Method for operating a compressor of a turbomachine comprising providing a plurality of stages in a front compressor area, a rear compressor area, and allowing a swirl in the rear compressor area

Abstract

Described is a method for operating a compressor of a turbomachine, in which, when considered in the direction of a main flow, an, in particular, radially averaged degree of reaction has dropped in a front compressor area from a maximum to a minimum, is held constant or virtually constant across a central compressor area up into a rear compressor area, an, in particular, radially averaged degree of reaction being adjusted in the rear compressors area which is closer to the minimum than to the maximum, and a residual swirl of at least 47 is present in the middle section, and a compressor and a turbomachine.

Claims

1. A method for operating a compressor of a turbomachine, the method comprising: providing a plurality of stages in a front compressor area so that a radially averaged degree of reaction in the front compressor area drops, with respect to a main flow direction, from a maximum at a first stage of the plurality of stages in the front compressor area to a front compressor area minimum at a further stage of the plurality of stages of the front compressor area downstream from the first stage; providing a rear compressor area with a plurality of rear compressor area stages and an outlet guide baffle so that the radially averaged degree of reaction of the plurality of rear compressor area stages in the rear compressor area is closer to the front compressor area minimum than to the maximum; and the rear compressor area allowing a swirl in the rear compressor area downstream from at least one of the plurality of rear compressor stages in front of the outlet guide baffle to be between 47 and 60 in a middle section.

2. The method as recited in claim 1 wherein the degree of reaction is adjusted to equal 0.5 to 0.6.

3. The method as recited in claim 1 wherein a value of a local degree of reaction at half a radial height between a compressor hub and a compressor housing is less than each of a hub-side degree of reaction and a housing-side degree of reaction.

4. The method as recited in claim 1 wherein the front compressor area has a plurality of rows of adjustable guide blades, central compressor area between the front compressor area and the rear compressor area has a plurality of nonadjustable rows of guide blades, and rear compressor area has a plurality of rows of nonadjustable guide blades and a last row of guide blades defining the outlet guide baffle.

5. A method for operating a compressor of a turbomachine, the compressor having a front compressor area having a plurality of rows of adjustable guide blades, a central compressor area having a plurality of nonadjustable rows of guide blades, and a rear compressor area having a plurality of rows of nonadjustable guide blades and a last row of guide blades defining an outlet guide baffle, the method comprising: providing a plurality of stages in a front compressor area so that a radially averaged degree of reaction in the front compressor area drops, with respect to a main flow direction, from a maximum at a first stage of the plurality of stages in the front compressor area to a front compressor area minimum at a further stage of the plurality of stages of the front compressor area downstream from the first stage; providing a rear compressor area with a plurality of rear compressor area stages and an outlet guide baffle so that the radially averaged degree of reaction of the plurality of rear compressor area stages in the rear compressor area is closer to the front compressor area minimum than to the maximum; and the rear compressor area allowing a swirl angle in the rear compressor area downstream from at least one of the plurality of rear compressor stages in front of the outlet guide baffle to be between 50 and 60 in a middle section.

6. The method as recited in claim 5 wherein the radially averaged degree of reaction is adjusted to equal 0.5 or higher.

7. The method as recited in claim 5 wherein a value of a local degree of reaction at half a radial height between a compressor hub and a compressor housing is less than each of a hub-side degree of reaction and a housing-side degree of reaction.

8. The method as recited in claim 1 wherein a value of a local degree of reaction at half a radial height between a compressor hub and a compressor housing is less than at least one of a hub-side degree of reaction and a housing-side degree of reaction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred exemplary embodiments of the present invention are subsequently described in greater detail with the aid of schematic illustrations.

(2) FIG. 1 shows a diagram to define a compressor-side degree of reaction,

(3) FIG. 2 shows curves of the radially averaged degree of reaction according to the present invention in the longitudinal compressor direction in comparison to a curve of a known compressor-side degree of reaction, and

(4) FIG. 3 shows a radial curve of a degree of reaction according to the present invention in comparison to a radial curve of a known compressor-side degree of reaction.

DETAILED DESCRIPTION

(5) As already mentioned at the outset, FIG. 1 shows how a compression-side degree of reaction of a turbomachine may be calculated. This calculation or this understanding is also based on the degrees of reaction according to the present invention.

(6) The local degree of reaction R is consequently calculated according to the following formula:

(7) $R=\frac{\tan \frac{1+2}{2}}{\tan \frac{1+2}{2}+\tan \frac{1+2}{2}}$

(8) The angles 1, 2, 1, 2 are, as shown in FIG. 1, are marked between tangents of the respective camber line and an axial flow direction x of the turbomachine. 1 is marked from the trailing edge of a guide blade 2 of a row of guide blades n1. 2 is marked toward the leading edge of a guide blade 4 of a row of guide blades n. 1 is marked toward the leading edge of a moving blade 6 of a row of moving blades n. 2 is marked from the trailing edge of moving blade 6 of a row of moving blades n. Moving blade 6 or row of moving blades n thereby passes through between guide blades 2, 4 or rows of guide blades n1, n in circumferential direction u. Letter n designates whole number multiples of 1, 2, etc.

