US3306333A - Air spray combustor - Google Patents

Description

Feb. 28, 1967 c, MQCK 3,306,333

AIR SPRAY COMBUSTOR Filed March 31, 1964 5 Sheets-Sheet 1 I NVE NTOR.

ATTORNEY Feb. 28, 1967 F. c. MOCK AIR SPRAY COMBUSTOR Filed March 51, 1964 3 Sheets-Sheet 2 INVENTOR.

Feb. 28, 1967 F. c. MOCK AIR SPRAY COMBUSTOR Filed March 51, 1964 5 Sheets-Sheet 5 INVENTOR.

ATTOENEY United States Patent v Ofilice 3,3fi6,333 Patented Feb. 28, 1967 3,306,333 AIR SPRAY COMBUSTOR Frank C. Mock, Los Angeles, Calif., assignor to The Bendix Corporation, South Bend, Ind., a corporation of Delaware Filed Mar. 31, 1964, Ser. No. 356,169 Claims. (Cl. 158-4) The present invention relates to a combustor and more particularly a combustor of the flame tube type, with toroid-a1 or smoke ring type of gas circulation in the primary zone.

It is an object of the present invention to provide a combustor design providing means through a wide range of capacity for efliciently heating land/0r vaporizing fuel prior to ignition.

It is still another object of the present invention to provide a combustor design having a combined fuel and air injection or atomization nozzle for more efficiently atomizing and mixing fuel and air quantities for the combustion process.

A further object is to provide improved means for quick positive starting from an electric spark.

The foregoing and other objects and advantages will become apparent in view of the following description taken in conjunction with the drawings wherein:

FIGURE 1 is a cross-section view taken longitudinally through a preferred embodiment of a combustor of the present invention;

FIGURE 2 is a lateral cross-section through the same device on line 22 of FIGURE 1;

FIGURE 3 is a partial section view of a modified form of my combustor; and

FIGURE 4 is an explanatory cross-section through the fuel spray and starting nozzle.

It is well known that combustion proceeds slowly between a relatively cool fuel spray of low volatility and a cool air charge; and that the rate of spread of combustion can be increased by additional transfer of heat from already burning portions of the gas to the unburned portions. Stated in another way, flame tends to blow-out when unburned charge is introduced too rapidly to the flame front or combustion interface, in excess of the rate at which the needed ignition heat can be supplied. But if adequate heat is supplied-as with my design, the air turbulence may be increased to further increase the combustion r-ate.

One especially desirable characteristic of my construction is that the volume of flame increases and decreases with the fuel feed rate, therefore tending to hold a high primary zone temperature at both low and high fuel feed rates.

Another good characteristic of this device is that the flame body tends to locate next to the breech end of the combustor at all times, at the point where the fuelis delivered; keeping the wall hot, keeping combustion stable at low deliveries, preventing deposition of liquid fuel on the wall, and avoiding accumulation of carbon.

One problem heretofore is that up to this time the toroid construction has given no assistance in initial i-gnition or cool starting, since its outside shell is a region of high velocity. In the present invention, this is improved by locating the starting fuel feed and ignition points in the quiescent central region of the vortex ring, as will be later shown.

Partial solutions of these problems have been set forth in my copending commonly assigned application Serial No. 166,337, filed January 15, 1962, now US. Patent 3,229,464, in which improved recirculation means are provided for recirculating burning particles back into the unburned gases.

As compared to the prior disclosure, the present invention provides both a more positive and exact control of the toroid air circulation and a better atomized fuel delivery. Another improvement is in starting, by directing an air atomized fuel spray against an ignition spark, both of which are located in a quiescent region of the combustion chamber, from which the flame can propagate readily to the high velocity region.

Referring to FIGURE 1, 10 designates my combustor generally, which includes an outer shell or casing 12 having an air entrance opening 14 for connection with a source of pressurized air, not shown; and also containing integrally the combustor cap or dome 26. Casing 12 is closed at one end by flange 16 of outlet tubing 17, and at the other end by cover 18. A flame tube 20 of generally cylindrical configuration threadedly engages the inner diameter of combustor dome 26 and has a downstream end 24 projecting into outlet tubing 17.

Atomizing and toroid air flow is admitted at connection 11, at about 10 pounds per square inch higher pressure than supply to entrance 14. Fuel for both normal combustion and starting is supplied at connection 15, at a pressure regulated a known amount above that of the air pressure in casing 12.

The combustor cap or dome 26 is integrally mounted in casing 12. Its inner contour is generally dome shaped as illustrated. The precise configuraiton is not critical except that it must be so shaped as to accommodate the air flow patterns as will be later described. An expanding outlet contour similar to that shown in my prior application Serial No. 166,337 [may also be used.

