DE102014215888A1 - Internal combustion engine with variable mixed-flow turbine - Google Patents

Abstract

The invention relates to an internal combustion engine having an intake system for supplying charge air, an exhaust gas removal system (2) for discharging the exhaust gas and at least one mixed-flow turbine (1) arranged in the exhaust gas removal system (2) and having at least one turbine housing (3) and on a rotatable turbine shaft (4) mounted impeller (5) and wherein the turbine housing (3) has an inlet region (6), in which upstream of the at least one impeller (5) is arranged an adjustable guide (8) by means of Adjusting device (9) comprises rotatable guide vanes (8a), wherein - the adjusting device (9) has a rotatable adjusting ring (9a) which is mounted coaxially with the turbine shaft (4) of the mixed-flow turbine (1), - each vane ( 8a) is arranged on a guide blade-associated shaft (8b), and - pivotable lever (8c) as intermediate elements for the kinematic coupling of the adjusting ring (9a) m the guide vane-associated shafts (8b) are provided, which are each connected at their one shaft-side end (8c ') rotationally fixed to a guide vane-associated shaft (8b) and at its other ring-side end (8c'') movable in a recess (9b) of Adjusting ring (9a) are mounted so that the guide vanes (8a) by means of rotation of the adjusting ring (9a) are adjustable, - each guide blade associated shaft (8b) is rectilinear, - the pivotable lever (8c) are cranked by an acute angle γ , and - the pivotable levers (8c) are directed outwards from the adjusting ring (9a).

Description

• – die Verstelleinrichtung über einen verdrehbaren Verstellring verfügt, der koaxial zur Turbinenwelle der Mixed-Flow-Turbine gelagert ist,
• – jede Leitschaufel auf einer leitschaufelzugehörigen Welle angeordnet ist, und
• – verschwenkbare Hebel als Zwischenelemente zur kinematischen Koppelung des Verstellringes mit den leitschaufelzugehörigen Wellen vorgesehen sind, die jeweils an ihrem einen wellenseitigen Ende verdrehfest mit einer leitschaufelzugehörigen Welle verbunden sind und an ihrem anderen ringseitigen Ende beweglich in einer Ausnehmung des Verstellringes gelagert sind, so dass die Leitschaufeln mittels Verdrehen des Verstellrings verstellbar sind.

The invention relates to an internal combustion engine with an intake system for supplying charge air, a Abgasabführsystem for discharging the exhaust gas and at least one arranged in Abgasabführsystem mixed-flow turbine, which comprises at least one arranged in a turbine housing and mounted on a rotatable turbine shaft impeller and wherein the Turbine housing has an inlet region in which upstream of the at least one impeller, an adjustable guide is arranged, which comprises means of adjusting rotatable vanes, wherein

• The adjusting device has a rotatable adjusting ring which is mounted coaxially with the turbine shaft of the mixed-flow turbine,
• - Each vane is arranged on a guide blade associated shaft, and
• - Swiveling levers are provided as intermediate elements for kinematic coupling of the adjusting ring with the guide shafts associated shafts, which are each connected at its one shaft-side end rotationally connected to a guide shovel associated shaft and are movably mounted at its other ring-side end in a recess of the adjusting, so that the guide vanes are adjustable by turning the adjusting ring.

In the context of the present invention, the term internal combustion engine includes diesel engines and gasoline engines, but also hybrid internal combustion engines, which use a hybrid combustion process, and hybrid drives, which in addition to the internal combustion engine comprise an electric motor which can be electrically connected to the internal combustion engine, which receives power from the internal combustion engine or as switchable auxiliary drive additionally delivers power.

In recent years, there has been a trend toward small, supercharged engines, with supercharging primarily a method of increasing performance by compressing the air needed for the engine combustion process. The economic importance of these engines for the automotive industry continues to increase.

Frequently, an exhaust gas turbocharger is used for charging, in which a compressor and a turbine are arranged on the same shaft. The hot exhaust stream is supplied to the turbine and relaxes with energy release in the turbine, causing the shaft to rotate. The energy emitted by the exhaust gas flow to the turbine and finally to the shaft is used to drive the compressor, which is also arranged on the shaft. The compressor conveys and compresses the charge air supplied to it, whereby a charging of the cylinder is achieved. Advantageously, a charge air cooler is provided downstream of the compressor in the intake system, with which the compressed charge air is cooled before entering the at least one cylinder. The radiator lowers the temperature and thus increases the density of the charge air, so that the cooler to a better filling of the cylinder, d. H. contributes to a larger air mass. There is a compaction by cooling.

