Patent Publication Number: US-2021172603-A1

Title: Microturbine and Combustor thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a microturbine and a combustor, and more particularly, to a microturbine and a combustor to be cooled efficiently with low cost. 
     2. Description of the Prior Art 
     Typically, fuel is injected into a combustor of a microturbine, and the air and fuel are mixed upon burning in a flame zone. To ensure even temperature distribution and low temperature on the exhaust orifice of the combustor, dilution holes are drilled at the front end of the combustor. Nevertheless, improper control of intake air volume and gas volume of the combustor may cause local high temperature areas, which discolors the combustor and shortens the service life of the combustor. Moreover, drilling may be expensive. Therefore, a more cost efficient cooling approach is needed. 
     SUMMARY OF THE INVENTION 
     Therefore, the present application primarily provides a microturbine and a combustor to be cooled efficiently with low cost. 
     An embodiment of the present application discloses a microturbine including a combustor, an igniter disposed adjacent to the combustor, and a plurality of fuel nozzles disposed adjacent to the combustor. The combustor includes a plurality of laser holes located merely in a region of the combustor. 
     Another embodiment of the present application discloses a combustor including a plurality of laser holes located merely in a region of the combustor. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram illustrating a top view of a microturbine according to an embodiment of the present invention. 
         FIG. 1B  is a schematic diagram illustrating a side view of the microturbine shown in  FIG. 1A . 
         FIG. 1C  is a schematic diagram of the microturbine shown in  FIG. 1A . 
         FIG. 2  is a schematic diagram illustrating simulation results of a combustor. 
         FIG. 3  is a schematic diagram illustrating experimental results of a combustor. 
         FIG. 4  is a schematic diagram illustrating a locally enlarged view of the microturbine shown in  FIG. 1 . 
         FIG. 5  is a cross-sectional view diagram along a cross-sectional line A-A′ of the microturbine shown in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 1A  to  FIG. 1D .  FIG. 1A  is a schematic diagram illustrating a top view of a microturbine  10  according to an embodiment of the present invention.  FIG. 1B  is a schematic diagram illustrating a side view of the microturbine  10  shown in  FIG. 1A .  FIG. 1C  is a schematic diagram of the microturbine  10  shown in  FIG. 1A . The microturbine  10  may be a turbine engine and is configured to burn various fuels such as methane, propane, biogas, wood gas and other biofuels. The microturbine  10  includes an igniter  100 , a plurality of fuel nozzles  110  and a combustor  120 . The igniter  100  is disposed adjacent to the combustor  120 . The combustor  120  have a plurality of fuel nozzle orifices  122  to connect to the fuel nozzles  110  disposed adjacent to the combustor  120 , a plurality of laser holes  126  for heat dissipation, and a plurality of dilution holes  124 . Each of the fuel nozzles  110  is disposed corresponding to one fuel nozzle orifice  122 . 
     Briefly, with the laser holes  126 , a film of cooling air is developed along the surface of the combustor  120  and closely apposed on the surface of the combustor  120  so as to dissipate heat into the surrounding, thereby protecting the combustor  120  and extending the service life of the combustor  120 . Moreover, the laser holes  126  are located in a high temperature region of the combustor  120  for cost reduction. 
     Specifically, when the microturbine  10  burns different fuel to generate electricity, high temperature discoloration area may be formed on the combustor  120  because fuel gas and (engine intake) air are mixed unevenly. Using the laser drilling technology to form the laser holes  126  on the combustor  120  (especially on the potential high temperature discoloration area of the combustor  120 ), high pressure cold air outside the combustor  120  may enter the combustor  120  through the laser holes  126  to create a film of cooling air along the inner wall of the combustor  120 . The film of cooling air may isolate hot fuel gas in the combustor  120  to produce a film air cooling effect. This lowers temperature of the combustor  120  and protects the surface of the combustor  120  to increase its service life. Furthermore, the length of the combustor  120  may become shorter as heat dissipation efficiency is enhanced. Accordingly, in some embodiments, the laser holes  126  for heat dissipation are disposed on the surface of the combustor  120 , such that a film of cooling air may be developed along the inner wall of the combustor  120  and closely apposed on the inner wall of the combustor  120 . 
