Method of and Apparatus For Improved Utilization of the Thermal Energy Contained in a Gaseous Medium

Abstract

The present invention concerns a method of utilising the waste heat contained in the exhaust gas of an internal combustion engine, comprising a turbine ( 20 ). To provide an apparatus and a method of operating same which directly supplies additional drive energy which otherwise would be lost as waste heat, it is proposed according to the invention that the turbine is an inverse turbine connected downstream of the exhaust gas outlet of the internal combustion engine and comprising at the inlet side an expansion stage ( 23 ) and at the outlet side a subsequent compressor ( 21 ), wherein the expansion stage and the compressor of the inverse turbine are so designed that the downstream-disposed compressor of the inverse turbine generates at the outlet of the expansion stage ( 23 ) a reduced pressure (p 1 ) below the ambient pressure (p 0 ), wherein the outlet ( 2 b ) of the compressor ( 21 ) is at the level of the ambient pressure and the compressor of the inverse turbine is driven by the turbine.

1 . A method of utilising the waste heat contained in the exhaust gas of an internal combustion engine, comprising a turbine ( 10 ), characterised in that at least a part of the exhaust gas acts on an inverse turbine ( 20 ) which at the inlet side comprises an expansion stage ( 23 ) and at the outlet side a subsequent compressor ( 21 ), wherein the expansion stage and the compressor of the inverse turbine are operated in such a way that the downstream-connected compressor of the inverse turbine generates at the outlet of the expansion stage ( 23 ) a reduced pressure (p 1 ) below the ambient pressure (p 0 ), wherein the outlet ( 2   b ) of the compressor ( 21 ) is at the level of the ambient pressure and the compressor is driven by the turbine. 
     
     
         2 . A method according to  claim 1  characterised in that it is applied to a gas turbine, wherein the pressure ratio of the compressor of the gas turbine is set to at least 10, and the pressure ratio between the outlet and the inlet of the expansion stage is set to at least 10. 
     
     
         3 . A method according to  claim 1  characterised in that the reduced pressure at the outlet of the expansion stage of the inverse turbine is promoted by intercooling, i. e. by means of an intercooler, in particular a heat exchanger. 
     
     
         4 . A method according to  claim 1  characterised in that the inverse turbine is operated at a speed of rotation which is different from the speed of rotation of the upstream-disposed turbine. 
     
     
         5 . Apparatus for utilising the waste heat contained in the exhaust gas of an internal combustion engine, comprising a turbine ( 11 ,  13 ), characterised in that the turbine is an inverse turbine connected downstream of the exhaust gas outlet of the internal combustion engine and comprising at the inlet side an expansion stage ( 23 ) and at the outlet side a subsequent compressor ( 21 ), wherein the expansion stage and the compressor of the inverse turbine are so designed that the downstream-disposed compressor of the inverse turbine generates at the outlet of the expansion stage ( 23 ) a reduced pressure (p 1 ) below the ambient pressure (p 0 ), wherein the outlet ( 2   b ) of the compressor ( 21 ) is at the level of the ambient pressure and the compressor of the inverse turbine is driven by the turbine. 
     
     
         6 . Apparatus according to  claim 5  characterised in that the expansion stage ( 1 ) and the compressor ( 2 ) rotate about the same axis. 
     
     
         7 . Apparatus according to  claim 5  characterised in that the compressor ( 2 ) is connected to the turbine shaft by way of an interposed transmission ( 5 ). 
     
     
         8 . Apparatus according to  claim 5  characterised in that the volume of the compressor ( 11 ) and the expansion chamber ( 13 ) of the turbine is respectively smaller by a factor of 1.2 to 4, than the volume of the compressor ( 21 ) and the expansion stage ( 23 ) of the inverse turbine. 
     
     
         9 . Apparatus according to  claim 5  characterised in that the expansion stage and/or the compressor have at least one diffuser, the interior of which has a coolant at least partially flowing therethrough. 
     
     
         10 . Apparatus according to  9   claim 5  characterised in that the expansion stage ( 1 ) is connected downstream of the last stage of a gas turbine ( 6 ) and is driven by the exhaust gas from the gas turbine ( 6 ) and the pressure drop generated by the compressor ( 2 ). 
     
     
         11 . A combination of a gas turbine ( 19 ) with an inverse turbine ( 20 ) according to  claim 5  characterised in that devices for the feed of additional fuel are provided after the outlet of the gas turbine and preferably before or in the inverse turbine. 
     
     
         12 . Apparatus according to  claim 5  characterised in that the expansion stage ( 1 ) is connected to an exhaust gas outlet of an internal combustion engine and is driven by the exhaust gas of the internal combustion engine and the pressure drop generated by the compressor ( 2 ). 
     
     
         13 . An aircraft engine characterised by an apparatus according to  claim 5 . 
     
     
         14 . An aircraft engine according to  claim 13  comprising an outer housing  1  and an inner engine housing  2 , between which there are provided support elements and a stationary diffuser ( 26 ), wherein a fan ( 25 ) driven by a first turbine shaft ( 14 ) generates an axial air flow between the outer ( 1 ) and the inner housings ( 2 ), characterised in that provided at the end of the turbine shaft ( 14 ), that is remote from the fan, is an inverse turbine ( 23   b ) with a concluding compressor ( 21 ) and a cooling device ( 22 ) arranged therebetween. 
     
     
         15 . An aircraft engine according to  claim 13  comprising a heat exchanger between the expansion stage and the compressor of an inverse turbine, wherein cooling conduits extend through the housing and possibly through diffusers provided in the cooling device and in diffuser blades and contain a coolant to cool exhaust gases in the cooling chamber ( 22 ). 
     
     
         16 . A method according to  claim 1  characterised in that it is applied to a gas turbine, wherein the pressure ratio of the compressor of the gas turbine is set to at least 15, and the pressure ratio between the outlet and the inlet of the expansion stage is set to at least 15. 
     
     
         17 . Apparatus according to  claim 6  characterised in that the expansion stage ( 1 ) and the compressor ( 2 ) are mounted on a common shaft. 
     
     
         18 . Apparatus according to  claim 8  characterised in that the volume of the compressor ( 11 ) and the expansion chamber ( 13 ) of the turbine is respectively smaller by a factor of 1.2 to 2.5 than the volume of the compressor ( 21 ) and the expansion stage ( 23 ) of the inverse turbine.