The advantage of an exhaust gas turbocharger compared to a mechanical supercharger is that there is no mechanical connection to the power transmission between the supercharger and the internal combustion engine or is required. While a mechanical supercharger obtains the energy required for its drive completely from the internal combustion engine and thus reduces the power provided and thus adversely affects the efficiency, the exhaust gas turbocharger uses the exhaust gas energy of the hot exhaust gases.

The charge is - as already mentioned - the increase in performance. The air required for the combustion process is compressed, which allows each cylinder per working cycle, a larger air mass can be supplied. As a result, the fuel mass and thus the medium pressure can be increased.

The charge is a suitable means to increase the capacity of an internal combustion engine with unchanged displacement or to reduce the displacement at the same power. In any case, the charging leads to an increase in space performance and a lower power mass. If the displacement is reduced, then the load spectrum can be shifted to higher loads, where the specific fuel consumption is lower. By charging in combination with suitable transmission designs and a so-called downspeeding can be realized, in which also a lower specific fuel consumption can be achieved.

Charging thus supports the constant effort in the development of internal combustion engines to minimize fuel consumption, d. H. to improve the efficiency of the internal combustion engine.

Another fundamental goal is to reduce pollutant emissions. In the solution of this task, the charging can also be effective. With targeted design of the charge namely benefits in efficiency and in the exhaust emissions can be achieved.

The torque characteristic of a supercharged internal combustion engine may be improved by use be improved several turbochargers, for example, by a plurality of parallel turbines of smaller turbine cross-section, with successively connected turbines with increasing exhaust gas, or by means of several series-connected exhaust gas turbocharger, of which an exhaust gas turbocharger as a high pressure stage and an exhaust gas turbocharger as a low pressure stage.

In the design of the turbocharger is basically endeavor, the turbine or turbines as close to the outlet of the engine, d. H. near the exhaust ports of the cylinder, to be arranged in order to be able to use the exhaust enthalpy of the hot exhaust gases, which is largely determined by the exhaust pressure and the exhaust gas temperature, optimally and to ensure a fast response of the turbocharger. Not only the way of the hot exhaust gases to the turbine is shortened by a close-coupled arrangement, also the volume of Abgasabführsystems upstream of the turbine decreases. The thermal inertia of the Abgasabführsystems also decreases by reducing the mass and the length of the portion of Abgasabführsystems to the turbine.

For the reasons mentioned above, the exhaust manifold according to the prior art is often integrated in the cylinder head. The integration of the exhaust manifold also allows a dense packaging of the drive unit. In addition, it is possible to participate in a liquid cooling system, which may be provided in the cylinder head, so that the manifold does not have to be manufactured from materials capable of bearing high thermal loads, which are cost-intensive.

According to the state of the art, the turbine arranged in the exhaust-gas removal system can be of different construction. The turbine of an exhaust gas turbocharger is often carried out in a radial construction, ie, the flow of the blades of the impeller is carried out substantially radially. Substantially radial means that the velocity component in the radial direction is greater than the axial velocity component. The velocity vector of the flow cuts the shaft of the turbocharger at a right angle, if the flow is exactly radial. A radial turbine, for example, in the EP 1 710 415 A1 described.

In order to be able to flow radially to the rotor blades, the inlet region for supplying the exhaust gas according to the prior art is designed as a spiral or worm casing running all around, so that the inflow of the exhaust gas to the turbine rotor is essentially radial.

For this purpose, the exhaust gas must be occasionally diverted or deflected in order to be fed to the radial turbine can. In order to use the exhaust gas energy as efficiently as possible, the exhaust gas should, however, be deflected as little as possible. Any change in direction of the exhaust gas flow, for example as a result of a curvature of the Abgasabführsystems, has a pressure drop in the exhaust gas flow and thus enthalpy loss. Frequently, however, a radial turbine can also advantageously be part of the exhaust-gas removal system, for example as a high-pressure turbine of a multi-stage supercharging, and the directional change in the turbine can be used in order to realize a compact design of the supercharger or the internal combustion engine.

Occasionally, the turbine of an exhaust gas turbocharger is also designed as an axial turbine, d. H. the flow of the impeller blades takes place substantially axially. Substantially axial means that the velocity component in the axial direction is greater than the radial velocity component. The velocity vector of the flow in the area of the impeller runs parallel to the shaft of the turbocharger, if the flow is exactly axial.

