EP0131719B1 - Adjustable guiding apparatus - Google Patents

Abstract

A variable control mechanism for a turbine engine, in particular an exhaust gas turbine of a turbocharger, with a ring of guide blades arranged concentrically around a rotor axle and pivoting around pivot axles between end limits. The pivot axles are arranged in the forward areas associated with the inflow edges of the guide blades; one of the end limits being variable by means of an adjusting ring or the like. Clearance and impact losses are incurred depending on the prevailing setting of the guide blades. The invention provides a guide mechanism which can be constructed inexpensively and which reduces clearance and impact losses. The guide blades are arranged such that they can pivot freely within an angular setting range defined by the end limits. In case of a low load the guide blades pivot freely within the predetermined end limits, and with rising loads they abut against the variable end limit.

Description

The invention relates to an adjustable guide device of an exhaust gas turbine, in particular a turbocharger, with a ring of guide vanes arranged concentrically around a rotor axis, which are each pivotable between two end boundaries about pivot axes, which are arranged in the front area of the guide vanes assigned to the outflow edges, whereby means of an adjustment ring the end limits are adjustable.

DE-A-23 29 022 describes an adjustable guide apparatus for the guide vanes of a gas turbine, the guide vanes of which are arranged so as to be pivotable about pivot axes. To pivot the guide vanes, they have lateral pins in the area of their leading edges, which engage in axial guide grooves of an adjusting ring. The guide vanes can be pivoted between end limits by means of the adjusting ring, but the guide vanes cannot be pivoted freely. The guide vanes are positively guided in each operating area of the gas turbine in accordance with the setting of the adjusting ring.

A radial compressor is known from US-A-39 57 392, the diffuser ring of which has movable blades in order to ensure that it operates in a stable region. The unstable area should be avoided in particular with regard to so-called pumping and stalling. A spring engages on the axes of the blades in order to prevent the blades from fluttering, particularly in the vicinity of the surge line. These springs are a necessary prerequisite and there is no free movement of the blades. There is no adjustment ring for the defined specification of an angular position or a setting angle range and the blades can only pivot between the end limits fixed for the respective construction.

Furthermore, from US-A-40 29 433 a turbomachine with flexible, namely, bendable, blades is known. These blades are set using their flexibility in a defined manner, whereby there is no free swiveling under the flow forces. To adjust the blades, an axially displaceable sleeve with triangular recesses is used, into each of which a pin of a guide blade projects. The radially inner ends of the blades are held in place by means of a hub. When the radially outer sleeve is axially displaced, the blades are three-dimensionally deformed or twisted.

The invention has for its object to propose a guide device of the type mentioned, which has a comparatively simple construction and in which the adjusting forces can also be applied in one direction only. In addition, gap and / or impact losses are to be reduced with a view to low consumption. Finally, it should also be possible to introduce the adjusting force to the adjusting ring in a simple manner and, moreover, also at the desired location. A compact and weight-saving structure and also a high level of operational reliability are to be achieved. Furthermore, a functional adjustment to the operational requirements and the installation conditions should be given with a low weight.

To solve this problem, it is proposed that the adjusting ring for the guide vanes have contact surfaces which form an end limitation for the respective guide vane, that the guide vanes are freely pivotable under the flow forces in the angular range adjustable by means of the adjusting ring, and that the adjusting ring is inside the flow channel is arranged and / or forms part of the wall of the flow channel.

