Effects of fuel injection strategies in a RCCI heavy-duty diesel engine

Abstract

The main goal of the present study was to explore the impacts of various fuel injection strategies in a heavy-duty Direct Injection (DI) diesel engine operating under diesel-syngas combustion conditions computationally using CONVERGE Computational Fluid Dynamic (CFD) code. The SAGE combustion model coupled with a chemical kinetic n-heptane/toluene/PAH (Poly-Aromatic Hydro-carbons) mechanism that consisted of 71 species and 360 reactions were used to simulate the diesel-syngas combustion process and the formation and oxidation of emissions, e.g., Nitrogen Oxides (NOx), Particulate Matter (PM), Carbon Monoxide (CO), and Unburnt Hydro-Carbons (UHC). The separate effects of main (8 to 18 Crank Angle (CA) Before Top Dead Center (BTDC) with 2 CA steps) and post-injection (35 to 55 CA (After Top Dead Center) ATDC with 5 CA steps) timing of diesel fuel on the combustion characteristics and exhaust gas emissions were investigated under diesel-syngas combustion conditions. The numerical achievements revealed that the substitution part of the diesel with a CO–H2 gaseous mixture led to a considerably lower PM and UHC emissions in the exhaust gases with a CO penalty rate. Maximum Combustion Temperature (MCT) and Heat Release Rate Peak Point (HRRPP) were increased as Main-Injection Timing (MIT) was advanced. Also, advancing MIT led to a considerably higher level of NOx emissions but lower PM formation. Moreover, compared to baseline engine operating conditions, post-injection of diesel at 35 CA ATDC reduced both PM and UHC emissions simultaneously by nearly 26.5 and 89%, respectively.

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Abbreviations

ATDC:

After top dead center

BTDC:

Before top dead center

CA:

Crank angle

CFD:

Computational fluid dynamic

CO:

Carbon monoxide

DI:

Direct injection

DOI:

Duration of injection

DSC:

Diesel-syngas combustion

EGR:

Exhaust gas recirculation

EVO:

Exhaust valve opening

HRR:

Heat release rate

HRRPP:

Heat release rate peak point

ID:

Ignition delay

IMAP:

Intake manifold air pressure

IMAT:

Intake manifold air temperature

IT:

Injection timing

IVC:

Intake valve close

LTC:

Low temperature combustion

MCT:

Maximum combustion temperature

MIT:

Main-injection timing

NOx:

Nitrogen oxides

PAH:

Poly-aromatic hydrocarbon

PIP:

Post-injection pressure

PIQ:

Post-injection quantity

PIT:

Post-injection timing

PM:

Particulate matter

RCCI:

Reactivity controlled compression ignition

RNG:

Re-normalisation group

RI:

Ringing intensity

RPM:

Revolution per minute

SOI:

Start of injection

TDC:

Top dead center

UHC:

Unburnt hydro-carbon

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Acknowledgements

This research work was supported by a research grant from the Amol University of Special Modern Technologies, Amol, Iran.

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Correspondence to Bahram Jafari.

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Jafari, B., Seddiq, M. Effects of fuel injection strategies in a RCCI heavy-duty diesel engine. Sādhanā 46, 6 (2021). https://doi.org/10.1007/s12046-020-01527-7

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Keywords

  • Combustion simulation
  • RCCI engine
  • fuel injection
  • syngas
  • emissions