Control of airflow in a uniflow-scavenged, two-stroke cycle, opposed-piston engine during transient operation

Patent metadata

Field	Value
Publication number	US-10161345-B2
Application number	US-201615173478-A
Country	US
Kind code	B2
Filing date	Jun 3, 2016
Priority date	Jan 15, 2016
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

Control of airflow in a uniflow-scavenged, two-stroke cycle, opposed-piston engine during transient operation includes monitoring at least one operating parameter of the engine to recognize a transition to a transient state of engine operation. If a transient state of operation is detected, fuel injection and airflow into to the cylinders of the engine are controlled to optimize combustion and limit emissions. Airflow into cylinders of the engine may be controlled by increasing a scavenging ratio of the engine or by increasing a trapping efficiency of the engine.

First claim

The invention claimed is:

1. A method of controlling a uniflow-scavenged, two-stroke cycle, opposed-piston engine, comprising:
monitoring a transient indication parameter of the engine;
determining, based on the transient indication parameter, whether the engine is in a transient mode of operation;
when the engine is in a transient state of operation:
controlling fuel injection into cylinders of the engine by changing one or more of a common-rail pressure and a fuel injection duration;
controlling unidirectional airflow through the cylinders of the engine by increasing a scavenging ratio of the engine or by increasing a trapping efficiency of the engine;
determining when the transient state of operation ends; and,
transitioning the engine to a steady state of operation:

otherwise, operating the engine in a steady state of operation when the engine is not in a transient state of operation.

2. The method of claim 1 , wherein the transient indication parameter comprises an accelerator position.

3. The method of claim 1 , wherein controlling unidirectional airflow through the cylinders of the engine comprises changing one or more of a supercharger shunt valve setting, a supercharger drive ratio setting, and a turbine vane setting.

4. The method of claim 1 , wherein increasing the scavenging ratio of the engine comprises:
decreasing an exhaust backpressure of the engine; and,
increasing a velocity of unidirectional airflow through the cylinders of the engine.

5. The method of claim 4 , wherein increasing the scavenging ratio of the engine further comprises, after increasing the scavenge ratio for a calibration period, increasing a compressor outlet pressure of the engine.

6. The method of claim 1 , wherein increasing the trapping efficiency of the engine comprises:
decreasing an exhaust backpressure of the engine;
increasing a velocity of unidirectional airflow through the cylinders of the engine; and,
increasing a compressor outlet pressure of the engine.

7. The method of claim 6 , wherein increasing the trapping efficiency of the engine further comprises, after increasing the trapping efficiency for a calibration period, reducing a compressor outlet pressure of the engine.

8. The method of claim 1 , wherein the engine comprises active air handling devices including at least one valve, a supercharger drive, and a variable geometry turbine, and transitioning the engine to the steady state of operation comprises issuing a transient command θ 2 for an actuator of at least one air handling device from an engine control unit (ECU), monitoring an elapse of time from when the transient command θ 2 was issued, and transitioning the engine to the steady state of operation in response to an elapse of a calibration time.

9. The method of claim 8 , wherein the engine comprises a steady state control process in which an airflow parameter comprising one of mass airflow, boost pressure, exhaust and back-pressure in the air handling system is sensed and an error value is determined by subtracting the sensed parameter value from a desired set-point value for the airflow parameter, and transitioning the engine to the steady state of operation comprises transitioning the engine to the steady state of operation when:
an elapse of a calibration time occurs; or,
the error value is less than a calibration value.

10. The method of claim 9 , wherein controlling unidirectional airflow through cylinders of the engine comprises changing one or more of a supercharger shunt valve setting, a supercharger drive ratio setting, and a turbine vane setting.

11. A method of controlling an air handling system of a uniflow-scavenged, two-stroke cycle, opposed-piston engine equipped with at least one cylinder with a bore and axially-spaced exhaust and intake ports that communicate with the bore, 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, the air handling system including a charge air subsystem to provide charge air to the intake port, an exhaust subsystem to receive exhaust gas from the exhaust port, and a supercharger operable to pump charge air in the charge air subsystem, the method comprising:
monitoring a transient indication parameter of the engine;
determining, based on the transient indication parameter, whether the engine is in a transient state of operation;
when the engine is in a transient state of operation:
at an onset of the transient state of operation, opening a backpressure valve in the exhaust subsystem to reduce backpressure resistance to airflow through the air handling system;
at the onset of the transient state of operation, controlling unidirectional airflow through cylinders of the engine by changing a supercharger shunt valve setting to increase a supercharger pressure ratio of the engine or by changing a supercharger drive ratio setting to increase the supercharger pressure ratio of the engine;
determining when the transient state of operation ends; and
then, transitioning the engine to a steady state of operation;

otherwise, operating the engine in the steady state of operation if the engine is not in the transient state of operation.

12. The method of claim 11 , wherein the transient indication parameter comprises an accelerator position or an engine load.

13. The method of claim 11 , wherein the engine further includes a turbocharger with a turbine in the exhaust subsystem and a compressor in the charge air subsystem, upstream of the supercharger, and controlling unidirectional airflow through cylinders of the engine further comprises one or more of decreasing an exhaust backpressure of the air handling system, and increasing a compressor outlet pressure of the air handling system.

14. An airflow control combination for a uniflow-scavenged, two-stroke cycle, opposed-piston engine equipped with at least one cylinder with a bore and axially-spaced exhaust and intake ports that communicate with the bore, 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, and an air handling system including a charge air subsystem to provide charge air to the intake port, an exhaust subsystem to receive exhaust gas from the exhaust port, a supercharger operable to pump charge air in the charge air subsystem, and a command-controlled shunt valve which promotes a charge air pressure ratio across the supercharger, the airflow control combination comprising:
a sensor that senses one of engine acceleration and engine load of the engine;
a sensor that detects charge air pressure at the intake of the supercharger;
a sensor that detects charge air pressure at the outlet of the supercharger, and,
a control unit programmed to:
determine an occurrence of a torque demand for the engine, the torque demand having an intensity based on an intensity of a rate of change of engine acceleration or engine load with respect to a transient intensity threshold value;
produce a transient command for the shunt valve to increase a charge air pressure ratio across the supercharger when the intensity of the torque demand exceeds the transient intensity threshold; and
produce a steady state command to control the charge air pressure ratio across the supercharger to a desired setpoint when the intensity of the torque demand falls below the transient intensity threshold.

15. The airflow control combination of claim 14 , further comprising a backpressure valve in the exhaust subsystem to control a backpressure in the air handling system, in which the

Assignees

• Achates Power Inc

Inventors

• Sharma Arunandan
• Nagar Nishit
• Naik Suramya D
• Schum Daniel

Classifications

• F02D2200/1002

  Output torque · CPC title

• F02B75/02

  Engines characterised by their cycles, e.g. six-stroke · CPC title

• F02D2200/602

  Pedal position · CPC title

• F02D2200/101

  Engine speed · CPC title

• F02M35/1038

  for temperature or pressure · CPC title