US2541171A - Air inlet structure for combustion chambers - Google Patents

Description

Feb. 13, 1951 R. .1. M GARRY AIR INLET STRUCTURE FOR COMBUSTION CHAMBERS 2 Sheets-Sheet 1 Filed Jan. 25, 1947 INVENTOR- RICHARDJMGARRY {Ba/w ATTORNEY R. J. MCGARRY AIR INLET STRUCTURE FOR COMBUSTION CHAMBERS 2 Sheets-Sheet 2 Feb. 13, 1951 Filed Jan. 25, 1947 INVENTOR Patented Feb. 13, 1951 AIR INLET STRUCTURE FOR COIMBUSTION CHAMBERS Richard J. McGarry, New York, N. Y., assignor to The M. W. Kellogg Company, New York, N. Y., a corporation of Delaware Application January 25, 1947, Serial N0. 724,414

1 This application contains subject matter similar to that disclosed in Patent Number 2,531,810, issued November 28, 1950, with the same assignee. The invention described in the present application relates to combustion units of the general character in which fuel in finely divided form is injected into a chamber and burned in the presence of air, and although it has a wide range of utility, it is particularly useful, as for example, in connection with gus turbine plants.

Combustion systems such as those employed in connection with gas turbines for aircraft, must meet certain severe requirements. For example, they must secure complete fuel combustion, with a minimum of combustion pressure loss, and they must be of minimum weight and size to permit compact layouts. Hence, the combustion system must release heat at rates far in excess of those normally encountered in conventional combustion systems. For that purpose, the combustion system must be designed to control the heat liberation and the resulting temperatures in a manner that will permit said system to be constructed of readily available and easily work-able materials, and to be operated with a minimum of destrucr tive action on said materials.

Such a combustion system is required to perform dependably under all turbine load conditions and under all atmospheric conditions encountered in flight. The demands in are especially broad.

Another essential consideration in connection with a combustion system of the general type referred to, is the ease and facility with which the system ignites and loads up in starting, and the stability of the flame, especially at low fuel deliveries.

Among the objects of the present invention are this respect to provide a new and improved combustion unit,

of the general character referred to, which permits the attainment of high combustion rates with comparatively low pressure drops, and which effectively meets the requirements of efficiency, complete combustion and proper temperature distribution, and the usual aircraft volume and weight limitations.

Other objects of the present invention are to provide a new and improved combustion unit which starts easily, positively and consistently, without difficult manipulations, which afiords flame stability over a wide range of operation and at all speeds, altitudes and throttle positions, and which is suspectible to easy and close regulation.

In accordance with certain features of the present invention, a rich fuel-air mixture is cre- 12 Claims. (Cl. -44) ated in the forward end of a furnace chamber and ignited, and the resulting burning mixture is projected toward the discharge end of said chamber. outer housing wall forming an annular ai flow passage with the inner chamber walls. The air stream as it flows through the annular passage, has portions thereof diverted into spaced regions of the furnace chamber to create in said chamber flame propagating fuel-air mixtures. At the same time, the air passing through the annular air flow passage cools the outer housing wall and also the chamber wall.

To prevent the flame from being localized axlally of the furnace chamber, and to assure the eflicient creation and rapid distribution of the inflammable mixtures throughout the entire crosssection of the portion of said chamber in which combustion takes place, the air is projected into successive spaced regions therealong in such a manner that the air in one region is admitted through one or more air inlets angularly displaced from or staggered with respect to the air inlets of adjoining regions.

As a further feature of the present invention, the air streams are directed into the furnace chamber in a direction obliquely countercurrent to the direction of flow of the burning mixture in said chamber, and towards the active flame region, to afford a high degree of air turbulence in the axial region of the chamber, and thereby to achieve the desired high liberation of energy within a small combustion volume.

As another feature, the air inlets are arranged and distributed to attain effective air turbulence and diffusion around the axial zone of the chamber, without extinguishing the flame even at low fuel rates.

