Abstract:
A solar-energy heat power-generating system and thermoelectric conversion device thereof, the thermoelectric conversion device comprising a power generator ( 5 ), an air compressor, a turbine and an intermediate body ( 12 ) fixedly connected between the air compressor and the turbine; the interior of the intermediate body ( 12 ) is rotatably connected to a transmission shaft ( 28 ); the transmission shaft ( 28 ) is fixedly connected to the rotating shaft of the power generator ( 5 ); the air compressor impeller ( 7 ) of the air compressor and the turbine impeller ( 18 ) of the turbine are both installed on the transmission shaft ( 28 ); the power generator ( 5 ) is also connected to a conducting wire ( 3 ) for inputting current; the solar-energy heat power-generating system comprises a heat collector and the thermoelectric conversion device; the air compressor of the thermoelectric conversion device is located upstream of the heat collector, and the turbine is located downstream of the heat collector.

Description:
[0001]    This application claims priority from Chinese Patent Application No. 201110197353.1 titled “SOLAR THERMAL POWER GENERATION SYSTEM AND THERMOELECTRIC CONVERSION DEVICE THEREOF”, filed with the Chinese State Intellectual Property Office on Jul. 14, 2011, the entire disclosure of which is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present application relates to the technical field of solar thermal power generation, and particularly to a thermoelectric conversion device for a solar thermal power generation system. In addition, the present application further relates to a solar thermal power generation system including the above thermoelectric conversion device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Solar energy is one of the new energies that are most promising and most likely to meet continually increased demand for energy in future social development, and has characteristics such as unlimited reserves, wide distribution, clean utilization and the economical efficiency. The solar thermal power generation has some characteristics, for example, better adaptability to power grid load, high photoelectric conversion efficiency, scale effect with ease, environment-friendly manufacturing process of consumptive material, better adjustability of the electric power, and so on. Thus, the solar thermal power generation is an important development direction of utilization of solar power generation in the future. 
         [0004]    The basic technical idea of the solar thermal power generation is that: the sunlight is converged through a heat collector to increase the energy density of light energy; the collected light energy is absorbed by a heat absorbing device and converted into heat energy; the heat energy is transferred to working medium to increase the internal energy of the working medium; and then the internal energy in the working medium is converted into mechanical energy through a heat engine and a generator is driven so that the mechanical energy is further converted into electric energy to be output. In the whole process of energy conversion, converting the heat energy into the mechanical energy is the most critical aspect. 
         [0005]    Currently, there are mainly three kinds of the heat engine that are applicable to the solar thermal power generation system, i.e., the steam turbine based on Rankine cycle, the Stirling engine based on Stirling cycle and the small-scale gas turbine based on Brayton cycle. Specifically, the steam turbine can use hydrocarbons (halogenated hydrocarbons) or water having low boiling point and good heat stability as the working medium. However, because the temperature that the working medium can withstand is low, the heat efficiency is low. The steam turbine is generally used in a slot-type power generation system with low the heat collection temperature. The Stirling engine uses hydrogen or helium working medium which has the dynamic seal pressure up to 15 Mp or more when working, so that the working reliability, stability and lifetime is limited to some extent. The small-scale gas turbine can directly use air as the working medium. That is, air is compressed by a compressor, then absorbs heat and is heated up in a working medium heating device, and then goes into a turbine for expanding and doing work; and the mechanical work in turn drives the compressor and the generator for outputting current. The small-scale gas turbine is simple in the design, has no demanding seal conditions, directly obtains and discharges the working medium from and into atmosphere, and has better reliability and stability. 
         [0006]    However, for using the small-scale gas turbine as the heat engine for solar thermal power generation equipment, there are following several problems to overcome in addition to difficulty in designing impellers of the compressor and the turbine with high efficiency as well as high speed generator: 
         [0007]    1) start-up performance of the system: because the turbine and the compressor are coupled to each other, after the compressor drives the high-pressure airflow into the heat collector, the heat generated by the heat collector can be absorbed by the airflow, and the formed high-temperature and high-pressure airflow can pass through the turbine to output mechanical work and to drive the compressor and the generator. Thus, when the system is actuated, an additional starting device is required to give an initial rotating speed to the compressor. In this way, the whole system can be actuated smoothly, resulting in a more complex structure of the thermoelectric conversion device. 
         [0008]    2) lifetime and reliability of the high speed generator: because the operating rotating speed of the small-scale gas turbine is up to 100000 to 200000 r/min, cooling requirement of the generator is extremely demanding. It is necessary to provide a good solution to cooling, otherwise the lifetime and reliability of the generator will be affected. 
         [0009]    3) operation stability and robustness of the system: when the high-temperature air going into the turbine air inlet deviates from the designed working temperature and pressure of the turbine due to fluctuation in solar radiation and so on, the rotating speed of the turbine impeller will significantly fluctuate, resulting in a fluctuation in the rotating speed of the turbine impeller, and the flow and pressure of the air going into the working medium heating device will fluctuate as well, thus further leading to fluctuation in the rotating speed of the turbine impeller, and causing loss of stability of the system. 
       SUMMARY OF THE INVENTION 
       [0010]    A technical problem to be solved according to the present application is to provide a thermoelectric conversion device for a solar thermal power generation system, which has a better startability since there is no need for additionally providing a start-up device to rotate a compressor when the thermoelectric conversion device is started, and has a better stability since the generator can be better cooled in the process of thermoelectric conversion. Another technical problem to be solved according to the present application is to provide a solar thermal power generation system including the thermoelectric conversion device. 
         [0011]    In order to solve the above technical problems, there is provided according to the present application a thermoelectric conversion device for a solar thermal power generation system including a generator, a compressor, a turbine and an intermediate body fixedly connected between the compressor and the turbine. A transmission shaft is rotatably connected inside the intermediate body. The transmission shaft is fixedly connected to a rotating shaft of the generator, and a compressor impeller of the compressor and a turbine impeller of the turbine both are mounted on the transmission shaft. The generator is further connected to a lead for inputting current. When the system is started, the generator functions as an electric motor; and when the system is in normal operation, the generator functions to produce electricity. 
         [0012]    Preferably, the generator is arranged in an air inlet flowing passage inside the compressor. 
         [0013]    Preferably, a heat insulation plate is provided between a rear flange of the intermediate body and a turbine volute of the turbine, and an annular nozzle is formed between the heat insulation plate and a vertical rear side wall of the turbine volute. 
