Abstract:
An energy cascade which is preferably fed by solar energy is made from standard solar absorbers including Seebeck elements on the upper end thereof, a self-regulating turbine including a generator arranged downstream and Seebeck elements arranged on the turbine outlet, a heat exchanger for the secondary circuit, and regulating devices for controlling the inner pressure of the primary circuit. The turbine is matched to varying operating conditions by means of suitable measures: matching of the inlet channel, changing turbine blade length for radial turbines, electronic control of the current generated in the generator for rotational speed limitation and a Seebeck heat/current exchanger in the turbine outlet channel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation under 35 U.S.C. §120 of International Application No. PCT/DE2003/003607, filed on Oct. 30, 2003, which claims priority from German No. 102 51 752.5, filed on Nov. 5, 2002. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a self-regulating turbine.  
         [0004]     2. The Prior Art  
         [0005]     DE 42 00 507 A1 discloses a turbine with very many geometrical adjustment possibilities. These possibilities include adjusting the blade wheel  3   a , the flow gap or its size and at the same time the turbine vane length  2  or turbine blade length, and the spiral  14  is not changed automatically by the blade spring  9 .  
         [0006]     Automatic geometrical alterations are disclosed by the documents U.S. Pat. No. 3,149,820 and U.S. Pat. No. 4,540,337.  
         [0007]     These documents represent only a selection from many known technical solutions.  
         [0008]     The known design concepts have long experimented with the use of variable guide vanes in particular, in order to alter the incoming flow angle and the incoming flow speed.  
         [0009]     The known forms of turbines, however, are disadvantageous in terms of the optimal efficiency during variable daily and seasonal loads and in possible pulsed operation. On account of the essentially rigid geometry of the rotor disk, or rather the turbine vanes, the optimal efficiency is achieved only twice a day when using an upstream solar absorber to produce steam or hot gas. During the remainder of the time, the turbine works uneconomically in the underloaded or overloaded region (see  FIG. 1 ).  
         [0010]     Furthermore, when using a turbine downstream from a solar absorber one must consider that the turbine geometry is designed for a mean optimal working range, which is supposed to make optimal utilization of the daily and seasonal variations. Hence, with traditional turbine geometry, the optimal working point will be set relatively low. As a result, a traditional turbine will work at least 90% of the available time at a considerable distance from optimal operating states in the underload or overload range. In other words, the turbine will achieve a mean efficiency of only perhaps 25%, as compared to an available 70%.  
       SUMMARY OF THE INVENTION  
       [0011]     It is an object of the present invention to provide a turbine which adapts to the variable daily and seasonal load of a turbine in particular and also to a possible pulsed operation, and which adapts the turbine geometry to an optimal efficiency.  
         [0012]     More particularly, it is an object of the present invention to provide a self-adapting turbine with nearly constant rotary speed for variable torque with a mass flow of 0.5 to 20.0 l/s between 0.2 MPa at the intake side and 0.1 MPa at the exit side, wherein angle-adjustable guide vanes and/or rotor vanes could not be considered in view of the required robustness and compact size of the turbine.  
         [0013]     These and other objects are achieved, in accordance with the invention, by finding other suitable measures besides the possible use of adjustable rotor vanes for adapting the turbine to changing operational states with large variances. The measures according to the invention involve, in particular: 
        adapting the inlet channel of the turbine, as well as     a variable turbine vane length for radial turbines, as well as     electronic control of the current produced in the generator in order to limit the speed after reaching the rated speed and the rated voltage, as well as     a Seebeck heat/current exchanger in the turbine outlet channel.        
 
         [0018]     Specifically, the stated purpose is achieved as follows:  
         [0019]     In a first measure, given the steam or gas masses of varying size, one must strive to change the cross section of the inlet channel so that the quantity of steam or gas arriving vertically at the particular inlet edge of the turbine vane can be kept approximately in the same optimized speed range.  
         [0020]     This objective is accomplished, according to the invention, in a first embodiment by providing an inlet channel that does not have a constantly tapering, circular-invariant cross section, as in the case of exhaust turbochargers, for example, but instead a rectangular cross section, in which there is situated an elastic sealing band that is placed under tension and closes off the channel vertically. When the quantity of steam or gas is small and the inlet pressure is low, this pretensioning of the sealing band ensures a very tiny inlet gap; when steam or gas quantities are large and the pressure is higher, the channel opens spontaneously to the maximum gap width, and the sealing band lies against the outer surface of the inlet channel at maximum opening.  
         [0021]     A second solution according to the invention is one in which the inlet channel is closed off by an adjustable-height, suitably shaped and spring-loaded lid, so that the channel cross section can likewise be adapted to the particular load condition.  
