Frequency rotation regulator of indirect action without feedback

Regulator of indirect action is called a regulator, in which replacement of CU is not done due to the SE’s efforts but with the help of servomechanism with using energy from external source. This allows you to provide large rearrangement efforts, required for CU displacement in engines with large fuel consumption. Structural scheme of frequency rotation regulator of the indirect action and its functional scheme are shown on the fig. 5.3.

Fig. 5.3. Structural scheme (a), static characteristic (b), functional scheme (c) of frequency rotation regulator of indirect action without feedback

By construction this regulator changes from direct action regulator only those that in its executive connection the servomechanism (2) and control device (1) are included.

Disagreement between the actual and desired values ​​of rotation frequency comes from a comparison element (3) (executive connection rod) up to control slide valve (1) and further to the servomechanism (2) with dozing needle as the corresponding signals.

In the process of frequency rotation control the strengthened signal from thesensing elements using servomechanismis transferred to CD regulator. Regulator’s SE is connected with slide valve 1 (shown at the neutral position), that corresponds to the equilibrium frequency of rotation

In given regulator independent from CD location the equilibrium modes will be in the same position of control sliding valve 1. At the constant TCL position the unchangeable position of slide valve can be only at constant centrifugal force SE, i.e. at n = const.

Thus the regulator in its scheme is astatic and in principle can exactly, without static error to maintain a given rate of rotation by changing of external conditions (Т^*_н або р^*_н).

Consumption characteristics oftheregulator isshowninfig. 5.3, b.

Lines 1 and 3 maintains the necessary fuel consumption, built in accordance with rotor frequency rotation for several different ambient conditions, which are characterized Т^*_нor р^*_н.

Line 2 – fuel consumption, which maintains by regulator at ambient conditions changings.

Such character of change of fuel supply includes static error during control.

But absents of direct rigid feedback between SE and CE in such regulators leads to appearance of frequency rotation damped oscillationsin transition process. The appearance of oscillations is the resultof large rotational inertial mass efforts ofturbineand compressor,which are the cause of delay or increase of the rotor rotation frequency at fuel supply changes.

Advantages of regulator:

· Considered regulator is static, i.e. maintain supply of required frequency of rotation at ambient condition changes without appearance of static errors;

· Due to using theservomechanism in regulator, large replacement effort of CD is provided

Disadvantages of regulator:

· Transition processes with such regulators has oscillation character, which is associated withintricate-type changes of frequency rotation because of the inertia mass of the rotor feeding fuelinto the combustion chamber.

Regulator of the indirect action because of bad dynamic characteristics cannot be used in modern GTU controlsystemsto maintain their operation on the basic exploitation modes. But good static properties and high replacement effort for removing CD allows to use regulators of given scheme as one-mode regulators or limiters of maximum rotation frequency in modern engines and, firstly, in aviation turbo shaft engines.

Date: 2015-02-16; view: 892