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Combustion and emissions of controlled auto-ignition engine under stratified mixture conditions

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Author: Hunicz, J. · Mikulski, M. · Rybak, A.
Type:article
Date:2018
Publisher: Institute of Physics Publishing
Source:Mitianiec, W., IOP Conference Series: Materials Science and Engineering - Scientific Conference on Automotive Vehicles and Combustion Engines, KONMOT 2018, 13 September 2018 through 14 September 2018, 4, 421
Identifier: 843693
Article number: 042028
Keywords: Direct injection · Efficiency · Engine cylinders · Exhaust gas recirculation · Exhaust gases · Fuel purification · Fuels · Mixtures · Process control · Stratified charge engines · Combustion technology · Complex relationships · Control combustion process · Controlled autoignition · Injection techniques · Mixture stratifications · Negative valve overlap · Single-cylinder research engines · Ignition

Abstract

Controlled auto-ignition (CAI) is an advanced combustion technology offering high thermal efficiency and low NOX emissions. One promising approach to achieve CAI combustion is application of negative valve overlap resulting in internal exhaust gas re-circulation. However, combustion control is still an issue which should be resolved before wide application of CAI combustion. Introduction of some degree of fuel stratification via direct fuel injection is interesting approach to control combustion process. In this study a gasoline-fuelled single-cylinder research engine was used to investigate the effects of stratification on combustion and emissions of CAI engine. The stratification was achieved using split direct fuel injection technique, where the second fuel injection controlled the degree of stratification. The results shown that variability of the second injection timing and mass of fuel injected is a viable method to control combustion on-set as well as its duration. However, the trends in both combustion and emissions were found to be non-monotonic, revealing complex relationships between mixture formation and combustion process. It has been found that small degree of mixture stratification delays combustion on-set, whereas large stratification advances combustion. The obtained results confirmed superior combustion controllability via mixture stratification, however with some limitations resulting from reduced efficiency at high degree of stratification. © Published under licence by IOP Publishing Ltd.