Rotary device and a method of designing and making a rotary device

Abstract

The invention provides a rotary device comprising a first rotor rotatable about a first axis and having at its periphery a recess bounded by a curved surface, and a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having a radial lobe bounded by a curved surface, the first and second rotors being coupled for intermeshing rotation, wherein the first and second rotors of each section intermesh in such a manner that on rotation thereof, a transient chamber of variable volume is defined, the transient chamber having a progressively increasing or decreasing volume between the recess and lobe surfaces, the transient chamber being at least in part defined by the surfaces of the lobe and the recess; the ratio of the maximum radius of the lobe rotor and the maximum radius of the recess rotor being greater than 1.

1 .- 15 . (canceled) 
     
     
         16 . A rotary device comprising a first rotor rotatable about a first axis and having at its periphery a recess bounded by a curved surface, and a second rotor counter-rotatable to said first rotor about a second axis, parallel to said first axis, and having a radial lobe bounded by a curved surface, the first and second rotors being coupled for intermeshing rotation, wherein
 the first and second rotors of each section intermesh in such a manner that on rotation thereof, a transient chamber of variable volume is defined for acting on working fluid in order to reduce its volume in the case of compression or for being acted on by working fluid to allow increase in its volume in the case of expansion, the transient chamber being defined between interacting surfaces of the lobe and recess rotor, the transient chamber having a progressively decreasing or increasing volume between the recess and lobe surfaces, the transient chamber being at least in part defined by the surfaces of the lobe and the recess;   a ratio of the maximum radius of the lobe rotor and the maximum radius of the recess rotor being greater than 1 thereby increasing the swept volume per cycle of interaction as compared to if the ratio was less than or equal to one.   
     
     
         17 . The rotary device according to  claim 16 , wherein the ratio of the maximum radius of the lobe rotor and the maximum radius of the recess rotor is between 1.1 and 1.5. 
     
     
         18 . The rotary device according to  claim 17 , wherein the ratio of the maximum radius of the lobe rotor and the maximum radius of the recess rotor is about 1.3. 
     
     
         19 . The rotary device according to  claim 16 , wherein a housing is provided to enclose the rotors. 
     
     
         20 . The rotary device according to  claim 19 , wherein the housing includes a moveable containment wall, said wall being moveable so as to vary the maximum possible volume of the transient chamber of variable volume. 
     
     
         21 . The rotary device according to  claim 16 , wherein the rotors extend axially in a helical configuration. 
     
     
         22 . The rotary device according to  claim 16 , wherein the geometry of the or each lobe is determined by an inner radius of the lobe ρ Li , an outer rotor radius at a tip of the lobe ρ Lo , an outer radius of the recess rotor ρ Po , and a circular arc segment A l  of radius R l  defining a bulk of the lobe. 
     
     
         23 . The rotary device according to  claim 22 , wherein the geometry of the or each lobe is, in addition, determined by a circular arc segment A c  of radius R c  wherein the arc segment A l  defines the bulk of the lobe from its tip to an inflection point and the circular arc segment A c  defines a base of the lobe connecting between the arc segment A l  and a core of the lobe. 
     
     
         24 . The rotary device according to  claim 22 , wherein a position of the centre of the circular arc segment A l  is defined in dependence on the separation of the centre of the circular arc segment A l  from the centre of the lobe rotor. 
     
     
         25 . The rotary device according to  claim 16 , wherein the lobe profile comprises plural arc segments. 
     
     
         26 . One or more of an engine, a compressor, an expander, and a supercharger each comprising a rotary device according to  claim 16 . 
     
     
         27 . A method of designing the rotors for a rotary device having a lobe rotor and a recess rotor coupled for intermeshing rotation, wherein the lobe and recess rotors intermesh in such a manner that on rotation thereof, a transient chamber of variable volume is defined, the transient chamber having a progressively increasing or decreasing volume between the recess and lobe surfaces, the method comprising:
 determining the geometry of the or each lobe in dependence on an inner radius of the lobe ρ Li , an outer rotor radius at the tip of the lobe ρ Lo , and a circular arc segment A l  of radius R l  defining a bulk of the lobe and an outer radius of the recess rotor ρ Po .   
     
     
         28 . The method according to  claim 27 , wherein the geometry of the or each lobe is, in addition, determined by a circular arc segment A c  of radius R c  wherein the arc segment A l  defines the bulk of the lobe from its tip to an inflection point and the circular arc segment A c  defines a base of the lobe connecting between the arc segment A l  and a core of the lobe. 
     
     
         29 . The method according to  claim 27 , comprising making a lobe rotor having the determined geometry. 
     
     
         30 . The method according to  claim 29 , comprising making the recess rotor to correspond with the lobe rotor.