WO1981002762A1

WO1981002762A1 - Vaporizing combustor tube

Info

Publication number: WO1981002762A1
Application number: PCT/US1980/000301
Authority: WO
Inventors: J Bailey
Original assignee: J Bailey
Priority date: 1980-03-19
Filing date: 1980-03-19
Publication date: 1981-10-01

Abstract

Vaporizing combustors generally have fuel-air inlet tubes which tend to clog with carbon deposits. Clogging can be stopped by raising the temperature of the tubes, but service life is reduced. Making such tubes of high temperature ceramic materials is unsatisfactory because high thermal stresses are created which can lead to cracking. Herein, a tube structure (48) ends in a delivery end portion (50) within a combustion chamber (18) and adjacent a splash structure (36) with a mixed stream (arrows 33) flowing generally from the delivery end portion (50) towards a second end portion (28) of the chamber (18). A deflector (34) is separated from the tube structure (48) and is positioned to receive the stream (arrows 33). The deflector (74) deflects the stream (arrows 33) through an angle of greater than 90o and towards the splash structure (36). The deflector (74) can be of a ceramic material, thus allowing long time high temperature service.

Description

DESCRIPTION VAPORIZING COMBUSTOR TUBE

Technical Field

The invention relates to an improvement in a vaporizing combustor, more particularly a vaporizing combustor of the type used in gas turbines.

Background Art

In one type of vaporizing combustor for gas turbine engines, a mixture of fuel and oxidizer flows into a vapor tube which consists of a hollow stem having a rather large cross-sectional area and through which oxidizer and fuel enter the system. The oxidizer, generally air, and entrained fue , when they reach the end of the hollow stem, are guided outwardly into two opposite hollow arms which bend back somewhat more than 90°. Generally, the exits from the arms are of somewhat smaller cross-section than the rest of the arms, thus accelerating the mixture to a higher flow velocity. The oxidizer, with its entrained fuel, is then directed back • against a splash plate from which the fuel is redirected, vaporizes and burns.

Carbon deposits tend to form within the constricted vapor tube passages, thereby restricting 'air flow and eventually rendering the system « inoperable. Also, if the vapor tubes are operated with a minimum temperature above about 1,000°F, in order to prevent carbon from adhering to them, then the maximum temperature of the flame is too high to provide the desired service life if the vapor tubes are metallic. In such a case, the tubes service life is reduced due to oxidation and sulfidation. The use of ceramic vapor tubes, which would have a long service life at above 1000°F might be considered. The vapor tube used is, however, relatively complex in that the arm portion must be curved and must be attached to the stem while maintaining smooth streamlined internal flow. Such can be readily accomplished in the case of metal vapor tubes. However, the manufacture of ceramic vapor tubes having such a configuration is much more difficult. More importantly, the complex intersection between the curved arm portions and the stem tends to create thermal stresses which lead to cracking of vapor tubes made Of ceramic materials, particularly at the junctions of the arms with the stem.

The present invention is directed to overcoming one- or more of the problems set forth above.

Disclosure of Invention

According to an embodiment of the present invention, an improvement is provided in a vaporizing combustor of the type having a side^"wall construction defining a combustion chamber having first and second end portions. In such combus ors, means are provided for delivering a mixed fuel-oxidizer- stream, to the first end portion, the stream having a ve^'locity generally towards the second end portion. Deflecting means are provided for deflecting the stream through an angle of greater than 90°. A splash structure redirects the deflected stream generally towards the second end portion of the chamber. .The improvement comprises using a delivering means for the mixed stream which includes a tube structure ending in a delivery end portion from which the mixed stream flows generally towards the second end portion. The improvement also comprises using a deflecting means which includes a deflector separated from the tube structure and positioned to receive the stream, on its exiting from the delivery end portion, with the deflector being of a structure to deflect the stream generally through an angle of greater than 90°. Means are also provided for mounting the deflector a spaced distance away from the delivery end portion.

Through utilizing an-improvement as just discussed above, the deflector can be made of a ceramic material which can stand high temperature operation for long periods of time. At the same time, thermal stresses are, not built up in the deflector, since it is not joined to the tube structure. That is, there is^'not a relatively cool tube structure joined via a relatively complex curvature to a relatively hot pair of arms. Thus, the deflector can be kept hot enough to prevent carbon from adhering to it while long time use life can be attained. And, all of the above can be attained without the creation of large thermal stresses in the deflector.

