DE10061847A1 - Exhaust gas supercharger has compressor wheel which has separate attachment rotor with blades having trailing edge angle greater than leading edge angle - Google Patents

Abstract

The exhaust gas supercharger has an exhaust gas turbine (3) in the exhaust manifold (5) and a compressor in the induction manifold (7). The compressor wheel (9) has a separate attachment rotor (10). The blades of this rotor have a trailing edge angle which is greater than the leading edge angle. The compressor wheel does not rotate relative to the exhaust gas turbine.

Description

The invention relates to an exhaust gas turbocharger for a Internal combustion engine and a method for operating an exhaust gas 7. turbocharger according to the preamble of claim 1 or 7.

In US 6 029 452 an exhaust gas turbocharger is included an exhaust gas turbine in the exhaust line of an internal combustion engine and discloses a compressor in the intake tract, the compressor is driven by the exhaust gas turbine via a shaft. To the Un Support of the compressor, especially at low speeds len, where there is only a low pressure level in the exhaust system prevails with only comparatively little turbine power can be generated that can be transferred to the compressor, an electric motor is provided between the compressor and Turbine arranged on the shaft and rotatably with the shaft connected is. When the electric motor is energized, the Shaft and thus also the compressor with additional drive power supplied, which is independent of that in the exhaust system pressure level an increased boost pressure in the intake system can be built up of the engine to increase the engine power is supplied.

This exhaust gas turbocharger enables an increase in the La power by switching on the electric motor. However, since the Rotor of the electric motor is rotatably connected to the shaft, the mass to be accelerated is significantly increased, whereby  especially in the transient area due to the increased Mass moment of inertia with a delay in speed build-up and accordingly with a delayed boost pressure build-up must be expected. The high moment of inertia requires also a comparatively large electromo gate with high power consumption.

Beyond an additional boost pressure build-up can No other functions can be performed via the electric motor. In particular, it is not possible to change the behavior of the compaction ters in limit areas when operating near the surge limit o the positive influence close to the darning limit.

The invention is based on the problem, the operating behavior for an exhaust gas turbocharger for an internal combustion engine improve. In particular, it should build up the boost pressure in the low ren speed range can be improved. Beyond that expedient the area of application of the exhaust gas turbocharger both in Direction of large volume flows to be promoted as well as in Rich small volume flows to be promoted.

This problem is solved according to the invention with the features of the Proverbs 1 and 7 solved. The subclaims give useful Training courses.

The exhaust gas turbocharger according to the invention has a compressor a compressor wheel and an additional one, separate from the ver Dichterrad trained front rotor, which is coaxial to Compressor wheel is arranged and in the direction of flow sucked combustion air seen upstream of the compressor the located. With the help of the front runner, the operation behave of the compressor in a targeted, desired manner be influenced. It is particularly possible depending a standard compressor wheel for the desired application  to equip an additional front runner that ver shifting the surge limit in the direction of smaller volume flows o which, however, shifts the compression limit of the compressor into Direction of larger volume flows or a combination of allowed that. The front runner as additional equipment for ver dichterrad represents a simple, inexpensive and quick Action to be taken to improve operating behavior of the compressor.

It is also provided that the front rotor blades of the Front rotor and the compressor wheel blades of the compressor rotor which are aligned at a certain angle to each other. To determine the angular position between the blades of the front block rotor and the blades of the compressor wheel are before partial absolute angle, which the respective Blade alignment at a specific position of the header rotor and the compressor wheel in relation to the plane of rotation of Determine the attachment impeller or compressor wheel. For that be the exit angle of the front rotor blades and the on step angle of the compressor wheel blades used, the Exit angle of the front rotor blades is larger than that Entry angle of the compressor wheel blades, each based on the level of rotation of the front rotor or the compressor wheel. There the exit angle of the front rotor blades is greater than the entry angle of the compressor impeller blades, the pump limit in the compressor map in favor of smaller volume or Mass flows shifted. In addition, in particular already at low supercharger speeds with an increased mass flow rate an accompanying boost pressure buildup can be achieved.

