The even more stringent worldwide emission legislation, the instability of the fuel price and the not very clear limit of fossil fuel reserves, push researcher to develop high efficiency and low emission technologies in the field of internal combustion engines (ICE). The use of alter-native fuels together with the adoption of alternative combustion concepts are possible routes to reach these objectives. Fuel decarbonisation and gaseous fuels are two key points for emis-sion lowering including the CO2. On this way, the dual-fuel (DF) engines for automotive ap-plication based on the use of natural gas (NG) and diesel have received increased attention in recent years [1-4]. In DF CI engines, the gaseous fuel is premixed with air in the intake mani-fold and subsequently compressed as in a conventional diesel engine. A certain amount of high-cetane liquid fuel (conventionally diesel fuel), usually called pilot, is then injected at the end of the compression stroke providing the energy to ignite the mixture and initiate the combustion. The high octane number of NG makes the fuel suitable for CI engines which usually operate with relatively high compression ratio (CR). Furthermore, NG is mainly con-stituted by methane (CH4) and has a favorable H/C ratio in terms of CO2 reduction compared to conventional fuels. From the point of view of NOx and particulate matter (PM) emissions, it was assessed that the DF combustion concept has the benefits to reduce NOx, and generally PM. From previous experiences it was evidenced that in the case of automotive DF engine operating with diesel energy substitution rate (ESR) >=50%, exhaust PM suppression at engine out is in the order of 60÷80% [5,6]. Therefore, also with high EGR, the DF engine could not match the current Euro 6 PM emission target of 5 mg/km, as clearly reported in [6]. So, the use of a diesel particulate filter (DPF) is required, even if the relevant soot load reduction re-lated to the DF operation mode could increase the interval time between two consecutive re-generations. With this premise, it appears extremely important the evaluation of the chemical, physical and morphological characteristics of the emitted PM, as well as the engine out parti-cles in terms of particle size distribution function (PSDF) and total number. Such information are of high importance for the design of tailored DPF for DF engines and their management during regeneration. They are usually available for conventional diesel engine, but literature concerning properties of the impact of DF operating mode on emitted particles is still not ful-ly exhaustive. Moreover, literature data should be representative of the dynamic operating mode typical of the automotive engines.
Chemical/physical features of particles emitted from an automotive modern dual-fuel methane-diesel engine
M Alfe';C Guido;V Gargiulo;P Napolitano;N Del Giacomo;C Beatrice
2017
Abstract
The even more stringent worldwide emission legislation, the instability of the fuel price and the not very clear limit of fossil fuel reserves, push researcher to develop high efficiency and low emission technologies in the field of internal combustion engines (ICE). The use of alter-native fuels together with the adoption of alternative combustion concepts are possible routes to reach these objectives. Fuel decarbonisation and gaseous fuels are two key points for emis-sion lowering including the CO2. On this way, the dual-fuel (DF) engines for automotive ap-plication based on the use of natural gas (NG) and diesel have received increased attention in recent years [1-4]. In DF CI engines, the gaseous fuel is premixed with air in the intake mani-fold and subsequently compressed as in a conventional diesel engine. A certain amount of high-cetane liquid fuel (conventionally diesel fuel), usually called pilot, is then injected at the end of the compression stroke providing the energy to ignite the mixture and initiate the combustion. The high octane number of NG makes the fuel suitable for CI engines which usually operate with relatively high compression ratio (CR). Furthermore, NG is mainly con-stituted by methane (CH4) and has a favorable H/C ratio in terms of CO2 reduction compared to conventional fuels. From the point of view of NOx and particulate matter (PM) emissions, it was assessed that the DF combustion concept has the benefits to reduce NOx, and generally PM. From previous experiences it was evidenced that in the case of automotive DF engine operating with diesel energy substitution rate (ESR) >=50%, exhaust PM suppression at engine out is in the order of 60÷80% [5,6]. Therefore, also with high EGR, the DF engine could not match the current Euro 6 PM emission target of 5 mg/km, as clearly reported in [6]. So, the use of a diesel particulate filter (DPF) is required, even if the relevant soot load reduction re-lated to the DF operation mode could increase the interval time between two consecutive re-generations. With this premise, it appears extremely important the evaluation of the chemical, physical and morphological characteristics of the emitted PM, as well as the engine out parti-cles in terms of particle size distribution function (PSDF) and total number. Such information are of high importance for the design of tailored DPF for DF engines and their management during regeneration. They are usually available for conventional diesel engine, but literature concerning properties of the impact of DF operating mode on emitted particles is still not ful-ly exhaustive. Moreover, literature data should be representative of the dynamic operating mode typical of the automotive engines.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