In the case of axial turbines, the inlet region for supplying the exhaust gas is often designed as a spiral or worm casing running all around, so that at least in the inlet region the flow of the exhaust gas runs obliquely or radially to the shaft. A deflection of the exhaust gas leads to losses in axial turbines at the available exhaust gas enthalpy. The EP 1 710 415 A1 describes such an axial turbine.

In general, turbines in the so-called mixed-flow design are carried out in which the velocity vector of the flow has both a radial velocity component and an axial velocity component. The internal combustion engine, which is the subject of the present invention, also has at least one mixed-flow turbine, which in the present case comprises at least one impeller arranged in a turbine housing and mounted on a rotatable turbine shaft. The used mixed-flow turbine does not necessarily have to be the turbine of an exhaust gas turbocharger. Compared to a pure radial turbine, the mixed-flow turbine is characterized by a lower inertia, which results from the smaller diameter of the impeller.

The used mixed-flow turbine is equipped with a variable turbine geometry, which allows a further adaptation to the respective operating point of the internal combustion engine Adjustment of the turbine geometry or the effective turbine cross-section allowed. In this case, guide vanes for influencing the flow direction are arranged in the inlet region of the turbine. Unlike the vanes of the rotating impeller, the vanes do not rotate with the shaft of the turbine.

If the turbine has a fixed invariable geometry, the vanes are not only stationary, but also completely immovable in the entry area, i. H. rigidly fixed. If, on the other hand, a turbine with variable geometry is used, the vanes are indeed arranged stationary, but not completely immobile, but rotatable about their axis, so that the flow of the blades can be influenced.

In the case of the mixed-flow turbine of the internal combustion engine according to the invention, an adjustable guide device is arranged upstream of the at least one running wheel and comprises guide vanes which can be rotated by means of an adjusting device. The adjusting device has a rotatable adjusting ring which is mounted coaxially with the turbine shaft of the mixed-flow turbine, wherein each guide vane is arranged on a guide vane-associated shaft. The guide vanes are kinematically coupled to the adjusting ring via intermediate elements, so that the guide vanes are adjusted by turning the ring.

The WO 2013/116136 A1 describes such a guide or adjusting device, wherein serve as intermediate elements pivotable lever, which are each connected at its one end via bore rotationally fixed to a guide blade associated shaft and mounted at its other spherical end movable in a recess of the adjusting ring.

A disadvantage of the adjustment described is that the levers are directed starting from the adjusting ring inwards, d. H. the adjusting ring with respect to the lever is an outboard adjusting ring. This leads to large diameters of the adjusting ring, which can not be integrated into the turbine housing, but must be arranged adjacent to the housing. The turbine is thus larger overall, d. H. less compact, in particular their length in the direction of the turbine shaft increases significantly.

In addition, the vane-associated shafts on which the vanes are arranged according to the WO 2013/116136 A1 cranked. This leads to a tumbling motion of the guide vanes during rotation of the guide vane-related shafts by means of adjusting ring, ie to a complex kinematics, which complicates the gap-free arrangement of the rotatable vanes in the inlet region or makes the gap-free arrangement of the vanes in several rotational position impossible.

Against this background, it is the object of the present invention to provide an internal combustion engine according to the preamble of claim 1, with which the disadvantages known from the prior art are overcome and whose variable mixed-flow turbine has an improved adjusting device or guide.

• – die Verstelleinrichtung über einen verdrehbaren Verstellring verfügt, der koaxial zur Turbinenwelle der Mixed-Flow-Turbine gelagert ist,
• – jede Leitschaufel auf einer leitschaufelzugehörigen Welle angeordnet ist, und
• – verschwenkbare Hebel als Zwischenelemente zur kinematischen Koppelung des Verstellringes mit den leitschaufelzugehörigen Wellen vorgesehen sind, die jeweils an ihrem einen wellenseitigen Ende verdrehfest mit einer leitschaufelzugehörigen Welle verbunden sind und an ihrem anderen ringseitigen Ende beweglich in einer Ausnehmung des Verstellringes gelagert sind, so dass die Leitschaufeln mittels Verdrehen des Verstellrings verstellbar sind, die dadurch gekennzeichnet ist, dass
• – jede leitschaufelzugehörige Welle geradlinig ausgebildet ist,
• – die verschwenkbaren Hebel um einen spitzen Winkel γ gekröpft sind, und
• – die verschwenkbaren Hebel ausgehend vom Verstellring nach außen gerichtet sind.

