Power plants – Combustion products used as motive fluid
Reexamination Certificate
1999-05-10
2001-04-24
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
Reexamination Certificate
active
06220012
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to turbine engines and, more particularly, to apparatus and methods for preventing stall in a compressor.
A turbine engine typically includes a fan in front of a core engine having, in serial flow relationship, a low pressure compressor, or a booster, and a high pressure compressor. The low pressure compressor and the high pressure compressor each include an inlet section and a discharge section.
During engine power reductions, the inlet section of the high pressure compressor may generate an airflow blockage resulting from a flow differential between airflow through the high pressure compressor inlet section and the airflow through the booster discharge section. The airflow blockage generates a back pressure in the booster which causes the booster operating line to migrate closer to a stall limit. Migration of the booster operating line closer to the stall limit restricts the operating range of the turbine engine because less air continues to flow through the booster.
If the booster stalls, loud banging noises and flames or smoke may be generated at the booster inlet and/or discharge section. A booster stall condition results in excessive wear, degradation of performance, and a reduction in engine reliability and durability. In order to compensate for booster stall, the booster is typically over constructed, leading to more parts that in turn make the booster, and the resulting engine, heavier.
Booster stall is mitigated in existing engines by the use of complex variable bleed doors, or valves, which open during unsteady airflow conditions and allow a portion of the booster airflow to bypass the high pressure compressor. However, the bleed doors may fail or malfunction due to the complexity of the doors and valves.
Accordingly, it would be desirable to provide efficient booster stall protection without the added complexity of variable bleed doors. Additionally, it would be desirable to provide improved reliability of booster stall protection.
BRIEF SUMMARY OF THE INVENTION
A booster which includes a stator casing, a rotor shroud, and stator and rotor hub treatments extends the booster stall limit capability, and eliminates the need for variable bleed, or bypass, doors. More particularly, and in an exemplary embodiment, the booster includes a passageway which extends from a higher pressure portion of the booster to a lower pressure portion of the booster. The passageway includes angular slots which extend along an airflow path from the higher pressure portion of the booster to the lower pressure portion of the booster.
In operation, an airflow enters the passageway at a higher pressure portion of the booster. The airflow travels through the passageway from the higher pressure portion of the booster to the lower pressure portion of the booster, and expends energy and decreases in pressure while traveling through the passageway. The airflow then exits the passageway at the lower pressure portion of the booster and returns to the airflow path.
Recirculation of the airflow from the higher pressure portion of the booster to the lower pressure portion of the booster extends a booster stall free operating region and reduces the likelihood that the booster will reach a stall limit during engine power reductions. As back pressure diminishes, the recirculation lessens and the booster returns to a more normal operation. By eliminating the bypass doors or valves, the passageway increases engine and booster stall protection reliability.
REFERENCES:
patent: 5282718 (1994-02-01), Koff et al.
patent: 5562404 (1996-10-01), Koff et al.
patent: 5607284 (1997-03-01), Byrne et al.
Hauser Ambrose A.
Seda Jorge F.
Szucs Peter N.
General Electric Company
Herkamp Nathan D.
Hess Andrew C.
Rodriguez W
Thorpe Timothy S.
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