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A novel method for the evaluation of fuel-borne catalysts effect on DPF regeneration temperature is presented. The method is simple and allows for the in-situ determination of the regeneration temperature. It consists of the engine and trap preconditioning, the trap loading cycle and the regeneration phase. The repeatability of the method is better than ±1% of average value measured. The method is capable of distinguishing very low concentrations of the metal catalyst. The application of the method with different concentrations of the same catalyst does not require the use of fresh traps. For the evaluation of different catalysts however it is recommended to use a fresh trap, since the prescribed preconditioning is not capable of eliminating the effects of the previous additive.

A test protocol, allowing for the evaluation of diesel particulate filters of different materials and of different sizes, located at various distances from the engine was developed. A total of 13 filter configurations were tested on a Euro I naturally aspirated diesel light duty truck with a fully passive trap system, utilizing only cerium-based additive in the fuel. It was proved that regeneration under constant urban driving conditions was always possible, at an exhaust gas temperature at the trap inlet in the range of 250 - 350°C. On a gravimetric basis, the efficiency of the traps tested concerning PM was in the order of 45 - 80% over the NEDC, depending on trap material and location along the exhaust pipe and reflecting the specific composition of the PM generated by the vehicle. No major effect on gaseous emissions (HC, NOx and CO) was observed.

A direct injection turbocharged passenger car with exhaust gas recirculation was equipped with a ceramic Diesel Particulate Filter (DPF) and operated on fuel doped with a cerium based additive at concentrations ranging from 50 to 400 ppm. Repeat chassis dynamometer tests were carried out using the European urban cycle for trap loading, while steady state speeds were utilized for monitoring the oxidation activity inside the loaded trap. The analysis of the results is done using a number of parameters, including a mass-in-trap indicator, which reflect the oxidation activity in the trap. Thus the regeneration area is determined experimentally and an optimum combination of parameters that may be adjusted by the electronic control unit of the engine is investigated, aimed at the safe and durable operation of the DPF, without negative effects on fuel consumption and vehicle driveability.

A light duty truck Renault Trafic with a naturally aspirated 2.5 l diesel engine was equipped with metal particulate filters of different sizes, installed at different positions along the exhaust pipe of the vehicle. The filters were operated on diesel fuel doped with a cerium based additive at concentration of 100 ppm in the fuel. Tests were carried out on chassis dynamometer using continuous repetition of the urban part of the European Driving Cycle as a « worst case » approach. Comparisons are made between the different sizes and positioning as regards both back-pressure build up and catalytic regeneration behavior. The results show that filter regeneration was always possible at continuous low speed driving, at relatively high filter back-pressure levels (i.e. high particulate accumulation in the filter), with an effect on fuel consumption.

The effect of a ceramic diesel particle trap on the size and number of particles emitted from an IDI diesel engine was investigated. Transient effects on the distribution were revealed by utilizing an Electrical Low Pressure Impactor for real time measurement of the particle distribution. A conventional and a low sulfur - low aromatics fuel were used with and without Cerium based additive. Both parameters considerably affect the number of emitted particles, while the median size, expressed as the aerodynamic diameter equivalent, is found in the range of 60 to 110nm. Furthermore, a major influence of the trap load on the total particle number was detected during the accelerations of an urban driving cycle.

A light duty truck Renault Trafic with a naturally aspirated 2.5 l engine was equipped with ceramic DPFs of different sizes, installed at different positions along the exhaust line of the vehicle. The filters were operated on diesel fuel doped with a cerium based additive at concentration of 100 ppm in the fuel. Tests were carried out on chassis dynamometer using the urban part of the new European driving cycle and the full new European Driving cycle. Comparisons are made between the different sizes and positioning as regards both back-pressure build-up and catalytic regeneration behavior. The results show that filter regeneration was always possible at continuous low speed driving, at relatively high filter back-pressure levels (i.e. high particulate accumulation in the filter), with an effect on fuel consumption.

Possible techniques to protect the filter against a failure scenario, so far reported, include filter by-passing and limiting the engine A/F ratio. Both techniques aim at controlling the oxygen content of the exhaust gas and thus reducing the oxidation rate in the filter. In this paper a new method for the protection of the trap is presented. This method, called Selective Flow Modulation (SFM) aims at controlling the reaction rate via the modulation of the exhaust gas flow through the filter. For the practical application of such a method, it is necessary to split the filter into at least two parts and to use at least one device for the flow modulation. In addition, a number of different possible SFM configurations are presented and their characteristics are analysed together with the experimental results of the technique applied on two engines, one heavy and one light duty.