Lubrication management of a pump for a micro combined heat and power system

Abstract

A piston pump with a working fluid region, drive mechanism and a lubricating fluid region. The pump's working fluid region is configured to circulate a working fluid through an external circuit, such as a micro combined heat and power system. The working fluid region is separated from its lubricating fluid region by a seal. By keeping a sufficient quantity of lubricating fluid against the lubricating fluid region side of the seal, leakage of working fluid from the working fluid region to the lubricating fluid region can be significantly reduced. The pump may include various alternative forms of lubricant pumping devices to effect transport and pressurization of the lubricating fluid, including a variable volume pumping cavity, separate oil transfer pump, and mixture between the lubricating fluid and high pressure working fluid. Various piston configurations in the working fluid region may also be used to improve piston sealing.

We claim:  
     
         1 . A piston pump comprising: 
 at least one working fluid region comprising: 
 an intake port configured to receive a working fluid;  
 an outlet port configured to dispense said working fluid, and  
 a piston disposed between said intake and outlet ports such that upon oscillation of said piston, said working fluid is pumped from said intake port to said outlet port;  
   a drive mechanism comprising: 
 a power transfer shaft rotatably responsive to a drive source;  
 a tubular passageway extending from a space adjacent said power transfer shaft to said working fluid region such that said piston is contained in the portion of said tubular passageway in said working fluid region;  
 a crosshead slidably disposed in said tubular passageway, said crosshead pivotally connected to said power transfer shaft; and  
 at least one piston rod connected at a first end to said crosshead and at a second end to said piston, said piston rod configured to impart an oscillating motion to said piston;  
   a lubricating fluid region coupled to at least said drive mechanism, said lubricating fluid region comprising: 
 a lubricant sump disposed adjacent said power transfer shaft and configured to contain at least a portion of said lubricant;  
 a lubricant reservoir in fluid communication with said lubricant sump; and  
 a lubricant pumping device fluidly coupled to said lubricant sump; and  
   at least one seal disposed in said tubular passageway, said seal defining a boundary between said working fluid region and said lubricating fluid region such that said seal is configured to reduce migration of fluid between said working fluid region and said lubricating fluid region.    
     
     
         2 . A piston pump according to  claim 1 , wherein said lubricant sump is hermetically sealed.  
     
     
         3 . A piston pump according to  claim 1 , wherein said lubricant pumping device comprises: 
 a lubricant inlet channel configured to receive lubricant from at least one of said lubricant sump and said lubricant reservoir;    an inlet check valve disposed in said lubricant inlet channel;    a lubricant outlet channel;    an outlet check valve disposed in said lubricant outlet channel; and    a variable volume pumping cavity at least partially disposed in said tubular passageway, said cavity in fluid communication with said lubricant inlet channel and said lubricant outlet channel, said cavity defined at a first end by said crosshead such that upon oscillating motion of said crosshead, said lubricant introduced into said cavity through said lubricant inlet channel becomes pressurized and exits through said lubricant outlet channel.    
     
     
         4 . A piston pump according to  claim 3 , wherein said lubricant inlet channel is fluidly coupled to said lubricant reservoir.  
     
     
         5 . A piston pump according to  claim 3 , wherein said variable volume pumping cavity is defined at a second end by a wall intermediate said crosshead and said at least one working fluid region.  
     
     
         6 . A piston pump according to  claim 5 , wherein said at least one seal is disposed in said wall.  
     
     
         7 . A piston pump according to  claim 1 , further comprising a reservoir seal disposed about said piston rod between said lubricant reservoir and said lubricant pumping device.  
     
     
         8 . A piston pump according to  claim 7 , wherein said at least one seal and said reservoir seal define boundaries between multiple compartments along the lengthwise dimension of said tubular passageway.  
     
     
         9 . A piston pump according to  claim 1 , wherein said at least one working fluid region comprises a plurality of working fluid regions, each configured to cooperate with corresponding said tubular passageways, crossheads, piston rods and seals to define a single unit of a multi-unit piston pump.  
     
