Optimization of thermoacoustic engine design variables for maximum performance

Abstract

Thermoacoustic engine prototype design typically proceeds based on an intuitive, trial and error approach. This study investigates the benefits of performing a systematic optimization of design parameters in a thermo- acoustic engine for given operational requirements. The design optimization seeks to minimize a cost function of performance using the simplex method. This method allows constraints to be readily implemented without need for gradient evaluations. Parameter space maps are generated for visualization of solution sensitivity. System analysis is performed with the assistance of DeltaE, a commercially available software tool which solves the 1-D lossy wave equation in resonator sections and Rott energy and wave equations in stack sections. The solution is therefore subject to the low-amplitude (linear) flow assumptions and conduction mode heat transfer assumptions in heat exchangers. The optimization and space mapping tools systematically write input decks, execute DeltaE, and evaluate results. Optimization of up to 13 geometric, fluid, and material properties has been explored, producing encouraging performance predictions. Application of this strategy to design modifications of documented prototypes and resulting benefits of systematic optimization will be illustrated. It is anticipated that the optimization scheme will be useful in enhancing performance of future thermoacoustic engine prototypes.