Embodiments relate to a combustor, and more particularly, to a combustor for improving combustion performance and achieving low emission combustion by increasing a gas recirculation flow.
Technology for minimizing environmental pollution caused by combustion of fossil fuel is important in designing and operating a combustor. Research has recently been conducted on moderate or intense low-oxygen dilution (MILD) combustion to improve the efficiency of a combustor and achieve low emission combustion. MILD combustion is also named flameless oxidation (FLOX) or high-temperature air combustion (HiTAC).
A combustor is a component that performs a function of generating power for an engine or a gas turbine by combusting fuel. With global trends of stricter regulations on nitrogen oxide and carbon monoxide emissions, MILD combustion which enables stable combustion by mixing air with a high-temperature exhaust gas that is discharged as a waste product even in a combustor to reduce an oxygen concentration and deliver a flow of high-temperature air is applied.
Korean Patent Publication No. 2010-0061538 discloses technology of supplying fuel and a diluted solution in a secondary combustion zone downstream of a primary combustion zone of a combustion engine. The technology performs secondary combustion that assists combustion taking place in the primary combustion zone by providing a manifold on a wall that surrounds the secondary combustion zone, locating an injector nozzle in the manifold, and injecting the fuel in the secondary combustion zone. Although the technology may reduce the amount of fuel injected in the secondary combustion zone, there is no interaction between the combustion in the primary combustion zone and the combustion in the secondary combustion zone. That is, combustion performance in the primary combustion zone is not improved by fuel injection in the secondary combustion zone.
U.S. Pat. No. 4,389,848 discloses a structure in which a fuel injector includes a primary nozzle located on the upstream side of a burner and a secondary nozzle located on the downstream side and fuel and air are recirculated by injecting the fuel through the secondary nozzle. However, in this structure, since the secondary nozzle is located on an extension of the central axis of the primary nozzle of the burner, recirculation effect of the fuel and the air is not sufficient.
(Patent Document 1) Korean Patent Publication No. 2010-0061538 (Jun. 7, 2010)
(Patent Document 2) U.S. Pat. No. 4,389,848 (Jun. 28, 1983)
An objective of embodiments is to provide a combustor for improving combustion performance by reducing a flame temperature by increasing a gas recirculation flow.
Another objective of the embodiments is to provide a combustor for achieving low emission combustion by performing moderate or intense low-oxygen dilution (MILD) combustion.
A combustor according to an embodiment may include: a combustion tube having a cylindrical shape with a combustion space where fuel is combusted, and including an inlet through which the fuel is introduced, an outlet through which a gas generated when the fuel is combusted is discharged, and a protrusion protruding inward from a wall surface between the inlet and the outlet; an injection unit configured to inject fuel into the combustion tube through the inlet of the combustion tube; and an additional injection unit located on the protrusion of the combustion tube and configured to inject fuel into the combustion tube.
The protrusion and the additional injection unit may respectively include a plurality of protrusions and a plurality of additional injection units, which are arranged to be spaced apart from one another in a circumferential direction of the combustion tube.
The protrusions and the additional injection units may be symmetric with respect to the center of the combustion tube.
The protrusion may include an outer support wall that protrudes toward the center of the combustion center further than the wall surface of the combustion tube and an inner support wall that protrudes toward the center of the combustion tube further than the outer support wall, the additional injection unit is located on the outer support wall, the inner support wall has a fuel hole that is formed at a position corresponding to the additional injection unit and through which the fuel injected by the additional injection unit passes to the combustion tube and inner air holes that are formed around the fuel hole, and the outer support wall has outer air holes that are formed around the additional injection unit.
Diameters of the outer air holes may be greater than diameters of the inner air holes.
The combustion space of the combustion tube may be divided into a first zone that is an upstream region where the fuel injected by the injection unit is combusted, collides with the fuel injected by the additional injection unit and air injected through the protrusion, and primarily recirculates toward the inlet and a second zone that is a region where the fuel injected by the additional injection unit proceeds to a position downstream of the first zone, is combusted, and secondarily recirculates toward the inlet.
