Pseudo-transient computational fluid dynamics analysis of an underbonnet compartment during thermal soak

Abstract

Underbonnet simulations are proving to be crucially important within a vehicle development programme, reducing test work and time-to-market. While computational fluid dynamics (CFD) simulations of steady forced flows have been demonstrated to be reliable, studies of transient convective flows in engine compartments are not yet carried out owing to high computing demands and lack of validated work. The present work assesses the practical feasibility of applying the CFD tool at the initial stage of a vehicle development programme for investigating the thermally driven flow in an engine bay under thermal soak.A computation procedure that enables pseudo time-marching CFD simulations to be performed with significantly reduced central processing unit (CPU) time usage is proposed. The methodology was initially tested on simple geometries and then implemented for investigating a simplified half-scale underbonnet compartment. The numerical results are compared with experimental data taken with thermocouples and with particle image velocimetry (PIV).The novel computation methodology is successful in efficiently providing detailed and timeaccurate time-dependent thermal and flow predictions. Its application will extend the use of the CFD tool for transient investigations, enabling improvements to the component packaging of engine bays and the refinement of thermal management strategies with reduced need for in-territory testing.

Review of underhood aerothermal management: Towards vehicle simplified models

“…Therefore, there is an increasing need for a fast, dependable, and reliable aerothermal management design and analysis procedures to be employed at an early stage of the vehicle development program. Numerical simulations appear to be an appropriate means to satisfy these requirements and have the potential to reduce the amount of prototypes [23]. These numerical simulations concern mainly the investigation of the thermal soak phase of a vehicle where the flow is buoyancy driven [24,25], the underhood compartment thermal management of passenger cars and trucks [26], the exhaust system during cold start emissions [27], diesel engine with a dual-loop Exhaust Gas Recirculation EGR system [28], the airflow over a radiator and convex and concave tubes [29,30] and vehicle suspension system [31].…”