As a further feature, the furnace chamber wall and the outer housing wall defining the annular air flow passage are substantially free from obstructions tending to cause turbulence and the air inlets are designed to divert air from the annular air flow passage into the inner furnace chamber with a minimum of turbulence in said passage, whereby the impact or velocity head of the air as it flows through said passage is conserved as fully as possible, and the air pressure loss in the combustion unit is reduced to a minimum.

As another feature, the air inlets are designed to prevennt seepage Of liquid fuel therethrough, or accumulation of this fuel thereabout, thereby preventing combustion in the annular air flow passage, which combustion usually causes dan- The furnace chamber is enclosed in anserous overheating of the walls defining said passage and undesirable changes in the operating conditions.

Various other Objects, features and advantages of the invention will be apparent from the followingparticular description, and from an inspection of the accompanying drawings, in which:

Fig. 1 is a longitudinal axial section of one form of combustion unit embodying the present invention;

Figs. 2, 3, 4 and 5 are different sections or views of the combustion unit of Fig. 1, taken on lines 2-2, 3-3, 4-4 and 5--5 respectively of Fig. 1;

Fig. 6 is a plan view of the development or blank f the conical downstream section of the inner shell; and

Fig. 7 is a plan View of the development or blank of the conical upstream section of the inner" shell.

Referring to the drawings, the combustion unit of the present invention is shown of the type which is particularly adaptable for use in connection with gas turbine plants. However, it must be understood that as far as certain aspects of the invention are concerned, the unit of the present invention may be adapted for other combustion uses or for other air heating installations where a high energy release rate and low pressure loss are required.

The combustion unit of the present invention shown in the embodiment of Figs. 1'7, comprises in general, an outer housing wall H], which ineludes an air duct portion II, and an inner furnace wall l2 defining therein a combustion chamber formed of zones I3 and I4. The inner furnace wall |2 forms with the outer housing wall 10 an annular flow passage l for the air. The inner furnace wall l2 and the outer housing wall I!) are sectionalized, and mainly of thin, rolled metal shell construction, a-though part are of heavier forged or cast metal shell construction, as will be made apparent.

Air duct portion II is provided at its inlet end II with a flange It for bolting connection to the outlet IQ of an air compressor. Air duet portion II is of the type especially useful in connection with modern air compressors which discharge compressed air with relatively large velocity head, and has its cross-section increasing progressively in area in the direction of flow in the form of a streamlined diffuser to recover a large part of the velocity head and convert it into pressure head suitable for the conditions existing in the different combustion zones l3 and I4, while at the same time maintaining the necessary velocity to afford high rate of combustion in said zones.

The shape of the air duct portion II is shown of a specific design suitable for application to a gas turbine layout proposed in connection, for example, with an aircraft installation. In such a power plant, all of the principal elements of the plant, as for example, the compressor, the combustion unit and the gas turbine, would be arranged in line. In the particular layout shown in the drawings, the compressor would be disposed near the front of the combustion unit with its end connected to the air duct inlet l1, while the gas turbine would be disposed at the exhaust end of the combustion unit. There usually is a number of these combustion units circularly arranged around the axis of the turbine wheel.

The outer shell I0 is made of three sections 23, 24, and 25 of generally circular cross-section connected coaxially end to end. The inlet shell 4 section 23, usually cast or forged, is of conical or flaring shape, and is preferably integral with the air duct portion gated in a circumferential direction at its inlet end, to follow the curvature of the compressor outlet I9, as shown in Fig. 2, and changes gradually from this elongated shape, to merge with the generally circular cross-section of section 23.

The intermediate shell section 24 is generally cylindrical and is made of thin sheet metal; the joint or joints are preferably welded. The intermediate shell section 24 has an expansion joint 26 permitting endwise movement of the joined shell parts, and is removably connected to the inlet shell section 23 as by a coupling 21 of usual construction.

The discharge shell section 25 desirably of sheet metal construction, is of progressively reduced diameter downstream, and terminates in a neck 32. The section 25 is removably connected to the intermediate shell section 24 by a separable joint 33 also of usual construction, and it is removably connected to a conduit 34 by a studded flange connection 35. Conduit 34 may be any unit of the system or plant, and may, for example, be the conduit member leading to the gas turbine of the aircraft.

