Control of ThermoAcoustic Phenomena with Applications to Novel Energy Conversion Devices

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Thermoacoustic energy conversion devices are engines and refrigerators in which mechanical work is done by intense, contained pressure waves rather than the traditional pistons, cranks or turbine mechanisms present in traditional engines and refrigerators. These devices have almost no moving parts, thus minimizing mechanical friction losses and leading to potentially higher efficiencies than traditional ones. This award supports research leading to new types of thermoacoustic devices in which active control enables the optimization of thermodynamic cycles and adaptation to rapidly varying loading and operating conditions. These smart thermoacoustic devices are integrated with control electronics, thus transferring complexity from mechanical design into the design of the control algorithm, where it can be much more easily implemented. They are particularly suited to unpredictable and time-varying settings such as those that harness waste heat or small-scale solar-thermal power. The control design techniques investigated in this project include (a) optimal design of periodic operating trajectories of thermoacoustic systems using the techniques of Optimal Periodic Control (OPC) as well as frequency domain methods, (b) the design of feedback for regulation of periodic distributed systems around spatio-temporal limit cycles, and (c) the investigation of the limits of performance in the control of thermoacoustic systems with point versus distributed sensing. Aside from their direct relevance to thermoacoutic systems, these research topics are important in a wide class of spatially distributed dynamical systems that occur in flow and gas dynamics, flexible structures and other domains. Another significant component in the proposed research program is the experimental investigation of control design concepts in several thermoacoustic devices including new varieties of Rijke and Sondhauss tubes, as well as thermoacoustic engines and heat pumps.