Computational optimization of reactivity controlled compression ignition combustion to achieve high efficiency and clean combustion

Abstract

<jats:p> One of the major limitations of reactivity controlled compression ignition is higher unburned hydrocarbon and carbon monoxide emissions and lower thermal efficiency at part load operating conditions. In the present study, a combined numerical approach using a commercial three-dimensional computational fluid dynamics code CONVERGE along with artificial neural network and genetic algorithm is presented to address the above limitation. A production light-duty diesel engine is modified to run in reactivity controlled compression ignition by replacing an existing mechanical fuel injection system with a flexible electronic port fuel injection and common rail direct injection systems. The injection schedules of port fuel injection and direct injection injectors are controlled using National Instruments port and direct injection driver modules. Upon validation of combustion and emission parameters, parametric investigations are carried out to establish the effects of direct-injected diesel fuel timing start of injection (SOI), premixed fuel ratio and intake charge temperature on the engine performance and emissions in reactivity controlled compression ignition. The results obtained show that the start of injection timing and intake charge temperature significantly influence combustion phasing, while the premixed fuel ratio controls mixture reactivity and combustion quality. By utilizing the data generated with the validated computational fluid dynamics models, the artificial neural network models are trained to predict the engine exhaust emissions and efficiency. The artificial neural network models for gross indicated efficiency and oxides of nitrogen (NO<jats:sub>x</jats:sub>) are then coupled with genetic algorithm to maximize gross indicated efficiency while keeping the NO<jats:sub>x</jats:sub> and soot emissions within Euro VI emission limits. By optimizing the start of injection timing, premixed fuel ratio and intake charge temperature simultaneously using the artificial neural network models coupled with genetic algorithm, 19% improvement in gross indicated efficiency, 60% and 64% reduction in hydrocarbon and carbon monoxide emissions, respectively, are obtained in reactivity controlled compression ignition compared to the baseline case. </jats:p>

Assessment of the impacts of combustion chamber bowl geometry and injection timing on a reactivity controlled compression ignition engine at low and high load conditions

“…36 Overall, in the RCCI engine, DIT has critical impacts on the combustion characteristics since the start of a direct injection directly controls the rate and time of the air-fuel mixing process. 37 According to numerical research by Mohammadian et al, the influence of injection timing in a singlecylinder heavy-duty RCCI engine was investigated. 38 Their findings showed that by early direct injection at -88 CA ATDC, maximum gross indicated efficiency and also, combustion efficiency was enhanced by nearly 7% and 3.7%, respectively compared to the engine baseline conditions.…”

“…36 Overall, in the RCCI engine, DIT has critical impacts on the combustion characteristics since the start of a direct injection directly controls the rate and time of the air-fuel mixing process. 37…”

Safe operation of dual-fuel engines using constrained stochastic control

“…25,26 New low temperature combustion (LTC) modes such as HCCI or reactivity controlled compression ignition (RCCI) aim to emit low NOx and low soot concentration thanks to longer ignition delays. [27][28][29] They are nevertheless limited by their MPRR levels due to the rapid auto-ignition of the mixture [30][31][32] and use to exhibit high resonance excitation. 33 Similar to knock in SI engines, the resulting pressure waves represent a source of potential damage for the engine and must be limited and controlled.…”

Influence of Pre-Turbine Small-Sized Oxidation Catalyst on Engine Performance and Emissions under Driving Conditions

“…In this context of hybridization, several advanced technologies for ICEs are available to reach near-zero CO 2 emissions while allowing for the sustenance of the automotive industry and market [5]. ICE improvements promote benefits in CO 2 [6] and pollutant emissions [7], being the exhaust aftertreatment systems (ATS) key to meet the limits on pollutant emissions in a context of highly dynamic operating conditions [8]. However, the early activation of the catalytic converters is becoming a critical challenge.…”