Consideration of Fluid Velocity Effects in the Design and Development of Aluminum Cooling System Components for Heavy Duty Diesel Engines 1999-01-0128

In the design of aluminum (Al) cooling system components for heavy duty diesel engines, coolant flow velocities are critical to the durability of the parts. The geometries of the individual component parts used in the system must be designed to minimize turbulence which will affect the rate and type of corrosion. In addition, flow passages must be “sized” to maintain coolant velocities below a critical value. In high velocity flow, a combination of the mechanical damage produced by the impingement of a liquid on a metal surface and the inherent corrodibility of the metal may result in erosion-corrosion and impingement attack. Aluminum alloys are very prone to this type of corrosion damage because of the low inherent hardness of the material as compared to other alloy systems.

The development of aluminum cooling system parts for a new 15 liter diesel engine was undertaken to lower weight and make a more compact design for the engine profile. Alloy selection for the cooling system components was based in part on flow studies conducted in a closed loop, flow test stand to study weight loss for candidate Al casting alloys. The choice of coolant velocities for the flow studies was predicated on calculated velocities in the individual cooling system components based on CFD analysis. Multiple Computational Fluid Dynamic (CFD) analyses were completed on two individual cooling system components where aluminum castings were being considered as replacements for gray cast iron. The studies were initiated in order to predict where the local velocities within the components would exceed the critical level, and thus be prone to accelerated erosion-corrosion effects.

Erosion-corrosion damage is shown to be a function of bulk flow velocity, type of coolant as well as the angle of attack of the fluid stream with the casting wall surface.