         [0014]    Preferably, at least one airflow guide vane for adjusting the injection-expansion ratio of airflow within the nozzle is provided in the nozzle. 
         [0015]    Preferably, the heat insulation plate is provided therein with a through hole oriented in the fore-and-aft direction. An outer end of the airflow guide vane is pivotally connected in the through hole, and an inner end of the airflow guide vane swings as the outer end rotates in the through hole. 
         [0016]    Preferably, a rear side wall of the intermediate body is provided with an arc-shaped hole, and a shift lever slidable along the arc of the arc-shaped hole is inserted into the arc-shaped hole. The shift lever extends through a rear end of the intermediate body to be connected to a slide ball that rotates in an end surface along with the shift lever. A shift fork is provided in front of the heat insulation plate. The outer end of the airflow guide vane is fixedly connected between two fork-shaped portions of the shift fork, and a straight-bar portion of the shift fork is slidably inserted into a through hole in the slide ball. 
         [0017]    Preferably, a diffusing pipe of the compressor is an annular space formed between an end surface of a positioning boss on the front flange of the intermediate body and a corresponding portion of a compressor volute. 
         [0018]    Preferably, the intermediate body is rotatably connected to the transmission shaft through a floating bearing, and a thrust bearing is provided in front of the floating bearing. An oil inlet hole is provided at the top end of the intermediate body. Lubrication passages leading to two of the floating bearing and the thrust bearing are provided at the bottom end of the oil inlet hole. An oil outlet hole is further provided at the bottom end of the intermediate body. An oil baffle plate is further provided at a lower end of a transition ring located in front of the thrust bearing, and the oil baffle plate is arranged to be inclined towards the oil outlet hole. 
         [0019]    Preferably, a sealing element is provided at contacting area between a front end of the transition ring and a bearing cover of the thrust bearing, and an oil throwing plate that projects towards the outside of the transmission shaft is further provided on the transition ring between the sealing element and the oil baffle plate. 
         [0020]    Preferably, a projecting ring is provided at the rear side of the rear floating bearing of the transmission shaft, the sealing element is provided at a contacting area between a rear end of the projecting ring and a side wall of the intermediate body. 
         [0021]    In the thermoelectric conversion device for a solar thermal power generation system according to the present application, a transmission shaft is rotatably connected inside the intermediate body; the transmission shaft is fixedly connected to a rotating shaft of the generator, and a compressor impeller of the compressor and a turbine impeller of the turbine both are mounted on the transmission shaft; the generator is further connected to a lead for inputting current; when the system is started, the generator functions as an electric motor; and when the system is in normal operation, the generator functions to produce electricity. 
         [0022]    By employing the thermoelectric conversion device with this structural form, when the system is started, external current is input to the generator through the lead so as to drive the rotating shaft of the generator to rotate. At this time, the generator is used as an electric motor, and drives the compressor impeller to rotate. Under the action of the compressor impeller, air coming from the atmospheric environment enters through a compressor entrance and flows through an air flowing passage into compressor impeller. The air obtains energy in a vane flowing passage of the compressor impeller to increase the flowing speed, temperature and pressure thereof. Then the air goes into a diffusing pipe and reduces flowing speed in the diffusing pipe, but further increase the temperature and pressure thereof, thus forming high-pressure air which is output through a compressor volute and a compressor air outlet. The high-pressure air described above goes into a heat exchanger through a pipe with a heat insulation layer, and then flows into a working medium heating device where the air is heated at constant pressure so as to form high-temperature air. The high-temperature air goes into turbine volute through a turbine air inlet and then flows through a nozzle. In the nozzle, the high-temperature air expands so as to achieve pressure reduction, temperature reduction and speed increase, and thus part of pressure energy is converted into kinetic energy. A high-speed airflow flowing out from the nozzle impacts a turbine impeller, and further expands and does work in a flowing passage of the turbine impeller, so as to achieve pressure reduction, temperature reduction and speed increase and push the turbine impeller to rotate. Finally, the air is discharged through an exhaust pipe of the turbine, thus forming the air after doing work. The air after doing work goes into a heat exchanger through a pipe with a heat insulation layer. The remaining heat in the heat exchanger is transferred to the air coming from the compressor, so as to recover part of the energy therein. Thus, the whole cyclic process is completed. 
         [0023]    As the generator functioning as an electric motor causes increase of the rotating speed of the compressor impeller, the power output from the turbine is increasingly large, and the driving power required to be output by the generator is increasingly small, until the power output from the turbine exceeds the power required for the compressor. At this time, the function of the generator is changed from an electric motor to a generator and starts to output electric energy. 
         [0024]    As can be seen from the above working process, in the thermoelectric conversion device with the above structure, in addition to outputting electric energy, the generator functions as an electric motor so as to drive the compressor to rotate at an initial stage of system startup, thereby converting the normal-temperature air into the high-temperature and high-pressure airflow. As compared with the prior art, since there is no need for additionally providing start-up equipment to rotate the compressor, the thermoelectric conversion device according to the application has good startability, so that the thermoelectric conversion device can have simple and compact structure, relatively reduced contour dimension and smaller occupying space. 
         [0025]    The present application also provides a solar thermal power generation system, which includes a heat collector and the above thermoelectric conversion device. The thermoelectric conversion device is provided at an output end of the heat collector. 
         [0026]    Because the thermoelectric conversion device has the above technical effects, the solar thermal power generation system including the thermoelectric conversion device also has the corresponding technical effects, which will not be described in detailed herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a partially structural sectional view of a specific embodiment of a thermoelectric conversion device according to the present application; 
           [0028]      FIG. 2  is an overall outline view of a solar thermal power generation system including the thermoelectric conversion device of  FIG. 1 ; 
           [0029]      FIG. 3  is a sectional view taken along line A-A in  FIG. 1 ; 
           [0030]      FIG. 4  is a sectional view taken along line B-B in  FIG. 1 ; 
           [0031]      FIG. 5  is a partial enlarged view of part III in  FIG. 4 ; 
           [0032]      FIG. 6  is a partial enlarged view of part II in  FIG. 1 ; 
           [0033]      FIG. 7  is a sectional view taken along line C-C in  FIG. 6 ; 
           [0034]      FIG. 8  is a view seeing from the direction F in  FIG. 1 ; 
           [0035]      FIG. 9  is a partial enlarged view of part I in  FIG. 1 ; 
           [0036]      FIG. 10  is a longitudinal sectional schematic view of an intermediate body. 
       
