CA1220685A - Steam generator having a high pressure combustor having controlled thermal and mechanical stresses and utilizing pyrophoric ignition - Google Patents

Abstract

STEAM GENERATOR HAVING A HIGH PRESSURE COMBUSTOR
HAVING CONTROLLED THERMAL AND MECHANICAL STRESSES
AND UTILIZING PYROPHORIC IGNITION

ABSTRACT OF THE DISCLOSURE

A steam generator having substantial thermal capaci-ty for producing high quality steam used primarily for downhole steam generation in tertiary oil recovery.
Incorporated in the generator is a novel high pressure, high heat release combustor, utilizing high pressure gaseous fuel and compressed gas oxidizer such as air, wherein thermal and mechanical stresses on the combustor structure are controlled.
A method for controlling combustion induced mechani-cal stresses on the combustor through fluid injection is also disclosed. Disclosed designs provide substantially increased combustor life in "Downhole" Steam Generation service.
The burner employs an ignition technique utilizing gaseous injection of a pyrophoric compound such as triethylborane (TEA).

Description

BAC~GROUND OF THE INVENTION

This invention relates to steam generation by direct contact between high temperature gases produced by combustion of gaseous hydrocarbon fuels such as natural gas and an o~idizer such as compressed air and water. The invention also provides a method of igniting a high pressure gaseous fuel/oxidizer burner utilizing a pyrophoric compound with alternate combustor configurations. The disclosed steam generator is of improved construction and utllizes fluid injection for varying combustion processes in situ, resul~ing in substantially increased operational periods when generating steam for tertiary oil recovery in downhole combustion.

Techniques for thermal recovery of oil have been known Eor a substantial period of time. Although above ground steam generation and introduction into wells, also known as "steam drive", is in common use, the technique suffers from substantial limitations, particularly in deeper wells. Included in these limitations is the loss of heat due to long flow paths from the steam generator to the oil bearing strata or sands containing oil requiring steam injection for recovery.

Direct fired downhole steam generation such as disclosed in U.S. Patent 2,5~8,606, ~known as DFDSG) overcomes many of the above mentioned dif~iculties. U.S.
Patent 2,548,606 is typical of conventional DFDSG's.
However, the system disclosed typically displays substantial operating difficulties, culminating in short burner runs and substantially reduced "recovery".

~igh pressure combustion and steam generation encountered in downhole recovery also presents additional difficulties, including ignition, and corrosive deterioration o~ the burner assem~ly. Additional approaches to downhole recovery are disclosed in U.S. Patent 2,839,141.
This approach generates steam at the surface.

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~ 2 - ~2~8~

Known direct fired downhole steam generators have encountered certain operatina difficulties resulting in reduced operating times, and relatively short equipment life, particularly that of the combustor. An exam~le of 5 the substantially limited life of direct fired downhole steam generators (DFDSG) is contained in reports pub-lished by the Sandia National Laboratories, working under contract to the United States Department of Ener-gy. These reports, titled "Air/Diesel Steam Generator 10 Fuel Test Interim Report" dated June 10, 1982, and "Oxy-gen/Diesel Steam Generator Field Test Interim Report"
dated June 10, 1982, and Project Deep Steam Quarterly Reports October 1, 1981 - March 31, 1982, indicate the deterioration of a DFDSG. More particularly, damage to 15 areas adjacent to the combustor can and occurrences of "map" cracking are shown as examples of the deteriora-tion of known generator designs. A further difficulty pointing up the lack of reliability when utilizing glow pluas for ignition is also indicated in these reports.
20 Igniting the burner of a "downhole" generator in situ, as indicated above, is therefore an additional and sub~
stantial problem with known equipment.
U.S. Patent 3,456,721 discloses a DFDSG unit employ-ing a ceramic liner and conventional electrical iqni-25 tion. In situ li~e of the electrical ignitor and associ-ated difficulties are limited due to the high downhole fuel/oxidizer pressures resulting in limited actual com-bustion time downhole. Life of the ceramic liner dis-closed is also limited in the downhole environment.
As indicated above, ignition of the combustor uti-lized in high pressure downhole steam generators is dif-ficult and complicated. Difficulties arise since the energy required to ignite even stochiometric mixtures is great when both fuel and oxidizer mix at high pressures 35 and flow rates~ The conventional spark ignition at high pressures is impractical due to the distances from a _ 3 _ ~ 2 ~ ~ ~8 ~