This object is achieved by an internal combustion engine with an intake system for supplying charge air, a Abgasabführsystem for discharging the exhaust gas and at least one arranged in Abgasabführsystem mixed-flow turbine, which comprises at least one arranged in a turbine housing and mounted on a rotatable turbine shaft impeller and at in that the turbine housing has an inlet region in which an adjustable guide device is arranged upstream of the at least one impeller, which comprises rotatable vanes by means of an adjusting device, wherein

• The adjusting device has a rotatable adjusting ring which is mounted coaxially with the turbine shaft of the mixed-flow turbine,
• - Each vane is arranged on a guide blade associated shaft, and
• - Swiveling levers are provided as intermediate elements for kinematic coupling of the adjusting ring with the guide shafts associated shafts, which are each connected at its one shaft-side end rotationally connected to a guide shovel associated shaft and are movably mounted at its other ring-side end in a recess of the adjusting, so that the guide vanes be adjusted by turning the adjusting ring, which is characterized in that
• Each vane-associated shaft is rectilinear,
• - The pivotable levers are cranked at an acute angle γ, and
• - The pivotable lever are directed starting from the adjusting ring to the outside.

Each vane-associated shaft of the internal combustion engine according to the invention is rectilinear. A straight-line design of the shaft simplifies the kinematics of the adjusting device in such a way that rotation of the guide-blade-associated shaft at the adjusting ring-side end causes a pure rotational movement of the associated guide blade, whereas a cranked shaft causes a tumbling motion of the guide blade. By rotating the ring, the vanes are adjusted, the blades perform a pure rotational movement.

As a result, a gap-free arrangement of the rotatable vanes in the inlet region is possible in each rotational position of the blades. The latter is a significant advantage over the prior art, since the exhaust gas flow is to be guided over the guide vanes and not via gap on the vanes.

The pivotable levers are bent at an acute angle γ and thus adapted to kinematically couple the coaxial with the turbine shaft adjusting ring with the vanes, which are each arranged on a - relative to the turbine shaft inclined - wave. The cranking of the levers serves to balance the inclination of the guide vane-associated shafts with the turbine shaft.

In contrast to that in the WO 2013/116136 A1 described prior art, the pivotable lever according to the invention are directed starting from the adjusting ring to the outside.

The adjusting ring forms an internal adjusting ring with respect to the levers. Consequently, the adjusting ring according to the invention can be formed with a comparatively small diameter. Compared with the adjusting rings known from the prior art, the adjusting ring according to the invention smaller diameter can be integrated into the turbine housing, d. H. in the case of a spiral or screw housing, engage in the direction of the exhaust-carrying lines, d. H. arrange next to them. This makes the turbine more compact, less voluminous and shorter in the direction of the turbine shaft. The adjusting ring as such has a lower weight and due to its smaller diameter also a reduced moment of inertia with respect to its rotational movement. Both are advantageous and represents a noticeable improvement over the prior art.

Thereby, the object underlying the invention is achieved, namely provided a supercharged internal combustion engine, with which the disadvantages known from the prior art are overcome and their variable mixed-flow turbine has an improved adjustment or guide.

According to the invention, the guide device has a plurality of rotatable guide vanes, which in the context of the present invention means that the guide device comprises at least two guide vanes, i. H. two vanes, three vanes, four vanes, five vanes, six vanes or more vanes.

Further advantageous embodiments of the internal combustion engine are discussed in connection with the subclaims.

Embodiments of the internal combustion engine in which the ring-side end is crowned are advantageous. This improves the bearing of the lever in the adjusting ring and supports a pivoting movement of the lever during rotation of the adjusting ring. The spherical end can roll during pivoting of the lever in the associated recess of the adjusting ring, whereby the kinematic coupling or assignment between the adjusting ring and the guide vanes is refined and improved.

Embodiments of the internal combustion engine in which the at least one mixed-flow turbine arranged in the exhaust-gas removal system is the turbine of an exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas removal system and a compressor arranged in the intake system are advantageous. Reference is made to the statements made at the outset with regard to the turbocharger.

Embodiments in which the associated compressor of the exhaust-gas turbocharger likewise has a variable compressor geometry are advantageous. Advantages of the variable geometry of the compressor, especially in the operating conditions in which hardly any exhaust gas flows through the mixed-flow turbine and therefore little power is provided by the mixed-flow turbine to compress the charge air. In these cases, the associated compressor merely represents a flow resistance for the charge air. A variable compressor geometry then allows the Entschrosselung of the intake system by increasing the flow cross-section of the compressor.