    
    
       [0037]    In  FIGS. 1 to 10 , the correspondences between the reference numerals and the component names are listed as follows: 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
             
             
               
                  1-air filtering assembly 
                  2-motor supporter 
                  3-lead 
               
               
                  4-air inlet flowing passage 
                  5-generator 
                  6-air inlet pipe 
               
               
                  7-compressor impeller 
                  8-compressor volute 
                  9-compressor air outlet 
               
               
                 10-high-pressure air 
                 11-front flange 
                 12-intermediate body 
               
               
                 13-oil inlet hole 
                 14-lubricating oil 
                 15-shift lever 
               
               
                 16-nozzle 
                 17-turbine volute 
                 18-turbine impeller 
               
               
                 19-exhaust pipe 
                 20-air after doing work 
                 21-fastening bolt 
               
               
                 22-turbine air inlet 
                 23-high-temperature air 
                 24-rear flange 
               
               
                 25-oil outlet hole 
                 26-oil baffle plate 
                 27-diffusing pipe 
               
               
                 28-transmission shaft 
                 29-tightening nut 
                 30-bearing assembly 
               
               
                 31-air deflector 
                 32-normal-temperature air 
                 33-retaining ring 
               
               
                 34-seal assembly 
                 35-thrust bearing 
                 36-lubrication passage 
               
               
                 37-floating bearing 
                 38-thrust ring 
                 39-transition ring 
               
               
                 40-oil throwing plate 
                 41-bearing cover 
                 42-slide ball 
               
               
                 43-major clamp piece 
                 44-fastening assembly 
                 45-retaining ring 
               
               
                 46-heat insulation plate 
                 47-minor clamp piece 
                 48-shift fork 
               
               
                 49-airflow guide vane 
                 50-rotating shaft 
                 51-pin assembly 
               
               
                 52-retaining sleeve 
                 53-arc-shaped hole 
                 54-positioning and clamping ring 
               
               
                 55-bearing seat hole 
                 56-positioning boss 
                 57-heat exchanger 
               