         [0022]     A third solution according to the invention is to use an elastic material, suitable to the temperature and pressure range, to form the wall of an inlet channel; this expands as the pressure increases and thus forms a circular, constantly tapering cross section which is optimal at all times.  
         [0023]     In a second measure, because of the variable gas or steam quantities arriving at approximately the same speed thanks to the adjustable cross section of the inlet channel, it proves to be advantageous to have the turbine vane of variable length, whereby a portion of the turbine vanes can be retracted into a cylindrical body rotating at the same speed, with negative shapes designed to accommodate the turbine vanes, and this co-rotating body can close off the inlet region of the turbine vanes or make it partly or fully open.  
         [0024]     A comparable measure can be achieved at the turbine outlet by again having a co-rotating cylindrical body, in which the exit ends of the turbine vanes can be retracted such that the exit region can be largely closed off or fully opened up.  
         [0025]     The co-rotating cylindrical body can have negative shapes on both sides to accommodate the particular turbine vanes, and a central bore in the middle for the fluid to flow through. The co-rotating cylindrical body can be fashioned as an impeller, in which the guide channel is bladed.  
         [0026]     The first and second measures mentioned above have the effect that the turbine, automatically adjusting to different load conditions, quickly reaches its rated speed even when the steam or gas mass flows are slight and the generator connected to the turbine likewise quickly reaches its rated voltage. A limiting of the turbine speed is achieved in that the current flow through the generator is steered by a suitable, voltage-dependent control system and the increasing current flow presents a suitably high electromagnetic moment in opposition to the turbine torque.  
         [0027]     The outer wall of the turbine outlet channel allows for heat to pass through Peltier elements to a cooling channel, where the working fluid of the secondary circuit flows before going to the heat exchanger. This measure makes possible a further recovery of current at the preferred temperature difference of 150° C. to 30° C.  
         [0028]     The automatically adjusting turbine should preferably be used for current production with solar absorbers, but it can equally be used for other operating purposes with changeable loads. Given a suitable choice of material, an operation with hot gas from combustion processes is also possible.  
         [0029]     When used with solar absorbers, additional necessary devices which complement the invention are specified for an optimal operation of the solar absorber in dependence on the solar radiation.  
         [0030]     Thus, the solar absorber at the upper end of the housing should be outfitted with a Peltier heat/current exchanger. The warm side of the exchanger closes off the solar absorber housing at the inside. The outer side of the exchanger is shaded and subjected to forced thermal ventilation and, thus, cooled.  
         [0031]     Moreover, a heat exchanger is provided downstream from the turbine-generator set, which cools the particular selected working fluid down to the absorber inlet temperature and furnishes the thermal energy recovered from the exchanger to a heating circuit or a heat reservoir, for example.  
         [0032]     In this case, the working fluid can be a gas or a liquid that is evaporated in the absorber and condensed back in the heat exchanger coming after the turbine.  
         [0033]     The desired direction of work of the working fluid is ensured by a check valve at the lower inlet of the working fluid into the solar absorber, which only allows a flow into the absorber from underneath.  
         [0034]     The absorber tubes lying in or on the absorber surface can be filled with a good gas or steam-permeable and good heat-conducting filler material, such as copper wool, in order to achieve a better transfer of heat from the absorber surface through the wall surface of the absorber tube to the working fluid being heated. The absorber tube can also be an extruded hollow profile with individual star-shaped sections, in order to present the largest possible heat transfer surface.  
         [0035]     Moreover, when using an evaporating working fluid, it is advantageous to have a variable inner pressure of the device in the absorber tubes in order to produce an optimal steam quantity depending on the process temperature which can be achieved in accordance with the solar radiation. Thus, water at normal pressure would evaporate only at 100° C., whereas familiar refrigerants do so at around 50° C. The inner pressure in the primary circuit should be coordinated with the flow temperature of the secondary circuit so that the working fluid in the primary circuit is exposed to a pressure whose corresponding boiling point is more than 5° C. above the flow temperature of the secondary circuit.  
         [0036]     This variable inner pressure is accomplished by an automatic device in which the interior of the absorber tubes is connected to a pressure regulating body, which is connected to the working fluid of the secondary circuit via a membrane not permeable to gas or steam. At low flow temperatures, the membrane is stretched by a bimetallic spring and, thus, the pressure is reduced inside the evaporation device.  
         [0037]     It proves to be especially advantageous to operate the system in pulsed mode in the case of efficiency-critical low working temperatures and low gas or steam quantity per unit of time, in that the absorber tubes are brought together in a collective absorber tube and this collective absorber tube only opens by a spring-loaded check valve at a preset pressure and the quantity of gas or steam produced by the energy input is presented to the turbine in a pulse. This pulsed mode can be smoothed out by opening up two or more collective absorber tubes for admission to the turbine in alternation.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0038]     Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.  
