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Diesel particulate filters are expected to be used on most passenger car applications designed to meet coming European emission standards, EU5 and EU6. Similar expectations hold for systems designed to meet US Tier 2 Bin 5 standards. Among the various products oxide filter materials, such as cordierite and aluminum titanate, are gaining growing interest due to their unique properties. Besides the intrinsic robustness of the filter products a well designed operating strategy is required for the successful use of filters. The operating strategy is comprised of two elements: the soot estimation and the regeneration strategy. In this paper the second element is discussed in detail by means of theoretical considerations as well as dedicated engine bench experiments. The impact the key operating variables, soot load, exhaust mass flow, oxygen content and temperature, have on the conditions inside the filter are discussed.

The accuracy of soot estimation is - besides thermal management – one of the key requirements for successful DPF applications. With the implementation of more stringent emissions regulations and requirements for fuel efficiency the importance of high quality soot mass estimation becomes even more relevant. The durability targets for T2B5 and Euro 6 require accurate soot load detection under all driving profiles and customer specific environments – from low speed delivery cycles to high speed extra urban driving profiles. The most fuel and CO2 efficient regeneration strategy relies on knowledge of the current soot mass in the DPF. This paper describes several options of soot mass estimation: From an empirical engine out emissions model, combined with a physical soot oxidation model to a physical model in which the pressure drop signal combined with other parameters is used to determine the filter load.