               
                 58-working medium heating device 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    An object of the present application is to provide a thermoelectric conversion device for a solar thermal power generation system. The thermoelectric conversion device is actuated without additional start-up device for driving a compressor to rotate, thus having good startability, and has an advantage of better stability since the generator can be better cooled in the process of thermoelectric conversion. Another object of the present application is to provide a solar thermal power generation system including the thermoelectric conversion device. 
         [0039]    In order that the person skilled in the art can better understand technical solutions of the present application, the present application will be further described in detail in conjunction with the accompanying drawings and the embodiments hereinafter. 
         [0040]    Referring to  FIGS. 1 and 2 ,  FIG. 1  is a partially structural sectional view of a specific embodiment of a thermoelectric conversion device according to the present application, and  FIG. 2  is an overall outline view of a solar thermal power generation system including the thermoelectric conversion device of  FIG. 1 . 
         [0041]    In one specific embodiment, as shown in  FIGS. 1 and 2 , the thermoelectric conversion device according to the present application mainly include a compressor, an intermediate body  12 , a turbine, a heat exchanger  57 , a working medium heating device  58  and a generator  5 . The compressor is a component that does work to the normal-temperature air  32  by using vanes rotating at high speed so as to increase the pressure of the air. The turbine is an engine that generates power by using fluid impact to rotate an impeller. The intermediate body  12  is an intermediate component that connects the compressor and the turbine. Specifically, a front flange  11  and a rear flange  24  of the intermediate body  12  are fixedly connected to the compressor and the turbine respectively, and a transmission shaft  28  is rotatably connected inside the intermediate body  12 . The transmission shaft  28  is fixedly connected with a rotating shaft of the generator  5 , and a compressor impeller  7  and a turbine impeller  18  both are mounted on the transmission shaft  28 . The generator  5  is further connected with a lead  3  for inputting current. When the system is started, the generator  5  functions as an electric motor; and when the system is in normal operation, the generator  5  functions as a generator. 
         [0042]    By employing a thermoelectric conversion device in such a structural form, when the system is started, external current is input to the generator  5  through the lead  3  so as to drive the rotating shaft of the generator  5  to rotate. At this time, the generator  5  is used as an electric motor, and drives the compressor impeller  7  to rotate. Under the action of the compressor impeller  7 , air coming from the atmospheric environment enters through a compressor entrance and flows through an air flowing passage into compressor impeller  7 . The air obtains energy in a vane flowing passage of the compressor impeller  7  to increase the flowing speed, temperature and pressure thereof. Then the air goes into a diffusing pipe  27  and reduces flowing speed in the diffusing pipe  27 , but further increase the temperature and pressure thereof, thus forming high-pressure air  10  which is output through a compressor volute  8  and a compressor air outlet  9 . The high-pressure air  10  described above goes into a heat exchanger  57  through a pipe with a heat insulation layer, and then flows into a working medium heating device  58  where the air is heated at constant pressure so as to form high-temperature air  23 . The high-temperature air  23  goes into turbine volute  17  through a turbine air inlet  22  and then flows through a nozzle  16 . In the nozzle  16 , the high-temperature air  23  expands so as to achieve pressure reduction, temperature reduction and speed increase, and thus part of pressure energy is converted into kinetic energy. A high-speed airflow flowing out from the nozzle  16  impacts a turbine impeller  18 , and further expands and does work in a flowing passage of the turbine impeller  18 , so as to achieve pressure reduction, temperature reduction and speed increase and push the turbine impeller  18  to rotate. Finally, the air is discharged through an exhaust pipe  19  of the turbine, thus forming the air after doing work  20 . The air after doing work  20  goes into a heat exchanger  57  through a pipe with a heat insulation layer. The remaining heat in the heat exchanger  57  is transferred to the air coming from the compressor, so as to recover part of the energy therein. Thus, the whole cyclic process is completed. 
         [0043]    As the generator  5  functioning as an electric motor causes increase of the rotating speed of the compressor impeller  7 , the power output from the turbine is increasingly large, and the driving power required to be output by the generator  5  is increasingly small, until the power output from the turbine exceeds the power required for the compressor. At this time, the function of the generator  5  is changed from an electric motor to a generator and starts to output electric energy. 
         [0044]    As can be seen from the above working process, in the thermoelectric conversion device with the above structure, in addition to outputting electric energy, the generator  5  functions as an electric motor so as to drive the compressor to rotate at an initial stage of system startup, thereby converting the normal-temperature air  32  into the high-temperature and high-pressure airflow. As compared with the prior art, since there is no need for additionally providing start-up equipment to rotate the compressor, the thermoelectric conversion device according to the application has good startability, so that the thermoelectric conversion device can have simple and compact structure, relatively reduced contour dimension and smaller occupying space. 
