This project aims to develop fundamental understanding and new computational models for the complex problem of turbulence and mixing in high-speed liquid jets at the vicinity of Mach 1. The understanding of liquid jet behaviour is of critical importance in the design and development of new automotive propulsion technologies such as the recuperated split cycle engine. The project will focus on the fundamental fluid mechanics, development of a coherent framework for describing and modelling unsteady supercritical flow, and implementation of a practical simulation methodology for the air induction process in the engine. The research will take place within a group in the Advanced Engineering Centre at the University of Brighton, and will be supported by experimental research funded by Dolphin N2.
The project will consist of 3 phases:
Phase 1: Develop fundamental understanding of ultra-high speed liquid jet behaviour in a gaseous environment, and the interaction of the jet with the surrounding turbulence. Although liquid jets have been studied extensively, in reality there are many knowledge gaps in respect to the jet behaviour and modelling at ultra-high speeds that cause compressibility effects become important. The work in this phase will use large eddy simulation (LES) to inform understanding of the required jet behaviour, and the data obtained will be used to develop Reynolds-averaged Navier-Stokes (RANS) turbulence models which are able to accurately capture the observed jet behaviour.
Phase 2: Liquid jet interaction with high-speed air jets will be investigated as a means to control the turbulent mixing in order to improve atomisation. RANS models developed in phase 1 will be applied, and if necessary, adjusted to account for jet-to-jet interaction by comparison with LES data. Studies on flow and spray fields will be performed under various Mach numbers, injection positions, and injection angles. Modelling in phase 1 and 2 will be based on the open source computational fluid dynamics software OpenFOAM.
Phase 3: The third phase of the project will involve the implementation of the understanding and modelling from phase 1 and 2 to real life applications. One of the applications that will be considered is the recuperated split cycle engine because of the in-house experimental data available for validation. The recuperated split cycle engine has demonstrated high efficiency and ultra-low emissions on liquid diesel fuels. Through a novel combustion focused design methodology, a combination of fast mixing of the oxidant and reductants with low temperature combustion chemistry achieves thermodynamic conditions that suppress the formation of oxides of nitrogen. The air induction process in a split cycle engine is fundamentally different to conventional engines, with the charge air starting at a supercritical state and high-pressure ratios across the valves resulting in choked flow and the formation of a supersonic air jet. This presents significant modelling challenges and requires a fundamentally new approach to how the air induction process will be modelled. During this phase of the project the models from phase 1 and 2 will also be transferred to the CONVERGE software which allows for more realistic geometries to be simulated.
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