DE102017007636A1 - Halbaxialturbine for an exhaust gas turbocharger - Google Patents

Abstract

The invention relates to a half - axial turbine (10) for an exhaust gas turbocharger, comprising a turbine housing (12) with a turbine wheel (20) and at least partially disposed in the turbine housing (12) and rotatable about an axis of rotation (14) relative to the turbine housing (12) with at least two, by the turbine housing (12) formed, at least partially separated and asymmetrically trained and by exhaust gas of an internal combustion engine through-flowable floods (30, 40), by means of which the floods (30, 40) flowing through the exhaust gas turbine wheel (20) can be fed. A first flow (30) of the at least two floods (30, 40) has at least one feed region (16) at which the exhaust gas flowing through the flows (30, 40) reaches the turbine wheel (20) by means of the first flow (30) Vane tip inlet region (22) of the turbine wheel (20) can be supplied, a smaller flow cross section (32) as a second flood (40) of the at least two floods (30, 40), by means of which the exhaust gas to the turbine wheel (20) at a Schaufelfußeintrittsbereich ( 24) of the turbine wheel (20) can be fed.

Description

The invention relates to a Halbaxialturbine for an exhaust gas turbocharger according to the preamble of claim 1.

Exhaust gas turbocharger systems known from the prior art (charging systems) in a two-stage configuration usually use commercially available or existing components from single-stage systems. As a result, while the cost of building such systems can be kept low, but at the same time these components are not optimally adapted to given operating conditions in two-stage operation. In particular, pressure ratios of turbines and compressors in two-stage operation are significantly lower than in comparable single-stage turbochargers.

From the DE 10 2015 016 591 A1 is a double-flow, asymmetric turbine in a semi-axial design known. Here, a turbine wheel by means of two floods exhaust along a respective, obliquely to an axial direction and obliquely to a radial direction of the turbine wheel extending feed direction can be fed. The turbine wheel has a mean blade entry angle between 70 ° and 140 °.

The DE 100 48 237 A1 describes an exhaust gas turbocharger with a, equipped with variable turbine geometry exhaust gas turbine and a compressor, wherein the exhaust gas turbine is formed with two separate flow two inlet channels each having a flow inlet cross section to the turbine wheel and the two inflow channels are pressure-tight shielded from each other. A flow inlet cross section of an inflow channel to the turbine wheel is variably adjustable via the variable turbine geometry. The inflow channel has its own inflow connection for the separate supply of exhaust gas.

Object of the present invention is to provide a Halbaxialturbine of the type mentioned, by which an improved turbine efficiency can be achieved.

This object is achieved by a Halbaxialturbine with the features of claim 1. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the remaining claims.

The invention relates to a Halbaxialturbine for an exhaust gas turbocharger, with a turbine housing, with an at least partially disposed in the turbine housing and rotatable about a rotational axis relative to the turbine housing turbine wheel and with at least two, formed by the turbine housing, at least partially separated and asymmetrical to each other trained as well as by exhaust gas of an internal combustion engine through-flowable floods, by means of which the exhaust gas flowing through the floods can be fed to the turbine wheel.

The Halbaxialturbine is characterized in that the exhaust gas flowing through the floods flows out of the floods during operation of the turbine along a respective, obliquely to the axial direction of the turbine wheel and obliquely to the radial direction of the turbine wheel feed direction and the turbine wheel flows along the respective feed direction. The exhaust gas is supplied to the turbine wheel not strictly in the radial direction or strictly in the axial direction. Instead, the exhaust gas by means of both floods obliquely to the axial direction and obliquely to the radial direction, that is fed semi-axially (from the semi-axial direction) to the turbine wheel.

In order to further develop a half-axial turbine such that an improved turbine efficiency can be achieved, it is provided according to the invention that a first flow of the at least two flows at at least one feed region at which the exhaust gas flowing through the flows reaches the turbine wheel via the first flow at a blade tip inlet region of the turbine wheel can be supplied has a smaller flow cross-section, as a second flood of the at least two floods, by means of which the exhaust gas is supplied to the turbine wheel at a blade root inlet region of the turbine wheel. In other words, the first flood has a first flow cross-section, which is smaller than a second flow cross-section of the second flood. As a result of the smaller flow cross section, the exhaust gas at the blade tip inlet region (and thus at the respective blade tips of the blades) can be supplied to the respective blades of the turbine wheel at a greater inflow velocity than at the blade root inlet region (and thus at the respective blade roots of the blades).

