The characteristic of the rotor engine is that while the center of the triangular rotor revolves around the center of the output shaft, the triangular rotor itself rotates around its center. When the triangular rotor rotates, the internal gear ring centered on the center of the triangular rotor meshes with the gear centered on the center of the output shaft. The gear is fixed on the cylinder and does not rotate. The above-mentioned kinematic relationship makes the trajectory of the vertex of the triangular rotor (that is, the shape of the cylinder wall) resemble an "8" shape. The triangular rotor divides the cylinder into three independent spaces. Each of the three spaces completes the intake, compression, work, and exhaust. The triangular rotor rotates once and the engine ignites three times. Due to the above motion relationship, the rotation speed of the output shaft is three times the rotation speed of the rotor, which is completely different from the 1: 1 motion relationship between the piston and the crankshaft of the reciprocating engine.
The rotor of a rotor engine works three times per revolution. Compared with a normal four-stroke engine, it only works once every two revolutions. It has the advantage of high horsepower volume ratio (smaller engine volume can output more power). In addition, due to the axial operating characteristics of the rotor engine, it does not require precise crankshaft balance to achieve higher operating speeds. The entire engine has only two rotating parts. Compared with a general four-stroke engine with more than twenty moving parts such as intake and exhaust valves, the structure is greatly simplified, and the possibility of failure is greatly reduced. In addition to the above advantages, the advantages of the rotor engine also include smaller size, light weight, low center of gravity, and low vibration.
The displacement of a rotor engine is usually expressed in terms of unit working volume and number of rotors. For example, for a 13B twin-rotor engine, the displacement is "654cc × 2".
The unit working volume refers to the difference between the maximum volume and the minimum volume of the working chamber; and the compression ratio is the ratio of the maximum volume to the minimum volume. The same definition is used on reciprocating engines.
Rotary engine working volume changes and comparison with four-cycle reciprocating engines. Although the volume of the working chamber fluctuates steadily in both engines, there are significant differences between the two. The first is the rotation angle of each process: the reciprocating engine rotates 180 degrees, while the rotor engine rotates 270 degrees, which is 1.5 times the reciprocating engine. In other words, in a reciprocating engine, the crankshaft (output shaft) rotates two revolutions (720 degrees) in four working processes; whereas in a rotor engine, the eccentric shaft rotates three revolutions (1080 degrees) and the rotor makes one revolution. In this way, the rotor engine can obtain a longer process time, and form a smaller torque ripple, so that the operation is smooth and smooth.
