WO2006018189A1 - Exhaust turbocharger for an internal combustion engine - Google Patents

Abstract

Disclosed is an exhaust turbocharger for an internal combustion engine comprising a compressor in the intake manifold and a turbine in the exhaust manifold thereof, the compressor being connected to the turbine via a torsion-proof shaft. The true length of the leading edge of the turbine wheel and the inlet diameter of the turbine wheel as well as the true length of the leading edge of the turbine wheel and the height of the guide vanes are at a specific proportion relative to each other, respectively, while being provided with a minimum value that assures stiffness and rigidity of the turbine wheel.

Description

 Exhaust gas turbocharger for an internal combustion engine

The invention relates to an exhaust gas turbocharger for an internal combustion engine according to the preamble of claim 1.

From the generic document DE 102 12 032 Al an exhaust gas turbocharger with a guide grid is apparent. The guide grid comprises a plurality of guide vanes distributed over the circumference of the guide grid. The turbine blades of the turbine wheel are formed in such a way that the first natural frequency of each turbine blade depending on the number of guide vanes and the maximum supercharger speed follows an inequality and does not exceed a certain limit. This ensures that the first natural frequency of each turbine blade has a sufficient distance to the excitation frequency, which is calculated by multiplying the number of blades on the guide grid and the maximum supercharger speed in engine braking operation. This distance between natural frequency and excitation frequency ensures that at maximum engine braking power at which the thermodynamic load of the turbine wheel reaches a maximum, no additional vibration excitation of the turbine blades takes place. The risk of breakage is thus significantly reduced and thus increases the service life of the turbine wheel. The invention is based on the problem to provide an exhaust gas turbocharger with a guide grid or a free annular nozzle without guide grid and with a thin-bladed turbine wheel, which has a high rigidity and high strength.

This problem is solved according to the invention with the features of claim 1. The dependent claims contain expedient developments.

Basically, care is taken in the development of the exhaust gas turbocharger a first natural frequency of

Turbine wheel blading, the so-called fundamental tone to put on the maximum operating speed of the exhaust gas turbocharger in engine braking mode. If the operation of the exhaust gas turbocharger in resonance to this natural frequency, this can damage due to vibration fractures both in the exit region of the blade on a

Turbinenradaustrittskante as well as in the inlet region at a turbine wheel leading edge. To solve the problem, it is proposed to set a true length of the turbine wheel leading edge to the diameter of a turbine wheel inlet in a relationship to each other, wherein the ratio is greater than 0.25. Furthermore, the true length of the

Turbine wheel leading edge to a blade height of a vane of a guide grid or a nozzle height of a free annular nozzle in relation to each other, said ratio is greater than 2.0. With the help of these relationships it is ensured that at least the first natural frequency of the turbine wheel blading is exceeded at low maximum intensities at the maximum rotational speed of the exhaust gas turbocharger. Thereby are Thin-bladed turbine wheels can be used, which can be operated without damage under very high loads.

In a further embodiment according to claim 2, a ratio of a rear wall diameter of the turbine wheel to the turbine wheel inlet diameter is within a certain range, whereby a relative movement of the turbine blades is made possible with a vibration excitation of the turbine blades to each other. Furthermore, due to the not drawn up to Turbinenradeintritt rear wall of the turbine wheel an advantageous effect on the damping properties of the turbine wheel.

In a further embodiment according to claim 3, the turbine wheel diameter in an optimized engine turbocharger system is advantageously in a certain size ratio to the displacement of the internal combustion engine. With additional consideration of a free Strömungsguerschnitts, which is located in a transition from a spiral channel of the turbine to the turbine, results in a turbo braking factor, which at maximum braking power in engine braking operation of a multiplication of the free flow cross-section with the inlet diameter of the turbine wheel and division with the displacement calculated internal combustion engine, which is in particular less than 0.006, possibly even less than 0.003. With this optimized value of the turbo-braking factor, it is ensured that with maximum achievable engine braking power, the thermal load on the internal combustion engine and the exhaust-gas turbocharger is comparatively low. The high engine braking powers and associated thermal and mechanical loads occurring with these turbo-braking factors can be absorbed by the turbine wheel without damage. Further advantages and expedient embodiments of the invention can be taken from the claims, the description of the figures and the drawings. Showing:

1 is a schematic representation of a detail of a turbine wheel and a vane of an exhaust gas turbocharger according to the invention,

2 is a schematic plan view of the turbine wheel of the exhaust gas turbocharger according to the invention,

Fig. 3 shows a turbine wheel of the exhaust gas turbocharger according to the invention and

4 shows a twin-flow turbine of the exhaust gas turbocharger according to the invention.

In Fig. 1 is a schematic representation of a detail of a turbine wheel 1 of a turbine 14 shown in FIG. 4 of an exhaust gas turbocharger, not shown in an exhaust duct, not shown, of an internal combustion engine, not shown, which is for example a gasoline or a diesel engine, mapped ,

The turbine wheel 1 with a turbine wheel inlet diameter D _τ has a turbine hub 2. About a shaft, not shown, which forms a rotationally fixed connection with the turbine hub 2, the turbine wheel 1 is rotatably coupled with a compressor, not shown in a non-illustrated intake of the engine and is driven by the turbine 1. The compressor compresses sucked combustion air, which is supplied via not shown inlet ducts of the internal combustion engine. The turbine wheel 1 is delimited by a turbine housing 4.

Around the circumference of the turbine hub 2, turbine blades 3 projecting approximately radially from the turbine hub 2 are arranged at uniform intervals, with only one turbine blade 3 being illustrated by way of example in FIG.

The turbine hub 2 has at its larger diameter end a turbine rear wall 5 with a diameter D ₃ . A turbine wheel inlet edge 6 of the turbine blade 3 is located perpendicular to the turbine wheel rear wall 5 at a distance H from the diameter D _{8 of} the turbine wheel rear wall 5.

