This invention is directed generally to turbine engines, and more particularly to systems enabling warm startups of the gas turbine engines without risk of compressor and turbine blade interference with radially outward sealing surfaces.
Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine blade assemblies to these high temperatures. Because of the mass of these large gas turbine engines, the engines take a long time to cool down after shutdown. Many of the components cool at different rates and as a result, interferences develop between various components. The casing component cools at different rates from top to bottom due to natural convection. As a result, the casings cooling faster at the bottom versus the top, and the casings take on a deformed shape during shutdown prior to being fully cooled. The hotter upper surface of the casing versus the cooler bottom surface causes the casing to thermally bend or bow upwards. If the engine undergoes a re-start during the time the casing is distorted, the blade tips will have a tendency to interfere at the bottom location due to the upward bow. Thus, if it is desired to startup the gas turbine before is has completely cooled, there exists a significant risk of damage to the turbine blades due to turbine blade tip rub from the interference between the turbine blade tips and the blade rings at the bottom of the engine due to the deformed shape of the outer casing. Thus, a need exists for reducing turbine vane carrier and blade ring cooling after shutdown.
This invention relates to a turbine engine heating system configured to heat compressor and turbine blade assemblies to eliminate turbine and compressor blade tip rub during warm restarts of the gas turbine engine. The turbine engine heating system may include a heating air extraction system configured to withdraw air from the turbine engine and to pass that air thru a heating element configured to increase a temperature of the air supplied by the heating air extraction system. The air may then be passed to a heating air supply system via an air movement device. The heating air supply system may be in communication with a turbine cylinder cavity of the turbine engine positioned radially outward from at least one turbine assembly. The heated air may be passed into the turbine cylinder cavity to reduce the cooling rate of the turbine vane carriers after shutdown and before a warm restart to limit tip rubbing by heating the turbine vane carrier. Similarly, heated air may be passed via a compressor heating system to the compressor shell cavity to heat compressor vane carrier to prevent the compressor vane carrier from developing an oval cross-section due to material growth because of thermal gradients between the top and midsections of the compressor vane carrier.
The turbine engine with a turbine engine heating system may be configured for controlling turbine vane carrier temperatures after engine shutdown and before a warm restart and may include a heating air extraction system configured to withdraw air from the turbine engine and a heating element configured to increase a temperature of the air supplied by the heating air extraction system. The turbine engine heating system may also include a heating air supply system having an inlet in communication with the heating element and including one or more outlets in communication with a turbine cylinder cavity of the turbine engine positioned radially outward from one or more turbine assemblies.
The outlet of the heating air supply system may be formed from a first outlet positioned within 30 degrees of a first horizontal joint joining first and second sections of a housing forming at least a portion of the turbine cylinder cavity, wherein the first outlet may be positioned on a first side of the housing. A second outlet may be positioned within 30 degrees of a second horizontal joint between the first and second sections of the housing forming at least a portion of the turbine cylinder cavity, wherein the second outlet may be positioned on a second side of the housing. In another embodiment, a third outlet may be positioned on the first side of the housing within 30 degrees of the first horizontal joint and on an opposite side of the first horizontal joint from the first outlet and a fourth outlet positioned on the second side of the housing within 30 degrees of the second horizontal joint and on an opposite side of the second horizontal joint from the second outlet.
The heating air extraction system may be configured to withdraw air from a turbine engine combustor shell of the turbine engine. The heating air extraction system may also include one or more inlets in communication with the turbine engine combustor shell. The inlet may include a bell mouth to minimize the pressure loss.
The turbine engine heating system may also include an air movement device in fluid communication with the heating element. In one embodiment, the air movement device may be, but is not limited to being, a blower. The blower may be positioned upstream of the heating element. The blower may be configured to run at least as high as 2,500 rpm.
The turbine engine heating system may also include a compressor heating system extending from the turbine cylinder cavity and terminating in a compressor air feed supply. In one embodiment, the compressor air feed supply may be a compressor shell cavity. The compressor heating system may also include further comprising a first inlet in communication with the turbine cylinder cavity within 30 degrees of top dead center. The compressor heating system may also include a second inlet in communication with the turbine cylinder cavity within 30 degrees of bottom dead center. In another embodiment, the compressor heating system may include an inlet in communication with the turbine cylinder cavity within 30 degrees of bottom dead center without an inlet at top dead center. The turbine engine heating system may include one or more valves for isolating the heating air extraction system to prevent air from being exchanged with the turbine engine and at least one valve for isolating the heating air supply system from the turbine cylinder cavity of the turbine engine.
