EP2539544A2

EP2539544A2 - Blade comprising pre-wired sections

Info

Publication number: EP2539544A2
Application number: EP11711017A
Authority: EP
Inventors: Sergio Elorza Gomez; Peter EIBELSHÄUSER
Original assignee: MTU Aero Engines GmbH
Current assignee: MTU Aero Engines AG
Priority date: 2010-02-27
Filing date: 2011-01-29
Publication date: 2013-01-02
Also published as: WO2011103849A3; DE102010009615B4; WO2011103849A2; DE102010009615A1; US9435207B2; US20120315148A1

Abstract

The invention relates to a method for wiring sections ((i), (i+1)) of a blade (1) for a blade row of a turbomachine. According to said method, a first central component (formula (II)) of a second section ((i+1)) is selected according to at least one central component ((formula (IV)), x_CG(i), r_CG(i)) of a first section ((i)), especially according to formula (I) where: (i) is a variable of the first section; (i+1) is a variable of the second section; (formula (III)) is a central component of a section in the peripheral direction, preferably in the angular or radian measure; x_CG is a central component of a section in the axial direction; r_CG is a central component of a section in the radial direction; ß is a graduated angle of a section; and (formula (V)) is a peripheral incline, preferably in the angular or radian measure.

Description

Airfoil with threaded profile cuts

The invention relates to an airfoil for a blade of a turbomachine with threaded profile sections, in particular an airfoil of a compressor blade, and a method for threading profile sections of such a blade.

In particular, in order to adapt individual profile sections in the radial direction to flow conditions which vary radially above a channel height of a blade grid, in particular the flow vectors at entry and exit, it is for example from EP 0 798 447 A2 of the Applicant and DE 10 2006 055 869 A1 , known, the three-dimensional geometry (3D geometry) of an airfoil from successive profile sections in the radial direction,

preferably to construct 2D profile sections, i.e. to thread the profile sections. Both

Documents as well as DE 10 2005 042 115 A1, DE 34 41 115 C1 and DE 10 2005 025 213 AI deal with the geometry of the individual profile sections, in particular their skeleton lines.

In particular, in compressor blades with a sweep in the axial direction, due to circumferential threading, e.g. with circumferentially staggered profile sections, lateral bending stresses occur in the blade.

Object of the present invention is therefore to provide an improved airfoil for a

To provide blade grid of a turbomachine.

This object is achieved by a method having the features of claim 1 and a

Airfoil with the features of claim 8 or 9 solved. Advantageous developments are the subject of the dependent claims.

According to the invention, profile sections of an airfoil are threaded in such a way that a first center point component of a second profile section is selected as a function of at least one midpoint component of a first profile section.

The midpoint position of a profile section can in particular be the position i * c of its

Space center with the components X in the axial direction, rc in the radial direction and rc in the circumferential direction and the vector rdF to the infinitesimal element dF of the profile section F, preferably the position # * CG of its center of mass or center of gravity

with the vector ^ M to the infinitesimal mass element dM and the corresponding one

Center point components XCG in the axial, TCG in radial direction and ®CG in the circumferential direction, wherein in particular reference is made to a usual coordinate system whose axial coordinate with a longitudinal axis of the flow grid or the turbomachine is aligned.

According to the invention, preferably recursively, at least one of these components, which for the sake of greater compactness is referred to as the first center point component, is then formed for a second profile section as a function of one or more center point components of one, preferably radially outwardly preceding one, i.e. selected radially inward, first profile section. This allows for optimal threading of subsequent ones

Profile cuts with respect to their midpoint positions.

In this case, according to a preferred embodiment, the individual profile sections, in particular their geometry or outer contour, are designed in advance in terms of fluid, in particular aerodynamically, preferably optimized, and then according to the invention, i.e. in dependence of

Center point components of a previous profile section threaded. In this way, both fluid dynamic and strength requirements separately and thus optimally taken into account.

