Patent application title: Method and apparatus for enhanced flameholding in augmentors
Wookyung Kim (Glastonbury, CT, US)
Mark Godfrey Mungal (Cupertino, CA, US)
Heinz Guenter Pitsch (Aachen, DE)
IPC8 Class: AF23D1446FI
Class name: Combustion flame holder having protective flame enclosing or flame stabilizing structure
Publication date: 2011-02-24
Patent application number: 20110045426
Techniques for the enhancement of the stability of an afterburning flame
in the viscinity of a low pressure loss augmentor are provided by various
geometrical modifications of the base region of the augmentor.
1. A flame augmentor for use in a jet engine, wherein the bluffbody base
of said flame augmentor comprises a plurality of two-dimensional and
three-dimensional geometrical features to enhance flameholding.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority from U.S. Provisional Patent Application 61/236,456 filed Aug, 24, 2009, which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to thrust augmentors used in jet engines. In particular, the invention relates to techniques to enhance flameholding in augmentors.
BACKGROUND OF THE INVENTION
Thrust augmentors are used in jet engines as a means to provide additional thrust capability with little mechanical complexity. While the V-gutter has been used in the past, an alternate generic design for the flameholder uses a more streamlined shaped body for reducing the stagnation pressure loss and it includes a bluffbody with a rounded (or elliptic) nose, some streamwise length and a rectangular trailing edge. Fuel is injected through a set of ports upstream of the trailing edge, mixes with the hot gases and eventually forms a flame which is anchored by the recirculation downstream of the trailing edge. The present invention advances the art by disclosing new designs and methods for flameholding in augmentors.
SUMMARY OF THE INVENTION
In one aspect, the enhancement of afterburning flame stability and the change of the flow field in the wake region of new, low pressure loss flame augmentors, of variously modified base geometries, are disclosed in a high temperature (˜ 1300 K) vitiated flow. Flame liftoff height measurements are characterized by CH chemiluminescence, while the three-dimensional flow field is determined using stereo particle image velocimetry (PIV). The basic geometry of the augmentor is a rectangular body with a rounded nose. In one aspect, we find that a combination of both 2-D and 3-D geometric changes provides the best flameholding, i.e. the highest flame stability (lowest liftoff height), and furthermore, when local cavities are in phase with the fuel jets, the performance is optimal. Furthermore, it is conjectured from the PIV experiments that the observed stability enhancement is attributed to multi-dimensional vortices induced by both the presence of the local cavity as well as the two-dimensional geometric change.
Descriptions and figures of various embodiments of the present invention are disclosed in the following appendices:
Appendix A: A paper (10 pages) entitled "A Method and Apparatus for Improved Flameholding in Augmentors" by Kim et al.
Appendix B: A paper (4 pages) entitled "Stereo PIV Measurements of a Geometrically Modified Flame Augmentor Base" by Kim et al.
Appendix C: A paper (33 pages) entitled "Flame Liftoff Height Dependence on a Geometrically Modified Bluff Bodies in a Vitiated Flow" by Kim et al.
Appendix D: A paper (27 pages) entitled "The improvement of blowout limit in partially/fully premixed flames with geometrically modified bluffbody bases" by Kim et al.
As one of ordinary skill in the art will appreciate, various changes, substitutions, and alterations could be made or otherwise implemented without departing from the principles of the present invention. Accordingly, the examples and drawings disclosed herein including the appendix are for purposes of illustrating the preferred embodiments of the present invention and are not to be construed as limiting the invention.
Patent applications in class FLAME HOLDER HAVING PROTECTIVE FLAME ENCLOSING OR FLAME STABILIZING STRUCTURE
Patent applications in all subclasses FLAME HOLDER HAVING PROTECTIVE FLAME ENCLOSING OR FLAME STABILIZING STRUCTURE