Brief Description of Drawings

Figure 1 illustrates, in fragmentary partial view, partially in section, a vaporizing combustor in accordance with an embodiment of the present invention"in use in a gas turbine engine having an annular combustion chamber;

Figure 2 illustrates, in an enlarged fragmentary view, partially in section, a portion of the vaporizing combustor shown in Figure 1;

Figure 3 illustrates a view taken generally along the line III-III of Figure 2, with the side wall construction of the combustion chamber omitted for clarity.

Best Mode for Carrying Out the Invention

Figure 1 illustrates a gas turbine 10 having an outer wall 12 and inner wall 14. A vaporizing combustor 16 lies between the walls 12 and 14. Generally, the vaporizing combustor 16 will be in the nature^"of an annular combustion chamber 18 defined by a side wall construction 20 which includes an inner wall 22 and an outer wall 24. The combustion chamber 18 has a first end portion 26, a second end portion 28 (from which combustion gases exit rightwardly in Figure 1) and an end wall 30 closing off the first end portion 26.

Means 32, seen best in Figure 3, serves for delivering a mixed fuel-oxidizer stream (arrows 33) , having a velocity generally towards the second end portion 28, through the end wall 30. Deflecting means 34 serves for deflecting the mixed stream through an angle of greater than 90°, and generally towards the ^"side wall construction 20 and the end walls 30, to form a deflected stream (arrows 35). A' splash structure or plate 36 is positioned to receive the deflected stream and adapted to redirect it (arrows 37) generally toward the second end portion 28 of the^*chamber 18. The entering fuel flow is indicated by an arrow 38 and the entering oxidizer stream is shown by arrows 40a and 40b. The present invention is particularly concerned with utilizing particular deflecting means 34 and a particular mixed fuel-oxidizer stream delivering means 32. Turning first to the mixed stream delivering means 32, in accordance with the present invention such includes a tube structure 48 which ends in a delivery end portion 50 within the chamber 18 adjacent the splash structure 36. The mixed stream (arrows 33) flows generally towards the second end portion 28 of the chamber 18. In the preferred embodiment of the invention the tube structure 48 has- an entry end portion 52 external of the chamber 18: Further, the tube structure 48 preferably has an inner tube 54 and an outer tube 56 which are generally coextensive. The tubes 54 and 56 define a generally annular flow passage 58 between them and the inner tube 54 defines a generally cylindrical internal flow passage 60. The inner tube 54 has a delivery end portion 62 while the outer tube 56 has a delivery end portion 64. The inner tube 54 has an entry end portion 66 and the outer tube 56 has an entry end portion 68. The delivery end portion 64 of the outer tube 56 is sealed to the delivery end portion 62 of the inner tube 54. The. inner tube 54 has at least one hole 70 through it to communicate the annular flow passage ' 58 with the cylindrical flow passage 60. In this manner, oxidizer, for example air, can be flowed as indicated by arrows 40a into the annular passage 58 and as indicated by arrows 40b, also into cylindrical passage 60. Near the delivery end portion 50 of the tube structure 48, additional oxidizer is added via one or more holes 70 to the fuel-oxidizer mixture just before it exits the delivery end 50 of the tube structure 48. This provides for a more thorough mixing of the fuel with the oxidizer. Since pressure to the left of end wall 30 exceeds that in the chamber 18, acceleration of the fuel-oxidized mixture takes place as it flows rightwardly through tube structure 48.

Also in accordance with the present invention, the deflecting means 34 includes a deflector 74 which is separated from the tube structure 48 and is positioned .to receive the mixed stream (arrows 33) after it exits from the delivery end portion 50 of 'the tube str-ucture 48. The deflector 74 is of a shape and structure sufficient to deflect the-mixed stream (arrows 33) through an angle of greater than 90°, and generally towards the end wall 30 and the side wall construction 20, as shown by the arrows 35.