According to a preferred embodiment, a first selected according to the invention

Center point component of the second profile section additionally selected as a function of its graduation angle and / or in dependence on a stagger angle of the first profile section. As staggering or blade angle ß of a profile section is doing in the usual way, in particular the schaufelanfangs-, or blade end

Stagger angle or angle denoted by a chord between blade inflow and vane trailing edge or a profile skeleton line with a lattice plane of the blade lattice. Additionally or alternatively, the first center point component of the second profile section can also be dependent on at least one other, second

Center point component of the second profile section are selected. For example, for fluid dynamics reasons, first, an axial center location, i.e. a

Mid-point component in the axial direction, determined for the second profile cut, and then its mid-point circumferential position, i.e. its midpoint component in

Circumferential direction to be selected depending on this axial center position.

If, for example, the mass mean or center of gravity or position of a radially inner first profile section (i) is known by its position or position xcofi) in axial, rcG) in radial and ®CG (in the circumferential direction and its stagger angle β ( _t ), and the axial and radial positions xcGft + i), fcGfi + i) of the center of mass of a radially adjacent second

Profile section as well as its stagger angle ßp + ij given, for example due

fluid dynamic conditions, then obeyed in accordance with a preferred embodiment of the

Midpoint circumferential position ®cG (t + i) of the second profile section (i + 1) at least approximately the relationship

®C6 ( ₊ D = © _{CG (i)} (2)

where "tan" and "arctan" in common nomenclature denote the tanges and arctangent of an angle. It can be seen that the offset (.DELTA.cG (i + i) -C.sub.CG) of the center of gravity of the second profile section relative to the first profile section in the circumferential direction of the offset (xcGfi + i) - xcGfi)) in the axial direction and an average value (cGfi + i) + ^ CG ^) / 2 for the radial position and an averaged stagger angle (ßcGfl + i) + depends.

Preferably, substantially all profile sections of the airfoil at least approximately obey this relationship. In particular, to compensate for local loads, however, it may be advantageous if radially inner profile section deviate from this. Therefore, preferably at least radially outer profile sections meet the above relationship, in particular all profile sections from 35% of a channel height of the blade grid, preferably from 25% of the channel height upwards.

For simplification, instead of the mean value (rcGβ + i) + rcG (i ₎ ) 12, the radial position rcG (i) or rcGfi + i) of the first or second profile section may also be used, so that the Center point circumferential position ®cG (i + i) of the second profile section (i + J) at least approximately, for example, the relationship

®CG (/ ₊ D = ⁰ CG () + Arctane (2 ')

obeys. Additionally or alternatively, the stagger angle ß ^ or ß ( _{i +} i) of the first or second profile section can be used approximately, so that the

Center point circumferential position ®CG (I + I) of the second profile section at least approximately, for example, the relationship

(CG (/ + 1) ^X CG [i])

®CG (W ₎ = ®cs _(/) + arctane tan (? _{(I + 1)} ) (2 ")

'CG (/ + 1) obeys.

For example, to compensate for fluid, in particular gas forces, the blade can be inclined in the circumferential direction by the angle ® _{\ ean} . Then, the center-point circumferential position .RTM.CG (t + i) of the second profile section (i + 1) according to one of the above-explained relationships, the term

Aresin V CS (/ + 1) ^R CG (1), sin (©, _ean ) (3)

'CG (/ + 1) may be added such that the midpoint circumferential position ®CG (I + I) of the second profile section (i + 1) is at least approximately equal to the relationship

Θ

obeys.

Other features and advantages will become apparent from the dependent claims and the

Embodiment. This shows, partially schematized: Fig. 1A is a meridional view of an airfoil with threaded profile sections according to the prior art;

Fig. 1B is an axial view of the airfoil of Fig. 1A; and

2 A, 2B an airfoil according to an embodiment of the present invention in FIG.

1 A or 1B corresponding view.

FIGS. 2A, 2B show, in meridional or axial view, an airfoil 1 of FIG

A compressor blade according to an embodiment of the present invention. By way of example, some threaded profile sections are drawn in, of which a second one is labeled "i + 1".

