Final answer:
The engine-driven pump supplies high-pressure fuel for an engine's combustion and motive flow, while the unused energy in an engine is typically converted into heat due to inefficiencies.
Step-by-step explanation:
The component that supplies high-pressure fuel for combustion and motive flow operation in an engine is the engine-driven pump. This pump is designed to pressurize fuel to the correct level so it can be effectively sprayed into the combustion chamber by the fuel injector. Devices like the Bunsen burner and the aspirator mentioned in the provided figures utilize similar entrainment principles to mix fluids, but for the context of an engine, it is the engine-driven pump that provides the necessary pressure for the fuel system.
As for the second question, in an engine, the unused energy is typically converted into heat. This is a byproduct of inefficiencies within the engine where not all of the potential energy within the fuel is converted into useful work, leading some of it to dissipate as heat.