US3846062A

US3846062A - External recirculation burner

Info

Publication number: US3846062A
Application number: US00412750A
Authority: US
Inventors: R Quinn
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1973-11-05
Filing date: 1973-11-05
Publication date: 1974-11-05
Anticipated expiration: 1991-11-05

Abstract

A combustor assembly includes a combined swirl and jet inducing blade assembly for directing primary air into a primary combustion zone to produce a jet induced axial recirculation through an external recirculation flow path to preheat primary air being directed from the blades prior to passage into a primary combustion zone and further to produce a reverse recirculation of flow through the center of a primary combustion zone to stabilize combustion in the zone without producing pressure losses therein with the combined recirculation patterns serving to improve prevaporization of fuel particles being directed into the primary combustion zone by a spray producing nozzle.

Description

ante States atent m1 3 846 $2 Quinn Nov. 5, 1974 EXTERNAL RECIRCULATION BURNER Primary Examiner-Carroll B. Dority. Jr. [75] Inventor: Ronald E. Quinn, Indianapolis, Ind. Attorney Agem F Evans [73]. Assi nee: General Motors Cor oration,

g Detroit, Mich. p [571 ABSTRACT [22] Filed Nov 5 1973 A combustor assembly includes a combined swirl and jet inducing blade assembly for directing primary air [21] Appl. No.: 412,750 into a primary combustion zone to produce a jet induced axial recirculation through an external recircu- [52] us Cl 431/116 lation flow path to preheat primary air being directed [51] Int-.0. F23 from the blades prior to p g into a p y [58] Field 'j lt 52 bustion zone and further to produce a reverse recirculation of flow through the center of a primary combus- [56] References Cited tion 'zone to stabilize combustion in the zone without producing pressure losses therein with the combined UNITED STATES PATENTS recirculation patterns serving to improve prevaporiza- 2,048,321 7/1936 Carruthers et al 431/115 tion of fuel particles being directed into the primary ggx 1 combustion zone by a spray producing nozzle.

5 Claims, 7 Drawing Figures 1a ax :jLPZ I a 51k W a? w w I LF Illfitlllll\l 62 if as I Z2 3a 1 EN E W 5mm 3846l062 sum 10? 3 EXTERNAL RECIRCULATION BURNER This invention relates to combustor assemblies and more particularly to combustor assemblies having means therein for producing a recirculation pattern through a primary combustion zone to produce prevaporization of fuel prior to combustion thereof.

Various combustor designs have been proposed that include a jet induced recirculation stream for improving the combustion process in a primary combustion zone. Such systems, however, include a flame holder in the primary combustion zone that can effect the pressure drop through the combustor assembly in an undesirable manner.

Accordingly, an object of the present invention is to improve a combustor assembly by the provision therein of a combined swirl and jet distributing vane assembly for producing a swirl induced recirculation flow pattern with respect to a primary combustion zone that will stabilize combustion in the primary combustion zone without producing an excessive pressure drop thereacross and wherein the vane assembly further includes means for producing a jet induced secondary outer path recirculation through the combustion zone that will increase the quantity of recirculation over and above that produced by the swirl component of the blade assembly.

Another object of the present invention is to improve combustor assemblies of the type having an outer casing with an inlet dome and an outlet at the opposite end thereof and further including a combustor liner and means for supporting it in spaced relationship with the outer casing to provide an outer recirculation flow path by the provision therein of means for supporting the combustion chamber liner including a primary air pipe located centrally of the inlet end of the combustion chamber liner and including a plurality of flow directing hollow vanes thereon which serve to direct primary air from the inlet pipe into the combustion chamber and to produce a jet induced outer recirculation of flow and a swirl induced reverse inner recirculation of flow to improve the combustion process.

Still another object of the present invention is to provide a compact combustor assembly having an outer casing and a spaced inner combustion chamber liner wherein primary air is directed thereto through a plurality of hollow vanes at one end of the combustion liner, and wherein means are associated with the inlet vanes in a compact arrangement at one end of the combustion liner to produce a combined swirl induced and jet induced recirculation of flow through the combustion chamber to increase pre-mixing and prevaporization of fuel sprayed from a nozzle into the combustion chamber.