The inner shell l2 has at its inlet end a streamlined head flared to follow substantially the flaring curvature of the air duct portion I, and shaped to extend from an elongated arcuate edge 4| at one end to a circular cross-section at its downstream end 42. Clamped between the end 42 of head 40 and the upstream end 43 of the inner shell I2 is a fuel spray nozzle device 45 connected to a fuel inlet line 46. Nozzle device 45 is shown of the mechanical type adapted to project liquid fuel in the form of a conical spray under pressure into the combustion zone l3, and to atomize said fuel in said zone.

The inner shell I2 is centrally supported relative to outer housing wall ID by means of spacers 53, shown in the form of radial lugs, welded or otherwise united to the sections of the inner shell l2 and engaging outer housing wall l0. At the outlet end, the inner shell |2 is of progressively reduced diameter downstream, and terminates in a throat 41 snugly embraced by the neck 32 of the outer shell II, so that said inner shell I2 is firmly supported at this outlet end. The inner shell l2 aside from the head 40, is generally circular in cross-section, and is made of three sections 50, 5| and 52 coaxially mounted. The first or upstream section is cone shaped, and has its upstream end connected to the head 40 through the spray nozzle device 45. The shell section 5| is slightly conical. The upstream end 55 of shell section 5| is larger in diameter than the corresponding downstream end 56 of the upstream inner shell section 50, to form an expansion joint between the two inner shell sections 50 and 5|. The inner shell section 52 is of progressively reduced diameter downstream, and terminates inthe throat 41, as previously described. The sections of inner shell |2 may conveniently be formed of sheet metal, or thin plate by rolling or similar forming operations into the curved streamlined form shown and the longitudinal seams closed by welding.

For admitting air from the annular passage l5 into the zone l3, and into the zon I4, the inner shell I2 is provided with a series of successive stages of louvred air inlets 60, 60a, 60b, 60c, SM, 60c, 60;, 60g, 6072. and 602. In the embodiment of the invention now described ten of these The duct l l is shown elonstages employed in each cas will depend on the conditions. However it can be stated that within limits better results are usually obtained with a larger number of stages than with a smaller number of stages. I

Each of the primary air inlets 60 of the first stage comprises a tongue 62 usually integral with and cut out from the shell wall 50. The tongue 62 has a sectic. out off its free end to define an opening 63in the flat blank from which the shell section 50 is formed, as shown in Fig. '7, and is bent inwardly after the blank is rolled to define the port 64. Thus the tongue 62 serves as a guide to lead the air towards the interior of the inner shell; Inside the inner shell 50 and along the circumferential downstream edge of the port 64 is a curved deflector vane 65, welded to said edge. Vane 65 is substantially the same length as the circumferential width of the port 64, and constitutes a segment of a tube curved to follow the peripheral curvature of the shell section 50. The vane 65 has its ends sloped radially as shown in Fig. 5, and is transversely curved to direct the air admitted through the corresponding port 64 in a reverse upstream direction towards the zone of fuel injection, and obliquely of the axis of the injected fuel zone, thus promoting exceptional turbulence in the primary combustion region. i

Each of the primary air inlets 60 has on each side a substantially ovate Shroud-plate 61, with its apex end substantially sharp, and with its broader end conforming substantially with the transverse curvature of the vane 65, t cover one end of said vane. Shroud-plate 6'! has one of its tapering sides extending along the side edge of the port 64, and its other tapering side extending into the interior of the shell section 50 beyond the tongue 62, and is rigidl secured to the end of the vane 65, to the side of said tongue, and to the inner surface of said shell section by welding along contacting or abutting edges. The two shroud-plates 61 at each primary air inlet 60 will slope radially and flank the corresponding tongue 62 and vane 65 as shown in Figs. 4 and 5, and will serve to prevent spillage of air along the ends of said vane. The air is thereby channelled into the interior of the combustion chamber in well-defined streams having predetermined fiow characteristics.

