Project: Direct Numerical Simulations of Transient Turbulent Autoigniting Jets

Prace Call: 17th
ID: 2018184434, Leader: Christos Frouzakis
Affiliation: Swiss Federal Insitute of Technology Zurich, CH
Research Field: Engineering
Collaborators: Miriam Rabacal Swiss Federal Insitute of Technology Zurich CH , George Giannakopoulos Swiss Federal Insitute of Technology Zurich CH
Resource Awarded: 64.6 Mil. core hours on Marconi - KNL

Abstract

The transient nature of starting jets has a strong impact on the entrainment of ambient fluid in the near field, enhancing significantly the mixing of the jet with the ambient fluid. The increasing fuel/air interface and the enhanced mixing facilitate the initiation of the chemical reactions that can lead to autoignition, typically at multiple locations, and propagation of flames from the ignition kernels to consume the injected fuel. This subject is important for the development of innovative injection and ignition systems for internal combustion engines (ICEs) for the use of low-carbon alternative fuels towards the process of decarbonisation of the transportation sector, and heat and power production based in ICE technology. The objective of the proposed work is to provide new insights into the transient flow, mixing and turbulence-chemistry interactions in transient turbulent autoigniting jets at elevated pressures. Direct Numerical Simulations will be used to provide the complete description of the flow and chemistry, and generate much needed high resolution datasets for the development of better models for turbulent autoignition. The DNS code developed at the Aerothermochemistry and Combustion Systems Laboratory (LAV) for the direct numerical simulation of low Mach number reactive flows, based on the open source spectral element solver Nek5000, will be used to study two cases of relevance to compression ignition engines with direct gas injection: while in conventional engines combustion occurs during the jet acceleration or constant injection rate phases, the low temperature strategies employed in modern engines result in delayed autoignition and combustion during the deceleration phase. The proposed simulations will enhance the in-depth understanding of the role of the flow dynamics during the different phases of injection on the jet penetration and angle, on the transient rate of mixing and entrainment, and on the processes and local conditions leading to ignition kernel formation and appearance and propagation of the ensuing flames.