A positive influence on the boost pressure build-up is in particular by an additional drive for the front-mounted rotor enough, which is advantageously carried out by means of an electric motor bar, in that, for example, the front rotor rotates the rotor or  forms part of the rotor of the electric motor. More legs Flow possibilities are achieved by the fact that the block rotor is rotatably mounted independently of the compressor wheel, so that front rotor and compressor wheel with different Rotate speeds. In this way, through a appropriate rotation of the front rotor Such aerodynamic effects can be exploited by depending on the current area of application, a swirl or a counter-swirl due to a higher or lower speed of the front rotor against the compressor wheel speed or by reversing the Direction of rotation is set.

According to an advantageous further development, the exit twine lies angle of the front rotor blades, which is defined as Win angle of the tangent to the front rotor blades in the area of the side of the front rotor facing the compressor wheel, in egg NEM angular range between 75 ° and 100 °, especially at about 85 °. The entry angle of the compressor wheel blades - defined as the angle of the tangent to the compressor wheel blades on the the side facing the front runner - is smaller than the end step angle of the front rotor blades and is preferably in an angular range between 30 ° and 45 °. With such a Ratio of exit angle of the front rotor blades to Entry angle of the compressor wheel blades is particularly in the transient transition range at low engine speeds Internal combustion engine that has only a low exhaust gas pressure level The result is a faster boost pressure build-up with an additional Chen drive the front rotor achieved. In addition, a pump boundary shift in favor of smaller mass flows in the case a reduced front rotor speed reached, in particular the one at a speed below the compressor wheel speed set runner speed.

In the method according to the invention, which preferably on the  Exhaust gas turbocharger according to the invention is used, a Incorrect flow on the compressor wheel set in ei The angular range is between -5 ° and + 30 °. The Falschan flow, which is defined as the angle between the ge Velocity vector of the gas flow on the compressor wheel and the tangent to the compressor wheel blades on the header side facing the rotor, with a positive false flow a back impact on the compressor wheel and a negative one Incorrect inflow means an abdominal impact on the compressor wheel can, through a coordinated speed behavior of intent rotor and compressor wheel can be influenced. Is preferred for Boost pressure increase in the low speed range a positive Incorrect flow, which pushes the compressor wheel backwards has set, by the speed of the intent accelerated to a higher value than the compression terdrehzahl.

Further advantages and practical designs are the others Entities, the description of the figures and the drawings ent to take. Show it

Fig. 1 is a schematic representation of a turbocharged internal combustion engine having a compressor wheel, a compressor and an upstream inducer,

Fig. 2 of the compressor in a sectional view,

Fig. 3 is an enlarged view of terrad inducer and compaction,

Fig. 4 is a vector diagram with flow vectors at NEN Various positions of the compressor,

Fig. 5 is a design diagram with the course of the Schaufelwin keldiffer from exit angle of the front rotor blades and inlet angle of the compressor wheel blades depending on the peripheral speed difference between the front rotor and compressor wheel, based on an average flow velocity vector.

In the following figures, the same components with the same loading provide traction marks.

The internal combustion engine 1 shown in Fig. 1 is an exhaust gas, and associated with turbocharger 2 with an exhaust gas turbine 3, which is equipped with a varia bel adjustable turbine geometry 4 with a compressor 6 driven by a shaft 8 from the exhaust gas turbine 3. The exhaust gas turbine 3 is arranged in the gas line 5 of the internal combustion engine and is driven by the exhaust gases under pressure. The turbine output of the exhaust gas turbine 3 is converted via the shaft 8 into a corresponding compressor output of the compressor 6 , as a result of which combustion air sucked in by the compressor 6 is compressed to an increased charging pressure, with which charge air is supplied to the internal combustion engine 1 via the intake tract 7 .