     In some embodiments, there may be numerous laser holes  126  drilled on all the surface of the combustor  120 . However, the more the laser holes  126 , the higher the manufacturing cost. In addition, the difficulty of laser drilling technology for the combustor  120  may increase. Accordingly, in some embodiments, because forming the laser holes  126  may incur considerable expense, the laser holes  126  are limited in a region to reduce cost. In some embodiments, the laser holes  126  are locally distributed. In some embodiments, the laser holes  126  are located merely in a high temperature region (especially a potential thermal deformation area or the potential high temperature discoloration area) of the combustor  120  for cost reduction as well as heat dissipation. That is to say, a temperature of the (high temperature) region is higher than a front end or a back end of the combustor  120 . In some embodiments, it is not necessary to form the laser holes  126  in non-discoloration area. Obviously, without drilling the laser holes  126  on all the surface of the combustor  120 , the microturbine  10  ensures low manufacturing cost. Locally distribution of the laser holes  126  may be applied to various microturbine combustors and turbine engine combustors. 
     In some embodiments, the laser holes  126  may be disposed adjacent to the fuel nozzle orifices  122 . In some embodiments, the fuel nozzle orifices  122  may be distributed in an array formed by the laser holes  126 . Please refer to  FIG. 2 .  FIG. 2  is a schematic diagram illustrating simulation results of a combustor. According to flow field analysis, the maximum temperature of high temperature gas in the combustor may be 2150° C., and the temperature of high pressure air outside the combustor may be 170° C. The temperature difference between the inside and the outside of the combustor is large. The temperature distribution, thermal stress and thermal deformation of the combustor may be further calculated by fluid solid coupling. Additionally, the flow rate of cold air outside the combustor is almost double the flow rate of hot air inside the combustor. As shown in  FIG. 2 , temperature near the fuel nozzle orifices is below 1412° C. In other words, a high temperature region of temperature about 1250° C., which exceeds the melting point of a combustor, is located near the fuel nozzle orifices  122 . An area near the fuel nozzle orifices or between any two fuel nozzle orifices may be a potential thermal deformation area or a potential high temperature discoloration area of a combustor. Therefore, in some embodiments, the laser holes  126  may be disposed in the potential thermal deformation area or the potential high temperature discoloration area and thus adjacent to the fuel nozzle orifices  122 . In this manner, a film of cooling air may developed near the potential thermal deformation area or the potential high temperature discoloration area, such that the temperature may be lowered by 200° C. in the potential thermal deformation area or the potential high temperature discoloration area. 
     Similarly, please refer to  FIG. 3 .  FIG. 3  is a schematic diagram illustrating experimental results of a combustor. According to  FIG. 3 , there is discoloration and deformation near the fuel nozzle orifices after low temperature combustion of a combustor. It is indicated that temperature of a combustor is high near the fuel nozzle orifices. An area near the fuel nozzle orifices  122  or between any two fuel nozzle orifices  122  may be a potential thermal deformation area or a potential high temperature discoloration area of a combustor. Therefore, in some embodiments, the laser holes  126  may be disposed in potential thermal deformation area or the potential high temperature discoloration area and thus adjacent to the fuel nozzle orifices  122 . 
     Furthermore, as shown in  FIG. 1 , the laser holes  126  are arranged in an array. In other words, the laser holes  126  may be divided into different laser hole groups. The laser holes  126  in each laser hole group are aligned in one circle and surround the combustor  120 . In some embodiments, there are eight laser hole groups. In some embodiments, (centers of) the laser holes  126  are aligned in eight circles respectively. In some embodiments, for heat dissipation, there are five laser hole groups disposed between the fuel nozzle orifices  122  and the back end of the combustor  120 . The laser holes  126  of the five laser hole groups are aligned in five circles respectively. In some embodiments, for heat dissipation, there are three laser hole groups disposed between the fuel nozzle orifices  122  and the dilution holes  124 . The laser holes  126  of the three laser hole groups are aligned in three circles respectively. In some embodiments, there is no need to add laser holes  126  in other area of the combustor  120 , thereby greatly reducing the manufacturing cost. In some embodiments, the number or the density of the laser holes  126  is related to the (surface) temperature of the combustor  120 . In some embodiments, the number or the density of the laser holes  126  is increased as the temperature of the surface of the combustor  120  increases. 
     In addition, please refer to  FIG. 4  and  FIG. 5 .  FIG. 4  is a schematic diagram illustrating a locally enlarged view of the microturbine  10  shown in  FIG. 1 .  FIG. 5  is a cross-sectional view diagram along a cross-sectional line A-A′ of the microturbine  10  shown in  FIG. 4 . In some embodiments, a diameter DD of the laser hole  126  shown in  FIG. 4  may be substantially 0.015 inches to 0.03 inches, but not limited thereto. In some embodiments, an angle NGL of the laser hole  126  shown in  FIG. 5  may be substantially in a range of 45 degrees to 90 degrees, but not limited thereto. In some embodiments, the angle NGL of the laser hole  126  may be substantially 60 degrees accordingly to heat dissipation efficiency, hot cold flow rate ratio, and a group spacing ratio of a spacing SS to the diameter DD. The heat dissipation efficiency is calculated according to FF=(Thot-Twall)/(Thot-Tcold), where FF is the heat dissipation efficiency, Thot is the temperature of hot air, Twall is the temperature of the wall of the combustor  120 , and Tcold is the temperature of cold air. The hot cold flow rate ratio is calculated according to RR=(Dcold*Vcold)/(Dhot*Vhot), where RR is the hot cold flow rate ratio, Dcold and Vcold are the density and the air velocity of cold air, Dhot and Vhot are the density and the air velocity of hot air. In some embodiments, the hot cold flow rate ratio may be substantially 2, but not limited thereto. 
