Improving the Efficiency of Conventional Spark-Ignition Engines Using Octane-on-Demand Combustion. Part I: Engine Studies

Abstract

<div class="section abstract"><div class="htmlview paragraph">This paper is the first of a two part study which investigates the use of advanced combustion modes as a means of improving the efficiency and environmental impact of conventional light-duty vehicles. This first study focuses on the application of so-called Octane-on-Demand combustion, whereby the fuel anti-knock quality is customized to match the real-time requirements of an otherwise conventional spark-ignition engine. Methanol is utilized as the high octane fuel, while three alternative petroleum-derived fuels with Research octane numbers (RONs) ranging from 61 to 90 are examined as candidates for the lower octane fuel.</div><div class="htmlview paragraph">Experimental engine calibration maps are first developed to quantify the minimum amount of methanol that must be added to each lower octane fuel in order to reproduce the baseline engine performance attained on a market gasoline (RON 95). The properties of the lower octane fuel are shown to affect the engine performance significantly. In particular, the lower octane fuel indirectly defines the evolution of several key fuel properties with engine load. This synergistic relationship ultimately presents a trade-off between minimizing the fuel consumption and CO<sub>2</sub> emissions, but can also be exploited to eliminate the traditional constraints on high load engine operation.</div><div class="htmlview paragraph">Finally, the benefits and trade-offs associated with Octane-on-Demand are discussed in relation to powertrain design and emissions legislation. These benefits include several opportunities to simplify traditional aftertreatment systems, while also realizing higher pollutant conversion efficiencies. Overall, this work suggests that Octane-on-Demand can enable a degree engine performance and efficiency that is not possible with traditional gasolines, while simultaneously realizing the environmental benefits of lower octane petroleum-derived fuels that require less processing than those offered in the market today.</div></div>