CA1116416A

CA1116416A - Gas turbine combustor

Info

Publication number: CA1116416A
Application number: CA000303606A
Authority: CA
Inventors: Shigemi Mandai; Nobuo Sato
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1977-05-23
Filing date: 1978-05-18
Publication date: 1982-01-19
Also published as: JPS53143815A; IT1092054B; IT7819125A0

Abstract

47,705 GAS TURBINE COMBUSTOR
ABSTRACT OF THE DISCLOSURE
A stepped cylindrical combustion chamber for a gas turbine engine having secondary combustion air scoops pro-jecting thereinto wherein the first annular row of the air scoops are slanted obliquely to direct the air entering therethrough in a slightly downstream direction.

Description

UUl~ L) OL~ '1'111~ 11 V 1!~ \I'l'lUN
Field of the Invention:
.... _ _ . . . _ _ _ This invention relates ~o combustion chambers for gas turbine engines and more particularly to cy~indrical com~
bustion chambers having seconda~y air inlet tubes pro~ecting . thereinto to deliver combustion air to the combustion ~one.
Description of the Prior Art:
Reference is made to U.S. Patents 3,134,229 4,05~,02~; and 3,~72,664 to show various con~igurations of secondary air inlet tubes to gas turbine combustion ,.
chambers and generally referred to as air scoops~ In the first two pa~ents, the air scoops extend into the com-bustion chamber and, by design, deliver air in a pattern having a major upstream component for increased penetration and mixing of the air with the fuelO However, as subse-quently discussed, it has been found that this, in fact, causes upstream recirculation of the fuel, forming fuel rich pockets that produce smoke and hot spots on certain of the combustion parts causing premature burn-out of such parts.
The remaining patent shows an air scoop having a downstream slanted direction; however, the scoop does not .~

47,705 significantly extend into the combustion chamber for pene-tration of the airg and also the swirl imparted to the secondary air by the swirling apparatus within the scoops may well induce an upstream flow similar to that deseribed in the above patents.
SUMMARY OF THE IN~ENTION
-This invention provides a gas turbine combustion ehamber wherein at least the first row of secondary eombus-tion air inlet seoops of a eombustion ehamber are slanted downstream to minimize the upstream flow of air entering the eombustor therethrough and to, in turn, reduee the reeireu-lation of fuel intercepted and entrapped in the upstream air flow which would otherwise form fuel rich pockets causing smoke and early failure or burn-out of parts.
BRIEF DESCRIPTION OF THE DRQWINGS
Figure l is a schematic view of a prior art com-bustion chamber with radially extending secondary air scoops;
and, Figure 2 is a view similar to Figure l showing the chamber and air scoops of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure l, a stepped cylindrical com-bustion chamber 12 is shown having a fuel nozzle 11 at the head end. The primary combustion air enters at the head end through an air entry collar member 13. The primary air is divided upon entry, with a portion thereof flowing to adja-cent the face of the fuel nozzle for mixture with the fuel to provide the fuel rich easily ignited mixture, and another portion flowing along the inner face of the combustiorl dome 15 as guided by an annular baffle 14 to maintain a flow of ~, .

L~7, 705 cooling air along the wa]l of the combustor.
Secondary combustion air is injecked through a first annular row of air scoops 16 which extend into the combustion chamber to generally adJacent the primary com-bustion zone to provide penetration of secondary air into the rich air/fuel mixture to provide sufficient air to completely burn the fuel. A second downstream annular row of air scoops is also shown having less penetration. How-ever, it has been found that the primary radial direction of entry of the secondary air through the first row of scoops causes, in addition to the primarily downstream direction 19 of air flow, an induced air flow having an upstream compon-ent 18. This upstream flowing air intercepts and entraps a portion of the atomized fuel injected by the nozzle and redirects such fuel to generally ad~acent the baffle 14 and dome 15. This volume adJacent these members thus tends to become excessively rich in fuel, causing incomplete com-bustion producing smoke. In addition, combustion of such fuel in this region adjacent the baffle tends to overheat the baffle causing hot spots therein resulting in premature failure.
Also, the kinetic energy of the upstream flowing air is such that it will penetrate the cooling air flow along the wall of the dome 15 and diminish the cooling effects thereof to cause excessive heating in this area, again ultimately resulting in failure of the part.
Referring to Figure 2, the present invention is seen to comprise essentially the same cylindrical combustion chamber structure of ~igure 1 including a combustor 22 having a fuel injecting nozzle 21 in its upstream head end ^ ~ .

1,7,705 and an air inlet collar 23 supplying primary air to the fuel and a layer of cooling air along the wall of the dome 25 as guided by an annular baffle 24.
However, as is further seen in this configuration, the first annular row of secondary air inlet scoops 26 pro-e~2l jects into the combustion ~r~~~ ~h~ to adjacent the primary combustion zone with each scoop slanted in a direction such that the secondary air is directed slightly downstream.
Thus, with scoop structure and direction of entry according to the present invention, only a small portion of the enter-ing secondary air has an upstream direction thereby minimiz-ing the amount of air which entraps the atomized fuel and carries it to the upstream end, thereby reducing the amount of smoke produced by such unburned fuel over the normal prior art arrangement. ~urther, the reduced upstream air flow has a reduced kinetic energy so that it cannot as readily penetrate the layer of cooling air flowing across the dome surface and thereby overheating of this part is substantially eliminated.
Thus, with such obliquely slanted first row secon-dary air inlet tubesl the smoke emissions are decreased and the life of the upstream parts of the gas turbine combustion chamber is extended.

. ~ .

Claims

47,705 What is claimed is:

1. A generally cylindrical combustion chamber for a gas turbine engine having fuel/air inlet means at the upstream head end thereof and a first annular row of secon-dary air inlet tubes extending through the wall of the chamber and terminating generally adjacent the combustion zone therein and wherein said tubes are angled to project inwardly in a slight downstream direction to provide pene-tration of the air into the combustion zone and impart an initial downstream air flow component to minimize upstream flow of the secondary air exiting the tubes.