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A base diesel fuel with 37% 1-3 ring aromatics and 12.9% PAH was passed through a dearomatising process that removed the two and three ring aromatics and reduced the single ring aromatics to 14%. These two fuels plus a combination of 60% of the original fuel with 40% of the low aromatic fuel were tested on a Perkins Phaser TCIC diesel engine of US 1991 emissions standards over the EC 13 mode cycle. The fuels and particulate SOF were analysed for all the n-alkanes and all of the PAH of significant concentration. The high speed maximum power particulate SOF were analysed in detail for all three fuels and mass emissions of 15 n-alkanes and 15 PAH determined and 15 other non-fuel PAH searched for. Most of the results showed that the composition of the SOF in terms of n-alkane and PAH was predominantly unburnt fuel compounds, the fuel with negligible PAH had very low PAH emissions compared with the parent fuel with a high PAH content.

The relationship between a diesel engine lubricating oil consumption and the particulate volatile unburnt lube oil emissions depends on the combustion efficiency of the lube oil in the engine. Very little data exists on this topic and this is reviewed. An experimental procedure for the determination of lubricating oil consumption from a calcium mass balance between the lubricating oil and particulate was used combined with a thermogravimetric analysis of the particulate to obtain the unburnt lube oil emissions, together these techniques enabled the lube oil combustion efficiency to be determined This technique only requires the particulate filter paper as an experimental measurement in the engine test. Initial results for a Perkins 4-236 NA DI diesel engine are presented for a range of loads and speeds.

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.

The ELPI particle size instrument measures the number of particles in 12 size ranges using a series of impaction stages. To convert the measurement of number to mass, the instrument assumes that all the particles are spheres and are of a constant density, defined by the user, but normally around 1000kg/m3. Both of these assumptions are incorrect for all size ranges and the resultant mass emissions for PM10 usually do not agree with standard filter paper measurements. This paper presents a review of the current situation of the knowledge on converting particle number into mass, using the ELPI or other particle size instruments. Andersen Impactors were used for gravimetric determinations of the mass in the sizes above 400nm, in order to compare their resullts with ELPI number measurements. Gravimetric determination of mass using the ELPI was also attempted. The sampling time with both instruments was two hours to collect enough mass to weigh in each size range.

This work is part of a larger programme to investigate the storage at low power conditions and release at high power conditions in real diesel engine exhaust systems. The initial particle storage in the oxidation catalyst, followed by a release of particles a few minutes later, is explored, and the associated particle size distribution changes determined. A Ford 1.8L IDI Diesel Engine, Turbocharged and Intercooled (TCIC), and equipped with Exhaust Gas Recirculation (EGR), was used under high speed and high power conditions, both during cold start. The commercial close-coupled diesel oxidation catalyst had an associated hydrocarbon adsorber for cold start hydrocarbon control. The tests were carried out using a step cold start to a fixed low power output, typical of city driving. The ELPI particle size analyser was used together with constant temperature gravimetric filter based mass samples upstream and downstream of the catalyst.

An oxidation catalyst was fitted on a DI diesel engine for an experimental study involving an oxidation catalyst and the use of superheated steam for fumigating the intake air. Results are compared with that of the influence of low level of fumigation of the intake air with superheated diesel fuel. Exhaust emissions of NOx, CO, UHC, TPM, SOF and Carbon were measured and quantified on upstream and downstream of a low light off temperature (250 °C) oxidation catalyst. The technique used an electric vaporizer for producing superheated steam and prevaporised superheated diesel fumes at 350 °C, respectively. A low emissions version of Perkins 4-236 engine with squish lip piston was run both with and without fumigation at two speeds 1200 rpm and 2200 rpm. Roughly covering both city and highway running conditions.

Results showed the influence of the oxidation catalyst on exhaust emissions from a DI diesel engine due to the partial premixing, fumigation of the intake air with diesel fuel. Exhaust emissions of NOx, CO, UHC, TPM, SOF and Carbon were measured and quantified on upstream and downstream of a low light off temperature (250 °C) oxidation catalyst. Two methods of diesel fumigation of the intake air with fuel were used. The difference between these two methods was the degree of premixing of diesel fuel with the intake air. The first technique used a high-pressure fine diesel spray onto a glow plug and the second technique used an electric vaporizer for prevaporised superheated diesel fumes at 350 °C. A low emissions version of Perkins 4-236 engine with squish lip piston was run both with and without fumigation at two speeds 1200 rpm and 2200 rpm. Roughly covering both city and highway running conditions.

Results of an experimental study of a DI Diesel engine are presented, which show the influence of partial premixing fumigation of the intake air with diesel fuel on the exhaust emissions and the engine performance parameters. Exhaust emissions of NOx, CO, UHC, TPM, SOF and Carbon were measured and quantified. Engine performance parameters include the event of the start of combustion and fuel consumption besides other parameters, which were published elsewhere. The study also showed that during a “normal operation” of a DI diesel engine, no emissions trade-off exists between NOx and TPM. Rather these emissions need separate technological measures for their specific control. Two methods of diesel fumigation were used. The difference between these two methods was the degree of premixing of diesel fuel with the intake air.

Reduction of NOx was achieved in an experimental study in a DI Diesel engine. Results are presented, which show the comparison of the influence of partial fumigation of the intake air with superheated diesel fuel vapour and that of steam on the exhaust emissions and the engine performance parameters. Exhaust emissions of NOx, CO, UHC, TPM, SOF and Carbon were measured and quantified. The technique used for fumigating the intake air with fuel and steam consisted of an electric vaporizer for producing perfectly prevaporised superheated diesel fumes and steam at 350°C. A low emissions version of Perkins 4-236 engine with squish lip piston was run with the fumigation of the intake air with superheated fuel vapour and that of steam at two speeds 1200 rpm and 2200 rpm, roughly covering both city and highway running conditions.

