Blade cooling
In order to couple coolant air flow presented through a coolant gallery 4, 24 through an opening 7, 27 into a passage 8, 28 a flow deflector 6, 26 is provided. The flow deflector 6, 26 progressively deflects the coolant air flow 5, 25 through the opening 7, 27 such that there is reduced loss in coolant flow 5, 25 pressure.
The present invention relates to blade cooling and more particularly to arrangements for feeding coolant from a mounting disk or hub to turbine blades in a jet engine.
Cooling of turbine blades in a jet engine is important in order to maintain structural integrity whilst the blades operate at high temperatures approaching if not exceeding the melting point of the materials from which the blades are made. Turbine blades generally include a coolant passage network within their structure within which coolant air circulates in order to cool the blade. Such coolant air must be coupled to the coolant passage network within the blade. Generally, a central coolant supply system is coupled to the blade coolant passage network. Traditionally, a specific connecting hole or passage has been made in the mounting hub or disk to which the turbine blade is secured such that an opening in that blade is substantially aligned with the feed hole or passage in the mounting disk in order to present coolant to the blade coolant passage network. Fabrication of such feed holes in the mounting disk as well as reciprocal holes in the root or connecting end of the blade add significantly to fabrication costs as well as increased mechanical stress levels and their requirement for thicker material. Alternatively, a space can be created between the root end of the blade and the top surface of the mounting disk or hub. This space acts as a distribution gallery for openings connected to a coolant passage network of a blade. These distribution galleries are commonly referred to as a “bucket groove”. Essentially, within the distribution gallery there is a positive pressure differential such that coolant air presented at one end is drawn into the openings for the coolant passage network of the blade. Unfortunately, coolant flow in a distribution gallery is turned sharply at least twice as it passes to the coolant passage network of the blade. Such turning can diminish the pressure differential and so flow rate of coolant air into the blade cooling passage network. Clearly, a reduce flow rate will diminish cooling efficiency and therefore performance.
In accordance with the present invention, there is provided a blade cooling arrangement comprising a coolant gallery formed between a mounting hub and a blade root including at least one coolant passage opening and a flow deflector associated with that passage opening to deflect in use a coolant flow through the coolant gallery towards that passage opening.
Also in accordance with the present invention there is provided a flow deflector for a turbine blade, the deflector in use being arranged in a coolant gallery between a mounting hub and a blade root, the deflector associated with a coolant passage opening to deflect coolant flow in the gallery towards the passage opening whereby such deflection is progressive in order to limit coolant flow pressure loss upon entry through the coolant passage opening.
Preferably, the flow deflector is a curved scoop to progressively deflect the coolant flow towards the passage opening. Alternatively, the flow deflector is a ramp or wedge to lift coolant flow towards the passage opening to achieve angular flow overlap. Possibly, there is a plurality of flow deflectors to progressively deflect coolant flow towards the passage opening.
Possibly, the flow deflector extends upwards from the mounting hub towards the passage opening. Alternatively, the flow deflector extends downwardly from the blade root away from the passage opening.
Possibly, the flow deflector is adjustable dependent upon temperature or specific requirements. Typically, such adjustment is by variation in material dimensions as a result of differential expansion and/contraction relative to the mounting cup and/or the blade root. Alternatively, such adjustment may be through mechanical displacement under specific control by a control device.
Further in accordance with the present invention there is provided an engine including turbine blades having a blade cooling arrangement or a flow deflector as described above.
Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:
Referring to
In accordance with the present invention a flow deflector 6 located adjacent and around the opening 7 deflects the coolant flow 5 into the passage 8 through the opening 7. The deflector 6 is substantially flat and creates a wedge or ramp to progressively deflect the coolant flow 5 through the opening 7. In such circumstances, there is less direct or perpendicular collision by the coolant flow onto the deflector 6 such that a diminution in the net positive pressure drawing the coolant flow 5 through the gallery 4 into the passage 8 is not significantly diminished. The flow deflector 6 essentially acts as a scoop for coolant air flow 5 into the passage 8.
As indicated above, the flow deflector 6 is located substantially around the hole or passage opening 7 such that coolant air flow can pass either side of the deflector 6 to be come incident upon other flow deflectors in the gallery 4.
