Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to an industrial gas turbine engine with a second spool having a variable inlet guide vane assembly for the low pressure turbine.
Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Variable angle vanes are used to vary the mass flow through compressor and turbine passages. Compared to fixed airfoils that have integral outer and inner end walls, variable vanes have leakage areas between the airfoil and the end walls. These leakage paths create undesirable aerodynamic losses. The larger the desired swing angle of the airfoil, the bigger the challenge to minimize these gaps. The cycle benefit for having an adjustable vane throat greatly outweighs the leakage debits.
Variable inlet guide vanes are used in both a compressor and a turbine. However, the structure for a turbine variable inlet guide vane is different than for the compressor variable inlet guide vane. In a compressor, the flow path is decreasing in height as the compressed air passing through the stages of the compressor increases in pressure. Thus, the radial or spanwise height of the trailing edge of the vane decreases in the flow direction of the compressed air. This is the opposite in a turbine where the compressed gas is increasing or expanding in the flow direction. Thus, in a turbine the spanwise height of the vane at the trailing edge is increasing in height. Thus, the leakage across the ends of the vane at the trailing edge will have greater areas due to this structure.
In addition to controlling the gaps, aerodynamic forces acting on the airfoil are considered to select the optimum rotation axis. The airfoil center of pressure is the location where the moments are zero. The rotation axis placed through the center of pressure yields no additional forces over friction to articulate the vane. This center of pressure can vary on position when the stagger angle of the airfoil is changed.
A turbine variable inlet guide vane assembly for a gas turbine engine, such as an industrial gas turbine engine having a low pressure turbine, where the variable inlet guide vane assembly includes guide vanes having airfoils that extend between large diameter outer and inner buttons in which the airfoil trailing edge extends into the two buttons so that no gap is formed. The airfoil has a center of rotation that is located aft or downstream from an aerodynamic center of pressure which will decrease any gap from forming in the movement of the airfoil from an open position to a closed position and thus increase a performance of the turbine. For a given leakage gap, leakage flow amount and performance loss per unit flow is larger at aft portion of turbine airfoil due to high airfoil velocities than in front portion.
The present invention is a variable inlet guide vane for a turbine in which a rotational axis of the airfoil is located aft of the aerodynamic center of pressure on the airfoil in order to eliminate leakage gaps at the two endwalls. This is done to articulate the turbine vane at the entrance of a low pressure turbine on an axis well aft of the aerodynamic center of pressure. The use of this aft places rotation axis in combination with large diameter end wall buttons, minimized the clearance gaps of the OD and ID interface of the airfoil to end walls. By placing rotation center aft of the aerodynamic center of pressure leakage gap over aft portion of airfoil is minimized. For a given leakage gap, leakage flow amount and performance loss per unit flow is larger at aft portion of turbine airfoil due to high airfoil velocities than in front portion.
The rotation axis centered aft of airfoil's aerodynamic center of pressure creates forces on the vane that makes the system inherently want to close, that is seen as a negative system function. The benefit of minimizing the airfoil to end wall gaps creates a performance improvement over todays state of the art (Axis forward of the center of pressure). Additional safeties on the sync ring system that is driven to articulate the vane stems would ensure that the actuator force will have full command to position the vanes at the desired angle.
This application claims the benefit to U.S. Provisional Application 62/249,598 filed on Nov. 2, 2015 and entitled VARIABLE LOW TURBINE VANE WITH AFT ROTATION AXIS.
This invention was made with Government support under contract number DE-FE0023975 awarded by Department of Energy. The Government has certain rights in the invention.
Number | Name | Date | Kind |
---|---|---|---|
3295827 | Chapman | Jan 1967 | A |
4150915 | Karstensen | Apr 1979 | A |
4314791 | Weiler | Feb 1982 | A |
4861228 | Todman | Aug 1989 | A |
4950129 | Patel | Aug 1990 | A |
5039277 | Naudet | Aug 1991 | A |
5517817 | Hines | May 1996 | A |
5931636 | Savage et al. | Aug 1999 | A |
6179559 | Weaver | Jan 2001 | B1 |
6481960 | Bowen | Nov 2002 | B2 |
6843638 | Hidalgo et al. | Jan 2005 | B2 |
6984105 | Clark et al. | Jan 2006 | B2 |
7125222 | Cornier et al. | Oct 2006 | B2 |
7264441 | Loudet | Sep 2007 | B2 |
7713022 | Major et al. | May 2010 | B2 |
7806652 | Major et al. | Oct 2010 | B2 |
7985053 | Schott | Jul 2011 | B2 |
8186963 | LaMaster | May 2012 | B2 |
8202043 | McCaffrey | Jun 2012 | B2 |
8517661 | Schilling | Aug 2013 | B2 |
8651803 | Jones et al. | Feb 2014 | B2 |
8734088 | Jones et al. | May 2014 | B2 |
9062560 | Hayford | Jun 2015 | B2 |
20120263571 | Ress, Jr. | Oct 2012 | A1 |
20130243580 | Hayford | Sep 2013 | A1 |
Number | Date | Country |
---|---|---|
1112058 | May 1968 | GB |
Number | Date | Country | |
---|---|---|---|
20170234152 A1 | Aug 2017 | US |
Number | Date | Country | |
---|---|---|---|
62249598 | Nov 2015 | US |