Due to the different flow cross sections of the respective floods, the half-axial turbine is designed overall as a double-flow, asymmetrical turbine in a semi-axial design.

The blade tip inlet region corresponds to the inlet region of the exhaust gas at respective blade edges of respective blades of the turbine wheel at the blade tip of the respective blades. The blade root entry region corresponds to the inlet region of the exhaust gas at the respective blade edges of the turbine wheel at the blade root of the respective blades.

The invention is based on the finding that during operation of the Halbaxialturbine a peripheral speed at the blade root (blade root peripheral speed) is smaller than a peripheral speed at the blade tip (blade tip peripheral speed). An improved turbine efficiency results from the fact that also a peripheral component of an inflow rate of the exhaust gas at the blade tip is greater than at the blade root in order to introduce a respective relative flow of the exhaust gas in a blade-congruent manner at the feed region into the turbine wheel. This is made possible by the fact that the first flow has the smaller flow cross section than the second flow and, accordingly, the exhaust gas introduced into the turbine wheel via the first flow at the blade tip inlet region has a higher inflow velocity than that via the second flow at the blade root inlet region into the turbine wheel introduced exhaust.

In an advantageous development of the invention, the turbine housing has a dividing wall which separates the at least two floods at the feed region such that the dividing wall flows exhaust gas from the first flood to the blade root inlet region and a flow of exhaust gas from the second flood to the Vane tip entry area prevents. This is advantageous because by means of the partition thus a particularly targeted alignment of the exhaust gas is made possible when it enters the turbine wheel at the feed.

In a further advantageous development of the invention, the at least two floods are oriented at the feed region at least substantially parallel to one another.

This is advantageous because it allows a particularly streamlined introduction of the exhaust gas into the turbine wheel at the feed area.

The term "substantially parallel" is understood to mean that respective central axes of the two floods at the feed region enclose an acute angle with one another, which is preferably less than 10 ° and particularly preferably less than 5 °.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing (s). The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

• 1 einen Querschnitt durch einen aus dem Stand der Technik bekannten Abgasturbolader, wobei ein turbinenseitiger Gehäuseabschnitt des Abgasturboladers zwei asymmetrisch zueinander ausgebildete Fluten aufweist;
• 2 eine schematische Schnittdarstellung einer für die Erfindung beispielhaften Ausführungsform einer Halbaxialturbine, welche ein Turbinenrad aufweist;
• 3 eine schematische Darstellung eines einem Schaufelfußeintrittsbereich des Turbinenrades zugeordneten Geschwindigkeitsdreiecks; und
• 4 eine schematische Darstellung eines einem Schaufelspitzeneintrittsbereich des Turbinenrads zugeordneten Geschwindigkeitsdreiecks.

Showing:

• 1 a cross-section through an exhaust gas turbocharger known from the prior art, wherein a turbine-side housing portion of the exhaust gas turbocharger has two asymmetrically formed floods;
• 2 a schematic sectional view of an exemplary embodiment of the invention for a Halbaxialturbine having a turbine wheel;
• 3 a schematic representation of a blade root entry region of the turbine wheel associated speed triangle; and
• 4 a schematic representation of a blade tip inlet region of the turbine wheel associated speed triangle.

In the figures, identical and functionally identical elements are provided with the same reference numerals.

1 shows a cross section through a known from the prior art exhaust gas turbocharger for an internal combustion engine, wherein at a turbine-side housing portion of the turbocharger, a turbine wheel 90 is rotatably mounted and two asymmetrical to each other formed floods 92 . 94 are provided. The flood 92 is designed as a so-called λ-flood, whereas the tide 94 is designed as an EGR flood. An inflow direction 96 from exhaust gas of the internal combustion engine to the turbine and thus to the turbine wheel 90 is represented by an arrow. Furthermore, in 1 a line 98 to an exhaust gas recirculation of the internal combustion engine and a line 100 to respective cylinders of the internal combustion engine clarifies. The wires 98 . 100 are with the respective floods 92 . 94 fluidly connected.

2 shows a schematic sectional view of an exemplary embodiment of the invention for a Halbaxialturbine 10 for an exhaust gas turbocharger.

