What is the difference between internal circulation and external circulation in an engine?

[Beckett]

There is no distinction between internal and external circulation in an engine. Automobile Engine: An automobile engine is the device that provides power to a vehicle, serving as the heart of the car, determining its power, fuel efficiency, stability, and environmental performance. Depending on the power source, automobile engines can be categorized into diesel engines, gasoline engines, electric motors for electric vehicles, and hybrid systems, among others. Engine Starting System: To transition the engine from a stationary state to an operational state, an external force must first be applied to rotate the engine's crankshaft, causing the pistons to move reciprocally. The combustible mixture in the cylinders then ignites, expands, and performs work, pushing the pistons downward and rotating the crankshaft. Only then can the engine operate independently, and the working cycle proceed automatically. Therefore, the entire process from the crankshaft beginning to rotate under external force to the engine starting to idle automatically is called engine starting. The system required to complete the starting process is known as the engine starting system, which consists of the starter motor and its ancillary components.