The second zone may be formed about a central axis of the combustion tube in a longitudinal direction of the combustion tube and allows a combustion product generated in the second zone to be delivered to the first zone, and the first zone protrudes further outward than the second zone along the central axis of the combustion tube.
The protrusion may include a first inclined portion that is inclined toward the inlet of the combustion tube with respect to the wall surface of the combustion tube, a second inclined portion that is inclined toward the inlet of the combustion tube with respect to the wall surface of the combustion tube, and a connecting portion that extends parallel to the wall surface, connects the first inclined portion and the second inclined portion, and allows the additional injection unit to be located thereon.
An inclination angle between the first inclined portion and the wall surface may range from about 20° to about 60°.
An inclination angle between the second inclined portion and the wall surface may range from about 10° to about 90°.
A plurality of air holes through which external air is delivered into the combustion tube may be formed in the first inclined portion and the second inclined portion.
The combustor may further include: a preliminary mixing chamber to which the injection unit is coupled and that is located on the inlet; and a swirler provided in the preliminary mixing chamber and configured to supply a flow of air to the preliminary mixing chamber.
In a combustor according to the above-described embodiments, since dilution fuel is discharged through an additional injection unit located on a protrusion protruding inward from a wall surface of a combustion tube, an exhaust gas recirculation flow of the combustor may be enhanced. Accordingly, flameless combustion (e.g., moderate or intense low-oxygen dilution (MILD) combustion) may be performed in the combustor and combustion emissions may be greatly reduced.
Also, since the additional injection unit is located on the protrusion of the combustion tube, a path through which a gas of a first zone where primary combustion takes place may flow to a second zone at a downstream portion may be formed, and also the flow of dilution fuel injected by the additional injection unit may collide with the flow of dilution fuel and a gas of a primary recirculation flow zone and may flow to the second zone at the downstream portion. The dilution fuel injected by the additional injection unit may be combusted in the second zone at the downstream portion and then may recirculate toward the first zone at an upstream portion. Accordingly, the combustion and the recirculation flow in the first zone and the combustion and the recirculation flow in the second zone in the combustion tube are enhanced.
Configurations and operations of combustors according to embodiments will now be explained in detail with reference to the attached drawings. The expression ‘and/or’ used herein refers to any and all combinations of one or more of associated elements.
The combustor according to the embodiment of
The combustion tube 10 is manufactured to have a hollow cylindrical shape with a wall surface 13 and has therein the combustion space where fuel is combusted. Also, the combustion tube 10 includes the inlet 11 that is located on one side of the combustion tube 10 and through which fuel is introduced and the outlet 12 that is located on the other side of the combustion tube 10 and through which a gas generated when the fuel is combusted in the combustion space is discharged.
The combustion tube 10 includes the protrusion 20 protruding inward from a portion of the wall surface 13 between the inlet 11 and the outlet 12. The protrusion 20 is formed further downstream than the inlet 11 when viewed from the flow of fuel introduced into the combustion tube 10 through the inlet 11.
The injection unit 30 for injecting fuel into the combustion tube 10 is provided on the inlet 11 located on one side of the combustion tube 10. A preliminary mixing chamber 50 is provided on the inlet 11 of the combustion tube 10 and the injection unit 30 is provided in the preliminary mixing chamber 50. Also, a swirler 60 for delivering a flow of air to the inlet 11 of the combustion tube 10 is provided in the preliminary mixing chamber 50. The swirler 60 includes an air path 61 through which air is introduced. Positions and structures of the preliminary mixing chamber 50, the swirler 60, and the injection unit 30 are not limited thereto, and may be modified in various ways to inject fuel and efficiently mix the fuel with air.
The additional injection unit 40 for injecting fuel into the combustion tube 10 is provided on the protrusion 20 of the combustion tube 10. The additional injection unit 40 additionally supplies fuel and air into the combustion tube 10 at the downstream side when viewed from the flow of fuel introduced through the inlet 11 of the combustion tube 10.
