Study of Thermoacoustic Engine for Automotive Exhaust Waste Heat Recovery 2019-01-1257

In this paper, the travelling-wave thermoacoustic engine (TAE) and its application for recovery of waste heat from automotive exhaust systems is investigated. The aim is to give some insight into the potential but also limitations of the technique for light and heavy-duty applications. This includes packaging, physical boundary conditions as heating and cooling available but also system perspective as influence of legislative drive cycles and degree of hybridization. First, the travelling-wave TAE is described as a low-order acoustic network in the frequency domain. Models, including non-linear effects, are set up for every component in the network to describe the propagation and dissipation of acoustic power. For a TAE with looped structure, the continuity of pressure and velocity is employed to determine the saturation pressure, as well as the stable operating point. These models are validated against experimental data available in the literature (Backhaus [4]). This is an engine designed for high-temperature application, but is well documented and yields a good reference for the models and to further the understanding of the TAE. Next, systems adapted to the operating conditions typical for light- and heavy-duty systems are proposed. No actual physical prototype has been built and verified, but the designs are based on, and are of the same efficiency, as machines that have been reported in the literature. The proposed designs are then used to discuss the practical implementation on a system level.