The automotive industry is currently driven to reducing fuel consumption in internal
combustion (IC) engines and hence much research is being done into alternative fuels and
power sources. Thermal energy recovery from IC engines has proved to be of considerable
interest within the automotive industry. The motivation is that fuel consumption can be
reduced with a minimal effect on the “host” technology of the vehicle.
This thesis reports on a project that aimed to investigate the architecture and control of a
thermal energy recovery system, working towards proving this novel system concept. This
was achieved by the use of software modelling techniques and experimental tests on
various components of the system, namely heat exchangers and steam expanders. Various
modelling toolboxes were used to model a) a hybrid vehicle configuration and b) steam
expanders. The hybrid vehicle modelling began as a basic model to demonstrate the hybrid
application and configuration of the steam system, and was further developed to control and
optimise the system in such a way that the fuel economy, the overall efficiency of the IC
engine and the heat recovery system were all maximised. Standard drive cycles were used
to run the hybrid vehicle models. The steam expander modelling was performed in order to
validate the results from a series of experimental tests and also to deduce if the expander
models could be scaled up to predict results for larger expanders.
The fuel consumption for the initial modelling showed a reduction of between 8% and
36%, depending on drive cycle and modelling toolbox used. With the development of a
simple PID controlled system, the fuel consumption was further reduced resulting in a
range of 26% to 41%, again depending on drive cycle and modelling tool box. The
experiments on steam expanders point to a uni-flow configuration being the most suitable.
The expander modelling presents the groundwork for developing expander models to be
used for validating the experimental results; again the uni-flow arrangement gave the most
This thesis presents the results and draws conclusions from each project step; these
conclusions are summarised together with some recommendations for future work.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.