         [0045]    It should be noted that the specific mounting position of the generator  5  is not limited in the above specific embodiment. Any thermoelectric conversion device with the generator  5  provided with the lead  3  for inputting current and also functioning as start-up equipment is deemed to fall into the protection scope of the present application. 
         [0046]    In addition, the orientation word “rear” as used herein refers to the flowing direction of the normal-temperature gas after entering through the compressor entrance, that is, the direction from left to right in  FIG. 1 . The orientation word “front” is contrary to the above direction, that is, the direction from right to left in  FIG. 1 . It should be appreciated that these orientation words are defined on the basis of the accompanying drawings, and the presence thereof should not affect the scope of protection of the present application. 
         [0047]    It is possible to further define the mounting position of the generator  5  described above. 
         [0048]    In another specific embodiment, as shown in  FIG. 1 , the above generator  5  can be arranged in an air inlet flowing passage  4  inside the compressor. By employing such a structure, when the unit is in normal operation, part of the normal-temperature air  32  flows through between cooling fins of the generator  5  and compulsorily cools the generator  5 , so that the operating temperature of the generator  5  is maintained within reasonable range, thus ensuring the service time of the generator  5 . As compared with the prior art, the present application can better solve the cooling problem while also saving electric energy consumption on cooling, with no need for additionally providing an electrically driven cooling fan. 
         [0049]    In a specific solution, as shown in  FIG. 3 , it is a sectional view taken along line A-A in  FIG. 1 . A motor supporter  2  can be provided inside the air inlet pipe  6  of the compressor. An air deflector  31  can also be provided on the air inlet side of the motor supporter  2 , and a bearing assembly  30  can be provided inside the air deflector  31 . The bearing assembly  30  and the generator  5  both are mounted on the motor supporter  2 . A lead  3  of the generator  5  sequentially passes through an internal passage of one leg of the motor supporter  2  and out of a lead hole in the air inlet pipe  6  so as to be connected to other components than the generator  5 . Of course, the above generator and the lead thereof are not limited to the above mounting mode, and may also be in other specific structural forms. 
         [0050]    Still further, the turbine impeller  18  can be fixedly connected to a rear end of the transmission shaft  28  through a fastening bolt  21 . The compressor impeller  7  can be fixedly connected to a front end portion of the transmission shaft  28  through a tightening nut  29 , and the rotating shaft of the generator  5  can also be connected to a most front end of the transmission shaft through a nut. Of course, the generator  5 , the compressor impeller  7  and the turbine impeller  18  can also be fixedly connected to the transmission shaft  28  in other ways. An air filtering assembly  1  can also be provided at an inlet opening portion of the air inlet pipe  6  of the compressor, so as to preliminarily filter the normal-temperature air  32 , thus preventing dust or impurities in the air from going into the compressor and ensuring the working stability and reliability of the thermoelectric device. 
         [0051]    The diffusing pipe  27  of the compressor is an annular space formed between an end surface of a positioning boss  56  on the front flange  11  of the intermediate body  12  and a corresponding portion of a compressor volute  8 . By employing the diffusing pipe  27  with this structural shape, it is possible to more quickly reduce the flowing speed, temperature and increase the pressure of the air going into the compressor, so as to form high-pressure air  10 . 
         [0052]    It is possible to further arrange the thermoelectric conversion device in other specific structural forms. 
         [0053]    In another specific embodiment, a heat insulation plate  46  is provided between the rear flange  24  of the intermediate body  12  and the turbine volute  17 . The rear flange  24  can be provided thereon with a positioning clamping ring  54  which fixes the heat insulation plate  46  onto the turbine volute  17 . An annular nozzle  16  is formed between the heat insulation plate  46  and a vertical rear side wall of the turbine volute  17 . Because the high-temperature airflow enters into the annular nozzle  16 , and expands in the nozzle  16  so as to achieve pressure reduction, temperature reduction and speed increase, the heat insulation plate  46  provided between the intermediate body  12  and the turbine volute  17  is able to avoid the heat of the high-temperature air from diffusing outside of the volute and causing unnecessary heat loss, so that the heat of the high-temperature air is fully utilized and the conversion rate and working reliability of the thermoelectric conversion device are increased. 
         [0054]    Of course, the specific structural form of the heat insulation plate  46  is not limited herein. For example, the heat insulation plate  46  can be provided thereon with means such as heat insulating groove, heat insulating slot and heat insulating coating, or a structural form such as multi-layer heat insulation can by employed. Any heat insulation plate  46  arranged between the rear flange  24  of the intermediate body  12  and the turbine volute  17  and functioning to insulate heat is deemed to fall into the protection scope of the present application. 
         [0055]    In a further solution, referring to  FIGS. 4 and 5 ,  FIG. 4  is a sectional view taken along line B-B in  FIG. 1 ; and  FIG. 5  is a partial enlarged view of part III in  FIG. 4 . At least one airflow guide vane  49  for adjusting the injection-expansion ratio of airflow within the nozzle  16  is provided in the nozzle  16 . Specifically, the heat insulation plate  46  may be provided with a through hole oriented in fore-and-aft direction, and an outer end of the airflow guide vane  49  is pivotally connected in the through hole, so that an inner end of the airflow guide vane  49  swings as the outer end rotates in the through hole. 