     
         10 . A piston pump according to  claim 9 , wherein said plurality of tubular passageways are fluidly connected with one another.  
     
     
         11 . A piston pump according to  claim 1 , wherein said lubricant pumping device comprises a separately-powered oil transfer pump.  
     
     
         12 . A piston pump according to  claim 11 , wherein said lubricant reservoir is fluidly coupled to said piston pump.  
     
     
         13 . A piston pump according to  claim 11 , wherein said lubricant reservoir is separately pressurizable from the remainder of said lubricating fluid region.  
     
     
         14 . A piston pump according to  claim 11 , wherein the pumping capacity of said oil transfer pump is less than five percent of that of said piston pump.  
     
     
         15 . A piston pump according to  claim 11 , wherein said drive source is a motor.  
     
     
         16 . A piston pump according to  claim 15 , further comprising: 
 a first compartment configured to contain said motor therein;    a second compartment configured to hold a lubricant and at least a portion of said lubricating fluid region and said drive mechanism therein;    a coupling extending from said motor to said power transfer shaft in said second compartment;    a vapor space seal disposed about said coupling and defining a boundary between said first and second compartments; and    a lubricant drain line fluidly coupled to said first compartment and said oil transfer pump, said lubricant drain line configured to remove at least one of said working fluid and said lubricant from said first compartment.    
     
     
         17 . A piston pump according to  claim 16 , further comprising a lubricant return line fluidly coupled to said second compartment and said oil transfer pump.  
     
     
         18 . A piston pump according to  claim 17 , wherein said first and second compartments are disposed in a common housing.  
     
     
         19 . A piston pump according to  claim 18 , wherein said common housing is hermetically sealed.  
     
     
         20 . A piston pump according to  claim 16 , wherein said first compartment further comprises a heating element disposed therein, said heating element configured to maintain the temperature in said first compartment above the saturation temperature of said working fluid.  
     
     
         21 . A piston pump according to  claim 16 , wherein said lubricant drain line and the surface of said first compartment that contains said vapor space seal occupy the substantially lowest vertical position in said first compartment such that any lubricant that collects in said first compartment will flow through said lubricant drain line.  
     
     
         22 . A piston pump according to  claim 1 , wherein said lubricant pumping device comprises a high pressure vapor source fluidly coupled to said lubricant sump.  
     
     
         23 . A piston pump according to  claim 22 , wherein said high pressure vapor source further comprises: 
 a lubricant pressurization chamber fluidly coupled to said lubricant sump, said pressurization chamber including at least one check valve; and    a flow regulating device configured to intermittently allow the transport of fluid contained in said lubricant pressurization chamber to at least one of said working fluid region and said lubricating fluid region.    
     
     
         24 . A piston pump according to  claim 23 , wherein said flow regulating device is a time-responsive valve.  
     
     
         25 . A piston pump according to  claim 23 , wherein said high pressure vapor source is a jet pump configured to inject lubricant into a flow of high pressure vapor.  
     
     
         26 . A piston pump comprising: 
 at least one working fluid region comprising: 
 an intake port configured to receive a working fluid;  
 an outlet port configured to dispense said working fluid, and  
 a piston disposed between said intake and outlet ports such that upon oscillation of said piston, said working fluid is pumped from said intake port to said outlet port;  
   a drive mechanism comprising: 
 a power transfer shaft rotatably responsive to a drive source;  
 a tubular passageway extending from a space adjacent said power transfer shaft to said working fluid region such that said piston is contained in the portion of said tubular passageway in said working fluid region;  
 a crosshead slidably disposed in said tubular passageway, said crosshead connected to said power transfer shaft; and  
 at least one piston rod connected at a first end to said crosshead and at a second end to said piston, said piston rod configured to impart an oscillating motion to said piston;  
   a lubricating fluid region coupled to at least said drive mechanism, said lubricating fluid region comprising: 
 a lubricant sump disposed adjacent said power transfer shaft and configured to contain at least a portion of said lubricant;  
 a lubricant reservoir in fluid communication with said lubricant sump; and  
 a lubricant pumping device comprising: 
 a lubricant inlet channel configured to receive lubricant from at least one of said lubricant sump and said lubricant reservoir;  
 an inlet check valve disposed in said lubricant inlet channel;  
 a lubricant outlet channel;  
 an outlet check valve disposed in said lubricant outlet channel; and  
 a variable volume pumping cavity at least partially disposed in said tubular passageway, said cavity in fluid communication with said lubricant inlet channel and said lubricant outlet channel, said cavity defined at a first end by said crosshead such that upon reciprocating motion of said crosshead, said lubricant introduced into said cavity through said lubricant inlet channel becomes pressurized and exits through said lubricant outlet channel; and  
 
