Device and method for separating dirt particles from the working medium of a turbine

The invention relates to a device and a method for separating dirt particles from the working medium of a turbine (10). The turbine (10) comprises at least one rotor (11) which is arranged in a housing (17). A swirl generator (20) is provided that sets the working medium and the dirt particles in a spiral-shaped rotational movement along a principal axis (22) by means of the geometry of the swirl generator (20) and thereby separates the dirt particles from the working medium. The swirl generator (20) is designed in such a way that the working medium experiences a reversal of the speed component parallel to the principal axis (22) within the swirl generator (20).

BACKGROUND OF THE INVENTION

The invention relates to a device and method for separating dirt particles from the working medium of a turbine.

The European patent publication EP 2 137 397 B1 discloses an arrangement for supplying an internal combustion engine with a stream of combustion air and for removing a stream of exhaust gas, in which arrangement a swirl generator is designed as a centrifugal separator for condensate forming in the exhaust gas return stream. An effective separation can be brought about without additional measures by using the centrifugal forces or, respectively, mass inertia forces which occur anyway in the swirl generator and act on condensate that has formed.

A turbocharger for an internal combustion engine is known from the German patent publication DE 10 2007 030 277 A1. A centrifugal separator, which is coupled to the shaft, is disposed between a compressor wheel and the turbocharger in an intermediate chamber. The centrifugal separator is used as a separator for fluid/oil from the crankcases.

SUMMARY OF THE INVENTION

The device and method for separating dirt particles from the working medium of a turbine according to the invention have the advantage that a separation of dirt particles from the working medium of the turbine is implemented in a particularly compact and space-saving design. By reversing the speed component of the working medium parallel to a principal axis, the installation space of the swirl generator can be reduced approximately by half of the length otherwise required because the working medium flows twice through the same distance within the swirl generator. This is especially important for applications of turbines within motor vehicles because only a small amount of installation space is available within the engine compartment of the motor vehicle.

A device is advantageous in which the swirl generator is designed as a hollow body which is approximately rotationally symmetrical and into which a pipe protrudes that constitutes a connection to the turbine. As a result of the rotationally symmetrical hollow body, the working medium and the dirt particles experience the spiral-shaped rotational movement with the speed component parallel to the principal axis until said medium and dirt particles have arrived at the end of the hollow body. The working medium experiences a reversal of the speed component parallel to the principal axis on at least one reflection surface, i.e. a change in direction of the spiral-shaped movement during which the sign of the speed component parallel to the principal axis changes. As a result, the working medium flows in a spiral-shaped rotational movement in the opposite direction through the pipe into the housing of the turbine. Due to the inertia of the dirt particles, said particles do not experience a reversal of the speed component parallel to the principal axis and are therefore separated from the working medium. The arrangement of the pipe within the hollow body constitutes an efficient and space-saving design for separating working medium comprising dirt particles and working medium without dirt particles.

An especially compact and space-saving design of the swirl generator is ensured if the pipe which protrudes into the hollow body of the swirl generator is formed by the housing of the turbine. In this case, the swirl generator does not have to be spatially disposed upstream of the turbine but can be disposed as an approximately rotationally symmetrical hollow body around the housing of the turbine. In addition, costs are saved due to the multiple use of the same component, e.g. housing being used as pipe.

The principal rotational direction can be predefined for the spiral-shaped rotational movement by means of an inlet pipe into the swirl generator, which is designed in such a manner that the working medium has a further speed component tangential to the wall of the hollow body upon entry into the swirl generator. The principal rotational direction is to be understood here as the rotational direction of the spiral-shaped rotational movement, in which a clockwise rotational direction can be distinguished from a counterclockwise rotational direction. This is advantageous because the flow angle at which the working medium strikes the rotor or the laval nozzles directly upstream of the rotor can be influenced by the selection of the rotational direction.

A further advantage results from an inside radius of the hollow body which decreases along the principal axis between the supply line and the outflow wall located opposite the pipe. This is advantageous because the rotational speed of the working medium containing the dirt particles increases; thus enabling the dirt particles to be thrown more strongly against the walls of the hollow body due to the higher centrifugal force and to thereby be decelerated so that they can more easily separate themselves from the flow.

The arrangement of at least one bore on the outflow wall of the hollow body that is opposite the pipe is advantageous. The dirt particles can be removed in a simple and efficient way from the swirl generator by means of an outlet line connected to the bore. This can, e.g., be implemented by the buildup of a pressure gradient.

Especially in the case of a turbine, which is disposed in a system for heat recovery in an internal combustion engine, an arrangement of a swirl generator directly upstream of the turbine for separating dirt particles from the working medium is advantageous. In the system for heat recovery in an internal combustion engine, the working medium flows through a circuit in which at least one heat exchanger, the turbine, at least one condenser and at least one pump are disposed in succession. The working medium therefore flows through the turbine a number of times and is not replaced for each passage through the turbine, as is the case in other applications as, e.g., in the case of a turbocharger or in a thermal power plant for industrial applications. As a result of the circular process within the system for heat recovery in an internal combustion engine, the working medium becomes permanently contaminated by dirt particles, as, e.g., lubricants. The dirt particles can cause damage to the turbine or other components of the aforementioned system for heat recovery as a result of erosion, deposition or droplet impact. A reduction in the dirt particles in the working medium occurs by means of the proposed device and the proposed method before each passage of said working medium through the turbine. The concentration of dirt particles in the working medium can therefore be permanently reduced.

DETAILED DESCRIPTION

A turbine10comprising a rotor11, which is disposed in a housing17, is shown inFIG. 1. A working medium, which is used to drive the turbine, arrives at the rotor11via a supply line12, said rotor being set in a rotational movement by the working medium. The kinetic energy of the rotor11can be converted into further energy forms.

