Power plants – Combustion products used as motive fluid – Combined with regulation of power output feature
Reexamination Certificate
1999-06-10
2001-08-07
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combined with regulation of power output feature
Reexamination Certificate
active
06269628
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of turbine engines, and in particular, turbine engines in which distinct engine components are integrally cast so as to increase resistance to thermal stress, and thus decrease the need for cooling flow across the engine components.
2. Description of the Prior Art
Turbine engines, and in particular, gas turbine engines, are typically deployed in aircraft for jet propulsion. A gas turbine engine may form the core of a conventional turbojet engine, or may be used in conventional hybrid applications, such as in turboprop engines combining both jet and propeller propulsion.
A problem that occurs in gas turbine engines is that the components of the engine often cannot withstand prolonged and repeated exposure to the hot gases created during the combustion process. Engine components, such as combustion exit ducts, are typically formed of thin sheets of wrought metal which cannot withstand the prolonged, cyclic exposure to hot engine gases which are typically created during engine operation. As a result, these components require some mechanism for cooling in order to maintain their structural integrity over the service life of the engine.
In recent years, solutions have evolved for cooling engine combustion chamber components during operation of the engine. Proposed solutions are set forth in U.S. Pat. No. 5,271,220 to Holmes et al, issued Dec. 21, 1993, and U.S. Pat. No. 5,280,703 to Corrado et al, issued Jan. 25, 1994. These patents disclose radial inflow gas turbine engines in which the combustion chamber is surrounded by a case wall. Relatively cool airflow from the compressor stage of the engine is vented between the case wall and the outer wall of the combustion chamber to cool the combustion chamber walls during engine operation. The cooling airflow extends around the combustion chamber walls. The cooling airflow is ultimately vented into the combustion chamber where it is released in the exhaust stream.
A third construction is disclosed in U.S. Pat. No. 4,439,982 to Weller et al, issued Apr. 3, 1994. In this invention, airflow is directed around the combustion chamber during which time it is drawn on for use in the combustion process. The combustion products are then directed to a reverse flow duct where they flow across alternating rows of stator vanes and turbine blades. The airflow directed around the combustion chamber is vented through a duct into the interior of the stator vanes for cooling the stator vanes during engine operation. The airflow entering the interior of the stator vanes is then released into the exhaust stream through holes near the trailing edge of the stator vanes.
Both Holmes et al and Corrado et al relate to radial turbines and are not really pertinent. Each of the above-mentioned references provides for airflow which cools the walls of the combustion chamber and, in the case of Corrado et al, cools the turbine nozzle as well. The high volumes of cooling flow necessary to cool these components essentially deteriorates the efficiency of the engine. This occurs because a significant portion of the airflow being directed towards the combustion chamber by the compressor stage is not used by the combustion chamber. Instead, a significant portion of this airflow is used for transferring heat away from the combustion chamber and associated components. This means that more of the airflow from the compressor stages must be used for cooling and thus less of the airflow may be used for combustion.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to reduce the volume of cooling airflow which must be directed over thermally stressed components in a gas turbine engine.
It is another object of the invention to provide an apparatus which reduces the volume of cooling airflow required over thermally stressed engine components.
It is another object of the invention to provide a method of manufacturing engine components which are more resistant to thermal stress, thus reducing the amount of cooling airflow needed to maintain these components at their designed operating temperatures.
It is a further object of the invention to provide a method of reducing the relative diameter of the walls of the combustion chamber in a gas turbine engine.
In accordance with the above objects, the invention provides a gas turbine engine including a combustion chamber connected to a reverse airflow duct having a first duct wall portion. The combustion chamber is surrounded by an annular passage which provides airflow to the combustion chamber. The apparatus comprises an engine component which includes a plurality of airfoils for guiding airflow from the combustion chamber. The engine component includes an inner ring and an outer ring. The inner ring is connected to a static support. The outer ring includes a circumferentially extending shroud which is integrally cast with a second duct wall portion of the reverse airflow duct.
In accordance with the above objects, the invention provides a method of manufacturing an engine component for use in a gas turbine engine including a reverse airflow duct having a first duct portion. The engine component includes a plurality of airfoils extending circumferentially around a central hub, and defines an inner ring and an outer ring. The method comprises the step of integrally casting a second duct portion of the reverse airflow duct with a circumferentially extending shroud formed on the radial outward end of the engine component.
REFERENCES:
patent: 3652181 (1972-03-01), Wilhelm, Jr.
patent: 3691766 (1972-09-01), Champlon
patent: 3761205 (1973-09-01), Cronstedt
patent: 3914070 (1975-10-01), Straniti
patent: 4195476 (1980-04-01), Wood
patent: 4439982 (1984-04-01), Weiler et al.
patent: 4639188 (1987-01-01), Swadley
patent: 4955192 (1990-09-01), Shekleton
patent: 5271220 (1993-12-01), Holmes et al.
patent: 5280703 (1994-01-01), Corrado et al.
patent: 5387081 (1995-02-01), LeBlanc
patent: 5758504 (1998-06-01), Abreu et al.
Astle Jeffrey W.
Pratt & Whitney Canada Corp.
Rodriguez William
Thorpe Timothy S.
LandOfFree
Apparatus for reducing combustor exit duct cooling does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for reducing combustor exit duct cooling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for reducing combustor exit duct cooling will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2477360