Assessment by means of gas dynamic modelling of a pre-turbo diesel particulate filter configuration in a turbocharged HSDI diesel engine under full-load transient operation

Diesel particulate filters (DPF) are becoming a standard technology in diesel engines because of the need for compliance with forthcoming regulations regarding soot emissions. When a great degree of maturity in management of filtration and regeneration has been attained, the influence of the DPF placement on the engine performance emerges as a key issue to be properly addressed. The novelty of this work leads to the study of an unusual location of an aftertreatment device in the architecture of the turbocharged diesel engine exhaust line. The problem of the pre-turbo DPF placement is tackled comparing the engine response under full-load transient operation as opposed to the traditional DPF location downstream of the turbine. The study has been performed on the basis of a gas dynamic simulation of the engine, which has been validated with experimental data obtained under steady-state and transient conditions. The DPF response has been simulated with a model able to deal with the characteristic highly pulsating flow upstream of the turbine. Several levels of DPF soot loading have been considered to represent fully the most exigent conditions in terms of performance requirements. As a result, the main physical phenomena controlling the engine and DPF response and interaction have been identified. Placing the DPF upstream of the turbine will lead to a number of important advantages, owing to the continuous regeneration mode at which the DPF will operate, the lower pressure drop in the DPF, and the thermal energy storage in the DPF, which is very useful to mitigate ‘turbocharger lag’ during engine transient operation. These three effects have been evidenced with calculations performed using the validated model and the results have been fully analysed and discussed.

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