TheCNC2020 | Method of analysis and calculation of basic parameters in hydraulic control circuit

Method of analysis and calculation of basic parameters in hydraulic control circuit | thecnc2020

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1.1. The relationship between pressure and flow

1.1.1. Hydraulic source

Currently, people divide hydraulic resources into two types:

- The source of the traffic remains unchanged.

- Constant pressure source.

According to ISO R1219, hydraulic sources are designated as shown in figure 1.1.

 

Method of analysis and calculation of basic parameters in hydraulic control circuit

Figure 1.1. Symbol for hydraulic power

a- Constant flow source;

b- Constant pressure source.

The above symbol is actually the symbol of the oil pump, when there is an additional letter I in it, it means that

is the ideal power supply (no flow loss and no pressure loss in the pump).

The power in the hydraulic circuit is determined by:

or : N = P.

N = dt dE with E = dtdV∫dV.P (1.1)

 = P.Q (1.2)

where : E - characterizes work;

  V - the volume of liquid transferred;

  N - transmission power;

  P - fluid pressure.

Depending on the dimensions of pressure P and flow Q, formula (1.2) has additional coefficients.

means : P.Q = US

The computational model of the ideal traffic source is:

NX out = N in .Ω (1.3)

in which : US

  - torque on the pump inlet shaft;

Ω - angular velocity of the pump shaft.

If V is the volume of pumpable liquid, D is the working capacity of the pump in one radian, and θ is the rotation angle of the pump, we have the relationship:

V = D. (1.4)

Take the derivative ( 1. 4 ) :

where : dtdVdVθ= .Ddt = Q and Ω=θdtddtd so Q = D.Ω (1.5)

Replace (1.5) into (1.3): P.Q = P.D.Ω = M. Ω

or : Mxx = P.D (1.6)

If the measured capacity in one revolution of the pump is D

vg then : D (1.8)

In the case of a constant pressure source, the outlet flow may change according to a certain function, but the outlet pressure is always constant.

The above formulas are also used to calculate for diesel engines.

How many types of hydraulic circuits are there?

Open loop hydraulic system and closed loop hydraulic system are the two types of hydraulic system. In an open loop system, when the actuating mechanism is idle, there will be fluid flow but no pressure.

How do hydraulic cylinders work?

A hydraulic cylinder is a mechanical mover that provides strong force in one direction. Hydraulic cylinders typically get their power from a pressurized hydraulic liquid, usually oil. The cylinder creates pressure and then uses that pressure to move the piston piece of the cylinder forward

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• Hydraulic transmission and control engineering
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• Method of analysis and calculation of basic parameters in hydraulic control circuit

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