Comparison of Primary and Secondary Emissions from an Internal Combustion Engine - Novel Combustion Concepts for Sustainable Energy Development - page 413

fluorinated ethylene propylene (FEP)
membrane to avoid contamination and minimize wall losses. The chamber walls
were completely transparent to the UV spectrum. A 40

The chamber walls were constructed with fl

µ m thick sheet of cellulose

acetate was used to filter out UV light with wavelengths below 300 nm (UV-C

spectrum). It was kept in between the UV lamp banks and the photochemical
chamber. It was designed to keep the arti cial light spectrum as close as possible to

the sunlight spectrum. A humidity measurement sensor (Testo; 605H1) was kept at
the outlet of the photochemical chamber to monitor temperature and humidity of the
chamber. Chamber leak tests were performed to avoid any interference from the
ambient aerosol. FEP membrane was cleaned with ethanol and demineralized water.
Zero air supply was used to flush the photochemical chamber before starting an

experiment. Zero air supply setup comprised of an external compressor, pressure
regulators, chemical scrubbers and a temperature controller, all contained in one
enclosed unit. Air supply was used to

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flush the photochemical chamber to remove
trace pollutants remaining from the previous experiment. Experimental setup was
equipped with EC/ OC analyzer (Sunset Laboratory; Semi-continuous

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field v.4)
(Gupta et al. 2011 ); online PAHs analyzer (EcoChem Labs; PAS 2000) (Bae et al.
2004 ; Ott and Siegmann 2006 ) to measure total particle bound PAHs; engine
exhaust particle sizer spectrometer (TSI; 3090) to measure the number-size distri-
bution of nanoparticles (5.6

560 nm electrical mobility diameters). In order to
ensure complete particle formation mimicking atmospheric conditions, a partial
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-

flow dilution tunnel was employed to dilute the engine exhaust (Dwivedi et al.
2006 ). Approximately 36 % wall losses were measured using the penetration of EC
through the photochemical chamber in the absence of UV light. All measurements
reported here for EC, OC and total particle bound PAHs in the secondary emissions
were carefully corrected for chamber wall losses.

6 Results and Discussion

6.1 Physical Characterization of Particulates

Particle physical characterization was carried out via measurement of number, mass
and surface concentration distributions for primary as well as secondary particles at
various engine loads at a constant rated engine speed of 1,800 rpm. For primary
diesel particles, number concentration went up abruptly for 100 % rated engine load
for the tiny nucleation mode. However, there was signi

cant number of less than
10 nm particles seen in the primary exhaust from B20. Moreover, the number-size
distribution was much flatter as compared to that from mineral diesel. Nearly two

orders of magnitude reduction in particulate number-size distribution was achieved
with just 20 % biodiesel blend. Majority of this difference was explained by the
nucleation mode particles, which comprises of benzene soluble organic fraction
(BSOF), EC and sulfates (Abdul-Khalek and Kittelson 1995 ). At higher engine

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