power source, and the large sparking potentials required.
Vse of resistance heaters known as ~glow plugs" pro-vides the bulk of presently used ignitors and avoids 5 certain of the problems encountered. However, subse-quent high temperature combustion after ignition greatly reduces usable life of these units. Therefore, in order to provide economic and long term combustion "runs" of a downhole steam generator, a non-deteriorating source of 10 ignition energy as disclosed hereln is a substantial advance in the ignition art.
U.S. Patent 2,9~1,595 discloses a method and struc-ture for spontaneous ignition of a burner utilizing pre-mixed gaseous fuel/oxidizer. However, the ignitor dis-15 closed is a solid metal phosphide, requiring contactwith water in order to produce temperatures suf~icient for ignition of the fuel and air mixture. Utilizing a solid ignitor also requires use of an additional fluid and makes positioning of the igniting material di ficult 20 to introduce and/or control. In the pvrophoric tech~
nique disclosed, these shortcomings are overcome and precise introduction and control of an igniting mixture is provided.
It is therefore an object of this invention to pro-25 vide a direct fired downhole steam generator utilizingdesigns which minimize thermal and/or mechanical stress-es.
Tt is a further object of this invention to provide a direct fired downhole steam generator where combustion 30 pulsations are controlled, thereby minimizina structural fatigue of the burner components without sacrificing burner output or efficiency.
It is an additional object of this invention to pro-vide a method of controlling a direct fired downhole 35 steam generator through the use of injected fluids such as water, in order to modify the ongoing combustion pro-ces s ~2~

It is a further object of this invention to provide a direct fired downhole steam generator utilizinq natu ral gas as a fuel and air as an oxidizing agent, which overcomes difficulties encountered in presently uced 5 units through use of a construction providing improved ignition and subs~antially increased life of the incorpo-rated burner.
It is a further object of this invention to provide a high pressure combustor for a direct fired downhole 10 steam generator, utilizing high pressure gaseous fuel and compressed air as an oxidizer, which is ignited through the controlled introduction of a pyrophoric mate-rial.
It is a further object of this invention to provide 15 a method for effective and controlled introduction of a pyrophoric fluid for ignition of a high pressure combus-tor utilizing gaseous fuel and oxidizer.
It is a further object of this invention to provide a direct fired downhole steam generator having a high 20 pressure combustor and utilizing gaseous fuel, oxygen as an oxidizer, and ign~ted by controlled introduction of a pyrophoric fluid.