The shroud-plates 61 also prevent the flow of liquid fuel along the inside walls of the shell l2 and out through the air ports 64 into the annular space l5, where burning fuel would defeat the cooling function of the annular arrangement, would upset the operating conditions for which the unit is designed and thereby reduce its efilciency and would create a fire hazard. To prevent the accumulation of the liquid fuel in the pocket defined by the curved van 65, said vane has an aperture 68 through which liquid fuel can readily escape. The incoming air passing through the port 64 and directed against the vane 65 helps to blow any liquid fuel deposited in said vane through the aperture 68.

The air guiding structures of the other stages of air inlets 60a, 60b, 60c, 60d, 60c, 611], 60g, 60h and 601', are similar to those described in connection with the first stage of air inlets 60, except that the dimensions are diflferent, and in the later stages, the side shroud-plates may be absent,

' and the curved vanes may not be apertured for the escape of liquid fuel. The different stages of air inlets are'correctl sized to compensate for the decrease in volume and pressure of the air in the annular passage l5 progressively downstream, to effect the proper distribution of the air in the flame region, and to cause the injected air to follow a desirable predetermined pattern of tur-bulence and diffusion. As the air inlets extend downstream, the tongue guides thereof are preferably progressively bent inwardly of the inner shell l2 to an increasing extent, to progressively increase the effective area of the air inlet.

In the section of the combustion chamber where the later stages of air inlets are located, the fuel is usually all in such condition. and the flame so spread out that the shroud-plates and the apertures in the curved vanes are not necessary. If conditions require it, however, these features can be applied to all the stages of air inlets.

A comparatively large number of small air inlets are preferably employed instead of a small number of larger air inlets, as thereby better results and more stable operation are obtained. Highly localized and concentrated air streams have a tendenc to extinguish the flame, especially at low fuel deliveries. By providing a large number of small inlets, the flame-quenching tendency is reduced to the point Where stability of the flame is maintained within a wide operating range.

For this purpose, and by way of example, the combustion chamber described contains thirty separat air inlets of three different sizes, disposed in ten spaced transverse regions: of said chamber. Each of these transverse regions or stages contains three air inlets spaced 120 apart. The air inlets of one stage are circumferentially staggered with respect to the air inlets of adjoining stages, and in the initial stages, the air inlet of one stage is displaced 60 withrespect to the air inlets of adjoining stages. In the later stages, the angular relationship of the air inlets between successive stages may be different, and may be relatively displaced 30 apart as shown in Fig. 6 according to the pattern of airdistribution desired.

Fig. 6 shows the development of a blank 5 l a designed to form the inner shell section 5|, and cut out to provide the seven stages of air inlets 60c, 60d, 60e, 60f, 60g, 60h and 6M. Blank 51a is slitted and cut, as in the case of blank 50a, and may be rolled and completed as described in connection with the blank 50a to provide these seven stages of air inlets.

Fig. 7 shows the development of a blank 50a designed to form the shell section 50, and cut out to provide the three banks or stages of air inlets 60, 60a and 6%. To that end, the blank 56a has a plurality of pairs of radial slits 15. The slits 15 of each pair define therebetween a tongue 62a from which the deflector 62 is formed. This tongue 62a is shortened by cutting off its outer end to form the opening 63 in the blank. The

blank 50a cut and slitted as shown and described,

is rolled in conical shape and welded along its longitudinal seam. The tongue 62a may then be bent inwardly to define the air guides and the vanes and shroud plates welded in position to complete the air inlets 60, 60a, and 60b.

For initiating the flame. there is fitted into the peripheral wall of the outer housing wall H) a spark plug extending through an opening 8| in the shell section 50. Spark plug 80 is desirably operated only sufficiently long to properly initiate ignition. Thereafter, primary combustion will continue without the aid of the spark plug. However, if desired, the operation of the spark the casing of the spark plug 80, a low pressure region is created on the downstream side of said casing, thus tending to cause the liquid fuel in the inner shell II to seep through the opening 8| into said space. To avoid this condition, there is provided a saddle 83 for the spark plug 88 secured to the outside of the shell section 50 by welding, and opened only at its upstream end. The air flowing into the chamber 84 defined around the spark plug 88 by the saddle 83 maintai'ns said chamber under full air pressure, and thereby prevents seepage of the liquid fuel through the opening 8|. The spark plug 80 may be of a usual type having a casing which defines an air passage for cooling the porcelain insulator, and which is provided on its upstream side and in the saddle chamber 84 with a hole 85 constituting the inlet of said air passage.