   at least one seal disposed in said tubular passageway, said seal defining a boundary between said working fluid region and said lubricating fluid region such that said seal is configured to reduce migration of fluid between said working fluid region and said lubricating fluid region.    
     
     
         27 . A piston pump comprising: 
 at least one working fluid region comprising: 
 a pumping chamber for pressurizing a working fluid;  
 an intake port fluidly coupled to said pumping chamber, said intake port configured to receive said working fluid;  
 an outlet port fluidly coupled to said pumping chamber, said outlet port configured to dispense said working fluid; and  
 a piston disposed in said pumping chamber and defining a sealing channel therebetween, such that upon oscillation of said piston, said working fluid is pumped from said intake port to said outlet port;  
   a drive mechanism comprising: 
 a power transfer shaft rotatably responsive to a drive source;  
 a tubular passageway extending from a space adjacent said drive mechanism to said working fluid region such that said piston is contained in the portion of said tubular passageway in said working fluid region;  
 at least one piston rod pivotally coupled at a first end to said power transfer shaft and at a second end to said piston, said piston rod configured to impart an oscillating motion to said piston; and  
   a lubricating fluid region coupled to at least said drive mechanism, said lubricating fluid region comprising: 
 a lubricant sump disposed adjacent said power transfer shaft and configured to contain at least a portion of said lubricant; and  
 a lubricant pumping device fluidly coupled to said lubricant sump; and  
   a sealing fluid distribution network configured to transport a sealing fluid from said lubricating fluid region to said sealing channel.    
     
     
         28 . A piston pump according to  claim 27 , wherein said sealing fluid distribution network comprises a lubricant flowpath disposed within said piston and piston rod such that fluid communication is established therebetween.  
     
     
         29 . A piston pump according to  claim 28 , wherein said flowpath terminates along a radial surface of said piston such that sealing fluid routed through said sealing fluid distribution network can affect sealing and lubrication in said sealing channel.  
     
     
         30 . A piston pump according to  claim 28 , wherein said piston further comprises at least one circumferential groove, said groove in fluid communication with said lubricant flowpath.  
     
     
         31 . A piston pump according to  claim 30 , wherein an axial passage is disposed between said circumferential groove and said lubricant flowpath such that lubricant can be conveyed from said lubricant flowpath to said circumferential groove.  
     
     
         32 . A piston pump according to  claim 27 , wherein said sealing fluid distribution network comprises said piston, a scraper ring coupled to said piston, and said tubular passageway in said working fluid region, said scraper ring configured to traverse said sealing channel upon said oscillation of said piston within said tubular passageway.  
     
     
         33 . A piston pump according to  claim 32 , wherein said scraper ring is defined by a taper on its outer surface to preferentially allow sealing fluid migration into said pumping chamber while inhibiting working fluid migration out of said pumping chamber.  
     
     
         34 . A piston pump according to  claim 27 , wherein said sealing fluid distribution network is configured such that the pressure of said sealing fluid flowing through said sealing channel is sufficient to ensure that the net flow of fluid between said pumping chamber and said lubricating fluid region during each oscillating piston cycle is toward said pumping chamber.  
     