To generate the 3D geometry of this airfoil, the individual profile sections are first generated under aerodynamic aspects, for example by setting or optimizing their skeleton line and their design circles. Subsequently, starting with a radially innermost profile section at the bottom of the flow channel, the axial center of gravity positions of the profile sections are recursively specified. For each profile section at least from 25% of the height of the channel upwards (from bottom to top in Fig. 2) its center of gravity position in the circumferential direction according to the relationship (2) or (2 "') is chosen, then finally the complete, both in aerodynamic and in terms of strength optimal 3D geometry of this blade results without the need for time and cost-intensive aero-strength iterations must be performed.

In comparison with the blade 1 'according to the prior art shown in the corresponding view in FIGS. 1A, 1B, one recognizes the more favorable, curved course of the invention

Balance positions, which are connected in the figures by a line S and S ', above the channel height.

Claims

claims

Method for threading profile sections ((i), of an airfoil (1) for a blade grid of a turbomachine, characterized in that a first

Center point component (0cG ₍ i ₊ i ₎ ) of a second profile section depending on at least one center point component (0cG (i), * CG (i), ^ CG ©) of a first profile section ((i)).

A method according to claim 1, characterized in that the first

Center point component (0cG (i + i)) of the second profile section as a function of a stagger angle (? ₍ , ₎ , the first and / or second profile section selected

Method according to one of the preceding claims, characterized in that the first center point component (0cG (i + i)) of the second profile section ((i + 1)) in

Dependence on at least one second center point component (CG ₍ + I ₎ , rcG (i + i)) of the second profile section ((i + 1)).

Method according to one of the preceding claims, characterized in that the first center point component (0cG (i + i)) of the second profile section ((i + 1)) recursively in response to the, preferably radially outwardly preceding, first profile section ((i) ) is selected.

Method according to one of the preceding claims, characterized in that the first and second profile section are designed fluidically before threading.

Method according to one of the preceding claims, characterized in that, as the first center point component, a center point component (0cG (i + i)) of the second profile section ((i + 1)) in the circumferential direction substantially according to

is chosen with

in which

(0 a size of the first profile section;

(i + 1) a size of the second profile section;

Circumferential direction, preferably in angular or radian measure;

* CG a midpoint component of a profile section in axial

Direction;

reo a focal point component of a profile section in radial

Direction;

a stagger angle of a profile cut; and

a circumferential inclination, preferably in angular or radian.

A method according to claim 6, characterized in that the center point circumferential position (0cG (i + i)) for all profile sections according to

® CG _{(/ +} D = ®CG _(/) + ArctanfA * (x _{CG (i + 1)} - x _{CG (i)} ) · tan ßj + C is chosen, for which the difference (rcG (i + i) - ^ CG (i)) between her and one

Center point component in the radial direction of a radially inner channel bottom is at least 35%, in particular at least 25% of a channel height of the blade grid.

Blade (1) for a blade grid of a turbomachine, with a plurality of threaded profile sections ((i), characterized in that a first

Center point component (0cG (i + i)) of a second profile section ((i + 1)) is selected according to a method according to one of the preceding claims.

Airfoil (1) for a blade grid of a turbomachine with a

threaded profile sections ((i), (i + 1)), characterized in that a Center point component (0CG (I + I)) of a second profile section in FIG

Circumferential direction at least approximately the relationship

®CG ( ₊ D = ®c _{S ()} + arctane [A * (x _{ce (/ + 1)} -x _{CG (/)} ), tan βj + C

With

'CG ()

enough.

10. airfoil (1) according to at least one of the preceding claims 8 to 9, characterized in that the airfoil has a curvature in the circumferential direction and / or a sweep in the axial direction.