As the technology to generate the world's 80% power, combustion of fossil fuels will continue to play a key role in energy production over the next several decades and contributes heavily to carbon emission. In mobile internal combustion engines for road, air and water transportation and stationary gas turbines for electricity generation in power stations, the burning of fossil fuels is widely achieved by liquid fuel injection, which dictates fuel efficiency and emissions. It involves a cascade of complex multiscale, multiphysics, multiphase phenomena, and has been identified as a basic research need for these combustion devices. The need is becoming more urgent as more alternative biofuels are introduced in the fuel market, making the fuel properties more complex and the control of liquid fuel injection more difficult. Therefore, future smart engines require precise control of the injection of a broad variety of fuels that is far more subtle than what can be achieved to date.

Currently numerical research on the fuel spray process can be divided in two principal categories: (1) using an Eulerian approach to simulate primary breakup in the dense spray regime and (2) using a Lagrangian approach to simulate turbulence-combustion-droplets interaction in the dilute spray regime. However, to systematically study fuel spray atomisation and combustion cannot be achieved by either approach. To track a large amount of atomised droplets using an Eulerian approach is difficult due to the resolution requirement for small droplets and thin ligaments. For Lagrangian approaches, the widely used computational configurations are homogeneous isotropic/shear turbulence, or temporally/spatially developing mixing layers or jets laden with point-source droplets. Missing important initial conditions of the atomising spray which are determined by primary breakup in the dense spray zone, the research on spray combustion is currently in an early theoretical stage and far from the expected goal of guiding and optimising the design of fuel injection.

This project proposes an idea to bridge the gap between the two approaches to simulate fuel spray atomisation and combustion, by keeping the advantages of the two approaches and complementarily remedying their disadvantages with each other. The integrated, multiscale, hybrid Eulerian-Lagrangian simulation approach can be used to perform high-fidelity simulation of the fuel spray atomisation and combustion phenomena and investigate complex multilateral interactions among an atomising liquid-fuel jet, atomised evaporating droplets, combustion, and turbulence on current and future supercomputers.

Developing such a predictive numerical tool is an essential first step toward the goal of a complete, predictive simulation capability for the design and optimisation of fuel-efficient and clean engines. It can impact broadly the design of transportation engines including off-highway engines and help the acceleration of diverse biofuels being used in the fuel market, contributing to key emerging industries of bioenergy in the UK. A liquid spray process is also widely used in other research disciplines such as Healthcare Technologies and Advanced Manufacturing. A predictive numerical tool can contribute to improving the scientific understanding, design and control of the spray processes in these prioritised research areas.

Potential Impact:
The proposed research is directed towards the development of a predictive numerical tool that has the potential to significantly accelerate the development of cleaner and more efficient low carbon internal combustion engines. The major deliverable of the project is a multiscale simulation approach and an in-house code MultiPLESTaR that enables high-fidelity simulation of fuel spray atomisation and combustion for unveiling the complex physiochemical spray flow physics.

Improved scientific understanding of the liquid fuel injection will accelerate the development of advanced combustion concepts and technologies and the wide use of various bio-derived fuels for efficient, clean engines in order to reduce CO2 and other emissions, thus meeting the relevant emission legislations and contributing to the Department for Transport Carbon Reduction strategy.

Greater knowledge of the complex fuel spray atomisation and combustion phenomena in engines will have significant practical/technical implications in the design of fuels and fuel injection devices and processes. These scientific and technical advances are vital to control and optimise the fuel spray process and achieve more efficient and cleaner combustion in future advanced engines. Subsequently the outcomes of the research will lead to societal and environmental benefits. In addition, they will yield economic benefits by means of improved fuel efficiency and result in increased energy security by reducing the petroleum-derived fuel demands and hence the dependence on such fuels.

The project partner expects to generate know-how relating to fuel and engine system design and operation and hence the key stakeholders in this proposal will be the fuel and engine industries which will use the research outcome to help design, develop, and optimise their next-generation products to meet the targets of carbon reduction, fuel economy and stringent exhaust emissions. With public dissemination occurring throughout the project lifetime, fuel producers, engine technology designers, and other potential end-users will be exposed to the scientific outputs with little delay. This will enhance the probability of alternative applications being identified. It will also allow policy makers to make informed decisions based on good science.

The numerical methodology and code can be potentially employed in a multiplicity of industrial and residential applications such as water-injection in auto- and aero-engines to reduce emissions and noise, water-based fire suppression. More broadly, since a liquid spray process is widely used in other research disciplines such as Healthcare Technologies and Manufacturing, the new approach can benefit researchers in these prioritised research areas, promoting interdisciplinary and multidisciplinary research.

Databases of high-resolution simulations of spray atomisation will be open for access by other academics to facilitate the analysis of flow physics and development of engineering LES, RANS spray models. The PI would be pleased to share the code with other researchers for future collaboration in the field and related disciplines. The impact of the research on the careers of the RA employed on the project will be of great importance. The project will ensure the provision of high quality training to him/her who will gain knowledge and advanced skills that s/he will be able subsequently to use to make a significant contribution in a research and development environment in either academia or industry.