     
         35 . A piston pump according to  claim 27 , wherein each of said intake and outlet ports include a check valve disposed therein.  
     
     
         36 . A micro combined heat and power system comprising: 
 a working fluid circuit configured to transport a working fluid, said working fluid circuit comprising: 
 an evaporator configured to convert said working fluid from a subcooled liquid into a superheated vapor;  
 an expander in fluid communication with said evaporator, said expander including a first lubricant sump;  
 a condenser in fluid communication with said expander; and  
 a working fluid feed pump comprising: 
 at least one working fluid region comprising: 
 an intake port configured to receive said working fluid;  
 an outlet port configured to dispense said working fluid, and  
 a piston disposed between said intake and outlet ports such that upon oscillation of said piston, said working fluid is pumped from said intake port to said outlet port;  
 
 a drive mechanism comprising: 
 a power transfer shaft rotatably responsive to a drive source;  
 a tubular passageway extending from a space adjacent said power transfer shaft to said working fluid region such that said piston is contained in the portion of said tubular passageway in said working fluid region;  
 a crosshead slidably disposed in said tubular passageway, said crosshead pivotally connected to said power transfer shaft; and  
 at least one piston rod connected at a first end to said crosshead and at a second end to said piston, said piston rod configured to impart an oscillating motion to said piston;  
 
 a lubricating fluid region coupled to at least said drive mechanism, said lubricating fluid region comprising: 
 a second lubricant sump disposed adjacent said power transfer shaft and configured to contain at least a portion of said lubricant;  
 a lubricant reservoir in fluid communication with said second lubricant sump; and  
 a lubricant pumping device fluidly coupled to said second lubricant sump; and  
 
 at least one seal disposed in said tubular passageway, said seal defining a boundary between said working fluid region and said lubricating fluid region; and  
 
   at least one energy conversion circuit operatively responsive to said working fluid circuit such that upon operation of said system, said at least one energy conversion circuit is configured to provide useable energy.    
     
     
         37 . A micro combined heat and power system according to  claim 36 , wherein said lubricant pumping device comprises a high pressure vapor source fluidly coupled to said lubricant sump.  
     
     
         38 . A micro combined heat and power system according to  claim 37 , wherein said expander is said high pressure vapor source.  
     
     
         39 . A micro combined heat and power system according to  claim 38 , further comprising a jet pump disposed in a flowpath fluidly coupled to said expander so that high pressure vapor in said flowpath draws lubricant into a low pressure region within said jet pump for mixing between said vapor and said lubricant such that upon mixing the fluids can be used elsewhere.  
     
     
         40 . A micro combined heat and power system according to  claim 36 , wherein said lubricant pumping device is a separately-powered oil transfer pump fluidly connected between said expander and said second lubricant sump.  
     
     
         41 . A micro combined heat and power system according to  claim 40 , wherein said oil transfer pump is configured to move said lubricant from said second lubricant sump to said expander.  
     
     
         42 . A micro combined heat and power system according to  claim 40 , wherein said oil transfer pump is configured to move said lubricant from said first lubricant sump to said second lubricant sump at least during periods of system operation.  
     
     
         43 . A micro combined heat and power system according to  claim 42 , wherein said oil transfer pump is configured to maintain said second lubrication sump substantially full of lubricant at least during periods of system operation.  
     
     
         44 . A micro combined heat and power system according to  claim 43 , further comprising a pressure relief valve disposed between said first lubricant sump and said second lubricant sump.  
     
     
         45 . A micro combined heat and power system according to  claim 36 , wherein said expander is a scroll expander comprising a working fluid inlet, a working fluid outlet, an orbiting involute spiral wrap, a stationary involute spiral wrap and a working fluid outlet.  
     
     
         46 . A micro combined heat and power system according to  claim 40 , further including a vapor line extending from said second lubricant sump to said condenser.  
     