Adjacent combustor cap 26, a series or ring of primary air holes 28 are spaced around the flame tube 20 in a transverse plane to admit pressurized air from casing 12 to the interior of the flame tube. The space within the flame tube and combustor ca p bounded at the right by the plane intersecting holes 28 and on the left by the end wall of the combustor cap defines a primary combustion zone where there is a heterogeneous but rich fuel/air ratio and where initial combustion occurs. The holes 28 may be inclined rearw-ardly towards the combustor cap or may be directed straight in without inclination. I have found inclinations from 0 to approximately 15 to provide good performance depending on the objectives desired.

The inner tubular fuel nozzle member 38 has a longi tudinal fuel transmitting passage 42 formed therein which contains a fuel metering restriction 44. The outer configuration of member 38 has three distinct areas as follows: First, a threaded portion 46; secondly, a reduced diameter portion 48 for forming an annular air passage 50; and thirdly, an enlarged upset fuel distributing head 52 having a series of transversely drilled passages, one of which is designated by numeral 54. The passages 54 intersect the longitudinal fuel passage 42 and also form a series of annularly arranged fuel ejecting opening 56 delivering around the outer periphery of distributing head 52. The right end of outer tubular member 36 is contoured to form an annular air opening or to define conical or annular air nozzle 60- immediately adjacent and concentric with fuel openings 56. Air nozzle 60 is connected to passage 50 which in turn communicates with atomizing air supply inlet 11.

The combustor design is completed with the provision of secondary or dilution air openings 64 formed in the flame tube wall downstream of the primary openings 28 and within casing 12.

Operation Continuous operation of the device can be best understood by consideration of the air and fuel patterns during the combustion process.

Primary air is supplied by a differential pressure of the order of 5 pounds per square inch at full power; through the openings 28 which are equally spaced around the flame tube wall. The air is ejected inwardly radially, causing a low static pressure of about 0.1 of the magnitude of the differential across openings 28 and 64, to build up along the axial center line of the flame tube where the streams 28 converge. This static pressure, and the slight inclination of the holes 28, cause a portion of the inflowing air 29 to deflect and flow axially of the flame tube leftward or upstream as indicated by the arrows. As this weak flow approaches the breech of the combustor it is acted upon by the small but more energetic flow through 60, causing it to flow outward and parallel with the breech wall, and thence in a downstream or righthand direction as guided by the inner contour of combustor dome 26.

Note that the axial leftward flow 29 and the outward righthand flow through 60 tend to form a dynamic couple which is very effective in setting up the desired clean cut toroidal air flow.

Fuel is ejected in an outwardly extending spray pattern through fuel openings 56. The air ejected from opening 60 is directed in a generally wide angle or frusto-conical pattern which intermixes with the fuel spray at a point closely adjacent openings 56 to promptly initiate atomization or intermingling of the air and fuel quantities, causing quick dispersion and atomization of the fuel droplets. This action is assisted by the aspirating effect of the high velocity atomizing air flow issuing from opening 60 which creates a low pressure region at the fuel nozzles 56 causing the fuel droplets to be sucked into the air stream.

Centrifugal force and general air turbulence causes the spray droplets to strike the wall of the dome 26, where some heating, vaporization, combustion, and formation of droplets takes place. As this mixture continues on its righthand path it encounters the primary air holes 28, where a first portion of it, now bearing heat, will be picked up and recirculated through region 29 back to the breech and again around the toroid. The greater portion of the air issuing from the dome however will pass between the holes 28 and downstream into the flame tube where it merges with dilution air from secondary holes 64. Thus there is a continuous feed of new air, recirculated air, flame, and burning drops leftward to the breech 29 and also a continuous feed of this same sort of mixture, rich in fuel air ratio downstream to the holes 64. Meanwhile there is a quite hot, fuel-rich, low velocity, smoke ring vortex in the region 89, which constitutes a continuous source of reignition.

The atomizing air stream from opening 60 further accomplishes an additional and important object, which is by induced depression to cause the vortex and the zone of primary combustion to nest, under all combustion conditions, close to the breech wall at the lefthand of the combination chamber. 1 have found that too weak toroidal circulation may allow the flame to move out of this desired area as the air and fuel quantities are varied, resulting in a cool breech wall, poor combustion efficiency and even permitting the flame to blow out. Hence the value of positively established and controlled toroidal conditions.

Insofar as other design considerations permit, the relative angular spacing of fuel orifices 56 and air recirculation orifices 28 should be such that they lie in common planes through the axis. In other words, the orifices 28 should preferably be downstream of orifices 56 for best combustion.

FIGURE 2 shows a section on line 22 of FIGURE 1, and illustrates the starting system (with fuel channels somewhat over scale for clearness). 80 represents the ignition points of the spark plug, which is located approximately at center of the whirling gas vortex.

