Modelling And Control Of Waste Heat Utilization Using Organic Rankine Cycle

In this paper, evaporator and scroll expander integrated into Organic Rankine Cycle(ORC) system were studied. Firstly, On the basis of previous work about them, a detailed modeling process about evaporator was presented and its model was transformed into state space form according to predecessor’s research. After analysing mathematical model of evaporator, it is a non-minimum phase, time-varying and uncertain system. According to its characteristics, self-tuning controller based on generalized minimum variance control and forgetting factor recursive least squares parameter estimation method was applied to evaporator. Simulation showed good stationary and dynamic performance of controller along with strong anti-inference ability proper. The controller applied in evaporator obtained good results, which could be referenced by researchers.Secondly, on the basis of prehominid’s research on scroll expander, two groups of nonlinear differential equations were established according to mechanism analysis of scroll expander, which were based on static mathematical relationship. The relationship was formed by supply pipe and supply chamber, expansion chamber and exhaust chamber etc. Firstly, one nonlinear equation was built between valve opening and pressure at supply pipe inlet. Secondly, another equation was set up between internal power of the expander and rotating velocity. Pressure at supply pipe inlet was connected with internal power of the expander. Finally dynamic model was obtained, whose input variable was valve opening and output variable was rotating velocity. Simulation showed that the model was in accordance with the characteristics of practical model of scroll expander. On account of characteristics of time-varying and uncertainty in mathematical model of scroll expander, a fuzzy immune PID controller was applied by means of borrowing ideas from biological immune feedback mechanism and combining fuzzy control. Simulation showed that overshoot of the output was less than PID’s, response speed was faster, the controller had strong robustness and anti-inference ability. Meanwhile, the impact of some parameters on controller were studied, which was important to select the controller parameters. Since research on control of scroll expander was few, fuzzy immune PID controller had been applied for scroll expander successfully, which had a reference value for future work.