Miller cycle

The Miller cycle ( named after the inventor Ralph Miller, who was this principle patented 1947) refers to a special control of the valve train, in which the inlet valve "too early" closes compared to the Otto - cycle process. The air charge amount is reduced by the compression pressure remains constant and the expansion ratio becomes higher. This causes an increase in efficiency in four -stroke internal combustion engines. The Miller cycle is an adaptation of the Atkinson cycle for normal crankshaft engines.

Basics

The intake valve is closed when the Miller process already during the intake stroke. So there is less air in the cylinder, as would fit. The ratio of the combustion chamber to cylinder capacity is chosen so that the same compaction pressure prevails, as in the normal four-stroke. The advantage consists in the fact that the geometric expansion can be increased, without increasing the compacting pressure. The working stroke (expansion volume) is larger than in a normal engine. This means that more expansion energy is used and consumes fuel efficient. The exhaust gas temperature is reduced and facilitates the use of a turbocharger. The charging with charge air cooling can compensate the performance loss due to the reduced cylinder filling, if not a greater engine displacement is desired. The Miller process is now often implemented with variable valve control.

Application

• 2010 Nissan, the manufacturer presented before a 1.2 - liter three- cylinder engine with the designation HR12DDR which generates 98 hp with Eaton TVS supercharger and Miller cycle. It reaches the cycle on its variable valve timing, further efficiency measures include direct injection and stop-start system. The engine is located in the summer of 2010, still in the testing phase.
• 2008 Mazda Mazda2 offered in a 1.3 -liter DOHC all-aluminum engine which works on this principle.

• The Mazda Xedos 9 worked after the closely related Atkinson cycle.
• The current Toyota Prius also uses the Atkinson cycle.
• The new Mercedes S 400 Hybrid operates on the Atkinson principle.

Atkinson cycle

The Atkinson cycle uses the same effect, the intake valve closes later but in contrast to the Otto cycle. It has its origin in the circumvention of the Otto patents. 1882 James Atkinson developed an internal combustion engine, which should not be dependent on patents Nikolaus Otto. To this end he produced a crankshaft with all four strokes are performed within one crankshaft revolution instead of the usual two in the gasoline engine. Since the crankshaft has to this effect two upward movements of the piston, he could make them different lengths. This he used to lower the compression and expansion stroke longer. This cycle was then named after him. It was not until 1947 Miller then turned to the same effect on engines with common today crankshaft. He used the valve control, or more precisely their early closing, to achieve the lower compression. Thus, the present hybrid engines use strictly speaking no Atkinson, but the Miller cycle.