Abstract:
A gas turbine, especially an aircraft engine is provided. The gas turbine comprises at least one compressor ( 15, 16 ), at least one combustion chamber ( 17 ), at least one turbine ( 18, 19 ), and at least one generator ( 20 ) for generating electrical energy, each generator ( 20 ) comprising at least one stator ( 25 ) and at least one rotor ( 22 ). Each rotor ( 22 ) of each generator ( 20 ) is embodied as a free-wheeling generator turbine that is driven by a gas flow in such a way that it rotates in relation to the respective stator ( 25 ) of the respective generator ( 20 ) and thus generates electrical energy from the kinetic energy of the gas flow.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a gas turbine, in particular an aircraft engine comprising at least one compressor, at least one combustion chamber, at least one turbine, and at least one generator for generating electrical energy. 
   BACKGROUND 
   In addition to a thrust for propelling the aircraft, aircraft engines—either civil aircraft engines or military aircraft engines—generate power for supplying attachments or auxiliary units of the gas turbine or for supplying aircraft-side systems such as the air conditioning system. The attachments, auxiliary units, or also aircraft-side systems of an aircraft engine may be devices, units, or systems driven hydraulically, pneumatically, or electrically or by an electric motor. 
   A clear trend toward increasing need for electrical power in the aircraft can be noticed in aircraft development. This is based on the fact that hydraulically or pneumatically driven aircraft systems are replaced by systems driven by electric motors and that an ever greater power demand exists per aircraft seat. Therefore, the aircraft engines must provide an ever greater amount of electrical power. Such aircraft engines are also referred to as “more electric engines”, (MEE). 
   For generating electrical power for supplying the attachments or auxiliary units of the gas turbine as well as the aircraft-side systems it is known from the related art to draw mechanical energy from a core engine of the gas turbine which is used for driving pumps and generators, for example. DE 41 31 713 C2 describes an aircraft engine in which shaft energy is drawn from a core engine and this shaft energy is supplied to auxiliary units. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a novel gas turbine, in particular a novel aircraft engine. 
   In an advantageous embodiment of the present invention, the or each rotor of the or each generator is designed as a free-running generator turbine which, driven by a gas flow, rotates relative to the respective stator of the respective generator thereby generating electrical energy from the kinetic energy of the gas flow. This results in a totally novel concept or principle for the configuration of a gas turbine designed as a “more electric engine.” 
   According to an advantageous refinement of the present invention, the gas turbine includes a fan module having at least one fan, the or each generator being positioned downstream from the or each fan in such a way that the or each free-running generator turbine of the or each generator is driven by a gas flow of the or each fan. The or each generator generates electrical energy from a bypass gas flow of the fan module. The or each generator is preferably integrated into a generator module, the generator module being detachably connected to the fan module at the downstream end of a fan flow channel. 
   According to an alternative advantageous refinement of the present invention, the or each generator is positioned downstream from a low-pressure turbine of the gas turbine, kinetic energy of the gas flow exiting the low-pressure turbine being converted into electrical energy. It is also possible to position a generator downstream from the fan module and an additional generator downstream from the low-pressure turbine of the gas turbine whereby kinetic energy of the bypass gas flow exiting the fan module and kinetic energy of the gas flow exiting the low-pressure turbine is converted into electrical energy. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Without being restricted thereto, exemplary embodiments of the present invention are explained in greater detail based on the drawing. 
       FIG. 1  shows a schematic representation of a gas turbine according to the present invention. 
       FIG. 2  shows an alternate embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   The present invention is described in greater detail in the following with reference to  FIG. 1 . 
     FIG. 1  shows a gas turbine  10  designed as an aircraft engine in a partial sectional perspective side view. Gas turbine  10  of  FIG. 1  has a fan module  11  including a rotating fan  12 , fan  12  being enclosed by housing  13  of fan module  11 . A fan flow channel  14  is adjacent downstream from fan  12 . Fan  12  acts as a low-pressure compressor; a medium-pressure compressor  15 , a high-pressure compressor  16 , a combustion chamber  17 , a high-pressure turbine  18 , and a low-pressure turbine  19  are adjacent downstream from fan  12 . Medium-pressured compressor  15 , high-pressure compressor  16 , combustion chamber  17 , high-pressure turbine  18 , and low-pressure turbine  19  together form the core engine of gas turbine  10 . One part of the gas flow generated by fan  12  which acts as a low pressure compressor reaches the core engine and another part reaches fan flow channel  14 . The portion of the gas flow generated by fan  12  and reaching fan flow channel  14  is referred to as a bypass gas flow. 
   Within the scope of the present invention at least one generator is assigned to the gas turbine for generating electrical power, one rotor of each generator being designed as a free-running generator turbine, and the rotor, driven by a gas flow, rotating relative to a stator of the respective generator, thereby generating electrical energy from the kinetic energy of the gas flow. 
   In the preferred exemplary embodiment of  FIG. 1 , a generator  20  is assigned to gas turbine  10 , generator  20  being integrated into a generator module  26  and the generator module  26  being positioned at the downstream end  21  of fan module  11  or fan flow channel  14 . In the preferred exemplary embodiment of  FIG. 1 , a rotor  22  of generator  20  designed as a free-running generator turbine is thus driven by the bypass gas flow of fan module  11 , and generator  20  generates electrical energy from the kinetic energy of the bypass gas flow of fan module  11 . As is apparent in  FIG. 1 , rotor  22  of generator  20  has multiple rotating blades  23 , pole pieces  24  being assigned to radially outlying ends of blades  23 . Rotor  22  of generator  20 , which is formed by blades  23  and pole pieces  24 , is enclosed radially outside by a stator  25  of generator  20 , stator  25  having windings and magnetic circuits for generating electrical energy. 
