US2827761A - Combustor - Google Patents

Description

March 25, 1958 R. M. SCHIRMER ETAL COMBUSTOR Filed Jan. 26, 1953 E. H. FROMM R.M.SCHIRMER vBY ATTORNEYS United States Patent O COMBUSTOR Robert M. Schirmer and Ellsworth H. Fromm, Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Application January 26, 1953, Serial No. 333,047

4 Claims. (Cl. 60-39.23)

This invention relates to combustors. In one ot its more specific aspects, it relates to an improved combustor used in a jet engine. In another of its more specific aspects, it relates to a means and a method for regulating the direction of air ow into a prevaporizer type combustion chamber.

One type of aircraft propulsion system, i. e., a turbojet engine comprises an air compressor, fuel inlet means at the compressor outlet, and a gas turbine driven by the combustion products and air, which turbine mechanically drives the said compressor. Thrust is developed by the expansion of the stream of combustion products and unused air through a nozzle or jet in a rearwardly extending direction. One established practice in the art is the introduction of fuel into the combustion chamber in the form of a vapor. The fuel is vaporized in vaporizer tubes which can take any one of several conventional forms. One such type of vaporizer tube is the J-type. Such vaporizer tubes are mounted in the upstream end of the combustor in a tube plate or combustor head and extend into the flame tube or combustor. The tube plate forms a partial closure at the upstream end of the combustor so that primary air from the compressor is directed into the vaporizer tubes located around the peripheral portion of the combustor, `and through at least one primary air duct centrally located in the tube plate. The tube plate acts as a director for primary air introduced into the upstream end of the primary combustion zone.

Fuel and air are introduced into the upstream ends of the vaporizer tubes. The vaporizer tubes are exposed to the combustion flames and the fuel is thereby vaporized in the vaporizer tubes. The vaporizer tubes change direction through 180 intermediate their ends so that the vaporized fuel and air mixture formed in the tubes is discharged upstream into the stream of air discharged from the downstream end of the primary air duct. Air flowing through the vaporizer tubes assists in vaporization of the fuel by reducing the partial pressure of the fuel and thus reducing the temperature required for complete fuel vaporization. The lair also serves to reduce the deposition of carbon, which results from overheating of the fuel on the walls of the tubes and aids in the transport of any liquid and unvaporized fuel through the vaporizer tubes. This portion of primary air which passes through the vaporizer tubes also aids in obtaining complete combustion of the vaporized fuel discharged from the vaporizer tubes into the primary combustion chamber. The major portion of primary air is introduced through a primary air duct located in the tube plate.

In the operation of such an engine, changes in the regimes of engine operation affect the severity of combustion conditions in the primary combustion zone and have a pronounced influence upon llame stability in the primary combustion chamber. For example, a change in altitude of aircraft from slightly above sea level to 60,000 feet or higher causes as much as a ten fold decrease in density and a corresponding increase in linear velocity of air through the primary air duct. This increased linear ice air velocity results in an increased penetration of the air into the combustion zone. Such an increase in penetration of air into the combustion zone is detrimental to stable combustion, causing the flame front to move downstream in the combustor. The manner in which the air is supplied to the combustion chamber, as well as the telationship between the quantity of air and fuel, must be regulated in order to maintain stable combustion with widely varying operating conditions.

The various objects of this invention will be attained by one or more of the aspects of this invention.

An object of this invention is to provide improved means for regulating the ow of primaryl air into the primary combustion zone. Another object of the invention is to provide means for limiting the linear velocity of primary air introduced in a downstream direction axially into the primary combustion zone. Another object of the invention is to provide a means for regulating the direction in which air is admitted into the primary combustion zone of a prevaporizer type combustion chamber. Another object of the invention is to provide a means for regulating the direction in which air is admitted into the combustion zone of a prevaporizer type combustion chamber in accordance with the linear velocity of air introduced through the primary air duct. Another object of the invention is to provide a method for regulating the mixing of primary air and vaporized fuel in the combustion zone of a prevaporizer type combustion chamber. Other and further objects of this invention will be apparent to those skilled in the art upon study of the accompanying disclosure and the drawing.

Broadly speaking, this invention comprises a means and method for diverting a portion of primary air, in response to an excess of a predetermined maximum linear air Velocity from an axial ow radially into the primary combustion zone. Orifice-type primary air inlets are provided in a poppet valve so as to permit a normal flow of primary air through those inlets into the axial portion of the combustion chamber where the primary air is mixed with prevaporized fuel, preferably introduced in an upstream direction counter to the ow of incoming primary air. An increase in linear air velocity over a predetermined maximum overcomes the force of a spring or biasing force acting on the poppet valve and forces the valve head from its seat at the downstream end of the primary air duct so that air is discharged radially from the primary air duct in addition to flow of primary air through the conduits in the valve head, into the central portion of the combustion zone.