In the operation of the combustion unit, as the air flows through the annular Space I5 from the compressor, part of the air is diverted through the first stage of inlets 60, and is reversely defiected obliquely back into the combustion zone l3 towards the point of fuel injection. portions of the air further downstream in the annular space l5 are diverted through the second stage of air inlets 68a, and are reversely deflected obliquely back into the combustion zone l3 towards the point of fuel injection. The air streams projected into the combustion zone I3 through the two close sets of air inlets 80 and 68a, assume somewhat the form of a vortex ring around the injected fuel cone. Sufiicient amount of the fuel from this cone is drawn and diffused towards the annular axis of the air vortex ring, to form at said axis an inflammable mixture. This mixture created around the fuel cone forms a pilot flame by which ignition is continuously maintained, even though the operation of the spark plug 88 should be discontinued.

The ignited stream, rich in fuel, is projected from the combustion zone |3 towards the combustion zone It, where it impinges and is thoroughly, rapidly and intimately intermixed with the progressively injected air streams from the air inlets 80b and from all the other air inlets further downstream, to form therewith flame propagating mixtures. The air inlets 60b, 60c, 60d, Bile, 68f, 60g, GM and 882', as well as the air inlets 60 and 68a, are designed to direct the air into the combustion chamber in a direction obliquely countercurrent to the general direction of flow in said chamber, and into the active flame region of said zone.

As a result of the staggered arrangement of the air inlets lengthwise and circumferentially of the shell l2 as described, the combustion is not confined to the center of the chamber but is effectively distributed throughout the cross-section thereof. As the flame is extended or propagated axially along th combustion chamber, it is spread, fanned out, or distributed outwardly in different substantially radial directions by the admission of air at one transverse inlet region Other or stage of the chamber, and then spread or distributed outwardly in substantially radial directions in staggered relationship with respect to the first-mentioned directions by the admission of air at the next succeeding transverse inlet region or stage. This promotes turbulence in the zones of the chamber where it is most desirable and most efiective, and thereby causes complete, thorough mixing of the fresh air with the fuel elements of the. burning mixture in a comparatively small space, creates a short intense flame in the interior of the chamber, and assures complete combustion even at maximum loads before the gas stream reaches the outlet end of the unit. The converging character of the inner shell |2 at its outlet or exhaust section 52 serves to impart to the exit gases the necessary velocity, according to the use to which these gases are to be put. I

Not all of the air which flows through the annular flow chamber I5 is diverted in the interior of the combustion chamber. Some of it is allowed to pass completely along the annular flow passage i5, and is discharged into the combustion chamber outlet through holes 90 near the throat 41 of inner shell section 52 to aid in the control of the outlet temperature.

The circular cross-section of the shell l2 assures a uniform distribution of air entering into the combustion chamber at any transverse region thereof; this promotes a more uniform flow of air into the chamber, and thus contributes to flame uniformity and stability.

The general conical shape of the shell sections 58 and 5| serves to present a surface to the air flowing through passageway I5 which is at an angle to the direction of the flow of said air. As a consequence, a portionpf the kinetic energy or impact head of the entering air is employed to force the air to enter the air inlets, thus decreasing the air stream total pressure loss in the combustion unit. The conical angle of the shell sections 50 and 5| is so selected as to provide a minimum clearance 9| between the two shells II and I2 at the extreme downstream end of the active combustion part of the unit. The radial depth of this minimum clearance 9| controls the amount of air which by-passes the combustion chamber.

The angle of the cones of the shell sections 50 and 5| as well as the depth of the depressions of the air inlets as determined by the angle of inclination of the guide or tongue plates therein, determine the air flow characteristics in the regions of said air inlets, and consequently serve to control the quantity and velocity of air entering each air inlet.

