The present invention relates generally to gas turbine engines and more particularly to an inlet air heating system of the engine and method of operating the same.
Gas turbine engines are known, and typically include an inlet through which air passes to a compressor section. The air is compressed in the compressor section and passed downstream into a combustion section. In the combustion section, air is mixed with fuel and burned. Products of this combustion pass downstream across turbine rotors, to drive the rotors. A good deal of control is included in modern gas turbine engines.
One recent advancement in gas turbine engines is the so-called dry low NOx or “DLN” combustion systems. These are often utilized in industrial gas turbine engines to achieve very low levels of NOx emissions, without any need for water injection. These engines typically have a very narrow operating range over which emissions are kept low.
One way to increase the operating range is a concept known as inlet bleed heat. Inlet bleed heat involves bleeding off compressor discharge air and injecting it into the inlet air passing into the gas turbine engine. This heat increases inlet air temperature and reduces the power provided by the gas turbine engine. The use of the bleed air reduces the power in that as the inlet temperature increases, the provided power decreases. Unfortunately, bleeding off compressor discharge air reduces engine efficiency.
A gas turbine engine has an inlet for delivering air into a compressor section. The compressor section is connected to feed air into a combustion section, where the air mixes with fuel and combusts. The combustion section is connected to turbine rotors such that products of combustion can pass over the turbine rotors to drive the turbine rotors. An exhaust communicates with the turbine sections to receive the products of combustion. A bleed tap communicates the exhaust to the inlet. A control controls the amount of exhaust gasses tapped into the inlet to achieve desired operating conditions without a loss in engine efficiency. Also, an inventive method and a system for reducing the power from a gas turbine engine are claimed.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A gas turbine engine 20 is illustrated in
The amount of gas bled into the inlet 22 is controlled to achieve a desired amount of power to be delivered from the turbine sections 28 and 30. As shown schematically in
In some applications, if the pressure difference between the exhaust 32 and the inlet 22 is sufficient, blower 36 may not be necessary. As an example, if a heat recovery steam boiler is included, the pressure difference might be sufficient. Instead, a simple damper 42, as shown schematically in
Notably, the exhaust gasses may have corrosive materials produced when burning fuel. Thus, with this system bleeding air from the exhaust through the lines 34, 38, the material and coatings of the turbine sections 28 and 30, and even perhaps the compressor sections 24 and 26, should be selected to resist any potential corrosion issues.
By recirculating gas from the exhaust 32 to the inlet 22, the temperature of the inlet air can be increased, and the oxygen content reduced. Reducing the oxygen content may further reduce NOx emissions.
A worker of ordinary skill in this art would recognize how much air to deliver from the exhaust 32 to the inlet 22 dependent upon the relative temperatures at the two locations preferably measured by sensor 39 and sensor 41, respectively. Sensors 39, 41 send signals to a control 43 for the blower motor 36, or the damper motor 44. Control 43 can be any appropriate processor. Dependent on the desired temperature, and operating temperature, the air delivered to the compressor 24 can be between zero and twenty percent exhaust gas.
Also, the tap lines 34 and 38, along with the blower motor 36, or damper 42, can be connected to existing gas turbine engines.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.