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Ethanol-Diesel Fumigation in a Multi-Cylinder Engine

Författare:
Publiceringsår: 2008
Språk: Engelska
Publikation/Tidskrift/Serie: SAE technical paper series
Dokumenttyp: Konferensbidrag

Sammanfattning

Fumigation was studied in a 12 L six-cylinder heavy-duty
engine. Port-injected ethanol was ignited with a small
amount of diesel injected into the cylinder. The setup
left much freedom for influencing the combustion process,
and the aim of this study was to find operation modes that
result in a combustion resembling that of a homogeneous
charge compression ignition (HCCI) engine with high efficiency
and low NOx emissions. Igniting the ethanol-air
mixture using direct-injected diesel has attractive properties
compared to traditional HCCI operation where the
ethanol is ignited by pressure alone. No preheating of the
mixture is required, and the amount of diesel injected can
be used to control the heat release rate. The two fuel injection
systems provide a larger flexibility in extending the
HCCI operating range to low and high loads.
It was shown that cylinder-to-cylinder variations present
a considerable challenge for this type of combustion. By
using closed-loop cylinder-individual control based on incylinder
pressure sensors, combustion was successfully
harmonized between the cylinders.
Successful fumigation operation was verified up to 18.4
bar BMEP at a fixed engine speed of 1450 rpm. Two load
points (4.6 bar BMEP and 9.2 bar BMEP) were studied
in detail. Different diesel injection timings, diesel ratios,
and EGR rates were investigated, and comparisons were
drawn to pure diesel operation of the same engine. At
medium load (9.2 bar BMEP), it was possible to obtain
a stable HCCI-like combustion with low NOx emissions
(0.1 g/kWh), reasonably high brake efficiency (37 %), and
low pressure derivatives (5 bar/CAD). High load operation
(18.4 bar BMEP) resulted in low pressure derivatives (5.5
bar/CAD), acceptable brake efficency (36 %), and relatively
low NOx emissions (0.34 g/kWh).

Disputation

Nyckelord

  • Technology and Engineering
  • HCCI
  • Combustion control
  • Fumigation

Övrigt

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