Another object of the present invention is to include a span wise slot in a swirler blade in a swirl recirculation stabilized combustor assembly wherein the jet slot serves to direct the primary air supply for combustion into the assembly and to serve as the inlet for primary air flow across swirl blade surfaces to produce a primary combustion zone recirculation flow within the combustion zone and to further produce a jet induced axial flow recirculation through the combustion zone in an outer recirculation path for increasing the recirculation rate during combustor assembly operation to improve mixing of primary air and fuel sprayed from a nozzle and to prevaporize spray fuel for improving stability of combustion within the primary combustion zone.

Still another object of the invention is to provide a combustor assembly having combined swirl and jet induced recirculation patterns therein wherein the assembly includes an open ended combustion chamber liner having a plurality of hollow swirl blades located at the inlet end thereof and wherein each of the blades includes a span wise jet slot thereon for discharging primary air into the combustion chamber and an inlet opening for flow of primary air through the jet slot and wherein in addition to directing primary air into the combustion chamber, the blades also serve to produce swirl and jet induced recirculation patterns within the primary combustion zone for stabilizing the combustion process therein.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the Drawings:

FIG. 1 is a view in longitudinal cross section of a combustor assembly including the present invention;

FIG. 2 is a vertical sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary sectional view taken along the line 33 of FIG. 2 looking in the direction of the arrows;

FIG. 4 is a longitudinal sectional view of a combustor assembly including a second embodiment of the present invention;

FIG. 5 is a vertical sectional view taken alongthe line 5-5 of FIG. 4;

FIG. 6 is a vertical cross sectional view taken along the line 6-6 of FIG. 4; and

FIG. 7 is a horizontal sectional view taken along the line 7-7 of FIG. 6.

Referring now to the drawings, FIG. 1 shows a combustor assembly 10 having an outer casing 12 with an inlet plate 14 closing one end thereof and an outlet tube 16 on the opposite end thereof. A primary air inlet pipe 18 is directed through a central opening 20 in the end plate 14 to serve as a support for a combined recirculation and combustion chamber liner subassembly 22. The subassembly includes a combustion chamber liner 24 having opposite

open ends

26, 28 in communication with a central primary combustion zone 30. The combustion chamber liner 24 is located intermediate the opposite ends of the outer casing and has the outer surface thereof spaced radially inwardly of the outer casing 12 to define an open ended annular recirculation passage 32 outwardly of the linear between the opposite open endsthereof.

The subassembly 22 is located in spaced relationship within the outer casing 10 by a plurality of circumferentially located support members 34 directed across the annular passage radially between the liner 24 and the outer casing 12 having the opposite ends thereof connected therebetween.

Additionally, the primary air inlet pipe 18 includes a closed end 36 thereon having a plurality of circumferentially located primary air outlet openings 38 therein. These openings 38 feed a plurality of air foil configured hollow swirler blades 40 located within the inlet end 26 of the combustion liner 24.

Each of the hollow swirler blades 40 include a root portion 42 defining an inlet opening to the hollow blades 40 which is connected around the outlet openings 38 in the primary inlet pipe 18. They also include a tip portion 44 secured to the inner surface of the liner 24 to close the radially outermost end of the blades.

As best seen in FIGS. 2 and 3, there is a plurality of circumferentially spaced blades 40 each including a leading edge 46 and an outwardly convex surface 48 that is curved from the leading edge 46 to a trailing edge 50 on the blade. The opposite side of the blade has a concavely formed surface 52 thereon whereby each of the adjacent blades define a diverging diffusion passage 54 from the leading edges of the blades 46 to the trailing edges 50 thereof. The blades are arranged angularly with respect to the longitudinal axis of the combustion chamber liner 24 and will direct recirculating flow from a mixing chamber 56 located between the inlet plate 14 and the inlet end 26 of the liner 24 through the passages 54 tangentially with respect to the inner surface of the liner 24 for producing a swirl component therein.

