Computer model of the performance of a thermoacoustic generator

Abstract

A computer program is developed to predict the performance of a thermoacoustic generator. The defining relationships are based on equations derived using short stack and boundary layer approximations. The engine modeled is the five inch engine currently in operation at Los Alamos National Laboratory. The working fluid in the model is a helium-argon gas mix, chosen to provide flexibility in placing the transducer relative to the thermoacoustic stack assembly while maintaining resonance near the desired operating frequency of 120 Hz. The transducer model is based on a linear alternator design proposed for use with the L. A. N. L. engine in the future. The thermodynamic properties of the gas mix are determined using virial equations and binary gas mixture relationships. The defining relations are solved simultaneously and an iterative process is used to optimize the gas mix. The variables for which the program then solves are pressure amplitude, hot heat exchanger temperature, and angular frequency as functions of input heat flux, system geometry, and load characteristics. From these, the power output and total system efficiency are determined.