Better understanding of this invention will be obtained upon reference to the drawings in which- Figure l is a section elevatio-n of a combustor incorporating the control means of this invention.

Figure 2 is a section View of a modication of the prir mary air inlet assembly.

Referring particularly to Figure 1 of the drawings, combustor 11 comprises shell 12, open at its downstream end and closed at its upstream end by combustor head 13. Vaporizer tube 14, which is preferably only one of several such vaporizer tubes used in the combustor, is aixed at its upstream end to combustor head 13 and .makes a change of direction through intermediate its-ends. Air inlet 15 is connected to vaporizer tube 14 through combustor head 13. Fuel inlet conduit 16 extends from a fuel source, not shown, into vaporizer tube 14. Primary air inlet conduit 17 is provided in the central portion of tube plate 13 and the downstream end of conduit 17 forms a valve seat upon which poppet valve 18 is normally seated. Spider member 19 is connected to conduit 17 and supports alignment member 21, alignment member 21 extending beyond the downstream end of conduit 17. Alignment member 21 is provided at its SUL `Referring particularlyto'igure 'ofV drawings,

Y parts lkethose described in connection with"EieureA 1 are desgnatedby numerals- Theiprmarx airnlet in this device, is modified by usinga biasngimeansg s uch as tension spring, 2 3? which is ait-acflledl t9 Portlet valve 18 and extends upstream therefromithrough abortion- 0f the interior'of conduit17, V Spring ZS'ismaintained in iixedpsition atts upstream ed- Y In theop'eraton of; the device' Shown vin the drawings@ fuel and airdare introduced intojthe combustion chamber I'adjacent' the `downstream end Vof conduit`17,'wherein the fuel is ignited.V Vaporizer tubes V1,4 are exposed to the burning fuel, whereby the liquid fuel .is vaporized. Primary" air in addition to Ythat entering the Ycombustol through vaporizer tubes 14 passes through conduit 17 and the plurality ofY inlet openings 24 in poppet valve 1 8. The prima-ry air which ,ows'through conduits 24 is admixed with the prevaporized fuel entering the combustionchaxnber from vaporizer tube 14 and is burned, preferably in the upstream end portion of combustor 11. The tension on spring member 23 or 23Y is such that as the linear velocity of air passing through conduits 24 increases -to such an extent that the ilame front is moved downstream from the inlet end of vaporizer conduit 14, theY air pressure overcomes the pressure of spring 23 or 23 causing poppetvalve 18 to be displaced from its seat on the downstream end of conduit Y17. When poppet valve 18 is displaced, a portion of the air stream passes radially between the downstream end of conduit 17 and poppet valve 18. A'portion of Vthe primaryraircontinuesto pass centrally into the combustor through inlet conduits 7.4Y Bycausinga portion of the primary air to pass radially. into the combustor upon an increase in linear air velocity above a predetermined maximum, a limit is placed uponthe amount of displacement of the llame front downstream which can be caused rby an increase in linear velocity ofthe incoming primary air. The portion of the primary air which is radially introduced into the combustor causes an increase in turbuposition. Y In such a modification, alignment member 21 extends through the central portion of poppet valve 18 so as to maintain the kpoppet valve in alignment with conduit 17. Tension spring 23' is then afxed toralign-VY ment member 21 at a point upstream Vof poppet valve 18 and is affixed at its downstream end to the upstream side of poppet valve 18. In this construction, the spring member is maintained in an atmosphere of relatively cool in-f coming primary air and is not subjectedto the severe temperature conditions "to `which spring member 23 is subjected. Y

YMany other modifications jof this inventionV will be apparent te those skilled; in the aft upon study Q f thefae company/ine dse1esurelt beLeYedtbat such Ineditications are within the spirit and :thescopc of this inveni closure member in the upstream end of said shell; at

least one vaporirzer tube` extending from said closure member" into the interior of--said combustor shell; a primary air inlet'exten'ding through said closureV member'and connected to the upstreamfend of each said vaporizer tube; a fuel conduit extending into each'said vaporizer tube; a primary air inlet conduit extending into each said vaporizer tube; a primary `air inlet conduit extending Y centrally" into said vaporizer ,shell throughfsaid closure member; a poppet valve seated at and closing the downstream endy of said primary air inlet conduit; inlet conduits ex-tcnding'-through said` poppet valve and pressure means connected to saidpoppet-valve to bias said v alve closed with a predetermined pressure.

3. Thefcombustor, of `2 wherein saidgvaporizer V,and extend to points centrally'disposed in the upstream end portion ofsaid'con-ibustor, and said pressureemeans is a compression spring positioned downstream of and Vpressing against said poppet valye. Y

ReferencesfCited in thefrrile of this patent

Images