Abstract: A piston engine may include a heat pipe capable of transferring heat away from a portion of the piston engine such as a combustion section. The heat pipe may be included as part of a piston assembly, a cylinder, or both. The heat pipe may be filled with a suitable heat pipe fluid that may undergo a phase change such as, for example, water, ethanol, ammonia, sodium, other fluids or combinations thereof. Boiling and condensing of the fluid within the heat pipe may utilize the latent heat of the fluid during heat transfer. Multiple heat pipes may be used in some instances.

Abstract: 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.

Abstract: A piston engine may include a non-contact bearing between a piston assembly and a cylinder. The piston may be configured to translate in a bore of the cylinder, and a non-contact bearing may be included in a clearance gap between the piston assembly and the bore. A bearing fluid may be supplied to the clearance gap via the piston assembly and/or cylinder to create the non-contact bearing. A bearing element may be used to direct or otherwise manage the flow of bearing fluid in the clearance gap. The bearing element may include one or more holes, porous portions, and/or passages to direct the bearing fluid to the clearance gap.