The half-axial turbine 10 includes an in 2 partial illustrated turbine housing 12 , at least partially in the turbine housing 12 arranged and at least one rolling bearing 50 around a rotation axis 14 relative to the turbine housing 12 rotatable turbine wheel 20 ,

The half-axial turbine 10 further includes two, through the turbine housing 12 formed, at least partially separated and asymmetrically trained to each other and exhaust gas from an internal combustion engine can flow through flooding 30 . 40 by means of which the floods 30 . 40 exhaust gas flowing through the turbine wheel 20 can be fed.

A first flood 30 the two floods 30 . 40 points at a feed area 16 on which the floods 30 . 40 exhaust gas flowing through the turbine wheel 20 by means of the first flood 30 at a blade tip entry area 22 of the turbine wheel 20 can be supplied, a smaller first flow cross-section 32 has, as a second flood 40 the at least two floods 30 . 40 , by means of which the exhaust gas is the turbine wheel 20 at a blade root entry area 24 of the turbine wheel 20 can be fed. The second flood 40 has a second flow cross section 42 on. In other words, the in 2 indicated by dashed lines, first flow cross-section 32 smaller than the one in 2 also indicated by dashed lines, second flow cross-section 42 ,

The blade tip entry area 22 represents an area at which the exhaust gas to respective blade tips 26 of the turbine wheel 20 meets, whereas the blade root entry area 24 represents an area at which the exhaust gas on respective blade roots of the turbine wheel 20 meets as soon as the exhaust gas over the respective floods 30 . 40 through the feed area 16 occurs.

The turbine housing 12 has a partition 18 on which the two floods 30 . 40 at the feed area 16 so separated from each other that the partition 18 a flow of exhaust gas from the first tide 30 to the blade root entry area 24 and a flow of exhaust gas from the second flood 40 to the blade tip entry area 22 in derogation.

The two floods 30 . 40 are at the feed area 16 are oriented at least substantially parallel to each other. To make this possible, the partition runs 18 at an acute angle in the direction of the feed area 16 to.

Due to the asymmetrically designed floods 30 . 40 is a good charge change in an internal combustion engine with simultaneously functioning high-pressure exhaust gas recirculation possible.

Through the Halbaxialturbine 10 may be a particularly favorable blade inflow of the respective blades of the turbine wheel 20 be achieved with exhaust. Compared to known from the prior art turbine systems, which have different flow conditions of floods, on the floods 30 . 40 a Fehlanströmung the respective blades of the turbine wheel 20 avoided or at least significantly reduced.

In radial turbines with two exhaust gas flows known from the prior art, respective peripheral speeds at the turbine wheel inlet are constant over the blade height of the respective radial turbine blades. If the inflow velocity (circumferential component) of both exhaust gas flows is not the same, then deviations of the circumferential component in the inflow to the circumferential speed of the turbine wheel inlet occur.

The half-axial turbine 10 offers advantages in design to lower pressure ratios compared to known from the prior art radial turbines. Therefore, the semi-axial turbine 10 especially useful for use in two-stage supercharging systems. Due to the special arrangement of the floods 30 . 40 , So by the fact that the exhaust gas by means of the first flood 30 specifically to the blade tip entry area 22 and about the second flood 40 specifically to the blade root entry area 24 of the turbine wheel 20 can be supplied, results in a particularly favorable flow of the turbine wheel 20 , which also as impeller of the Halbaxialturbine 10 can be designated. As a result, compared to turbine systems known from the prior art, an improved turbine efficiency can be achieved.

Respective peripheral speeds on the blade root 28 as well as at the blade tip 26 are in the operation of the Halbaxialturbine 10 differently. The peripheral speed at the blade root 28 can also be used as blade root circumferential speeds u _root be designated, which in one, in 3 shown, on the blade foot 28 applied speed triangle is plotted. More pages of the speed triangle in 3 are by a blade root relative velocity component w _{1, root} and by a blade root inflow rate c _{1, root} given. By the inflow of the Exhaust gas at the feed area 16 under the blade root inflow rate c _{1, root} (Hypotenuse of the speed triangle in 3 ) result in the blade root relative velocity component w _{1, root} and the blade root peripheral speeds u _root (as respective catheters) on the blade root 28 ,

