Final Report Summary - TOP EXPERT (Tailored on-board activated agents production for exhaust aftertreatment performance enhancement)
The TOP-EXPERT project aimed at the selection, test and assessment of a novel, fully integrated active after-treatment system, targeted to allow compliance with future regulations, based on the use of activated chemical agents, generated on purpose, to enable and maximise the pollutant compounds abatement capabilities with particular reference to NOx emissions from diesel engines.
Two approaches towards these goals were pursued:
- Catalyst based approach: the activated chemical agents are produced by reforming diesel fuel, using an auto-thermal reforming device (hereby addressed as catalytic fuel processor (CFP)). Such activated chemical agents are injected in the exhaust line, upstream a main catalyst, in charge to exploit the activated agents: such device are called in the following catalyst based after-treatment device (CATD).
- Energy based approach: two devices are included in this system concept; the first one is an energy based fuel processor (EFP), using corona discharge generated plasma to reform the fuel in active species. The second is a microwawe resonance based cold plasma generator, used as energy based exhaust elaboration after-treatment device (EATD): this device works on the main exhaust gas stream, acting directly on gaseous (HC, CO, NOx) and solid (PM) pollutants. The processed gases, mixed with the activated agents' stream from EFP, are finally treated by an auxiliary catalyst, in charge of exploiting the reactive compounds to complete pollutants abatement.
The first part of the project was focused to provide the guidelines for an effective development work. The systems specification requirements defined at the beginning of the project has been used for the whole project duration to properly compare the effectiveness of the innovative after-treatment systems developed. In this task, a state of the art engine and vehicle was selected and characterized as study case for the systems application. The information collected from the study case characterisation was then provided in to the partnership, to start with the definition of the systems specifications for the two after-treatment concepts: the chemical and electrical based approach.
The second task was focused on the fuel processor devices development, needed for the on board production of activated species for NOx reduction; the device to be developed in this task were: CFP and EFP.
The CFP is essentially a fuel reformer catalyst based on noble metals supported onto inorganic metal oxides; an extensive lab-scale experimental campaign was carried out to optimise the catalyst formulation and select the most suitable reformer volume using a wide span of real-like parameters, to assess the CFP functional capabilities, and the strategies to drive the device itself in different situations, considering in particular the start-up and the engine transients.
The performance of the EFP as stand-alone system and combined with a catalytic reformer was investigated; the test campaign covered many aspect of the plasma technology: steady state conversion efficiency, side products especially short chain hydrocarbons, time dependence (on-off cycles) with cold and warm system and influence of fuel composition on the reforming process.
Once collected all the information coming from the test campaigns carried out onto the developed systems, it has been selected the most promising technology for the final implementation on vehicle; the selected technology was the CATD in two different configurations: CC (close-coupled) and UF (under-floor) systems. The two CATD systems have been successfully implemented on the selected demo vehicle (new Lancia Delta 2.0Mjet Euro5) with some minor modifications; moreover, a specific control box and software have been developed and installed onto the vehicle in order to properly control the CFP.
The CATDs have been tested over a wide range of working conditions: on the road in real driving conditions, stationary driving conditions over the roller test bench, European homologation cycle (NEDC). It has been demonstrated that the CFP is able to work in many driving conditions and the reforming reaction can be effectively controlled and maintained; the CC system performances in stationary conditions are interesting but not fully compliant with the expectations; while the UF system demonstrated an higher reliability in all the testing conditions reaching instantaneous NOx conversion efficiency up to 85 %. During the NEDC cycle the UF system was able to reduce the overall NOx emission below 0.08 g/km; the main drawback of such a system is the high level of the secondary emissions (mainly CO) generated during the reforming process. Another weak point of the TOP EXPERT system is the fuel penalty which is still higher than the expected target.
The final test campaign demonstrated that the CATD systems are able to work over a wide range of engine conditions controlling and maintaining the on-board diesel fuel reforming reaction, are compatible with the engine and vehicle systems and fully transparent to the vehicle user and the systems operation. The UF system demonstrated better performances than the CC one either in stationary conditions or over the homologation cycle. The main drawback of both the systems is anyway the high level of the secondary emissions (CO, HC and soot) which should be solved in order to exploit as much as possible the system performances. Finally, the preliminary cost benefit analysis showed that in comparison to a standard SCR system (HN3 based), the costs for the both the systems should be competitive and a further cost saving is expected with some improvements in the manufacturing process.
