28-03-2014, 02:00 PM
Engine Performance and Emission Characteristics of CRDI Diesel Engine Equipped with WCC and DOC using Ethanol Blended Diesel Fuel
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Abstract
Emission characteristics of CRDI diesel engine equipped with a warm-up catalyst (WCC) and a diesel oxidation
catalyst (DOC) were investigated. The experimental investigation was conducted a neat diesel fuel, a blend of diesel
fuel with 15% ethanol, a blend of diesel fuel with 15% ethanol and cetane improver EHN (2-ethylhexyl nitrate) of
7500ppm. The experiments measured the emission and engine performance according to ECE 13 mode cycles. The
maximum torque provided by the ethanol-diesel-EHN blended fuel was higher than that by the neat diesel fuel at high-
load conditions. The specific fuel consumption in g/kWh slightly increased with the 15 % ethanol blended diesel fuel in
the low load. Smoke was decreased by more than 28-58% in the entire ECE 13 mode cycles. HC and CO emissions of
the ethanol blended fuel were slightly increased; however, the mean conversion efficiencies of HC and CO on the
catalysts appeared about 60-80% in the ECE 13 mode cycles. Based on measurement by the Scanning Mobility Particle
Sizer(SMPS), the particulate matter(PM) nano-particle number and mass of the diesel fuel with 15% ethanol and EHN
decreased by 30-40 % compared with neat diesel PM emission. The results showed that the CRDI diesel system with the
diesel fuel with 15% ethanol and EHN with WCC and DOC can meet emission regulations before enforcement of a
strengthened regulation such as EURO V.
INTRODUCTION
Diesel engine has a high thermal efficiency and gives
low greenhouse effect due to its low rate of fuel
consumption and low amount of CO2 emission compared
to the gasoline engine. However, diesel engine has the
problem of generating large amount of smoke because its
diffusion combustion characteristics causes air to be used
at a low rate, and its localized high temperature generates
NOx which is a source of air pollution in the city. To
solve these problems, electric control high pressure fuel
injection system1) has been adopted recently in diesel
engine. This system can atomize the spray droplet for the
fuel so that the high rate of air utilization can reduce the
amount of smoke. However, it is difficult to reduce
emission of NOx and PM at the same time because of the
properties of diffusion combustion. Ethanol blended
diesel fuel has been recently studied2-7) as a possible
alternative fuel for the petroleum4-7)
TEST PROCEDURE
The engine performance and the emission
characteristic of the exhaust gas from a WCC and DOC
equipped CRDI diesel engine, which used 3 kinds of
fuels, the neat diesel fuel (D100), a blend of diesel fuel
with 15% ethanol (E15+D), and a blend of diesel fuel
with 15% ethanol and cetane improver (E15-D-CI). In
blended fuel, 1% of co-solvent (tetrahydrofuran,
C4H8O)9) was added into the ethanol blended fuel to
improve the solubility of ethanol, and EHN 7500 ppm10)
was used as the cetane number improver. Li11) indicated
that 15% content of ethanol in diesel fuel was the
optimum content for optimum smoke emission and
engine performance of the direct injection diesel engine.
The steady-state of ECE (economic commission for
europe) 13 mode was used in the experiment8). The
concentration of THC, CO, CO2, O2, NOx and smoke
were continuously measured at the front and rear of
catalysts in each mode. The conversion efficiency is
calculated as ((1- A out )/A in) x 100 (%).
CONCLUSIONS
The engine performance and emission characteristics
of the CRDI diesel engine equipped with WCC and DOC
using diesel-ethanol blended fuel and cetane improver
were investigated under the ECE 13 mode. The results are
summarized as follows:
1. The engine performance from E15-D and E15-D-CI
was similar to that of the base diesel engine with respect
to power output, and E15-D-CI had the highest thermal
efficiency because of the addition of the cetane
improver (EHN).
2. Smoke emission from the use of the ethanol blended
fuel was remarkably reduced; the smoke reduction rates
with E15-D and E15-D-CI were 28% and 58%,
respectively. From this result, for the CRDI diesel
engine, 15% of ethanol with cetane improver is
recommended to reduce PM to less than half.