         [0056]    By employing this structural form, when the thermoelectric conversion device is in normal operation, the guide vane  49  is located at a position b. When the pressure and flow of the high-temperature air  23  going into the turbine air inlet  22  is lower than the design value, the outer end of the airflow guide vane  49  pivotally connected to the heat insulation plate  46  can be rotated to drive the inner end of the airflow guide vane  49  to swing to a position a, so as to reduce the outlet cross-sectional area of the nozzle  16  and increase the flowing velocity of the air when it goes into the turbine impeller  18 . As a result, the rotating speed of the turbine is increased and the boost pressure and air supply amount for the compressor are increased correspondingly, thereby increasing the flowing speed and pressure of the air going into the turbine. When the pressure and flow of the high-temperature air going into the turbine air inlet  22  is higher than the design value, the airflow guide vane  49  can be rotated to a position c, so as to increase the outlet cross-sectional area of the nozzle  16  and reduce the flowing speed of the high-temperature air  23 . As a result, the rotating speed of the turbine is reduced and the supply air pressure and supply air flow for the compressor are reduced, thereby reducing the flowing speed and pressure of the air going into the turbine, so as to avoid overspeed of the system. 
         [0057]    As can be seen from the above adjusting process, the rotating speed of the turbine impeller  18  can be adjusted by mounting the airflow guide vane  49 , so that the rotating speed of the system when it is operating is within the design range, thus avoiding excessive fluctuation of the rotating speed of the turbine impeller  18  due to larger fluctuation in solar radiation and so on. As compared with the prior art, the working stability and robustness of the thermoelectric conversion device are significantly improved, so that it has better anti-interference performance. 
         [0058]    The thickness in the fore-and-aft direction and the length from the outer end to the inner end of the airflow guide vane  49  are not limited in the above specific embodiment. The thickness in the fore-and-aft direction of the airflow guide vane  49  can fully or partially occupy the space between the heat insulation plate  46  and the vertical side wall of the turbine volute  18 . The length from the outer end to the inner end of the airflow guide vane  49  can be slightly larger, or smaller than the radial width of the annular nozzle  16 . The user can make options according to the magnitude of shifting angle and the magnitude of target adjusting amount. 
         [0059]    Of course, the airflow guide vane  49  is not limited to the above mode and can be in other modes. For example, the inner end of the airflow guide vane  49  may be connected fixedly and pivotally to the heat insulation plate  46 , and the injection-expansion ratio of the airflow within the nozzle  16  may be adjusted through the outer end of the airflow guide vane  49 . For another example, the airflow guide vane  49  can also be inserted into the heat insulation plate  46  in such a manner to be slidable in the fore-and-aft direction. When the fluctuation in rotating speed is relatively large, the airflow guide vane  49  is driven to slide in the fore-and-aft direction. The rotating speed of the turbine impeller  18  may be adjusted by changing the thickness of airflow guide vane  49  in the fore-and-aft direction. In addition, the airflow guide vane  49  adjusting the flow can also be in other specific structural forms. 
         [0060]    It should be noted that the orientation word “outer” used herein refers to the direction along which the air diffuses outwards from the center of the turbine impeller  18  in the end surface of the volute, that is, the direction from bottom to top in  FIG. 5 . The orientation word “inner” is contrary to the above direction, that is, the direction from top to bottom in  FIG. 5 . The term “end surface” refers to the surface in the vertical direction in  FIG. 1 . It should be appreciated that these orientation words are established based on the accompanying drawings, and the presence thereof should not affect the scope of protection of the present application. 
         [0061]    Referring to  FIGS. 6 ,  7  and  8 ,  FIG. 6  is a partial enlarged view of part II in  FIG. 1 ;  FIG. 7  is a sectional view taken along line C-C in  FIG. 6 ; and  FIG. 8  is a view seeing from the direction F in  FIG. 1 . 
         [0062]    In a more specific solution, as shown in  FIGS. 6 ,  7  and  8 , a rear side wall of the intermediate body  12  is provided with an arc-shaped hole  53 , and a shift lever  15  slidable along the arc of the arc-shaped hole  53  is inserted into the arc-shaped hole  53 . The shift lever  15  passes through a rear end of the intermediate body  12  to be connected to a slide ball  42  that rotates in an end surface along with the shift lever  15 . A shift fork  48  is provided at the front side of the heat insulation plate  46 . The outer end of the airflow guide vane  49  is fixedly connected between two fork-shaped portions of the shift fork  48 , and a straight-bar portion of the shift fork  48  is slidably inserted into a through hole of the slide ball  42 . 
