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Pure sunflower oil was used in a Perkins 4-236 DI diesel engine at 2200 rpm and maximum power, particulate samples at 50°C were obtained from the exhaust 7m from the exhaust port in an air cooled exhaust pipe. The engine lubricating oil was fresh and contained no fuel contamination. The sunflower oil had higher particulate, UHC, CO and NOx emissions than for diesel. This was attributed to the shorter ignition delay and higher diffusive burning. The higher UHC emissions also resulted in a higher particulate SOF. Sunflower oil contained no fuel PAH above 1 ppm and there was no source of PAH from the lubricating oil. However, significant PAH emissions were found in the particulate SOF, but at a level well below that for diesel. It was shown that the bulk of this PAH could be attributed to the thermal desorption of PAH from the exhaust pipe walls. Hence, there was little PAH generated by pyrosynthesis as part of the combustion process.

Diesel engine exhaust pipe and incylinder deposits were analysed for the global fuel, lube oil, carbon and ash fractions for a range of diesel engines. A large SOF fraction, typically 30%, was found and this was dominated by lubricating oil. These deposits are shown to contain significant levels of PAH and hence provide a source of diesel PAH emissions and possible sites for incylinder pyrosynthesis of high molecular weight PAH. A Perkins 4-236 NA DI was used to investigate the role of exhaust pipe deposits on PAH emissions. It was shown that PAH compounds could be volatilised from the exhaust pipe. The difference in the exhaust inlet and outlet particulate composition for diesel and kerosene fuels was used to quantify the n-alkane and PAH emissions originating from the exhaust pipe deposits. Comparison with pure PAH free fuels showed that the exhaust outlet PAH composition was similar to that expected from the exhaust pipe deposits.

Exhaust particulate and gas composition samples were obtained at various distances along an externally air cooled exhaust from a Perkins 4-236 single cylinder engine. The change in the particulate composition was determined as a function of the exhaust distance and local temperature. Exhaust temperatures were in the range 200 - 260C at entry to the tunnel at all engine conditions. A constant filter paper and sample temperature of 50C was used for both exhaust and dilution tunnel samples and the filter paper was mounted in an oven for this purpose and the particulate sample was tranported through heated lines to this oven. Associated with these particulate measurements were gas analysis measurements. UHC were measured at 180, 50 and 2C in the exhaust and the differences were taken as an indication of the condensable hydrocarbons over that temperature difference.

The objective was to investigate PAH emissions in diesel particulates using a kerosene fuel that had a PAH content that was predominantly two ring. Higher PAH were two orders of magnitude lower in concentration in the fuel than for diesel, but the two ring PAH were a higher proportion of the fuel than for diesel. Pyrosynthesis of higher PAH in the particulate from the two ring PAH would thus be easier to detect for kerosene. Fresh PAH free lubricating oil was used throughout in an attempt to eliminate additional sources of PAH. The kerosene results showed that emissions of higher PAH were an order of magnitude lower than with diesel. However, these PAH emissions were compatible with an unburnt fuel source, as the n-alkane results showed that the higher MW fuel components had a much greater survivablity than for diesel. A contribution to PAH and n-alkane emissions from the exhaust pipe deposits was also identified.