What is the difference between a centrifugal pump and a positive displacement pump

The positive displacement pump is proportional to the speed and flow rate, such as gear pumps, screw pumps, plunger pumps, etc., for example, their flow rate is 1 cubic at 100 rpm, and it can be understood as 10 cubic at 1000 rpm, but it is actually a bit efficient. Loss, the flow is about 9.5-9.8 cubic meters;

Centrifugal pump: He relies on the high-speed rotation of the motor to throw the medium (generally the medium with lower viscosity: such as water, diesel, kerosene, gasoline, thermal oil, etc.) by the flow channel of the impeller to throw the medium out.

There are also volumetric pumps that can transport media with relatively high viscosity, such as heavy oil, viscous oil, asphalt, and other media with higher viscosity; centrifugal pumps can only transport some media with lower viscosity, and his transport viscosity can only be lower than 3Cst (centist )