         [0063]    By employing this structural form, when the pressure and flow of the high-temperature air  23  going into the turbine air inlet  22  is higher or lower than the design value, the shift lever  15  is rotated so as to slide in the arc-shaped hole  53  and drive the slide ball at the rear end of the shift lever  15  to rotate accordingly. Because the fork-shaped portions of the shift fork  48  are fixedly connected to the airflow guide vane and the straight-bar portion of the shift fork  48  is slidably inserted into a through hole of the slide ball  42 , the rotation of the slide ball  42  in the end surface can drive the fork-shaped portions of the shift fork  48  to rotate appropriately, thereby driving the outer end of the airflow guide vane  49  fixedly connected to the fork-shaped portions to rotate. As a result, the adjustment of the injection-expansion ratio of the airflow within the nozzle  16  is achieved. 
         [0064]    Thus, as can be seen, by employing the above manipulating structure, when the angle of the airflow guide vane  49  is adjusted as desired, the operator merely shifts the shift lever  15 , so that it slides in the arc-shaped hole  53 , thereby achieving the angle adjustment of the airflow guide vane  49 , which simplifies the operation of flow adjustment. When the fluctuation in solar radiation is relatively large, the adjusting process can be completed rapidly, thus having a good responsibility. 
         [0065]    Of course, the mode of fixed connection between the fork-shaped portions at the outer end of the shift fork  48  and the outer end of the airflow guide vane  49  is not limited in the above specific embodiment, and the fork-shaped portions can be fixedly connected to a rotating shaft  50 , inserted into a through hole of the heat insulation plate  46 , of the airflow guide vane  49  via a pin assembly  51 . A retaining sleeve  52  can also be provided between the through hole of the heat insulation plate  46  and the rotating shaft  50  of the airflow guide vane  49 , and is also fixedly connected to the fork-shaped portions of the shift fork  48 . The provision of the retaining sleeve  52  herein can have a certain protective action on the rotating shaft  50  of the airflow guide vane  49  and avoid the rotating shaft  50  from subjecting larger wear due to excessive rotation, which would otherwise cause hot air leakage and so on. 
         [0066]    The specific structural form by which the shift lever  15  drives the slide ball  42  to rotate is not limited in the above specific embodiment. Specifically, a clamp structure can be fixedly connected to the rear end of the shift lever  15  and the slide ball  42  can be clamped in the clamp structure so that the slide ball  42  can be freely rotated but can not be moved in the inward-outward direction. More specifically, a major clamp piece  43  and a minor clamp piece  47  can be arranged at two sides of the slide ball  42 , and the major clamp piece  43  and the minor clamp piece  47  are connected as one piece through a fastening assembly  44 . A retaining ring  45  can also be provided at an inner end of the major clamp piece  43 . The retaining ring  45  presses the clamp assembly against the front side of the heat insulation plate  46 , so that the clamp structure can be rotated about the inner end thereof in the end surface. 
         [0067]    In summary, the operation for adjusting the injection-expansion ratio within the nozzle  16  can be stated completely as follow: firstly, the shift lever  15  is manipulated so that it slides in the arc-shaped hole  53 , thereby driving the outer end of the clamp structure to rotate about the inner end thereof and thus driving the slide ball  42  in the clamp assembly to rotate therewith; then, the straight-bar portion of the shift fork  48  is driven to slide in the slide ball  42 , and the fork-shaped portions of the shift fork  48  drive the rotating shaft  50  of the airflow guide vane  49  to rotate, thereby achieving the position change of the airflow guide vane  49  so as to adjust the injection-expansion ratio within the nozzle  16 ; and thus, adjustment of the rotating speed of the turbine impeller  18  is achieved finally. 
         [0068]    Thus, as can be seen, the above manipulating device, in which movement is transferred sequentially from the shift lever  15 , the clamp structure, the slide ball  42 , the shift fork  48  to the airflow guide vane  49 , has the technical effects such as easy manipulation, convenient control and actuate adjustment. Of course, the manipulating device for the airflow guide vane  49  is not limited to the above specific structural form and can also be a variety of other manipulation modes. 
         [0069]    A lubricating system and a cooling system may further be provided in the above thermoelectric conversion device. 
         [0070]    Referring to  FIGS. 9 and 10  in conjunction with  FIG. 1 ,  FIG. 9  is a partial enlarged view of part I in  FIG. 1 ; and  FIG. 10  is a longitudinal sectional schematic view of the intermediate body  12 . 
         [0071]    In another specific embodiment, the intermediate body  12  is rotatably connected with the transmission shaft  28  through floating bearings  37 . A thrust bearing  35  is provided in front of the floating bearings  37 . An oil inlet hole  13  is provided at the top end of the intermediate body  12 . Lubrication passages  36  leading to the two floating bearings  37  and the thrust bearing  35  are provided at the bottom end of the oil inlet hole  13 . An oil outlet hole  25  is further provided at the bottom end of the intermediate body  12 . A thrust ring  38  and a transition ring  39  are further provided in front of the thrust bearing  35 . The thrust ring  38  cooperates with a shaft shoulder of the transmission shaft  28  and a thrust face of the thrust bearing  35 , and the transition ring  39  cooperates with the compressor turbine  7  and the thrust face of the thrust bearing  35 . An oil baffle plate  26  is provided on a lower end of a transition ring  39 , and the lower end of the oil baffle plate  26  is arranged to be inclined towards the oil outlet hole  25 . 
         [0072]    By employing this structural form, lubricating oil  14  enters through an oil inlet hole  13  of the intermediate body  12  and is sent to friction pairs of the floating bearing  37  and the thrust bearing through the lubrication passages  36 , so as to lubricate the friction surfaces while taking away heat generated by rotational friction. The lubricating oil  14  with elevated temperature flows out from an oil outlet hole  25  arranged at a lower portion of the intermediate body  12 . In addition, most of the lubricating oil  14  that flows out from the front thrust bearing  35  will drip on the oil baffle plate  26 , then slip along the oil baffle plate  26  to the oil outlet hole  25  and flow out. 
