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Shell is working with UK researchers to study the potentially hazardous nano-particles that are spewed out in diesel and bio-fuel engine emissions.

Although diesel engines obtain about 30 per cent better mileage and emit far less carbon dioxide than petrol engines, they can pump out up to 400 times more particulate matter. The exhaust fumes can contain a wide variety of hazardous ultra-fine and nano-particulates. These are believed to lead to a number of serious health problems, including asthma, irregular heart-beats and even premature death from heart and lung disease.

As EU emissions targets are moving the car industry towards an increasing use of bio-fuels in engines, the researchers behind this EPSRC-funded project at Brunel University believe more information about their emissions is required. Dr Lionel Ganippa said that by 2020 about 20 per cent of engines will run on bio-fuels.

'We need to think about the size of particles rather than just their mass,' he said. 'At the moment we know nothing about the size range of particles under different conditions.'

The first stage of the research will entail researchers looking at the formation of soot inside a test engine at the university's school of engineering and design laboratory. The engine has been packed with optical sensors so they can measure what is happening in the combustion chamber.

The soot particles will be measured and characterised using advanced laser diagnostics as the engine runs under different conditions and temperatures. The technology uses a laser to heat up the particles inside the engine, which then absorb the heat and emit radiation and glow brightly.

This brightness is then detected and, as each particle has different levels of cooling properties and heat resistance, each can be characterised against a database of particles.

The second stage of the system will use another laboratory-based, multi-cylinder engine that will run under the same variety of conditions as in the first test. However, this time the team will measure what is coming out of the exhaust.

One system used to measure the exhaust emissions will be a scanning mobility spectrometer, used to analyse the size distribution and concentration of the particles based on their weight.

The system passes the exhaust through an electrostatic charge and, depending on the charge, the particles are split into different sizes. They can then be counted using a range of systems including a condensation particle counter — a device that uses water to enlarge sub-micrometer particles for easy measurement.

Ganippa said the project would also investigate the effectiveness of different particulate filters.

'There are so many organic fractions that are part of the combustion process that deposit on the small particles,' he said. 'Once the exhaust gases pass through the diesel sub-particulate filter, the particles are filtered out, but not the smaller organic products. When one of these comes out of the filter it has no solid particles to condense upon and in extreme cases these fractions super- saturate and turn into dangerous nano-particles.'

The project will study the particulate matter before and after the filter, and the team is working with Johnson Matthey, a leading catalyst manufacturer, to see how these tiny dangerous particles deposit and re-form.

A third technique is also being used: a transmission electron microscope will look at the size, morphology and composition of the soot particles at the nanometre level.

Shell is providing the fuels to be tested, and Ganippa said the project could help the firm develop cleaner fuels in the future. 'There is a high level of interest at the moment in the emissions of bio-fuels. This research will also be beneficial for car manufacturers and catalyst developers.'

He added that although much of the EU's emissions regulations are based on the mass of particulate matter, the size of the particles is more important.

He said: 'These particles could be very harmful for lung function. There is a debate about how these things work, particularly as cooling processes have a real impact on how the particles are formed. This all needs to be better understood.'