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Previous work on the transient storage of particulate in diesel exhaust systems (SAE 2000-01-0508) was carried out mainly at conditions where storage in the exhaust would dominate the process. The test involved a preconditioning of the engine the previous day with about 4 hours of engine idling. This ensured that the exhaust had a significant level of deposits. The following day low power cold starts were investigated and the movement of particulate between the two silencer boxes was determined as well as the net blow out of deposited particulate. Continuing deposition if particulate was also shown even in the presence of net blow out. The present work extends this previous work to higher power blow out conditions. Also investigated was the preconditioning of the engine at high power the previous day so that the exhaust was in a much cleaner condition. The previous tests were then repeated.

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 non-metallic organic diesel fuel additive was investigated, Energy Plus D 2000, which is marketed as a fuel economy additive, where typical fuel economy benefits are 10%. The influence of this additive on diesel engine pollution was investigated using a Perkins 4-236 NA DI diesel engine. The additive was found to markedly reduce the particulate emissions by up to 75%. The volatile fraction was reduced slightly more than the carbon and the additive had a strong direct effect on carbon emissions. The optimum level of additive was 0.2%. Higher dosages continued to produce a decreasing level of particulate emissions, but the rate of reduction in the particulates with increase in additive was much lower after 0.2%. However, the active ingredients of the additive are dissolved in kerosene and hence the active component dosage was much less than the nominal dosage. This type of additive warrants further investigation as a means of diesel particulate control.

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 test procedures used to investigate the transient warm-up of two Ford 40 kW SI engines are described. Water, engine casing and lubricating oil temperatures were monitored and the rates of temperature rise determined as a function of engine speed and power. The temperature results showed that for both engines the lubricating oil was the slowest component in the warm-up and may be the limiting factor in engine warm-up. A particular emphasis has been placed on monitoring the gas composition during the warm-up. A special feature of this system is the use of two UHC FID analysers operating at 180°C and 2°C. The difference in the two UHC readings is a measure of the high molecular weight condensible UHC or unburnt liquid fuel that is emitted. It is shown that this is quite significant during the initial period of warm-up.

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.

Although water injection or water/fuel emulsions are a well known method of reducing NOx in stationary Diesel engines, their influence on Diesel particulates and particulate SOF has recieved little study. A single cylinder DI Petter engine was used to investigate the influence of Diesel/water emulsions on particulate emissions and associated gaseous emissions. Water/fuel ratios of up to 20% were used and a strong influence on emissions was found. Both NOx and particulate emissions were decreased with increased water content. However, there was a major increase in the unburnt hydrocarbons. Associated with this was a similar increase in the particulate solvent organic fraction and of the PAH fraction of this. These effects on UHC and PAH emissions make Diesel/fuel emulsions an unattractive solution to the Diesel NOx and particulate emissions problems.