The internal combustion engine obtains repulsive force by high pressure, and high pressure is constituted by combustion of fuel in the combustion chamber. In response to this repulsive force, the piston begins to move and supplies the engine output to the mechanical parts necessary to actuate the piston. This is the mechanism of the internal combustion engine. In other words, the internal combustion engine is a machine that rotates the chemical energy of the fuel before the fuel rotates. Since combustion is done inside the engine, it is called internal combustion engine.
Internal combustion engines are engines in which the combustion of fuel (usually fossil fuel) is carried out in the combustion chamber using an oxidant (usually air). In internal combustion engines, the expansion of high-temperature, high-pressure gases generated by combustion creates mechanical work by applying force directly to the components of the engine, such as pistons or turbine blades or nozzles, and moving it a distance. An external combustion engine (EC engine) is a heat engine in which an internal working fluid is heated by an engine wall or a heat exchanger by combustion from an external source. Movement and available work are then generated by the fluid which expands and acts on the engine mechanism. The fluid is then cooled, compressed and reused (closed cycle), or (less commonly) discarded and the coolant is sucked in (open cycle air engine).
An internal combustion engine (ICE) is a heat engine in which the combustion of fuel is carried out in the combustion chamber using an oxidant (usually air), which is an integral part of the working fluid flow circuit. In internal combustion engines, the expansion of high-temperature, high-pressure gases produced by combustion exerts a direct force on certain components of the engine. This force is usually applied to the piston, turbine blade, rotor or nozzle. This force moves the part a certain distance and converts chemical energy into useful mechanical energy.
Like gasoline engines, diesel engines are internal combustion engines. Combustion is another term of combustion, the interior is internal, so the internal combustion engine is just where the fuel burns in the main part (cylinder) of the engine. This is very different from the external combustion engine used in the old steam locomotive. In a steam engine, there is a big fire at one end of a boiler that generates steam by heating water. Steam flows through a long tube and flows into the cylinder at the other end of the boiler where it pushes the piston back and forth to move the wheel. This is external combustion as the fire is outside the cylinder (actually 6 to 7 meters or 20 to 30 feet in fact). In gasoline or diesel engines, the fuel burns in the cylinder. That's why internal combustion engines are more efficient than external combustion engines (they produce more energy from the same amount of fuel).