Referring to
In
Although four protrusions 20 and four additional injection units 40 are illustrated in
The protrusion 20 includes an outer support wall 21 that protrudes toward the center C of the combustion tube 10 further than the inner surface of the wall surface 13 of the combustion tube 10, and an inner support wall 22 that protrudes toward the center C of the combustion tube 10 further than the outer support wall 21. Since the outer support wall 21 and the inner support wall 22 are spaced apart from each other, a space where a path of external air is formed is formed between the outer support wall 21 and the inner support wall 22. Due to such a double structure of the outer support wall 21 and the inner support wall 22, the protrusions 20 may enable the external air to be smoothly introduced into the combustion tube 10.
The additional injection unit 40 is located on the outer support wall 21. The outer support wall 21 has outer air holes 21b formed around the additional injection unit 40. The outer air holes 21b allow external air of the combustion tube 10 to be introduced into the space between the outer support wall 21 and the inner support wall 22.
The inner support wall 22 has a fuel hole 22a through which fuel injected by a fuel nozzle 41 of the additional injection unit 40 passes and inner air holes 22b formed around the fuel hole 22a. The inner air holes 22b discharge part of air, introduced into the space between the inner support wall 22 and the outer support wall 21 through the outer air holes 21b of the outer support wall 21, into the combustion tube 10.
Diameters of the outer air holes 21b of the outer support wall 21 are greater than diameters of the inner air holes 22b of the inner support wall 22.
The fuel hole 22a of the inner support wall 22 functions as a path through which fuel injected by the fuel nozzle 41 of the additional injection unit 40 and external air may be mixed and then may be supplied into the combustion tube 10.
Referring to
Also, the first inclined portion 21f and the second inclined portion 21r of the outer support wall 21 are connected by a connecting portion 21m that extends parallel to the wall surface 13. The additional injection unit 40 is located on the connecting portion 21m.
The outer support wall 21 also includes a first inclined portion 22f and a second inclined portion 22r that respectively extend parallel to the first inclined portion 21f and the second inclined portion 21r.
Referring to
The second zone C2 is a region where an exhaust gas generated after the fuel injected by the additional injection unit 40 proceeds to a position further downstream than the first zone C1 and is combusted secondarily recirculates toward the inlet 11.
Combustion of fuel injected by the injection unit 30 takes place in the first zone C1. Also, in the first zone C1, an exhaust gas generated when the fuel injected by the injection unit 30 is combusted collides with the fuel injected by the additional injection unit 40 and air introduced through the protrusions 20 and recirculates toward the inlet 11.
Referring to
In the area perpendicular to the longitudinal direction of the combustion tube 10, a region B of the combustion tube 10 provides a path through which dilution fuel obtained by mixing the fuel injected by the additional injection unit 40 and the air introduced through the protrusion 20 collides with a flow of an exhaust gas of the first zone C1 and a combustion byproduct generated by the additional injection unit 40 is delivered to the first zone C1. Hence, the region A functions as an exit of a recirculation flow, and the region B functions as an entrance through which a combustion product is introduced into the first zone C1.
The combustor according to the embodiment of
The combustor of the embodiment of
The preliminary mixing chamber 50 is provided on the inlet 11 of the combustion tube 10. When fuel is injected by the injection unit 30 provided in the preliminary mixing chamber 50, the fuel is introduced into the combustion tube 10 through the inlet 11 of the combustion tube 10 and is combusted. The combustion tube 10 includes the protrusion 20 protruding inward from a portion of the wall surface 13 between the inlet 11 and the outlet 12. The protrusion 20 is formed further downstream than the inlet 11 when viewed from the flow of fuel introduced into the combustion tube 10 through the inlet 11.
The protrusion 20 includes the first inclined portion 21f that is inclined toward the inlet 11 of the combustion tube 10 with respect to the wall surface 13 of the combustion tube 10, the second inclined portion 21r that is inclined toward the outlet 12 of the combustion tube 10 with respect to the wall surface 13 of the combustion tube 10, and the connecting portion 21m that connects the first inclined portion 21f and the second inclined portion 21r and on which the additional injection unit 40 is located.