Embodiments of the internal combustion engine in which at least two exhaust-gas turbochargers are provided, each of which comprises a turbine arranged in the exhaust-gas removal system and a compressor arranged in the intake system, are advantageous.

When using a single exhaust gas turbocharger is observed in the prior art, a significant torque drop falls below a certain speed. This torque drop becomes understandable if it is taken into account that the boost pressure ratio depends on the turbine pressure ratio. If the engine speed is reduced, this leads to a smaller exhaust gas mass flow and thus to a smaller turbine pressure ratio. Consequently, the boost pressure ratio also decreases toward lower speeds. This is synonymous with a torque drop.

The torque characteristic of the supercharged internal combustion engine can be improved by using a plurality of turbochargers arranged in parallel, that is to say by a plurality of turbines of a small turbine cross section arranged in parallel, with turbines being switched on successively as the exhaust gas quantity increases.

The torque characteristic can also be advantageously influenced by means of a plurality of exhaust-gas turbochargers connected in series. By switching in series of two exhaust gas turbochargers, one of which is an exhaust gas turbocharger as a high-pressure stage and an exhaust gas turbocharger as a low-pressure stage, the engine map can be widened in an advantageous manner, both towards smaller compressor streams and towards larger compressor streams.

In particular, in the case of the exhaust gas turbocharger serving as a high-pressure stage, the pumping limit can be shifted towards smaller compressor flows, which means that high boost pressure ratios can be achieved even with small compressor flows, which significantly improves the torque characteristic in the lower rpm range. This is achieved by designing the high-pressure turbine for small exhaust gas mass flows and providing a bypass line, with which increasing exhaust gas mass flow increasingly exhaust gas is passed to the high-pressure turbine. For this purpose, the bypass line branches off the exhaust-gas removal system upstream of the high-pressure turbine and returns to the exhaust-gas removal system upstream of the low-pressure turbine. In the bypass line, a shut-off element is arranged to control the exhaust gas flow passed past the high-pressure turbine.

The downsizing is continued by a multi-stage turbocharger charge. Furthermore, the response of such a supercharged internal combustion engine is significantly improved over a comparable internal combustion engine with single-stage supercharging. The smaller high-pressure stage is less sluggish, because the running gear of a smaller exhaust gas turbocharger accelerates faster.

Therefore, embodiments of the internal combustion engine in which a first exhaust gas turbocharger as a low-pressure stage and a second exhaust gas turbocharger as a high-pressure stage is advantageous, wherein the second turbine of the second exhaust gas turbocharger upstream of the first turbine of the first exhaust gas turbocharger is arranged and the second compressor of the second Exhaust gas turbocharger is arranged downstream of the first compressor of the first exhaust gas turbocharger.

Advantageous embodiments of the internal combustion engine, in which the recesses are formed like a groove. If the recess formed like a groove, the lever can be moved with its verstellringseitigen end stop-free in the associated groove. This has advantages in compensating for changes in length of the vane-associated shafts that result from the thermal stress of the hot exhaust gas.

Embodiments of the internal combustion engine in which the groove-like recesses run parallel to the turbine shaft are advantageous, ie. H. are aligned.

Advantageous embodiments of the internal combustion engine, in which each pivotable lever to the side, which faces away from the associated vane, inclined by the angle γ and thus cranked.

Embodiments of the internal combustion engine in which each shaft associated with the turbine shaft forms an acute angle α are advantageous, with the angle γ of the offset corresponding to the angle α.

A cranking according to the two preceding embodiments is particularly advantageous to compensate for the inclination of the guide vane associated waves to the turbine shaft.

Embodiments of the internal combustion engine in which each shaft associated with the turbine shaft forms an acute angle α, for which the following applies: 15 ° ≦ α ≦ 75 °, are advantageous.

Embodiments of the internal combustion engine in which each shaft associated with the turbine shaft forms an acute angle α are advantageous, for which the following applies: 25 ° ≦ α ≦ 65 °.

Embodiments of the internal combustion engine in which each shaft associated with the turbine shaft forms an acute angle α, for which the following applies: 35 ° ≦ α ≦ 55 °, are advantageous.

Embodiments of the internal combustion engine in which each shaft associated with the turbine shaft forms an acute angle α are advantageous, for which the following applies: 40 ° ≦ α ≦ 75 °.