A naturally aspirated Perkins 4-236 engine was compared with a similar turbocharged Perkins engine. The higher pressures and temperature of a turbocharged engine should make the pyrosynthesis of PAH more likely than for a NA engine and this was investigated using the fuel n-alkanes as tracers for the unburnt fuel of the same fuel distillation fraction as the PAH. The results showed that the below C20 the NA and TC survivabilities of fuel n-alkanes onto the particulates were similar at below 0.02%. For higher n-alkanes the turbocharger was much more efficient at burning the fuel, with survivabilities of C24 a factor of 10 below the NA results. The higher operating temperatures of the TC engine reduced the UHC emissions and this reduced the higher boiling fraction unburned fuel. In contrast to these results the fuel PAH apparent survivability's were higher, by approximately a factor of 10, for the turbocharged engine for equivalent boiling point compounds in the range C18-C22.

Diesel fuel was injected into the inlet air port of a Perkins 4-236 NADI diesel engine using a Stanadyne 5 micron fuel injector directed onto the back of the inlet valve so as to give the best port fuel injection vaporisation. The fuel was timed to be injected when the inlet valve was open and the exhaust valve closed. Up to 20% of the maximum power fuel flow was injected into the inlet port and the effect is to reduce the diffusion burning phase of diesel combustion at maximum power and hence to reduce soot emissions. The results show that an older relatively high emitting diesel engine can be retrofitted with this technology to produce large soot emission reductions with soot reduced to the level of modern low emission engines. Fumigation also decreases the ignition delay, which at constant fuel injection timing reduces the NOx emissions.

A 1117cc Ford Valencia SI engine was used to investigate the influence on emissions of relatively large (10-30%) additions of ethanol to gasoline. The ethanol was shown to extend the lean burn range and improve the specific energy consumption in the lean burn region. Addition of ethanol significantly reduced NOx and CO by over 50% and increased slightly HC and condensible hydrocarbons, but had little effect on NMHC.

A small 0.220 litre Petter IDI single cylinder engine was investigated over a 120 hour test period, consisting of 40 three hour test runs, with emission measurements and lubricating oil analysis every 20 hours for the same batch of fuel and lubrication oil. The particulates were analysed for the SOF and for the fuel/lubricant proportion using TGA. Fuel dilution of the lubricating oil was shown to increase uniformly with time and reached 10% after 120 hours, there was an associated decrease in the viscosity and increase in the lube oil fraction in the particulate SOF. Carbon contamination of the lubricating oil increased to 1.6% by mass over the 120 hour test period. The particulate emissions decreased initially and then increased after 50 hours, but the effect was no more than a 30% variation, mainly caused by variations in the carbon emissions. The motoring particulates were found to be low and dominated by vaporised lubricating oil.

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.

The influence of nozzle sac volume on the composition of the fuel derived solvent organic fraction of diesel particulate from a naturally aspirated 1 litre per cylinder diesel engine was studied. Significant differences in the quantities of the polycyclic aromatic compounds for different sac volumes were found. The emission differences were due to the reduction of unburnt fuel contributions to particulate SOF as the sac volume was reduced.

An old single cylinder Petter AA1 and a new four cylinder Ford 1.61 engines were operated over a wide range of steady state conditions using kerosene and diesel fuels. The two engines exhibited different trends in forming the particulate emissions. For both fuels the particulate emissions were dominated by the carbon for the old engine, and by the SOF for the new engine where the latter was characterized by its low level of emissions. The engine operating conditions also influenced the emissions of the different particulate fractions. Generally, the old engine had higher unburnt lube oil emissions as well as high survival of diesel n-alkanes and PAH in the emissions. However, in the case of kerosene and the new engine when operated both with kerosene and diesel fuel, the pyrosynthesis of these compounds was evident. Sulphates in the particulates, which originated mainly in the fuel, were shown to incorporate low levels of background from the engine deposits and the lubricating oil.

A Ford Valencia engine was tested with a sudden start-up to a fixed speed and load and the coolant, lubricating oil and exhaust emissions were monitored as a function of time. Steady state tests were carried out with and without air preheat and with synthetic lubricating oil. These showed that the air preheat had a major impact on the hydrocarbon emissions and this had to be eliminated if the influence of the lubricating oil and water warm-up alone was to be investigated. The synthetic lubricating oil tests showed the importance of the lubricating oil in the hydrocarbon emissions as well as the reduced sfc. Tests with water and lubricating oil initially at ambient temperatures were compared with tests with the water externally heated and the lubricating oil cold, and with cold water and hot lubricating oil.

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.

The reduction of Diesel particulate SOF, including the PAH was investigated using a conventional one pass Englehard PTX exhaust catalyst, which formed part of an underground mine Diesel exhaust clean up system. The reduction in total particulate mass and the SOF mass was approximately 70% for exhaust temperatures above 250 C, which was better than for the low MW gas phase UHC. For the PAH and other high MW compounds in the SOF a 70% reduction in the mass emissions was achieved for temperatures above 170 C. This greater catalytic efficiency at lower temperatures for high molecular weight compounds was attributed to these compounds, at the catalyst temperature, being in the liquid phase absorbed into the particulate and in direct, locally concentrated, large surface area contact with the catalyst surface. The low MW compounds of the SOF would be in the gas phase at the catalyst temperature.