     In some embodiments, the group spacing ratio of the spacing SS to the diameter DD may be substantially in a range of 20:1 to 40:1, but not limited thereto. In some embodiments, the laser hole groups may include a first laser hole group  126 G 1  and a second laser hole group  126 G 2 , and (the laser holes  126  in) the first laser hole group  126 G 1  are adjacent to (the laser holes  126  in) the second laser hole group  126 G 2 . In some embodiments, the laser holes  126  (also referred to as first laser holes) in the first laser hole group  126 G 1  and the laser holes  126  (also referred to as second laser holes) in the second laser hole group  126 G 2  are spaced apart by the spacing SS. In some embodiments, any two adjacent laser hole groups (for instance, the first laser hole group  126 G 1  and the second laser hole group  126 G 2 ) are spaced apart by the spacing SS shown in  FIG. 4 . In some embodiments, the group spacing ratio of the spacing SS to the diameter DD may be substantially 30:1. In some embodiments, when the angle NGL is 60 degrees, the hot cold flow rate ratio is 2, and the group spacing ratio is 30:1, the temperature of the wall of the combustor  120  may be lowered by 1000° C. 
     In some embodiments, the pitch ratio of a pitch PP to the diameter DD may be substantially in a range of 4:1 to 12:1, but not limited thereto. (The centers of) two laser holes  126  adjacent to each other in a laser hole group are spaced apart by the pitch PP shown in  FIG. 4 . In some embodiments, the temperature of the wall of the combustor  120  is evener when the pitch ratio is smaller. However, smaller pitch ratio means more laser holes  126  disposed on the combustor  120 , which increases the manufacturing cost. To decrease the pitch ratio without adding more laser holes  126 , a misaligned hole design is adopted, and the pitch PP may increase to make the pitch ratio of the pitch PP to the diameter DD equal to 8:1. As shown in  FIG. 4 , the laser holes  126  are alternately arranged or distributed to realize the misaligned hole design. That is to say, the laser holes  126  (also referred to as first laser holes) in the first laser hole group  126 G 1  are misaligned to the laser holes  126  (also referred to as second laser holes) in the second laser hole group  126 G 2 . In some embodiments, the laser holes  126  in one laser hole groups (for instance, the first laser hole group  126 G 1 ) are misaligned to the laser holes  126  in another adjacent laser hole group (for instance, the second laser hole group  126 G 2 ). A center of each laser hole  126  in the first laser hole group  126 G 1  is aligned to none of the centers of the laser holes  126  in the second laser hole group  126 G 2 . 
     In some embodiments, the laser holes  126  may be formed on the combustor  120  by the laser drilling technology. Specifically, the combustor  120  is operated under high temperature and faces high temperature flow field first. Besides, the combustor  120  may have a large volume. Furthermore, the combustor  120  should be used for and applicable to different fuels. However, flow or heating value of different fuels, especially fuels such as biofuels and domestic garbage, varies with the composition of the fuels. And multi fuel combustion may impact the temperature of the wall of the combustor  120  dramatically. The temperature control of the combustor  120  is thus difficult (or difficult to be accurate), and the unevenness of temperature may reduce the service life of the combustor  120  significantly. In such a situation, the laser holes  126  are drilled with the laser drilling technology. In the laser drilling technology, small spots are generated by the laser on the high temperature region of the combustor  120 . A light beam is moved in a circular range to form the laser holes  126 . The laser holes  126  may be formed at low speed but the shape of the laser holes  126  is perfect. After drilling, high pressure cold air outside the combustor  120  may enter the combustor  120  through the laser holes  126  to create a film of cooling air along the inner wall of the combustor  120 , thereby achieving the film air cooling effect. This lowers temperature of the combustor  120  and thus extends its service life. 
     In summary, with the laser holes  126  formed on the combustor  120  of the present invention, a film of cooling air is developed along the surface of the combustor  120  and closely apposed on the surface of the combustor  120  so as to dissipate heat into the surrounding, thereby protecting the combustor  120  and extending the service life of the combustor  120 . Moreover, the laser holes  126  are located in a high temperature region of the combustor  120  for cost reduction. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.