Patent Application
20130336785
This disclosure relates to improvements in coupling rotors together.
Turbomachines, such as gas turbine engines, typically include a compressor section and a turbine section that is coupled for rotation with the compressor section. The compressor section may include one or more stages of compressor rotors and the turbine section likewise may include one or more stages of turbine rotors. One or more of the compressor rotors can be axially held together with one or more of the turbine rotors using a tie rod, for example. However, if the tie rod connection is lost, one or more of the rotors could move axially, resulting in an over speed condition.
A rotor assembly according to an exemplary aspect of the present disclosure includes a first rotor including first tabs, a second rotor arranged coaxially with the first rotor which includes second tabs that are interlocked with the first tabs, and a retainer locking the first tabs and the second tabs together.
In a further non-limiting embodiment, each of the first tabs and each of the second tabs includes a base and a free end and extends radially inwardly from the base to the free end.
In a further non-limiting embodiment of any of the foregoing examples, the first tabs and the second tabs define a circumferential channel.
In a further non-limiting embodiment of any of the foregoing examples, the circumferential channel opens in a radially inward direction.
In a further non-limiting embodiment of any of the foregoing examples, the retainer is located in the circumferential channel.
In a further non-limiting embodiment of any of the foregoing examples, the retainer is a split ring.
In a further non-limiting embodiment of any of the foregoing examples, the retainer is a positive engagement member.
In a further non-limiting embodiment of any of the foregoing examples, the positive engagement member is a split ring.
In a further non-limiting embodiment of any of the foregoing examples, the split ring includes radially inwardly projecting hooks.
In a further non-limiting embodiment of any of the foregoing examples, the first rotor and the second rotor each include a number (N) of airfoils, and the first rotor and the second rotor each include a number (T) of, respectively, the first tabs and the second tabs such that N is a positive integer multiple of T.
In a further non-limiting embodiment of any of the foregoing examples, the positive integer multiple is 2.
In a further non-limiting embodiment of any of the foregoing examples, the second tabs are circumferentially interlocked with the first tabs.
In a further non-limiting embodiment of any of the foregoing examples, the first rotor includes a first projection extending axially and located radially outwards of the first tabs and the second rotor includes a second projection extending axially and located radially outwards of the second tabs, the second projection axially overlapping the first projection and radially bearing against the first projection.
A turbomachine according to an exemplary aspect of the present disclosure includes a compressor section and a turbine section coupled to rotate with the compressor section. The turbine section includes a first rotor having first tabs, a second rotor arranged coaxially with the first rotor and having second tabs that are interlocked with the first tabs, and a retainer coupling the first tabs and the second tabs together.
In a further non-limiting embodiment of any of the foregoing examples, each of the first tabs and each of the second tabs include a base and a free end and extends radially inwardly from the base to the free end.
In a further non-limiting embodiment of any of the foregoing examples, the first tabs and the second tabs define a circumferential channel that opens in a radially inward direction, and the retainer is located in the circumferential channel.
In a further non-limiting embodiment of any of the foregoing examples, the compressor section includes a compressor rotor, and the compressor rotor, the first rotor and the second rotor are axially held together by a tie rod.
A method of coupling a first rotor and a second rotor together according to an exemplary aspect of the present disclosure includes interlocking first tabs of a first rotor with second tabs of a second rotor that is arranged coaxially with the first rotor and locking the first tabs and the second tabs together using a retainer.
In a further non-limiting embodiment of any of the foregoing examples, the interlocking of the first tabs with the second tabs includes establishing a circumferential channel that opens in a radially inward direction.
In a further non-limiting embodiment of any of the foregoing examples, the locking of the first tabs and the second tabs together includes inserting the retainer into the circumferential channel.
The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
The turbomachine 20 generally includes a compressor section 24 having a compressor rotor 24a and a turbine section 26 having a first rotor 26a and a second rotor 26b. For example, the first rotor 26a and the second rotor 26b are considered to be two stages of the turbine section 26, such as high pressure turbine stages of a gas turbine engine.
A tie rod 28 axially holds the compressor rotor 24a, the first rotor 26a and the second rotor 26b together. The compressor rotor 24a and the first rotor 26a are mounted on a common shaft 30 such that the first rotor 26a and the compressor rotor 24a are rotatable in unison. The second rotor 26b is coupled for rotation with the first rotor 26a through a locking mechanism 32, which is shown schematically in
The operation of the turbomachine 20 is generally known and is represented by the flow path 34 there through. The compressor section 24 compresses air and communicates the compressed air into the combustor 22. The compressed air is mixed and burned with fuel in the combustor 22, then expanded over the turbine section 26. It is to be understood that the turbomachine 20 is shown highly schematically and may include additional compression stages and additional turbine stages, as well as a fan, for example.
The tabs 40a/40b extends both axially and radially from the respective rotors 26a/26b. Thus, the first tabs 40a extend axially rearwardly from the first rotor 26a and the second tabs extend axially forwardly from the second rotor 26b. Each of the first tabs 40a and each of the second tabs 40b include a base 42 and a free end 44 such that each of the tabs 40a/40b extends radially inwardly from the respective base 42 toward the free end 44.
When interlocked, the first tabs 40a and the second tabs 40b define a circumferential channel 46. A retainer 48 is located in the circumferential channel 46 to lock the first tabs 40a and the second tabs 40b together. Thus, the first rotor 26a and the second rotor 26b are coupled together for co-rotation through the locking mechanism 32. In other words, the interlocking of the first tabs 40a and the second tabs 40b circumferentially and rotationally locks the first rotor 26a and the second rotor 26b together. The retainer 48 within the circumferential channel 46 defined by the first tabs 40a and the second tabs 40b prevents or limits relative axial movement between the first rotor 26a and the second rotor 26b. Thus, the rotors 26a/26b are rotationally and axially coupled together. The rotational and axial coupling of the first rotor 26a and the second rotor 26b ensures that the second rotor 26b will not axially disengage from the first rotor 26a in the case that the connection provided by the tie rod 28 is lost. Furthermore, the locking mechanism is compact and can be used as a design replacement where packaging considerations do not permit other bolted or other types of locking designs.
To further facilitate coupling of the rotors 26a/26b, the first rotor 26a includes an axial projection 60a and the second rotor 26b includes an axial projection 60b. The axial projections 60a/60b axially overlap and radially bear against one another at bearing surface 62. A thrust bearing surface 64 reacts axial loads and acts as an axial stop in assembling the rotors 26a/26b together. In operation, friction at the bearing surfaces 62 and 64 limits relative rotational and axial movement between the rotors 26a/26b.
In a further example, the first rotor 26a and the second rotor 26b each include a number N of airfoils 70, shown in part in
Selecting the number N to be the positive integer multiple of the number T ensures that the rotors 26a/26b are balanced with regard to the stress generated on each of the tabs 40a/40b. Further, the positive integer multiple also ensures that the tabs 40a/40b are clocked to the position of the airfoils 70. For instance, in one example where the positive integer multiple is 2, there would be one tab 40a or 40b per two airfoils 70 on the respective first rotor 26a or second rotor 26b. Additionally, the positive integer multiple of 2 facilitates selection of a proper size of the tabs to carry the torque between the first rotor 26a and the second rotor 26b. For instance, a relatively larger number of tabs 40a/40b would require a relatively small individual cross-sectional tab area and corresponding relatively low strength. On the other hand, for a relatively small number of the tabs 40a/40b would require a relatively greater cross-sectional tab area and a corresponding greater strength, but at a weight penalty. The positive integer multiple of 2 provides a desirable balance between the stress that each tab would see in operation and size of the tabs to accommodate those stresses.
Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.