     
         47 . A micro combined heat and power system according to  claim 36 , wherein said lubricant reservoir is fluidly coupled to said first lubricant sump to receive lubricant that has been separated out of said expander.  
     
     
         48 . A micro combined heat and power system according to  claim 36 , wherein said lubricant pumping device comprises: 
 a lubricant inlet channel configured to receive lubricant from at least one of said first or second lubricant sumps or said lubricant reservoir;    an inlet check valve disposed in said lubricant inlet channel;    a lubricant outlet channel;    an outlet check valve disposed in said lubricant outlet channel; and    a variable volume pumping cavity at least partially disposed in said tubular passageway, said cavity in fluid communication with said lubricant inlet channel and said lubricant outlet channel, said cavity defined at a first end by said crosshead such that upon reciprocating motion of said crosshead, said lubricant introduced into said cavity through said lubricant inlet channel becomes pressurized and exits through said lubricant outlet channel.    
     
     
         49 . A micro combined heat and power system according to  claim 36 , wherein said working fluid feed pump further comprises: 
 a motor configured to provide power to said pump; and    a housing comprising: 
 a first compartment configured to contain said motor;  
 a second compartment configured to contain at least said power transfer shaft and said second lubricant sump;  
 a coupling extending from said motor to said power transfer shaft;  
 a vapor space seal disposed about said coupling and defining a boundary between said first and second compartments; and  
 a lubricant drain line fluidly connected between said first compartment and said first lubricant sump.  
   
     
     
         50 . A micro combined heat and power system according to  claim 49 , further comprising a lubricant return line that extends from said second compartment to said first lubricant sump such that, in conjunction with said oil transfer pump, a continuous loop is formed therebetween.  
     
     
         51 . A micro combined heat and power system according to  claim 50 , wherein said second compartment is situated below said first compartment such that any lubricant present in said first compartment will collect along a lower surface formed in part by said vapor space seal.  
     
     
         52 . A micro combined heat and power system according to  claim 50 , wherein said first lubricant sump is configured such that a lubricant fluid level therein is situated in a lower vertical elevation than a lubricant fluid level in said first and second compartments.  
     
     
         53 . A micro combined heat and power system according to  claim 50 , wherein said lubricant drain line is spaced adjacent said vapor space seal such that at least one of said organic working fluid and said lubricant collecting therealong can flow through said lubricant drain line to said first lubricant sump.  
     
     
         54 . A micro combined heat and power system according to  claim 49 , wherein said first compartment further comprises a heating element disposed therein, said heating element configured to maintain the temperature in said first compartment above the saturation temperature of said working fluid.  
     
     
         55 . A micro combined heat and power system according to  claim 36 , further comprising a sealing fluid distribution network configured to maintain a sealing fluid between said piston and a complementary surface in said working fluid region.  
     
     
         56 . A micro combined heat and power system according to  claim 55 , wherein said sealing fluid distribution network comprises said piston, a scraper ring coupled to said piston, and said tubular passageway in said working fluid region, said scraper ring configured to traverse said sealing channel upon said oscillation of said piston within said tubular passageway.  
     
     
         57 . A piston pump according to  claim 56 , wherein said scraper ring is defined by a taper on its outer surface to preferentially allow sealing fluid migration into said pumping chamber while inhibiting working fluid migration out of said pumping chamber.  
     
     
         58 . A micro combined heat and power system according to  claim 55 , wherein said sealing fluid distribution network comprises a lubricant flowpath disposed within said piston and piston rod such that fluid communication is established therebetween.  
     
     
         59 . A micro combined heat and power system according to  claim 57 , said sealing fluid distribution network is configured such that the pressure of said sealing fluid flowing through said sealing channel is sufficient to ensure that the net flow of fluid between said pumping chamber and said lubricating fluid region during each oscillating piston cycle is toward said pumping chamber.  
     
