CFD Study Of Flow And Heat Transfer During Compression Process In A Liquid Piston For Isothermal Compressed Air Energy Storage

Abstract

Liquid piston technology has proved its efficiency into the achievement of Isothermal Compressed Air Energy Storage. While the concept is no more a new one, the description and the understanding of the physics of the flow and heat transfer during compression process are not completely achieved. Through a CFD study based on the resolution of Navierstokes equations and VOF method for interface tracking, a characterization of the flow and heat transfer inside the liquid piston, which are complex, are presented. The numerical results were validated and compared with the ones obtained in a former experimental study. Both velocity and temperature fields and profiles are analyzed locally and globally. In this study, it is found that with a compression ratio of 5 and compression time of 21s, the air's average temperature rises non linearly with 32K. The velocity and temperature profiles undergo several stages. A characteristic structure appears at the beginning of the compression where the flow is axisymmetric and remains so until its disruption. It is observed that the structure disruption occurs closer to the cylinder head moments after the highest local velocities are observed. Velocity fields analysis show that the air's velocity can be higher than 10 time the piston velocity.