Abstract:
An electrical generator ( 10 ) powered by fluid pressure in a flow line includes a turbine housing ( 23 ) and control valve ( 11 ). The turbine housing houses a rotor ( 29 ) and a plurality of turbine blades ( 33 ) which are rotated by fluid passing from the flow line through the turbine housing. A bearing ( 22 ) within the turbine housing guides rotation of the rotor, and supports a plurality of magnets ( 28 ). Cap member ( 23 ) is sealed to the turbine housing, and a stator ( 40 ) external of the cap member generates electricity in response to a plurality of rotating magnets.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to an integrated turbine generator, such as used in a generator and battery charge control system, using the pressure differential typically found in natural gas production and transmission systems. 
     BACKGROUND OF THE INVENTION 
     The natural gas production and transmission industry routinely wastes significant amounts of energy that could be put to economical and environmentally friendly use for the production of electrical energy. The need for electric power at the well site, compressor stations, downstream city gate and neighborhood distribution stations is well known. Flow measurement, equipment status, valve actuation, emission control and communication systems all require different but typically small amounts of electrical energy to operate. Even when grid electric power is available, commercial electrical power may not be desirable to use due to setup and permitting costs. In these and remote situations where grid power is not available, solar panels or thermoelectric generators are typically used. 
     When gas comes to the surface from a well, it is often at a pressure significantly higher than pressure which may be safely placed in a transmission line. Accordingly, the gas pressure typically is regulated or choked down to the transmission line pressure limit. This pressure reduction releases large amounts of energy, typically as a cooling effect, which is wasted and in many cases has to be reversed by burning gas to reheat the cooled gas before it can continue down the pipeline. When high pressure transmission gas arrives at what is referred to as a “city gate,” the pressure must again be reduced significantly before it can enter pipelines that go into the neighborhoods. Again, the “pressure” energy in the gas is typically wasted even though electric power is needed for instrumentation and communication systems at the site. At remote locations, solar power or thermoelectric systems are often used to keep batteries charged to operate the equipment. 
     Solar energy is essentially free power, but its production is unreliable in many parts of the world due to uncontrollable weather conditions. This unpredictability results in the solar systems being greatly oversized in both panels and battery banks to provide the required safety factor. Also, solar systems by their nature allow batteries to be deep drawn which reduce the battery life. 
     Thermoelectric systems operate 24/7 off the natural gas in the line so over sizing and deep drawing batteries are not a problem, although the cleanliness and quality of the gas greatly affects the operation of the systems and often requires high maintenance “gas cleaning” before it may be used to run the thermoelectric generator. This is particularly a problem at well sites where the gas has not yet been cleaned up. 
     A generating device which would not be weather, sunlight or gas quality dependant and which would use the previously wasted pressure differential seen at well sites and city gate stations would be useful in the industry for supplying electric power to keep battery banks at full charge regardless of weather or gas quality. 
     Also, industry standards applicable to equipment placed in a potentially hazardous environment require that faults in the equipment would be unlikely to cause an explosion or fire in the area even if explosive gasses were present at the time of the equipment failure. For such a requirement, isolating the electrical circuits from the potentially explosive media with fixed barriers and static seals is highly desirable. 
     The prior art includes a variety of turbines having integrated generators. U.S. Pat. No. 4,293,777 discloses a turbine with a hollow rotor in which are disposed the elements of an electric generator. U.S. Pat. No. 4,935,650 discloses a fluid driven rotor with spaced apart ferromagnetic discs which cooperate with cavities of a ferromagnetic stator to generate electrical power. U.S. Pat. No. 2,984,751 discloses a rotor carrying an armature element which cooperates with exteriorly mounted stationary field elements. U.S. Pat. No. 3,039,007 discloses a turbine wheel having a shaft which mounts a permanent magnet for being rotatably driven inside a stator steel core. U.S. Pat. No. 2,743,375 discloses a turbo-generator having rotating bladed discs alternating with stationary discs: each of the discs carry cooperating flat radial pole-pieces and windings. U.S. Pat. No. 3,157,793 includes stator discs circumferentially disposed about rotor discs which have magnetic poles placed about their peripheries. U.S. Pat. No. 5,118,961 discloses a hollow rotor driven on it&#39;s periphery about a stator steel core. 
