment of a jet engine; and 
         FIG. 2  is a front view of an illustrative embodiment of a jet engine. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, an illustrative embodiment of a jet engine is generally indicated by reference numeral  1 . The jet engine  1  is fuel efficient and suitable for use in a variety of applications, including but not limited to military aircraft and supersonic passenger aircraft. 
     As shown in  FIG. 1 , the jet engine  1  includes a central fanjet  2 . The fanjet  2  may have a conventional design, typically including an elongated cowling  3 . Multiple fanjet supports  12  may be provided to facilitate attachment of the fanjet  2  to a frame (not shown) of an aircraft (not shown). An elongated engine housing  4  is provided in the cowling  3 . The engine housing  4  typically includes an intake  4   a  at the front end thereof. A cone  8  is mounted in the engine housing  4  and is movable between a forward or extended position shown in  FIG. 1  in which the cone  8  engages the engine housing  4  and seals the intake  4   a  and a rear or retracted position (not shown) in which the cone  8  disengages the engine housing  4  and opens the intake  4   a . The cone  8  may be adapted to move in the engine housing  4  using any suitable cone displacing mechanism (not shown). For example, the cone displacing mechanism may utilize pressurized oil to move the cone  8  between the extended and retracted positions. 
     A compressor chamber  13  is provided in the engine housing  4 , behind the intake  4   a . A central fan shaft  5  is rotatably mounted in the engine housing  4 , typically in conventional fashion according to the knowledge of those skilled in the art, and extends through the compressor chamber  13 . Multiple compressor fans  6  are mounted on the fan shaft  5  for rotation therewith inside the compressor chamber  13 . Multiple stator fans  6   a  are also mounted in the compressor chamber  13 , adjacent to the compressor fans  6 . The stator fans  6   a  remain stationary with respect to the compressor fans  6  as the compressor fans  6  rotate with the fan shaft  5 . A starting air valve  7  may be provided in the compression chamber  13  to control the volume of air flowing through the compressor fans  6 . 
     A combustion chamber  10  is provided in the engine housing  4 , behind the compressor chamber  13 . Multiple fuel injection nozzles and igniter (not shown) are provided in the combustion chamber  10  to inject jet fuel (not shown) into the combustion chamber  10  and ignite the fuel. Multiple cooling surfaces  9  may be provided in the combustion chamber  10  to enhance cooling of the engine housing  4 . A nozzle  11  is provided at the rear end of the engine housing  4 , behind the combustion chamber  10 . 
     As shown in  FIG. 2 , multiple subsonic ramjets  16  and supersonic ramjets  24  are provided in adjacent relationship to each other around the circumference of the fanjet  2 . The subsonic ramjets  16  and supersonic ramjets  24  may be provided around the circumference of the fanjet  2 , in alternating relationship to each other. In the embodiment shown in  FIG. 2 , four subsonic ramjets  16  and four supersonic ramjets  24  alternate with each other around the fanjet  2 , although this number of subsonic ramjets  16  and supersonic ramjets  24  may vary. As used herein, the term “subsonic ramjet” means any ramjet which is capable of sustained operation at subsonic or both subsonic and supersonic speeds. As used herein, the term “supersonic ramjet” means any ramjet which is capable of sustained operation at supersonic speeds. 
     As shown in  FIG. 1 , each subsonic ramjet  16  may have a conventional ramjet design and typically includes an elongated subsonic ramjet housing  17 . The subsonic ramjet housing  17  includes an intake  18 , a combustion chamber  19  behind the intake  18  and a subsonic ramjet nozzle  20  behind the combustion chamber  19 , at the rear end of the subsonic ramjet housing  17 . The subsonic ramjet housing  17  includes the components (not shown), such as multiple fuel injection nozzles and igniter, necessary to render functionality to the subsonic ramjet  16 . 
     As shown in  FIG. 1 , each supersonic ramjet  24  may have a conventional ramjet design and typically includes an elongated supersonic ramjet housing  25 . The subsonic ramjet housing  25  includes an intake  26 , a combustion chamber  27  behind the intake  26  and a subsonic ramjet nozzle  28  behind the combustion chamber  27 , at the rear end of the subsonic ramjet housing  25 . The supersonic ramjet housing  25  includes the components (not shown), such as fuel injection nozzle and igniter, necessary to render functionality to the supersonic ramjet  24 . 
