Air handling in a heavy-duty opposed-piston engine

Abstract

An air handling arrangement in a two-stroke cycle, opposed-piston engine with uniflow scavenging and constructed for heavy-duty operation includes sequentially arranged turbochargers in series with a supercharger, in some aspects, the air handling system is equipped with an EGR channel.

1 . A two-stroke cycle, uniflow-scavenged, opposed-piston engine ( 80 ,  302 ), comprising:
 one or more cylinders ( 50 ), each cylinder comprising a bore ( 52 ), longitudinally-separated exhaust and intake ports ( 54  and  56 ), and a pair of pistons ( 60  and  62 ) disposed in the bore for opposing movements therein, in which movement of a first piston of the pair of pistons controls the exhaust port and movement of the second piston of the pair of pistons controls the intake port;   a supercharger ( 305 ) disposed in fluid communication with the intake ports ( 56 ) to provide a continuous positive pressure differential from the intake ports ( 56 ) to the exhaust ports ( 54 ) so as to maintain a unidirectional flow of gas from the intake ports to the exhaust ports during two-stroke operation of the engine;   characterized by:   a sequential turbocharger ( 306 ), including a first turbocharger ( 312 ) and a second turbocharger ( 314 ), each of the turbochargers including a turbine and a compressor, in which the compressors of the first and second turbochargers are arranged in series with the supercharger ( 305 ) such that the compressor of the first turbocharger ( 312 ) is in fluid communication with the compressor of the second turbocharger ( 314 ) and the compressor of the second turbocharger ( 314 ) is in fluid communication with the supercharger ( 305 ), and the turbines of the first and second turbochargers are arranged in series with the exhaust ports ( 54 ) such that the turbine of the second turbocharger ( 314 ) is in fluid communication with the exhaust ports ( 54 ) and the turbine of the first turbocharger ( 312 ) is in fluid communication with the turbine of the second turbocharger ( 314 );   a compressor bypass valve ( 316   c ) associated with the second turbocharger ( 314 ) and disposed in parallel with the compressor of the second turbocharger, the compressor bypass valve ( 316   c ) having a closed setting that causes pressurized air from the compressor of the first turbocharger ( 312 ) to pass through the compressor of the second turbocharger ( 314 ) and an open setting that directs pressurized air from the compressor of the first turbocharger ( 312 ) past the compressor of the second turbocharger ( 314 ) to an inlet of the supercharger ( 305 ); and,   a turbine bypass valve ( 316   t ) associated with the second turbocharger ( 314 ) and disposed in parallel with the turbine of the second turbocharger ( 314 ), the turbine bypass valve ( 316   t ) having a closed setting that causes exhaust gasses from the exhaust ports ( 54 ) to pass through the turbine of the second turbocharger ( 314 ) and an open setting that directs exhaust gasses from the exhaust ports ( 54 ) past the turbine of the second turbocharger ( 314 ) to the turbine of the first turbocharger ( 312 ).   
     
     
         2 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 1 , in which the first turbocharger is a low pressure turbocharger and the second turbocharger is a high pressure turbocharger. 
     
     
         3 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 2 , further comprising:
 a charge air channel ( 320 ) including the series arrangement of the compressors of the first and second turbochargers and the supercharger which is operable to generate charge air for provision to the intake ports; and   an EGR loop ( 400 ,  500 ,  600 ) operable to circulate a portion of the exhaust gasses to the charge air channel.   
     
     
         4 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 3 , the EGR loop comprising one or more of a low pressure EGR loop ( 600 ), a mid-pressure EGR loop ( 500 ), and a high-pressure EGR loop ( 400 ). 
     
     
         5 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 1 , further comprising:
 a charge air channel ( 320 ) including the series arrangement of the compressors of the first and second turbochargers and the supercharger which is operable to generate charge air for provision to the intake ports; and   an EGR loop ( 400 ,  500 ,  600 ) operable to circulate a portion of the exhaust gasses to the charge air channel.   
     
