Numerical simulation of particle soiling in the engine compartment of a bus

Abstract

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.