Additionally, in accordance with certain principles of the present invention, this swirl component is enhanced by the provision of a jet slot 58 which is formed in the convex surface 48 of each of the blades adjacent the leading edge 46 thereof through the vertical height of the vanes. This jet slot 58 serves as the inlet opening for primary air flow from pipe 18 into the combustion chamber 30. The primary air flow through the jet slots will have an axial component and a tangential component. The tangential component will be directed through the passage 54 into the combustion chamber 30 to produce an induced swirl recirculation of primary air from the outlet end of the liner 24 back toward the inlet end 26 thereof shown by reference numeral 66. This swirl induced recirculation is thereby directed interiorly of and centrally through the primary combustion zone 30 and will tend to stabilize a flame front produced by combustion of fuel and primary air therein.

In this embodiment of the invention, the fuel supply is in the form of a fuel tube 60 directed concentrically through the pipe 18 and a central opening 62 in the closed end 36 of the pipe 18 so as to locate a spray nozzle 64 at the inlet end 26 of the inner combustion liner 24. The nozzle 64 will distribute a fuel spray pattern 68 of approximately 90 into the primary combustion zone. This spray pattern mixes with the primary air directed by the swirler blades 40 into the inlet end 26 of the liner 24 for premixing of the primary air and fuel. Additionally, the swirl induced recirculation will direct combustion products into the primary inlet swirl pattern to increase the temperature thereof as it mixes with the spray pattern from the nozzle 64 to produce prevaporization of the fuel prior to combustion in the zone 30.

Additionally, the primary air flow through the jet slots 58 will induce an outer recirculation flow pattern by virtue of the fact that it includes an axial component that will be directed through the combustion zone 30 thence through the outlet 28 and will be drawn by jet entrainment through the passage 32 and thence through the mixing chamber 56 to the leading edges 46 of each of the blades. This outer recirculation flow pattern is illustrated by the reference numeral 70 and will increase the rate of recirculation over that produced by the swirl induced pattern at 66 so as to further increase prevaporization of the primary air and fuel spray particles before combustion in the zone 30.

In this embodiment of the invention, the outlet H6 includes a plurality of circumferentially spaced secondary air flow ports 72 therein for directing dilution air into the outlet tube 16 of the combustion assembly for further combustion of any fuel particles that are not completely burned in the primary combustion zone 30.

Employment of aerodynamic configured blades 40 enhances the efficiency of jet entrainment of recirculation flow in the outer passage 32.

The combination of a swirler blade that will produce a swirl component and a jet induced axial component will produce an inner recirculation path that will stabilize the combustion in the primary zone 30 without the need for an orifice plate flame holder thereby to reduce pressure drop through the primary combustion zone 30. The outer recirculation path defined by passage 32 is associated with the axial momentum imparted by the entrained flow through the passages 54 in combination with the location of the inner surface of the liner 24. This tends to direct flow from the outlets between each of the blades 40 across the inner surface of liner 24 where it is drawn back through the recirculation passage 32 thence into the inlets of the blades 40.

In the illustrated arrangement, the blades have a camber to produce a pronounced swirl pattern within the combustion chamber 30. The chamber is optimized to produce a proportional relationship between axial and swirl momentum components in the passages 54, which will result in the central reverse recirculation pattern 66 through the primary zone for stabilization thereof and an outer recirculation flow pattern 70 to produce an increase in the rate of recirculation.

As illustrated in FIG. 3, the primary air jets directed through the slots '58 pass through the diverging passages 54. Thus, primary inlet air is mixed to a degree within the passages through the diffusion action therein to produce a secondary recirculation effect. This secondary recirculation is separated from the mixing zone 56 immediately downstream of the outlet from the vanes by virtue of the diffusion action in the blades. This effect, however, will not be prevelant in an arrangement where the primary air is directed into the combustion chamber for example by provision of a slot that is located closely adjacent the trailing edges of the blades 40 on the convexly configured surface 54 of the air foil. Such an arrangement, however, does retain the swirl induced central flow 66 through the primary zone as well as the jet induced outer recirculation flow pattern 70 to produce both stability and an increased recirculation rate.

