Reactivity Controlled Compression Ignition Drive Cycle Emissions and Fuel Economy Estimations Using Vehicle Systems Simulations with E30 and ULSD

Abstract

In-cylinder blending of gasoline and diesel to achieve reactivity controlled compression ignition (RCCI) has been shown to reduce NO X and PM emissions while maintaining or improving brake thermal efficiency as compared to conventional diesel combustion (CDC). The RCCI concept has an advantage over many advanced combustion strategies in that the fuel reactivity can be tailored to the engine speed and load allowing stable low-temperature combustion to be extended over more of the light-duty drive cycle load range. However, the current range of the experimental RCCI engine map investigated here does not allow for RCCI operation over the entirety of some drive cycles and may require a multi-mode strategy where the engine switches from RCCI to CDC when speed and load fall outside of the RCCI range. The potential for RCCI to reduce drive cycle fuel economy and emissions is explored here by simulating the fuel economy and emissions for a multi-mode RCCI-enabled vehicle operating over a variety of U.S. drive cycles using experimental engine maps for multi-mode RCCI with E30 and ULSD, CDC and a variety of 2009 port-fuel injected (PFI) gasoline engines ranging from 1.8L to 4.0L. Simulations are completed assuming a conventional mid-size passenger vehicle with an automatic transmission that is optimized for each engine. RCCI fuel economy simulation results are compared to the same vehicle powered by a representative 2009 PFI gasoline engine over multiple drive cycles and showing at least a 20% improvement in fuel economy over a PFI baseline. Engine-out drive cycle emissions are compared to CDC and observations regarding relative gasoline and diesel tank sizes needed for the various drive cycles are also summarized.

A Detailed Study of Boost Pressure and Injection Timing on an RCCI Engine Map Fueled with Iso-Octane and N-Heptane Fuels

“…Using multi-dimensional CFD simulations combined with engine testing, Molina et al (2015) analyzed performance and emissions of an RCCI engine at low, medium and high loads to find out the effective parameters in order to extend its operation range. (Curran et al, 2014;Splitter et al, 2011c). Splitter et al (2011a) experimentally used E85 (85% Ethanol fuel and 15% gasoline fuel) instead of gasoline in a gasoline/diesel fueled RCCI engine and reported an increase in IMEP from 14.5 bar to 16.5 bar.…”

Drive cycle simulation of high efficiency combustions on fuel economy and exhaust properties in light-duty vehicles

“…It is well known that diesel engines require complex and expensive lean exhaust afertreatment systems for NOx and PM emissions control [14][15][16]. To address aftertreatment costs, studies are exploring innovative combustion strategies which enable higher fuel efficiencies than diesel engines while simultaneously lowering engine-out emissions to reduce aftertreatment costs [17][18][19][20]. Such novel combustion modes usually involve flameless or staged fuel combustion and are known as low-temperature combustion (LTC).…”

“…The LTC strategy has many variants including homogeneous charge compression ignition (HCCI), partially-premixed charge compression ignition (PCCI), and reactivity controlled compression ignition (RCCI) [21][22][23]. While HCCI is applicable for gasoline-like fuels and PCCI is used for diesel-like fuels, RCCI is an emerging combustion strategy that utilizes in-cylinder fuel blending of low-and high-reactivity fuels (e.g., a diesel-like and gasoline-like fuel in combination) to produce low NOx and PM emissions, while maintaining higher thermal efficiency [18,19,23].…”

“…However, limited studies have addressed the impact of these combustion technologies on the fuel economy of vehicles operating over transient driving cycles [31]. In particular, there are no full vehicle experiments having been completed with RCCI to date [18]. In the reported studies, the comparisons between the PFI, lean GDI, CDC, and dual-fuel RCCI engine emissions and fuel economy were not well-addressed for both non-hybrid and hybrid LD vehicles.…”

Estudo Experimental Sobre O Impacto Do Etanol Em Misturas Diesel-Biodiesel-Etanol Nos Motores De Ignição Por Compressão

“…Kokjohn et al[41], que fazem parte de um grupo de pesquisas da universidade norte americana de Wisconsin-Madison, tem se empenhado ultimamente no estudo da referida estratégia de combustão e chegaram a batizala com o nome Reactivity Controlled Compression Ignition (RCCI). Inicialmente Kokjohn et al[41] propuseram o RCCI operando a partir da injeção indireta (PFI), vide Figura 9[42], de um combustível de baixo número de cetano, promovendo uma carga bem misturada de combustível de baixa reatividade, ar e em alguns casos gases advindos de sistemas de recirculação EGR. Já o outro combustível, de alto número de cetano (alta reatividade), deveria ser injetado diretamente por meio de injeções simples ou múltiplas durante o curso de compressão.…”