Methods and systems for managing a clearance gap in a piston engine
A piston engine may include a clearance gap between a piston assembly and a cylinder. The piston may be configured to translate in a bore of the cylinder. The clearance gap between the piston assembly and the bore may be actively or passively controlled. A control system may provide one or more adjustments based on, for example, a detected temperature, pressure, flow rate, work metric, and/or other indicator. The adjustments may include, for example, adjusting a cylinder liner, adjusting a flow through a bearing element, adjusting a coolant flow, adjusting a heat pipe property, and/or other adjustments. One or more auxiliary systems may be used to provide the adjustments.
1. A method of controlling a clearance gap between a piston assembly and a cylinder of a free-piston engine, the method comprising:
detecting at least one indicator of the clearance gap;
determining a control response based at least in part on the indicator;
generating a control signal based at least in part on the control response; and
causing the clearance gap to be adjusted based at least in part on the control signal, wherein:
the piston assembly comprises at least one feature or component that interacts with blow-by gas from a compression section of the free-piston engine to aid in centering the piston assembly, wherein the at least one feature or component is selected from the group consisting of a step, a slotted pocket, a labyrinth, and any combination thereof.
2. The method of claim 1 , wherein the at least one indicator comprises a temperature.
3. The method of claim 1 , wherein the at least one indicator comprises a thickness of the clearance gap.
4. The method of claim 1 , wherein the at least one indicator comprises a pressure.
5. The method of claim 1 , wherein the at least one indicator comprises a gas flow rate.
6. The method of claim 1 , wherein the at least one indicator comprises a work interaction of the free-piston engine.
7. The method of claim 1 , wherein the at least one indicator comprises a velocity.
8. The method of claim 1 , wherein the at least one indicator comprises an acceleration.
9. The method of claim 1 , wherein causing the clearance gap to be adjusted comprises causing a pressure to be adjusted to a cylinder liner positioned coaxial in the cylinder.
10. The method of claim 1 , wherein causing the clearance gap to be adjusted comprises causing a flow of a bearing fluid through a bearing element of the free-piston engine to be adjusted.
11. The method of claim 1 , wherein causing the clearance gap to be adjusted comprises providing a coolant to at least one of the piston assembly and the cylinder to control a temperature of the free-piston engine.
12. The method of claim 1 , wherein causing the clearance gap to be adjusted comprises causing a property of a heat pipe of the free-piston engine to be adjusted.
13. The method of claim 1 , wherein causing the clearance gap to be adjusted comprises causing a force applied to a piston assembly of the free-piston engine to be adjusted.
14. The method of claim 1 , wherein causing the clearance gap to be adjusted comprises causing a pressure of a gas flow to the inside of the cylinder to be adjusted.
15. A system configured to control a clearance gap between a piston assembly and a cylinder of a free-piston engine, the system comprising:
at least one sensor configured to detect at least one indicator of the clearance gap;
processing equipment configured to determine a control response based at least in part on the at least one indicator; and
a control interface configured to provide a control signal based at least in part on the control response, wherein:
the piston assembly comprises at least one feature or component that interacts with blow-by gas from a compression section of the free-piston engine to aid in centering the piston assembly, wherein the at least one feature or component is selected from the group consisting of a step, a slotted pocket, a labyrinth, and any combination thereof.
16. The system of claim 15 , wherein the at least one sensor is configured to detect a temperature.
17. The system of claim 15 , wherein the at least one sensor is configured to detect a thickness of the clearance gap.
18. The system of claim 15 , wherein the at least one sensor is configured to detect a pressure.
19. The system of claim 15 , wherein the at least one sensor is configured to detect a fluid flow rate.
20. The system of claim 15 , wherein the at least one sensor is configured to detect a work output of the free-piston engine or work input to the free-piston engine.
21. The system of claim 15 , wherein the at least one sensor is configured to detect a velocity.
22. The system of claim 15 , further comprising at least one auxiliary system configured to adjust the clearance gap based at least in part on the control signal.
23. The system of claim 22 , wherein the at least one auxiliary system is configured to adjust the clearance gap by adjusting a pressure to the outside of a cylinder liner positioned coaxial in the cylinder to reduce or increase the clearance gap in response to the control signal.
24. The system of claim 22 , wherein the at least one auxiliary system is configured to adjust the clearance gap by increasing or decreasing a gas flow through a bearing element of the free-piston engine in response to the control signal.
25. The system of claim 22 , wherein the at least one auxiliary system is configured to adjust the clearance gap by providing a coolant to at least one of the piston assembly and the cylinder to control a temperature of the free-piston engine in response to the control signal.
26. The system of claim 22 , wherein the at least one auxiliary system is configured to adjust the clearance gap by adjusting a property of a heat pipe of the free-piston engine in response to the control signal.
27. The system of claim 22 , wherein the at least one auxiliary system is configured to adjust a force applied to a piston assembly of the free-piston engine in response to the control signal.
28. The system of claim 22 , wherein the at least one auxiliary system is configured to adjust a pressure of a gas flow to the inside of the cylinder in response to the control signal.