Rotary engine

A rotary engine, comprising:

• a cylinder having a gas inlet and a gas outlet;
• two rotors which are mounted inside the cylinder and rotatable freely, the rotors comprising a first rotor and a second rotor;
• pistons fixed on the rotors, at least one pair of pistons being fixed to the first rotor, and at least one pair of pistons being fixed to the second rotor;
• an ignition device provided on an inner wall of the cylinder;
• a planetary conical gear differential located outside the cylinder, the planetary conical gear differential comprising a first sun gear and a second sun gear, wherein the first rotor and the second rotor are superposed concentrically, the first rotor is connected to the first sun gear through a spindle, the second rotor is connected to the second sun gear through a hollow shaft, the spindle passes through the hollow shaft, the first rotor and the second rotor are connected to the planetary conical gear differential on a same side of the planetary conical gear differential, the pistons are each provided with an independent combustion chamber thereon, and an opening of the combustion chamber faces the inner wall of the cylinder.