Embodiments of the internal combustion engine in which each shaft associated with the turbine shaft forms an acute angle α are advantageous, for example: 40 ° ≦ α ≦ 65 °, preferably 45 ° ≦ α ≦ 60 °.

The different angles or angular ranges take into account the fact that the Velocity vector of the flow in a mixed-flow turbine having a radial velocity component and an axial velocity component and the ratio of these two velocity components can vary widely, ie the inlet region in which the vanes are arranged and by which the flow is substantially fixed more or less inclined to the turbine shaft. Consequently, the angle α between the turbine shaft and a vane-associated shaft can also vary widely.

Advantageous embodiments of the internal combustion engine, in which each lever is connected at the shaft-side end via bore rotationally fixed to the associated shaft. A non-positive rotationally fixed connection between the lever and the guide vane-associated shaft can be realized on the shaft side by shrinking the bore onto the shaft. Additional fasteners omitted, d. H. are not required.

Advantageous embodiments of the internal combustion engine, in which an actuating device is provided, by means of which the adjusting ring is rotatable.

According to this embodiment, the adjusting ring is not actuated directly, d. H. twisted to adjust the vanes. The adjusting ring serves primarily for the kinematic coordination of the adjusting ring side mounted lever.

In this context, embodiments of the internal combustion engine are advantageous in which the actuating device is arranged on the side of the adjusting ring, which faces away from the at least one impeller of the turbine. The external arrangement allows good accessibility, whereas the adjusting ring according to the invention is an internal adjusting ring, which can indeed be dimensioned relatively small by its internal arrangement, but also less accessible.

Advantageous embodiments of the internal combustion engine, in which the mixed-flow turbine has a coaxial with the turbine shaft extending and formed outlet region, so that the outflow of the exhaust gas from the turbine takes place substantially axially.

If the mixed-flow turbine is, for example, the high-pressure turbine of a multi-stage supercharger, the outlet region formed coaxially with the turbine shaft, in cooperation with a downstream axial-pressure low-pressure turbine, permits axial delivery of the exhaust gas to the low-pressure turbine as pressure-free as possible and thus the provision of enthalpy-rich exhaust gas at the low pressure stage.

Embodiments of the internal combustion engine in which exhaust gas recirculation is provided are advantageous.

To comply with future limits for nitrogen oxide emissions, an exhaust gas recirculation is increasingly used, ie the return of exhaust gases from the exhaust side to the inlet side, in which the nitrogen oxide emissions can be significantly reduced with increasing exhaust gas recirculation rate. In this case, the exhaust gas recirculation rate x _{AGR is} determined by x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _{AGR designates} the mass of recirculated exhaust gas and m _{fresh air} the supplied fresh air or combustion air, possibly guided and compressed by a compressor. In order to achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates are required. Exhaust gas recirculation is also suitable for reducing emissions of unburned hydrocarbons in the partial load range.

Embodiments in which a shut-off element is provided in the line for exhaust gas recirculation are advantageous. This shut-off element is used to control the exhaust gas recirculation rate.

In this connection, embodiments of the internal combustion engine in which exhaust gas recirculation is provided, which includes a line which branches off from the exhaust gas removal system downstream of the mixed-flow turbine, are advantageous.

In contrast to a high pressure EGR, which removes exhaust gas from the exhaust gas removal system upstream of the turbine, exhaust gas is returned to the inlet side in a low pressure EGR which has already passed through the turbine. For this purpose, the low-pressure EGR comprises a return line, which branches off from the exhaust-gas removal system downstream of the turbine. The exhaust gas recirculated to the inlet side by means of low-pressure EGR thus beforehand serves to generate energy in the mixed-flow turbine.

In the following the invention is based on an embodiment according to the 1a and 1b described in more detail. Hereby shows:

1a schematically the mixed-flow turbine of a first embodiment of the internal combustion engine, partially cut, and

1b schematically a fragment of the adjustment of in 1a illustrated mixed-flow turbine in side view.

1a schematically shows the mixed-flow turbine 1 a first embodiment of the supercharged internal combustion engine. The velocity vector of the flow in the inlet area 6 the turbine 1 has a radial component perpendicular to the shaft 4 the turbine 1 and an axial component along the shaft 4 on. This is the entrance area 6 opposite the turbine shaft 4 inclined.

