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Based on the authors' knowledge, in the current literature, a model able to simultaneously and properly reproduce both the engine operating parameters, including the intake valve strategy (EIVC, conventional Full Lift (FL) and LIVC), and the engine geometrical parameters is still missing.
This system, based on an electrohydraulic VVA device, allows a versatile control of the closure angle, so to realize both EIVC and LIVC strategies.
[3.] Li, T., Gao, Y., Wang, J., and Chen, Z., "The Miller Cycle Effects on Improvement of Fuel Economy in a Highly Boosted, High Compression Ratio, Direct-Injection Gasoline Engine: EIVC vs.
A promising technology for the improvement of engine efficiency and the reduction of pollutant emissions are Miller cycles, which utilize intake valve lift curves that are characterized by valve closing significantly before bottom dead center (early intake valve closing - EIVC) or thereafter (late intake valve closing - LIVC).
A first Miller concept with EIVC was introduced in 1947 to reduce compression work due to an internal cooling effect .
In early intake valve closing Miller cycle (EIVC), the descent of the piston creates a vacuum inside the cylinder, achieving the manifold pressure somewhere during compression, near the position where the intake valve was closed on the downward movement of the piston.
In , Audi shows a significant fuel economy improvement for the 2.0L TFSI with Miller cycle, implemented by means of the EIVC, in which, some additional gas expansion occurs, which helps reducing in-cylinder temperatures.
From engine operation point of view, the low-load operating points are commonly optimized for fuel consumption and therefore work with early IVC (EIVC) which inevitably compromises the intake-induced charge motion and, consequently, deteriorates the mixing capability and turbulence level to the extent near the combustion stability limit.
The reason is that the intake phase is heavily reduced by the relatively low intake valve lift and extreme EIVC, and more importantly, that the piston crown shape favors the anticlockwise flow motion when moving downwards.
One of the key challenges arising from the application of EIVC is the impact on air motion.
The use of early intake valve closure (EIVC) strategy has shown to promote an initial increase in tumble motion near BDC.
Looking at [L.sub.I] evolutions (Figure 16a, 17, 18, Figure 19a), some differences during early stage of intake phase appear among cases with an EIVC strategy and the one with a conventional full lift profile.
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