Final answer:
Diesel engines compress only air and inject fuel at high temperatures for ignition, differing from gasoline engines that compress a mixture of air and fuel and require a spark for ignition.
Step-by-step explanation:
Diesel engines do indeed operate with an internal combustion process, but the statement that a mixture of air and diesel fuel is needed to ignite and operate the engine is not entirely accurate. In diesel engines, only air is compressed during the intake and compression strokes, and due to this compression, the air temperature increases significantly. Fuel is then injected into the hot, high-pressure air in the cylinder, leading to ignition without the need for a spark. This differs from gasoline engines, where a mixture of air and fuel is compressed, and a spark is used for ignition.
In relation to the ideal diesel cycle, it comprises of five strokes: intake of air, compression of air, fuel injection and power stroke, and two exhaust strokes. However, real-world diesel engines typically operate on a four-stroke cycle: intake, compression, power, and exhaust.