For discharging the hot exhaust gases from the cylinders, the internal combustion engine has an exhaust gas removal system 2 , For the purpose of charging the cylinders, at least one exhaust-gas turbocharger is provided which has one in the exhaust-gas removal system 2 arranged mixed-flow turbine 1 includes.

The mixed-flow turbine 1 includes a in a turbine housing 3 arranged and on a rotatable turbine shaft 4 stored impeller 5 , The as a spiral housing 3 trained turbine housing 3 has an entrance area 6 , in the upstream of the impeller 5 an adjustable guide 8th is arranged so that it is the mixed-flow turbine 1 around a variable turbine 1 is.

The guide 8th has vanes 8a , each on a vane-related shaft 8b are arranged and the means of adjustment 9 are rotatable. The guide vane-related waves 8b make up with the turbine shaft 4 ie with its longitudinal axis 4a , In each case an acute angle α and are formed in a straight line, so that a turning on Verstellringseitigen end of the guide vane associated waves 8b a rotational movement of the associated vanes 8a causes. The adjusting device 9 has an internally rotatable adjusting ring 9a , which is coaxial with the turbine shaft 4 the mixed-flow turbine 1 is stored.

For the kinematic coupling of the adjusting ring 9a with the vane-associated shafts 8b are swiveling levers 8c provided as intermediate elements, each at its one shaft-side end 8c' rotationally fixed with a guide blade associated shaft 8b connected and at the other end of the ring 8c'' movable in a recess 9b the adjusting ring 9a are stored, so that the vanes 8a by turning the adjusting ring 9a are adjustable.

The swiveling lever 8c are starting from the adjusting ring 9a directed outwards and inclined at an acute angle γ and thus cranked at its shaft-side end 8c' to the side, by the associated vane 8a turned away. The angle of inclination, that is, the offset angle γ, corresponds to the angle α of each guide vane-associated shaft 8b with the turbine shaft 4 forms.

The turbine 1 has an exit area 7 , which is coaxial with the turbine shaft 4 runs, so that the outflow of the exhaust gas in the exit area 7 the turbine 1 essentially axially.

1b schematically shows a fragment of the adjustment 9 the in 1a illustrated mixed-flow turbine 1 in the side view. It will be complementary to 1a executed.

The recesses 9b are formed like a groove, so that each lever 8c at its Verstellringseitigen end 8c`` in the associated groove 9b is displaceable. This allows compensation for changes in the length of the guide vane associated waves 8b which can result from the thermal stress of the hot exhaust gas. The grooves 9b are present parallel to the turbine shaft 4 aligned.

The ring-side end 8c'' each lever 8c is formed spherical, whereby the pivoting movement or the rolling of the lever 8c when turning the adjusting ring 9a supported in an advantageous manner.

At the wave-side end 8c' is every lever 8c via hole 8d with the associated shaft 8b connected, wherein a non-positive rotational connection between the lever 8c and wave 8b is trained.

It is an actuator 10 provided in the form of a lever or a rod, by means of which the adjusting ring 9a is rotatable.

LIST OF REFERENCE NUMBERS

1

 Mixed-flow turbine

2

 Abgasabführsystem

3

 Turbine housing, spiral housing

4

 Wave of the turbine

4a

 longitudinal axis

5

 Impeller of the turbine

6

 Entry area of the turbine

7

 Exit area of the turbine

8th

 guide

8a

 vane

8b

 vane-associated shaft

8c

 lever

8c'

 shaft end of a lever

8c''

 ring-side end of a lever

8d

 drilling

9

 adjustment

9a

 adjusting

9b

 Recess of the adjusting ring, groove

10

 actuator

AGR

 Exhaust gas recirculation

m _AGR

 Mass of recirculated exhaust gas

_{Fresh air}

 Mass of supplied fresh air or combustion air

x _AGR

 Exhaust gas recirculation rate

α

 Angle between the turbine shaft and a vane-associated shaft

γ

 Angle around which a lever is inclined, d. H. is cranked

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

• EP 1710415 A1 [0013, 0017]
• WO 2013/116136 A1 [0022, 0024, 0030]

Claims (15)