     
         60 . A method of operating a piston pump, said method comprising: 
 configuring said pump to comprise: 
 at least one working fluid region comprising: 
 an intake port configured to receive a working fluid;  
 an outlet port configured to dispense said working fluid, and  
 a piston disposed between said intake and outlet ports such that upon oscillation of said piston, said working fluid is pumped from said intake port to said outlet port;  
 
 a drive mechanism comprising: 
 a power transfer shaft rotatably responsive to a drive source;  
 a tubular passageway adjacent said power transfer shaft;  
 a crosshead slidably disposed in said tubular passageway, said crosshead pivotally connected to said power transfer shaft; and  
 at least one piston rod connected at a first end to said crosshead and at a second end to said piston, said piston rod configured to impart an oscillating motion to said piston;  
 
 a lubricating fluid region coupled to at least said drive mechanism, said lubricating fluid region comprising: 
 a lubricant sump disposed adjacent said power transfer shaft and configured to contain at least a portion of a lubricating fluid;  
 a lubricant reservoir in fluid communication with said lubricant sump; and  
 a lubricant pumping device fluidly coupled to said lubricant sump; and  
 
 at least one seal disposed in said tubular passageway, said seal defining a boundary between said working fluid region and said lubricating fluid region;  
   connecting said intake port and said outlet port to a supply of said working fluid;    introducing said working fluid to said intake port;    activating said drive source so that said piston moves at least a portion of said working fluid from said intake port to said outlet port; and    maintaining a sufficient quantity of said lubricating fluid in said lubricant reservoir to ensure that the side of said seal that is adjacent said lubricant reservoir is exposed to a substantially vapor-free environment.    
     
     
         61 . A method according to  claim 60 , wherein said lubricant pumping device is a separate oil transfer pump placed in fluid communication with said lubricant sump.  
     
     
         62 . A method according to  claim 60 , comprising the additional step of configuring a sealing fluid distribution network to provide sealing fluid to a sealing channel disposed between said piston and a complementary surface in said working fluid region.  
     
     
         63 . A method according to  claim 62 , wherein said sealing fluid distribution network comprises a flowpath defined in said piston and said piston rod to establish fluid communication between said lubricant sump and said sealing channel such that a sealing fluid may be introduced into said sealing channel through said flowpath.  
     
     
         64 . A method according to  claim 62 , wherein said sealing fluid distribution network comprises said piston, a scraper ring coupled to said piston, and said complementary surface in said working fluid region, said scraper ring configured to traverse said sealing channel upon said oscillation of said piston within said complementary surface in said working fluid region.  
     
     
         65 . A method according to  claim 61 , wherein said step of configuring said pump further comprises: 
 providing a motor configured to provide power to said pump;    providing a first compartment to contain said motor;    providing a second compartment configured to contain at least said power transfer shaft and said second lubricant sump;    extending a coupling from said motor to said power transfer shaft;    establishing a vapor space seal disposed about said coupling such that a boundary is formed between said first and second compartments.    
     
     
         66 . A method according to  claim 65 , wherein said step of configuring said pump further comprises: 
 connecting a lubricant drain line adjacent said vapor space seal such that lubricant collecting therealong can flow through said lubricant drain line and out of said first compartment; and    connecting a lubricant return line to said second compartment such that excess of said lubricant collecting therein can flow through said lubricant return line and out of said second compartment.    
     
     
         67 . A method according to  claim 66 , wherein said step of configuring said pump further comprises activating a heating element disposed in said first compartment so that the temperature in said first compartment is maintained above the saturation temperature of said working fluid.  
     
     
         68 . A method according to  claim 67 , comprising the additional step of operating said oil transfer pump such that at least a portion of said lubricant flowing in at least one of said lubricant drain line or said lubricant return line is moved to said lubricant sump.  
     
     
         69 . A method according to  claim 68 , wherein said step of operating said oil transfer pump substantially fills said lubricant sump.  
     