SUMMARY OF THE INVENTION
~5 The unsatisfactory life of known DFDSG burners has been discovered to be related to combined thermal strain due to combustion processes and generator feedwater injection, and mechanical forces applied to the combus-tor structure by hypersonic pulsations resulting from 30 high intensity, high pressure combustion. Ensuing fatigue failure has been clearly demonstrated.
Applicant's discovery provides a means to optimize combustor performance in order to provide required out-put, high overall efficiency, and substantially 35 increased life of the combustor. Presently used units do not contemplate the overall effects of high heat _ 5 _ ~22~5 release, high pressure operation, and/or the thermal strain due to the hi~h combustor thermal output required. Applicantls discovery as disclosed herein employs a generator design incorporating op~imized com-5 bustion in order to provide high combustor output, highthermal efficiency, and extended combustor life.
As indicated by dif~iculties involved with state of the art downhole fired steam generators, control of com-bustion has been found to be a difficult task. General-10 ly speaking, the phenomenon of high pressure, high turbu-lence, and high heat release combustion combined with direct contact steam generation, has involved multiple and complex processes, each a relatively unknown phenome-na. Utilization of these processes in concert has gener-15 ~lly resulted in equipment which is substantially lessthan optimized, primarily incorporating designs achieved through "cut and try" processes. The invention dis-closed herein however, incorporates discoveries by the applicant which provide structure and techniques and/or 20 methods for control and therefore adjustment, of the processes involved~
Applicant's discovery is embodied in the DFDSG dis-closed herein. In this unit, control of fuel/oxidizer convective mixing provides a method of varyiny the com-25 bustion process within the combustor can. The disclosedstructure accomplishes this control of the combustion process by use of angularly disposed oxidizer passages.
Fuel is introduced in relation to the oxidizer jets so as to control the progressive combustion which follows 30 ignition and confine it to a predetermined portion of the combustor can. As will be discussed later, the angle of impingement between the oxidizer jets and f~lel inlet paths provides means for optimizing the location and size of the combustion reaction within the combustor 35 can.

In particular, Applicants' discovery establishes concepts relating the above mentioned angle of incidence and its' criticality in obtaining a satisfactory DFDSG
in that, angles either smaller or laryer than the opti-5 mum result in unstable combustion or extension of theprocess outside the combustor can. In the former case, unstable combustion results in increased pulsations, thereby increasing mechanical strain and reducing burner life. In the latter case, combustion beyond the con-10 fines of the combustor can results in poor combustionef'iciency and reduced steam generation, since feedwater and combustion gases are mixed befcre combustion is com-plete.
The direct ~ired downhole steam generator disclosed 15 utilizes a combustor operating on compressed gaseous ~uel such as natural gas, and an oxygen bearing oxidizer s~ch as compressed air. As discussed, the disclosed combustor optimizes fuel/oxidizer introduction providing a long lived efficient unit havin~ high output. A pyro-20 phoric fluid is introduced at the fuel inlet adjacent tothe fuel and oxidizer mixing zone. The method of intro-duction achieves controlled concentration of the ignit-ing fluid to insure combustion of a relatively larae volume of fuel/air mixture ~ithin the combustion contain-25 er or "can".
An additional discovery by the applicant involvesthe utilization of small amounts of water or similar fluid added to the combustion processes by pre-in~ection into the gaseous fuel stream, with subsequent in~ection 3~ and convective mixing internal of the combustor can It has been found that water injection as disclosed pro-vi~es a further means to optimize the combustion within the disclosed structure, and to control mechanical stresses induced through ultrasonic pulsations associat-35 ed with the combustion process.

6!35i In accordance with the invention, introduction ofthe pyrophoric fluid in a combustor utili~ing gaseous fuel and o~idizer, is accomplished by a method wherein the pyrophoric fluidJ in this case triethylborane ~TEB), 5 is contained for selective introduction into the combus-tion zone. Control of the TEB is enhanced through the use of an intermediate fluid, nonreactive with the TEB, which allows accumulation of a predetermined volume and accurate injection into the burner.
BRIEF DESCRIPTION OF THE DRA~INGS
Figure 1 is a semi-schematic system diagram showing the support and control systems for the disclosed steam generator utilized in downhole service incorporating 15 pyrophoric ignition.
Figure 2 is a semi-schematic section of a typical steam injected well, particularly showing the generator in place.
Figure 3 is a detailed dra~ing of the steam genera-20 tor disclosed, particularly showing details of convec-tive mixing of the fuel, oxidizer, and pyrophoric materi-al.
Figure 4 is a sectional view of the burner of Figure 3 particularly showing fuel and air channels.
Figure 5 is an additional detailed section showing a section of the disclo~ed generator showing annular water channels and combustor can.
Figure 6 is a combustion pulsation energy/pulsation frequency plot particularly showing reduction in destruc-30 tlve pulsation energy through use of the disclosed inven-tion.