By virtue of the arrangement as illustrated in FIGS. 1 thru 3, it is possible to maintain both a jet induced external and a swirl induced internal recirculation simultaneously within the combustion chamber 30. The external recirculation serves to increase the total quantity of recirculation for a fixed total momentum through the blade passages 54 as imparted by the primary air flow through the jet slots 58 while also establishing a central internal recirculation swirl pattern reversely through the combustion zone 30. The internal recirculation stabilizes the primary combustion zone without pressure losses normally associated with flame holders that previously have been utilized with solely jet induced recirculation type systems.

Referring now to the embodiment of the invention illustrated in FIGS. 4 thru 7, a combustor assembly 78 is illustrated including an outer casing 80 having a domed inlet end 82 and a tubular outlet end 84 thereon. The domed inlet end 82 includes a central tubular extension 85 thereon in which is located a support ring 86 having a central opening 88 therein for location of an opened end 90 of a primary air inlet pipe 92. The pipe 92 extends coaxially of the outer casing 80 and concentrically within acombustion chamber liner 94 having opposite open ends 96, 98. The liner 94 encloses an air distribution and recirculation inducing assembly 100 located within the inlet end 96 of the liner 94. The outlet end 98 of liner 94 defines a primary combustion zone 102 of the assembly 80.

A closure plate 104 is supported within the downstream end 106 of the primary air inlet pipe 92 to separate the primary combustion zone 102 from a primary air plenum 108 within pipe 92. The plate 104 includes a central opening 110 therein in which is welded a bushing 112 that receives a fuel supply pipe 114 directed centrally through the inlet end 90 of the primary air supply pipe 92 and having the opposite end thereof extending into the upstream end of primary combustion zone 102 where a nozzle 116 thereon is located to produce a spray pattern 118 of fuel into the combustion zone 102.

The combustion liner 94 is spaced radially inwardly of the outer casing 80 to define an outer recirculation passage 120 for flow of recirculation between the inlet and outlet ends 96, 98 of the liner 94.

As best illustrated in FIG. 6, the subassembly 100 includes a plurality of radially outwardly directed hollow ducts 122 each having an open base 124 connected around an outlet opening 126 from the plenum 108. Each of the ducts has a radially outward cover 128 closing the outer end thereof. The ducts are spaced at circumferentially located points on the outer surface of the pipe 92 as seen in FIG. 6 to define a plurality of circumferentially spaced axial flow passages 130 for passage of recirculation flow from the passage 120 across an annular curvilinear surface 132 of the domed end 82 so as to direct return recirculation axially into the combustion zone 102 radially outwardly of the outer surface of the pipe 92.

The ducts 122 each include a vertical jet slot 134 therein at the downstream edge thereof which overlies the leading edge 136 of a swirler blade 138 that is curved from the leading edge to form a downstream convexly configured surface 140 terminating in a trailing edge 142. The trailing edge is directed at an acute angular relationship with respect to a plane transverse of the primary air supply pipe 92 and each one of the adjacent blades 138 as best illustrated in FIG. 5 forms a curvilinear passage 144 that will direct primary air discharged through the slot 134 on each of the ducts to produce a tangential component thereon which will produce a swirl pattern around the inner surface of the combustion liner 94. This swirl pattern will pass through the primary zone 102 and will produce a reverse recirculation pattern illustrated by reference numeral 146 through zone 102 which will stablize the combustion process therein.