(9) FIG. 2 shows curves according to the present invention of a radially averaged degree of reaction 8a, 8b of a compressor of a turbomachine, in particular an aircraft engine, in comparison to a conventional curve of a radially averaged degree of reaction 10.

(10) Degrees of reaction 8a, 8b, 10 are outlined in the longitudinal direction of the compressor or in flow direction x of a main flow flowing through the turbomachine across a front compressor area 12, a central compressor area 14, and a rear compressor area 16. Front compressor area 12 is formed on the stator side, for example, by three adjustable rows of guide blades. Central compressor area 14 has on the stator side a plurality of non-adjustable rows of guide blades. Rear compressor area 16 has on the stator side, in addition to a plurality of non-adjustable rows of guide blades, an outlet guide baffle 18, in particular as a last row of guide blades. The dimensions of compressor areas 12, 14, 16 shown in FIG. 2 in flow direction x are purely exemplary and may also naturally vary. Thus, for example, front area 12 may also have fewer than three rows of guide blades or more than three adjustable rows of guide blades, such as, for example, five rows of guide blades.

(11) Conventionally, radially averaged degree of reaction 10 drops in front compressor area 12 from a maximum, for example 0.7, sharply to a minimum, for example 0.6. At the beginning of central compressor area 14, conventional degree of reaction 10 rises slowly up to outlet guide baffle 18 of rear compressor area 16. Consequently, all guide blades in central compressor area 14 and in rear compressor area 16 are strongly loaded and the efficiency in rear compressor area 16 decreases sharply.

(12) According to the present invention, degree of reaction 8a, 8b is now adjusted in such a way that, after the sharp drop in front compressor area 12 from a maximum to a minimum, it is held constant or virtually constant at the minimum, in this case 0.5, across central compressor area 14 up into rear compressor area 16 and in particular up to outlet guide baffle 18. Consequently, the stator-side load of rear compressor area 16 is generally reduced and thus the efficiency is increased. Only outlet guide baffle 18 is strongly loaded by the residual swirl of the main flow, which is to be reduced. Preferably, a residual swirl of at least 47 in relation to flow direction x is present in the middle section. Residual swirl angles of 50 to 60 are also possible.

(13) Structurally, the degree or reaction curves according to the present invention may be achieved in that either a stator-side and/or rotor-side sidewall contouring, such as hub-side sidewall contouring 128 or housing-side sidewall contouring 130 (shown schematically in FIG. 3), preferably a non-circumferentially symmetrical sidewall contouring, is carried out in outlet guide baffle 18 (degree of reaction 8b). Alternatively or supplementally, outlet guide baffle 18 is designed in a tandem form shown schematically in FIG. 2 (degree of reaction 8a). Consequently, the degree of reaction curve may fundamentally be held closer to the minimum than in the case of pure sidewall contouring.

(14) According to FIG. 3, it is preferred if an average value 20 of degree of reaction 8a, 8b at half the radial height between the compressor hub and the compressor housing is reduced compared to an average value 22 at a linear radial curve 24. Linear curve 24 is thereby such that a hub-side value 28 of the degree of reaction is lower than a housing-side value 30 of degree of reaction 8a, 8b. Due to the reduction of the average degree of reaction value, a trough-shaped radial curve 26 or degrees of reaction 8a, 8b results, whereby the sidewall-side degree of reaction values 30, 28 are increased compared to linear curve 24. This effectuates a stabilization of the sidewall boundary layer and thus results in an increase of the surge margin so that the stability of the compressor is increased due to the reduction of the average value of degree of reaction 8a, 8b compared to an original linear curve 24.

(15) A method for operating a compressor of a turbomachine is described, in which, when considered in the direction of a main flow, an, in particular, radially averaged degree of reaction has dropped in a front compressor area from a maximum to a minimum, is held constant or virtually constant across a central compressor area up into a rear compressor area, an, in particular, radially averaged degree of reaction being adjusted in the rear compressor area which is closer to the minimum than to the maximum, and a residual swirl of at least 47 being present in the middle section, and a compressor and a turbomachine.

LIST OF REFERENCE NUMERALS

(16) 2 guide bladestage n1 4 guide bladestage n 6 moving bladestage n 8a degree of reaction 8b degree of reaction 10 degree of reaction 12 front compressor area 14 central compressor area 16 rear compressor area 18 outlet guide baffle, tandem 20 average value 22 average value 24 linear curve 26 trough-shaped curve 28 hub-side value 30 housing-side value 128 hub-side sidewall contouring 130 housing-side sidewall contouring R degree of reaction x flow direction u circumferential direction