Patent Publication Number: US-10787992-B1

Title: Regenerative displacer for use in a stirling engine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a thermodynamic auxiliary instrument and relates particularly to a regenerative displacer for use in a stirling engine. 
     2. Description of the Related Art 
     Stirling engine is a high-efficiency energy conversion instrument that utilizes the principle of heat engine which allows gas to expand and contract in response to a change in temperature to further reciprocate a power piston to generate power. In addition, any form of external heat source can be applied to execute the mechanical equivalent of heat. Thus, type and source of external heat source are not limited. Any energy source can make the stirling engine work as long as a temperature of the energy source is increased to be high enough, and that is especially suitable for use in the present which is confronted by problems of energy shortage and environmental pollution. 
     Stirling engine is usually presented in two ways. One is to use two power pistons to achieve the compression and expansion of working gas and to force the working gas to move back and forth. Another one is to use one power piston to compress and expand working gas and use one displacer to force the working gas to further flow back and forth. The displacer is usually formed with a heat conduction material which is provided by winding a stainless steel wire or a copper wire into an irregular cylindrical shape and placed inside the displacer, so that the heat of the expanded working gas that is increased in a heating portion can be temporarily stored in the heat conduction material when the working gas passes through the displacer into a cooling portion. Hence, the heat which needs to be removed in the cooling portion is reduced. Meanwhile, the working gas can absorb the heat stored in the heat conduction material during the previous cycle when passing the displacer into the heating portion after being cooled and compressed in the cooling portion, whereby the working gas is pre-heated to increase a speed of heating the working gas in the heating portion. Therefore, the efficiency of the heat conduction material affects the entire output efficiency and performance of the stirling engine, and that makes the heat conduction material to be an integral part to the stirling engine. 
     Since the heat conduction material is provided with the irregular winding shape, only a small area of the heat conduction material contacts the working gas and that results in poor efficiency of heat exchange between the working gas and the heat conduction material and causes reduced pressure. Therefore, the displacer cannot be pushed and accelerated smoothly and effectively, and simultaneously affects the motion of the power piston. The start time of the stirling engine is extended. Meanwhile, the energy consumed during the driving process is increased, and the generated power is decreased. If the temperature of the heating portion is increased in order to increase the output power, the cost will be raised and that needs to be improved. 
     SUMMARY OF THE INVENTION 
     The object of this invention is to provide a regenerative displacer for use in a stirling engine capable of providing preferable effect of heat conduction, increasing the efficiency of heat exchange and the efficiency of a regenerator, and increasing a temperature difference of working gas in a thermodynamic cycle to increase pressure for facilitating a quick reciprocation of a power piston and further increase output power greatly. 
     The regenerative displacer for use in a stirling engine of this invention is disclosed. The stirling engine comprises a cylinder and a regenerative displacer disposed therein to divide the cylinder into a heating portion and a cooling portion. An expansion chamber is formed in the heating portion and a compression chamber is formed in the cooling portion. A power piston is disposed apart from the regenerative displacer. The regenerative displacer comprises a body which has a peripheral wall enclosing an accommodation space, a first cover and a second cover respectively engaging two ends of the peripheral wall, a regenerator disposed in the accommodation space, and a rod inserted through the regenerator and the second cover into the cooling portion. Surfaces of the first cover and the second cover are penetrated by a plurality of through openings respectively. The regenerator has a plurality of spaced channels each has two opposite open ends. Each open end communicates with the accommodation space and is covered by a heat collecting net. Thus, working gas sealed in the cylinder can be concentrated at the open ends when passing through the regenerator and can absorb and release heat quickly by an assistance of the heat collecting nets, thereby providing preferable effect of heat conduction, and increasing the efficiency of heat exchange effectively and the efficiency of the regenerator greatly. Further, a temperature difference between a maximum temperature and a minimum temperature of the working gas generated in a thermodynamic cycle is increased, thereby increasing the generated pressure to quickly reciprocate the power piston, and that increases output power greatly. 
