The main objective of the HT&ML model is the easiness to be
used coupled with a general purpose models like GT-Power. For
that reason, a 1D lumped model is chosen as described in Ref. [20]
and presented in Fig. 2. In the model, the turbocharger has been
divided in five metal nodes: one for the turbine case, one for the
compressor case and three for the bearing housing. The variables of
this model have been computed using experimental data provided
by tests performed in specific test rigs, saving the costs of engine
bench tests. On one hand, the thermal properties of the turbocharger
are calculated from measurements on a thermohydraulic
test bench described in Ref. [21] and following the procedure
explained in Ref. [22]. On the other hand, measurements in a hot
flow gas stand allowed to obtain the correlations for both internal
heat transfer [23] and external heat transfer [24]. In addition, in
order to adapt a mathematical model for turbocharger mechanical
losses as described in Ref. [25], adiabatic measurements from gas
stand have been used. Therefore, using these models, the calculation
of heat transfer and mechanical losses for any operating condition
of the turbocharger in the engine is possible.