As illustrated in
As illustrated in
It is an objective of the flow deflector 6 in accordance with the present invention to provide progressive deflection of the coolant flow 5. Thus, a number of flow deflectors could be utilised in order to act in concert such that there is gentle and progressive deflection of the coolant flow with limited positive pressure loss upon entry to the passage 8 through the opening 7. It will be understood that air coolant flow through the passage 8 and then into the coolant passage network of the blade 3 is highly determinant of the cooling efficiency within that blade 3. In such circumstances, a greater degree of cooling may be achieved to allow the blade to operate at higher temperatures and therefore an associated engine to work more efficiently. Alternatively, a lower volume of coolant air may be necessary in order to provide a required level of cooling for engine operation and such a lower volume of air coolant flow will also improve pro rata engine efficiency.
A number of flow deflectors may be provided to cause deflection. Thus, a primary flow deflector marked by a dotted line and numeral 10 may be provided in order to create initial coolant flow deflection which is further deflected by the flow deflector 6. However, care should be taken that the impingement by the flow deflector 10 does not create a throttle choking effect by diminishing the cross-sectional area of the gap between the top of the deflector 10 and the bottom of the blade root end 2. The flow deflector 10 may comprise a material which expands in order to create the wedge or ramp shape depicted in
The flow deflector 26 has a curved surface 30 which acts as a scoop in order to progressively deflect the coolant air flow 25 through the opening 27 into the passage 28. Thus, the flow deflector 26 acts substantially in the same fashion as that described with respect to flow deflector 6 (
Typically, as illustrated in
Normally, as illustrated in
It will be understood that the flow deflector 26 as with flow deflector 6 (
Specific choice of the angle of inclination for the wedge or ramp configuration of flow deflector 6 (
The principal function of a flow deflector 6, 26 is to deflect a lateral coolant air flow 5, 25 along the distribution gallery 4, 24 into an opening 7, 27 which is perpendicular to that flow 5, 25. Thus, if the coolant air flow is considered a planar front, the deflector 6, 26 deflects that planar front such that there is greater overlap with the plane of the opening 7, 27 for entry. Ideally, the planar deflection should be in the order of 90° or that required for in-line incidence but normally a balance is struck between the severity of deflection (which effects net positive pressure loss) and the level of flow planar front overlap with the opening 7, 27 (alignment would be an ideal coupling of flow into the opening 7, 27 but normally the deflected flow planar front will be skew of the plane of the opening).
Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.
Claims
1. A blade cooling arrangement comprising a mounting hub and a blade root having a coolant gallery formed between said hub and said root and including at least one coolant passage opening and a flow deflector associated with that passage opening to deflect coolant flow through the coolant gallery towards the passage opening wherein the flow deflector is positioned in the coolant gallery and extends from one side across said coolant gallery to engage the other side of said coolant gallery.
2. A flow deflector arrangement for a turbine blade, the arrangement comprising a mounting hub and a blade root having a coolant gallery formed therebetween, and flow deflector positioned adjacent the coolant passage opening in said coolant gallery, the deflector associated with a coolant passage opening to deflect coolant flow in the gallery towards the passage opening whereby such deflection is progressive in order to limit coolant flow pressure loss upon passage through the coolant passage opening.
3. An arrangement as claimed in claim 1 wherein the flow deflector has a curved surface to progressively deflect the coolant flow towards the passage opening.
4. An arrangement as claimed in claim 1 wherein the flow deflector is a ramp or wedge to lift coolant flow towards the passage opening to achieve progressive deflection of the coolant flow towards that passage opening.
5. (canceled)
6. An arrangement as claimed in claim 1 wherein the flow deflector extends upwardly from the mounting hub towards the passage opening.
7. An arrangement as claimed in claim 1 wherein the flow deflector extends downwardly from the blade root away from the passage opening.
8. An arrangement as claimed in claim 1 wherein the flow deflector is adjustable dependent upon specific requirements.
9. An arrangement as claimed in claim 8 wherein adjustment of the flow deflector is by variation in material dimensions as a result of one of differential expansion and contraction relative to one of the mounting hub and the blade root.
10. (canceled)
Type: Application
Filed: Sep 25, 2006
Publication Date: Feb 8, 2007
Inventor: Roderick Townes (Derby)
Application Number: 11/525,931
International Classification: F01D 5/18 (20060101);