A nozzle arrangement13can be disposed upstream of the rotor11. This can be a laval nozzle which leads to an acceleration of the working medium prior to striking the rotor11.

A swirl generator20is disposed directly on the input side of the turbine10. The swirl generator20is formed from a hollow body24which is approximately rotationally symmetrical and which is fastened to the front face of the housing17of the turbine10. The hollow body24has an inlet line28. The working medium can move into the hollow body24of the swirl generator20by means of the inlet line28. On account of the inlet line28, the rotational symmetry is interrupted in at least one region of the hollow body24.

The inlet line28can be designed such that the working medium has at least one further speed component parallel to an inner wall25of the hollow body24.

A pipe26, which constitutes a connection to the turbine10, is disposed within the hollow body24. The pipe26can be formed by the housing17of the turbine10. The pipe can, however, also be a separate component of the swirl generator20, which is flanged to the housing17of the turbine10by means of a connection that is as impermeable as possible. Working medium which has flowed into the swirl generator20moves through the pipe26into the supply line12of the turbine10.

An outlet line23is disposed on an outflow wall27located opposite the pipe26. The outlet line23can be connected to the hollow body24via a bore in the center of the outflow wall27. Further positions of the bore within the outflow wall27are also possible. Said positions can be selected as a function of the geometry of the hollow body24.

The device shown inFIG. 1is used to separate dirt particles from the working medium of the turbine10. The working medium of the turbine can be steam which is under high pressure. Other working mediums are, however, also possible which can be used to drive a turbine10. Dirt particles can accumulate within the working medium, as, e.g., lubricants which come from the bearings of the turbine10. These dirt particles can lead to damage within the turbine10due to droplet impact or erosion. In addition, undesirable depositions of dirt particles can occur within the turbine10or within the components downstream of the turbine10.

In order to remove the dirt particles from the working medium of the turbine10, the working medium containing the dirt particles is led via the inlet line28into the swirl generator20directly upstream of the turbine10.

By way of example,FIG. 2shows how the dirt particles are removed from the working medium within the swirl generator20. The working medium containing the dirt particles passes through the inlet line28into the approximately rotationally symmetrical hollow body24. Due to the geometry of the hollow body24and the orientation of the inlet line28with respect to the inner wall25of the hollow body24, the working medium containing the dirt particles is set into the spiral-shaped rotational movement with the speed component parallel to the principal axis22. The working medium and the dirt particles move in a spiral-shaped rotational movement along an outer main vortex7of the inlet line28in the direction of the outlet line23.

Centrifugal forces act on the working medium and the dirt particles by means of the spiral-shaped rotational movement, said centrifugal forces produce a radial force that is directed outwards on the working medium and the dirt particles. Due to the different size and thickness of the particles of the working medium and the dirt particles, a spatial separation of the working medium from the dirt particles occurs during this spiral-shaped rotational movement.

The working medium experiences a reflection on at least one reflection surface of the hollow body24which leads to a reversal of the speed component parallel to the principal axis22and therefore to a change in sign of the corresponding speed component so that an inner partial vortex9forms which is in the opposite direction of the outer main vortex7. In contrast, the dirt particles do not experience a reversal of the speed component parallel to the principal axis22so that they continue to move in the direction of the outlet line23. This causes a separation of working medium and dirt particles. While the working medium and the dirt particles are still situated in the outer main vortex, the proportion of dirt particles in the inner partial vortex is greatly reduced.

The at least one reflection surface can be formed by any wall of the hollow body24. An arrangement according toFIG. 1, in which the at least one reflection surface is formed by the outflow wall27, is particularly advantageous.

The inner partial vortex9moves with a spiral-shaped rotational movement in the opposite direction of the outer main vortex7. Furthermore, the radius of the inner partial vortex9is smaller than the radius of the outer main vortex7so that a mixing of the working medium from the outer main vortex7and the inner partial vortex9hardly occurs.

The working medium of the inner partial vortex9moves in the direction of the pipe26, through which the working medium passes into the supply line12of the turbine20, due to the opposite speed component with respect to the main vortex22.

In contrast, the dirt particles move in the direction of the outlet line23and can be removed from the swirl generator through said outlet line23.

The hollow body24is formed by a cone in the depiction inFIG. 2so that the inside radius of the hollow body24decreases along the principal axis22between the inlet line28and the outlet line23opposite the pipe12. By means of the reduction of the inside radius, the rotational speed of the working medium increases so that the articles of dirt particles are thrown more strongly against the inner wall25of the hollow body24as a result of centrifugal force. This leads to a deceleration of the dirt particles, which thus are released from the flow and move along the inner wall25of the hollow body to the outlet line23. In the case of heavy dirt particles, a separation also occurs between working medium and dirt particles if the inside radius of the hollow body24is only slightly reduced or not reduced at all.

A schematic depiction of a system for heat recovery30in an internal combustion engine31is shown inFIG. 3. The system is formed by a circuit in which the turbine10, at least one condenser34, at least one pump36and at least one heat exchanger are disposed in succession. A corresponding system is described in the German patent application DE 10 2010 043 405. Corresponding explanations from said German patent application DE 10 2010 043 405 as to the functionality of a corresponding system for heat recovery are also considered to be a constituent part of this application.

The working medium passes through the system for heat recovery30within the framework of a circular process and, in so doing, is not exchanged. This leads to a permanent accumulation of dirt particles in the working medium so that, precisely here, the device and the method for separating dirt particles from the working medium take on a great deal of importance.