Dual fuel engine having selective compression reduction

1. An engine system, comprising:

an engine block at least partially defining a cylinder bore;

a cylinder liner disposed within the cylinder bore;

at least one air intake port radially formed within the cylinder liner;

a piston slidingly disposed within the cylinder liner and configured to open and close the at least one air intake port;

a cylinder head configured to close off an end of the cylinder liner to form a combustion chamber;

at least one exhaust valve disposed within the cylinder head;

a valve actuation system configured to cyclically move the at least one exhaust valve between open and closed positions; and

a variable timing device configured to selectively interrupt cyclical movement of the at least one exhaust valve to change a compression ratio of the engine system.

2. The engine system of claim 1 , further including:

a gaseous fuel injector configured to inject gaseous fuel into the combustion chamber; and

a liquid fuel injector configured to inject liquid fuel into the combustion chamber.

3. The engine system of claim 2 , wherein:

the gaseous fuel injector is configured to inject gaseous fuel radially into the combustion chamber through the at least one air intake port; and

the liquid fuel injector is configured to inject liquid fuel axially into the combustion chamber.

4. The engine system of claim 2 , wherein the variable timing device is configured to change a compression ratio of the engine system based on a mixture of fuels being injected into the combustion chamber.

5. The engine system of claim 4 , wherein the variable timing device is configured to cause the at least one exhaust valve to open at about 100° after TDC of the piston and to close at about 240° after TDC of the piston when only liquid fuel is being injected.

6. The engine system of claim 5 , wherein the variable timing device is configured to cause the at least one exhaust valve to open at about 80° after TDC of the piston and to close at about 260° after top dead center of the piston when only gaseous fuel is being injected.

7. The engine system of claim 6 , wherein the variable timing device is configured to transition from a first timing associated with gaseous fuel only operation to a second timing associated with liquid fuel only operation at a rate of about 2°/cycle.

8. The engine system of claim 7 , wherein the piston moves through two strokes to complete an entire cycle.

9. The engine system of claim 3 , wherein the variable timing device is configured to cause the at least one exhaust valve to open at about 80° after TDC of the piston and to close at about 260° after top dead center of the piston when only gaseous fuel is being injected.

10. The engine system of claim 3 , wherein the variable timing device is configured to cause a compression ratio of about 12:1 when only gaseous fuel is being injected.

11. The engine system of claim 10 , wherein the variable timing device is configured to cause a compression ratio of about 18:1 when only liquid fuel is being injected.

12. The engine system of claim 3 , wherein the variable timing device is configured to cause a compression ratio of about 18:1 when only liquid fuel is being injected.

13. The engine system of claim 1 , wherein the variable timing device includes a rocker arm operatively associated with the at least one exhaust valve, and a hydraulic piston configured to selectively lock pivoting of opposing ends of the rocker arm.

14. The engine system of claim 1 , wherein:

the engine block defines a plurality of cylinder bores;

the cylinder head is a first cylinder head associated with a first of the plurality of cylinder bores;

the engine system further includes a second cylinder bore associated with a second of the plurality of cylinder bores;

the at least one exhaust valve includes at least a first exhaust valve associated with the first cylinder head, and at least a second exhaust valve associated with the second cylinder head;

the variable timing device is a first variable timing device associated with the at least a first exhaust valve;

the engine system further includes a second variable timing device associated with the at least a second exhaust valve, and the second variable timing device is configured to selectively interrupt cyclical movement of the at least a second exhaust valve at a different timing than the first variable timing device interrupts cyclical movement of the at least a first exhaust valve.

15. An engine system, comprising:

an engine block at least partially defining a cylinder bore;

a cylinder liner disposed within the cylinder bore;

a plurality of air intake ports radially formed within the cylinder liner;

a piston slidingly disposed within the cylinder liner and configured to open and close the plurality of air intake ports;

a cylinder head configured to close off an end of the cylinder liner to form a combustion chamber;

a gaseous fuel injector configured to radially inject gaseous fuel into the combustion chamber;

a liquid fuel injector configured to axially inject liquid fuel into the combustion chamber;

at least one exhaust valve disposed within the cylinder head;

a rocker arm configured to open and close the at least one exhaust valve;

a valve actuation system configured to cyclically move the rocker arm; and

a lost motion device associated with the rocker arm and configured to selectively interrupt cyclical movement of the at least one exhaust valve to change a compression ratio of the engine system from about 12:1 to about 18:1 based on a mixture of liquid and gaseous fuels being injected into the combustion chamber.

16. The engine system of claim 15 , wherein:

the lost motion device is configured to cause the at least one exhaust valve to open at about 100° after TDC of the piston and to close at about 240° after TDC of the piston when only gaseous fuel is being injected;

the lost motion device is configured to cause the at least one exhaust valve to open at about 80° after TDC of the piston and to close at about 260° after top dead center of the piston when only liquid fuel is being injected; and

the lost motion device is configured to transition from a first timing associated with gaseous fuel only operation to a second timing associated with liquid fuel only timing at a rate of about 2°/cycle.

17. A method of operating an engine;

directing air radially into a combustion chamber;

selectively injecting gaseous fuel into the combustion chamber;

selectively injecting liquid fuel into the combustion chamber;

igniting a mixture of gaseous and liquid fuels within the combustion chamber to move a piston and produce mechanical power;

cyclically moving an exhaust valve to relieve charge from the combustion chamber; and

selectively interrupting cyclical movement of the exhaust valve to adjust a compression ratio of the engine based on the mixture of gaseous and liquid fuels.

18. The method of claim 17 , wherein cyclically moving the exhaust valve includes opening the exhaust valve at about 100° after TDC of the piston and closing the exhaust valve at about 240° after TDC of the piston when only liquid fuel is being injected.

19. The method of claim 18 , wherein selectively interrupting the cyclical movement of the exhaust valve includes opening the exhaust valve at about 800° after TDC of the piston and closing the exhaust valve at about 260° after TDC of the piston when only gaseous fuel is being injected.

20. The method of claim 19 , further including transitioning from a first timing associated with gaseous fuel only operation to a second timing associated with liquid fuel only operation at a rate of about 2°/cycle.