Rotary kinetic fluid motors or pumps – With lubricating – sealing – packing or bearing means having... – For shaft sealing – packing – lubricating or bearing means
Patent
1995-11-30
1997-03-18
Larson, James
Rotary kinetic fluid motors or pumps
With lubricating, sealing, packing or bearing means having...
For shaft sealing, packing, lubricating or bearing means
415176, 60 3908, 184 611, F01D 2518
Patent
active
056116616
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a gas turbine engine, especially an aircraft gas turbine engine, with a compressor bearing chamber and a turbine bearing chamber. Barrier air chambers surround the bearing chambers that are supplied with oil. The barrier air chambers are supplied with a barrier air flow by a low-pressure compressor or fan and a high-pressure compressor. The flow passes at least partially into the associated bearing chambers through labyrinth seals and is conducted away from the bearing chambers through an oil separator, especially into the environment. Reference is made to Great Britain Patent document GB-B- 702 931 as an example of the prior art.
The seals provided in the bearing chambers for the shafts of a gas turbine engine between the bearing chamber wall as well as the shaft passing therethrough are necessary to prevent lubricating oil or an oil mist from entering the compressor or the turbine. This seal must be made contact-free, so that usually labyrinth seals are used which are, however, additionally traversed by a barrier air flow to achieve an optimum sealing effect. This barrier air flow comes from a barrier air chamber surrounding the bearing chamber through the labyrinth seals into the bearing chamber and is conducted out of the latter through an oil separator, preferably into the environment, but could also be used later in another fashion.
In order to ensure the flow of barrier air described above from the barrier air chambers into the bearing chambers and from the latter into the environment for example, a certain pressure drop is always required between the barrier air chambers and the environment, i.e. the pressure in the barrier air chambers must be larger by a certain amount than that downstream from the bearing chambers. Therefore, it is conventional to supply the barrier air chambers from the low-pressure compressor, which can also be designed as a fan, or from the high-pressure compressor with a barrier air flow. However, during the operation of a gas turbine engine, operating points can occur in which the pressure delivered by the low-pressure compressor or fan is not sufficient to deliver a barrier air flow which overcomes the flow resistances, for example, in the labyrinth seals, through the barrier air chambers, as well as the bearing chambers, and then through an oil separator and into the environment. Great Britain Patent document GB-B- 702 931 mentioned above therefore proposes to tap off the barrier air flow from the high-pressure compressor in these cases.
This known prior art is disadvantageous because not only is a separate switching valve required, with the aid of which the barrier air flow is tapped off either from the low-pressure compressor or fan or from the high-pressure compressor. Also this known prior art is disadvantageous because each of the bearing chambers is exposed at least temporarily to a relatively high-temperature barrier air flow, since, as is known, a definitely elevated temperature level prevails in high-pressure compressors.
There is therefore needed an improved and simplified manner of providing barrier air supply to a gas turbine engine, especially one for an aircraft gas turbine, having a compressor bearing chamber, a turbine bearing chamber and barrier air chambers surrounding the compressor and turbine bearing chambers. The barrier air chambers are supplied by a low pressure compressor or fan and a high-pressure compressor with a barrier air flow. The barrier air flow passes through labyrinth seals at least partially into an associated bearing chamber and is carried away from the latter through an oil separator.
These needs are met according to the present invention by a gas turbine engine wherein the compressor barrier air chambers are supplied by the low-pressure compressor or fan and wherein the turbine barrier air chambers are supplied with barrier air from the high-pressure compressor. The barrier air flow emerging from the compressor bearing chambers is mixed in an ejector with the barrier
REFERENCES:
patent: 3527054 (1970-09-01), Hemsworth
patent: 3722624 (1973-03-01), Buckland
BMW Rolls-Royce GmbH
Larson James
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