     Prior art integrated turbines include electrical generator elements that are in the turbine media or are separated from that media by dynamic seals. Isolation of a pressurized turbine drive mechanism from a generator using a magnetic drive is possible, but magnetic drives are both expensive and subject to magnetic decoupling and runaway under load, which may destroy a bearing in short order. 
     The disadvantages of the prior art are overcome by the present invention, and an improved differential pressure electrical generator powered by fluid pressure in the flow line is hereinafter disclosed. 
     SUMMARY OF THE INVENTION 
     The present invention provides an integrated turbine generator which has all elements of the electrical system separated from the turbine and rotor by a static seal pressure boundary. Electrical power is generated through this boundary. This approach is simple, low cost and highly reliable. The pressurized media also does not circulate in close proximity to the rotating magnets of the generator turbine or the support bearing. 
     A turbine rotor is positioned in a turbine housing such that a controlled stream of fluid may impact the rotor causing the rotor to rotate. The turbine rotor is attached to a shaft which is supported by a bearing. The shaft runs through the bearing and is formed into a generator rotor assembly containing permanent magnets around its periphery. 
     The turbine rotor, rotor shaft and generator rotor assembly are contained in a pressure tight member which directs the fluid to the exhaust port after impinging on the rotor to cause rotation. The pressure tight member that surrounds the generator rotor assembly is constructed of a material that is transparent to a magnetic field and is generally thin in cross section and approximates a shell around the rotor assembly. The outside of the shell is brought into close proximity to a generator stator assembly such that the spinning rotor will impress its magnetic field on the stator assembly and cause an electric current to be generated in the stator windings. 
     The above arrangement is highly desirable because it completely isolates the electrical circuit of the generator contained in the stator assembly from the pressurized media driving the turbine rotor and the isolation is accomplished without dynamic seals. The absence of a dynamic seal removes any rotational speed restriction imposed by the presence of a dynamic seal since higher turbine speeds will wear dynamic seals faster. In addition, by not having a dynamic seal, the rotational speed of the turbine is limited only by the bearing. This arrangement allows the generator to be reliably safe even when placed directly on a gas pipeline which is the preferred location for this type of generating device since the possibility of a fluid leak caused by a seal failure is virtually eliminated. 
     These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross section of the integrated turbine generator. 
         FIG. 2  is a cross section depicting the turbine and generator flow control valve. 
         FIG. 3  is a cross section showing the generator rotor and stator. 
         FIG. 4  is an overview of the generator in a natural gas transmission system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The integrated turbine generator assembly  10  is comprised of a flow control valve  11  connected to valve control motor  12  by a motor control shaft  13 . Valve  11  is mounted to mounting plate  14  attached to generator housing  15 . Mounting plate  14  further supports and guides motor control shaft  13 , which connects to both valve  11  and control motor  12 . 
     Turbine rotor  20  is attached to rotor shaft  21  which is supported by bearing  22  within turbine housing  23 . The inside race of bearing  22  is trapped between shoulder  50  on shaft  21  (upper surface of the bearing engages the rotor) and a sleeve shaped turbine rotor spacer  51  which is brought into contact with turbine rotor  20  when screwed onto shaft  21  at thread  52 . The outside race of bearing  22  is mounted in turbine housing  23  and secured with snap ring  24  (lower surface of the bearing engages a stop axially fixed to the turbine housing). Pressure is balanced across bearing  22  as it passes through gap  60  between turbine rotor  20  and turbine housing  23 . Pressure then enters cavity  65  and passes through turbine spacer  51  via drilled through port  61 . Pressure may then circulate around the ID of turbine spacer  51  and exit to cavity  63  via flat  62  formed on shaft  21 , thus pressure balancing the bearing. Fluid does not pass between a radially inward race and a radially outward race of the bearing. Flat  62  is one form of a fluid passageway circumferentially positioned in the shaft  21  and axially extending to provide pressurized fluid above and below the bearing. Turbine exhaust cover  25  may be attached to housing  23  by bolts not shown. 