DETAILED DESCRIPTION OF_THE INVENTION
Operation of the disclosed DFDSG 7, is best under-35 stood by r~ference primarily to Figures 3, 4, and 5,with occasional reference to Figures 1 and 2. As shown - 8 - ~2~85 in Figure 3, the combustor consists of a head or upper section 45, defining a gaseous oxidizer inlet 52, a pyro-phoric igni-tor inlet 60, and a fuel inlet 5~. The ignitor inlet 60 and fuel inlet 5~ intersect at location 61 via ori-fices 58 and 62. The combustion head further definesoxidizer combustion zone inlets or ports 51. It should be noted that although these inlets are disclosed in a configur-ation utilizing four inlet orifices, other configurations are contemplated including a configuration utilizing three orifices equally spaced on the circumference of a circle co-axial the fuel inlet and under certain conditions would provide proper operationD
The oxidizer inlet pasages 42 terminating in the orifices 51 are angularly disposed relative to the longitud-inal axis of the burner at a predetermined angle (0) 46.
Applicant has discovered that preferred angle or magnitude of 0 is approximately 15, although variations in fuel, pressure, and the unit heat capacity dictate a variation in angle from 10 to ~5.
As discussed above, the fuel and ignitor inlet oriEices are 58 and 42 respectively, terminating or merging to provide a fuel inlet passage 61, which terminates in a combustion gas inlet orifice 4~O Therefore, the mixed com-bustion gas and oxidant passes through the combustion zone 25 69 via orifice 44, and 51.
The pyrophoric inlet 60 terminating in the inter-secting inlet orifice 62 is further utili~ed as means to introduce a liquid combustion moderator such as water, after combustion has been initiated. As discussed above, it has been discovered that controlled amounts of liquid water introduced at this point in the combustion process provide a means Eor in situ control of the combustion process. This form of control rQsults in substantial improvement in com-bustion efficiency, heat release, and more importantly in the combustion pulsation phenomenon.
It has further been determined that the com-bustion pulsations inherent in high turbulence, high heat .~

- 9 - ~22~Ç~85 release combustion can produce mechanical fa-tigue in burner components (ref. FigO 6). Therefore, control of the pulsa-tion phenomenon contributes substantially to burner life as well as efficiency and output.
Feedwater in-troduced via channel 41 disposed long-itudinally beyond the combustion zone passes through orifice 53 where the feedwater flow is reversed and travels through an annular flow passage or water channel 55. Annular water channel 55 is defined by the generator outer sleeve 47 co-axial of combustor inner sleeve 48 and the combustor can 50.
An additional annular water channel or combustor can inner sleeve feedwater flow passage 64 is defined by coaxially dis-posed combustor inner sleeve 48 and combustor can 50.
The combustor can outer sleeve 47 is coaxial the generator head upper section 45, joining the lower portion of the combustor head ~5 at the upper end of the combustor outer sleeve ~7 at an intersection 43. The lower end of the combustor outer sleeve 47, is concentric of and abuts the combustor inner sleeve 48 at its lower end, adjacent to the Z0 steam generator feedwater inlet or flow control orifice 53, defining a feedwater intermediate flow channel 55, as intro-duced above.
In operation, gaseous oxidizer introduced through inlet 52 divides through the plurality of oxidizer inlet passages 42, intermediate the oxidizer inlet channel 52 and outlet orifice 51, providing an oxidizer outlet internal of the combustion chamber 75 at its upper end. Gaseous fuel enters the combustor head through passage or generator fuel inlet 54, at a pressure at or slightly greater than the oxi-dizer pressure. Fuel from the inlet 54 flows through genera-tor head fuel passage 76, terminated by the generator fuel outlet orifice 44. Similarly, an ignitor inlet 60 commun-icates with passage 79 which in turn is terminated by the ig-nitor inlet orifice 62. The central fuel/ignitor channel 61 communicates the fuel inlet port 58, and ignitor inlet port - lo - ~2~6~S

