Which type of pump is considered to be a positive displacement pump in fuel systems?

In fuel systems, a positive displacement pump is one that moves fluid by trapping a fixed amount within the pump and forcing that trapped volume into the discharge pipe. This mechanism contrasts with centrifugal pumps, which rely on rotational energy to move fluid, creating a pressure differential without a fixed displacement of fluid in each cycle.

The sliding vane pump is indeed a type of positive displacement pump. It operates by utilizing vanes that slide in and out of slots on a rotor as the rotor turns. This action creates chambers of varying sizes that fill with fluid on one side and then discharge it on the other, effectively pumping the fuel in a controlled manner irrespective of the pressure in the discharge line.

The gear pump, which is also a positive displacement type, uses two meshing gears to draw fluid into the pump and force it out. While this type of pump is commonly used in many applications, it was not selected as the correct answer in this context, possibly because the question was seeking a distinction based on the specific type explained or focusing on the sliding vane's characteristics.

Centrifugal pumps, although widespread in various applications, do not fall under the category of positive displacement pumps due to their method of fluid propulsion. As such, they are not a suitable choice in this