81 represents generally an air atomizing jet, discharg ing toward the spark plug gap. Design objectives are:

(1) To have as fine a spray as possible.

(2) To have the distance between the nozzle and spark as long as possible, since diffusion and vaporization in= crease, and spray velocity decreases, with distance.

(3) To have the spray path follow a region of low velocity, in order to extend the distance of flame propagation.

Essentially the atomizer consists of three elements, the air pressure nozzle 83 receiving air from connection 11 and duct 62; intermediate nozzle 84 which receives fuel from inlet 15 and duct 85 to deliver it round the outside of nozzle 83; and common delivery nozzle 86. All this is usual air atomization practice.

Referring now to the embodiment of FIGURES 3 and 4, this has many parts in common in FIGURES 1 and 2, and bears the equivalent numerals with prime mark notation added. The nozzle assembly is modified by the addition of an intermediate tubular member 66 which now serves to define the series of slot openings 60 within the enlarged end 52' of the inner tubular member 38', which may give any desired angle or arrangement of atomized fuel discharge relative to the vortex.

A second and annular air opening 68 is defined by the right ends of outer and intermediate tubular members 36' and 66 respectively, which, while concentric with spray slots 60 is spaced leftwardly therefrom to provide a wide angle air flow pattern parallel to the rear wall as required for best toroidal air flow. The area of openings 68 is preferably greater than that of 60, to diminish interfer-- ence of the latter with toroidal circulation. The inter= mediate tubular member has a thin section 70 which defines a first air passage 50' with the inner tubular mem ber 38 for supplying atomizing air to openings 60 and a second passage 72 with the outer tubular member 36' for supplying air to opening 68. These passages are con nected to a separate and preferably higher pressure air supply by passages 62 formed in member 36' and passages 74 formed in the thin section 70. An air connect ing ring 76 is disposed concentrically over tubular member 36' and has an air conduit 78 for connection with an air supply. Connecting ring 76 is held in position by jam nut 80 which is threaded over tubular member 36' and tightened against ring 76.

The design of the fuel distributing head 52' is modified in that the fuel passages 54 are connected with the atomizing air passage internally of the nozzle head so that openings 60' eject a partially atomized fuel-air mixture. Additionally there is provided a starting atomizing passage 82 connected by passage 84 to fuel passage 42 and by passage 83 to an atomizing air passage. Starting atomizing passage 82 is aligned to eject a fuel-air mixture directed towards spark plug 88 having electrodes extending into the combustor and somewhat into the core of the torus. The spark plug location is preferably upstream (to the left) of primary air holes 28 in the zone of primary combustion while spaced as far as conventionally possible from the fuel-air nozzle to facilitate ignition.

In operation, the FIGURE 3 embodiment functions similarly to that described for the FIGURE 1 device with the following exceptions. First, a separate air nozzle 68 is provided solely to assist the primary air holes 28' in producing a strong toroidal circulation whereas in the FIGURE 1 device the nozzle 60 provides a double function of supplying atomizing air and air for toroidal circulation. Second, with the FIGURE 3 arrangement a smaller percentage of the initial fuel discharge will be thrown on the dome walls. Third, an atomizing fuel-air jet, integral with the main jet is provided for starting. This jet has a maximum effect at starting and its location and configuration are subordinated to this requirement; however, as shown, it may be used to supply a share of the main fuel flow at all times, in which case this fuel flow will help to continually cool the spark plug points.

While I have shown two specific embodiments of my in- Vention, it will be obvious to those skilled in the art that 'various additional modifications may be made without departing from the inventive concept, and I intend the appended claims to cover all such modifications as fall within their scope.

I claim:

1. A combustor comprising:

a cylindrical flame tube having a generally-closed upstream end and an opened downstream end;

a ring of primary air holes formed in the side of said flame tube admitting pressurized air, producing toroidal air circulating within said upstream end;

a fuel-air nozzle extending through said upstream end at the approximate axial centerline of said flame tube;

said fuel-air nozzle having passage means adapted to direct a fuel-air mixture into said flame tube to assist toroidal circulation;

a spark plug having electrodes extending into said flame tube intermediate said closed upstream end and said ring of primary air holes and fuel spray ignition means comprised of an additional fuel ejecting passage, formed as part of said fuel-air nozzle, operative to direct a fuel spray toward said electrodes.

2. A combustor comprising: a cylindrical flame tube having a generally closed upstream end and an open downstream end, a ring of primary air holes formed in the side of said flame tube admitting pressurized air to produce toroidal air circulation Within said upstream end, a fuelair nozzle extending through said upstream end at the approximate axial centerline of said flame tube, said fuelair nozzle operative to supply an atomized fuel-air mixture in an expanding frusto-conical pattern into the zone of toroidal air circulation, said fuel-air nozzle further operative to supply a wide angle air stream along the flame tube wall operative to assist toroidal air circulation.

