Hydraulic machine

Detailed view of a hydraulic pump.

A hydraulic machine is a variety of fluid machine that uses the properties of an incompressible fluid for its operation or that behaves as such, due to the fact that its density inside the system does not undergo significant variations.

Conventionally, a limit of 100 mbar for pressure change is specified for gases; so that if this is lower, the machine can be considered hydraulic. Within hydraulic machines, the fluid undergoes an adiabatic process, that is, there is no heat exchange with the environment.

Types

Gear pump.

Gear pump.

Gear pump.

Hydraulic machines can be classified according to different criteria.

Depending on energy variation

In hydraulic motors, the energy of the fluid that passes through the machine decreases, obtaining mechanical energy, while in the case of hydraulic generators, the process is reversed, so that the fluid increases its energy as it passes through the machine.

According to the type of fluid dynamic energy that is exchanged through the machine, we have:

• Machines in which a variation of potential energy occurs, such as the Archimedes screw.

• Machines in which there is a variation of kinetic energy, such as turbine turbine turbine, turbine turbine turbine or turbine. These are called action machines and have no housing.

• Machines in which there is a variation of the entalpia (pressure), such as centrifugal pumps. These machines are called reaction machines.

Depending on the type of exchange

Taking into account the way in which energy is exchanged within the machine, its classification can be as follows:

• Machines positive or volumetric displacement. It is one of the oldest types of hydraulic machines and are based on the displacement of a volume of fluid by compressing it. The clearest example of this type of machine is the air pump for bicycles. They supply a flow that is not constant, to avoid it at times they join several to achieve greater uniformity. These machines are suitable for high-pressure and low-flow supplies.

According to the enclosure

According to the presence or not of casing:

• Machines not intubated as they can be all the ones below present action machines.

• Intubate machines.

According to the movement

There are other criteria, such as the division into rotary and reciprocating, depending on whether the energy exchanger has a rotary or reciprocating movement. This classification is very intuitive but does not meet the basic principle of operation of these machines.

The following table shows a summary of the classification of hydraulic machines (l=liquid, g=gas).

Components

• Pumps
• Control valves
• Actuators
• Deposits
• Accumulators
• Tubs and hoses
• Boards and closures
• Exchangers
• Hydraulic flow
• Filling systems
• Screws