Abstract
Reactivity Controlled Compression Ignition (RCCI) is one of the most promising solutions among the low temperature combustion concepts, in terms of thermal efficiency and pollutant emissions. However, for values of brake mean effective pressure higher than 10 bar, in-cylinder peak pressure rise rates tend to be too high, limiting the specific power of any 4-Stroke (4S) engine. Such a limitation can be canceled by moving to the 2-Stroke (2S) cycle. Among many alternatives, the “Uniflow” scavenging system with exhaust poppet valves on the cylinder head allows the designer to reproduce the same identical combustion patterns of a 4-stroke RCCI engine, while increasing the indicated power output. The goal of the paper is to explore the potential of a 2-stroke RCCI engine, on the basis of a comprehensive experimental campaign carried out on a modified automotive 2.0 L, 4-stroke, four-cylinder, four-valve diesel engine. The developed prototype can run with one cylinder operating in 4-stroke RCCI mode (gasoline–diesel), while the others work in the standard diesel mode. A One Dimensional-Computational Fluid Dynamics (1D-CFD) model has been built to predict the performance of the same prototype, when operating all four cylinders in RCCI mode. In parallel, an equivalent 2-stroke RCCI virtual engine has been developed, by means of 1D-CFD simulations and empirical assumptions. A numerical comparison between the 4S and the 2S engines is finally presented, in terms of performance and emissions at full load. The study demonstrates that a 2S RCCI engine can maintain all of the advantages of the RCCI combustion, strongly reducing the penalization in terms of performance, in comparison to a standard 4S diesel engine.
Highlights
Publisher’s Note: MDPI stays neutralAnthropogenic Greenhouse Gas (GHG) emissions are considered the major cause of the current climate changes
The results revealed that, at low load, simultaneous improvement of fuel consumption and emissions can be obtained by enhancing the homogeneity of the charge
In comparison to a conventional 4-stroke diesel engine, particular care must be devoted to the design of the exhaust valves, operating at a double frequency; specific solutions must be adopted to control the blow-by between piston and liner, as well as the wear of the piston rings, which are forced to slide on the inlet ports
Summary
Anthropogenic Greenhouse Gas (GHG) emissions are considered the major cause of the current climate changes. Fuel can be injected directly into the cylinder, without any loss at the exhaust This design, adopted on almost all of the large-bore low-speed 2-stroke engines (naval and steady plants) permits to reach excellent values of brake thermal efficiency (even higher than 50%), along with relatively high power density (in comparison to their 4-stroke counterparts) [23]. In comparison to a conventional 4-stroke diesel engine, particular care must be devoted to the design of the exhaust valves, operating at a double frequency (higher thermal and mechanical loads); specific solutions must be adopted to control the blow-by between piston and liner, as well as the wear of the piston rings, which are forced to slide on the inlet ports. A numerical comparison among the engines is presented in terms of brake performance at full load, while pollutant emissions are estimated on the basis of experimental data, collected on the 4-stroke RCCI prototype, integrated by some empirical hypotheses
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