62 and combustion fuel chamber 75, via a combustor inlet orifice 44 located adjacent the oxidizer inlet ports 51.
As shown in Figure 4, the oxidizer inlet ports 51 are disposed about the fuel~ignitor inlet port 44 in tne upper end of the combustor head 45.
In the disclosed configuration, gaseous oxidant enters the combustion chamber 75 via the orifices Sl, while gaseous fuel enters the fuel/ignitor inlet port 44 oxidant and fuel pressures are such that convective mixing is obtain-ed in the combustion area at a predetermined location 69within the combustion chamber 75. As indicated above, the intersection angle of oxidizer inlet channels 42 with the longitudinal axis o~ the combustor can is critical in deter-mining the location oE combustion, i.e. 69, within the chamber 75, the applicant having discovered that containing and completing combustion within the combustor can provide high eEficiency, and improved output.
Assuming that gaseous Euel and oxidizer are flow-ing and entering the combustion chamber as indicated above, a pyrophoric fluid such as triethylborane is introduced ~hrough the ignitor inlet port 60, in a manner to be des-cribed later. Predetermined amounts of properly distributed pyrophoric fluid and gaseous fuel are convectively mixed adjacent their respective inlet ports, i.e. 62 and 58, enter-ing the combustion chamber in a premixed condition via theinlet orifice 44. On entering the combustion chamber, due to the convective mixing process, the i~nition fluid com-bines with the oxidizer somewhere in the vicinity of the upper inlet orifices, i.e. 51 and 44, whereupon the pyro-phoric fluid oxidizes raising the mixture to the igni-tion point oE the gaseous fuel/oxidizer mixture, and initiating the combustion process.
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As combustion proceeds, the process traverses the combustor can being essentially complete, prior to reach-ing the feed~ater/combustion gas mixing zone 77.
Steam is generated in the mi~ing zone 77 through the 5 discharge of water from the concentric flow passage defined as indicated above by the combustor can 50 and the combustor inner sleeve 48, the feedwater entering the mixing zone 78 after passing through a somewhat cir-cular flow control orifice 65 disposed near the lower 10 end of the combustor can 50. It should be noted that the feedwater -follows a helically turbulent path as it traverses the flow passage defined by the combustor can inner sleeve 4~ and the combustor can 50, since a helically wrapped turbulator 63 having a somewhat cylin-15 drical cross-section, produces helical flow within the channel 64 prior to its discharge via the flow control orifice 65 into the mixing zone 78.
Typically, for a burner utilizing natural ~as as a ~uel operating at 1500 pounds per square inch pressure, 20 and atmospheric air`operating at 1500 pounds per square inch, and utiliæing feedwater flows of 20 gallons per minute, 1200 pounds of steam per hour are produced at 1~50 pounds per square inch pressure having a quality of 70%.
tJtilizing the combustor described above, applicant has discovered that in addition to controlling the com-bustion location ~ithin the combustor can, injection of water via the ignitor port 6Q at a pressure of 1500 pounds per square inch and a flow rate of 0.10 gallons 30 per minute, combustion pulsations can be adjusted in order to further minimize combustion induced pressure pulsations on the burner assembly. As it has been deter-mined in prior art burners, ~hese pulsations occurring simultaneously with elevated temperatures produce a com-35 hination of stresses on the combustor material which inearly units resulted in early failure. These are clear-~L2~685 ly shown in the Department of Energy reports incorporat-ed by reference. As shown in Fig. 6, measurement of combustor can vibration, a ~uantity directly related to combustion pulsation, indicates reduced amplitude 5 through controlled injection of fluids such as water.
Thus, applicant has discovered that the combination of predetermined angular disposition of the oxidizer inlet ports in relation to the gaseous fuel inlets, and introduction of predetermined amounts of water provide a 10 means for greatly reducing combustor strain and in turn substantially increasing life of the direct fired down-hole steam generator unit.
As indicated in Figure 2, the generator of the inven-tion operates in a conventional well casing 12 of an 15 existing well. The burner is located at a predetermined depth in the well, the exact location dictated by down-hole location of oil bearing strata or oil sands. In position, the burner 7 communicates with the above ground system 1 via conduits 8, 9, lO, and 35 as indicat-20 ed above. With this arrangement, generator output isinjected into the ap~ropriate oil bearing strata provid-ing the required steam drive, thereby improving the out-put of adjacent wells interconnected by the above men-tioned oil bearing strata.
In keeping with an additional aspect of the inven-tion disclosed, ignition of the fuel/air mixture inter-nal of the combustor can 50 in the vicinity of point 69 is initiated by prior adjust~ent and injection of the pyrophoric fuel inlet system as follows.
A pyrophoric fluid such as triethylborane is stored in oxygen-free container 25 (ref Figure l). Exclusion of oxygen is assured by maintaining an atmosphere of nitrogen or other inert gas above the stored TER. The nitrogen further serves to provide 2 driving force for 35 removal of TEB to be described later.