     
         70 . A method of operating a piston pump, said method comprising: 
 configuring said pump to comprise: 
 at least one working fluid region comprising: 
 an intake port configured to receive a working fluid;  
 an outlet port configured to dispense said working fluid, and  
 a piston disposed between said intake and outlet ports such that upon oscillation of said piston, said working fluid is pumped from said intake port to said outlet port;  
 
 a drive mechanism comprising: 
 a power transfer shaft rotatably responsive to a drive source;  
 a tubular passageway adjacent said power transfer shaft;  
 a crosshead slidably disposed in said tubular passageway, said crosshead pivotally connected to said power transfer shaft; and  
 at least one piston rod connected at a first end to said crosshead and at a second end to said piston, said piston rod configured to impart an oscillating motion to said piston;  
 
 a lubricating fluid region coupled to at least said drive mechanism, said lubricating fluid region comprising: 
 a lubricant sump disposed adjacent said power transfer shaft and configured to contain at least a portion of a lubricating fluid;  
 a lubricant reservoir in fluid communication with said lubricant sump; and  
 a lubricant pumping device fluidly coupled to said lubricant sump; and  
 
 at least one seal disposed in said tubular passageway, said seal defining a boundary between said working fluid region and said lubricating fluid region;  
   connecting said intake port and said outlet port to a supply of said working fluid;    introducing said working fluid to said intake port;    activating said drive source so that said piston moves at least a portion of said working fluid from said intake port to said outlet port; and    increasing the pressure of said lubricating fluid at said boundary above that of the lubricating fluid remaining in said sump.    
     
     
         71 . A method according to  claim 70 , wherein said increased lubricant pressure at said boundary is effected by configuring said lubricant pumping device to comprise: 
 a lubricant inlet channel configured to receive lubricant from at least one of said lubricant sump and said lubricant reservoir;    an inlet check valve disposed in said lubricant inlet channel;    a lubricant outlet channel;    an outlet check valve disposed in said lubricant outlet channel; and    a variable volume pumping cavity at least partially disposed in said tubular passageway, said cavity in fluid communication with said lubricant inlet channel and said lubricant outlet channel, said cavity defined at a first end by said crosshead such that upon oscillating motion of said crosshead, said lubricant introduced into said cavity through said lubricant inlet channel becomes pressurized and exits through said lubricant outlet channel.    
     
     
         72 . A method according to  claim 70 , wherein said increased lubricant pressure at said boundary is effected by the additional steps of: 
 configuring said lubricant pumping device as a separate oil transfer pump; and    operating said separate oil transfer pump to pressurize said lubricant reservoir more than the remainder of said lubricating fluid region.    
     
     
         73 . A method of operating a micro combined heat and power system, said method comprising: 
 configuring a working fluid circuit to transport a working fluid, said working fluid circuit comprising: 
 an evaporator configured to convert said working fluid from a subcooled liquid into a superheated vapor;  
 an expander in fluid communication with said evaporator, said expander including a first lubricant sump; and  
 a condenser in fluid communication with said expander; and  
 a working fluid feed pump comprising: 
 at least one working fluid region with an intake port configured to receive a working fluid, an outlet port configured to dispense said working fluid, and a piston disposed between said intake and outlet ports such that upon oscillation of said piston, said working fluid is pumped from said intake port to said outlet port;  
 a drive mechanism with a power transfer shaft rotatably responsive to a drive source, a tubular passageway adjacent said power transfer shaft, a crosshead slidably disposed in said tubular passageway, said crosshead connected to said power transfer shaft, and at least one piston rod connected at a first end to said crosshead and at a second end to said piston, said piston rod configured to impart an oscillating motion to said piston;  
 a lubricating fluid region with a second lubricant sump disposed adjacent said power transfer shaft and configured to contain at least a portion of a lubricating fluid, and a lubricant pumping device fluidly coupled to said second lubricant sump; and  
 at least one seal disposed in said tubular passageway, said seal defining a boundary between said working fluid region and said lubricating fluid region;  
 
   fluidly connecting said intake port to said condenser;    fluidly connecting said outlet port to said evaporator;    starting said system such that said working fluid adjacent said evaporator is converted into superheated vapor, expanded in said expander, cooled in said condenser, and pumped by said pump back to said evaporator in a continuous loop; and    maintaining a sufficient quantity of said lubricating fluid in said lubricant reservoir to ensure that the side of said seal that is adjacent said lubricant reservoir is exposed to a substantially vapor-free environment.    
     
