Paul Joseph Tennison

NOx Control Development with Urea SCR on a Diesel Passenger Car

Diesel vehicles have significant advantages over their gasoline counterparts including a more efficient engine, higher fuel economy, and lower emissions of HC, CO, and CO 2 . However, NO x control is more difficult on a diesel because of the high O 2 concentration in the exhaust, making conventional three-way catalysts ineffective. Two current available technologies for continuous NO x reduction onboard diesel vehicles are Selective Catalytic Reduction (SCR) using aqueous urea and lean NO x trap (LNT) catalysts. This paper discusses an application with SCR. SCR with ammonia has been used for many years at stationary sources. Aqueous urea is a convenient way to deliver ammonia onboard a vehicle and high NO x efficiencies have been shown in past work by Ford and others using urea. Tailpipe NO x emissions from a modified European production level 1.8L diesel Ford Focus TDCi were reduced to the range of ULEVII levels (0.05 g/mi NO x ) with a green catalyst system. The green system also had results within the Tier 2 SFTP US06 standard (0.14 g/mi NMHC+NO x ). An oxidation catalyst was used to convert engine-out HC and CO upstream of the urea SCR system. Aqueous urea was added to the exhaust using a Ford-developed air-assisted injection system. A base metal/zeolite SCR catalyst utilized the added reductant to convert NOx to N 2 under lean conditions.

Influence of mileage accumulation on the particle mass and number emissions of two gasoline direct injection vehicles.

Gasoline direct injection (GDI) is a new engine technology intended to improve fuel economy and greenhouse gas emissions as required by recently enacted legislative and environmental regulations. The development of this technology must also ensure that these vehicles meet new LEV III and Tier 3 emissions standards as they phase in between 2017 and 2021. The aim of the present paper is to examine, at least for a small set, how the PM emissions from GDI vehicles change over their lifetime. The paper reports particle mass and number emissions of two GDI vehicles as a function of mileage up to 150K miles. These vehicles exhibit PM emissions that are near or below the upcoming 3 mg/mi FTP and 10 mg/mi US06 mass standards with little, if any, deterioration over 150K miles. Particle number emissions roughly follow the previously observed 2 × 10(12) particles/mg correlation between solid particle number and PM mass. They remained between the interim and final EU stage 6 solid particle count standard for gasoline vehicles throughout the mileage accumulation study. These examples demonstrate feasibility to meet near-term 3 mg/mi and interim EU solid particle number standards, but continued development is needed to ensure that this continues as further fuel economy improvements are made.