The outer shell H, which acts as a container for the assembly, and is therefore the stressed member, is cooled by the entering air as described. The inner shell I2 containing the flame, is also cooled and is under little or no stress. As a result, the entire assembly can be fabricated from thin sheets of heat-resistant material.

Since the air is injected into the interior of the combustion chamber through depressions in the conical surfaces of the shell sections 50 and 5| and said surfaces are straight and free of obstructions, a minimum of turbulence is created in the annular air stream in the space |-5 adjacent to each air port. The preservation of the. sense of direction of flow of the air in the space l5 resulting from this condition conserves to a maximum the impact head of said air, and consequenttion unit. p

The combustion unit of the'present invention can be made to effectively affordoutlet temperatures; ranging from about 200 F.to' as high as 3000 F. The embodiment shown is best adapted to provide outlet temperatures ranging from 300, F, to a maximum of 1800'F.

Operating test data indicate that the,com-

bustion'unit of the type shown in Figs. 1-7, which is particularly adaptedfor installation in an aircraft engine, performs most satisfactorily over theentire range of performance conditions dictated bythe most extensive engine requirements. This performance range comprises a maximum heat release rate ofover fifty times the minimum heat release rate, amaximum combustion chamber pressure better than twenty-five times the minimum combustion chamber pressure, and a maximum air flow rate better. than fifteen times the minimum air flow rate. Smooth, stable, steady, dependable, soot-free performance was observed under all conditions, with a thermal efficiency measured close to 98% at every operating point. l

As many changes can be made in the above apparatus, and many apparently widely different embodiments of this invention can be made without departing from the scope of the claims, it is intended that all matter contained in the above 1 description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense;

What is claimed is:

l. A combustion unit comprising a combustion chamber, the peripheral wall of which is provided with openings spaced therealong and circumferentially thereof, means for creating an inflammable, fuel-rich, fuel-air mixture, igniting said mixture and discharging the resulting ignited mixture rich in fuel elements into said chamber, a housing around said combustion chamber and defining therewith an annular airflow passage, said openings conducting a major portion of the ai from said passage into said chamber for combustion therein, a curved vane entirely inside said chamber on the downstream end of each opening for deflecting the air admitted through said opening in the form of a jet generally countercurrent to the flow of said ignited mixture in said chamber to create thorough mixing in said chamber of said air and the ignited 4 openings spaced therealong. and circumferentially' thereof for the admission of a major portion of said air stream for combustion, means for creating an inflammable, fuel-rich, fuel-air mixture, igniting said mixture and discharging the resulting ignited mixture rich in fuel elements into said chamber for progressive combustion, a curved vane entirely inside said chamber on the downstream end of each opening for deflecting the air admitted through said opening in the form of a jet generally countercurrent to the flow 1y minimizes the air pressure loss in the combusof said ignited mixture in said chamber to create thorough mixing in said chamber of said air and the ignited mixture-to assure substantially complete combustion therein, and a guide plate for saidvane cut out from said peripheral chamber wall and integral therewith along the upstream end of each opening, said guide plate extending in a general downstream direction'from said upstream end and inclined inwardly from said end with respectto said peripheral chamber wall for directing the air admitted into said! opening towards said vane.

3. A combustion unit comprising an elongated combustion chamber, the peripheral wall of which is provided with openings spaced therealong and circumferentially therearound, means for creating an inflammable, fuel-rich, fuel-air mixture, igniting said mixture and discharging the result ng ignited mixture rich in fuel elements into said chamber, a housing surrounding said combustion chamber and defining therewith an annular passage for conducting an air stream in the direction of the flow of said ignited mixture, said openings direct ng the major portion of said air stream into said chamber for combustion pro-' gressively, a curved vane entirely inside said chamber on the downstream end of each opening for deflecting the air admittedthrough said opening in the form of a jet generally counter-' current to the flow of said ignited mixture in said chamber to create thorough mixing in said chamber of said air and the ignited mixture to assure substantially complete combustion therein, and a pair of shroud-plates in said chamber on O posite sides of each vane.

