US20080006641A1

US20080006641A1 - Positioning arrangement for components of a pressure vessel and method

Info

Publication number: US20080006641A1
Application number: US11/061,608
Authority: US
Inventors: Lev Prociw; Aleksandar Kojovic
Original assignee: Pratt and Whitney Canada Corp
Current assignee: Pratt and Whitney Canada Corp
Priority date: 2005-02-22
Filing date: 2005-02-22
Publication date: 2008-01-10
Also published as: US8181465B2; US20090060636A1; US20120227415A1; CA2537397C; CA2537397A1; US8959928B2

Abstract

The positioning arrangement comprises at least one pair of complimentary rounded recesses, each recess being provided on the mating face of the corresponding component. One ball is positioned between each pair of complementary recesses.

Description

TECHNICAL FIELD

The invention relates generally to a positioning arrangement for components of a pressure vessel and to a method of positioning two adjacent components of a pressure vessel.

BACKGROUND OF THE ART

Pressure vessels are often made of two or more components that are connected together at some point during manufacturing. These components generally have mating faces that are provided with complementary positioning elements to ensure that the components are perfectly aligned. These positioning elements have a number of advantages, including being able to ensure that components are always oriented in accordance with their design. However, pressure vessels, particularly thin wall pressure vessels, are often prone to high stress concentration when provided with these positioning elements.
In some arrangements, the positioning elements include a cylindrical pin located at the interface between the two components being joined together. Cylindrical pins have some limitations and drawbacks. At first, small cylindrical pins are difficult to handle during the assembly and pins manufactured with very small tolerances are expensive. They can also be easily damaged if they are not handled properly. Then, the arrangements require that two perfectly colinear cylindrical holes be provided in the adjacent surfaces. These holes produce stress concentrations due to the relatively deep holes that are required and the sharp edges thereof.
Accordingly, there is a need to provide an improved positioning arrangement for components of a pressure vessel, and a method of assembling two adjacent components of a pressure vessel, with very minimal stress concentrations.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide an improved positioning arrangement for a pressure vessel, and an improved method of assembling two adjacent structures of a pressure vessel.
In one aspect, the present invention provides a positioning arrangement for a pressure vessel having at least two adjacent components to be secured together at mating faces, the arrangement comprising: at least one pair of complementary recesses forming a rounded space, each recess being provided on the mating face of one corresponding component; and one ball positioned in the rounded space of one corresponding pair of complementary recesses.
In another aspect, the present invention provides a method of assembling two adjacent components of a pressure vessel, the method comprising: machining a first recess in one of the components; machining a second recess in the other component, the two recesses being complementary and forming a rounded space when the two adjacent components are being assembled; and providing a ball between the two complementary recesses, the ball having an external shape and size which are substantially identical to an internal shape and size of the rounded space.
In another aspect, the present invention provides a pressure vessel arrangement having at least two adjacent components to be secured together at mating faces, one of the two components being a fuel nozzle, the arrangement comprising: at least one pair of complementary rounded recesses forming a space, each recess being provided on the mating face of one corresponding component, and one rounded element snugly fitted in the space of one corresponding pair of complementary recesses.
Further details of these and other aspects of the present invention will be apparent from the detailed description and figures included below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures depicting aspects of the present invention, in which:
FIG. 1 schematically shows a generic gas turbine engine to illustrate an example of a general environment in which the invention can be used.
FIG. 2 is a schematic side view showing an example of a pressure vessel with two different positioning arrangements.
FIG. 3 is an enlarged schematic cross-section view of an example of a positioning arrangement in accordance with the present invention.
FIG. 4 is an enlarged schematic cross-section view of another example of a positioning arrangement in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a gas turbine engine 10 of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan 12 through which ambient air is propelled, a multistage compressor 14 for pressurizing the air, a combustor 16 in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section 18 for extracting energy from the combustion gases.
A pressure vessel can be generally defined as a hollow structure which will be pressurized at one point during its use. This pressure will generate internal forces in the material of the structure. Very often, a pressure vessel is made of at least two components that are secured together using bolts, welds, solders or any other suitable kind of fasteners. An example of such pressure vessels is the engine casing of the gas turbine engine 10.
FIG. 2 schematically illustrates an example of a pressure vessel 20 having two mating components 22, 24 being secured together using fasteners (not shown). In this case, the pressure vessel 20 comprises the walls of a fuel nozzle 100.
To ensure that the mating components 22, 24 of the pressure vessel 20 are aligned relative to each other with a very high degree of accuracy, the present invention uses at least one rounded element, preferably a spherical ball 30, which is designed to fit between a pair of opposite complementary recesses 32, 34 machined in the mating faces of the components 22, 24, which complementary recesses 32, 34 form together a rounded space in which the ball 30 is set. FIG. 2 also illustrates, on the left side, a pin 102 similar to the ones used in the prior art.
Preferably, as illustrated, the rounded space and the ball 30 are spherical. Moreover, more than one set of spherical balls 30 and corresponding spherical recesses 32, 34 are preferably provided and their position is such that during assembly, the components 22, 24 cannot be assembled with a wrong orientation. For instance, the position of the various balls 30 can be out of alignment with reference to a line of symmetry of the components 22, 24 for this purpose.
The advantages of using balls 30 and corresponding recesses 32, 34 are numerous. First, the balls 30 are available at low cost with very accurate tolerances. They are available in a large number of sizes. Balls 30 can be easily manipulated with equipment devised for ball tacking and they can be easily positioned during the manufacturing. These balls 30 are more robust than pins, especially during handling or dropping. Moreover, the rounded recesses 32, 34 in the arrangement produce a far lower stress concentration in critical areas due to their smooth geometry. This is particularly advantageous in the case of pressure vessels having a thin wall, in which conventional positioning arrangements cannot be used because they can introduce severe stress concentrations.
If desired, the ball 30 can be partially embedded in a recess 34 provided in one of the components, which recess 34 is located deeper in the corresponding component 34 than the opposite recess 32 of the adjacent component 24. This second component 24 would have only its recess 34 shaped as a segment of the geometric form, as illustrated in FIG. 4. Both recesses 32, 34 are thus nonidentical. This is useful, for instance, if one component is thinner than the other.
It should be noted that FIGS. 3 and 4 illustrate the components 22, 24, the recesses 32, 34 and the ball 30 having a very large tolerance between them. This is only for the purpose of better illustration. In fact, the outside shape and size of the ball 30 is substantially identical to the interior shape and size of the space.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, the present invention is not limited to pressure vessels used in a gas turbine engine. The ball 30 and the corresponding recesses 32, 34 can have a rounded shape which is not necessarily spherical, such as ovoid, ellipsoid, spheroid, conoid, etc. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.