The dip tube 26 having i-ts lower end submerged in the TEB communicated with a mul-tiway valve 3] via conduit 33. ~ charge cylinder 21 communicates with multiway valves 31 at its upper and lower ends. The uppex multiway valve 31 is in fluid communication wi-th an intermediate fluid container 23 storing an intermediate fluid 24 such as water.
The lower multiway valve 31 communicates with the high pressure water supply 6 via conduit 41. Lower multiway valve 31 further communicates at a preselected position with a water drain 39 preferably to the atmosphere.
In operation, with air or other oxidizer, fuel and water supplied to the burner 7 via conduits 8, 9, 10, and 35 as described above, the charge cylinder 21 has been filled with water via lower multiway valve 31. Multiway valves 31 are now adjusted to admit intermediate fluid 24 from container 23 and venting container 23 via lower valve 31, through outlet or drain 39, thereby completely filling the charge container 21 with the intermediate fluid 2~. At this point, multiway valves 31, are readjusted to admi-t a predetermined amount of pyrophoric fluid, i.e. TEB to the container 21 via dip tube 26 and conduit 33. Assuming that fuel, air and water are flowing into the burner assembly 7 as indicated above, multiway valves 31 are again adjusted to force the predetermined amount of pyrophoric liquid 22 contained in 21 into the inlet of conduit 35 using the pressure of water supply 6, whereby it enters the burner via inlet or port 60 passing through check valve 61, entering the combustor via port 62. (As shown, the intersection of the fuel outlet 51 at a pressure approximately 5% greater than the fuel pressure).
It is apparent that there has been provided în accordance of the inventiGn a high pressure steam generator that fully satisfied the objects, aims and advantages set forth above. While the invention has been described

2~6~i in conjunction with a specific embodiment or embodiments thereof, it will be evident to those skilled in the com-bustion arts that ~any alternatives, variations and sub-stitutive modifications are apparent in the li~ht of the 5 above description. Accordingly, it is intended to con-template all such alternatives, modifications and varia-tions as fall within the scope of the appended claims.

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a direct fired high pressure steam generator of the type having a burner base with means for supplying feedwater, gaseous fuel and oxidizer, and a feedwater cooled combustion chamber extending from said base along a common longitudinal axis, said base/chamber extension defining a chamber inlet end, said chamber generating high pressure combustion gases and having a section for generating steam by mixing feedwater and combustion gas, the improvement comprising;
a plurality of conduits in said base terminated by inlet ports defined by said inlet end, said conduits angularly disposed to said longitudinal axis of said base and chamber for directing gaseous oxidizer through said ports internal of said combustion chamber and in said base end for generating gaseous oxidizer jets, said jets intersecting entirely internal said chamber; and, a central fuel inlet port in said base and centrally adjacent said oxidant inlet ports for generating a central fuel jet, said jet intersecting said oxidizer jets and means for introducing water into said fuel inlet port so as to reduce vibrations caused by combustion.