Additionally, the jet flow from the slots 134 will enhance this swirl pattern and furthermore will have an axial component to produce an outer recirculation flow pattern illustrated by the arrows marked by reference numeral 148 that proceeds from the slots 134 through the radially outermost parts of the primary combustion zone 102 radially outwardly of the swirl pattern directed centrally therethrough and will thence pass through the outer recirculation passage and will be directed by the surface 132 through the passages in an axial direction where they will be picked up by the jet entrainment action of primary air flow through the jets 134. There will be a certain amount of secondary recirculation within the passages 144 to mix the recirculation flow with primary inlet air from the slots 134 to heat the primary air so that it will produce an improved prevaporization of fuel particles in the spray pattern 118 in a mixing zone 150 immediately downstream thereof. As in the first embodiment, this embodiment includes secondary air flow ports 152 and the outlet tube 84 for further combustion of the air-fuel prior to passage from the combustor. The recirculation flow induced by the assembly 100 will produce increased recirculation and will reduce pressure loss across the combustion chamber of the assembly 80.

While the embodiments of the present invention, as herein disclosed, constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is:

l. A combustor assembly having an outer casing including an inlet dome on one end thereof, a tubular combustion chamber liner located within said outer casing having an inlet end and an outlet end, said linear being spaced inwardly of said outer casing to define an outer recirculation passage, means directed through said outer dome for directing primary inlet air and fuel to said combustion chamber, a plurality of swirler blades located in the inlet of said combustion chamber liner for producing a swirl induced recirculation of flow from the outlet end of the combustion chamber to the inlet end thereof during the combustion process, each of said swirler blades having a hollow duct portion and including an inlet opening at the base thereof for directing primary air into the interior of the blades, each of said blades further including a jet nozzle slot on the surface thereof for producing a jet flow across said vanes to induce recirculation flow through said combustion chamber from the inlet to the outlet thereof thence through said recirculation passage between said combustion chamber liner and said outer casing for enhancing recirculation of heated gas from the combustion chamber to the fuel supply means for producing improved prevaporization of fuel particles prior to combustion thereof within the combustion chamber defined by said liner.

2. A combustor assembly including an outer casing having an inlet end and an outlet end, a combustion chamber liner located within said outer casing in spaced relationship therewith to define an annular recirculation passage therebetween, said inlet liner being opened at the opposite ends thereof, a primary air inlet pipe directed through the inlet end of said outer casing interiorly of said combustion chamber liner, said primary inlet air pipe having a plate closing one end thereof and being opened at the opposite ends thereof, a bushing supported on said closure plate, a fuel tube directed through said bushing having a nozzle thereon located within the interior of said combustion chamber liner downstream of said primary air pipe, a plurality of swirler blades supported on the outer periphery of said primary air tube each of said swirler blades including a radially outwardly directed hollow duct portion thereon and a downstream segment curved with respect to the longitudinal axis of said combustion chamber, each of said ducts having an inlet opening in communication with the interior of said primary air tube and a vertical slot formed therein at the leading edge of the curved segment for directing primary air as a jet against the curved segment to produce a jet induced recirculation of flow outwardly of said combustion chamber liner thence through said recirculation passage back to the inlet end of said combustion chamber, said swirler blades producing a reverse recirculation of flow from the outlet of said outer casing through said combustion chamber, said jet induced recirculation and said swirl induced recirculation combining to produce improved prevaporization of fuel discharge from said nozzle to improve combustion of air and fuel within said combustion chamber, means at the outlet of said outer casing for directing secondary air flow into said combustion products from said combustion chamber to further enhance combustion of fuel particles prior to discharge from said combustor assembly.

