Turbogenerator with cooling system

[0001] 1. Field of the Invention

[0002] The present invention relates to gas turbine engine powered generators or turbogenerators and cooling and thermal management systems.

[0003] 2. Description of Related Art

[0004] Directed energy weapons (DEW) require megawatts (in a range of between 1-5 megawatts or more) of fast (e.g. less than 0.1 sec) on/off pulsing power. They also require megawatts of heat removal that can be provided by gas turbines driving electrical generators, also referred to as turbogenerators. Turbogenerators, such as independent APU power sources to meet the power requirement, can provide enough power but are slow (on the order of 4 sec). Batteries and complicated power electronics are often used to meet the transient power requirements. These systems typically require large RAM air heat exchangers for thermal management of the large heat loads generated by the DEW.

[0005] Directed energy weapons are representative of very high power devices in high energy systems that are being studied and developed for a variety of applications. One area of high energy systems under very active development is directed energy controlled effects, also referred to as Directed Energy Weapons (DEW). Sea based, ground, and DEW systems are being developed to provide missile defense as well as other defense related capabilities. DEW include microwave energy to disrupt enemy electronics, laser energy to damage or destroy targets and particle beam energy to damage or destroy targets.

[0006] It is highly desirable to provide a fast switching thermal management system within a single integrated turbogenerator package for high energy devices such as directed energy weapons using large amounts of electrical power in a range of between 1-5 megawatts or more.

[0007] A turbogenerator includes a gas turbine engine operable to power a generator, a cooling system including an annular heat exchanger disposed entirely across an annular outer fan duct of the gas turbine engine and powered by a fan in the gas turbine engine. Variable inlet guide vanes may be disposed within the outer fan duct just upstream of the fan and variable outlet guide vanes may be disposed within the outer fan duct just downstream of the fan. A low pressure turbine and the generator may be drivingly connected to the fan by a low pressure turbine shaft with a core engine operably disposed between the fan and the low pressure turbine.

[0008] Inner and outer portions of the fan separated by a rotating shroud may be disposed in the annular inner and outer fan ducts respectively upstream of the core engine. A surface heat exchanger may be disposed in a bypass duct extending axially and downstream from the outer fan duct. The surface heat exchanger may be operably connected to the generator for cooling the generator.

[0009] A high energy system including a power consuming device may incorporate the turbogenerator for powering the power consuming device and the cooling system for cooling the power consuming device. The cooling system may include a refrigeration apparatus operably disposed between the annular heat exchanger and the power consuming device for cooling the power consuming device and the refrigeration apparatus may include a vapor cycle cooling system and a cold storage containing a phase change material.

[0010] The high energy system may be a directed energy weapon system with the power consuming device being a directed energy weapon. Conditioning power electronics operably disposed between the generator and the directed energy weapon conditioning the electricity produced by the electrical generator and supplied to the directed energy weapon. The cooling system is operably connected to the directed energy weapon and the conditioning power electronics for cooling the directed energy weapon and the conditioning power electronics.

[0013] FIG. 1 illustrates an exemplary high energy system 8 in the form of a directed energy weapon system 10 including a directed energy weapon 12 (DEW) powered by an electrical generator 14 in a turbogenerator 16. The turbogenerator 16 includes a gas turbine engine 30 operable to power the generator 14 and a cooling system 20 for cooling the directed energy weapon system 10. The directed energy weapon system 10 further includes conditioning power electronics 68 operably disposed between the generator 14 and the directed energy weapon 12 for conditioning the electricity produced by the electrical generator 14 for operating and firing the directed energy weapon 12. The gas turbine engine 30 is operable to switch between exclusively powering the generator 14 and exclusively powering the cooling system 20 or powering both simultaneously.

[0014] A fan 32 upstream of a core engine 34, also referred to as a gas generator, is drivenly connected to a low pressure turbine 36 that supplies power to the fan 32 through a low pressure turbine shaft 38 concentrically mounted with respect to the core engine 34. The core engine 34 is operably disposed between the fan 32 and the low pressure turbine 36 and is axially located downstream of the fan 32. The generator 14 is also drivenly connected to the low pressure turbine 36 by the low pressure turbine shaft 38.

[0015] The directed energy weapon system 10 including the directed energy weapon 12 and the conditioning power electronics 68 requires megawatts of fast (e.g. less than 0.1 sec) on/off pulsing power that is produced by the electrical generator 14. The directed energy weapon 12 and the conditioning power electronics 68 also require megawatts of heat removal which is provided by the cooling system 20. The turbogenerator and cooling system may be used to power and cool other types of large power consuming devices 13 besides directed energy weapons 12.

[0016] In order to provide for additional control of the engine's airflow and thereby help increase the engine's efficiency downstream of a fan inlet 44, the fan 32 is split into an outer portion 50 and inner portion 52. The inner and outer portions 52, 50 of the fan 32 are disposed in annular inner and outer fan ducts 53, 55 respectively and separated by a rotating shroud 54. The inner portion 52 supercharges the core engine 34 with a compressed airflow that is separated by the shroud 54 from being affected by the airflow past the outer portion 50. This separation allows core engine supercharging and inlet flow conditions to be relatively independent of the position of fan variable inlet guide vanes 46 disposed within the outer fan duct 55. An inner variable inlet guide vane 76 axially ahead and upstream of the inner portion 52 is provided to assist in matching the airflow characteristics of the inner portion 52 with the airflow requirements of the core engine 34.

