Title
Application of variable valve actuation strategies and direct gasoline injection schemes to reduce combustion harshness and emissions of boosted HCCI engine
Author
Hunicz, J.
Mikulski, M.
Publication year
2018
Abstract
One of the pending issues regarding Homogeneous Charge Compression Ignition (HCCI) engines is high load operation limit constrained by excessive pressure rise rates (PRRs). The present study investigates various measures to reduce combustion harness in a residual-affected HCCI engine. At the same time, the impact of those measures on efficiency and emissions is assessed. Experimental research was performed on a single cylinder engine equipped with a fully-flexible valvetrain mechanism and direct gasoline injection. The HCCI combustion mode with exhaust gas trapping was realized using negative valve overlap and fuel reforming, achieved via the injection of a portion of fuel during exhaust re-compression. Three measures are investigated for the PRR control under the same reference operating conditions, namely: (i) variable intake and exhaust valve timing, (ii) boost pressure adjustment and (iii) split fuel injection to control the amount of fuel injected for reforming. Variable exhaust valve timing enabled control of the amount of trapped residuals, and thus of the compression temperature. The reduction in the amount of trapped residuals, at elevated engine load, delays auto-ignition, which results in a simultaneous reduction of pressure rise rates and nitrogen oxides emissions. The effects of intake valve timing are much more complex, because they include the variability in the amount of intake air, the thermodynamic compression ratio as well as the in-cylinder fluid flow. It was found, however, that both early and late intake valve openings delay auto-ignition and prolong combustion. Additionally, the reduction of the amount of fuel injected during exhaust re-compression further delays combustion and reduces combustion rates. Intake pressure reduction has by far the largest effect on peak pressure reduction yet is connected with excessive NOX emissions. The research successfully identifies air-path and injection techniques, which allow for the control of combustion rates and emissions under elevated load regime, thus shorting the gap towards the real-world application of HCCI concepts.
Subject
Fluid & Solid Mechanics
PT - Power Trains
TS - Technical Sciences
Industrial Innovation
Air
Air intakes
Engine cylinders
Flow of fluids
Fuel purification
Gasoline
Ignition
Intake valves
Nitrogen oxides
Compression temperature
Experimental research
Negative valve overlap
Nitrogen oxides emission
Simultaneous reduction
Single cylinder engine
Variable valve actuation
Direct injection
Combustion
Valves
Homogeneous charge compression ignition engines
HCCI engines
Emissions
Gasoline
To reference this document use:
http://resolver.tudelft.nl/uuid:5825c962-f407-4f02-8f75-34c2495cbb02
DOI
https://doi.org/10.1115/icef2018-9625
TNO identifier
861695
Publisher
American Society of Mechanical Engineers
ISBN
9780791851982
Source
ASME 2018 Internal Combustion Engine Division Fall Technical Conference, ICEF 2018, ASME 2018 Internal Combustion Engine Division Fall Technical Conference, ICEF 2018, 4 November 2018 through 7 November 2018
Document type
conference paper