Effect of evaporation and condensation on a thermoacoustic engine: A Lagrangian simulation approach.

Acoustic oscillations of a fluid (a mixture of gas and vapor) parcel in a wet stack of a thermoacoustic engine are numerically simulated with a Lagrangian approach taking into account Rott equations and the effect of non-equilibrium evaporation and condensation of water vapor at the stack surface. In a traveling-wave engine, the volume oscillation amplitude of a fluid parcel always increases by evaporation and condensation. As a result, pV work done by a fluid parcel is enhanced, which means enhancement of acoustic energy in a thermoacoustic engine. On the other hand, in a standing-wave engine, the volume oscillation amplitude sometimes decreases by evaporation and condensation, and pV work is suppressed. Presence of a tiny traveling-wave component, however, results in the enhancement of pV work by evaporation and condensation.