Method of eliminating mach waves from supersonic jets

Abstract

A method and device for reducing the amount of noise generated by a supersonic jet engine is provided. The method creates an envelope of air around the supersonic jet exhaust. The temperature and velocity of this envelope is controlled to eliminate or reduce the formation of noise making Mach waves.

1. A jet engine which produces a supersonic stream of air, said engine  comprising:
 a structure adapted to provide a compression ratio sufficient to produce a supersonic thrust; 
 an air intake end and an exhaust end;  
 said  exhaust end having a partition that divides said  an exhaust end  stream into a  first side  and a  second side such that a  streams, the first stream exits said exhaust end on said first side and a second stream of heated air exits said exhaust end on said second side;  
 a combustion chamber for heating adapted to heat said first stream such that said first stream is expelled from said exhaust end of said engine to produce said supersonic thrust; and  being supersonic; and  
 a heating  control mechanism adapted to heat said second stream such that said second stream is expelled from said exhaust end of said jet engine to produce a subsonic thrust adjacent to said first thrust and thereby prevent Mach waves from said supersonic thrust  to control at least one of temperature and velocity of the second stream such that the second stream is subsonic.  
 
     
     
       2. The jet engine of claim  1    26 , wherein said first and second stream  streams pass through said combustion chamber before said partition separates said first stream from said second stream; after said separation, said heating mechanism designed to further heat said second stream . 
     
     
       3. The jet engine of  claim 1  wherein said jet engine is a turbojet engine. 
     
     
       4. The jet engine of  claim 1  wherein said jet engine is a turbofan engine. 
     
     
       5. The jet engine of  claim 1 , wherein said heating  control mechanism is  comprises a suppression burner, said suppression burner being designed to heat the air by burning a fuel. 
     
     
       6. The jet engine of  claim 1 , wherein said heating  control mechanism is  comprises a variable compression ratio fan which can change its  having a variable compression ratio and produce heat . 
     
     
       7. The jet engine of claim  1    25 , wherein said partition is an inner shell core of a jet engine . 
     
     
       8. The jet engine of claim  1    25 , wherein said partition further has louvers or apertures which can be opened to allow mixing of said first and said second stream  streams. 
     
     
       9. The jet engine of  claim 1 , wherein said jet engine  first stream is at least partially surrounded by a shroud, said shroud forming a confining wall for said second stream. 
     
     
       10. The jet engine of  claim 1 , wherein said heating  control mechanism is  comprises a divider which diverts said first stream to entirely form or to mix with said second stream. 
     
     
       11. The jet engine of  claim 10 , wherein said jet engine has a second divider which further divides said second stream from a third stream; and
 a heating mechanism adapted to heat said third stream to a temperature different from that of said second stream, such that said third stream is also expelled from said exhaust end of said jet engine to produce a third thrust adjacent to said second thrust and thereby prevent Mach waves from said second thrust  control mechanism controls at least one of temperature and velocity of a third stream to control Mach wave formation from the second stream, the third stream being divided from the air.  
 
     
     
       12. The jet engine of claim  1    25 , wherein said first stream has a circular or elliptical cross section at a plane, said plane located at said exhaust end of said jet engine . 
     
     
       13. The jet engine of claim  1    25 , wherein said first stream has a rectangular cross section at a plane located at said exhaust end of said jet engine . 
     
     
       14. A jet engine in use propelling an aircraft at a supersonic speed together with the exhaust stream thereof, said engine  comprising:
 an air intake end and an exhaust end  to intake air, the air being divided into at least first and second streams; and  
 a first passage and a second passage extending between said air intake end and said exhaust end;  
 a combustion chamber in fluid communication with and located along said first passage such that a portion of said first passage is disposed to receive a first flow of exhaust between said combustion chamber and said exhaust end;  
 said first flow of exhaust forming said supersonic exhaust stream upon exiting said engine;  
 a heating  control mechanism in fluid communication with and located along said second passage such that a portion of said second passage is disposed to receive a second flow of exhaust between said heating mechanism and said exhaust end;  
 said second flow of exhaust forming a subsonic exhaust stream upon exiting said engine; and  
 said supersonic exhaust stream at least partially enveloped by said subsonic exhaust stream  to control at least one of temperature and velocity of at least one of the first and second streams such that the first and second streams form supersonic and subsonic streams upon exiting an exhaust end, the subsonic stream at least partially surrounding the supersonic stream.  
 
