PSI - Issue 12

Francesco Mocera et al. / Procedia Structural Integrity 12 (2018) 213–223 Author name / Structural Integrity Procedia 00 (2018) 000–000

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• loading and handling machines; • construction machines; • agricultural and farming machines; • rail vehicles and ferries for inland navigation.

NRMMs regulations cover machines with a wide range of application fields leading to a not so easy work to do for power unit manufacturers in terms performance and emissions optimization. The di ff erent mission profiles to which the same thermal engine could be subjected do not allow a fully optimized design for the specific solutions both in terms of performance and emissions. Emissions regulations cover several kind of pollutants: carbon monoxide (CO), unburnt hydrocarbons (HC), several types of nitrogen oxides (NO x ) and carbon based particulate matter (measured as PM - particulate matter or PN - Particles number) (Res¸itogˇ lu, 2015). To manage the emission of such a variety of chemical compounds, specific combustion strategies and a proper after-treatment of exhaust gas must be considered. These, usually tends to go against the pure power performance of the same unit. If Diesel engines are considered, the main tools for CO and HC emissions management are the DOCs (Diesel Oxidation Catalysts) which converts hydrocarbons and carbon monoxides mainly into H 2 O, CO 2 and H 2 SO 4 . Then, there are three main strategies for NO x management: trap systems (LNT - Lean NOx Trap), recirculation systems (EGR - Exhaust Gas Recirculation) and selective reductions systems (SCR - Selective Catalytic Reduction). LNT systems usually store nitrogen oxides during high production windows of the engine operating conditions, to release them during lower production working conditions. EGR systems send back again exhaust gas into the combustion chamber to increase its temperature and decrease the amount of free oxygen available. Lastly, SCR systems use specific chemical reactions involving ammo niac or urea to decrease the amount of free oxygen available in the exhaust gas (decreasing the amount of armful reactions), converting NO x into N 2 and H 2 O. For particulate matter treatment, the main adopted technique consists in the use of special filters (DPF - Diesel Particulate Filter) which trap carbon based particles available in the exhaust gas. This regulations framework requires lot of e ff orts on the manufacturers side to integrate on their vehicles all the neces sary exhaust after-treatment systems. Not being able to satisfy these requirements means not being allowed to sell their machines on the market. With the increase of the constraints required by law, the size of the required after-treatment systems has grown accordingly. This is one of the reasons why several manufacturers have recently explored alter native solutions to post combustion treatments systems. There are two possible ways to reduce pollutant emissions: increase the overall e ffi ciency both on the power unit and vehicle side but also design engines able to output the same amount of power but with smaller engines (downsizing) (Katrasˇnik, 2007). The former consists in being able to ac complish a task with lower fuel consumptions, decreasing the amount of pollutants per task. The latter can be also considered as a consequence of the first point. Working machines usually are equipped with oversized engines to meet all the possible working scenarios. This translates to a higher fuel consumption average compared with an optimized power unit. Engine downsizing aim to obtain the same performance of a traditional power unit in a more e ffi cient way. Traditional thermal engines are a well consolidated technology but with a limited improvement window left. This is the reason why also in the NRMM field new hybrid electrified architectures started to be investigated (Soma`, 2017). Several NRMM manufacturers presented these years hybrid - electric architectures for their traditional machines (La junen, 2018). The main field of application of the machine strongly a ff ects the electrified solution. In the case of hybrid architectures, series hybrid, parallel hybrid and power split solution have been explored by manufacturer to find the best one that fit their specific case. Some of them have also considered full electric solutions. There is no a best solution in absolute terms due to the high peculiarities of each application. Usually hybrid solutions seem to best fit performance and costs requirements taking into account the state of the art of the current technology. Sometimes, specific application can also allow for full electric solutions. This is the case of the self propelled vertical feed mixer considered in this work. An extensive experimental campaign allowed for working cycle identification of such kind of machines leading to the main requirements for the new electrified architecture. The join e ff orts with the italian man ufacturer Supertino Srl allowed to study the machine on the field, highlighting the critical aspects of each working phase. In the following sections, the main design steps will be showed starting from the definition of the machine and its working cycle leading to the analysis of experimental results.