Volumetric fluid expander with water injection

Abstract

An exhaust gas energy recovery system includes an internal combustion engine, a volumetric fluid expander, and a water injection mechanism. The internal combustion engine includes an air inlet, at least one cylinder, and an exhaust gas outlet for conveying an exhaust gas stream at a first pressure. The volumetric fluid expander generates useful work at an output shaft by expanding the exhaust gas stream to a second pressure lower than the first pressure as the exhaust gas stream moves through the volumetric fluid expander. The water injection mechanism injects water into the system at a location between the air inlet of the engine and the expander to increase the volume of the exhaust received by the expander for increased power output at the expander.

What is claimed is: 
     
         1 . An exhaust gas energy recovery system for an internal combustion engine having an air intake and an exhaust outlet, the energy recovery system comprising:
 (a) a volumetric fluid expander in fluid communication with the exhaust manifold, the volumetric fluid expander being configured to receive and expand exhaust from the exhaust manifold to a lower pressure, the volumetric fluid expander including first and second twisted meshed rotors rotatably disposed in a housing, wherein the rotors have an equal number of lobes, and wherein the lobes of the first rotor do not contact the lobes of the second rotor; and   (b) a water injection mechanism including a water injector and a pump for providing pressurized water to the water injector, the water injector being positioned to inject water at a location between the air intake and the volumetric fluid expander to cause a volumetric expansion.   
     
     
         2 . The exhaust gas energy recovery system of  claim 1 , further comprising:
 (a) a water recovery condenser located downstream of the volumetric fluid expander and in fluid communication with the pump, the water recovery condenser being for collecting at least some of the water injected by the water injector.   
     
     
         3 . The exhaust gas energy recovery system of  claim 2 , wherein the water recovery condenser is located downstream of a catalytic converter associated with the internal combustion engine. 
     
     
         4 . The exhaust gas energy recovery system of  claim 1 , wherein the water injector is positioned to inject water at a location upstream of a supercharger associated with the internal combustion engine. 
     
     
         5 . The exhaust gas energy recovery system of  claim 1 , wherein the water injector is positioned to inject water into a cylinder of the internal combustion engine. 
     
     
         5 . The exhaust gas energy recovery system of  claim 1 , wherein the water injector is positioned to inject water at a location between a cylinder of the internal combustion engine and the volumetric fluid expander. 
     
     
         6 . The exhaust gas energy recovery system of  claim 1 , further comprising:
 (a) a controller to operate the pump, wherein the controller is configured to control the speed of the pump based on an operating parameter of at least one of the internal combustion engine and the volumetric fluid expander.   
     
     
         7 . The exhaust gas energy recovery system of  claim 6 , wherein the operating parameter is one or more of an exhaust temperature, an exhaust pressure, and a rotational speed of the expander. 
     
     
         8 . A method for recovering exhaust gas energy, the method comprising:
 injecting, by a water injection mechanism, water into a cylinder of an engine at or before an exhaust cycle of the cylinder, wherein the injected water vaporizes within the cylinder;   collecting, via an exhaust manifold of the engine, exhaust gas stream mixed with the vaporized water;   supplying the exhaust gas stream into a volumetric fluid expander, the exhaust gas stream having a first pressure; and   generating, by the volumetric fluid expander, useful work at an output shaft of the expander by expanding the exhaust gas stream to a second pressure lower than the first pressure.   
     
     
         9 . The method of  claim 8 , wherein the step of injecting, by the water injection mechanism, water into the cylinder comprises providing:
 a water injector configured to inject water into the cylinder;   a water pump device connected to the water injector;   a water tank connected to the water pump device; and   a controller configured to control the water injector to selectively inject water to the cylinder at or before the exhaust cycle of the cylinder.   
     
     
         10 . The method of  claim 9 , wherein the step of providing the controller configured to control the water injector comprises activating the water injector and the water pump device to selectively inject water to the cylinder based on an operating parameter of the engine. Activating    
     
     
         11 . The method of  claim 8 , wherein the step of generating, by the volumetric fluid expander, useful work comprises providing:
 first and second twisted meshed rotors rotatably disposed in a housing of the volumetric fluid expander, wherein the rotors have an equal number of lobes, and wherein the lobes of the first rotor do not contact the lobes of the second rotor.   
     
     
         12 . The method of  claim 8 , wherein the step of generating, by the volumetric fluid expander, useful work comprises transferring the generated useful work to an output shaft of the engine. 
     
     
         13 . The method of  claim 8 , wherein the step of generating, by the volumetric fluid expander, useful work comprises transferring the generated useful work to a generator or a hydraulic pump. 
     
     
         14 . An exhaust gas energy recovery system comprising:
 a. an internal combustion engine having a cylinder and an exhaust gas outlet for conveying an exhaust gas stream at a first pressure;   b. a volumetric fluid expander including:
 i. a housing having an inlet and an outlet, the housing inlet being in fluid communication with the exhaust gas outlet; 
 ii. an output shaft; 
 iii. wherein the volumetric fluid expander is configured to generate useful work at the output shaft by expanding the exhaust gas stream to a second pressure lower than the first pressure generally without reducing the volume of the exhaust stream as the exhaust stream moves from the housing inlet to the outlet; and 
   c. a water injection mechanism configured to inject water into the cylinder such that the exhaust gas stream received by the volumetric fluid expander is increased in volume.   
     
     
         15 . The system of  claim 14 , wherein the water injection mechanism is configured to inject water into the cylinder at or before the exhaust cycle of the cylinder begins. 
     
     
         16 . The system of  claim 14 , wherein the water injection mechanism comprises:
 a plurality of water injectors, each configured to inject water into each of the plurality of cylinders;   a water pump device connected to the plurality of water injectors;   a water tank connected to the water pump device; and   a controller configured to control the water injector to selectively inject water to the cylinder at or before the exhaust cycle of the cylinder.   
     
     
         17 . The system of  claim 16 , wherein the controller controls the water injector to selectively inject water to the cylinder based on an operating parameter of the engine. 
     
     
         18 . The system of  claim 14 , wherein the volumetric fluid expander includes first and second twisted meshed rotors rotatably disposed in the housing, wherein the rotors have an equal number of lobes, and wherein the lobes of the first rotor do not contact the lobes of the second rotor. 
     
     
         19 . The system of  claim 14 , wherein the volumetric fluid expander output shaft is mechanically coupled to an output shaft of the combustion engine. 
     
     
         20 . The system of  claim 14 , wherein the volumetric fluid expander output shaft is mechanically coupled to a generator.