Abstract:
An axial flow turbine configured to accept different nozzles which are respectively compatible with different fluids (gas, liquid or mixture thereof). The turbine is compatible with different rotating loads, which can be cooled or lubricated using liquid derived from the fluid.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to fluid driven turbines, and more particularly to what are described herein as variable phase fluid driven turbines. 
   Turbines are widely used in industry to convert the energy in liquid streams or gas streams to shaft power. Less common, but also used are turbines to convert the energy in two-phase (gas and liquid) streams to shaft power. The turbines for each type of stream are unique to that stream. That is, a turbine designed to be gas driven is not readily usable for liquid or two-phase flow. For example attempts to use radial inflow gas turbines for two-phase flow have resulted in poor performance and damage because the direction of centrifugal body forces is such as to throw liquid backwards into the nozzle blades. 
   Certain application for turbines require the use of different types of fluid streams for differing conditions. For example, a low temperature geothermal power system may require use of a gas stream or a two-phase flow stream, depending upon the temperature and working fluid used in the power producing cycle. To provide an efficient power conversion system, a new or specialized turbine must be designed, manufactured and qualified for each application. This is costly and time consuming and reduces flexibility, if the thermal characteristics of a given application change with time. There is need for an efficient turbine that can be driven by gas, or liquid or two-phase fluid flow. 
   SUMMARY OF THE INVENTION 
   It is a major object of the invention to provide a solution to the above described problems, and need. 
   An object of the present invention is to provide a turbine that can be used for either gas, liquid or two-phase flow, with minor adjustments to a component part, and known herein as the Variable Phase Turbine. As will be seen, such minor adjustments, typically concern nozzle insert and blade adjustments. 
   A further object is provision of a turbine and electric generator assembly that can be used for either gas, liquid or two-phase flow, and that requires no external seals, known herein as the Variable Phase Turbine Generator Assembly. 
   An additional object is provision of a turbine, electric generator and pump assembly that can be used for either gas, liquid or two-phase flow with no external seals, known as the Variable Phase Turbine Generator Assembly (VPTRA). 
   Yet another objective is provision of a power system, incorporating the Variable Phase Turbine Generator Assembly which generates power from heat sources. 
   A further objective is provision of a power system incorporating the Variable Phase Turbine Generator Assembly to generate power from a stream of gas, liquid or two-phase flow which has received heat from a heat source in a predominately liquid heat exchanger. 
   Another object is provision of a power system incorporating the Variable Phase Turbine Generator Assembly to generate power from a stream of gas, liquid or two-phase flow which has received heat from a geothermal fluid in a predominately liquid heat exchanger. 
   Yet another object is provision of rotary machinery comprising 
   a) an axial flow turbine having nozzle means to receive first fluid flow along a first path to drive turbine blades for rotating a shaft, said path having a first exit, 
   b) a driven structure rotatable by said shaft and having bearings, 
   c) pump means associated with the driven structure to effect second fluid flow along a second path having a second exit, for lubricating the bearings, the second path disjunct from the first path, 
   d) said nozzle means including at least two selectable nozzle configurations, for respectively receiving said first flow in the form of at least two of the following:
         i) gas   ii) liquid   iii) a gas and liquid mixture,       

   e) a selected one of such nozzle configurations installed at the turbine. 
   As will be seen, the nozzle configurations are selected from the following groups:
         x 1 ) a first nozzle having a relatively long flow contour section diverging lengthwise away from a throat, and a perforated fluid distribution plate upstream of the throat,   x 2 ) a relatively short flow contour section lengthwise away from a throat, and an inlet section of relatively large area,   x 3 ) a relatively short flow contour convergent lengthwise away from a throat.
 
Also, the driven structure typically comprises one of the following:
   x 1 ) an electrical generator adjacent said second path, for cooling,   x 2 ) other power means.       

   A further object is to provide the electrical generator adjacent to, or proximate to, the turbine, with a seal for sealing off between the first and second flow paths. The generator and turbine typically share the same shaft. 
   An added object is to utilize geo-thermal fluid that is cooled by the first fluid in a heat exchanger, before supply to the first path. 
   A yet further object is to provide a condenser receiving the first fluid in vapor state, for condensing the first fluid to liquid state, said first fluid then flowing to the second path in the form of the second fluid. 

