Final answer:
A rotary engine uses a triangular rotor, providing a smoother operation compared to conventional piston engines that use a flywheel to smooth out vibrations caused by piston firings.
Step-by-step explanation:
A rotary engine uses a triangular rotor instead of conventional pistons. Unlike conventional piston engines which use cylindrical pistons moving back and forth in cylinders, rotary engines have a uniquely shaped rotor that rotates within an epitrochoidal housing. The rotor performs the same four operations as the pistons in a conventional internal combustion engine: intake, compression, power, and exhaust, but in a circular motion rather than an up-and-down piston motion.
The presence of a flywheel in conventional piston engines smoothens out engine vibrations which are a result of the individual piston firings. As each piston fires, it imparts a force to the crankshaft; the flywheel provides inertial resistance to these rapid changes in rotational speed, thereby smoothing the operation of the engine. Rotary engines deliver smoother power as the rotational movement eliminates the reciprocating mass of pistons, thus a flywheel isn't as critical. However, most rotary engines still utilize a flywheel for better inertia and operating characteristics.