The compressor 6 is constructed in two parts and comprises a Ver up terrad 9 and a compressor wheel 9 upstream, ko axially arranged inducer 10, which is driven by an electric motor. 11 The compressor wheel 9 and the front runner 10 can expediently rotate independently of one another. Before block runner 10 is seen in the flow direction of the intake combustion air upstream of the compressor wheel 9 , so that the combustion air sucked in with atmospheric pressure must first pass through the front runner 10 and then the compressor wheel 9 and is conducted downstream of the compressor wheel into the intake tract 7 . After compression in the compressor 6 , the charge air is first cooled in a charge air cooler 12 , which is arranged downstream of the compressor 6 in the intake tract 7 , and then fed to the internal combustion engine 1 .

The internal combustion engine 1 is also equipped with an exhaust gas recirculation device 13 via which an adjustable exhaust gas mass flow from the exhaust gas line 5 upstream of the exhaust gas turbine 3 can be guided into the intake tract 7 downstream of the charge air cooler 12 . The exhaust gas recirculation 13 comprises an exhaust gas recirculation line 14 with an adjustable valve 15 and an exhaust gas recirculation cooler 16 .

Via a regulating and control unit 17 , the function of the adjustable components of the internal combustion engine can be set as a function of the current status and operating parameters of the internal combustion engine and the associated units. Via the regulating and control unit 17 , in particular the variable turbine geometry 4 of the exhaust gas turbine 3 , the propeller rotor 10 driving the electric motor 11 and the valve 15 of the exhaust gas recirculation 13 are set.

The electric motor 11 is supplied via a power line 19 with current from a generator 18 which is driven by the internal combustion engine 1 .

Fig. 2 shows a compressor 6 with a compressor wheel 9 , be standing from a compressor wheel hub 20 and compressor wheel fel 21 , and a coaxial to the compressor wheel 9 arranged upstream of the compressor wheel placed rotor 10 , be standing from a front rotor hub 22 and front rotor blades 23 . The attachment rotor hub 22 is connected in a rotationally fixed manner to the rotor of the electric motor 11 . Compressor wheel 9 and Vorsatzläu fer 10 are mechanically decoupled and can circulate independently of each other. The front-end rotor 10 can be embossed by a corresponding action on the electric motor 11, a speed which differs from the compressor wheel speed. It can in particular in low engine speed ranges in which only a low exhaust back pressure is available to drive the supercharger and accordingly only a comparatively low boost pressure can be built up, the front rotor 10 revolve at a significantly higher speed than the compressor wheel 9 , thereby Combustion air drawn in in the direction of arrow 24 is compressed by the auxiliary rotor 10 to an increased boost pressure and / or by the rotation of the auxiliary rotor 10, a swirl to be transmitted to the compressor wheel aerody namically generated, which accelerates the compressor wheel to an increased speed.

It may optionally be advantageous to between inducer 10 and provide a mechanical coupling of the compressor wheel 9, may be that formed in particular as a switchable clutch in order to create, if necessary, a torsionally rigid connection between the front of block runner and the compressor wheel, which are also enabled again particularly at higher rotational speeds of the compressor wheel can.

The enlarged representation of the compressor wheel 9 and the attachment rotor 10 according to FIG. 3 shows that the exit angle β _{V, A of} the attachment rotor blades 23 has a larger value than the entry angle β _{R, E of} the compressor wheel blades 21 . The exit angle β _{V, A of} the front rotor blades 23 is defined here as the angle of the tangent to the front rotor blades 23 on the side facing the compressor wheel 9 - marked with "A" - relative to the plane of rotation of the front rotor 10 . The entry angle β _{R, E} is correspondingly defined as the angle of the tangent to the compressor wheel blades 21 on the side “E” facing the front rotor relative to the plane of rotation of the compressor wheel 9 . The exit angle β _{V, A} is the inducer blades 23 exceeds the angle of entry β _{R, E} of the compressor wheel 21, wherein suitably the exit angle β _{V, A} in a range of values between 75 ° and 100 °, in particular sondere at about 85 °, and the Verdichterradschaufel- Entry angle β _{R, E is} in a range of values between 30 ° and 45 °, for example around 35 °. It can be advantageous to make the exit angle β _{V, A} twice as large as the entry angle β _{R, E.}