4 indicates, on the blade tip 26 related speed triangle, wherein the peripheral speeds at the blade tip 26 as the blade tip peripheral speed u _tip is specified. More pages of the speed triangle in 4 are by a blade tip relative velocity component w _{1, tip} as well as a blade tip inflow rate c _{1, tip} given. By the inflow of the exhaust gas at the feed area 16 under the blade tip inflow rate c _{1, tip} (Hypotenuse of the speed triangle in 4 ) results in the blade tip relative velocity component w _{1, tip} and the blade tip peripheral speed u _tip at the blade tip 26 ,

The peripheral speeds u _tip . u _root at the blade tip 26 or on the blade foot 28 are at the Halbaxialturbine 10 different, as from the synopsis of 3 and 4 is recognizable.

The following applies in principle: u _tip > u _root

$$u_{tip}=r_{tip}*\omega =r_{tip}*2\pi n$$

$$u_{root}=r_{root}*\omega =r_{root}*2\pi$$

In general, the following relationships apply: $$u=r*\omega =r*2\pi n$$

$$u_{tip}=r_{tip}*\omega =r_{tip}*2\pi n$$

$$u_{rOOt}=r_{rOOt}*\omega =r_{rOOt}*2\pi$$

In the above relationships, the rotational speed n and the angular velocity ω of the turbine wheel become 20 , the blade tip radius r _tip (Distance between blade tip 26 and rotation axis 14 ) and the blade root radius r _root (Distance between blade root 28 and rotation axis 14 ).

Because the peripheral speeds u _tip . u _root should also be the blade tip peripheral speed u _tip the inflow velocity c _{1, tip} at the blade tip 26 be larger than on the blade foot 28 to the relative flow corresponding to the blade tip relative velocity component w _{1, tip} blade congruent in the turbine wheel 20 initiate. For the Halbaxialturbine 10 (asymmetric turbine) with the different floods 30 . 40 (Single floods) this offers the advantage that the tighter tide 30 (with the first flow cross section 32 ) causes a higher inflow rate of the exhaust gas as compared to other tide 40 (with the second flow cross section 42 ). For this reason, the first (tighter) tide 30 at the blade tip 26 arranged.

An in 2 given angle α as well as a height H one, the turbine wheel 20 or the individual blades of the turbine wheel 20 assigned, enveloping blade geometry determine how much different the peripheral speeds u _tip . u _root at the entrance to the turbine wheel 20 , ie at the feed area 16 are. It follows: $$\begin{array}{l}{u}_{tip}=r_{rOOt}+H*\text{tan}\left(\alpha \right)\\ bzw,u_{tip}=u_{rOOt}*\frac{r_{rOOt}+H*\text{tan}\left(\alpha \right)}{r_{rOOt}}\end{array}$$

Depending on bevel (angle α ) and bucket height (height H ) can be the difference of their respective speeds u _tip . u _root be sensibly adjusted to the appropriate turbine wheel 20 to the appropriate inflow profile of the two floods 30 . 40 pretend.

From the synopsis of 3 and 4 it can be seen that the respective speed triangles of the blade root 28 and blade tip 26 are also formed differently, since the respective inflow rates c _{1, tip} . c _{1, root} as well as the respective peripheral speeds u _tip . u _root between the two floods 30 . 40 vary. Ideally, the relative flow of the individual blades of the turbine wheel 20 as congruent as possible to the blade direction in order to avoid or at least minimize efficiency losses due to false flow and vortex formation. Overall, the asymmetry of the two floods 30 . 40 , which can also be referred to as housing floods, are used profitably. What is a disadvantage in radial turbines, is advantageous for the Halbaxialturbine 10 ,

In 3 and 4 is a so-called angle of incidence, which in this case corresponds to a value of about 30 °, neglected, since this does not affect fundamental relationships.

The relative components w _{1, tip} . w _{1, root} (Blade tip relative velocity component w _{1, tip} and blade root relative velocity component w _{1, root} ) are in 3 for the blade foot 28 or in 4 for the blade tip 26 perpendicular to the blade inlet (feed area 16 ).

For a blade angle of 90 °, this results in an optimal inflow. Even for blade angles deviating from 90 °, optimum inflow can be achieved. In order to achieve the highest possible turbine efficiency, is a vote of the height H , the angle α as well as the correct dimensioning of the two flow cross sections 32 . 42 meaningful.