3. A combustor comprising: a cylindrical flame tube, a combustor cap secured to one end of said flame tube substantially enclosing one end and forming a primary combustion zone within said flame tube, a casing exterior of said flame tube enclosing said one end, said casing including an opening for receiving pressurized combustion air, a ring of primary air holes formed in the side of said flame tube adjacent said combustor cap for permitting the flow of primary combustion air into said flame tube, said ring of primary air holes located in a plane transverse to said flame tube centerline to initiate toroidal air circulation within said primary combustion zone, a combined fuel-air nozzle projecting centrally through said com bustor cap and extending into said primary combustion zone, said nozzle operative to eject a frusto-conical air pattern within said primary combustion zone assisting toroidal circulation of primary air, said fuel nozzle further operative to eject a fuel-air mixture in an expanding frusto-conical spray pattern causing dispersion and atomization of fuel.

4. A combustor comprising: a cylindrical flame tube, a combustor cap secured to one end of said flame tube substantially enclosing one end and forming a primary combustion zone within said flame tube, a casing exterior of said flame tube enclosing said one end, said casing including an opening for receiving pressurized combustion air, a ring of primary air holes formed in the side of said flame tube for permitting the flow of primary combustion air into said flame tube, said ring of primary air holes located in a plane transverse to said flame tube centerline to initiate toroidal air circulation within said primary combustion zone, a combined fuel-air nozzle assembly including inner and outer concentric tubular members, said combined nozzle assembly projecting centrally through said combustor cap and extending one end of each of said inner and outer tubular members into said primary combustion zone, said inner tubular member including fuel passage means formed therein terminating with a series of annularly arranged openings formed in the end of said inner tubular member extending within said primary combustion zone, said outer tubular member having an end closely spaced to said inner tubular member within said combustion zone to form an annular air opening concentric and adjacent said annularly arranged openings operative to supply a Wide angle air pattern assisting toroidal air circulation, air passage means formed intermediate said inner and outer tubular members connected to said annular air opening, at least one opening formed in the side wall of said outer tubular member connecting said air passage means to a pressurized air source.

5. A combustor comprising: a cylindrical flame tube having a closed upstream end and an open downstream end, a ring of primary air holes formed in the side of said flame tube admitting pressurized air within said closed upstream end, a combined fuel and air nozzle extending through said closed upstream end at the approximate axial centerline of said flame tube, said fuel and air nozzle having a fuel distributing head with a series of outwardly directed fuel passages, said combined fuel and air nozzle including a plurality of air passages connecting with said fuel passages, said plurality of air passages conically arranged to supply an atomized fuel-air mixture in an outwardly expanding frusto-conical pattern, and an annular air opening disposed intermediate said plurality of air passages and said closed upstream end of said flame tube operative to supply a wide angle air pattern assisting toroidal air circulation.

References Cited by the Examiner UNITED STATES PATENTS 2,195,025 3/1940 Couzinet 1584 2,199,771 5/1940 Young 15873 2,601,000 6/1952 Nerad -39.65 2,618,928 11/1952 Nathan 158-4 X 2,923,348 2/1960 Fraser 158-4 DONLEY J. STOCKING, Primary Examiner. ROBERT A. DUA, Examiner.

Claims (1)

1. A COMBUSTOR COMPRISING: A CYLINDRICAL FLAME TUBE HAVING A GENERALLY-CLOSED UPSTREAM END AND AN OPENED DOWNSTREAM END; A RING OF PRIMARY AIR HOLES FORMED IN THE SIDE OF SAID FLAME TUBE ADMITTING PRESSURIZED AIR, PRODUCING TOROIDAL AIR CIRCULATING WITHIN SAID UPSTREAM END; A FUEL-AIR NOZZLE EXTENDING THROUGH SAID UPSTREAM END AT THE APPROXIMATE AXIAL CENTERLINE OF SAID FLAME TUBE; SAID FUEL-AIR NOZZLE HAVING PASSAGE MEANS ADAPTED TO DIRECT A FUEL-AIR MIXTURE INTO SAID FLAME TUBE TO ASSIST TOROIDAL CIRCULATION; A SPARK PLUG HAVING ELECTRODES EXTENDING INTO SAID FLAME TUBE INTERMEDIATE SAID CLOSED UPSTREAM END AND SAID RING OF PRIMARY AIR HOLES AND FUEL SPRAY IGNITION MEANS COMPRISED OF AN ADDITIONAL FUEL EJECTING PASSAGE, FORMED AS PART OF SAID FUEL-AIR NOZZLE, OPERATIVE TO DIRECT A FUEL SPRAY TOWARD SAID ELECTRODES.

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