     Preferably, each channel is parallel to the rod. 
     Preferably, each channel is inclined to the rod. 
     Preferably, a number of net holes formed on each heat collecting net is between 2 and 3 per square inch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view showing a first preferred embodiment of this invention; 
         FIG. 1A  is an enlarged view showing a partial element of  FIG. 1 ; 
         FIG. 2  is a cross-sectional view showing the regenerative displacer; 
         FIG. 3  is a schematic view showing the regenerative displacer is forced to move toward the cooling portion and synchronously push the power piston; 
         FIG. 4  is a schematic view showing the regenerative displacer is forced by the power piston to move toward the heating portion; and 
         FIG. 5  is a cross-sectional view showing a second preferred embodiment of this invention characterized by the inclined channels. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 3 , a first preferred embodiment of a regenerative displacer  3  for use in a stirling engine  4  is disclosed. The stirling engine  4  comprises a cylinder  41  which is filled with working gas and a regenerative displacer  3  which is loosely fitted in the cylinder  41  so that the regenerative displacer  3  can move in the cylinder  41  easily. The regenerative displacer  3  divides the cylinder  41  into a heating portion  42  where an expansion chamber  421  is surrounded and a cooling portion  43  where a compression chamber  431  is surrounded. A power piston  44  is located in the compression chamber  431  and disposed at a distance from the regenerative displacer  3 . 
     Referring to  FIG. 1  and  FIG. 2 , the regenerative displacer  3  comprises a body  31  which has a peripheral wall  311  by which an accommodation space A is surrounded, a first cover  32  engaging one end of the peripheral wall  311 , a second cover  33  engaging another end of the peripheral wall  311  and opposite to the first cover  32 , a regenerator  34  disposed in the accommodation space A, and a rod  35  penetrating through a slot  341  formed in the regenerator  34  and a bore  331  formed in the second cover  33  into the cooling portion  43  of the stirling engine  4  as shown in  FIG. 3 . A surface of the first cover  32  and a surface of the second cover  33  are respectively formed with a plurality of through openings  36 . Referring to  FIG. 1A  which is the enlarged view of the encircled portion X indicated in  FIG. 1  shows that the regenerator  34  has a plurality of channels  342  spaced from each other. Each channel  342  has two opposite open ends  343 . Each open end  343  communicates with the accommodation space A and is engaged with a heat collecting net  344 . Namely, the heat collecting net  344  is covered at a surface of each open end  343 . In this preferred embodiment, each channel  342  is parallel to the rod  35 . In addition, a number of net holes formed on each heat collecting net  344  is between 2 and 3 per square inch. 
     Referring to  FIG. 2  and  FIG. 3 , in order to start the stirling engine  4 , an external heat source (not shown) is applied to increase a temperature of the heating portion  42 , and synchronously heat the working gas which is sealed in the expansion chamber  421  to allow the working gas to expand and increase its volume. The expanded working gas then moves toward the cooling portion  43  and simultaneously passing through the regenerative displacer  3 , whereby the regenerative displacer  3  is also forced to move toward the cooling portion  43 . When the working gas passes through the through openings  36  of the first cover  32  and the open ends  343  into the channels  342  and then leaves the regenerative displacer  3  into the compression chamber  431  through the open ends  343  and the through openings  36  of the second cover  33 , the open ends  343  assist in concentrating the working gas. Meanwhile, the working gas exchanges heat with the heat collecting net  344  surrounding each open end  343  to allow the heat collecting nets  344  to absorb and store the heat of the working gas effectively, thereby providing the preferable effect of heat conduction and quickly pushing the regenerative displacer  3 . Because the heat collecting nets  344  remove part of the heat of the working gas, it allows the working gas to be cooled rapidly and lowers its volume effectively, and that facilitates the cooling and compression operation of the working gas in the compression chamber  431 . When the working gas flows to the compression chamber  431 , the working gas moves the power piston  44 , and simultaneously activate a crank shaft, a gear wheel or a flywheel (not shown) that connect to the power piston  44  to operate. 
