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Cavitation bubble cloud dynamics and surface erosion in high pressure fuel systems for medium/heavy duty Diesel engines (CavFuelSystem)
Start date: Feb 16, 2014, End date: Feb 15, 2017 PROJECT  FINISHED 

The medium/heavy duty Diesel engine industry is facing new challenges for meeting the forthcoming emission regulations. Injection pressure reaching 3000bar combined with multiple injection strategies can drastically reduce the NOx/PM trade-off and allow use of less demanding aftertreatment systems for meeting the set legislations. At the same time, use of commercial Diesel engines is expected to double over the next few decades. Cavitation erosion can affect the durability of the injection system to levels that replacement of mechanical parts only after hours of operation is demanded. The proposed programme will assist in the understanding of such flow effects using thoroughly validated CFD models and assisted by detailed experimental data as well as industrial input. The fundamental process that will be thoroughly investigated is the collapse of cavitation bubble cloud and the erosion it induces on solid surfaces. This expertise has been developed at the outgoing host institution, NTU in Singapore where the applicant will develop and validate a simulation model for such effects. Upon return back to Europe, the numerical model will be implemented into the CFD code of the return host and which simulates the macroscopic cavitating flow development within fuel injection systems. Under the premises of the International Institute of Cavitation Research, the applicant will consider with the new model effects not captured so far but believed to be of imperative importance: the prediction of cavitation surface erosion caused by sudden bubble collapse at pressure up to 3000bar and temperatures reaching locally more than 450oC. This excessive heating is produced during the fast acceleration of the fuel as it flows through the injection holes and can result to flow boiling. Thus, it alters the heat transfer characteristics between the flowing fluid and the metal of the injector. Model validation will be performed against field data from injector’s durability tests.

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