Internal combustion engine with an intake system for supplying charge air, an exhaust gas discharge system ( 2 ) for discharging the exhaust gas and at least one in the Abgasabführsystem ( 2 ) arranged mixed-flow turbine ( 1 ), which at least one in a turbine housing ( 3 ) and mounted on a rotatable turbine shaft ( 4 ) stored impeller ( 5 ) and in which the turbine housing ( 3 ) an entrance area ( 6 ), in which upstream of the at least one impeller ( 5 ) an adjustable guide ( 8th ) is arranged, which by means of adjusting ( 9 ) rotatable vanes ( 8a ), wherein - the adjusting device ( 9 ) via a rotatable adjusting ring ( 9a ), which is coaxial with the turbine shaft ( 4 ) of the mixed-flow turbine ( 1 ), - each vane ( 8a ) on a vane-associated shaft ( 8b ), and - pivotable levers ( 8c ) as intermediate elements for the kinematic coupling of the adjusting ring ( 9a ) with the guide vane-associated shafts ( 8b ) are provided, each at its one wave-side end ( 8c' ) rotationally fixed with a guide blade associated shaft ( 8b ) and at its other end ( 8c'' ) movable in a recess ( 9b ) of the adjusting ring ( 9a ) are stored so that the guide vanes ( 8a ) by turning the adjusting ring ( 9a ) are adjustable, characterized in that - each guide vane-associated shaft ( 8b ) is rectilinear, - the pivotable lever ( 8c ) are cranked at an acute angle γ, and - the pivotable levers ( 8c ) starting from the adjusting ring ( 9a ) are directed outwards. Internal combustion engine according to claim 1, characterized in that the ring-side end ( 8c'' ) is formed spherical. Internal combustion engine according to claim 1 or 2, characterized in that the at least one in Abgasabführsystem ( 2 ) arranged mixed-flow turbine ( 1 ) the turbine ( 1 ) of an exhaust gas turbocharger, which is one in the Abgasabführsystem ( 2 ) arranged turbine ( 1 ) and a compressor arranged in the intake system. Internal combustion engine according to one of the preceding claims, characterized in that at least two exhaust gas turbochargers are provided, each one in Abgasabführsystem ( 2 ) arranged turbine ( 1 ) and a compressor arranged in the intake system. Internal combustion engine according to claim 4, characterized in that a first exhaust gas turbocharger is used as a low pressure stage and a second exhaust gas turbocharger as a high pressure stage, wherein the second turbine ( 1 ) of the second exhaust gas turbocharger upstream of the first turbine ( 1 ) of the first exhaust gas turbocharger is arranged and the second compressor of the second exhaust gas turbocharger is arranged downstream of the first compressor of the first exhaust gas turbocharger. Internal combustion engine according to one of the preceding claims, characterized in that the recesses ( 9b ) are formed like a groove. Internal combustion engine according to one of the preceding claims, characterized in that each pivotable lever ( 8c ) at its shaft end ( 8c` ) to the side of the associated vane ( 8a ) is turned away, inclined by the angle γ and is thus cranked. Internal combustion engine according to one of the preceding claims, characterized in that each guide blade-associated shaft ( 8b ) with the turbine shaft ( 4 ) forms an acute angle α, wherein the angle γ of the crank corresponds to the angle α. Internal combustion engine according to one of the preceding claims, characterized in that each guide blade-associated shaft ( 8b ) with the turbine shaft ( 4 ) forms an acute angle α, for which applies: 15 ° ≤ α ≤ 75 °. Internal combustion engine according to one of the preceding claims, characterized in that each guide blade-associated shaft ( 8b ) with the turbine shaft ( 4 ) forms an acute angle α, for which applies: 25 ° ≤ α ≤ 65 °. Internal combustion engine according to one of the preceding claims, characterized in that each guide blade-associated shaft ( 8b ) with the turbine shaft ( 4 ) forms an acute angle α, for which applies: 35 ° ≤ α ≤ 55 °. Internal combustion engine according to one of the preceding claims, characterized in that each guide blade-associated shaft ( 8b ) with the turbine shaft ( 4 ) forms an acute angle α, for which applies: 40 ° ≤ α ≤ 75 °. Internal combustion engine according to one of the preceding claims, characterized in that each lever ( 8c ) at the shaft end ( 8c' ) via bore ( 8d ) rotationally fixed with the associated shaft ( 8b ) connected is. Internal combustion engine according to one of the preceding claims, characterized in that an actuating device ( 10 ) is provided, by means of which the adjusting ring ( 9a ) is rotatable. Internal combustion engine according to one of the preceding claims, characterized in that the mixed-flow turbine ( 1 ) a coaxial with the turbine shaft ( 4 ) extending and formed exit area ( 7 ), so that the outflow of the exhaust gas from the turbine ( 1 ) is effected substantially axially.

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