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The use of two or three FID hydrocarbon analysers for the determination of condensable or liquid unburned fuel is described. Each FID has upstream pumps and filters in separate sample conditioning systems operating at three different temperatures of 180C, 50C and 2C. The 50C system could operate at any temperature up to 100C, the use of 50C was because this was the temperature used for sampling diesel particulates. The difference in the three hydrocarbon readings was used to determined on a mass basis the condensable UHC over the sample temperature difference of either 180C to 2C or 180C to 50C. The latter hydrocarbon difference was shown to be close to the particulate fuel fraction of the SOF. A range of applications of this technique to both diesel and spark ignition engines are described, including the warm-up of a Ford CVH SI engine and the influence of nozzle sac volume on condensable hydrocarbon emissions in a Perkins 4-236 diesel.

A mass balance has been carried our between fuel and particulate SOF n-alkanes and the survivability of a range of fuel n-alkanes was determined, Similarly the survivability of fuel PAH was determined and compared with the equivalent boiling point n-alkanes. A Petter AA1 single cylinder IDI engine was used with direct particulate sampling at 50C from the exhaust. The PAH and n-alkane fuel component survivabilities were mainly below 0.1%, indicating that unburnt fuel was the dominant source of particulate PAH. However, at maximum power there was an order of magnitude difference in the survivabilities of some PAH and n-alkanes. This indicated a possible pyrosynthesis source of PAH or a role of the engine and exhaust deposits in releasing PAH. The results confirm previous conclusions from test on a DI engine.

The objective was to investigate combustion generated PAH in Diesel engine particulate emissions using a pure single component fuel, hexadecane, in a Perkins 4-236 engine in a single cylinder format. The results were compared with those using a conventional Diesel fuel and with the particulates collected by motoring the engine. To minimise any influence of contamination from the PAH in used lubricating oil, all the tests were carried out with fresh PAH free lubricating oil. The hexadecane particulates were found to contain 6-25% of the PAH and 5-9% of the n-alkanes for Diesel and the motoring tests were found to give 10% of the PAH and 50-200% of the n-alkane for hexadecane. It was concluded that there was an internal source of n-alkane and PAH in the engine and exhaust system, probably absorbed in engine deposits. It was therefore not possible to conclude that the PAH with hexadecane was pyrosynthesised.