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Contents >> Engineering Mathematics >> Hydraulic Systems >> Dynamic Express Analysis >> Typical structures of hydraulic circuits and their description

Dynamic express-analysis of hydraulic systems - Typical structures of hydraulic circuits

Typical structures of hydraulic circuits and their description

The decision of the problem is based on representation of structure of the hydraulic circuit in the form of set of separate components – functional blocks of which practically any hydraulic circuit (Fig. 1) usually consists. There are: a diesel engine, pump station of open type (with an opened flow circulation), pump station of closed type (with a closed flow circulation), hydraulic actuators (hydraulic motor, two in parallel connected hydraulic motors, hydraulic cylinder, two in parallel connected hydraulic cylinders), various kinds of loading (elastic-inertial of forward or rotary action, wheel carrier), machine (block of simulation of progressive machine motion at tractive-dynamic calculations). Each of listed functional blocks is described by system of mixed differential and algebraic equations.

Fig.1. Functional blocks of hydraulic systems.

a – diesel engine with centrifugal regulator;  pump stations: b – with opened flow circulation, c – with closed flow circulation; hydraulic actuators: d – single hydraulic motor, e – two in parallel connected hydraulic motors,  f  – single hydraulic cylinder, g – two in parallel connected hydraulic cylinders;  elastic-inertial loading: h – of forward action, i – of rotary action;  j – wheel carrier, k – machine

In a basis of the structural description of the hydraulic circuit an identification of functional blocks and representation lays, that each of them has no more than four nodes (points) in which it incorporates to other blocks of the circuit (Fig.1). The binding of nodes and identification of functional blocks are carried out as follows (tab. 1):

 

Table 1. Classification of functional blocks of hydraulic systems

    Functional block

Block identifier

    Node  i

   Node  j

      Node  k

      Node  l

Diesel engine

DIESEL

-

-

Engine shaft

Regulator muff

Pump station

with opened flow

circulation

OPENED

 

Pressure head line*)

Drain

line *)

Pump shaft

        

 

-

Pump station

with closed flow

circulation

CLOSED

 

Pressure head line

Drain

line

Shaft of basic

and boost pump

-

Hydraulic motor

 

MOTOR1

Pressure head line

Drain

line

Hydraulic motor shaft

-

Two in parallel

connected hydraulic

motors

MOTOR2

 

Pressure head line

Drain

line

Hydraulic motor shaft

Hydraulic motor shaft

Hydraulic cylinder

CYLINDER1

 

Pressure head line

Drain

line

Hydraulic cylinder rod

-

Two in parallel

connected hydraulic

cylinders

CYLINDER2

 

Pressure head line

Drain

line

Hydraulic cylinder rod

Hydraulic cylinder rod

Elastic-inertial

loading

LOADING

 

 

-

-

   Moving mass

Hydraulic motor shaft or    hydraulic cylinder rod

Wheel carrier

WHEEL

 

 

Wheel axis

 

 

Contact

point of

wheel with

road

Machine case

     

 

 

-

Machine

 

 MACHINE

 

Machine case

-

-

-

 

*)  Hereinafter pressure head and drain lines are defined by accepted direction of flow of a working liquid. At change of a direction of flow when pressure head and drain lines vary places, there is a change of signs on corresponding flows of liquid, a binding of nodes i and j thus remains constant.

By preparation of the hydraulic circuit for calculation its nodes are numbered in the arbitrary order then the structure of the circuit is described by a matrix which line looks like:

where Т – functional block identifier; n – number of the given type  block;numbers of block nodes.

The functional block identifier serves for a choice from the library of mathematical models the system of equations corresponding given type of the block. The variables entering into the equations of the block both describing its input and an output, are indexed under numbers of nodes of the given block.

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Last updated: April 30, 2015.