Claims

1. A positioning arrangement for a pressure vessel having at least two adjacent components to be secured together at mating faces, the arrangement comprising:

at least one pair of complementary recesses forming a rounded space, each recess being provided on the mating face of one corresponding component, and

one ball positioned in the rounded space of one corresponding pair of complementary recesses.

2. The positioning arrangement as defined in claim 1, wherein the rounded space and the corresponding ball are spherical.

3. The positioning arrangement as defined in claim 1, wherein the pressure vessel comprises a fuel nozzle.

4. The positioning arrangement as defined in claim 1, wherein the recesses of a same pair are identical.

5. The positioning arrangement as defined in claim 1, wherein the recesses of a same pair are nonidentical.

6. A method of assembling two adjacent components of a pressure vessel, the method comprising:

machining a first recess in one of the components;

machining a second recess in the other component, the two recesses being complementary and forming a rounded space when the two adjacent components are being assembled; and

providing a ball between the two complementary recesses, the ball having an external shape and size which are substantially identical to an internal shape and size of the rounded space.

7. The method as defined in claim 6, wherein the rounded space and the corresponding ball are spherical.

8. The method as defined in claim 6, wherein the pressure vessel comprises a fuel nozzle.

9. The method as defined in claim 6, wherein the recesses of a same pair are identical.

10. The method as defined in claim 6, wherein the recesses of a same pair are nonidentical.

11. A pressure vessel arrangement having at least two adjacent components to be secured together at mating faces, one of the two components being a fuel nozzle, the arrangement comprising:

at least one pair of complementary rounded recesses forming a space, each recess being provided on the mating face of one corresponding component, and

one rounded element snugly fitted in the space of one corresponding pair of complementary recesses.

12. The positioning arrangement as defined in claim 11, wherein the rounded element is a spherical ball.

13. The positioning arrangement as defined in claim 11, wherein the recesses of a same pair are identical.

14. The positioning arrangement as defined in claim 11, wherein the recesses of a same pair are nonidentical.