         [0073]    Thus, as can be seen, by employing this structure, most of the lubricating oil  14  can be introduced into the intermediate body  12  for lubricating and cooling the bearings, and is discharged from the intermediate body  12  by the guiding effect of the oil baffle plate  26 , thus producing the technical effects such as simple structure and easy manufacture and processing. Specifically, the thrust bearing  35  can be further provided with an oil hole aligned with the lubricating oil passage  36  to guide the lubricating oil  24 , so as to achieve a better lubrication effect. Of course, the thrust bearing  35  and the lubrication passage  36  can also be communicated with each other in other specific ways. 
         [0074]    In a further solution, a bearing cover  41  is provided at a front end of the transition ring  39  and in front of the thrust bearing  35 . The bearing cover  41  is axially fixed to the thrust bearing  35  by a retaining ring  33 . A sealing element  34  is provided at contacting areas. An oil throwing plate  40  projecting towards the outside of the transmission shaft  28  is further provided on the transition ring  39  between the sealing element  34  and the oil baffle plate  26 . 
         [0075]    By employing this structure, a part of the lubricating oil  14  after lubricating and cooling the bearings flows towards the transition ring  39  and is blocked by the oil throwing plate  40 , and then is thrown to a side wall of the bearing cover  41  under the action of centrifugal force and flows down, thus forming dynamic seal. When the device is in operation, after a small amount of the lubricating oil  14  immerses the oil throwing plate  40 , it will be sealed by the seal assembly  34  with static seal. In summary, by the oil baffle plate  26 , the oil throwing plate  40  on the transition ring  39  and the seal assembly  34 , it can be ensured that the lubricating oil  14  will not leak out from a side, close to the compressor, of the intermediate body  12 , thus having a good sealing performance. 
         [0076]    Similarly, in order to ensure that the lubricating oil  14  will not leak out from a side, close to the turbine, of the intermediate body  12 , a projecting ring is provided at the rear side of the rear floating bearing  37  of the transmission shaft  28 , and the sealing element  34  is provided at contacting areas between the projecting ring and a side wall of the intermediate body  12 . 
         [0077]    By employing this structure, the lubricating oil  14  that flows out from the floating bearing  37  on the turbine side will directly drip on the side wall of the intermediate body  12  firstly, and then flow towards the oil outlet hole  25 . Even if a small amount of the lubricating oil  14  will infiltrate towards the turbine side along the transmission shaft  28 , it can be thrown to the surrounding by the projecting ring on the transmission shaft  28 , thus preventing the lubricating oil  14  from leaking outwards. When the system is not in operation, a small amount of the lubricating oil  14  infiltrates towards the turbine side along the transmission shaft  28  and will be sealed by the seal assembly  34  with static seal, thus ensuring that the lubricating oil  14  will not leak from the turbine side. 
         [0078]    In another specific embodiment, as shown in  FIG. 10 , the intermediate body  12  has a cavity structure, and two bearing seat holes  55  arranged coaxially are provided in the middle of the intermediate body  12 . A positioning ring  56  for positioning and connecting to the compressor is provided on the front flange  11  of the intermediate body  12 , and a positioning and clamping ring  54  for clamping and positioning relative to the turbine is provided on the rear flange  24  of the intermediate body  12 . The oil inlet hole  13  is provided in the top of the intermediate body  12  at a middle position. Three paths are formed from the oil inlet hole  13 , two of which lead to the two bearing seat holes  55  respectively, and the other of which leads to a hole in which the thrust bearing  35  is mounted. The oil outlet hole  25  is provided in the bottom of the intermediate body  12  at a middle position. Of course, the oil inlet hole  13  and the oil outlet hole  25  are not limited to be provided at the middle position of the intermediate body. The intermediate body  12  is not limited to the above structure, and can also employ other structural forms. 
         [0079]    The present application also provides a solar thermal power generation system, which includes a heat collector and further includes the above thermoelectric conversion device. The thermoelectric conversion device is connected to an output end of the heat collector. 
         [0080]    Because the thermoelectric conversion device has the above technical effects, the solar thermal power generation system including the thermoelectric conversion device also has the corresponding technical effects, which will not be described in detailed herein. 
         [0081]    The solar thermal power generation system and thermoelectric conversion device thereof according to the present application has been described in detail above. The principle and embodiments of the present application are described herein by using specific examples, and the description of the above embodiments is only used to help understanding the method and the core idea of the present application. It should be noted that, those skilled in the art may make various improvements and modifications to the present application without departing from the principle of the present application, and these improvements and modifications should also fall into the protection scopes of the claims of the present application.