Miller cycle

In engineering, the Miller cycle is a thermodynamic cycle used in a type of internal combustion engine. The Miller cycle was patented by Ralph Miller, an American engineer, US patent 2817322 dated Dec 24, 1957. The engine may be two- or four-stroke and may be run on diesel fuel, gases, or dual fuel.

This type of engine was first used in ships and stationary power-generating plants, and is now used for some railway locomotives such as the GE PowerHaul. It was adapted by Mazda for their KJ-ZEM V6, used in the Millenia sedan, and in their Eunos 800 sedan (Australia) luxury cars. More recently, Subaru has combined a Miller-cycle flat-4 with a hybrid driveline for their concept "Turbo Parallel Hybrid" car, known as the Subaru B5-TPH, and Nissan has introduced a small three-cylinder engine with variable intake valve timing that claims to operate an Atkinson cycle at low load (thus the lower power density is not a handicap), or a Miller cycle when under light boost in the low-pressure, supercharged variant, returning to regular (and either suction or more strongly supercharged), more power-dense Otto cycle operation at higher loads. In the latter example, the particular nature of the Miller cycle permits the supercharged version to not only be moderately more powerful, but also claim better, almost diesel-like fuel economy with lower emissions than the (simpler, cheaper) suction-intake one - in contrast to the usual situation of supercharging causing significantly increased fuel consumption.

A traditional reciprocating internal combustion engine uses four strokes, of which two can be considered high-power: the compression stroke (high power flow from crankshaft to the charge) and power stroke (high power flow from the combustion gases to crankshaft).

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