3. A combustor assembly having an outer casing including a domed inlet end and a tubular outlet end thereon, a combustion liner located within said outer casing having opened ends thereon, means for supporting said combustion chamber within said outer casing in spaced relationship therewith to form an annular recirculation passageway therebetween, said support means including a primary inlet pipe having an opened end supported within said domed inlet end of said outer casing, means for closing the opposite end of said primary air pipe, a plurality of swirler blades each having a root portion thereon connected to the outer surface of said primary pipe and a tip portion thereof connected to the inner surface of said combustion liner, each of said blades being curved with respect to the longitudinal axis of said combustion liner to produce a swirl pattern therethrough for inducing a reverse recirculation of flow from the outlet of said outer casing through the interior of said combustion liner, each of said swirler blades having means including a jet slot across the vertical span of each of the blades between the outer surface of said primary air inlet pipe and the inner surface of said combustion liner at a point located near the leading edge of said swirler blade, means for directing primary air from said primary inlet air through said slot for inducing a jet flow therefrom, said swirler blades directing said jet flow into said combustion liner, said jet induced flow across said blade including a swirl component and an axial component, said swirl component producing a reverse recirculation of flow from the outlet of said outer casing to the outlet of said combustion liner which is generally centrally located within said combustion chamber for stabilizing a primary combustion zone without producing pressure loss within said combustion zone region, said jet induced flow further including an axial component to induce a recirculation of flow from the inlet to the outlet end of said combustion liner for returning heated combustion products across the leading edge of each of said swirler blades for further mixing with the jet flow of primary air through said jet slots in between each of said swirler blades.

4. A combustor assembly comprising an outer casing having a domed inlet and a tubular outlet end, a combustion chamber liner located within said outer casing having opposite opened ends therein, means for supporting said combustion chamber liner within said outer casing in spaced relationship therewith to form an external recirculation passage, said combustion chamber liner defining a primary combustion zone, means for directing fuel and primary inlet air into said primary combustion zone, said means including a primary inlet pipe supported on the domed end of said outer casing and including a closed end thereon located at the inlet end of said combustion liner, said closed end including a plurality of circumferentially spaced primary air outlets thereon, a plurality of primary swirler blades each having a hollow interior thereon and an aerodynamically configured outer surface located within the inlet end of said combustion liner, each of said swirler blades having a root portion connected to said primary inlet pipe around the primary outlet opening therein to direct the primary air into the interior of said blades, each of said blades having a tip portion thereon connected to said combustion chamber liner, said swirler blades being located circumferentially around said primary inlet pipe to define a plurality of circumferentially located flow paths having an inlet end defined by the leading edge of each of said blades, each of said blades having a convexly curved surface thereon located with respect to the leading edge of an adjacent blade to form a flow passage therebetween, each of said blades being spaced at the trailing edges thereof with respect to an adjacent blade to form a diffusion section, each of said blades further including a vertical slot therein downstream of the leading edge to direct primary air from the interior of said plates as a jet into the diffusion section for inducing recirculation of flow from the outlet of said combustion liner through said recirculation passage to the inlet of each of said vanes, said slot jet further inducing a swirl component across said blades for producing reverse recirculation of flow from the outlet end of said combustion liner to the inlet end thereof through the center of said primary combustion zone to stabilize the primary combustion zone without excessive pressure loss therein, a jet fuel distributing nozzle directing a fuel spray pattern into the primary combustion zone which mixes with the reverse recirculation through said zone and said jet induced recirculation to produce preheating of primary air and prevaporization of fuel particles therein prior to combustion thereof in said primary combustion zone, said outer liner having a tubular outlet including means therein for directing secondary dilution air flow therein for further combustion of fuel and air prior to passage from said combustion assembly.

5. A combustor assembly comprising an outer casing having a domed inlet end and a tubular outlet end, an opened ended combustion chamber liner located within said outer casing having an open inlet thereon spaced closely adjacent said domed end of said outer casing and an opened outlet located intermediate the ends of said outer casing, said combustion chamber liner defininga primary combustion zone within said outer casing, means including a primary inlet pipe supporting said combustion liner within said outer casing in spaced relationship therewith to define an annular recirculation passage therebetween, said annular recirculation passage communicating with the opposite open ends of said combustion liner, said primary air inlet pipe having an opened end at the domed end of said outer casing and a closed end located intermediate the opened ends of said inner combustion liner, a plurality of radially outwardly directed ducts supported between said primary air inlet pipe and said combustion liner at the inlet end thereof, each of said ducts having an open end thereon in communication with the interior of said primary pipe for receiving primary air therefrom, said ducts each including a slot through the vertical extent thereof facing in a downstream direction of said combustion liner, means forming a curved blade having the inlet end located at said slot and a curved surface formed angularly with respect to the longitudinal axis of said combustion liner and terminating at a trailing edge that is inclined in a downstream direction from the outer surface of said primary air tube to the inner surface of said combustion liner, primary air being directed from said slot inducing an axial flow through passages between each of said circumferentially spaced ducts from the recirculation passage through the inlet end of said combustion chamber liner, said axially induced flow passing through said combustion chamber and being drawn for return flow through said annular recirculation passage, said jet induced axial recirculation heating primary air flowing from said slots and mixing therewith between each of said curved blades, said curve blades further producing a swirl induced recirculation from the outlet of said outlet casing to the outlet of said inner combustion liner and centrally of said primary combustion zone to stabilize combustion therein without excessive pressure across said primary combustion zone, said jet induced axial recirculation and said swirl induced recirculation combining to preheat primary combustion air from said pipe, means for directing fuel into said primary combustion zone mixing with said jet induced recirculation to prevaporize fuel particles prior to combustion within said zone.

