Using Petroleum and Biomass-Derived Fuels in Duel-fuel Diesel Engines - Novel Combustion Concepts for Sustainable Energy Development - page 252

Table 2 Engine parameters
and other properties for the
reference case

Engine speed, rpm 1,500

Engine bore diameter, mm 82

Engine stroke length, mm 90.4

Squish height, mm 0.6

Connecting rod length 145.4

IVC (intake valve closing), CAD − 132 ATDC

Gas temperature at IVC, K 350

Gas pressure at IVC, bar 1.23

EVO (exhaust valve opening), CAD 116 ATDC

SOI (start of injection), CAD − 8 ATDC

Fuel injection temperature, K 298

Nozzle diameter, mm 0.141

Injection duration, CAD 8.5

Fuel intake temperature, K 298

Cylinder head temperature, K 500

Cylinder wall temperature, K 450

Piston wall temperature, K 550

each cylinder. Simulations were performed for a 1/7 (51.43 ) sector of the cylinder.

Table 2 provides the engine parameters and other properties for the reference case.
N-heptane is used as the surrogate for diesel fuel, while methane is used to represent
biogas. For dual-fuel cases, methane or syngas premixed with air is introduced
through the intake manifold. Simulations are started at the intake valve closing. The
fuel oxidation chemistry is modeled using the Chalmers mechanism (Golovichev n.
d.; Tao et al. 2007 ), which contains 42 species and 168 reactions. The software also
contains models for soot and NO x formation, which are described by Senecal et al.
( 2007 ) and Patterson and Reitz ( 1998 ).
While the reaction mechanism has been extensively validated in previous
studies, additional validation is provided in Fig. 9 , which presents the predicted and
measured ignition delays for n-heptane/air, methane/air, and syngas/air mixtures at
engine relevant conditions and

°

= 1. The constant pressure homogeneous reactor
simulations were performed using the CHEMKIN software along with the Chal-
mers and CRECK (Ranzi 2012 ) mechanisms. The CRECK mechanism is a com-
prehensive mechanism with 466 species 14,631 reactions and has previously been
validated against various targets,

ϕ

including ignition delays, fl ame speeds, and

species measurements. In the figure, the predicted ignition delays are compared

against the measurements for n-heptane/air (Gauthier et al. 2004 ), methane/air
(Huang et al. 2006 ), and syngas/air mixtures (Mittal et al. 2006 ). Overall, there is
good agreement between the measurements and predictions of the two mechanisms.
The Chalmers mechanism somewhat overpredicts ignition delays for n-heptane and
underpredicts for methane at high temperatures. For syngas, both the mechanisms
signi cantly underpredict the ignition delay at temperatures below 1,000 K. These

differences have been attributed to mixture non-homogeneities present in