Roots supercharger with a shunt pulsation trap

Abstract

A shunt pulsation trap for a Roots supercharger reduces pulsation, NVH and improves efficiency without significantly increasing overall size of the supercharger. Generally, a Roots supercharger with the shunt pulsation trap has a pair of interconnected and synchronized parallel multi-helical-lobe rotors housed in a transfer chamber with the same number of lobes for propelling flow from a suction port to a discharge port of the transfer chamber without internal compression. The shunt pulsation trap comprises an inner casing as an integral part of the transfer chamber, and an outer casing oversized surrounding the inner casing, therein housed various pulsation dampening means or pulsation energy recovery means or pulsation containment means, at least one injection port (trap inlet) branching off from the transfer chamber into the pulsation trap chamber and a feedback region (trap outlet) communicating with the supercharger outlet pressure.

1 . A Roots supercharger with a shunt pulsation trap apparatus, comprising:
 a. a housing structure having an inner casing with a flow suction port, a flow discharge port and a transfer chamber there-between, and at least one injection port located at least one lobe span away from said flow suction port communicating with said transfer chamber and at least one feedback region communicating with said flow discharge port, and an outer casing enclosing said inner casing;   b. two parallel multi-helical-lobe rotors having same number of lobes and rotatably mounted on two parallel rotor shafts respectively inside said inner casing and interconnected through a set of timing gears to rotate in synchronization for propelling flow from said suction port to said discharge port:   c. a shunt pulsation trap apparatus comprising said inner casing as an integral part of said transfer chamber, and said outer casing oversized surrounding said inner casing, therein housed various pulsation dampening means or pulsation energy recovery means or pulsation containment means, at least one trap inlet (said injection port) branching off from said transfer chamber into said pulsation trap and at least one trap outlet (said feedback region) communicating with said supercharger discharge port;   d. whereby said Roots supercharger is capable of achieving high pulsation and NVH reduction at source and improving supercharger efficiency while being kept light in mass, compact in size and suitable for both mobile and stationary applications at the same time.   
     
     
         2 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said multi-helical-lobe rotor is of twisted shape in its axial direction and having at least three or more lobes per rotor. 
     
     
         3 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said injection port (trap inlet) is at least one lobe span away from said supercharger suction opening and has a converging cross-sectional shape or a converging-diverging cross-sectional (De Laval nozzle) shape in feedback flow direction. 
     
     
         4 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means comprises at least one layer of perforated plate or acoustical absorption materials or other similar types for turning pulsation into heat. 
     
     
         5 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means comprises at least one layer of perforated plate on which there is at least one synchronized valve that is closed and opened as said each lobe passes said trap inlet. 
     
     
         6 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means comprises at least one Helmholtz resonator. 
     
     
         7 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means comprises at least one Helmholtz resonator in parallel with at least one layer of perforated plate or acoustical absorption materials or other similar types for turning pulsation into heat. 
     
     
         8 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means comprises at least one Helmholtz resonator in parallel with at least one synchronized valve that is closed and opened as each said lobe passes said trap inlet. 
     
     
         9 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means and said energy recovery means comprise at least a diaphragm or a piston or other similar types in parallel with at least one layer of perforated plate or acoustical absorption materials or other similar types for partially turning pulsation into heat and partially absorbing pulsation energy and turning that energy into pumping air from said trap outlet through said perforated plate into said trap. 
     
     
         10 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means and energy recovery means comprise at least a diaphragm or a piston or other similar types in parallel with an opening for absorbing pulsation energy and turning that energy into pumping air from said trap outlet through said opening into said trap. 
     
     
         11 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means and energy recovery means comprise at least a diaphragm or a piston or other similar types synchronized with at least one valve for absorbing pulsation energy and turning that energy into pumping air from said trap outlet through said valve into said trap. 
     
     
         12 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means and energy recovery means comprise at least a diaphragm or a piston or other similar types synchronized with at least one valve for absorbing pulsation energy and turning that energy into driving an externally connected load. 
     
     
         13 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation dampening means and energy recovery means comprise at least a diaphragm or a piston or other similar types synchronized with at least two valves, one at trap inlet, the other at trap outlet, for absorbing pulsation energy and turning that energy into driving an externally connected load. 
     
     
         14 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation trap further comprises at least one perforated plate located at said suction port or at least one perforated plate located at said discharge port or both either before or alternatively after said trap outlet 
     
     
         15 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation containment means comprises at least one control valve located at said trap outlet. 
     
     
         16 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 1 , wherein said pulsation containment means comprises at least one layer of perforated plate or acoustical absorption materials or other similar types for turning pulsation into heat, in series with at least one control valve located at said trap outlet. 
     
     
         17 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 15  or  16 , wherein said control valve in said pulsation containment means is a one way valve, like a reed valve. 
     
     
         18 . The Roots supercharger with shunt pulsation trap apparatus as claimed in  claim 15  or  16 , wherein said control valve in said pulsation containment means is a rotary valve that is timed to close and open as each said lobe passes said trap inlet. 
     
     
         19 . The perforated plate as claimed in  claim 14  has holes with a cross-sectional shape of either constant area or converging shape or a converging-diverging (De Laval nozzle) shape in flow direction.