Creation of Dynamic Model for Optimization of the Temperature Control Loop in the Air Conditioning System of an Aircraft
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CREATION OF DYNAMIC MODEL FOR OPTIMIZATION OF THE TEMPERATURE CONTROL LOOP IN THE AIR CONDITIONING SYSTEM OF AN AIRCRAFT I. V. Tishchenko, N. A. Lavrov, and S. I. Khutsieva
UDC 621.56
The temperature control loop of the actuating air following the heat exchanger is considered. The control loop consists of a heat exchanger, adjustable air intake, circulation fan, temperature sensor, and temperature controller. A dynamic model of thecontrol loop that takes into account the automatic control system is created. Transient processes that arise in the control loop as a consequence of variations of the altitude of the aircraft are considered. Results of the variation in the actuating air temperature at a temperature control point are obtained. Partial optimization of the coefficients of the controller is performed. Optimal coefficients of the controller are selected. Keywords: air conditioning system, mathematical simulation, dynamic simulation, heat exchanger, control, optimization.
The creation of mathematical models of plants and systems is an increasingly critical need today [1–3]. The creation of steady-state models applied to cryogenic and adsorbent plants has been the subject of many studies [4–6], and the creation of dynamic models applied to cryogenic plants has also been subject of studies [7–9]. The creation and application of models has helped to reduce the volume of tests needed to confirm the characteristics of a plant. The objective of the present study is to develop the control loop of the temperature of the actuating air behind the heat exchanger in the air conditioning system of an aircraft. Temperature Control Loop The pneumohydraulic design of the control loop is presented in Fig. 1. Actuating air from the engine enters the heat exchanger where it is cooled by scavenging air taken from the environment. The temperature of the actuating air behind the heat exchanger is regulated by varying the discharge of scavenging air (through regulation of the air intake). The automatic control system (Fig. 2) that governs the temperature of the actuating air functions in the following way. A signal from the temperature sensor (TS) enters the comparison element (CE) of the controller (C) where the signal is compared with the set value and the deviation generated. A signal to the control element (1 — open; 0 — no action; −1 — closed) is generated by the controller based on the deviation found. A control action (h) for the subject of control is generated by the final control element. In the loop the temperature of the actuating air behind the heat exchanger is the adjustable parameter (y); the coefficient of resistance of the air intake, variation of which induces a variation in the discharge of the scavenging air, which in turn affects the adjustable parameter, is the control action (h). A decrease in the coefficient of resistance of the air intake tends to increase the flow rate of the scavenging air, moreover, the temperature of the actuating air behind the heat exchanger also decreases. Bauman Moscow State Technica
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