2. The generator of claim 1 where said angular disposition has a range of 15°-45°.

3. Apparatus for downhold generation of steam and high temperature gases of the type having a water cooled combustion chamber and steam generating sections comprising;
a burner base with means for introducing gaseous fuel, oxidizer, and water, said base having supply and combustion ends and a central axis;
a plurality of oxidizer conduits in said base, said conduits angularly disposed about said base axis, having initial and terminal ends in said base supply and combustion ends respectively, said terminal ends defining oxidizer inlet ports in said base combustion end;

a fuel inlet passage in said base communicating said supply and combustion ends, said base combustion end and fuel passage defining a fuel inlet port in said base combustion end, said port essentially coaxial said base axis;
a generally cylindrical open ended combustion chamber extending from and coaxial of said base combustion end, and surrounding said oxidizer and fuel inlet ports for containing fuel and oxidizer during combustion and further directing combustion gas flows through said open end;
a generally cylindrical open ended conduit extending from said base combustion end, said conduit telescoping said chamber and extending beyond said chamber open end, said extension defining a steam generator section downstream said chamber open end, said telescoped chamber outer surface and conduit inner surface further defining an open ended first flow passage for cooling said chamber and supplying water to said generator for producing steam;
an outer housing extending from and generally coaxial of said base combustion end, and partially surrounding said conduit, said housing inner surface and conduit outer surface defining a second flow passage in fluid communication with said first passage adjacent said base combustion end;
means in said second flow passage for admitting feedwater at a predetermined rate;
means admitting pressurized gaseous fuel and oxidizer at pressures in a range of 500 to 2000 pounds per square inch and in predetermined flow rate ratios to said feedwater rate to said base supply end;
means in said combustion chamber, for igniting fuel and air mixture;
wherein said base conduits and inlet ports angularly inject oxidizer and fuel flows for combustion within said combustion chamber, thereby generating high temperature gases, said gases exiting said chamber open end, and feedwater exiting said first passage open end generate high pressure steam through contact with said high temperature gases and means for introducing water into said fuel inlet port so as to reduce vibrations caused by combustion.

4. The apparatus of claim 3 wherein the axis of said oxidizer conduits are symmetrically disposed about and angularly inclined from said base axis in a range of 10 - 45 degrees.

5. The apparatus of claim 4 wherein the burner base combustion ends further comprises three oxidizer inlet ports symmetrically spaced around said fuel inlet port.

6. A method of improving the service life of a direct fired downhole steam generator, said generator having base means supplying gaseous fuel, water and oxidizer to said base, an outer cylinder and combustion chamber extending from said base, said cylinder surrounding and extending beyond said combustion chamber, said extension defining a steam generating section; and, conduit means in said base said conduit means supplying said gaseous fuel and oxidizer to said combustion chamber and feedwater to said steam generator, comprising the steps of;
supplying gaseous fuel pressurized in the range of 500 to 2000 pounds per square inch to said fuel conduit means;
supplying a gaseous oxidizer pressurized to the range of 500 to 2000 pounds per square inch;
supplying feedwater to said feedwater conduit means at pressures in the 500 to 2000 pounds per square inch range, and at a predetermined flow rate;
mixing said fuel and water through injecting water into said fuel conduit means, said water having a predetermined flow rate;
wherein ultrasonic pulsations generated by the combustion process are controlled.

7. The method of claim 6 further including the step of controlling said injected water flow rate to the range of .3 to .6% of said feedwater rate.

8. The apparatus of claim 3 wherein said introduced water is injected at a rate of .3 to .6 percent of the feedwater flow rate.