Compression/expansion process that allows temperature to vary independent of pressure

Abstract

Systems and methods are described herein to operate an air compression and/or expansion system in its most efficient regime, at a desired efficiency, and/or achieve a desired pressure ratio independent of discharge temperature, with little to no impact on thermal efficiency. For example, systems and methods are provided for controlling and operating hydraulic pumps/motors used within a hydraulically actuated device/system, such as, for example, a gas compression and/or expansion energy system, in its most efficient regime, continuously, substantially continuously, intermittently, or varied throughout an operating cycle or stroke of the system to achieve any desired pressure and temperature profile. Such systems and methods can achieve any desired pressure ratio independent of input or discharge temperature, and can also achieve any desired discharge temperature independent of pressure ratio, without altering any of the structural components of the device or system.

1 . An apparatus, comprising:
 a hydraulic pump operable to deliver hydraulic fluid over at least a hydraulic pressure range that includes a predetermined lower pressure and a predetermined upper pressure, greater than said lower pressure;   a hydraulic actuator arrangement including a first hydraulic piston and a second hydraulic piston, each of said hydraulic pistons having a first side and a second side; and   a working actuator operably coupled to said hydraulic actuator arrangement, said working actuator having a working cylinder and a working piston disposed for reciprocating movement in the working cylinder, the working piston defining at least in part between a first side thereof and the working cylinder a working chamber configured to contain a quantity of gas,   said hydraulic actuator arrangement being operably coupled to said hydraulic pump to enable selective delivery of pressurized hydraulic fluid from said hydraulic pump to one or both of said first side and said second side of each of said first and second hydraulic pistons to yield an output force in a first force range corresponding to a first combination, and to yield an output force in a second force range, different than said first force range, corresponding to a second combination;   a hydraulic controller operable to cause the hydraulic actuator arrangement to move the working piston: a) at a first average speed over a first distance, and b) at a second average speed over a second distance different than the first average speed,   wherein the hydraulic controller is operable to compress the quantity of gas contained therein at an approximately constant rate as the working piston is moved over the first distance at the first stroke speed and the second distance at the second stroke speed.   
     
     
         2 . The apparatus of  claim 1 , further comprising:
 a heat transfer element disposed within the working chamber, the heat transfer element configured to receive heat energy from the gas being compressed to reduce the temperature of the compressed gas.   
     
     
         3 . The apparatus of  claim 2 , wherein the heat transfer element is configured to transfer heat energy received from the compressed gas to the exterior of the working chamber. 
     
     
         4 . The apparatus of  claim 2 , wherein the heat transfer element is configured to transfer heat energy received from the compressed gas to a volume of liquid contained in the working chamber. 
     
     
         5 . The apparatus of  claim 4 , wherein the volume of liquid is not in contact with the heat transfer element during movement of the working piston over the first distance. 
     
     
         6 . The apparatus of  claim 5 , wherein at least a portion of the volume of liquid is in contact with at least a portion of the heat transfer element during movement of the working piston over the second distance. 
     
     
         7 . The apparatus of  claim 1 , wherein the first stroke speed corresponds to the first force range and the second stroke speed corresponds to the second force range. 
     
     
         8 . An apparatus, comprising:
 a hydraulic pump operable to deliver hydraulic fluid over at least a hydraulic pressure range that includes a predetermined lower pressure and a predetermined upper pressure, greater than said lower pressure;   a hydraulic actuator arrangement including a first hydraulic piston and a second hydraulic piston, each of said hydraulic pistons having a first side and a second side; and   a working actuator operably coupled to said hydraulic actuator arrangement, said working actuator having a working cylinder and a working piston disposed for reciprocating movement in the working cylinder, the working piston defining at least in part between a first side thereof and the working cylinder a working chamber configured to contain a quantity of gas,   said hydraulic actuator arrangement being operably coupled to said hydraulic pump to enable selective delivery of pressurized hydraulic fluid from said hydraulic pump to one or both of said first side and said second side of each of said first and second hydraulic pistons to yield an output force in a first force range corresponding to a first combination, and to yield an output force in a second force range, different than said first force range, corresponding to a second combination;   a hydraulic controller operable to cause the hydraulic actuator arrangement to move the working piston: a) at a first average speed over a first distance, and b) at a second average speed over a second distance different than the first average speed,   wherein the hydraulic controller is operable to compress the quantity of gas contained therein such that heat energy produced by compression of the quantity of gas is transferred from the quantity of gas to the exterior of the working chamber at a substantially constant rate as the working piston is moved over the first distance at the first stroke speed and the second distance at the second stroke speed.   
     
     
         9 . The apparatus of  claim 8 , further comprising:
 a heat transfer element disposed within the working chamber, the heat transfer element configured to receive heat energy from the gas being compressed to reduce the temperature of the compressed gas.   
     
     
         10 . The apparatus of  claim 9 , wherein the heat transfer element is configured to transfer heat energy received from the compressed gas to the exterior of the working chamber. 
     
     
         11 . The apparatus of  claim 9 , wherein the heat transfer element is configured to transfer heat energy received from the compressed gas to a volume of liquid contained in the working chamber. 
     
     
         12 . The apparatus of  claim 8 , wherein the heat energy produced by compression of the quantity of gas is transferred from the quantity of gas to the exterior of the working chamber to maintain a substantially constant temperature during compression of the quantity of gas. 
     
     
         13 . A method of compressing gas in a pressure vessel, the pressure vessel having a working piston disposed therein for reciprocating movement in the pressure vessel, the working piston defining at least in part between a first side thereof and the pressure vessel a working chamber configured to contain at least one of a liquid or a gas, the method comprising:
 moving the working piston at a predetermined velocity profile to compress a quantity of gas contained therein so that the time rate of change of pressure is approximately constant over substantially the entire stroke.   
     
     
         14 . The method of  claim 13 , wherein the working chamber includes a heat transfer element disposed therein, and wherein the predetermined velocity profile is determined by taking into account the portion of the cross-sectional area occupied by the heat transfer element. 
     
     
         15 . The method of  claim 13 , further comprising:
 moving a volume of liquid into the working chamber during at least a portion of a compression stroke,   wherein the predetermined velocity profile is determined by taking into account the volume of liquid being received in the working chamber.   
     
     
         16 . The method of  claim 13 , wherein the working chamber includes a heat transfer element disposed therein, the method further comprising:
 moving a volume of liquid into the working chamber during at least a portion of a compression stroke,   wherein the predetermined velocity profile is determined by taking into account the portion of the cross-sectional area occupied by the heat transfer element and the volume of liquid being received in the working chamber.   
     
     
         17 . The method of  claim 13 , further comprising:
 causing heat energy produced by the compression of the quantity of gas to be transferred from the quantity of gas to the exterior of the working chamber so that a predetermined temperature profile during compression of the quantity of gas is maintained.   
     
     
         18 . The method of  claim 17 , wherein the rate of temperature change is approximately constant over substantially the entire stroke. 
     
     
         19 . The method of  claim 13 , wherein the working chamber includes a heat transfer element disposed therein, the method further comprising:
 causing the temperature of the quantity of gas to increase to a temperature above a temperature of the heat transfer element, and   causing heat energy produced by the compression of the quantity of gas to be transferred from the quantity of gas to the heat transfer element.   
     
     
         20 . The method of  claim 19 , wherein the predetermined velocity profile is determined by taking into account a rate at which heat energy produced by compression of the quantity of gas is transferred from the quantity of gas to the heat transfer element so that a predetermined temperature profile of the gas is maintained.