Optimized helix angle rotors for roots-style supercharger

Abstract

A Roots-type blower has first and second meshed, lobed rotors disposed in first and second chambers of a housing. Each lobe has first and second axially facing end surfaces defining a twist angle that is a function, at least partially, of the number of lobes on each rotor, and each lobe further defines a helix angle that is a function of the twist angle and an axial length between the first and second axially facing end surfaces of said lobe. The lobes cooperate with an adjacent surface of the housing to define at least one blowhole that defines a control volume, occurs in a cyclic manner, and moves linearly in a direction toward the outlet port. The blowhole provides communication between adjacent control volumes.

1 - 5 . (canceled) 
     
     
         6 . An internally compressing Roots blower comprising:
 a blower housing comprising a plurality of rotor chambers and a plurality of rotors;   wherein the rotors and the blower housing are configured to create internal fluid compression when the rotors are rotating at a first rotational speed and not to create internal fluid compression when the rotors are rotating at a second rotational speed.   
     
     
         7 . The internally compressing Roots blower of  claim 6 , including a plurality of cyclically occurring internal backflow passages. 
     
     
         8 . The internally compressing Roots blower of  claim 7 , wherein the plurality of cyclically occurring internal backflow passages are configured to permit a continuous backflow event. 
     
     
         9 . The internally compressing Roots blower of  claim 7 , wherein the cyclically occurring internal backflow passages are configured to move linearly in a direction toward an inlet port. 
     
     
         10 . The internally compressing Roots blower of  claim 6 , wherein the blower is configured to produce a boost ratio of at least  2 . 4  before reaching a critical temperature. 
     
     
         11 . A blower comprising
 a blower housing; and   a plurality of rotors disposed in the blower housing;   wherein the blower housing and the rotors are configured to generate a plurality of cyclically occurring internal backflow passages configured to permit a continuous backflow event.   
     
     
         12 . The blower of  claim 11 , wherein the plurality of cyclically occurring internal backflow passages comprises at least three cyclically occurring internal backflow passages. 
     
     
         13 . The blower of  claim 11 , wherein the plurality of cyclically occurring internal backflow passages are configured to permit a continuous backflow event. 
     
     
         14 . The blower of  claim 11 , wherein the cyclically occurring internal backflow passages are configured to move linearly in a direction toward an inlet port. 
     
     
         15 . The blower of  claim 11 , wherein each of the plurality of rotors comprises a plurality of lobes, and wherein each of the plurality of lobes includes a maximum ideal twist angle that does not open a leak path between inlet and outlet ports of the blower housing. 
     
     
         16 . The blower of  claim 15 , wherein the maximum ideal twist angle is at least 170 degrees. 
     
     
         17 . The blower of  claim 15 , wherein each of the rotors includes a helix angle of about 29 degrees. 
     
     
         18 . A Roots blower comprising:
 a plurality of rotors having a plurality of lobes; and   a blower housing comprising:
 a plurality of rotor chambers, 
 an axial inlet port in a first end wall, and 
 a plurality of control volumes; 
 wherein the axial inlet port is in communication with four control volumes. 
   
     
     
         19 . The Roots blower of  claim 18 , wherein each of the plurality of control volumes is disposed between two adjacent unmeshed lobes of the plurality of lobes. 
     
     
         20 . The Roots blower of  claim 18 , wherein each of the plurality of control volumes corresponds to a trailing lobe and a leading lobe of the plurality of lobes. 
     
     
         21 . The Roots blower of  claim 20 , wherein the leading and trailing lobes corresponding to each of the plurality of control volumes are disposed between inlet and outlet cusps of the blower housing. 
     
     
         22 . The Roots blower of  claim 18 , comprising a plurality of cyclically occurring internal backflow passages. 
     
     
         23 . The Roots blower of  claim 22 , wherein the plurality of cyclically occurring internal backflow passages are configured to permit a continuous backflow event. 
     
     
         24 . The Roots blower of  claim 22 , wherein the cyclically occurring internal backflow passages are configured to move linearly in a direction toward an inlet port. 
     
     
         25 . The Roots blower of  claim 18 , wherein each of the plurality of rotors comprises a plurality of lobes, and wherein each of the plurality of lobes includes a maximum ideal twist angle that does not open a leak path between inlet and outlet ports of the blower housing.