Half the engine displacement of popular cars and light trucks would be adequate for most driving. The split engine (SE) is introduced here as a concept to improve the fuel economy of light-duty vehicles with large spark-ignition internal combustion engines. It operates with a small-displacement portion of the engine for typical driving and activates the secondary portion of the engine to assist with high-power driving. SE is different from cylinder deactivation; the two portions of the engine have independent crankshafts which connect through a one-way clutch, a mechanical diode with indexing features to achieve the correct relative phase of the engine sections. For illustration, 6- and 8-cylinder SE are proposed and simple versions are modeled analytically. The 6-cylinder SE consists of two inline 3-cylinder engines of equal or near-equal displacement. The 8-cylinder SE consists of two opposed horizontal 4-cylinder engines of the same displacement. SE and cylinder deactivation are also compared. Moments of inertia and the time to connect both engine sections smoothly are estimated. Fuel economy improvements with SE are estimated for the EPA urban and highway cycles. Fuel economy is improved about 30%, depending on the driving pattern. The emphasis is on relatively large engines in light trucks. The suggested design might be feasible at low manufacturing cost. Aside from cost, the main challenges to realization of successful split engines appear to be the complexity of two separate valve systems, suppression of vibration and noise from the primary engine with its small number of cylinders, and suppression of the shock and noise turning on and connecting the secondary module. If electronic controlled valve actuation continues to progress as it has, and as sophisticated vibration control systems advance, these two challenges diminish, and the split engine system could become a reality to provide substantial fuel efficiency improvements at a modest cost.
High fuel economy enabled by the split engine
Hohe Kraftstoffeinsparung durch Splitmotoren
2005
7 Seiten, 9 Bilder, 3 Tabellen, 14 Quellen
Aufsatz (Konferenz)
Englisch
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