System and method for air handling control in opposed-piston engines with uniflow scavenging

1. A uniflow-scavenged, opposed-piston engine, comprising:

at least one cylinder with a bore and axially-spaced exhaust and intake ports, and a pair of pistons disposed in opposition in the bore and operative to open and close the exhaust and intake ports during operation of the engine;

a charge air channel to provide charge air to an intake port;

an exhaust channel to receive exhaust gas from an exhaust port;

a supercharger operable to pump charge air in the charge air channel;

an exhaust gas recirculation (EGR) channel having an input coupled to the exhaust channel and an output coupled to the charge air channel; and,

a control mechanization operable to:

determine a plurality of air handling setpoints for trapped conditions in the at least one cylinder;

determine a plurality of external operating conditions of the air handling system; and,

adjust, based on the external operating conditions, the plurality of air handling setpoints.

2. The opposed-piston engine of claim 1 , in which the control mechanization is operable to adjust a first setpoint for intake pressure in the charge air channel, a second setpoint for EGR flow in the EGR channel, and a third setpoint for fresh air flow into the charge air channel.

3. The opposed-piston engine of claim 1 , in which the control mechanization is further operable to correct the air handling setpoints in response to changed engine operating conditions.

4. The opposed-piston engine of claim 1 , in which the plurality of trapped conditions include trapped lambda, trapped burned gas fraction, and trapped temperature.

5. The opposed-piston engine of claim 4 , in which the control mechanization is operable to adjust a first setpoint for intake pressure in the charge air channel, a second setpoint for EGR flow in the EGR channel, and a third setpoint for fresh air flow into the charge air channel.

6. The opposed-piston engine of claim 5 , in which the control mechanization is operable to:

adjust intake pressure in the charge air channel by one of changing a speed of the supercharger and operating a first valve to shunt charge air flow from an output to an input of the supercharger;

adjust EGR flow in the EGR channel by operating a second valve to increase or decrease exhaust gas flow through the EGR channel; and,

adjust fresh air flow into the charge air channel by adjusting backpressure in the exhaust channel.

7. The opposed-piston engine of claim 6 , in which the control mechanization is operable to adjust backpressure in the exhaust channel by one of operating a third valve in the exhaust channel or changing a turbine geometry in the exhaust channel.

8. The opposed-piston engine of claim 5 , in which the control mechanization is further operable to correct the first, second, and third setpoints in response to changed engine operating conditions.

9. The opposed-piston engine of claim 8 , in which the control mechanization is operable to:

adjust intake pressure in the charge air channel by one of changing a speed of the supercharger and operating a first valve to shunt charge air flow from an output to an input of the supercharger;

adjust EGR flow in the EGR channel by operating a second valve to increase or decrease exhaust gas flow through the EGR channel; and,

adjust fresh air flow into the charge air channel by adjusting backpressure in the exhaust channel.

10. The opposed-piston engine of claim 9 , in which the control mechanization is operable to adjust backpressure in the exhaust channel by one of operating a third valve in the exhaust channel or changing a turbine geometry in the exhaust channel.

11. An opposed-piston engine equipped with an air handling system, comprising:

at least one cylinder with a bore, axially-spaced exhaust and intake ports, and a pair of pistons disposed in opposition in the bore and operative to open and close the exhaust and intake ports during operation of the engine;

a charge air channel to provide charge air to an intake port;

an exhaust channel to receive exhaust gas from an exhaust port;

a supercharger operable to pump charge air in the charge air channel;

an exhaust gas recirculation (EGR) channel having an input coupled to the exhaust channel and an output coupled to the charge air channel; and,

a control mechanization operable to:

determine a plurality of air handling setpoints for trapped conditions in the at least one cylinder;

determine a plurality of external operating conditions of the air handling system;

change the setpoints in response to the external operating conditions; and

adjust, based on the changed setpoints, an intake manifold pressure in the charge air channel, an EGR flow in the EGR channel, and a backpressure in the exhaust channel.

12. The opposed-piston engine of claim 11 , in which the control mechanization is operable to determine a first setpoint for the intake manifold pressure, a second setpoint for the EGR flow, and a third setpoint for the backpressure.

13. The opposed-piston engine of claim 12 , in which the trapped conditions include trapped lambda, trapped burned gas fraction, and trapped temperature.

14. The opposed-piston engine of claim 12 , in which the control mechanization is further operable to correct the setpoints in response to changed engine operating conditions.

15. A method of operating an opposed-piston engine with an air handling system, comprising:

generating exhaust gas in at least one ported cylinder of the engine;

transporting exhaust gas from an exhaust port of the at least one ported cylinder through an exhaust channel;

recirculating a portion of the exhaust gas from the exhaust channel through an EGR channel;

pressurizing fresh air;

mixing recirculated exhaust gas from the EGR channel with the pressurized fresh air to form charge air;

pressurizing the charge air with a supercharger;

providing the pressurized charge air to an intake port of the at least one ported cylinder;

determining a plurality of air handling setpoints for trapped conditions in the at least one ported cylinder;

determining a plurality of external operating conditions of the air handling system; and, adjusting, based on the external operating conditions, the plurality of air handling setpoints.

16. The method of claim 15 , in which the plurality of trapped conditions include trapped lambda, trapped burned gas fraction, and trapped temperature.

17. The method of claim 16 , in which adjusting the plurality of air handling setpoints include adjusting a first setpoint for intake pressure in the charge air channel, adjusting a second setpoint for EGR flow in the EGR channel, and adjusting a third setpoint for fresh air flow into the charge air channel.

18. The method of claim 17 , in which:

in response to adjusting a first setpoint, adjusting intake pressure in the charge air channel by one of changing a speed of the supercharger and operating a first valve to shunt charge air flow from an output to an input of the supercharger;

in response to adjusting a second setpoint, adjusting EGR flow in the EGR channel by operating a second valve to increase or decrease exhaust gas flow through the EGR channel; and,

in response to adjusting a third setpoint, adjusting fresh air flow into the charge air channel by operating a backpressure in the exhaust channel.

19. A method of operating an opposed-piston engine equipped with one or more ported cylinders and a supercharger, comprising:

generating exhaust gas in at least one ported cylinder of the engine;

transporting exhaust gas from an exhaust port of the at least one ported cylinder through an exhaust channel;

recirculating a portion of the exhaust gas from the exhaust channel through an EGR channel;

pressurizing fresh air in a charge air channel;

mixing recirculated exhaust gas from the EGR channel with the pressurized fresh air to form charge air;

pressurizing the charge air with a supercharger;

providing the pressurized charge air to an intake port of the at least one ported cylinder;

determining a plurality of air handling setpoints for trapped conditions in the at least one cylinder;

determining a plurality of external air handling conditions;

changing the setpoints in response to the external air handling conditions; and

adjusting, based on the changed setpoints, an intake manifold pressure in the charge air channel, an EGR flow in the EGR channel, and a backpressure in the exhaust channel.

20. The method of claim 19 , in which determining a plurality of air handling setpoints includes determining a first setpoint for the intake manifold pressure, determining a second setpoint for the EGR flow, and determining a third setpoint for the backpressure.

21. The method of claim 20 , in which the trapped conditions include trapped lambda, trapped burned gas fraction, and trapped temperature.

22. The method of claim 19 , in which determining the plurality of air handling setpoints includes correcting the setpoints in response to changed engine operating conditions.