Diesel engine builders are faced with a new challenge to lower the weight of engines to increase payload while meeting rigorous durability goals for the engine. Cooling system parts represent a family of components which may be converted to lightweight metallic alloys for significant weight savings. To utilize lightweight alloys, cooling system parts must be engineered to maintain the same durability as the cast iron components they replace. For a modern high speed diesel, the Bl0 design life may be upwards of 1,280,000 kilometers which is a very aggressive target for a new component design.
A test program was planned to guide design and development of aluminum (Al) cooling system parts for a new engine. The part must exhibit no corrosion after long duration operating with acceptable coolant. This program included three major phases consisting of bench scale corrosion tests for alloy selection, component rig tests for design verification and engine testing for system reliability.
Engine testing was carried out on a 10.8 liter, 6 cylinder, turbocharged diesel engine rated 298 kw (400 hp) which was being developed with Al cooling system parts. A coolant test matrix was developed to correspond to the limits of coolant degradation that could produce corrosion in the cooling system of typical engines in the field. The coolants used in the test program ranged in composition from a recommended coolant to an aggressive coolant with no antifreeze, low levels of corrosion inhibitor, high chloride, copper ions and high pH..
Corrosion damage detected in test parts was strongly dependent on the type of coolant used during testing. The design of the part was also found to be an important variable in the observed failures. Corrosion damage that was detected may be explained in terms of the mechanisms of corrosion failure which were observed including cavitation, erosion-corrosion, and galvanic type failures.
Although the development program is not complete, preliminary results show that with the proper choice of coolant, the correct design and alloy selection, Al parts can be utilized with no degradation in performance when compared with current cast iron designs. The durability aspects of A1 cooling system parts at high mileage have not been evaluated through field testing.