   
     These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which: 
     DRAWING DESCRIPTION 
       FIG. 1  shows a preferred turbo-generator; 
       FIGS. 2–5  shows nozzle configurations; 
       FIG. 6  shows turbine structure to selectively receive different nozzle; and 
       FIG. 7  shows a power system incorporating the invention. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , gas, liquid or a mixture of the two (collectively and individually hereafter referred to as “fluid”) is introduced at  120  to the VPTRA through an inlet  1 . The fluid is collected in a manifold  2 , and flows to a multiplicity of nozzle inserts  3 , which are easily replaceable. The nozzle inserts are arranged in a holder  22 , to direct the fluid in a generally tangential direction towards rotor blades  5 . The rotor  6  is carried by a rotatably driven shaft  12 . 
   The fluid is expanded from the inlet pressure to a lower pressure in the nozzle inserts, producing a jet having kinetic energy. The jet is impinged upon impulse blades  5 , which act to reverse the direction of flow, producing force on the blades. The blades are attached to rotor  6 , and are easily replaceable. The blades transmit the force to the rotor producing a torque on the shaft  12  causing rotation. 
   The rotation drives an electric rotor piece  13  which is attached to the shaft, producing generated electric current in the electric stator  14 . The current produced is conducted by wires  15  through a sealed and insulated connection to a junction box  16 , for external delivery. 
   The fluid leaves the blades to flow at  7  in a generally axial direction with respect to duct  7   a , typically with some swirl remaining. A continuous, generally annular shroud  8  is attached to outer extents of the blades to collect any centrifuged liquid, as for example where the fluid consists of liquid, or a liquid and gas mixture, and to minimize blade to blade leakage losses and windage losses. 
   Liquid collected on the shroud leaves the shroud with a small swirl that causes it to flow to and collect on the wall  9  of the end plate, ensuring that it leaves the area of the rotating blades without impinging on the blades or shroud which would produce frictional losses. Any liquid on the wall and gas leave the VPTRA through outlet  10 , of duct  7   a.    
   Fluid  21  in liquid state is introduced to the VPTRA through another inlet  21   a . The pressure is increased by a pump  20  attached to the shaft  12 . An impeller  20  on shaft  12  increases the pressure of fluid  21  above that at the inlet, causing the fluid to flow to zone  18 , and lubricate the bearings  17 . The fluid leaving the pump also flows to zone  19  adjacent outer extent of the stator, and cools the electric stator  14 , and rotor  13 . 
   After cooling the electric parts and lubricating the bearing parts, the fluid flows through a passage  23 , and leaves the structure at  24  through an outlet  24   a  after reception in plenum zone  122 , and end zone  122   a , to cool structure and lubricate the bearing  17  closest to rotor  6 . An internal seal  11  on shaft  12  isolates the cooling liquid  21  from the fluid  120  flowing in the rotor area, i.e. the flow paths of the two fluids are disjunct. The casing  25  encloses the parts of the VPTRA and has only static seals at  26  and  27  to contain the fluid. No external rotating seals are required, greatly increasing reliability and useful operating life. 
   As shown in  FIGS. 2–4  the replaceable nozzles consist of three general types. A nozzle insert for a mixture of liquid and gas  28  in  FIG. 2 , has a generally long contour  29  to enable the expanding gas to efficiently transfer energy to the liquid droplets. A gradual pressure gradient and expansion rate is required to avoid excessive slip between the gas and liquid. A distribution plate  30  having a multitude of smaller holes is provided to enable uniform distribution of the liquid and gas at the inlet to the nozzle. The distribution plate and nozzle insert can be fixed or removably held in place by an easily removable snap ring  31 , holding the nozzle in bore  31   a  of structure  31   aa.    
   A nozzle insert  32  in  FIG. 3  for gas fluid has a generally shorter contour  32   a  to provide expansion of the gas in a shorter distance to reduce the wall friction. As shown it may have a convergent-divergent passage  34  with a throat  34   a  to provide supersonic flow velocity at the exit. An inlet section  32   b  having a larger flow area  32   bb  is provided to transport the gas to the inlet of the nozzle contour with low losses. 
   A nozzle insert  33  in  FIG. 4  for a liquid fluid also has a generally shorter contour  33   a , to reduce the wall friction. A convergent exit passage  35  with a generally smaller and decreasing diameter is provided to accelerate the liquid fluid to a high velocity. 
   In all cases, solid inserts can be provided to block individual passages of clustered nozzles when low flow rates of the fluid are to be used. See for example  FIG. 5 , with solid insert  40  received in bore  31   a.    
     FIG. 6  shows a cluster of bores  31   a  in turbine structure  31   aa  to removably and selectively receive selected nozzles, having different fluid flow configurations. 
   A power system incorporating VPTRA is shown in  FIG. 7 . This power system uses a geothermal heat source. Other heat sources may be used to supply heat energy for the identical power system described. Hot geothermal fluid  34  flows into a heat exchanger  35 . Heat is transferred from the geothermal fluid to the working fluid, in this case a liquid refrigerant R134a, which enters the heat exchanger at  37 . After transferring heat the cooler geothermal fluid leaves the heat exchanger at  36 . 
   The heated working fluid flows at  38  into the VPTRA  43 , corresponding to point  1  of  FIG. 1 . After producing power in the VPTRA, the fluid leaves in the vapor state at  39 . It enters a condenser  41 , where it is condensed to liquid, cooled by cooling water  44 , or cooling air. 
   The condensed fluid leaves the condenser at  40 , and has its pressure increased by a boost pump  46 . The fluid flows at  42  back into the VPTRA, corresponding to point  21  of  FIG. 1 . The pressure of the fluid is increased further by the VPTRA pump  20  of  FIG. 1 . The fluid cools the generator and lubricates the bearings in the VPTRA, before leaving and flowing at  37 , to the heat exchanger  35 , closing the circuit of the fluid. Power generated by the fluid is transferred at  48  from the VPTRA to an electrical load  49 . 
   For the system shown, the heat exchanger can be a liquid to liquid heat exchanger, reducing the size, cost and pinch point limitations of a vaporizer, which is used in conventional binary geothermal systems. For a brine temperature of 260° F., refrigerant R134A can be used, which enters the heat exchanger as a liquid and leaves as a supercritical fluid. Expansion in a vapor nozzle insert  32 , of  FIG. 2 , results in an efficient expansion producing a high velocity vapor stream to drive the turbine rotor of the VPTRA. 
   At a higher brine temperature of 300° F., refrigerant R245fa can be used. This results in the fluid entering and leaving the heat exchanger in a liquid state. The liquid is flashed in a two-phase nozzle insert  28  of  FIG. 2 , resulting in a high efficiency expansion producing a high velocity two-phase stream to drive the turbine rotor of the VPTRA. 
   Thus, the unexpected result of the invention is that a single seal-less turbine-generator-pump assembly can be used for a wide range of geothermal or other heat source temperatures to generate power with an efficient replacement of the nozzle inserts and blades. This results in a great savings in engineering and design costs and enables the advantages of a liquid-liquid-heat exchanger to be realized for a wide range of temperatures.