Volumetric energy recovery device and systems

Abstract

A volumetric expander ( 20 ) configured to transfer a working fluid and generate useful work includes a housing. The housing includes an inlet port ( 24 ) configured to admit relatively high-pressure working fluid and an outlet port ( 26 ) configured to discharge to a relatively low-pressure working fluid. The expander also includes first and second twisted meshed rotors ( 30,32 ) rotatably disposed in the housing and configured to exp/and the relatively high-pressure working fluid into the relatively low-pressure working fluid. Each rotor has a plurality of lobes, and when one lobe of the first rotor is leading with respect to the inlet port, one lobe of the second rotor is trailing with respect to the inlet port. The expander additionally includes an output shaft ( 38 ) rotated by the relatively high-pressure working fluid as the fluid undergoes expansion. A system for generating work using the expander in a Rankine cycle is also disclosed.

1 . A system used to generate useful work via a closed-loop Rankine cycle, the system comprising:
 a condenser configured to condense a working fluid;   a fluid pump configured to pressurize the working fluid;   a heat exchanger configured to heat the working fluid; and   a volumetric fluid expander configured to receive the working fluid from the heat exchanger, generate the work, and transfer the working fluid to the condenser, the expander including:
 a housing having an inlet port configured to admit relatively high-pressure working fluid and an outlet port configured to discharge into relatively low-pressure working fluid; 
 first and second twisted meshed rotors rotatably disposed in the housing and configured to expand the relatively high-pressure working fluid into the relatively low-pressure working fluid, wherein each rotor has a plurality of lobes; and 
 an output shaft operatively connected to one of the first and second rotors and rotated by the working fluid as the working fluid undergoes expansion. 
   
     
     
         2 . The system of  claim 1 , being characterized by the absence of a superheat boiler provided to take the working fluid into superheated range and evaporate all liquid from the working fluid. 
     
     
         3 . The system of  claim 2 , wherein when useful work is generated during the Rankine cycle, the working fluid is present in two phases within the expander, such that conversion efficiency of the Rankine cycle is increased via the working fluid sealing internal clearances between the first and second rotors, and between the rotors and the housing. 
     
     
         4 . The system of  claim 1 , wherein the system is used in a vehicle having an internal combustion engine with an exhaust system, and wherein the heat exchanger is in fluid communication with the exhaust system. 
     
     
         5 . The system of  claim 1 , wherein the system is used in a vehicle having a solid oxide fuel cell. 
     
     
         6 . The system of  claim 1 , further comprising a load storage device, wherein the mechanical work generated by the expander is accumulated in the load storage device for subsequent release on demand. 
     
     
         7 . The system of  claim 6 , wherein the load storage device is one of an pneumatic accumulator, a hydraulic accumulator, and an electric battery. 
     
     
         8 . The system of  claim 1 , wherein the inlet port includes an inlet angle of incidence relative to the trailing lobe that is substantially parallel to the surface plane of the trailing lobe when the trailing lobe is rotated and presented to the working fluid. 
     
     
         9 . The system of  claim 1 , wherein the expander includes first and second meshed timing gears fixed relative to the first and second meshed rotors, respectively, that are configured to prevent contact between the rotors. 
     
     
         10 . A volumetric fluid expander configured to transfer a working fluid and generate useful work, the expander comprising:
 a housing having an inlet port configured to admit relatively high-pressure working fluid and an outlet port configured to discharge into relatively low-pressure working fluid;   first and second twisted meshed rotors rotatably disposed in the housing and configured to expand the relatively high-pressure working fluid into the relatively low-pressure working fluid, wherein each rotor has a plurality of lobes defining a helix angle; and   an output shaft having a rotational axis that is configured to be rotated by the relatively high-pressure working fluid as the working fluid undergoes expansion;   wherein the helix angle is between about 25 degrees and about 40 degrees and the inlet angle is both oblique with respect to the shaft rotational axis and has a value that is within about 15 degrees of the helix angle.   
     
     
         11 . The fluid expander of  claim 10 , wherein the inlet angle is about 30 degrees. 
     
     
         12 . The fluid expander of  claim 10 , wherein the helix angle is about 35 degrees. 
     
     
         13 . The fluid expander of  claim 11 , wherein the inlet angle is about 30 degrees. 
     
     
         14 . The fluid expander of  claim 13 , wherein each of the rotors has a twist angle of about 120 degrees. 
     
     
         15 . The fluid expander of  claim 10 , wherein the inlet angle is oblique with respect to a rotational axis of the output shaft. 
     
     
         16 . The fluid expander of  claim 10 , wherein the outlet port is includes an outlet angle that is oblique with respect to a longitudinal axis of the rotors. 
     
     
         17 . An energy recovery system:
 a power source that generates a waste heat stream, the power source having a power input location;   a volumetric energy recovery device configured to transfer energy from the waste heat stream to the power input location, the volumetric energy recovery device including:
 a housing having an inlet port and an outlet port; 
 first and second twisted meshed rotors in fluid communication with the inlet and outlet ports, the rotors being rotatably disposed in the housing wherein a first rotational axis of the first twisted rotor is parallel to a second rotational axis of the second twisted rotor; 
 an output shaft operatively connected to one of the first and second rotors and to the power input location of the power source, the output shaft being rotated by power from the waste heat stream. 
   
     
     
         18 . The energy recovery system of  claim 17 , wherein the waste heat stream is in fluid communication with a working fluid and wherein the working fluid is in fluid communication with the volumetric energy recovery device via the inlet and outlet ports. 
     
     
         19 . The energy recovery system of  claim 17 , wherein the working fluid is an organic fluid. 
     
     
         20 . The energy recovery system of  claim 19 , wherein the working fluid is subjected to a Rankine cycle in which at least a portion of the working fluid is expanded from a liquid state to a vapor state within the energy recovery device. 
     
     
         21 . The energy recovery system of  claim 17 , wherein the power source is an internal combustion engine and the waste heat stream is an engine exhaust stream. 
     
     
         22 . The energy recovery system of  claim 17 , wherein the power input location is a load storage device. 
     
     
         23 . The energy recovery system of  claim 22 , wherein the load storage device is a fuel cell. 
     
     
         24 . The energy recovery system of  claim 17 , wherein the power input location is an engine output shaft.