The Modeling Of Steam Ejector Refrigerating And Control Applied To Automobile Air Conditioning System

Not less than 30% of the energy is consumed usefully and 70% of the energy is converted into waste heat during the process of the automobile running. The highest temperature of the tail gas released by automobile engine can reach 600～700℃. The automobile air-conditioner which utilizes the waste heat energy of the automobile tail gas and the technology of the ejector refrigerating will be a substitute for the traditional automobile air-conditioner which utilizes the technology of the compression refrigeration, which has important economic and social interest for improving the utilization ratio of the primary energy sources.Base on the automobile air-conditioner of steam ejector refrigerating, the main factor influencing the refrigerating output, the pressure of the working steam, is confirmed. Using the knowledge of thermodynamics, the mathematical model of the critical components and objects for the ejector jet pump, evaporator, condensator, heat change space, measurement segment and driving segment is completed with the method of mechanism and experimental model-building. The mathematical model of refrigeration cycle system and the object model of the temperature control for the operator cabin are put forward in the paper.Aiming at the characteristics that the automobile air-conditioner has many interference factors, nonlinearity and long lag time, Self-tuning fuzzy-PID control controller is designed to realize the control for the refrigerating output. The optimum matching between the refrigerating output and the load is realized under various kinds of loads, which is achieved through fuzzy controller on-line adjustment on the value of the proportional, integral and differential parameters. Based on the known refrigerating output, the thermoregulation of the operator cabin is realized through adapting PID control strategy controlling the rotating speed of the evaporator fan. For the above-mentioned modeling and control strategy, the simulation was carried out under the environment of Simulink of MATLAB software. During the simulation, random interferences were applied and all kinds of operation modes of the automobile are imitated. Compared to the traditional PID, self-tuning fuzzy-PID has fast response speed, small overshoot and powerful anti-interference ability. The method in this paper is fit for the control of the automobile air-conditioner.