[0017] The variable inlet guide vanes 46 are disposed within the outer fan duct 55 downstream of the fan inlet 44 and just upstream of the fan 32. The exemplary embodiment of the gas turbine engine 30 illustrated herein further includes variable outlet guide vanes 48 disposed within the outer fan duct 55 just downstream of the fan 32. The basic characteristics of variable inlet and outlet guide vanes 46, 48 are known to those skilled in the art, and it is known that vanes can be rotated to different positions to control the volume of inlet airflow into the fan 32. A bleed valve 56 is provided between an engine bypass duct 58 and a core engine inlet 60 to the core engine 34 radially located inwardly of the bypass duct 58. The bypass duct 58 extends axially and downstream from the outer fan duct 55 to an engine exhaust nozzle 72. By incorporating this bleed valve 56, an outlet is provided to permit redirection of excess air supercharged by the fan inner portion 52 when it is not required by the core engine 34. It is expected that bleeding of fan airflow would be required only at part power engine settings when fan speed is held at maximum levels.

[0018] The inlet guide vanes 46 are part span inlet guide vanes, meaning the vanes physically extend into the engine's bypass stream region only. The inlet guide vanes' 46 angular position will tend to affect the fan outer portion airflow only. The airflow that flows radially inwardly of the inlet guide vanes 46 is then relatively unaffected by vane position. The use of these part span inlet guide vanes 46 is useful for maintaining reasonable airflow conditions entering the core engine 34 over the entire range of inlet guide vane angles. The shroud 54 tends to further promote this airflow separation which generally increases the engine performance at inlet guide vane closures.

[0019] A fan powered DEW annular heat exchanger 57 is disposed entirely across the outer fan duct 55 upstream of the variable inlet guide vanes 46. The exemplary embodiment of the fan powered DEW annular heat exchanger 57 illustrated herein is annular and extends radially completely across the outer fan duct 55. The exemplary directed energy weapon system 10 illustrated herein further includes a vapor cycle cooling system 61 for cooling the directed energy weapon 12. The vapor cycle cooling system 61 is essentially a refrigeration apparatus 62 that may include a cold storage 64 containing a phase change material such as paraffin. The exemplary embodiment of the cooling system 20 illustrated herein further includes a surface heat exchanger 66 disposed in the bypass duct 58 downstream of the fan powered DEW annular heat exchanger 57. The surface heat exchanger 66 is operably connected to the generator 14 for cooling the generator. The surface heat exchanger 66 is disposed along or in a nacelle or radially outer wall circumscribing the bypass duct 58 and preferably downstream of the fan 32.

[0020] The VGVs allow switching between shaft horsepower to power the electrical generator 14 for the DEW and cooling flow for the DEW annular heat exchanger 57 used to cool the DEW. The directed energy weapon system 10 allows cycling between power and cooling flow at 100% of the gas turbine engine's speed and load. This eliminates a transient problem of ramping up the gas turbine engine 30 from a low to high power level in a very short period of time, typically, about 0.1 sec.

[0021] When the gas turbine engine 30 is operating to power the electrical generator 14 which in turn is powering the directed energy weapon 12 during firing of the directed energy weapon 12, the inlet guide vanes 46 can be rotated to a “closed” position to reduce the inlet airflow and, thereby, reduce the load on the fan 32 with the fan still rotating. This permits a majority of the mechanical power from the gas turbine engine 30 to be transferred to the generator 14 through the low pressure turbine shaft 38 instead of to the fan 32.

[0022] When the gas turbine engine 30 is not powering the electrical generator 14, the inlet guide vanes 46 are rotated to an “open” position increasing the inlet airflow and primarily cooling the directed energy weapon system 10 through the vapor cycle cooling system 61 and the cold storage 64 by cooling and solidifying the phase change material therein. The cold storage 64 is used as a heat sink to cool the electrical generator 14 during its operation when the electrical generator 14 is primarily powering the directed energy weapon 12.

[0023] This permits the gas turbine engine 30 to be constantly running at or near operating conditions for the firing of the directed energy weapon system 10. The power produced by the gas turbine engine 30 can very quickly be switched between shaft horsepower to power the electrical generator 14 for firing the DEW and the fan 32 to produce cooling flow for the DEW annular heat exchanger 57 used to cool and solidify the phase change material in the cold storage 64 making it available to be used as a heat sink to cool the electrical generator 14 during the operation and firing of the DEW.

[0024] The cooling system 20 and more particularly the fan powered DEW annular heat exchanger 57 is used for cooling the directed energy weapon system 10 and more particularly to cool the directed energy weapon 12 and the power electronics 68. The turbogenerator and cooling system 20 is useful for providing a fast switching thermal management system within a single integrated turbogenerator package for high energy devices such as directed energy weapons 12 using large amounts of electrical power in a range of between 1-5 megawatts or more.

[0025] The present invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. While there have been described herein, what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein and, it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention.

[0026] Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims: