Waste heat recovery system

Abstract

The invention relates to a waste heat recovery system (1) comprising a working fluid circuit (18), having a heat exchanger which is connected in an exhaust gas line (4) of an internal combustion engine (2). The heat exchanger is part of the working fluid circuit (18) together with an expansion machine (20) which has at least one working fluid bypass (21) that is controlled by a valve. According to the invention, a waste heat recovery system (1) is provided with improved functionality. This is achieved in that the valve is a directional valve which connects a fluid inlet (36) to an expansion machine fluid outlet (37) and/or a bypass fluid outlet (38), in particular a 3/2-way valve (22), and the connection of the fluid inlet (36) to the expansion machine fluid outlet (37) is leakage-free relative to the bypass fluid outlet (38), whereas the connection of the fluid inlet (36) to the bypass fluid outlet (38) exhibits leakages with respect to the expansion machine fluid outlet (37).

1 . A waste-heat recovery system ( 1 ) with a working fluid circuit ( 18 ) having a heat exchanger connected into an exhaust-gas line ( 4 ) of the internal combustion engine ( 2 ), wherein the heat exchanger is part of the working fluid circuit ( 18 ) with at least one expansion machine ( 20 ) which has a working fluid bypass ( 21 ) controlled by a valve, wherein the valve is a directional valve ( 22 ) which connects a fluid inlet ( 36 ) to an expansion machine fluid outlet ( 37 ) and/or to a bypass fluid outlet ( 38 ), and wherein a connection made between the fluid inlet ( 36 ) and the expansion machine fluid outlet ( 37 ) exhibits no leakage to the bypass fluid outlet ( 38 ). 
     
     
         2 . The waste-heat recovery system ( 1 ) as claimed in  claim 1 , characterized in that a connection made between fluid inlet ( 36 ) and the bypass fluid outlet ( 38 ) exhibits leakage, with a leakage quantity ( 46   a ,  46   b ), to the expansion machine fluid outlet ( 37 ). 
     
     
         3 . The waste-heat recovery system ( 1 ) as claimed in  claim 2 , characterized in that the leakage quantity ( 46   a ,  46   b ) is less than  10 % of the maximum volume flow of the working fluid. 
     
     
         4 . The waste-heat recovery system ( 1 ) as claimed in  claim 2 , characterized in that the directional valve ( 22 ) has a slide ( 31 ) with two opposite switching positions that can be assumed by the slide ( 31 ). 
     
     
         5 . The waste-heat recovery system ( 1 ) as claimed in  claim 2 , characterized in that the directional valve ( 22 ) has a slide housing ( 30 ) and a slide ( 31 ) which is displaceable in said slide housing axially counter to the force of a spring ( 32 ), which slide has a permanent flow connection to the fluid inlet ( 36 ) and can be adjusted in each case into a flow connection with the bypass fluid outlet ( 38 ) and with the expansion machine fluid outlet ( 37 ). 
     
     
         6 . The waste-heat recovery system ( 1 ) as claimed in  claim 2 , characterized in that the directional valve ( 22 ) has a bypass fluid outlet seat ( 40 ) configured to have an end-side slide seat ( 41 ) of the slide ( 31 ) engaged therein with sealing action. 
     
     
         7 . The waste-heat recovery system ( 1 ) as claimed in  claim 2 , characterized in that the slide housing ( 30 ) has an expansion machine fluid outlet seat ( 43 ) configured to have a slide edge ( 44 ) of the slide ( 31 ) engaged therein with sealing action. 
     
     
         8 . The waste-heat recovery system ( 1 ) as claimed in  claim 6 , characterized in that the slide seat ( 41 ) is arranged on a slide base wall of the slide ( 31 ) of piston-like form, and in that the slide base wall has passage openings ( 45 ) for an unhindered throughflow of the working fluid. 
     
     
         9 . The waste-heat recovery system ( 1 ) as claimed in  claim 4 , characterized in that the slide ( 31 ) interacts with an actuator ( 33 ). 
     
     
         10 . The waste-heat recovery system ( 1 ) as claimed in  claim 2 , characterized in that the leakage quantity ( 46   a ,  46   b ) is less than 1% of the maximum volume flow of the working fluid,