Underhood Flow Management of Heavy Commercial Vehicle to Improve Thermal Performance

Thermal management of heavy commercial vehicles is crucial for improving their performance, especially in the engine compartment where heat rejection is more and cooling is a challenge. As heat rejected from the engine increases, this may affect other components like intake manifold. Heat localization in the engine compartment may lead to overheating. Hence to solve this problem and to maximize cooling performance of heavy commercial vehicles a CFD approach has been adopted. Steady state fluid flow analysis was carried out for the baseline model of 25 ton truck and with modifications; the results obtained are used for further improvement.

Numerical modeling has been carried out in HYPERMESH.11 and simulation has been done in the FEM based CFD solver ACUSOLVE.1.8. Spalart Allmaras turbulence model is considered for simulation. Complete analysis has been carried out in two stages: cold flow analysis and hot flow analysis. Cold flow analysis was done to improve flow circulation in the compartment whereas hot flow analysis was carried out for studying heat dissipation. On studying base line model results local modifications were done incorporating additional openings, flaps and shroud length extension Simulations were carried out for maximum power and maximum torque conditions, monitoring the mass flow rate, velocity and temperature at different locations in engine compartment.

Flow recirculation zones present are identified in Underhood compartment and it is observed that front openings, shroud length which covers radiator fan are very small for allowing adequate quantity of air through radiator. Modifications in the shroud geometry lead to 20% improvement in mass flow rate through radiator and intercooler. Modifications incorporated improved the velocity of air at radiator and over the engine surface. This led to about 20% increase in the heat rejection from radiator and exhaust manifold, thus reducing the maximum temperature of the hot spots e.g. close to the exhaust manifold maximum temperature reduced by 114.7°C.