Organic Rankine Cycle for Vehicles: Control Design and Experimental Results

The system considered here is an organic Rankine cycle for recovering waste heat from a heavy-duty diesel engine. Because of the highly transient conditions these systems are subject to, control plays a fundamental role to enable the viability and efficiency of those systems. In this context, this paper investigates the problem of control design for superheating (SH) and pressure at evaporator outlet. Based on a moving boundary heat exchanger model, a first controller, which consists of a dynamic feedforward combined to a gain-scheduled PID, is implemented on the pump speed to maintain the SH close to the set-point value. Experimental results illustrate the enhanced performance in terms of disturbance rejection. Then, a second controller based on nonlinear state estimation is proposed. This is a nonlinear feedback law, which allows to adjust the evaporating pressure to time-varying demand with a good accuracy.