Numerical simulation of particle soiling in the engine compartment of a bus
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The location of the air intake of a bus creates challenges from a soiling perspective. The proximity to the rear
wheels pulls up dirt from the road. Compared to a commercial truck, with the fan placement in the front of
the vehicle the air intake of a bus can’t rely on ram air pressure to get the sufficient cooling air mass flow. The
fan must always operate on high effect when the bus is driving and thus pulls in dirt. An understanding of the
flow of the dirt in the engine is necessary for a possibility to prevent it from soiling the engine compartment.
As physical evaluation of the dirt flow is very complicated a numerical method has been developed in the
present work. The computational fluid dynamics software STAR-CCM+ was used to simulate the airflow and
the particles released in front, under and from the rear wheels on the same side as the air intake of the bus.
Steady Lagrangian particle tracking was used to simulate the particle movement. The method developed can
be used to get a basic understanding of where the dirt particles enter the engine compartment. The method
is demonstrated for the flow around a fully detailed Volvo bus which includes cooling package and engine
compartment. The demonstration shows that the method can be used to analyse particle tracks, the size of
particles enters the engine compartment, the impact of different grilles on the particle intake, the difference in
the particle intake depending on the amount of air entering the engine compartment, the effect of the bus speed
and the difference when changing the geometry around the engine compartment on the number of particles
entering the bus engine compartment.
Keywords: cfd, soiling, engine compartment, lagrangian, steady, MRF, porous media, dirt

Thursday, January 1, 2015
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