In the turbine housing 4 is upstream of

Turbinenradeintrittskante G of the turbine blade 3, a guide grid 7 with a blade height h _Le a guide vane, not shown, and a Leitgitteraustrittskante 8 arranged. The guide grid 7 is adjustable, so that via the guide grid 7, a free flow cross section A _τ , which is in a transition from a spiral channel 15 shown in FIG. 4 of the turbine 14 is located on the turbine 1 is adjustable. This free flow cross-section A _τ determines the velocity of a flow medium and thus an inlet velocity of the flow medium into the turbine wheel 1 and thus also the rate of occurrence on a turbine blade 3 of the turbine wheel 1. An arrow 9 represents the flow direction of the flow medium.

An analogous effect in the turbine 14 on the velocity of the flow medium can be achieved by means of a suitably arranged spiral channel 15 with a free annular nozzle, that is to say without a guide grid 7. FIG. 2 shows the schematic plan view of a turbine blade 3 of the turbine wheel 1 of the exhaust gas turbocharger according to the invention. In order to reduce a shock-like stress on the turbine blade 3, a tangent 10 of the turbine blade 3 encloses an angle with a plane of the turbine wheel rear wall 5, the so-called

Rake angle γ. This rake angle γ is advantageously less than 50 °. Along the tangent 10 of the turbine blade 3, a true length S _{ER of} the turbine wheel inlet edge 6 runs. The rotation of the turbine wheel 1 takes place in the direction of rotation 12.

According to the invention, the true length S _{ER of} the turbine wheel leading edge 6 has a value of at least one quarter of the turbine wheel diameter _Dτ and is at least twice as large as the blade height h _Le or, in the case of a free annular nozzle, the height of the free annular nozzle. The greater the ratio of the true length of the turbine wheel inlet edge S _ER to the blade height h _Le , the more a pressure peak of a flow of the flow medium is reduced to the turbine blade 3.

With the help of these relationships it is ensured that at least the first natural frequency of a

Turbine wheel blading is exceeded at a maximum speed of the exhaust gas turbocharger. Advantageously, thereby thin turbine blades 3 are used, which are operable damage-free under very high loads.

In order to enable a relative movement of the turbine blades 3 to each other at a vibration excitation of the turbine blades 3 due to a certain exhaust gas turbocharger speed is a ratio DD of the diameter D ₅ of Turbinenradrückwand 5 to the turbine wheel inlet diameter D _{τ to set} within a range of values, which has the value of 0.6 as the minimum ratio and the value 0, 95 as the maximum ratio.

In Fig. 3, the turbine wheel 1 of the exhaust gas turbocharger is shown to further illustrate the exhaust gas turbocharger according to the invention.

In Fig. 4, the turbine 14 is formed as a double-flow asymmetric turbine. As an alternative to the twin-flow asymmetric design of the turbine 14, the turbine may also be designed as a single-flow turbine or a symmetrical multi-flow turbine.

In order not to exceed the turbine load, in particular the thermal load, during engine braking operation using variable turbine geometry exhaust gas turbines, a sizing rule may be considered. This dimensioning rule supports the design of the free flow cross-section A _τ and the

Ingress diameter D _{τ of} the turbine wheel 1 as a function of a stroke volume of the internal combustion engine, which can be calculated as the sum of the difference volumes between the smallest and largest volumes of the combustion chambers of the internal combustion engine, in particular a reciprocating internal combustion engine. In accordance with this dimensioning rule, a braking braking factor TBF is determined according to the relationship during braking operation at maximum braking power of the internal combustion engine

D _τ

TBF = A _τ • - V _H determined, which is to achieve high braking performance while maintaining allowable load limits less than 0.006, in particular less than 0.003.

Claims

 claims Exhaust gas turbocharger for an internal combustion engine, with a compressor arranged in the intake tract of the internal combustion engine and a turbine (14) arranged in the exhaust tract of the internal combustion engine, which turbine blades (3) and a guide grid (7) with guide vanes with a blade height (h _Le ) or a free annular nozzle without Guide vanes with a nozzle height (h _Le ), wherein the turbine (14) has a turbine wheel inlet diameter (D _τ ) and a true length (S _ER ) of a turbine wheel leading edge (6), characterized in that the true length (S _ER ) of the turbine wheel leading edge (6) to the turbine wheel inlet diameter ( _Dτ ) of the turbine (14) a ratio SD according to the relationship g SD = - ⁵ ^ - and D _τ SD is larger than 0.25, and the true length (S _ER ) of the turbine wheel leading edge (6) having the blade height (h _Le ) of the guide rail of the guide rail (7) or the nozzle height (h _Le ) of the free ring nozzle is a ratio Sh according to the relationship g Sh = - ^ - has and Sh is greater than 2.0. Exhaust gas turbocharger for an internal combustion engine according to claim 1, characterized in that a diameter (D ₈ ) of the turbine rear wall (5) of the turbine wheel (1) with the turbine wheel inlet diameter (D _τ ) a ratio DD according to the relationship D _s DD = -s- D _τ forms and DD lies in the following value range: 0.6 <DD <0.95 Exhaust gas turbocharger for an internal combustion engine according to claim 1 or 2, characterized in that in braking mode at maximum braking power of Internal combustion engine, a free flow cross-section (A _τ ), which is located in a transition from a spiral channel (15) of the turbine (14) on the turbine wheel (1), the Turbine wheel inlet diameter (D _τ ) and a stroke volume (V ₁₁ ) of the internal combustion engine in the following relationship to each other and a turbo braking factor TBF according to the relationship TBF = A _τ • - ^ form, wherein the turbobar factor TBF is less than 0.006.