Abstract: Various embodiments of the present invention are directed toward a linear free piston combustion engine with indirect work extraction via gas linkage, comprising: a cylinder with two opposed free pistons disposed therein that form a combustion section in a center of the cylinder, each free piston comprising a front face facing the combustion section and a back face facing the opposite direction; two opposed extractor pistons disposed in their own cylinders at opposite ends of the free piston cylinder, each extractor piston comprising a front face facing the combustion section and a back face facing the opposite direction; and two gas linkages, each gas linkage comprising a volume sealed between the back face of a free piston and the front face of an extractor piston; wherein each extractor piston is connected to a rotary electromagnetic machine.

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: An element is provided to maintain a clearance gap between a piston and a cylinder wall. In some embodiments, an element is included that is capable of spatial change. In some embodiments, the element is a component such as a clearance ring, a surface bearing, or a segment of a clearance ring or surface bearing. A clearance gap may be maintained by inward and outward motion of the component with respect to a piston assembly and a cylinder wall, where the motion is determined by a balance of forces acting on the component. In some embodiments, an inward force generated by an external gas pressure source is balanced by an outward preload force generated by, for example, a pneumatic piston. In some embodiments, a clearance gap is maintained based on in part on the ratio of inner to outer surface areas of a clearance ring.

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.

Abstract: Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.

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.

Abstract: Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.

Abstract: A piston engine may include a piston assembly, which may include a piston having a self-centering feature. The piston assembly may be configured to translate in a bore of the cylinder, and contact a combustion section and/or gas driver section. The self-centering feature may use a flow of blow-by gas in a clearance gap to provide a self-centering force on the piston assembly. The self-centering feature may include one or more slotted pockets, a step, a tapered portion, any other suitable feature, or a combination thereof. Optionally, a piston assembly may include a feature that aids in self-centering such as, for example, a labyrinth seal.

Abstract: A multiphase electromagnetic machine may be controlled by controlling currents in one or more phases of the multiphase electromagnetic machine. A control system may be used to determine how much current to deliver to, or extract from, each phase. The control system may use an objective function, subject to one or more constraints, to determine the current. The control system may use position information to determine the objective function, constraints, or both.

Abstract: A multiphase electromagnetic machine may be controlled by controlling currents in one or more phases of the multiphase electromagnetic machine. A control system may be used to determine how much current to deliver to, or extract from, each phase. The control system may use an objective function, subject to one or more constraints, to determine the current. The control system may use position information to determine the objective function, constraints, or both.

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 piston assembly, which may include a piston having a self-centering feature. The piston assembly may be configured to translate in a bore of the cylinder, and contact a combustion section and/or gas driver section. The self-centering feature may use a flow of blow-by gas in a clearance gap to provide a self-centering force on the piston assembly. The self-centering feature may include one or more slotted pockets, a step, a tapered portion, any other suitable feature, or a combination thereof. Optionally, a piston assembly may include a feature that aids in self-centering such as, for example, a labyrinth seal.

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.

Abstract: Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a hollow back section comprising a gas spring that directly provides at least some compression work during a compression stroke of the engine; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke; wherein the engine includes a

Abstract: Various embodiments of the present invention are directed toward a two-piston linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly; a pair of driver sections, each driver section comprising a compression mechanism that directly provides at least some compression work during a compression stroke of the engine; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke, wherein each linear electromagnetic machine is located distal to an end of the cylinder; wherein the engine

Abstract: Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.

Abstract: A multiphase electromagnetic machine may be controlled by controlling currents in one or more phases of the multiphase electromagnetic machine. A control system may be used to determine how much current to deliver to, or extract from, each phase. The control system may use an objective function, subject to one or more constraints, to determine the current. The control system may use position information to determine the objective function, constraints, or both.

Abstract: Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.