A downhole power generation includes a power generation module for providing power to a load. A turbine is driven by flow of a downhole fluid to rotate. A generator is coupled with the turbine for converting rotational energy from the turbine to electrical energy, and an AC-DC rectifier is coupled with the generator for converting an alternating voltage from the generator to a direct voltage. A power conversion circuit couples the AC-DC rectifier with the load. The power conversion circuit is configured for providing a first power to the load when the load is in a working mode and providing a second power to the load when the load is in a non-working mode. The second power is less than the first power. A downhole power generation method is also disclosed.

Two-stroke engine includes a cylinder having a peripheral wall defining an interior space, a crankshaft coupled to a piston movable in the cylinder and having a power stroke in which air/fuel in the interior space is ignited and the crankshaft is rotated and a compression stroke, two intake conduits leading to the cylinder, and intake valves in the intake conduits that regulate air flow into the interior space. An exhaust conduit leads from an opening in the peripheral wall between lowermost and uppermost positions of the piston. An exhaust valve is in the exhaust conduit. In an exhaust-intake stroke after the power stroke when the piston has moved such that its upper surface is below the opening, the outlet valve opens, and air is inlet into the interior space through the intake valve(s) and forces combustion products to exhaust the interior space into the exhaust conduit.

Two-stroke engine includes a cylinder having a peripheral wall defining an interior space, a crankshaft coupled to a piston movable in the cylinder and having a power stroke in which air/fuel in the interior space is ignited and the crankshaft is rotated and a compression stroke, two intake conduits leading to the cylinder, and intake valves in the intake conduits that regulate air flow into the interior space. An exhaust conduit leads from an opening in the peripheral wall between lowermost and uppermost positions of the piston. An exhaust valve is in the exhaust conduit. In an exhaust-intake stroke after the power stroke when the piston has moved such that its upper surface is below the opening, the outlet valve opens, and air is inlet into the interior space through the intake valve(s) and forces combustion products to exhaust the interior space into the exhaust conduit.

Methods and systems for unsticking a stuck gaspath actuator are disclosed. In one embodiment, an engine operating method includes adjusting exhaust valve timing of one or more cylinders of an engine in response to an indication that a gaspath actuator is stuck in position. In this way, pressure waves in an exhaust manifold and/or an intake manifold may be generated, which may act to unstick the gaspath actuator.

Methods and systems for unsticking a stuck gaspath actuator are disclosed. In one embodiment, an engine operating method includes adjusting exhaust valve timing of one or more cylinders of an engine in response to an indication that a gaspath actuator is stuck in position. In this way, pressure waves in an exhaust manifold and/or an intake manifold may be generated, which may act to unstick the gaspath actuator.

A valve arrangement for supplying air to a combustion chamber of an internal combustion engine includes a first valve, the first valve including a first valve head, a first valve stem assembly and an internal cavity, which is at least partly located in the first valve stem assembly, and a second valve partly arranged within the internal cavity of the first valve, the second valve including a second valve head and a second valve stem assembly, and being movable within the internal cavity between an upper, closed position and a lower, open position, wherein a junction seal extends over a junction between the first valve stem assembly and the second valve stem assembly when the second valve is in the closed position. A leakage preventing arrangement is arranged to hinder leakage of liquid from the outside of the junction seal from reaching in between the first valve stem assembly and the second salve stem assembly.

A valve arrangement for supplying air to a combustion chamber of an internal combustion engine includes a first valve, the first valve including a first valve head, a first valve stem assembly and an internal cavity, which is at least partly located in the first valve stem assembly, and a second valve partly arranged within the internal cavity of the first valve, the second valve including a second valve head and a second valve stem assembly, and being movable within the internal cavity between an upper, closed position and a lower, open position, wherein a junction seal extends over a junction between the first valve stem assembly and the second valve stem assembly when the second valve is in the closed position. A leakage preventing arrangement is arranged to hinder leakage of liquid from the outside of the junction seal from reaching in between the first valve stem assembly and the second salve stem assembly.

A gas feeding arrangement for feeding gas from an internal combustion engine cylinder chamber to a gas tank includes a feeding conduit assembly and a dedicated feeding valve. The feeding valve is adapted to assume an open condition in which it provides for gas transport in a direction from the cylinder chamber towards the gas tank, via the feeding conduit assembly. The gas feeding arrangement includes a one-way valve adapted to prevent gas transport from the gas tank to the cylinder chamber, via the feeding conduit assembly.

A gas feeding arrangement for feeding gas from an internal combustion engine cylinder chamber to a gas tank includes a feeding conduit assembly and a dedicated feeding valve. The feeding valve is adapted to assume an open condition in which it provides for gas transport in a direction from the cylinder chamber towards the gas tank, via the feeding conduit assembly. The gas feeding arrangement includes a one-way valve adapted to prevent gas transport from the gas tank to the cylinder chamber, via the feeding conduit assembly.

An engine system may include an engine including a plurality of combustion chambers generating driving torque by combustion of fuel, an intake line through which outside air supplied to the combustion chamber flows, an exhaust line for exhausting the exhaust gas from the combustion chamber to the outside, a turbocharger including a compressor mounted in the intake line and a turbine mounted in the exhaust line, an air supply passage through which a portion of the outside air branched from the intake line and supplied to the combustion chamber, an air supply nozzle connected to the air supply passage and supplying the part of the outside air to the combustion chamber, an air supply pump provided in the air supply passage and providing an injection pressure to the part of the outside air injected into the combustion chamber, and a controller for controlling the air supply nozzle and the air supply pump.