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The abatement of nitrogen oxides emissions is a topic of major concern for automotive manufacturers. In addition to aftertreatment solutions such as LNT or SCR devices, the use of exhaust gas recirculation (EGR) is necessary in most of the applications to meet emissions regulations. Due to the high specific humidity of the exhaust gases, a high condensate flow may be generated if EGR gases are significantly cooled down. In the case of long-route EGR (LR-EGR) usage, this condensate flow would reach the compressor wheel. This paper explores the variables governing the condensation process and the potential effects of the liquid droplets and streams on the compressor wheel durability combining experimental and theoretical approach. For this purpose, visualization of both the condensate flow and the compressor wheel are performed. Tests are conducted in a flow test rig in which LR-EGR water content is reproduced by water injection on the hot air mass flow.

Wall-flow diesel particulate filters have become the most effective system for particulate matter abatement in Diesel engines being required for current and future emission standards fulfillment. Despite the high filtration efficiency that wall-flow DPFs exhibit their use involves a noticeable impact in fuel consumption because of the increase of the exhaust back-pressure. Additionally, the fuel economy penalty increases as the DPF becomes soot/ash loaded. This constraint demands the approach and development of new solutions to reduce the DPF pressure drop. This paper focuses on the improvement of the ratio between the pressure drop and the loading by means of pre-DPF water injection. A proper management of the water injection events is able to completely remove the dependence between these magnitudes. The test campaign and the discussion of the experimental results address how the DPF pressure drop reduction leads to benefits in engine fuel consumption.

Pre-turbo aftertreatment systems benefit from an increase of the temperature across the monolith reducing the time up to DOC light-off and reaching better conditions for passive regeneration in the DPF. The engine performance is also improved by reducing the specific fuel consumption. The pumping work diminishes because of the lower aftertreatment pressure drop due to the higher gas density. Additionally, the aftertreatment pressure drop is not multiplied by the turbine expansion ratio to set the engine back-pressure, which becomes lower. It also makes the DPF pressure drop less dependent on the soot mass loading. In this context, the traditional ratio between engine displacement and DOC & DPF volume in post-turbo aftertreatment placement needs to be reviewed in pre-turbo applications as a way to optimize savings in fuel consumption and aftertreatment manufacturing cost.