Unified modelling framework of sub- and super- critical injection dynamics

点击翻译按钮获取中文摘要

Despite many previous (mostly experimental) efforts to characterise super-critical injection conditions, they still remain a challenging fluid dynamics problem due to the multi-scale, multi-phase character of the complex physical phenomena that governs it. This proposal aims to offer a systematic approach towards a better understanding and prediction of the transition of sub- critical to super- critical injection phenomena, combining novel state of the art simulations with experiments already performed by the University of Brighton and Sandia National Laboratories for diesel engine conditions. The model will include real gas effects and target both primary and secondary atomization regions at the limit of transition between sub- critical to super- critical conditions. Such an approach is currently lacking from commercial and open source simulation tools. The new framework will be developed within Large Eddy Simulations (LES) and will be based on the extension of ideas also used in probabilistic modelling of flame interfaces (surface density approaches). The major strength of the approach is that it does not include any a priori region-dependent assumptions for the liquid-gas volume fraction in the computational cells, and bypasses the spherical vision of the liquid structures that compose the spray. Thus, it can be applicable both to the near-nozzle and the dilute spray areas, and represent both sharp (as in the case of sub- critical injection) and diffused (more representative of super-critical conditions) interfaces. Our suggested numerical models have the potential to capture the underlying physics of the phenomena even at extreme thermodynamic conditions and therefore can play the role of "virtual experiments", providing valuable access to flow areas and conditions where real experiments face limitations. The numerical framework that will be presented in the proposed research aspires to lead to the creation of the new generation of equipment design tools that will be available to both academic and non-academic sectors and will facilitate the cost effective design of novel high pressure injection systems. Moreover, the outcomes of the research will be disseminated to the academic community through publications in high impact journals and national and international conferences as well as an outreach workshop. These could change the way we currently view the modelling of multiphase problems not only for automotive application but for other disciplines involving super-critical fluids.