A New Integrated Approach to Measurements and Modelling of Combustion Generated Particulate Matter

Particulate Matter emissions are important for the health of both our planet and its population. Legislation on Particulate Matter (PM) is increasingly stringent and subject to the greatest change. However, Particulate Matter emissions are both the most difficult to measure and the most challenging to model. In simple terms, Particulate Matter is essentially soot (carbon) onto which species such as unburned hydrocarbons are adsorbed, and is intrinsic to all combustion processes.PM has been linked to global warming and serious epidemiological issues, and this has led to much regulation. Of greatest concern are the sub-micron particles that are invisible, yet it is these small particles that have the greatest deposition efficiency in the human respiratory system. While society is not yet able to replace combustion, technological developments can seek to minimise PM emissions.The complexity of measuring and modelling PM emissions means that modellers are dependent on published experimental data which can be old and incomplete. Furthermore, the modellers have no opportunity to specify the experiments. We have already collaborated on an informal basis, but without specific funding this has been very restricted. The integrated approach in this project will enable the modellers to specify the experiments, identify the most important measurements, and create a database that can be populated with the relevant experimental data. This will provide the modellers with immediate access to complete data.Oxford has a spark ignition engine with comprehensive optical access, and a range of burners: pre-mixed flat-flame (McKenna type), and co-flow (Santoro type, diffusion flame). Mass flow controllers allow us to vary the equivalence ratio of the core flow (pure fuel to the weak limit, with a choice of diluents) and the composition and flow of the annular flow (oxygen enriched or depleted air). The same fuels can be used in both the engine and burners, and in both cases the fuel composition can be controlled Measurement Capabilities - Oxford has a mix of proprietary and unique equipment for PM measurements. We can measure size distributions, mass loadings, composition, morphology and surface area. We also have a unique Differential Mobility Analyser that allows size segregation prior to PM characterisation. We have techniques for measuring temperature, as this has been identified by the modellers as of paramount importance. Most significantly, we will apply the novel technique - Laser Induced Grating Spectroscopy, LIGS temperature measurements of high accuracy and precision. In LIGS, the coherent, laser-like signal beam offers high discrimination against background scattering and luminosity to give a good signal-to-noise ratio in sooting flames. Potential exists for developing a transportable instrument for thermometry of flames in laboratory or technical combustion systems such as engines, gas turbines, incinerators etc.Computational modelling - Cambridge will create and improve computational models which describe combustion chemistry and soot particle formation. Combustion chemistry involves thousands of chemical reactions; the model must contain enough detail to describe the species which are important but must be concise enough to make numerical evaluation possible. Such models exist, but contain many parameters which need further refinement via experimental data. Modelling the formation and growth of soot particles is even more challenging. The chemical reactions between gas phase species and particle surfaces have to be combined with a population balance model to predict the particle mass and size. Eventually a detailed particle and chemistry model must be included in an engine model. These models are to be used to understand the mechanism of particle formation in an engine further and with this find operating modes which reduce particle formation and increase the efficiency of the engine.

The 'STERN REVIEW: The Economics of Climate Change' concludes that the scientific evidence is now overwhelming: climate change is a serious global threat, and it demands an urgent global response. The overall costs and risks of climate change will be equivalent to losing at least 5% of global GDP each year, now and forever. In contrast, the costs of action - reducing greenhouse gas emissions to avoid the worst impacts of climate change - can be limited to around 1% of global GDP each year. (http://www.hm-treasury.gov.uk/6520.htm HM Treasury 2006 ISBN number: 0-521-70080-9). Economic and Social Benefits - Although wind generation capacity increased by 29.9% and solar generation capacity increased by 69% in 2008, only Hydroelectricity is significant as 6.4% of the World Energy Consumption. Nuclear energy represents 5.5% of World Energy Consumption, so 88% of World Energy Consumption is from fossil fuel combustion, and in the UK 94% of energy is from fossil fuel combustion. (BP Statistical Review of World Energy, June 2009. www.bp.com/statisticalreview ) These data exclude energy from bio-fuels, but they too of course depend on combustion. Particulate Matter (PM) emissions affect climate change, but in addition they are associated with health issues. It is thus vital to reduce PM emissions from all combustion sources, and to understand how this can be achieved. The validated models to be developed here will demonstrate this understanding, and enable industry to implement the most effective strategies. The work with flames is of a fundamental nature and will be widely applicable. To demonstrate this, measurements and modelling are also being undertaken with a Spark Ignition Engine. Road transport accounts for 21% of the CO2 emissions in the UK, and about half of these are from gasoline engines. Liquid hydrocarbon fuels (including biofuels) are likely to remain the major energy source for transportation for the foreseeable future (i.e. up to 2050). Developing a trans/portable instrument based on compact Nd:YAG and DPSS lasers for LIGS thermometry will provide a commercially exploitable instrument for applications in industrial and research environments. Advisory Board The Advisory Board (comprising UK Industrialists and overseas academics) will meet every 6 months; Video Conferencing will be used to reduce overseas travel costs. A report will be presented on the overall progress, and there will be presentations on selective aspects of recent work, and there will be discussion of the detailed plan for the following 6 months. This will ensure that industry is well-informed about our work as it develops. Scientific Benefits - Results for the measurements and modelling will be published in refereed journals (Combustion and Flame, Progress in Combustion Science and Technology) and international conferences (International Combustion Symposium, SAE Congress). We will also give presentations at UnICEG, Cambridge Particles Meeting and Combustion Institute meetings + A WWW based database will be created for archiving the experimental data and making it available to other researchers. Support for collaboration that already provides a two-way flow of knowledge between academia and industry (Shell, Jaguar, Ford, Rolls-Royce, JCB), via Advisory Board meetings, UnICEG, Cambridge Particles Meeting and Combustion Institute meetings. + Maintain the current training of Graduate Students and PDRAs for careers in industry and academia.