     As shown in  FIGS. 1 and 2 , a cooling jacket  32  may be attached to the subsonic ramjet housings  17  and supersonic ramjet housings  25 . The cooling jacket  32  surrounds the subsonic ramjets  16  and supersonic ramjets  24  to direct flowing air adjacent to the subsonic ramjets  16  and supersonic ramjets  24  during operation of the jet engine  1 , for cooling purposes. Air flow spaces  30  may be provided between the fanjet  2  and each subsonic ramjet  16  and supersonic ramjet  24  for cooling purposes. 
     Controls (not shown) for the fanjet  2 , the subsonic ramjets  16  and the supersonic ramjets  24  are provided typically in the cockpit (not shown) in the aircraft (not shown) on which the jet engine  1  is mounted. The fuel supply, hydraulic supply, pressurization and electrical power for the jet engine  1  may be provided by an auxiliary power unit (not shown), typically in conventional fashion. 
     In typical application, one or multiple jet engines  1  is/are provided on a frame or body (not shown) of an aircraft (not shown). Each jet engine  1  is connected to the appropriate fuel, hydraulic and electrical power supplies (not shown) of the aircraft, according to the knowledge of those skilled in the art. In use of the jet engine  1 , the fanjet  2  is initially operated to propel the aircraft forwardly at subsonic speeds. Accordingly, the cone  8  is moved to the extended or forward position (not shown) to open the intake  4   a  of the engine housing  4 . The fan shaft  5  is rotated to rotate the compressor fans  6  relative to the stator fans  6   a  in the compression chamber  13  of the engine housing  4 . Accordingly, air (not shown) is drawn into the engine housing  4  through the intake  4   a , compressed by the compressor fans  6  and stator fans  6   a  in the compression chamber  13  and ejected into the combustion chamber  10 , respectively. Jet fuel (not shown) is injected into the combustion chamber  10  through the fuel injection nozzles (not shown), mixed with the compressed air and ignited. The burning gases expand in the combustion chamber  10  and are violently ejected through the nozzle  11  to propel the jet engine  1  and aircraft (not shown) forwardly. 
     As the jet engine  1  moves forwardly under operation of the fanjet  2 , air (not shown) enters the intake  18  of each subsonic ramjet  16 . When the forward speed of the jet engine  1  is such that the pressure of the air flowing into the intake  18  of each subsonic ramjet  16  is sufficient to initiate and sustain operation of the subsonic ramjets  16 , operation of the subsonic ramjets  16  is initiated. Simultaneously, operation of the fanjet  2  is terminated. The cone  8  may be retracted in the engine housing  4  to close the intake  4   a  of the fanjet  2 . In operation of the subsonic ramjets  16 , jet fuel (not shown) is injected into the combustion chamber  19  of each subsonic ramjet  16  through the fuel injection nozzles (not shown) and ignited. The burning gases expand in the combustion chamber  19  and are violently ejected from the nozzle  20  of each subsonic ramjet  16 , propelling the jet engine  1  and aircraft forwardly at speeds which approach, reach and then surpass the speed of sound. 
     When the forward speed of the jet engine  1  is such that the pressure of the air flowing into the intake  26  of each supersonic ramjet  24  is sufficient to initiate and sustain operation of the supersonic ramjets  24 , operation of the supersonic ramjets  24  is initiated. Simultaneously, operation of the subsonic ramjets  16  is terminated. In operation of the supersonic ramjets  24 , jet fuel (not shown) is injected into the combustion chamber  27  of each supersonic ramjet  24  through the fuel injection nozzles (not shown) and ignited. The burning gases expand in the combustion chamber  27  and are violently ejected from the nozzle  28  of each supersonic ramjet  24 , propelling the jet engine  1  and aircraft forwardly at speeds which surpass the speed of sound and reach the cruising altitude of the aircraft. Throughout operation of the fanjet  2 , air flows through the air flow spaces  30 , thereby cooling the fanjet  2 . Throughout operation of the subsonic ramjets  16  and supersonic ramjets  24 , air flows through the air flow spaces  30  and cooling jacket  32 , thereby cooling the subsonic ramjets  16  and supersonic ramjets  24 . 
     Shutting down of the jet engine  1  is accomplished by slowing the forward speed of the jet engine  1  to speeds which are sufficient to sustain operation of the subsonic ramjets  16 , at which time the supersonic ramjets  24  are shut down. The forward speed of the jet engine  1  is further slowed to speeds which are sufficient to sustain operation of the fanjet  2 , at which time the subsonic ramjets  16  are shut down. Finally, the fanjet  2  is shut down after landing of the aircraft. 
     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.