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Six full range gasolines were tested in two engines (one with a catalyst) operated at 4 steady states. Engine-out regulated emissions responded to equivalence ratio, Φ, in the accepted manner. For both CO and NOx, there was a characteristic, single emissions response to changes in Φ. Changing fuel composition will primarily alter the production of these emissions by modifying the stoichiometric air/fuel ratio, projecting engine operation onto another part of the Φ response curve. These Φ effects, which are independent of engine design, also determine how operating conditions affect engine-out CO and NOx. Speciated hydrocarbon measurements at engine-out and tail-pipe confirm results seen in previous test-cycle based programmes.

Speciated hydrocarbon emissions were measured at steady-state conditions in pre- and post-catalyst exhaust from a modern multi-valve fuel-injected and closed-loop controlled European gasoline engine tested on toluene, isooctane and diisobutylene. Unburned fuel contributed 70-80% of the total engine-out hydrocarbon emissions on toluene, but only 24% and <10% on isooctane and diisobutylene respectively except at idle where values were 71% and 47% respectively. Emissions from both of the aliphatic fuels were dominated by photochemically-reactive olefins such as isobutene and propene, plus ethyne, methane and formaldehyde. With the exception of ethyne, emissions of these compounds were much less from toluene. Even at rich conditions, most hydrocarbons were catalytically controlled to some extent, but the catalyst efficiency was dependant upon hydrocarbon composition.

Seven hydrocarbons were determined continuously in gasoline engine exhaust over the US FTP cycle using Fourier Transform Infra Red Spectroscopy (FTIR). Three of the hydrocarbons were also determined using Chemical Ionisation-Mass Spectrometry (CI-MS). Tests with and without a three way catalyst illustrated the strong dependence of catalyst performance on the composition of the hydrocarbons emitted. For example, the FTIR indicated that over a cold start FTP cycle, the catalyst took 98 seconds to achieve a 50% conversion rate for ethyne, 183 seconds for ethene and 229 seconds for ethane. The work indicates that FTIR in particular is an appropriate technique for the monitoring of exhaust catalyst performance.

To gain a better understanding of the exhaust emissions impact of olefins in a low aromatic, full boiling range gasoline, an evaluation of the before and after catalyst emissions of three highly olefinic refinery streams and three highly paraffinic refinery streams, blended 50/50 in motor alkylate, was conducted using a 3.1 L GM engine. The test fuels were also selected to consider the effects of volatility in addition to olefin concentration. The fuels were evaluated under three steady state engine operating conditions. The results of the tests indicate essentially only small differences in the before and after catalyst total hydrocarbons (THC) between the pairs of highly olefinic streams and the highly paraffinic streams at relatively the same volatility level, for two of the test conditions (2400RPM-light and moderate/heavy loads. The ozone forming potentials (OFP) for these fuels, across all three speed and load conditions, also show relatively small differences.

Twenty-three hydrocarbons were measured in the exhaust gases from a Volvo passenger car fitted with a 2.3 litre gasoline engine. Measurements were made in the absence of a catalyst, and in the presence of a fresh and an aged three-way catalyst, with particular attention being paid to the emission of benzene and other light aromatic compounds. Loss of catalytic activity through ageing led to an increase in hydrocarbons of ∼ 200% from 0.22 to 0.62 g/mile. Loss of activity was most evident for certain compounds notably alkanes (paraffins) although large increases in aromatic emissions were also apparent; catalytic control of ethyne (acetylene) was, however, completely maintained by the aged catalyst. Thus the work reported here demonstrates the selective manner in which a catalyst operates depending upon the chemical structure of hydrocarbons, and how this influences catalyst performance loss via ageing.

Twenty-three hydrocarbon components were analysed in the exhaust emissions from a 2.3 litre gasoline engine. The effect of a three-way catalyst on emission rates was investigated, as was the effect of addition to fuel of specific aromatic and olefinic compounds. The addition of 1-hexene and 1-octene (olefins) caused statistically significant increases in reactive olefins - ethene and propene - in the exhaust. The addition of benzene and toluene led to increases in these compounds in the exhaust, and indicated that whilst fuel-toluene is the main source of toluene emissions, the emission of benzene has sources in addition to fuel-benzene. A three-way catalyst, when operating at > 600°C, eliminated most hydrocarbons except methane and traces of the light aromatics. At idle, however, the catalyst exhibited substantial selectivity towards different hydrocarbons according to their ease-of-oxidation.

Particulate-bound hydrocarbons emitted by diesel engines have been analysed using a rapid new technique. The method involves directly loading filter-borne particulate into a modified injection port of a gas chromatograph. Hydrocarbons are vaporized in this solid sample injection system and subsequently become adsorbed on to a chromatography column. The merits of this procedure are demonstrated by comparing results with those obtained using conventional gas chromatography (with liquid injection) and thermogravimetry. The contribution of unburned engine oil to diesel particulate emissions has been investigated using the new method. For a DI truck diesel engine operated over the U.S. Federal Heavy Duty Transient Cycle it is shown that 40% of the particulate appears to be derived from unburned oil. For a comparable IDI truck diesel engine this value was 28%.

Extracts of particulate emissions from light duty diesel, conventional gasoline and lean-burn gasoline engines have been analysed using a range of short-term bioassays. The intention of the analyses was to identify tests which could be routinely applied to exhaust assessment in order to study the effects of engine operating conditions and design on biological activity. In this respect the most promising assays were the Ames Salmonella typhimurium test for mutagenicity, the detection of chromosome damage in rat liver cells, and the assessment of growth and development defects in the Hydra Regeneration Assay.

A Tapered Element Oscillating Microbalance (TEOM) was used to measure transient diesel particulate emissions. Light duty IDI and DI engined vehicles were tested over the LA4 Drive Cycle. One vehicle, a 1.6 litre IDI diesel engined VW Golf (Rabbit), was also tested over the Japanese 10-mode and European ECE-15 Cycles. Transient particulate emissions were also measured from a heavy duty DI diesel engine tested according to the US Federal Heavy Duty Transient Test Procedure. The TEOM proved to be very flexible, permitting continuous particulate measurements to be made at each of the conditions studied. Particulate mass determined by the TEOM over a complete cycle was generally lower, typically by between 13 and 28%, than that measured using conventional gravimetric filtration procedures. A new calibration technique was devised which improved the correlation between TEOM and gravimetric results.