Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.
Turbochargers are widely used in applications to increase
specific power and decrease fuel consumption. However,
recent anti-pollution regulations have became stricter and
pressed automotive engineers to find new solutions to reduce
Nox emissions. Two of these solutions are the catalytic
converter and the intercooler system. All these modifications
will change the initial matching of the turbocharger
performance characteristics to the engine requirements. In this
paper, several compressor wheel sizes are investigated to
evaluate the turbine/compressor matching. The intercooler and
catalytic converter back pressure induced are respectively
modeled by a lower duct section downstream the compressor
stage and a variable valve downstream the turbine stage. The
influences of the different modifications are identified through
the loading and the flow coefficients and also on classical
turbine performance maps. First, an analogy between
compressor wheel size and back pressure effects is underlined.
Second, it is shown that initial control settings of turbine
nozzle vanes are no longer appropriate with a catalytic
converter.
