Final answer:
The main, scavenge, and transfer ejectors in engines are powered by motive flow pressure, a principle where a high-velocity fluid entrains another fluid, transferring energy and carrying the fluid along.
Step-by-step explanation:
Main, Scavenge, and Transfer Ejectors Power Source
The main, scavenge, and transfer ejectors are powered by motive flow pressure. Ejectors are a type of entrainment device that operate on the principle of using a high-velocity fluid to entrain another fluid, thereby transferring energy from the motive fluid to the entrained fluid, which is then carried along with the motive fluid. For example, in figure 14.31(b), an atomizer uses a jet of air to entrain drops of perfume, similarly to how ejectors in an engine would operate using motive flow pressure.
The available options for power sources hint at different physical principles used to operate various devices. Hydraulics, mentioned in several other contexts such as power brakes or hydraulic jacks, rely on hydraulic pressure to perform work. However, in the context of ejectors, the correct power source is the motive flow pressure created by the fluid speed, in line with how an aspirator or paint sprayer would function.