4. A combustion unit comprising a combustion chamber, a housing surrounding said chamber and defining an annular passage for an air stream the peripheral wall of said chamber being provided with openings spaced therealong and circumferentially thereof for the admission of a major portion of said air stream for combustion, means for creating an inflammable, fuelrich, fuel-air mixture, igniting said mixture and discharging the resulting ignited mixture rich in fuel elements into said chamber for progressive combustion, a curved vane entirely inside said chamber on the downstream end of each opening for deflecting the air admitted through said opening in the form of a jet generally countercurrent to the flow of said ignited mixture in said chamber to create thorough mixing in said chamber of said air and the ignited mixture to assure substantially complete combustion therein, a guide plate extending in a general downstream direction from the upstream end of each opening and inclined inwardly from said end with respect to said peripheral chamber wall for directing the air admitted into said opening towards said vane, and a pair of shroudplates in said chamber on opposite sides of each vane and each corresponding guide plate. l

5. A combustion unit comprising an elongated combustion chamber having a peripheral wall section rolled from a fiat shell blank and slitted to define a series of tongues integral with said wall section along the upstream end of said tongues, means for creating an inflammable, fuel-rich, fuel-air mixture, igniting said mixture and discharging the resulting ignited mixture rich in fuel elements into said chamber for progressive combustion, said tongues being bent inwardly at their upstream ends at an acute angle with said wall section to define openings in said wall section for the admission of combustion air and to adapt combustion in the form of jets, to bring about a thorough mixing of the added air and burning fuel-air mixture and to assure substantially complete combustion therein.

6. A combustion .unit comprising an elongated combustion chamber, the peripheral wall of which is provided with openings spaced therealong and circumferentlally thereabout, means for creating an inflammable, fuel-rich, fuel-air mixture,

' igniting said mixture and discharging the resulting ignited mixture rich in fuel elements into said chamber, a housing surrounding said combustion chamber and defining therewith an annular passage for conducting an air stream in the direction of flow of said ignited mixture, said openings directing a major portion of said air stream into said chamber in the form of jets to bring about a thorough mixing of the added air and burning fuel-air mixture and to assure substantially complete combustion therein, a curved vane entirely inside said chamber on the downstream end of each opening for deflecting the air admitted through said opening generally countercurrent to the flow of said ignited mixture in said chamber, said vane having an aperture to permit escape of liquid fuel from said ber for progressive combustion therein. a vane associated with each of said air inlets interiorly of said chamber for directing combustion air from said annular air flow passage in the form of jets generally counter current to the flow ofignited materials in said chamber.

9. A combustion unit having an air intake end and an exhaust end comprising a combustion chamber having a peripheral wall section flaring in a direction from said air intake end'toward said exhaust end and presenting a substantially smooth outer surface, an outer housing for said chamber one end of said housingdeflning an air intake, said housing being concentrically spaced fromsaid chamber to form therewith an annular air flow passage, the end of said chamber adjacent said air intake being, closed, unitary means adjacent said closed end for introducing all of the fuel burned by said unit into said chamber for progressive combustion therein, a plurality of circumferentially and longitudinally spaced air inlets formed in the flaring wall section of said chamber for the successive admission of a major portion of the air flow from said air flow passage into said chamber for progressive combustion therein, a vane associated with each of said air inlets interiorly of said chamber, each vane into said chamber, and guide means for directing the air admitted through each of said openings towards the corresponding vane.

'7. In a combustion unit, a combustion chamber having a peripheral wall with openings spaced therealong and circumferentially therearound for directing combustion air into said chamber, means for injecting fuel into one end of said chamber, a housing around saidchamber and defining with said peripheral chamber wall an annular air flow passage, a fuel igniting unit passing through said passage and through an opening in said chamber wall and projecting into said chamber in position to ignite the fuel injected into said chamber, and a saddle around said unit in said passage and mounted against said peripheral chamber wall, said saddle being opened to said passage on the upstream side to maintain the region around said unit adjoining said chamber wall under suflicient pressure to resist seepage of fuel oil through the opening of said chamber wall through which said unit extends.

