Exhaust management strategies for opposed-piston, two-stroke engines

Abstract

Exhaust temperature management strategies for an opposed-piston, two-stroke engine with EGR are based on control of a ratio of the mass of fresh air and external EGR delivered to a cylinder to the mass of the trapped charge (density of the delivered charge multiplied by the trapped volume at port closing).

We claim: 
     
         1 . A two-stroke cycle internal combustion engine including at least one cylinder with exhaust and intake ports, two pistons disposed in a bore of the cylinder with end surfaces in opposition to each other, a charge air channel to provide charge air to at least one intake port of the engine, and an exhaust channel to receive exhaust from at least one exhaust port of the engine, in which an exhaust gas recirculation (EGR) loop has a loop input coupled to the exhaust channel and a loop output coupled to the charge air channel, a supercharger is operable to pump charge air in the charge air channel, a backpressure device is operable to control backpressure in the exhaust channel, and a control mechanization is operable to increase a trapped temperature in the cylinder by controlling one or more of the supercharger, the EGR loop, and the backpressure device during a cold start condition of the engine or a low-load condition of the engine. 
     
     
         2 . The two-stroke cycle internal combustion engine of  claim 1 , in which the charge air channel includes at least one charge air cooler, wherein the loop output is coupled in series with the at least one charge air cooler. 
     
     
         3 . The two-stroke cycle internal combustion engine of  claim 1 , in which the EGR loop includes a variable valve and the control mechanization is operable to control a setting of the valve in response to a trapped temperature of the cylinder. 
     
     
         4 . The two-stroke cycle internal combustion engine of  claim 1 , in which the supercharger is one of a single-speed supercharger, a multispeed supercharger, and a variable-speed supercharger and the control mechanization is operable to control the speed of the supercharger in response to a trapped temperature of the cylinder. 
     
     
         5 . The two-stroke cycle internal combustion engine of  claim 1 , in which the backpressure device includes a variable valve and the control mechanization is operable to control a setting of the valve in response to a trapped temperature of the cylinder. 
     
     
         6 . The two-stroke cycle internal combustion engine of  claim 1 , in which the backpressure device includes one of a variable valve, a variable nozzle turbo mechanism, a multi-stage turbo mechanism, and a compound turbo mechanism, and the control mechanization is operable to control a setting of the backpressure device in response to a trapped temperature of the cylinder. 
     
     
         7 . The two-stroke cycle internal combustion engine of  claim 1 , further including a turbo-charger with a charge air output coupled to the charge air channel and a turbine input coupled to the exhaust channel, and a back pressure valve in series with the turbine output, in which the backpressure valve is settable to a state causing a back pressure acting upon the exhaust channel. 
     
     
         8 . The two-stroke cycle internal combustion engine of  claim 7 , in which the turbo-charger includes a variable-geometry turbine. 
     
     
         9 . The two-stroke cycle internal combustion engine of  claim 1 , further including a turbo-charger with a charge air output coupled to the charge air channel, a turbine input coupled to the exhaust channel, a turbine output coupled to an exhaust output, and a back pressure valve in series between the turbine output and the exhaust output, in which the backpressure valve is settable to a state causing a back pressure acting upon the exhaust channel. 
     
     
         10 . The two-stroke cycle internal combustion engine of  claim 9 , in which the turbo-charger includes a variable-geometry turbine. 
     
     
         11 . The two-stroke cycle internal combustion engine of  claim 1 , in which a pair of pistons is disposed in a bore of the at least one cylinder with end surfaces opposing. 
     
     
         12 . The two-stroke cycle internal combustion engine of  claim 1 , further including a recirculation loop having an inlet connected to the charge air channel downstream of the supercharger, an outlet connected to the charge air channel upstream of the supercharger, and a variable valve between the inlet and the outlet, and, an air cooler in series with the variable valve. 
     
     
         13 . The two-stroke cycle internal combustion engine of  claim 1 , in which the EGR loop is one of a high-pressure EGR loop and a low-pressure EGR loop.