     
     
       15. The jet engine of  claim 14  wherein said jet engine is a turbofan engine. 
     
     
       16. The jet engine of claim  14    29 , wherein said heating mechanism is a suppression burner, said suppression burner being designed to heat the air by burning a fuel. 
     
     
       17. The jet engine of claim  14    29 , wherein said second passage substantially encloses said first passage. 
     
     
       18. The jet engine of claim  14    29 , wherein said jet engine is at least partially surrounded by a shroud, said shroud defining an exterior wall of said second passage. 
     
     
       19. The jet engine of claim  1    14 , wherein said first exhaust  stream has a circular or elliptical cross section at a plane, said plane located at said exhaust end of said engine . 
     
     
       20. The jet engine of  claim 1  wherein the control mechanism controls velocity of turbulent eddies of the first stream to be subsonic relative to the second stream. 
     
     
       21. The jet engine of  claim 1  wherein the control mechanism controls velocity of turbulent eddies of the second stream to be subsonic relative to an ambient stream. 
     
     
       22. The jet engine of  claim 1  wherein the control mechanism controls the temperature of the second stream to be greater than ( B*M   1 /(   1 +M   2 )) 2   *T   1   , wherein B is a ratio between eddy velocity and stream velocity, M   1    is air velocity of the first stream divided by a first speed of sound in the first stream, M   2    is air velocity of the second stream divided by a second speed of sound in the second stream, and T   1    is temperature of air in the first stream.   
     
     
       23. The jet engine of  claim 1  wherein the control mechanism controls the temperature of the second stream to be less than T a *((   1 +M   a )/( B*M   2 )) 2   , wherein B is a ratio between eddy velocity and stream velocity, M   a    is air velocity of ambient air surrounding said second stream divided by ambient speed of sound, M   2    is air velocity of the second stream divided by a second speed of sound in the second stream, and T   a    is temperature of said ambient air surrounding said second stream.   
     
     
       24. The jet engine of  claim 1  wherein the control mechanism controls the temperature of the second stream to be greater than ( B*M   1 /(   1 +M   2 )) 2   *T   1    and less than T   a *((   1 +M   a )/( B*M   2 )) 2   , wherein B is a ratio between eddy velocity and stream velocity, M   1    is air velocity of the first stream divided by a first speed of sound in the first stream, M   2    is air velocity of the second stream divided by a second speed of sound in the second stream, T   1    is temperature of air in the first stream, T   a    is temperature of said ambient air surrounding said second stream, and M   a    is air velocity of ambient air surrounding said second stream divided by ambient speed of sound.   
     
     
       25. The jet engine of  claim 1  further comprising:
   an exhaust end having first and second sides divided by a partition to allow the first and second streams exiting on said first and second sides.     
     
     
       26. The jet engine of  claim 25  further comprising:
   a combustion chamber to heat said first stream such that said first stream is expelled from said exhaust end to produce a supersonic thrust.     
     
     
       27. The jet engine of  claim 25  wherein the control mechanism comprises:
   a heating mechanism to heat said second stream such that the velocity of the turbulent eddies of the second stream is subsonic relative to an ambient stream.     
     
     
       28. The jet engine of  claim 14  further comprising:
   a combustion chamber located along a first passage such that a portion of said first passage is disposed to receive a first flow between said combustion chamber and said exhaust end, the first flow forming said supersonic stream.     
     
     
       29. The jet engine of  claim 28  wherein the control mechanism comprises:
   a heating mechanism located along a second passage such that a portion of said second passage is disposed to receive a second flow between said heating mechanism and said exhaust end, said second flow forming the subsonic stream.