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Gas turbine system with variable guide vane and optimized reliable sealing air operation Disclosure Number: IPCOM000168855D
Publication Date: 2008-Mar-31
Document File: 3 page(s) / 122K

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For an optimized sealing air operation in a gas turbine with variable guide vane operation, the gas turbine system comprises a minimum flow orifice and a pressure regulator, optionally a heat exchanger. The minimum flow orifice and the pressure regulator are arranged in parallel ensuring a guaranteed minimum flow. An orifice within the piping system adjusts the distribution of sealing air to rotor bearing seals. Extracted compressor air may additionally be cooled by the heat exchanger. The system ensures a minimum sealing airflow and prevents unnecessary efficiency reduction of the gas turbine.

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In order to seal a rotating rotor against ambient air at the bearings, gas turbines are often operated and sealed using sealing air from its own supply. This air is taken from an available extraction point of the compressor. For a variable guide vane operated compressor, the extraction is frequently not optimized for the complete load operation. For example, at an early stage of operation, the pressure is not sufficient at low load, while at a later stage the pressure (and therefore the flow) is too high at base load (see figure 1).

Figure 1:  Pressure requirements for sealing air


If the gas turbine is operated within a large range of variable guide vane operation, the sealing air supply is essential at a later compressor stage to ensure sufficient air supply at low load. At higher load, if the variable guide vane is open, the higher pressure at this stage results in unnecessary high airflow and therefore reduces the gas turbine efficiency.


The system described herein ensures a highly reliable system and sufficient sealing air for the complete load range of a gas turbine, while the airflow is kept at a minimum level, which in turn allows highest possible efficiency.

The gas turbine system as shown in figure 2 comprises a minimum flow orifice and a pressure regulator, and an optional heat exchanger. The minimum flow orifice and the pressure...