     
         74 . A method according to  claim 73 , comprising the additional step of configuring said lubricant pumping device to comprise: 
 a lubricant inlet channel to receive lubricant from at least one of said first or second lubricant sumps or said lubricant reservoir;    an inlet check valve disposed in said lubricant inlet channel;    a lubricant outlet channel;    an outlet check valve disposed in said lubricant outlet channel; and    a variable volume pumping cavity at least partially disposed in said tubular passageway, said cavity in fluid communication with said lubricant inlet channel and said lubricant outlet channel, said cavity defined at a first end by said crosshead such that upon reciprocating motion of said crosshead, said lubricant introduced into said cavity through said lubricant inlet channel becomes pressurized and exits through said lubricant outlet channel.    
     
     
         75 . A method according to  claim 73 , wherein said step of configuring said working fluid circuit further comprises incorporating a separate oil transfer pump as said lubricant pumping device.  
     
     
         76 . A method according to  claim 73 , comprising the additional step of introducing said lubricating fluid into a sealing channel disposed between said piston and said generally cylindrical passageway.  
     
     
         77 . A method according to  claim 76 , wherein said step of introducing said lubricating fluid comprises the additional step of configuring a sealing fluid distribution network to transport a sealing fluid from said lubricating fluid region to said sealing channel.  
     
     
         78 . A method according to  claim 77 , wherein said sealing fluid distribution network comprises a lubricant flowpath disposed within said piston and piston rod such that fluid communication is established therebetween.  
     
     
         79 . A method according to  claim 73 , wherein said step of configuring said pump further comprises: 
 providing a motor configured to provide power to said pump;    providing a first compartment to contain said motor;    providing a second compartment configured to contain at least said power transfer shaft and said second lubricant sump;    extending a coupling from said motor to said second compartment;    establishing a vapor space seal disposed about said coupling; and    defining a boundary between said first and second compartments such that said lubricant is substantially contained in said second compartment.    
     
     
         80 . A method according to  claim 79 , wherein said step of configuring said pump further comprises: 
 fluidly coupling a lubricant drain line between said first compartment and said first lubricant sump, said lubricant drain line spaced adjacent said vapor space seal such that lubricant collecting therealong can flow through said lubricant drain line to said first lubricant sump; and    fluidly coupling a lubricant return line between said second compartment and said first lubricant sump.    
     
     
         81 . A method according to  claim 80 , comprising the additional step of heating said first compartment with a heating element such that the temperature in said first compartment is maintained above the saturation temperature of said fluid to be pumped.  
     
     
         82 . A method according to  claim 75 , wherein said step of operating said oil transfer pump occurs independent of operation of said micro combined heat and power system.  
     
     
         83 . A method according to  claim 73 , comprising the additional step of pressurizing said lubricating fluid with high pressure vapor that has exited said evaporator.  
     
     
         84 . A method according to  claim 83 , wherein said step of pressurizing said lubricating fluid is accomplished a device that comprises: 
 a lubricant pressurization chamber fluidly coupled to said lubricant sump, said pressurization chamber including at least one check valve; and    a flow regulating device configured to intermittently allow the transport of fluid contained in said lubricant pressurization chamber to at least one of said working fluid region and said lubricating fluid region.    
     
     
         85 . A method according to  claim 84 , wherein said flow regulating device is a time-responsive valve.  
     
     
         86 . A method according to  claim 84 , wherein said step of pressurizing said lubricating fluid is accomplished with a jet pump configured to inject said lubricating fluid into a flow of said high pressure vapor.