         [0039]     In the drawings, wherein similar reference characters denote similar elements throughout the several views:  
         [0040]      FIG. 1  is a graph showing efficiency of geometrically rigid turbines;  
         [0041]      FIG. 2  shows a first embodiment of a turbine with axial inlet flow and radial outlet flow;  
         [0042]      FIG. 3  shows the turbine embodiment of  FIG. 2  with retractable turbine vanes;  
         [0043]      FIG. 4  shows an embodiment of a turbine with a radial inlet and outlet flow;  
         [0044]      FIG. 5  shows a configuration of the radial inlet channels;  
         [0045]      FIG. 6  shows blading of the inlet, middle, and outlet parts of an embodiment of the turbine;  
         [0046]      FIG. 7  is a system view of a coupled solar absorber with a turbine according to an embodiment of the invention;  
         [0047]      FIGS. 8-12  depict an opened housing of a turbine and the rotor in different positions in respect to a counter-housing in which the rotor can be moved in to enlarge or to reduce the active area of the turbine blades;  
         [0048]      FIG. 13  is a cross-sectional view of an embodiment of a turbine showing one type of construction for varying the active blades of the turbine rotor;  
         [0049]      FIG. 14  shows an embodiment of the invention with the rotor moved to a position different from that shown in  FIG. 13 ;  
         [0050]      FIG. 15  shows a rotatable control cylinder;  
         [0051]      FIG. 16  shows an embodiment of the turbine with retractable turbine vanes moving against a spring action in accordance with another type of construction; and  
         [0052]      FIG. 17  is a perspective exterior view of the embodiment of  FIG. 13 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0053]     In one aspect, a turbine is provided with an axial inlet flow and radial outlet flow according to an embodiment of the invention. The turbine is designed for operation with varying gas or steam quantities at varying temperatures or pressures. The flow gap is closed after reaching the rated speed in dependence on the available heated gas or steam quantity or the size of the flow gap between the turbine vanes and/or the turbine blade inclination and/or the length of the turbine vanes is automatically adjusted as a function of pressure and/or temperature and the change in current flow in the generator connected downstream from the turbine is used as an additional regulating quantity for limiting the speed of the turbine.  
         [0054]     Referring now in detail to the drawings,  FIGS. 2 and 3  show a turbine in which several turbine sets  1  with an axial gas or steam borehole  2  are arranged axially to each other. Each turbine set  1  is arranged on a separating seating disk. In the central gas or steam borehole a control cylinder  3  loaded with a temperature and pressure-controlled spring force automatically opens up one, several, or all turbine sets depending on the gas or steam quantity.  
         [0055]     As shown in  FIG. 4 , one or more turbine stators  4  and turbine rotors  5  of a turbine set may be arranged intermeshing in a plane. The available gap in the rotational plane is automatically regulated by a temperature and pressure-controlled spring force, depending on the quantity of gas or steam.  
         [0056]     The turbine blade may be fastened from an elastic material so that, when gas or steam quantities are low, the tip of a turbine blade lies tangentially against the neighboring blade with only a small outlet gap. As the gas or steam quantity increases the turbine blade is spontaneously deformed so that a larger gap is opened up with a smaller angle of attack of the turbine blade.  
         [0057]     The turbine outlet channel may be configured variably thanks to a temperature and/or pressure elastic leaf spring  26 , so that when gas or steam quantities are low only a slight outlet gap is opened up. When steam or gas quantities are larger, the leaf spring is simultaneously deformed so that a larger outlet gap is opened up in the turbine outlet channel.  
         [0058]      FIG. 3  shows a turbine with retractable turbine vanes, including an impeller  6  with turbine vane holders, and a spring  9  for pretensioning a rotation body against impeller  6 . When the turbine inlet flow is radial, the turbine vane segments running from outside to inside between the turbine blades in a first segment of the channel can be retracted in a negative form co-rotating axially as an impeller  6  and change after a streamlined central flow channel of the impeller into a last segment in which the turbine blades running from inside to outside can again be retracted into the negative shape.  
         [0059]      FIG. 4  shows a turbine with radial inlet and outlet flow including a turbine inlet rotation body  7  with turbine vanes, a turbine outlet rotation body  8  with turbine vanes, and a Peltier heat/current exchanger or Seebeck elements  14  at the turbine outlet channel. A Peltier heat/current exchanger takes advantage of the Peltier effect in which current flow across a thermoelectric junction produces cooling or heating. Seebeck elements take advantage of the Seebeck effect in which current will flow when two dissimilar conductors are made into a circuit so long as the junctions are at different temperatures. As shown in  FIG. 4 , the two rotation bodies  7 ,  8  carrying the turbine vanes form, with the negative shape accommodating the turbine vanes in the shape of an impeller, a structural assembly that is pretensioned by one or more springs  9  so that when gas or steam flows are increasing the turbine vanes are partly or entirely opened up.  