The proposed diffuser has a comparatively simple construction, and adjusting forces can only be applied in one direction. During normal operation or in the partial load range, the guide vanes are automatically adjusted within the limits specified by the end limits in accordance with the direction of the streamline. This results in a not inconsiderable reduction in gap and impact losses in the partial load range if no or even a low boost pressure is required for the engine. In this operating range, the freely pivotable guide vanes are thus set to "minimum loss" without the need for a high level of control and regulation, as would be necessary with positively driven guide vanes. In addition, it must be noted that consistent results are achieved with increased boost pressure in comparison with fully guided guide vanes. The guide device has a high level of operational reliability with a simple construction, the adjusting force being able to be introduced practically at any desired point; an adaptation to the respective installation conditions can be done without difficulty. The adjustment ring can be formed in one piece or consist of several individual parts or segments. The swiveling guide vanes are not adjusted by an external torque acting on their swivel axes, but can be swiveled freely in the partial load range between the variable end limits. On the other hand, the guide vanes are subjected to further loads due to the vane forces resulting from the flow, which act between the pivot axis and the adjustable end limit, by the end limit in each case predetermined maximum possible angle turned up. In the case of a turbocharger, the end limit can be set, for example, according to the charge pressure characteristic. It is not necessary to emphasize that in other exhaust gas turbines the adjustability can be made in accordance with the appropriate parameters. It can be seen that, due to the adjustability as a function of preselectable parameters, an optimal adaptation to the respective requirements and operating conditions can be carried out.

In a special embodiment, the guide device for a centripetal flow-through impeller is characterized in that the adjusting ring has the sawtooth-shaped contact surfaces for the free ends of the guide vanes on projections directed towards the flow channel. The sawtooth-shaped bearing surfaces are at a smaller distance from the rotor axis than the pivot axes. The curve shape can be specified according to the respective requirements. The curves are expediently predefined in such a way that a displacement angle of the displacement ring is also associated with a defined displacement angle of the blades, and above all a linear dependency can be predefined without difficulty.

In a further embodiment, the contact surfaces of the adjusting ring are arranged in guide grooves, in which the guide vanes each engage with a lateral pin. Due to the lateral arrangement of the pin, the passage area between the guide vanes remains free.

In an alternative embodiment, the contact surfaces of the adjusting ring are each arranged on a guide pin which engages in a guide groove provided on the end face of the guide vane or on which the guide vane rests with the profile side located downstream. In this embodiment, the guide pin, which is expediently connected directly to the adjusting ring, forms a reliable support or delimitation for the guide vane, with a low manufacturing effort also being required here.

In a further embodiment of the guide apparatus, the contact surface for an axially flowed through impeller is arranged on an axial end face of the adjusting ring designed as a hollow ring, on which end face the free ends of the guide vanes partially rest. In this embodiment, too, the adjusting ring is located behind the swivel axes in the flow direction, so that the unscrewing caused by the blade forces is limited by the free ends abutting the adjusting ring.

In an alternative embodiment, at least two guide vanes are coupled to one another and are freely pivotable together. The individual guide vanes can therefore no longer be freely pivoted independently of one another, but rather the guide vanes which are coupled to one another can be freely pivoted together. Within the scope of this invention, the individual blades are thus combined into groups distributed over the circumference. The guide vanes which are coupled to one another consequently have the same angle of attack, which ensures a particularly uniform flow against the turbine wheel. In addition, due to the coupling of different guide vanes according to the invention, disadvantageous oscillation or fluttering, which may occur in the case of individual blades, can be prevented. Of the total number of guide vanes, two are connected to each other, with more than two blades being connected to one another in accordance with the respective requirements, in particular by means of a lever or the like.

• Fig. 1 schematisch einen Längsschnitt durch eine Abgasturbine,
• Fig. 2 teilweise eine Ansicht in Blickrichtung A) bzw. einen Schnitt entlang Schnittlinie II gem. Fig.1,
• Fig. 3 eine prinzipielle Darstellung eines Axialschnittes durch den Strömungskanal von Axial-Leitschaufeln,
• Fig. 4 teilweise eine in die Zeichenebene projezierte Ansicht in Blickrichtung B) gem. Fig.3,
• Fig. 5 eine Ansicht ähnlich Fig. 4, wobei jedoch drei Leitschaufeln mittels eines Hebels aneinander gekoppelt sind.