Two approaches towards these goals were pursued:
- Catalyst based approach: the activated chemical agents are produced by reforming diesel fuel, using an auto-thermal reforming device (hereby addressed as catalytic fuel processor (CFP)). Such activated chemical agents are injected in the exhaust line, upstream a main catalyst, in charge to exploit the activated agents: such device are called in the following catalyst based after-treatment device (CATD).
- Energy based approach: two devices are included in this system concept; the first one is an energy based fuel processor (EFP), using corona discharge generated plasma to reform the fuel in active species. The second is a microwawe resonance based cold plasma generator, used as energy based exhaust elaboration after-treatment device (EATD): this device works on the main exhaust gas stream, acting directly on gaseous (HC, CO, NOx) and solid (PM) pollutants. The processed gases, mixed with the activated agents' stream from EFP, are finally treated by an auxiliary catalyst, in charge of exploiting the reactive compounds to complete pollutants abatement.
The first part of the project was focused to provide the guidelines for an effective development work. The systems specification requirements defined at the beginning of the project has been used for the whole project duration to properly compare the effectiveness of the innovative after-treatment systems developed. In this task, a state of the art engine and vehicle was selected and characterized as study case for the systems application. The information collected from the study case characterisation was then provided in to the partnership, to start with the definition of the systems specifications for the two after-treatment concepts: the chemical and electrical based approach.
The second task was focused on the fuel processor devices development, needed for the on board production of activated species for NOx reduction; the device to be developed in this task were: CFP and EFP.
The CFP is essentially a fuel reformer catalyst based on noble metals supported onto inorganic metal oxides; an extensive lab-scale experimental campaign was carried out to optimise the catalyst formulation and select the most suitable reformer volume using a wide span of real-like parameters, to assess the CFP functional capabilities, and the strategies to drive the device itself in different situations, considering in particular the start-up and the engine transients.
The performance of the EFP as stand-alone system and combined with a catalytic reformer was investigated; the test campaign covered many aspect of the plasma technology: steady state conversion efficiency, side products especially short chain hydrocarbons, time dependence (on-off cycles) with cold and warm system and influence of fuel composition on the reforming process.
Once collected all the information coming from the test campaigns carried out onto the developed systems, it has been selected the most promising technology for the final implementation on vehicle; the selected technology was the CATD in two different configurations: CC (close-coupled) and UF (under-floor) systems. The two CATD systems have been successfully implemented on the selected demo vehicle (new Lancia Delta 2.0Mjet Euro5) with some minor modifications; moreover, a specific control box and software have been developed and installed onto the vehicle in order to properly control the CFP.
The CATDs have been tested over a wide range of working conditions: on the road in real driving conditions, stationary driving conditions over the roller test bench, European homologation cycle (NEDC). It has been demonstrated that the CFP is able to work in many driving conditions and the reforming reaction can be effectively controlled and maintained; the CC system performances in stationary conditions are interesting but not fully compliant with the expectations; while the UF system demonstrated an higher reliability in all the testing conditions reaching instantaneous NOx conversion efficiency up to 85 %. During the NEDC cycle the UF system was able to reduce the overall NOx emission below 0.08 g/km; the main drawback of such a system is the high level of the secondary emissions (mainly CO) generated during the reforming process. Another weak point of the TOP EXPERT system is the fuel penalty which is still higher than the expected target.
The final test campaign demonstrated that the CATD systems are able to work over a wide range of engine conditions controlling and maintaining the on-board diesel fuel reforming reaction, are compatible with the engine and vehicle systems and fully transparent to the vehicle user and the systems operation. The UF system demonstrated better performances than the CC one either in stationary conditions or over the homologation cycle. The main drawback of both the systems is anyway the high level of the secondary emissions (CO, HC and soot) which should be solved in order to exploit as much as possible the system performances. Finally, the preliminary cost benefit analysis showed that in comparison to a standard SCR system (HN3 based), the costs for the both the systems should be competitive and a further cost saving is expected with some improvements in the manufacturing process.