As the vector diagram of FIG. 4 in conjunction with the Dar position of FIG. Refer 3, is produced as a function of the exit angle β _{V, A} is the inducer blades 23, enters angle β _{R, E} of the compressor wheel 21, the Umfangsge speed U _V of intent rotor 10, the peripheral speed U _R of the compressor wheel 9 and a pointing in the flow direction 24 vector c _m, with which the average flow speed of the compressor wheel is referred 9 passing combustion air, a Falschanströmung i on the Ver up terrad 9, which is defined as Angle between the actual speed vector w _{R, E of} the gas flow hitting the compression wheel and the tangent 25 to the compressor wheel blades 21 on the side facing the front rotor 10 of the compressor wheel, the tangent 25 defining the entry angle β _{R, E of} the compressor wheel blades 21 , The actual speed vector w _{R, E of} the gas flow impinging on the compressor wheel is composed vectorially of the peripheral speed u _{R of} the compressor wheel and a vector c _{R, E of} the absolute speed of the gas flow, which runs parallel to and has the same length as Vector c _{V, A of} the absolute speed at the outlet of the front runner 10 (shown in dashed lines), which in turn can be determined vectorially from the peripheral speed u _{V of} the front runner 10 and an actual speed vector w _{V, A} in the region of the exit "A" from the front runner 10 , The Ge speed vector w _{V, A} with respect to the plane of rotation of the front rotor includes the geometrically defined exit angle β _{V, A.} The actual speed vector w _{V, A} and the vector of the absolute speed c _{V, A} both have a component in the direction of flow 24 which corresponds to the mean flow rate c _m . The vector of the actual speed w _{R, E} at the inlet "E" of the compressor wheel 9 includes the angle β _{R, E} with respect to the plane of rotation of the compressor wheel.

The false flow i is preferably in an angular range from -5 ° to + 30 °, a positive value of the wrong flow i - as shown in FIG. 4 - a back impact on the rear side of the compressor wheel blades 21 and a negative value of i a abdominal impact the front of the compressor wheel show feln 21 results.

Fig. 5 shows a design diagram with a range of the blade angle difference β _{V, A} - β _{R, E} between two boundary lines, which mark a false flow i = -5 ° and i = + 30 °, depending on the difference in the peripheral speeds u _V - u _R related to the average velocity c _{m of} the gas flow. The two curves for the incorrect inflow i = -5 ° (abdominal joint) and i = 30 ° (back joint) limit an intermediate preferred area for the operation of the compressor and characterize both a preferred blade difference from the exit angle β _{V, A of} the front rotor blades and Entry angle β _{R, E of} the compressor wheel blades as well as a preferred circumferential speed difference between the peripheral speed u _{V of} the front rotor and the peripheral speed u _{R of} the compression wheel. Areas in which the wrong inflow is less than i = -5 ° should be avoided, since there is a risk of pumping in the compressor outside of the marked area. On the other hand, it can be advantageous in the transient area of the compressor, especially at low engine speeds, to set the incorrect inflow in the direction of the limit line i = 30 ° or, if necessary, to an even greater value, since in this area there is a strong swirl between the front rotor and the compressor wheel there is what can be used to increase the speed of the compressor wheel and thus to increase the boost pressure.

In Fig. 5 a preferred design for the front rotor blades an exit angle β _{V, A} = 85 ° is entered, the se angle selection of the outlet angle of the front rotor blades supports a rapid run-up of the supercharger rotor, particularly in the case of a motor-driven front rotor. On the other hand, a counter-swirl can be generated with the auxiliary rotor at a standstill at an exit angle β _{V, A} = 85 °, which can have a blocking effect in the compressor inlet, whereby the pressure range of the charge air to be set downstream of the compressor can be increased, in particular in the direction of smaller pressure values. The locking effect can be increased by turning the front rotor in opposite directions to the compressor wheel.