Claims

1. A combustor assembly having an outer casing including an inlet dome on one end thereof, a tubular combustion chamber liner located within said outer casing having an inlet end and an outlet end, said linear being spaced inwardly of said outer casing to define an outer recirculation passage, means directed through said outer dome for directing primary inlet air and fuel to said combustion chamber, a plurality of swirler blades located in the inlet of said combustion chamber liner for producing a swirl induced recirculation of flow from the outlet end of the combustion chamber to the inlet end thereof during the combustion process, each of said swirler blades having a hollow duct portion and including an inlet opening at the base thereof for directing primary air into the interior of the blades, each of said blades further including a jet nozzle slot on the surface thereof for producing a jet flow across said vanes to induce recirculation flow through said combustion chamber from the inlet to the outlet thereof thence through said recirculation passage between said combustion chamber liner and said outer casing for enhancing recirculation of heated gas from the combustion chamber to the fuel supply means for producing improved prevaporization of fuel particles prior to combustion thereof within the combustion chamber defined by said liner.

5. A combustor assembly comprising an outer casing having a domed inlet end and a tubular outlet end, an opened ended combustion chamber liner located within said outer casing having an open inlet thereon spaced closely adjacent said domed end of said outer casing and an opened outlet located intermediate the ends of said outer casing, said combustion chamber liner defining a primary combustion zone within said outer casing, means including a primary inlet pipe supporting said combustion liner within said outer casing in spaced relationship therewith to define an annular recirculation passage therebetween, said annular recirculation passage communicating with the opposite open ends of said combustion liner, said primary air inlet pipe having an opened end at the domed end of said outer casing and a closed end located intermediate the opened ends of said inner combustion liner, a plurality of radially outwardly directed ducts supported between said primary air inlet pipe and said combustion liner at the inlet end thereof, each of said ducts having an open end thereon in communication with the interior of said primary pipe for receiving primary air therefrom, said ducts each including a slot through the vertical extent thereof facing in a downstream direction of said combustion liner, means forming a curved blade having the inlet end located at said slot and a curved surface formed angularly with respect to the longitudinal axis of said combustion liner and terminating at a trailing edge that is inclined in a downstream direction from the outer surface of said primary air tube to the inner surface of said combustion liner, primary air being directed from said slot inducing an axial flow through passages between each of said circumferentially spaced ducts from the recirculation passage through the inlet end of said combustion chamber liner, said axially induced flow passing through said combustion chamber and being drawn for return flow through said annular recirculation passage, said jet induced axial recirculation heating primary air flowing from said slots and mixing therewith between each of said curved blades, said curve blades further producing a swirl induced recirculation from the outlet of said outlet casing to the outlet of said inner combustion liner and centrally of said primary combustion zone to stabilize combustion therein without excessive pressure across said primary combustion zone, said jet induced axial recirculation and said swirl induced recirculation combining to preheat primary combustion air from said pipe, means for directing fuel into said primary combustion zone mixing with said jet induced recirculation to prevaporize fuel particles prior to combustion within said zone.