91快活林

Our automotive research has led to the reduction of heavy-duty diesel engine emissions and, consequently, their negative impact on human health and the environment. Particulate matter (PM) and oxides of nitrogen (NOx) have been reduced from EuroV levels by 66 per cent and 77 per cent, respectively, and are now in line with EuroVI legislation.

Underpinning these accomplishments is original work using laser-induced incandescence (LII) to perform statistical analysis on in-cylinder soot distributions and formation rates over a wide range of diesel engine operating conditions. Our research team considered fuel atomisation optimisation to improve mixing in a collaborative project with Imperial College London, Delphi Diesel Systems and Ricardo UK and studied the influence of compression ratio and the interaction between fuel spray and piston bowl for a DTI project with Ricardo UK, Ford and Imperial College.

Collaborative work with the fuel injection system manufacturer, Delphi, identified injection strategies that form part of the Euro VI solution used by Volvo and other original equipment manufacturers (OEMs). The competitive advantage for users of this new flexible, high-pressure, Fuel Injection Equipment (F2 and F1) has been to reduce toxic emissions without a fuel economy penalty.

Our researchers have contributed to the development of an efficient, cost-effective and durable engine with environmental benefits. The economic impact of these innovations is the generation of considerable new business for our key partners.

AEC researchers have helped to develop an advanced spray-guided direct injection engine, which delivers significantly increased fuel efficiency while minimising emissions. Researchers from the Centre of Automotive Engineering collaborated successfully with Ricardo UK and PETRONAS, the Malaysian technology and energy company.

The research team focused on investigating the fundamentals of gasoline combustion using advanced analysis methods and laser diagnostic tools. Using optically accessed research engines located in the Sir Harry Ricardo Laboratories based at the university, researchers have been allowed unprecedented views into cylinders in order to analyse induction, fuel injection and combustion, validate simulations and optimise design.

The initial part of the programme enabled the successful development of a next-generation stratified charge combustion system based on spray-guided fuel injection (SGDI) with up to five injections per cycle. Subsequent research work on the multi-cylinder turbo-charged SGDI (T-SGDI) research engine has demonstrated that fuel consumption benefits were significantly enhanced through boosting, with a best brake specific fuel consumption (BSFC) of 203 grams per kilowatt hour (g/kWh) being achieved at 2250 revolutions per minute (rev/min) and 13 bar brake mean effective pressures (BMEP).

Further research led to insights that enabled the broadening of the stable combustion range for unthrottled, stratified operation of the ‘third- generation’ spray guided direct injection (SGDI) engine, incorporating piezoelectric fuel injectors, variable valve actuation (VVA) and advanced ignition systems.

Multiple fuel injection strategies were used to increase the unthrottled operating range, leading to further improvements in fuel economy. However, careful optimisation of these strategies is essential to ensure that benefits are maintained while further minimising emissions within combustion stability limits and consumer driveability demands.

One of the key aspects of the T-SGDI combustion system is the use of a multiple injection strategy. Whereas this approach is used effectively in modern diesels to control combustion rate, the T-SGDI combustion system uses multiple injections to limit spray penetration and hence avoid wall wetting. If optimised appropriately across a wide range of operating conditions, as in the T-SGDI system, the approach allows a stoichiometric mix to be focused in the region of the spark plug immediately prior to ignition. In addition to enabling fuel economy benefits to approach the theoretical optimum through unthrottled operation, the concept also offers enhanced exhaust gas recirculation (EGR) tolerance and is inherently low in nitric oxide and nitrogen dioxide (NOx).

Advanced Engineering Centre researchers have teamed up with industry and academics in Russia, Italy and France in a £1.3 million project to develop new understanding of fuel sprays. The research will focus on microscopic fuel droplets as they reach the combustion chamber. Current thinking is based on the premise that droplets are spherical but the new research shows that there are different shapes and it is believed that improving understanding about the processes involved will lead towards cleaner and more efficient fuels and combustion.

The complexity of the processes involved in the atomisation of diesel fuels is such that many facets involved are still not understood. The morphological composition of a typical diesel spray includes structures such as ligaments, amorphous and spherical droplets, but the quantity of fuel occupied by perfectly spherical droplets can represent a small proportion of the total injected volume. These relatively large non-spherical structures have never been thoroughly investigated and documented in high-pressure sprays, even though the increase in heat transfer surface area of deformed droplets is an influential factor for predicting the correct trend of evaporating diesel sprays. Consequently, theoretical models for liquid fuel atomisation and vaporisation are based on a number of simplifying hypotheses including the assumption of dispersed spherical droplets.

Our research initiates a step change in the description of petroleum and bio fuel spray formation by developing diagnostics and numerical models specifically focused on non-spherical droplets and ligaments. Our approach builds upon recent advances with microscopic imaging to build novel diagnostics and algorithms that can measure the shape, size, velocity and gaseous surrounding of individual droplets and ligaments and provide more information about spray breakup, heating and evaporation. The models will then be implemented into computational fluid dynamics (CFD) codes to simulate spray mixing under modern engine conditions, and generate information where optical diagnostics cannot be applied.

The 'Investigation of Non-Spherical Droplets in High-Pressure Fuel Sprays' research began in October 2013 and funding has come mainly from the government's Engineering and Physical Sciences Research Council (EPSRC), with a financial and technical contribution from BP. We are working with industrial partners and international experts from the University of Bergamo, CORIA, and Moscow State University to establish a unique world leading research capability with potential impact for numerous practical spray applications.