     Referring now to  FIG. 3 , the pressurized fluid enters the system from a pressurized fluid line at inlet port  30  and the flow is controlled by valve  11 . The fluid then passes through tube  31  and enters the turbine cavity through orifice  32  to impinge on turbine blades  33  causing the turbine rotor  20  to rotate. The exhaust fluid then passes through port  26  in turbine exhaust cover  25 , as shown in  FIG. 1 . 
     Now referring to  FIGS. 1 and 2 , the rotor assembly  27  is mounted to shaft  21 , which rotates about central axis  81 , and is fixed to shaft  21  with pin  29 . A plurality of magnets  28  are circumferentially mounted on rotor assembly  27  and come in close proximity to shell housing or cap member  34 , which has a cap top or end axially opposite the turbine blades with respect to the bearing and cap sides preferably made of a material both magnetically transparent (substantially nonmagnetic) and capable of containing the fluid pressure. 
     Shell housing  34  may be attached to turbine housing  23  with bolts (not shown) and sealed with static seal  35 , such as an O-ring, to contain the fluid pressure inside the shell housing  34 . Static seal  35  and seal  36  between the turbine housing  23  and the turbine exhaust cover  25  both serve to isolate the pressure cavities  63 ,  65  from the atmosphere and the housing cavity  64  containing the electric circuits or electronic boards  70  as shown in  FIG. 1 . 
     Generator stator  40  is mounted inside housing  15 . The outside diameter of shell  34  is in close proximity to the inside diameter of generator stator  40 , such that the rotating magnets on rotor assembly  27  will excite the coils of stator  40  through the shell member  34 . 
     The stator electrical output is then routed to electronic board  70 , as shown in  FIG. 1 , which monitors the charge condition of the device to be charged and controls the operation of valve  11  to initiate or terminate the flow of pressurized fluid to the turbine and thus the generating and charging activity. 
     The generator rotor assembly may be located such that pressurized media does not circulate about the generator rotor, subjecting it to contamination by particles or debris in the media that could be attracted to the magnets on the generator rotor. Locating the support bearing such that the circulating fluid does not flow through or in close proximity to the bearing also minimizes the opportunity for fluid contaminants to enter the bearing. The turbine cavity and the generator rotor cavity may be pressure balanced, such that pressurizing and depressurizing of the generator does not draw fluid media through the bearing which could lead to bearing contamination. 
     As indicated above, a significant feature of the present invention is the absence of dynamic seals in the generator, thereby allowing reliable operation at high rotational speed (RPMs). A further advantage is the pressure balancing of the bearing, and the fact that flowing fluid does not contact either the inner components of the bearing or the electrical components of the electrical generator, thereby minimizing the likelihood of debris in the pressurized gas contaminating these components. 
     Referring now to  FIG. 4 , pressure in gas pipeline  72  is supplied to the generator  10  by supply line  74 , and is returned to the gas pipeline by a return line  76 . Current from the generator is supplied to the controller  70 , as previously discussed, and is also forwarded to battery interface  78 , which in turn charges battery  80 . Battery  80  in turn may be used to power various devices other than the controller  70 , including telecommunication devices, warning alarms, and other electrically powered systems common to natural gas pipeline applications. 
     Although the invention has been particularly described for use in a natural gas pipeline, the generator may be powered by other pressurized fluids passing through a pipeline, with the appropriate changes made to the composition of the various materials, including the seals. 
     The foregoing disclosure and description of the invention is illustrative and explanatory of preferred embodiments. It would be appreciated by those skilled in the art that various changes in the size, shape of materials, as well in the details of the illustrated construction or combination of features discussed herein may be made without departing from the spirit of the invention, which is defined by the following claims.