Rotary piston pump

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The term rotary lobe pump is the collective term for the rotary vane pump and the rotary lobe pump .

Piston engine

Piston machines are machines that either increase or decrease the potential energy of a fluid (the pressure of a gas or a liquid) by adding or removing mechanical energy with the aid of a displacement component (piston). In the case of a compressor (for gases) or a pump (for liquids), potential energy is supplied to the medium via the piston (pressure increase). In the opposite case, with engines, the potential energy of the medium is converted into mechanical energy via the piston, which can then be tapped via the connecting rod on the crankshaft.

Rotary flask

Depending on the type of movement, a distinction is made between reciprocating pistons and rotary pistons.

In the first case, a cylindrical piston acts as a displacer and moves axially in a cylinder between two end positions (bottom and top dead center ).

In rotary piston machines, a rotating displacer causes the working space with the fluid to breathe.

Basic forms of rotary piston pumps

According to the center of gravity of the displacer and the working area, which can also perform a rotating movement, a distinction is made between four basic forms of rotary piston pumps.

  • The rotary lobe pump is characterized by an external axis design according to Roots (1848). It is free of rotating and oscillating inertial forces ( imbalance ).
  • The rotary piston pumps have an internal axis design according to Wankel (1954). According to the principle of their design, they have an imbalance, but this can be completely compensated for by closed chambers and differences in material density within the piston.
  • The rotary piston-like circulating piston pumps according to Trotter (1805).
  • The rotary piston-like piston pumps according to Wittig (1900) or rotary vane pumps.

The last two types of pumps mentioned have free inertia forces that cannot be compensated due to the rotating and oscillating movement of the displacer and also the wall parts that form the working space. Their speed is therefore limited to low to medium speeds, whereas rotary lobe pumps are suitable for high to very high speeds.