In one embodiment, a power generation system includes a pulse detonation engine including a combustion chamber, a linear power generator including a working chamber, and a nozzle positioned between the combustion chamber and the working chamber that expands exhaust gas expelled from the combustion chamber, wherein the nozzle increases thermodynamic efficiency of the system.

A variable intake system includes a pair of surge tanks connected in a communicating manner to a main intake pipe through a low speed communication pipe and a high speed communication pipe, a middle speed communication pipe for connecting the pair of surge tanks, and a noise reducing member integrally provided at the middle speed communication pipe to reduce noise.

An air intake apparatus includes an air intake apparatus body including a surge tank, a valve body rotatably attached to the surge tank and configured to rotate between an open position and a closed position to open and close a fluid passage formed at a partition wall dividing an inside of the surge tank into two parts, the valve body being out of contact with the partition wall at the open position and being in contact with the partition wall at the closed position, the air intake apparatus body being formed by a first member to which the valve body is attached and a second member joined to each other, and the first member including a jig-receiving portion arranged in a vicinity of the fluid passage and configured to receive a jig holding the first member when the first member and the second member are being joined to each other.

In one embodiment, a power generation system includes a pulse detonation engine including a combustion chamber, a linear power generator including a working chamber, and a nozzle positioned between the combustion chamber and the working chamber that expands exhaust gas expelled from the combustion chamber, wherein the nozzle increases thermodynamic efficiency of the system.