An advantage of this invention is that the heated air delivered to the turbine cylinder cavity reduces the rate of cooling of the turbine vane carrier after shutdown, thereby preventing the turbine vane carrier from developing an oval cross-section and creating turbine blade tip rub during a warm startup of the gas turbine engine.
Another advantage of this invention is that the heated air delivered to the compressor shell cavity reduces the rate of cooling of the compressor vane carrier after shutdown, thereby preventing the compressor vane carrier from developing an oval cross-section and creating compressor blade tip rub during a warm startup of the gas turbine engine.
Yet another advantage of this invention is that the turbine engine heating system may be installed in currently existing gas turbine engines, thereby making gas turbine engines that are currently in use more efficient by enabling warm startups to occur rather than waiting days for the gas turbine engines to cool enough for a safe startup.
Another advantage of this invention is that the uniform temperature distribution of heated air by the turbine engine heating system in the turbine cylinder cavity and in the compressor shell cavity overcomes any buoyancy effects from forming, thus preventing ovalization of the annular shaped turbine cylinder cavity and the compressor shell cavity due to vertical temperature gradients.
Still another advantage of this invention is that the uniform cavity air in the turbine cylinder cavity and the compressor shell cavity help to mitigate vertical gradients within the housing forming the turbine cylinder cavity and the compressor shell.
Another advantage of this invention is that injecting heated air at about 350 degrees Celsius into a turbine cylinder cavity causes turbine vane carriers number 1 and 2 to remain thermally expanded, thereby increasing the blade ring diameter in row 1 by about 0.40 mm and in row 2 by about 0.65 mm.
Yet another advantage of this invention is that the turbine engine heating system reduces case bowing by reducing the top to bottom temperature gradient.
Another advantage of this invention is that use of the turbine engine heating system is also beneficial in a cold start up condition of a gas turbine engine, whereby two hours of preheating may increase the cold start pinch point gap by 1 mm and four hours of preheating may increase the cold start pinch point gap by 1.2 mm.
These and other embodiments are described in more detail below.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention.
As shown in
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In yet another embodiment, as shown in
The turbine engine heating system 10, as shown in
The turbine engine heating system 10 may also include a heating element 20 configured to increase a temperature of the air supplied by the heating air extraction system 18. The heating element 20 may be configured to heat air to between 300 degrees Celsius and 500 degrees Celsius. In at least one embodiment, the heating element 20 may be configured to heat air to between 335 degrees Celsius and 365 degrees Celsius. In yet another embodiment, the heating element 20 may be configured to heat air to 350 degrees Celsius.
The turbine engine heating system 10 may also include one or more air movement devices 24 in fluid communication with the heating element 20. In one embodiment, the air movement device 24 may be a blower 68. The blower 68 may be positioned upstream of the heating element 20. The blower 68 may be coupled to the heating element 20 via one or more plenums or other appropriate structure. The blower 68 may be configured to run at least as high as 2,500 revolutions per minute (rpm).
The turbine engine heating system 10 may also include one or more compressor heating systems 70 for heating the compressor blade assembly 12 after shutdown and before a warm restart to eliminate compressor blade tip rub during warm restarts of the gas turbine engine 16. The compressor heating system 70 may extend from the turbine cylinder cavity 26 and may terminate in a compressor air feed supply 72. In at least one embodiment, the compressor air feed supply 72 may be a compressor shell cavity 74. The compressor heating system 70 may also include a first inlet 76 in communication with the turbine cylinder cavity 26 within 30 degrees of top dead center 56, as shown in
The turbine engine heating system 10 may be used most often to eliminate turbine and compressor blade tip rub during warm restarts of the gas turbine engine 16 that can occur at the tip 88 of the turbine blade 90 and the blade ring 92, as shown in
The air may be passed into the turbine cylinder cavity 26 to reduce the rate of cooling. The air may be passed into the turbine cylinder cavity 26 via one or more of outlets 34, 46, 52, 54 of the turbine engine heating system 10. The air may heat the turbine cylinder cavity 26 and heat turbine vane carriers 28, thereby limiting the cooling rate and preventing the turbine vane carrier 28 from developing an oval-shaped cross-section. As least a portion of the air may flow through the blade ring and the remaining heated air may flow into the compressor heating system 70 from the turbine cylinder cavity 26. The air may flow into one or more inlets, such as, but not limited to, first and second inlets 76, 78 of the compressor heating system 70. The air may flow into the compressor shell cavity 74 where the air is used to reduce the rate of cooling of the compressor vane carriers 84.
By slowing the cooling rate of the compressor vane carriers 84 and the turbine vane carriers 28, the housing 42 undergoes less thermal shrinkage. The turbine engine heating system 10 may be typically operated during a turbine engine shutdown sequence when the turbine engine 16 is on turning gear operation and has depressurized.
The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.