A novel 3D-CFD-simulation-based model to predict potential boiling-related erosion damage in engine cooling circuits

In recent years, the increasing power density of reciprocating internal combustion engines has posed significant challenges to maintain optimal temperature conditions and to preserve thermo-mechanical reliability. In order to improve the cooling circuit performance, local nucleate boiling has become a key phenomenon to promote pointwise heat transfer. However, experimental studies also revealed that, in presence of boiling, surface erosion can potentially occur in specific areas of the engine (especially the head), based on operating conditions and geometry of the cooling circuit. In this context, the development of a dedicated tool able to accurately predict the occurrence of boiling-induced erosion is essential to optimize design and thermal management of the engine, in order to mitigate the onset of potential severe damages. A 3D-CFD tool to predict damage in cooling circuits is proposed in the present work and it relies on both a conjugate heat transfer model of the engine and a novel purposely developed parameter. As for the former, it provides a detailed description of the engine and it is characterized by an accurate modelling of the boiling phenomenon. As for the latter, despite the availability of numerous erosion models in the context of cavitation, no reliable or widely accepted tool currently exists for predicting material surface erosion caused by the collapse of vapor bubbles in presence of boiling. In the paper, a model is proposed, based on the latest research findings available in literature on the vapor bubble condensation process. The model is synthetized by a novel erosion parameter, which accounts for key factors influencing the bubble collapse phenomenon, including vapor fraction, liquid subcooling level, thermal gradient and local velocity field. The higher the erosion parameter is, the higher the risk of severe damage results. The CFD tool is validated against experimental data on two different high-performance engines. The CHT model thermal field is compared to temperatures from thermocouples installed at the test bench. The predicted regions of potential boiling-induced damage, indicated by peaks of erosion parameter distribution, exhibit strong correlation with the experimental images showing the regions of severe damage. Interestingly, although the erosion parameter is developed to investigate damage in high-performance current-production reciprocating internal combustion engines, it can be applied, in principle, to any engine or cooling circuit. In addition, the implementation is straightforward as it is just a post-processing tool. Therefore, it can be applied to elaborate the results of any existing simulation.