Reducing emissions from diesel engines can be achieved in many ways, including the use of particle traps and the precise control of the fuel-injection process. But Helmut Weissbeck, Vice President for commercial vehicle applications at Bosch, believes that employing a selective catalyst reduction (SCR) system is the best way forward because it improves fuel economy too.
In an SCR system, urea is injected into the exhaust gases from the engine. Once heated, the urea produces ammonia that then reacts to reduce Nox to elemental nitrogen. The system is mounted in the exhaust system, downstream of an oxidation catalyst, which first deals with CO and unburnt hydrocarbons.
Bosch’s own SCR system contains an engine-management unit, filter, pressure sensor and dosing module. Bosch plans to market and sell the urea solution, under the Adblue name.
Weissbeck said AdBlue would be consumed at the rate of about 5% of diesel consumption. ‘The cost of running on diesel and AdBlue would be cheaper than diesel alone,’ he said. It would allow NOx emissions to be reduced to less than 2gm/kWh.
Because 80% of long-haul trucks are refuelled at depots the infrastructure to provide AdBlue is not a problem. ‘Fleet users could start using the system now,’ said Weissbeck. But he claimed it could be available through filling stations from 2005.