Frequency rotation regulator of indirect action with rigid feedback (RFB)

Frequency rotation regulator of indirect action with rigid feedback, which is stabilized means of frequency rotation during transmission process, is used for improving of system control dynamic characteristics.

Frequency rotation regulator with RFB (fig. 5.4.) is the following development of astatic regulator of indirect action. For deviation in operating mode from equilibrium SE, slider valve and control device in regulators with RFB reacting in the same way, as appropriate elements of astatic regulator of indirect action.

The difference is the servomechanism’s piston movement is transmitted both CD and lever AC (fig 5.4. a), this leads to its rotation around point A.

The result is that slide valve moves in opposite direction of initial movement, i.e. approaching it to the neutral position. As a result of this process controlling stops more quickly. On the functional scheme of the regulator (fig 5.4. c) we can see, that link of feedback enclose CSV and servomechanism. Servomechanism output signal transform into feedback, and in the view of coordinate zfeeds at output in CSV again, where it is summarized with non-coordination signal Dn.

Fig.5.4. Structural scheme (а), static characteristic (b) and functional scheme (c) of frequency rotation regulator of indirect action with rigid feedback

Choosing the correlation of lever of feedback AC we can provide the slider valve movement, at which time of windows opening decreases and slide valve blocking and movement congestion of CD at fuel feeding increasing appears more quickly than obtaining by engine a new frequency rotation value. Due to this overcorrection and frequency rotation variation hardly decreases.

Including of RFB into the regulator improve characteristics of regulator but decreases its static properties. For understanding this fact it’s necessary to compare regulator details location for the same fixed RFB position at two different operation modes, which is characterized by temperature and atmospheric pressure. For example at more low ambient temperature of air with higher fuel consumption by engine - line 1 (see fig. 5.4.b) and with higher ambient temperature and with lower fuel consumption – line 5.

When the process of steering stops by the reason of ambient conditions, slide valve CSV will take a neutral position, blocking by its belts both supplying channels, which provides movement of working fluid into the servomechanism body.

So, at equilibrium modes at the same fixed position of TCL at different external conditions point B of lever AC will take the same position. AtambientairtemperatureincreasingТ^*_нfor decreasing fuel feeding the servomechanism piston must sink, herewith point C will sink down to position С¢.

Such kind of servomechanism replacement with dozing needle, lever and executing feedback rod can works only at engine frequency rotor rotation increasing and appearance of centrifugal force excess, which compresses set up regulator spring.

Accordingly, at unchangeable turning of regulator with RFB, temperature increasing of ambient air and connected with this decreasing of consumer's moment for compressor driver leads to increasing of rotation frequency .

Evidently, that air temperature decreasing leads to frequency rotation decreasing, i.e. in both cases the static error appearance will take place. Similar processes will appear at ambient air pressure р^*_н changes.

That condition is confirmed by consumption characteristics (see fig 5.4. b)

Lines 1 and 5 show necessary fuel consumption for different ambient conditions, line 3 – fuel consumption, which is supported by regulator at ambient conditions changes, Dn = n₁ – n₀ – static controlling error. As it follows from the figure, if we change arms a andbcorrelation of lever AC, it will change the static and dynamic characteristics.

Advantages of regulator:

· frequency rotation regulator of indirect action with rigid feedback provides high dynamic characteristic oа controlling system, i.e. gives the possibility to get aperiodic or close to it transition process of controlling;

· regulator can be used for engines with high fuel consumption

Disadvantages of regulator:

· this regulator according to the principle of operation has static error, its limited the ranges of regulator exploitation.

As a rule, frequency rotation regulator of indirect action with rigid feedback is used in ACS GTE(GTU), which operates at low temperature ranges and ambient air pressure. Sometimes regulators of such a type equipped with additional devices – correctors of static error. More effective method of static error disposal and obtaining of good dynamic control characteristics is using in regulators fundamentally different feedback, which obtains the name flexible or isodromic feedback.

Date: 2015-02-16; view: 1086