A reverse interpretation path is conceivable: the individual floods 30 . 40 may be designed in accordance with requirements for exhaust gas recirculation in the corresponding degree of asymmetry. Depending on this, the turbine wheel can be 20 to design that appropriate parameters for a good inflow can be achieved.

With increasing asymmetry between the respective floods 30 . 40 greater efficiency advantages can be achieved.

The invention is based on the general knowledge that the design of compressors as Halbaxialmaschinen generally lowers their maximum pressure ratio and offers the opportunity for efficiency-optimal operation within their maps compared to a conventional compressor design with radial outflow. The half-axial turbine 10 , which may also have a variable turbine geometry, with the asymmetric flows 30 . 40 allows adaptation to particularly good turbine efficiencies compared to radial turbines from single-stage systems lower pressure ratios.

In the Halbaxialturbine 10 the realization is used that an axial low-pressure turbine offers ideal installation conditions. A low-pressure turbocharger can be arranged directly in extension to a high-pressure turbocharger, with even respective, coaxial shaft arrangements being conceivable. Also, a slight angular misalignment or lateral offset of respective shafts of the low pressure turbocharger and high pressure turbocharger is possible by fitting a connector between the high pressure turbocharger and the low pressure turbocharger. Due to a small intermediate volume between the high-pressure turbocharger and the low-pressure turbocharger, a good, transient start-up behavior can be achieved. Due to small surfaces, particularly low heat losses are achieved. In addition, there is a weight advantage and a very compact arrangement in the narrow engine compartment. By direct connection of the axial low-pressure turbocharger after an outflow of the high-pressure turbine results in very low pressure losses. In addition - in contrast to radial turbines - can be dispensed with a flow deflection.

LIST OF REFERENCE NUMBERS

10

Halbaxialturbine

12

turbine housing

14

axis of rotation

16

feeding

18

partition wall

20

turbine

22

Blade tip inlet area

24

Schaufelfußeintrittsbereich

26

blade tip

28

blade

30

first tide

32

first flow cross section

40

second tide

42

second flow cross section

50

roller bearing

90

turbine

92

λ Flood

94

EGR flood

96

Inflow direction (to the turbine)

98

Line for exhaust gas recirculation

100

Line to respective cylinders

c _{1, tip}

Blade tip inflow velocity

c _{1, root}

A root inflow velocity

r _tip

Blade tip radius

r _root

Schaufelfußradius

u _tip

Blade tip peripheral speed

u _root

Blade tip speed

w _{1, tip}

Blade tip relative velocity component

w _{1, root}

A root relative velocity component

H

height

α

angle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102015016591 A1 [0003]
• DE 10048237 A1 [0004]

Claims (3)

A half-axial turbine (10) for an exhaust gas turbocharger, comprising a turbine housing (12) with a turbine wheel (20) arranged at least partially in the turbine housing (12) and rotatable about an axis of rotation (14) relative to the turbine housing (12) and having at least two, formed by the turbine housing (12), at least partially separated and asymmetrically trained and by exhaust gas of an internal combustion engine through-flowable floods (30, 40), by means of which the flutes (30, 40) flowing through the exhaust gas turbine (20) can be fed, characterized characterized in that a first flow (30) of the at least two floods (30, 40) at least at a feed region (16), at which the exhaust gas flowing through the flows (30, 40) to the turbine wheel (20) by means of the first flow (30). at a blade tip inlet region (22) of the turbine wheel (20), has a smaller flow cross section (32) than a second flood (40) of the at least two F (30, 40), by means of which the exhaust gas to the turbine wheel (20) at a blade root inlet region (24) of the turbine wheel (20) can be fed. Halbaxialturbine (10) after Claim 1 characterized in that the turbine housing (12) comprises a partition wall (18) which separates the at least two floods (30, 40) at the feed region (16) such that the partition wall (18) flows exhaust gas from the first one Flood (30) to the blade root inlet region (24) and a flow of exhaust gas from the second flood (40) to the blade tip inlet region (22) prevented. Halbaxialturbine (10) after Claim 2 , characterized in that the at least two floods (30, 40) are oriented at the feed region (16) at least substantially parallel to one another.

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