         [0060]     The inlet channel may be configured with a tapering profile and can be adapted, as a function of load, to the conditions of usage by an inlet channel variable height profile  10  shown in  FIG. 4  or an inlet channel variable depth profile  11  shown in  FIG. 5 . This adaptation is achieved by springs  12  which are tensioned. Tensioning springs  12  are shown in  FIGS. 4 and 5  for the height or depth profile respectively.  
         [0061]      FIG. 6  shows blading of the inlet, middle, and outlet parts of the turbine including a profile with a wall  13 . The inlet channel, which is configured with a tapering profile, may have a cross-sectional profile varying as a function of load. Wall  13  of the profile may be made of a pressure-sensitive, elastic material.  
         [0062]     The turbine and the generator may be connected downstream to a heat exchanger  16  which cools the working fluid of a first circuit and provides the heat recovered in this way to a second circuit.  
         [0063]     The outer wall of the turbine outlet channel may have Seebeck elements  14 . The outer side of the Seebeck exchanger is formed by a cooling channel  15  through which the working fluid of a secondary circuit flows before entering the heat exchanger  16 .  
         [0064]      FIG. 7  shows a system view of a solar absorber coupled with a turbine having a downpipe  17  to an absorber inlet, a pressure regulating vessel  20  having a bimetallic controlled membrane  21 , and a Seebeck heat/current exchanger element  25  on the absorber. As shown in  FIG. 7 , the turbine with generator and the heat exchanger in the first circuit, after downpipe  17  with a check valve or valves  18  closing it off, are followed by one or more absorber tubes  19  in an ascending absorber for incoming thermal energy, including solar energy, which supply hot gas or steam to the turbine.  
         [0065]     An evaporable liquid or a gas may be used as the working fluid in the first circuit. Preferably, a working fluid which boils at low temperatures is used. For such boiling, the pressure in the first circuit can be lowered to the suitable low boiling temperature with more than 5 degrees Kelvin above the flow temperature of the heat exchanger  16  by self-regulating vessel  20  with bimetallic membrane  21 .  
         [0066]     The heater tubes, for better transfer of heat to the working fluid, may be additionally outfitted with good heat-conducting and gas or steam-permeable filler bodies  22 . The heater tubes may also be extruded profiles having individual flow channels separated by ridges.  
         [0067]     Two or more absorbers may be alternately admitted to the turbine in pulsed mode or smoothed pulse mode across collective absorber tubes  23 . The pulse operation is preferably regulated by coupled, pretensioned check valves  24  on the collective absorber tubes.  
         [0068]     Either a rotating turbine base plate at the side away from the turbine vanes or the rotating impeller on its outside may have permanent magnets of alternating polarity. The excitation windings of the generator may be arranged opposite the rotation gap.  
         [0069]     The absorbers may be closed off by Seebeck elements at the upper end of the housing which are directly shaded and under forced air cooling from the outside.  
         [0070]      FIGS. 8-12  show an opened housing of an embodiment of the turbine and the rotor in different positions in respect to a counter-housing in which the rotor can be moved in to enlarge or to reduce the active area of the turbine-blades.  
         [0071]     In  FIG. 8 , the blades are quite small as shown on the right hand side thereof. The blades are larger in  FIG. 9  and larger in  FIG. 10 .  FIG. 11  is a side view of the turbine-blades with the blades being quite large. In  FIG. 12 , the blades just dive in the right hand side rotatable counter-part.  
         [0072]      FIG. 13  shows turbine housing  30  in which a turbine wheel, i.e. turbine rotor  5 , is shifted against a spring  31  for movement deeper and deeper into a rotatable control cylinder  3 .  FIG. 15  shows control cylinder  3  in more detail and  FIG. 17  shows a tiny portion of control cylinder  3 .  
         [0073]     Input channels and output channels are designated with reference numerals  32  and  33  in  FIG. 13 . A generator  34  is shown within housing  30  but may be outside housing  30  on the rotary shaft  35  of the turbine rotor  5  and the control cylinder  3 .  
         [0074]     In order to cause axial movement of turbine rotor  5 , turbine rotor  5  is fixed on a part of shaft  35  which is, for example, quadratic in its square area. See  FIG. 13 .  
         [0075]     In accordance with the invention, there are at least two different types of constructions that can be used to vary the area of the active blades of the turbine. One form of construction is shown in  FIGS. 13 and 17  (and  FIGS. 8-12 ) where the turbine rotor moves in and out of control cylinder  3 . Another possibility is shown in  FIG. 16  where control cylinder  3  moves against a spring action and is shown also in  FIG. 3 .  
         [0076]     Although only a few embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.