Embodiments of the invention are explained below with reference to the drawing. Show it:

• 1 schematically shows a longitudinal section through an exhaust gas turbine,
• Fig. 2 partially a view in viewing direction A) or a section along section line II acc. Fig.1,
• 3 shows a basic illustration of an axial section through the flow channel of axial guide vanes,
• Fig. 4 partially a view projected into the plane of the drawing in viewing direction B) acc. Fig. 3,
• FIG. 5 is a view similar to FIG. 4, but with three guide vanes coupled to one another by means of a lever.

1 shows, purely schematically, an exhaust gas turbine with an impeller 2 through which there is a centripetal flow. A spiral inflow channel 4 is present, through which the exhaust gas flowing radially inward reaches the guide vanes 6 distributed over the circumference in the usual way. The guide vanes 6 are arranged in a housing 8 so as to be pivotable about a pivot axis 10, the pivot axis being located in the region of the leading edge 11. In the housing 8, an adjusting ring 14 which is rotatable in a suitable manner about the rotor axis 12 is also arranged. The free, radially inward-pointing ends 16 of the guide vanes rest on a projection 18 of the adjusting ring 14. The adjusting ring 14 or the projection 18, corresponding projections also being provided for the other guide vanes distributed over the circumference, has a sawtooth-shaped contour to be explained below. These projections 18 create 6 inner end boundaries for the respective guide vanes, against which the guide vanes bear with increasing load; otherwise the guide vanes are freely pivotable about their pivot axis 10. By means of suitable adjusting means, which are preferably pneumatic or are also mechanically designed, the adjusting ring 14 can be set in the desired angular position with respect to the rotor axis 12.

Fig. 2 shows in the left part a view in viewing direction A and also in the right part a section along section line II acc. Fig. 1. The adjusting ring 14 has on its radial outer surface the sawtooth-shaped projections 18, with each guide vane 6 being associated with such a projection 18. The drawing shows the position in which the flow cross-section between the guide vanes is greatest. The flow cross section is reduced by rotating the adjusting ring 14 about the rotor axis 12 in the direction of the arrow 20. The free ends 16 of the guide blades 6 are moved outward on the sawtooth-shaped contour in the radial direction. The adjustment ring 14 designed in this way creates the inner variable end limit for the guide vanes 6. In this embodiment according to the invention, the outer end limitation is formed by the next following guide vane in each case in the circumferential direction. At low loads, the guide vanes 6 adjust themselves according to the pressure and flow conditions between these two end limits, as a result of which gap and impact losses are reduced to a minimum and consequently, in this part-load range, compared to fully guided guide vanes, there are not inconsiderably lower losses. According to the sawtooth-shaped curves or surfaces of the projections 18 are formed such that there is a proportional dependence between the change in the angle of rotation of the adjusting ring 14 and the change in the setting angle of the guide vanes 6. It is also essential that the flow width is narrowed in the area of the projections 18 of the adjusting ring 14 and thus in the area of the trailing edges or the free ends of the guide vanes 6.

Fig. 3 shows purely schematically the diffuser for an exhaust gas turbine with an axially flow through stator, not shown here. Concentric to the rotor axis 12, the adjusting ring 14 can be seen, which is designed here as a hollow ring and which, according to the invention, is arranged radially on the outside in the flow channel. The guide vanes 6 can be pivoted about essentially radially oriented pivot axes 10, which are located at the front end or in the region of the leading edges. The free end or the trailing edge of the guide vane 6 lies against the end face of the adjusting ring 14 with a small, radially outer part. The adjusting ring 14 is guided in a suitable manner in the housing 22, and it can be adjusted parallel to the rotor axis 12, for example via a bolt 24.

