n. 12/2023 73 TECHNOLOGY mente un combustibile piuttosto critico come il biogas tal quale, questi motori prevedono un funzionamento di tipo continuo (h 24/7, che evita quindi del tutto la problematica fase iniziale di riscaldamento), un regime di funzionamento costante a 1.500 giri/min circa per un rendimento ottimizzato, la dotazione di un turbocompressore a due stadi, una camera di pre-combustione spurgata in posizione centrale a bassa pressione e con energia di accensione della candela amplificata e infine un dosaggio gas a controllo elettronico di elevata precisione. Molto meno critico nei motori a ciclo otto è l’impiego del metano, che in ambito agricolo ha origine proprio dal biogas adeguatamente depurato, per ottenere così il bio-metano, di recente diventato un combustibile interessante anche per l’azionamento dei trattori. A tale proposito, New Holland ha sviluppato e perfezionato il T6.180 Methane Power da 175 Cv, un modello che monta il motore NEF a 6 cilindri da 6.700 cm³ di cilindrata, appositamente messo a punto is rapeseed oil due to its lower viscosity than other oils, which is still significantly higher than that of diesel fuel. It is still possible to fuel diesel engines, even modern ones, with vegetable oil, albeit with necessary modifications, minor or medium. Indirect-injection models can be fueled with significant percentages of oil mixed (up to 50 percent) with diesel fuel by changing the pre-ignition glow plugs, injectors and the oil heating circuit, which, moreover, can be used pure up to about 10°C ambient temperature and together with diesel fuel for lower temperatures. Conversely, common rail direct injection engines require the installation of a real secondary tank for diesel fuel, used to start, warm up and shut down the engine, which can run on oil alone when hot. Biogas, methane and biomethane. Primarily interested in this group of fuels are endothermic Otto-cycle engines. It is, therefore, a relatively new strand for the agricultural field, dominated as is known by the diesel cycle engine. Direct biogas power is an established feature of the large CHP (Combined Heat and Power) engines that are a key part of generator sets coupled to anaerobic digesters. To be able to handle a rather critical fuel such as biogas adequately, these engines provide for a continuous type of operation (h 24/7, thus avoiding the problematic initial warm-up phase altogether), a constant operating speed of about 1,500 rpm for optimized efficiency, the equipment of a two-stage turbocharger, a purged pre-combustion chamber in a low-pressure central position and with amplified spark plug ignition energy, and finally a highly accurate electronically controlled gas metering. Considerably less critical in Otto-cycle engines is the use of methane, which in agriculture originates precisely from propNew Holland ha sviluppato il T6.180 Methane Power da 175 Cv, un trattore che monta un motore NEF alimentato a (bio)metano New Holland has developed the 175-Hp T6.180 Methane Power, a tractor with a NEF engine powered by (bio)methane John Deere ha sviluppato un motore prototipale da 9.000 cm³ di cilindrata, compatibile con alimentazione a etanolo al 100% John Deere has developed a prototype 9,000 cm³ displacement engine compatible with 100% ethanol fueling
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