First and Second Law Analyses of a Naturally-Aspirated, Miller Cycle, SI Engine with Late Intake Valve Closure 980889

A naturally-aspirated, Miller cycle, Spark-Ignition (SI) engine that controls output with variable intake valve closure is compared to a conventionally-throttled engine using computer simulation. Based on First and Second Law analyses, the two load control strategies are compared in detail through one thermodynamic cycle at light load conditions and over a wide range of loads at 2000 rpm. The Miller Cycle engine can use late intake valve closure (LIVC) to control indicated output down to 35% of the maximum, but requires supplemental throttling at lighter loads. The First Law analysis shows that the Miller cycle increases indicated thermal efficiency at light loads by as much as 6.3%, primarily due to reductions in pumping and compression work while heat transfer losses are comparable. The Second Law analysis shows that the throttling process in the conventional engine destroys up to 3% of the available energy in the fuel, and that the phasing of the heat transfer losses is more costly to its work producing potential. Overall, the availability analysis recognizes that the higher pressure in the LIVC intake manifold leads to a notable thermomechanical advantage, which the throttled engine has to overcome by consuming more chemical availability to achieve the same load.


Subscribers can view annotate, and download all of SAE's content. Learn More »


Members save up to 18% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:

A Naturally Aspirated Miller Cycle Gasoline Engine - Its Capability of Emission, Power and Fuel Economy


View Details


The Otto-Atkinson Engine - A New Concept in Automotive Economy


View Details


Development and Use of a Computer Simulation of the Turbocompounded Diesel System for Engine Performance and Component Heat Transfer Studies


View Details