     Referring to  FIG. 2  and  FIG. 4 , after the working gas is cooled and contracted in the compression chamber  431 , namely the volume of the working gas is decreased, the power piston  44  starts to move toward the regenerative displacer  3  and compress the working gas. When the working gas is compressed by the power piston  44  to flow from the compression chamber  431  through the regenerative displacer  3  into the expansion chamber  421 , the working gas gradually passes the through openings  36  of the second cover  33  and the open ends  343  into the channels  342  and flows into the expansion chamber  421  through the open ends  343  and the through openings  36  of the first covers  32 . The working gas then absorbs the heat stored in the heat collecting net  344  which is engaged at each open end  343  in the previous thermodynamic cycle when the working gas passes through the open ends  343 , thereby pre-heating the working gas effectively that facilitates the heating and expansion operation of the working gas in the expansion chamber  421 . Simultaneously, the regenerative displacer  3  is moved by the working gas to further subject the rod  35  which also connects with the crank shaft, the gear wheel or the flywheel to move toward the heating portion  42 . Hence, the repeated thermodynamic cycles allow the power piston  44  and the regenerative displacer  3  to move back and forth stably in the cylinder  41  to execute the quick reciprocation and force the crank shaft, the gear wheel or the flywheel to operate and generate output power. Therefore, the working gas contacts all heat collecting nets  344  uniformly to facilitate the heat collecting nets  344  to collect and store the heat of the working gas to allow the working gas to increase or decrease the temperature and volume quickly, thereby enhancing the heating effect of the heating portion  42  and the cooling effect of the cooling portion  43 . Moreover, the temperature difference between a maximum temperature and a minimum temperature of the working gas in the thermodynamic cycle is increased, thereby greatly increasing the generated pressure to push the regenerative displacer  3  and the power piston  44  quickly, increasing the efficiency of the regenerator  34 , and further increasing the output power. In addition, energy consumption caused when the stirling engine  4  operates is reduced and saved. Furthermore, the structure of the regenerative displacer  3  is very simple, thereby decreasing the cost greatly and reducing the entire volume and weight to achieve lightweight and lower cost. 
     Referring to  FIG. 5  shows a second preferred embodiment of the regenerative displacer  3  for use in the stirling engine  4  of this invention. The correlated elements and the concatenation of elements, the operation and objectives of the second preferred embodiment are the same as those of the first preferred embodiment. This embodiment is characterized in that each channel  342  is formed to be inclined to the rod  35 . Therefore, the inclined disposition increases a length of the channels  342 , thereby increasing the contact time of the channels  342  and the working gas to further increase the effect of heat conduction of the regenerative displacer  3  and increase the efficiency of heat exchange. Thus, the working gas can be pre-heated and pre-cooled through the regenerative displacer  3  quickly. The temperature difference between the maximum temperature and the minimum temperature of the working gas in the thermodynamic cycle is also increased, thereby increasing the generated pressure that can push the regenerative displacer  3  and the power piston  44  quickly and further increase the output power and reduce the energy consumption. 
     To sum up, the regenerative displacer for use in the stirling engine of this invention takes an advantage that the regenerator is formed with the spaced channels each has two open ends which are engaged by the heat collecting nets respectively to concentrate the working gas and allow the working gas to absorb and release heat rapidly, thereby increasing the efficiency of heat exchange. Further, the temperature difference of the working gas is increased in the thermodynamic cycle, thereby generating larger pressure for reciprocating the power piston quickly to generate power, increasing the efficiency of the regenerator, and further increasing the output power greatly. 
     While the embodiments of this invention are shown and described, it is understood that further variations and modifications may be made without departing from the scope of this invention.