Ceramic coatings—from DPFs to a steam-powered car

  • 31-Mar-2008 05:27 EDT
Zircotec 2.jpg
The Zircotec plasma spraying process creates a durable coating for diesel particulate filters.

To operate efficiently, diesel particulate filters (DPFs) need to reach their high operating temperatures quickly if they are to meet legislative requirements for reduced emissions levels. Zircotec thermal coating has been developed to reduce heat loss in diesel exhaust systems, helping DPFs to reach their optimum operating temperature faster.

Originally developed for the nuclear industry and also used by several Formula One racing teams, Zircotec claims that its system could help engine manufacturers reach Euro 5 emissions standards with proven technologies. By significantly reducing heat loss from the exhaust system, the coating has been developed to retain high exhaust gas temperatures, reducing warm-up times for aftertreatment systems, reducing the need for close coupling, and allowing more control of exhaust-gas temperatures.

Andy McCabe, Zircotec’s Technical Director, explained that the company’s technology is expected to be particularly useful for keeping DPFs at their operating temperature—increasingly important with rising exhaust gas recirculation (EGR) ratios, notably with stop-start drive cycles. “Superior temperature control will also allow reductions in the precious metal content in some catalyst applications,” McCabe said. “The problem with particulate filtration is that regeneration (the burning of collected soot) can only occur efficiently at very high temperatures. Typically, this occurs during periods of high load. In a vehicle with a mixed drive cycle, the gaps between periods of full load can be far greater than is required, leading to reduced efficiency of the trap and of the engine, due to filter blocking. Our coating can assist in solving this problem.”

The thermal coating makes it easier to find a suitable location to house the filter in a vehicle, because the distance of the filter from the engine can be increased without any significant additional heat loss from the exhaust stream, he added.

The coating is also to be used by the British Steam Car Challenge vehicle. Target speed is 320 km/h (199 mph). The Zircotec technology reduces heat loss, offering enhanced performance and helping to protect components against thermal damage. Its coatings are being used for the exhaust system, turbine inlet, internal surfaces of the boiler boxes, and heat shields. The company’s zirconia-based ceramics have a thermal conductivity of less than 1.7 W/m·K to achieve an effective thermal barrier and can be applied to carbon-fiber panels.

The Steam Car Challenge was launched in 2004, its aim to break the land speed record for steam-powered vehicles while promoting the potential of alternative fuels.

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