FIG. 4 shows a part of the guide apparatus projected into the drawing plane in the viewing direction B according to FIG. Fig. 3. The housing 22 has an inclined slot 26 for the bolt 24, so that not only an axial adjustability in the direction of the rotor axis but also a rotation about the rotor axis for the adjusting ring 14 is given. According to the invention, this makes it easy to adjust the adjustment ring. The guide vanes 6, as can be readily recognized in connection with FIG. 3, rest with the outer part of their trailing edge on the adjusting ring 14, which thus forms the one end limit. By moving the adjusting ring 14 in the direction of the arrow 20, the end limitation is also changed in this embodiment. It is not necessary to emphasize that the other end limitation is given by the adjacent guide vane. As the boost pressure increases, the force component of the inflowing medium indicated by the arrow 28 becomes larger, as a result of which the guide vanes 6 are pressed firmly against the end limit specified by the adjusting ring 14. At a lower boost pressure, that is to say in the partial load range, the component mentioned goes to zero, and the guide vanes which can be freely pivoted between the end limits are automatically set to the most favorable angular position. There is a not insignificant reduction in gap and impact losses.

• 2 Laufrad
• 4 Einströmkanal
• 6 Leitschaufel
• 8 Gehäuse
• 10 Schwenkachse
• 11 Anströmkante
• 12 Rotorachse
• 14 Verstellring
• 16 freies Ende
• 18 Vorsprung
• 20 Pfeil
• 22 Gehäuse
• 24 Bolzen
• 26 Schlitz
• 28 Pfeil
• 30 Hebel

FIG. 5 shows a view similar to FIG. 4, but with the three guide vanes 6 shown being coupled to one another by means of a lever 30. Otherwise, the description of FIG. 4 applies accordingly. The three guide vanes 6 are coupled to one another by means of the lever 30 in such a way that they can be pivoted together about their pivot axes 10 and thus each assume the same angular position in the partial load range. Distributed over the circumference, the other guide vanes, not shown here, are of course also coupled to one another in groups. In contrast to embodiments with individually pivotable blades, which take up slightly different positioning angles due to the spiral flow, the guide blades coupled in this way each assume the same angular position. The uniformity of the inflow to the turbine wheel is significantly improved and vibrations of individual blades can be prevented. Reference symbol list

• 2 impeller
• 4 inflow channel
• 6 guide vane
• 8 housing
• 10 swivel axis
• 11 leading edge
• 12 rotor axis
• 14 adjusting ring
• 16 free end
• 18 head start
• 20 arrow
• 22 housing
• 24 bolts
• 26 slot
• 28 arrow
• 30 levers

Claims (6)

1. An adjustable distributor of an exhaust gas turbine, in particular of a turbo charger with a ring of guide vanes which are arranged concentrically round a rotor axis and are each pivotal between two end limits about pivot axes arranged in the front region of the guide vanes connected to the inlet edges, the end limits being adjustable by means of an adjusting ring, characterised in that the adjusting ring (14) has contact faces for the guide vanes (6), which contact faces form an end limit for the respective guide vane (6), in that the guide vanes (6) are freely pivotal in the angular range adjustable by means of the adjusting ring under the flow forces, and in that the adjusting ring (14) is arranged inside the flow duct and/or forms part of the flow duct wall.

2. An adjustable distributor according to claim 1 for a centripetally traversed wheel, characterised in that the adjusting ring (14) has, on projections (18) directed toward the flow duct, the saw-tooth-shaped contact faces for the free ends (16) of the guide vanes (6).

3. An adjustable distributor according to claim 1, characterised in that the contact faces of the adjusting ring (14) are arranged in guide grooves in which the guide vanes (6) each engage with a lateral pin.

4. An adjustable distributor according to claim 1, characterised in that the contact faces of the adjusting ring (14) are each arranged on a guide pin which engages in each case into a guide groove provided on the end face of the guide vane (6) or on which the guide vane (6) rests with the downstream profile side.

5. An adjustable distributor according to claim 1 for an axially traversed wheel, characterised in that the contact face is arranged on an axial end face of the adjusting ring (14) designed as a hollow ring, on which end face the free ends of the guide vanes (6) rest in part.

6. An adjustable distributor according to one of claims 1 to 5, characterised in that at least two of the guide vanes (6) are coupled together, in particular by means of a lever (30), and are freely pivotal together.

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