Technology at the heart of the latest high-tech bagless vacuum cleaners is being utilised in an attempt to clean up diesel engine emissions from older vehicles such as buses and trucks, which are threatened by legislation that becomes effective in 2000.
Final year engineering students at the University of Hull have developed a low-cost device that removes up to 50% of particulates said to pose a bigger health hazard than other exhaust constituents.
The students’ device is a single-stage cyclone that works like a spin dryer, creating a twin vortex or spiral movement that forces heavier particles down and lighter particles to rise.
Instead of spinning out water, it drives out particles of carbon and unburned fuel, leaving the cleaner exhaust gases to pass into the air.
The cyclone is said to be cheaper than other methods such as the ceramic regenerative trap. It can be retrofitted or even designed into existing replaceable mild steel exhaust/silencer systems.
The students found a lack of useful data relating to the size of the particulates. Dr Kevin Fancey, who heads the project, says this is because the emissions legislation has focused attention on weight.
The legislation will limit emissions from modern diesel engines by weight. But those who link particulates to lung cancer argue that particle size is more relevant.
Some researchers believe a single particle can cause disease, with those up to 5 m in diameter being more dangerous than larger particles, which cannot penetrate deep into the lungs.
Older diesels lend themselves to cyclone technology because they produce much larger particles than modern ones, where particle size can be less than 0.1 m equal to 300 atoms across.
The students worked with local bus company East Yorkshire Motor Services to determine the size distribution of particles from older diesel engines.
Students Paul Robinson and Niell Strickland took two years to develop the design data. The department’s electron microscope was used to measure the particles, which were trapped in wire wool. A technique called energy X-ray dispersive analysis enabled the researchers to distinguish the harmful particulates from other types of particle.
They found the median particle size to be between 2 m and 3 m, with a range of 0.3 m to 9 m.
Masters degree student Jaime Palmer Walliker then designed the aluminium cyclone, which has been tested successfully on a bus.
Next year’s students will study ways to remove the more dangerous smaller particles by adapting the cyclone to include an agglomerator.