8. A combustion unit having an air intake end and an exhaust end comprising a combustion chamber having a substantially smooth outer surface, an outer housing for said chamber concentrically spaced therefrom, one end of said housing defining an air intake, said chamber flaring towards said housing in a direction away from said air intake whereby said chamber and said housing cooperate to form an annular air flow passage having a progressively smaller area from said air intake end toward said exhaust end, a plurality of circumferentially and longitudinally spaced air inlets formed in the flaring wall section of said combustion chamber for the successive admission of a major portion of the air flow from said air flow passage into said chamof said vanes being capable of directing combustion air from said annular air flow passage in the form of jets in a direction generally counter current to the normal flow of fuel in said chamber to bring about a thorough mixture of said combustion air and said fuel and to assure substantially complete combustion therein.

10. A combustion unit having an air intake end and an exhaust end comprising a combustion chamber having a peripheral wall section flaring for a predetermined distance and constricting for a predetermined distance following said flaring portion to form an exhaust opening, said chamber presenting a substantially smooth outer surface, an outer housing for said chamber, said housing being concentrically spaced from said chamber to form therewith an annular air flow passage, said housing being so formed that it approaches said chamber as it extends from said air intake end toward said exhaust end, a plurality of circumferentially and longitudinally spaced vaned air inlets formed in the flaring wall section of said chamber for the successive admission of a major portion of the air flow from said air flow passage into said chamber for progressive combustion therein, said vanes being located interiorly of said chamber and being adapted to direct the flow of air entering said air inlet in the form of jets in a direction in said chamber which is substantially opposite to the direction of flow of air in said annular air flow passage.

11. In a combustion unit having a combustion chamber with a substantially smooth outer surface, an outer housing for said chamber concentrically spaced therefrom and forming with said chamber an annular air flow passage around said chamber, the combination with said chamber of a plurality of air inlets formed in the peripheral wall of said chamber and extending inwardly of said chamber whereby air is permitted to flow unimpeded around said combustion chamber, each of said air inlets comprising a tongue extending inwardly of said chamber from'the peripheral wall thereof in a downtream direction for the successive admission of a major portion of the air flow from said air flow passage into said chamber for progressive combustion therein,

a vane associated with the downstream end of said air inlet and located entirely within said chamber, and-a pair of shroud plates joining the ends of said vane and the sides of said tongue. said shroudplates and said tongue serving to guide combustion air from said annular air flow passage to said vane, said vane being adapted to change the direction of the combustion air thus directed against it to a direction generally counter current to the direction of air in said annuiar air flow passage.

'12. A combustion unit comprising a combustion chamber having a conical peripheral wall section flaring downstream, an outer housing for said chamber defining with said chamber an an nuiar air flow passage extending therealong, for creating an inflammable, iuei-rich, mixture, igniting said mixture and discharging the resulting; ited mixture, and a series oi varied openings in said conicai chamber section spaced aiong and circuniierentiaiir around said chamber Wait section and communi with said passage tor the successive admission or a major portion oi the air iiow from said. air flow into said chamber for pro gressire combustion therein, the vanes associated with openings being ioeateci entirety Within said chamber and. so positioned with respect to openings that the r deflect combustion air entering chamber through said openings in term of iets in a direction generaiiy counter corrent to the new oi said ignited mixture in said chamber to create thorough mixing at said com bastion air and said ruei eiements and. to assure substantially compiete combustion therein, the nennherai Waii or" said housing around sairfi Sit chamber wall section being generally cylindrical to cause the air in said passageto flow in a general direction tending to approach said chamber wall section, whereby a portion of the kinetic energy of the air in said passage is employed to force said air into said openings, the outer surface of said conical chamber wall section resenting a continuous conical surface substantially free from obstructions in the regions of said openings in said annular passage so that air can pass through said passage with minimum loss of kinetic energy.

RIPEH ERENWEN mm The ioiiowing references are at record in the iiie of this patent:

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