We constantly strive to develop models to improve understanding about the complex processes taking place within engines. By building on our previous discoveries, we create new models, which take previously ignored, important physical parameters into account, revealing more about engine potential and informing innovation to optimise performance and reduce emissions.

Our current molecular dynamics project focuses on the development of new models for the analysis of diesel fuel droplet heating and evaporation under realistic engine conditions. In contrast to most previously developed models, the kinetic effects are taken into account alongside the effects of temperature gradient and recirculation inside droplets and the effects of the moving interface during the evaporation process. We believe that this is the first research into this area.

We are developing a new hybrid quantum mechanics/molecular dynamics (QM/MD) model for the simulation of complex hydrocarbon molecules and the application of this model to the simulation of n-dodecane and a mixture of n-dodecane and dipropylbenzene molecules in diesel engine conditions. The solution of the time independent Schrodinger equation allows us to obtain the equilibrium geometry of a molecule or an ensemble of molecules, and to calculate the potential energy for any position of atoms and electrons in the system. This approach gives us the potential energy of interacting molecules as a function of their geometry. Comparing the energy for interacting individual carbon and hydrogen atoms and molecules with the interaction energy calculated by the conventional MD approach (taking into account the internal degrees of freedom of molecules) for the same inter-atomic distances allows us to analyse the differences in the QM and classical potentials.

Our results are used to calculate the corrections for the potentials used in the classical MD calculations. The new hybrid model will be used for the analysis of the dynamics of n-dodecane molecules in liquid and gas phases and at the liquid/gas interface, using techniques developed during the work on a previous Engineering and Physical Sciences Research Council (EPSRC) funded project. We intend to establish the range of applicability of the conventional MD approach. A new approximate method of taking into account the QM corrections to the classical results will be developed. In addition, the previously developed kinetic model, taking into account the presence of two components (fuel vapour and air) in the kinetic region is generalised to take into account the presence of the three components (two species of fuel and one of air).

These state-of-the-art models enable accurate prediction of fuel evaporation and mixing inside the engine, which in turn enable the prediction of the onset and phasing of combustion accurately. These advances improve the prediction and simulations tools and allow engineers to optimise design of more efficient, cleaner diesel engines.

This is a collaborative area involving visiting researchers bringing internationally-recognised expertise to our pioneering research.

Vortex ring-like structures occur widely in two-phase mixtures in a range of systems, such as gasoline engines. These structures have an impact on the mixture preparation process in the combustion chamber and it is critical to analyse the activity within the engine and explore its implications.

Appropriate mathematical models allow engineers to rapidly test novel ways of optimising and improving engineering systems before resorting to costly experimental evaluation of new technologies.

Our research investigates the applicability and efficiency of using the full Lagrangian approach (also known as the Osiptsov-Lagrangian method). We are applying this approach in the modelling of three-dimensional processes within a Computational Fluid Dynamics (CFD) framework. In addition, we are exploring the construction of new mathematical models of vortex ring-like structures to take additional complications, such as the effect of an elliptical core, into account.

This new approach to modelling multiphase flows will incorporate the jet and droplet break-up models developed through another EPSRC project. A feasibility study will also be performed into modelling vortex rings based on the combination of the full Lagrangian approach for the dispersed phase and the vortex method for the carrier phase, to examine the advantages and limitations of the different mathematical approaches.

Finally, predictions from numerical and analytical models will be validated against in-house experimental results obtained in an optical gasoline engine using our advanced laser diagnostic techniques.

Working together with expert international consultants, we are developing a qualitatively new level of physical and mathematical models to further understanding about the impact and implications of vortex rings on engine performance.

These models will contribute much needed understanding about the fundamentals of fuel mixing in new generation spray-guided engines, thus enabling the optimisation of fuel injection strategies.

The overriding objective of our research is to find innovative ways to reduce fuel consumption and CO₂ emissions while improving performance and reliability. The global market for Heavy Duty Vehicles is expected to grow from 2.7 million to 3.6 million vehicles from 2013 to 2020. To date, there is no compulsory legislation to reduce CO₂ emissions for these vehicles, and yet, if we are able to develop more efficient engines, the probable environmental and commercial gains are significant.

Our research focuses on the development of a split cycle engine to address the needs of this sector. This shift in engine technology has the potential to radically increase the indicated thermal efficiency of a reciprocating internal combustion engine (ICE). The previous 'Cool-R' feasibility study, completed in December 2012, suggested that the novel application of cryogen injection and isothermal compression, along with the recuperation of exhaust heat, offered the potential for a game-changing level of indicated thermal efficiency of over 60 per cent for heavy duty diesel engine on-highway applications.

Together, with our partners Ricardo and Hiflux Limited, our work addresses the key technical issues to prepare for the successful migration of this technology from feasibility study to systems prototype. This innovation could potentially be applied to the numerically smaller but higher value marine and genset markets, delivering substantial reductions in CO₂ emissions and fuel savings in road, rail and marine freight.

Return on investment - environmentally, through reduced emissions, and commercially - through the sale of new technology through the supply chain, is predicted to be high. Placing the UK at the forefront of delivering unbeatable efficiency with advanced engineering will ensure we remain internationally competitive and address energy security concerns.