The inclination angle θf between the first inclined portion 21f and the wall surface 13 ranges from about 20° to about 60°. The inclination angle θr between the second inclined portion 21r and the wall surface 13 ranges from about 10° to about 90°.
The protrusion 20 has a plurality of air holes 20b through which external air of the combustion tube 10 is introduced into the combustion tube 10.
The standard can-type combustor of Comparative Example 1 of
The standard can-type combustor of Comparative Example 2 of
Referring to
Referring to
Referring to
In each of Comparative Example 1 and Comparative Example 2, a mixing ratio between fuel and air before dilution fuel is injected is good.
Referring to
In the combustors of Comparative Example 1 of
It is found in the combustor of
When a pattern factor of a temperature distribution was analyzed by using computational fluid dynamics (CFD) analysis, the combustor of Comparative Example 1 obtained 0.234, the combustor of Comparative Example 2 obtained 0.162, and the combustor of
Tmax is a highest temperature, Tmean is a mean temperature, and Tinlet is an inlet temperature.
It is found in Comparative Example 1 and Comparative Example 2 that a similar nitrogen oxide distribution is observed. Referring to
Referring to a distribution of nitrogen oxide in the combustor of
It is found in Comparative Example 1 and Comparative Example 2 that a similar carbon monoxide distribution is observed. Referring to a distribution of carbon monoxide in the combustor of
In the graphs of
Referring to
Referring to
Referring to
Referring to
Referring to
According to a combustor of the above-described embodiments, since an exhaust gas recirculation flow of the combustor is enhanced, flameless combustion (e.g., MILD combustion) may be performed in the combustor. Accordingly, combustion emissions may be greatly reduced.
Also, since an additional injection unit is located on a protrusion of a combustion tube, a path through which a gas of a first zone where primary combustion takes place may flow to a second zone at a downstream portion may be formed.
Also, since the additional injection unit is located on the protrusion of the combustion tube and injects dilution fuel, the flow of the dilution fuel may collide with the flow of dilution fuel and a gas of a primary recirculation flow zone and may flow to the second zone at the downstream portion.
Also, the dilution fuel injected by the additional injection unit may cause combustion in the second region at the downstream and then may form a recirculation flow toward the first zone at an upstream portion.
While configurations and effects of embodiments have been particularly shown and described, it will be understood by one of ordinary skill in the art that various modifications and equivalent other embodiments may be made from the present invention. Accordingly, the true technical scope of the present invention is defined by the appended claims.
Embodiments relate to a combustor for improving combustion performance and achieving low emission combustion by increasing a gas recirculation flow.
Number | Date | Country | Kind |
---|---|---|---|
10-2015-0096790 | Jul 2015 | KR | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/KR2015/010778 | 10/13/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2017/007068 | 1/12/2017 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4389848 | Markowski et al. | Jun 1983 | A |
6499993 | Steber et al. | Dec 2002 | B2 |
7665309 | Parker | Feb 2010 | B2 |
8112216 | Davis, Jr. et al. | Feb 2012 | B2 |
8407892 | DiCintio et al. | Apr 2013 | B2 |
20070259296 | Knoepfel | Nov 2007 | A1 |
20090084082 | Martin | Apr 2009 | A1 |
20110067402 | Wiebe et al. | Mar 2011 | A1 |
20140174090 | Chen et al. | Jun 2014 | A1 |
Number | Date | Country |
---|---|---|
2011-163626 | Aug 2011 | JP |
10-2010-0061538 | Jun 2010 | KR |
2009078891 | Jun 2009 | WO |
Entry |
---|
International Search Report, issued by International Searching Authority in corresponding International Application No. PCT/KR2015/010778, dated Feb. 22, 2016, (PCT/ISA/210). |
PCT/ISA/220, dated Feb. 22, 2016, issued by the International Searching Authority in counterpart International Patent Application No. PCT/KR2015/010778. |
Written Opinion, issued by International Searching Authority in corresponding International Application No. PCT/KR2015/010778, dated Feb. 22, 2016, (PCT/ISA/237). |
Number | Date | Country | |
---|---|---|---|
20180202662 A1 | Jul 2018 | US |