It will be noted that the deflector 74 does not have complex bends in it and is not connected to the relatively cool tube structure 48 (which is cooled by the fuel). Thus, high thermal stresses are not set up in the deflector 74. This allows the deflector 74 to be constructed of a high temperature resistant material, e.g., a ceramic material, which ^'has a long service life at high * temperatures. Since the deflector 74 can be utilized at high temperatures, e.g., 1000°F and above, carbon deposits do not significantly occur therein and flow^' is not interrupted or stopped. As may be noted by reference to the figures of the drawings, particularly to Figures 2 and 3, the deflector 74 generally includes a concave cavity 76 which generally opens towards the end wall 30 in order to provide the desired deflected flow as shown bv the arrows 35. Also in accordance with the present invention, means 78 (See Figure 2) are provided for mounting the deflector 74 a spaced distance away from the delivery end portion 50 of the tube structure 48. This is to ensure that no contact takes place between the delivery end portion 50 of the tube structure 48 and the deflector 74. Basically, the mounting means 7.8 includes a rod structure 80, more particularly a pair of rods 82 and 84, which are attached to extend generally laterally from the deflector 74, generally in opposite directions. The rod structure 80, more particularly the rods 82 and 84, each extend to adjacent the side wall construction 20 and are mounted thereto. Preferably, resilient mounting means 86, in the embodiment illustrated a pair of leaf springs 88 and 90, serve for resilient"mounting the respective rods 82 and 84 to the side wall construction 20. In the particular embodiment illustrated, the rods 82 and 84 pass through holes 92 and 94 in^*-the side wall construction 20 and the respective springs 88 and 90 are attached between the ends of the rods 82 and 84 and an exterior 96 of the side wall construction 20. This resilient mounting of the deflector 74 prevents axial and angular movement Of the deflector 74, while still permitting correction for the differences in axial expansion of the deflector 74 (and the generally integral rods 82 and 84) as compared to the side

2^N^, q ^;"^'' wall construction 20, as the vaporizing combustor 16 changes temperature.

Industrial Applicability

A vaporizing combustor 16 as described above is particularly useful in gas turbines 10 having annular combustion chambers 18. In such an apparatus, the splash plate 36 is aligned as illustrated in the figures of the drawings with adjacent of the splash plates 36 being close enough together to provide a relatively steady flame around the annular chamber 18. -^■

Through utilizing an improved vaporizing combustor 16 as described above, carbon deposits can be prevented without developing such thermal stresses as would lead to failure of a conventional deflector and while still retaining long service time for such deflectors.

Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, disclosure and the appended claims.

Claims

1. In a vaporizing combustor (16) having a side wall construction (20) defining a combustion chamber (18) having first (26) and second (28) end portions, means (32) for delivering a mixed fuel-oxidizer stream (arrows 33) to said first end portion (26) having a velocity generally towards said second end portion (28) , deflecting means (34) for deflecting said stream (arrows 33) generally through an angle of greater than 90° to form a deflected stream (arrows 35) , and a splash structure (36) positioned to receive the deflected stream (arrows 35) and adapted to redirect the deflected stream (arrows 35) generally towards the second end portion (28) , the improvement comprising: wherein said means (32) includes a tube structure (48) ending in a delivery end portion (50) within the chamber (18) adjacent the splash structure (36) , said end portion (50) being aimed generally towards the second end portion (28) ; wherein the deflecting means -(34) includes a deflector (74) separated from the tube structure (48) , positioned to receive the mixed stream (arrows 33) on exiting thereof from the delivery end portion (50) --and of a structure sufficient to deflect the mixed stream (arrows 33) generally ' through an angle of greater than 90°,; and including means (78) for mounting the deflector (74) a spaced distance away from the delivery end portit (50) .

2. The combustor (16) as set forth in claim 1, wherein said deflector (74) is constructed of a high temperature resistant ceramic material.

3. The combustor (16) as set forth in claim 1, wherein said deflector (74) includes a concave cavity (76) generally facing said delivery end portion (50) .

4. The combustor (16) as set forth in claim 1, wherein said means (78) includes a rod structure (80) attached to extend generally laterally from said deflector (74) and mounted to said side wall construction (2Q.) .

5. The combustor (16) as set forth in claim 4, including means (86) -for resiliently mounting said rod structure (80) to said side wall construction (20) .

6. The combustor (16) as set forth in claim 1, wherein said means (78) includes a pair of rods (82, 84) attached to extend generally laterally in generally opposite directions from said deflector (74), each rod (82, 84) extending to adjacent said side wall construction (20) and means (86) for resiliently mounting each of said rods to said side wall construction (20) .

7. The combustor (16) as set forth in claim 1, wherein said tube structure (48) has an entry end portion (52) external of said chamber (18) , said tube structure includes generally coextensive inner (54) and outer (56) tubes defining a generally annular flow passage (58) therebetween, said inner tube (54) defining a generally cylindrical flow passage (60), each of said tubes (54, 56) having entry (66, 68) and delivery (62, 64) end portions, said delivery end portion (64) of. said outer tube (56) being sealed to said delivery end portion (6.2) of said inner tube (54) , and said inner tube (54) having at least one hole (70) therethrough communicating said flow passages (58, 60) adjacent said delivery end portions (62, 64).

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