Regulation of the gas temperature in the gas turbine engine
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Regulation of the gas temperature in the gas turbine engine

Regulation of the gas temperature in the gas turbine engine

One of the important requirements to the GTE control characteristics is the high accuracy of maintaining (limiting) the set gas temperature in the established and transient modes of its operation, since the quality of regulation at the gas temperature limit modes is important for obtaining the required characteristics and saving the engine resource. The errors in the control of the gas temperature in steady-state conditions should not exceed 5. .10 K, and in transition modes the permissible temperature "casting" is 30. .50 To at most 0,5. .1c. At the same time, the rate of change of the gas temperature in transient regimes can reach 500 K / s.

Thermocouples are used as gas temperature meters in the automatic control system, which are placed in the case (cover) to protect them from damage. In this constructive design, the meter has a sufficiently large inertia that prevents obtaining the required dynamic accuracy of the gas temperature control (restriction) during fast transient processes in the engine, for example, such as injectivity. To improve the dynamic properties of the gas temperature regulator, algorithmic compensation of the inertia of the meter is applied by introducing into the control signal an action on the derivative of the measurement signal. An improvement in the quality of compensation is achieved by correcting the parameters of the algorithm for the air pressure behind compressor p or a set of parameters.

Stability control gas temperature depends on the temperature gauge performance, control algorithms and methods for harmonizing regulatory T channel with other control channels in the ACS. However, the general law is to reduce the regulatory stability while reducing the inertia of the channel regulation in various ways (using low-inertia meters, the introduction of compensating devices). This trend holds for different types of engines in all flight conditions.

This regularity illustrate the boundaries of the stability of the temperature control to one of the engines shown. On the charts, the following symbols: - total coefficient temperature controller gain characterizing the signal value of the derivative but in proportional-integral-differential (PID) controller temperature of the gas; Titus - time constant, which characterizes the inertia of the temperature of the gas meter. Hatching is directed into the region of stability.

This feature of resistance management characteristics determine the contradictions in the requirements to the parameters of the gas temperature regulator, which should ensure high quality regulation in the transient operation of the engine and the required accuracy to install: you must have a low inertia channel regulation that does not allow to realize a sufficiently high gain in it for obtaining the required accuracy to maintain a given value of T in the steady-state conditions.

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