The preferred design range limited by the incorrect flows i = -5 ° and i = 30 ° is at a difference angle β _{V, A} - β _{R, E} = 0 (outlet angle β _{V, A} identical to the inlet angle β _{R, E} ) a larger part in the area of the positive abscissa. With increasing difference angle, the design range shifts in the direction of the negative abscissa and at the same time rises sharply. As the difference angle decreases, the slope of the design range also decreases.

Claims (8)

1. Exhaust gas turbocharger for an internal combustion engine, with an exhaust gas turbine ( 3 ) arranged in the exhaust line ( 5 ) of the internal combustion engine ( 1 ) and a compressor ( 6 ) arranged in the intake tract ( 7 ), in the inflow region of which a compressor wheel ( 9 ), the compressor wheel blades ( 21 ), is arranged, the compressor wheel ( 9 ) being connected to the exhaust gas turbine ( 3 ) in a rotationally fixed manner, characterized in that
that the compressor wheel (9), a separately formed, arranged coaxially inducer is upstream (10) with auxiliary rotor blades (23), and that the exit angle (β _{V, A)} of the pre set rotor blades (23) is greater than the entry angle (β _{R, E} ) of the compressor wheel blades ( 21 ), wherein
the exit angle (β _{V, A} ) of the attachment rotor blades ( 23 ) as the angle of the tangent to the attachment rotor blades ( 23 ) on the side facing the compressor wheel ( 9 ) relative to the plane of rotation of the attachment rotor ( 10 ) and
the entry angle (β _{R, E} ) of the compressor wheel blades ( 21 ) as the angle of the tangent to the compressor wheel blades ( 21 ) on the side facing the front rotor ( 10 ) relative to the plane of rotation of the compressor wheel ( 9 )
is defined. 2. Exhaust gas turbocharger according to claim 1, characterized in that the front rotor blade exit angle (β _{V, A} ) is in an angular range between 75 ° and 100 °. 3. Exhaust gas turbocharger according to claim 2, characterized in that the front rotor blade exit angle (β _{V, A} ) is 85 ° be. 4. Exhaust gas turbocharger according to one of claims 1 to 3, characterized in that the compressor wheel blade entry angle (β _{R, E} ) is in an angular range between 30 ° and 45 °. 5. Exhaust gas turbocharger according to one of claims 1 to 4, characterized in that the rotational movement of the front rotor ( 10 ) is adjustable independently of the rotational movement of the compressor wheel ( 9 ). 6. Exhaust gas turbocharger according to one of claims 1 to 5, characterized in that the front rotor ( 10 ) can be driven by an electric motor ( 11 ). 7. A method for operating an exhaust gas turbocharger for an internal combustion engine, in particular an exhaust gas turbocharger according to one of claims 1 to 6, in which an exhaust gas turbine ( 3 ) arranged in the exhaust line ( 5 ) of the internal combustion engine ( 1 ) has a compressor wheel ( 9 ) with compressor wheel blades ( 21 ) drives a compressor ( 6 ) arranged in the intake tract ( 7 ), characterized in that a coaxially arranged auxiliary rotor ( 10 ) upstream of the compressor wheel ( 9 ) and separately formed is driven in such a way that an incorrect inflow (i) on the compressor wheel ( 9 ) is in an angular range between -5 ° and 30 °, the false flow (i) being defined as the angle between the speed vector (w _{R, E} ) of the air flow on the compressor wheel ( 9 ) and the tangent shovel the compressor wheel ( 21 ) on the side facing the front rotor ( 10 ), whereby a positive false flow (i) causes a back impact on the compressor wheel ( 9 ) and a negative false inflow (i) results in an abdominal impact on the compressor wheel ( 9 ). 8. The method according to claim 7, characterized in that to increase the boost pressure in the low speed range for setting a positive false flow (i) the front-runner ( 10 ) is accelerated to a speed that is higher than the compressor wheel speed.