     
         6 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 5 , the EGR loop comprising one or more of a low pressure EGR loop ( 600 ) upstream of the sequential turbocharger, a mid-pressure EGR loop ( 500 ) between the first and second turbochargers, and a high pressure EGR loop ( 400 ) between the second turbocharger and the supercharger. 
     
     
         7 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 1 , further comprising:
 a recirculation channel ( 313 ) coupling an outlet of the supercharger to an inlet of the supercharger; and,   a supercharger recirculation valve ( 311 ) in the recirculation channel.   
     
     
         8 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 7 , in which the first turbocharger is a low pressure turbocharger and the second turbocharger is a high pressure turbocharger. 
     
     
         9 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 8 , further comprising:
 a charge air channel ( 320 ) including the series arrangement of the compressors of the first and second turbochargers and the supercharger, which is operable to generate charge air for provision to the intake ports ( 56 ); and   an EGR loop ( 400 ,  500 ,  600 ) operable to circulate a portion of the exhaust gasses to the charge air channel.   
     
     
         10 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 9 , the EGR loop comprising one or more of a low pressure EGR loop ( 600 ), a mid-pressure EGR loop ( 500 ), and a high-pressure EGR loop ( 400 ). 
     
     
         11 - 12 . (canceled) 
     
     
         13 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 7 , further comprising a programmed engine control unit (ECU) ( 740 ) coupled to control settings of the compressor bypass valve ( 316   c ), the turbine bypass valve ( 316   t ), and the supercharger recirculation valve ( 311 ) in response to engine speed and intake port pressure. 
     
     
         14 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 13 , in which the first turbocharger is a low pressure turbocharger and the second turbocharger is a high pressure turbocharger. 
     
     
         15 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 14 , further comprising:
 a charge air channel ( 320 ) including the series arrangement of the compressors of the first and second turbochargers and the supercharger which is operable to generate charge air for provision to the intake ports ( 56 ); and   an EGR loop ( 400 ,  500 ,  600 ) operable to circulate a portion of the exhaust gasses to the charge air channel.   
     
     
         16 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 15 , the EGR loop comprising one or more of a low pressure EGR loop ( 600 ), a mid-pressure EGR loop ( 500 ), and a high-pressure EGR loop ( 400 ). 
     
     
         17 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 1 , further comprising:
 a compressor bypass valve ( 330   c ) associated with the first turbocharger ( 312 ) and disposed in parallel with the compressor of the first turbocharger, the compressor bypass valve ( 330   c ) having a closed setting that causes unpressurized fresh air from an air inlet to pass through the compressor of the first turbocharger ( 312 ) and an open setting that directs the unpressurized fresh air past the compressor of the first turbocharger ( 312 ); and,   a turbine bypass valve ( 330   t ) associated with the first turbocharger ( 312 ) and disposed in parallel with the turbine of the first turbocharger ( 312 ), the turbine bypass valve ( 330   t ) having a closed setting that causes exhaust gasses to pass through the turbine of the second turbocharger ( 314 ) and an open setting that directs exhaust gasses past the turbine of the turbine of the first turbocharger ( 312 ).   
     
     
         18 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of  claim 17 , further comprising:
 a charge air channel ( 320 ) including the series arrangement of the compressors of the first and second turbochargers and the supercharger to generate charge air for provision to the intake ports;   an exhaust channel ( 340 ) including the series arrangement of the turbines of the first and second turbochargers to transport exhaust from the exhaust ports ( 54 ); and,   an EGR loop ( 400 ) having an inlet ( 402 ) in the exhaust channel upstream of an inlet of the turbine of the second turbocharger ( 314 ) and having an outlet ( 403 ) in the charge air channel downstream of the compressor of the second turbocharger ( 314 ).   
     
     
         19 . The two-stroke cycle, uniflow-scavenged, opposed-piston engine of any one of  claims 1 ,  5 ,  7 , and  17 , further comprising an exhaust channel ( 340 ) including the series arrangement of the turbines of the first and second turbochargers and one or more after treatment devices ( 342 ) downstream of the turbine of the first turbocharger ( 312 ).