   At the radially inside end, blades  23  of rotor  22  are mounted on an outer rotating bearing ring  27  of a pivot bearing. Like the entire generator module  26 , the bearing is thus positioned downstream from fan module  11  and operates therefore in a relatively cold and a relatively clean environment. 
   In the preferred exemplary embodiment of the present invention, generator module  26  having generator  20  is detachably connected to fan module  11 . An outside diameter of generator module  26  is adapted to the outside diameter of fan module  11  in such a way that generator module  26  does not radially protrude with respect to fan module  11 . Generator module  26  may be connected to fan module  11  using a plurality of fastening means, in particular locking bolts or V-clamps. The detachable connection of generator module  26  to fan module  11  ensures that generator module  26  may be disassembled from fan module  11  in a simple manner for maintenance work. 
   In the exemplary embodiment of  FIG. 1 , generator  20  of generator module  26  has a single-stage design, i.e., it has one rotor  22  with multiple blades  23  assigned to rotor  22 . However, within the scope of the present invention, a generator may also be used which includes multiple rotors, including rotor  122 , designed as free-running generator turbines and which has thus a multi-stage design. The multiple rotors designed as free-running generator turbines may rotate either in the same direction or in opposite directions. 
   As mentioned above, rotor  22  of generator  20  has multiple blades  23  rotating with rotor  22 . Rotor  22  has a smaller number of blades than fan  12  of fan module  11 . This results in rotor  22  of generator  20  being largely insensitive to bird strikes or hail. 
   In the simplest form of generator  20 , blades  23  of rotating rotor  22  are designed to be stationary, which means that the bypass gas flow of fan module  11  flows against blades  23  always at the same angle of incidence. However, it is also possible within the scope of the present invention to design blades  23  of rotor  22  to be adjustable. This makes it possible to adjust the angle of incidence of blades  23  in such a way that the output energy of generator  20  is adapted to the operating conditions of gas turbine  10 , thereby making it possible to extract an optimum amount of energy from the bypass gas flow of fan module  11  and to generate a higher amount of electrical energy. The efficiency of generator  20  may thus be increased. 
   The design of gas turbine  10  according to the present invention described in connection with  FIG. 1  has the advantage that, for generating electrical energy with the aid of generator  20 , the configuration of gas turbine  10 , in particular the configuration of a core engine of gas turbine  10 , does not have to be modified. The design principles for generating electrical energy in a gas turbine, known from the related art, all have in common that shaft energy is drawn from the core engine of the gas turbine. The present invention abandons this principle and proposes a gas turbine  10  having generator  20  which generates electrical energy from a gas flow, from the bypass gas flow of fan module  11  in particular. This has the advantage that generator  20  operates in a relatively clean and relatively cold environment. Generator  20  virtually does not have to be cooled. Moreover, no design modifications to the core engine of the gas turbine are necessary. 
   In contrast to the exemplary embodiment shown it is possible of course to assign the pole pieces of rotor  22  to the radially inside ends of blades  23 . In this case, the stator of the generator would not be positioned radially outside with respect to rotor  22 , but rather radially inside. In this case, the rotor would thus enclose the stator of the generator radially on the outside. 
   It should be pointed out here that generator  20  of the exemplary embodiment in  FIG. 1  may also be used in motor mode. This may be useful, for example, when an aircraft having such gas turbines is in a parked position and rotation of fan  12  due to the effects of wind is to be prevented. It is furthermore possible, when generator  20  is driven in the motor mode, to generate a negative pressure at the outlet of fan  12  in order to enable a more effective acceleration of fan  12 . 
   In contrast to the exemplary embodiment shown in  FIG. 1 , it is also possible to position a generator, which has a rotor designed as a free-running generator turbine, downstream from low pressure turbine  19 . In this case, the rotor would be driven from the gas flow exiting low pressure turbine  19  and electrical energy would then be generated from the kinetic energy of the gas flow exiting low pressure turbine  19 . In this case, the generator would only have to be designed for use in higher temperature ranges. 
   It is likewise possible to position a first generator downstream from fan module  11  and an additional generator  30  downstream from low pressure turbine  19 . In this case, electrical energy would be generated from both the kinetic energy of the bypass gas flow of fan modula  11  as well as from the kinetic energy of the gas flow exiting low pressure turbine  19 . 
   However, the system shown in  FIG. 1  is preferred in which generator  20  is positioned downstream from fan module  11  and is integrated into a generator module  26  designed as a separate assembly, generator module  26  being detachably connected to fan module  11 . Using such a generator, it is possible to generate several hundred kilowatts of electrical energy during normal operation of gas turbine  10 . During what is known as “engine windmilling”, generator  20  is able to generate electrical emergency energy of approximately 30 kW. 
   The principle according to the present invention for providing a “more electric engine”, may be used in a plurality of aircraft engines, e.g., in turboprop engines, in aircraft engines having a high bypass gas flow of the fan module which is typical in civil aircraft engines, in aircraft engines having a low bypass gas flow which is typical in military aircraft engines, or also in engines which are used in helicopters.