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Combustion products, exhaust emissions and engine exhaust deposits formed on thermocouples, positioned after the heat exchanger of an engine power plant, were analyzed chemically. The engine was a lean burn 18W28SG 50 Hz (Wärtsilä NSD, Trollhättan Sweden) fuelled with natural gas equipped with a catalyst (Süd-Chemie NMHC catalyst). The exhaust emissions were sampled using the off-line bottle-in-bag (BiB) method and were analyzed by gas chromatography/flame ionization (GC/FID). Heavier organic compounds and aldehydes were separately collected using adsorption cartridges. The combustion products measured in the emissions were mainly ethene, propene and formaldehyde indicating normal combustion of the fuel in the engine. Organics contained in the engine exhaust deposits were extracted using three different extraction methods: thermal desorption (TD), liquid extraction (LE) and super critical fluid extraction (SFE). The extracts were analyzed by GC/MS.

Combustion chamber deposits from a gasoline direct injection stratified charge SI engine were analyzed using solid-state 1H inverse recovery NMR spectroscopy, before and after thermal desorption (TD). The engine was run with a typical European base fuel, containing 9.8% MTBE. Before TD, solid-state 1H NMR showed two broad peaks representing aliphatics and aromatics. The results showed that T1 (the relaxation time) of the aliphatics was significantly longer than T1 of the aromatics in the deposits. Deposits taken from the piston bowl, with the lowest volatility content, showed the shortest T1. In comparison, piston squish and piston bowl deposits, with higher volatility content showed a longer T1. After TD, T1 of the aliphatics was shorter than the corresponding T1 of the aromatics. A decreasing T1 of aliphatics may be used for following a transition from a liquid (engine oil), via a semi-solid deposit to a solid carbon backbone.

The exhaust emissions from a gasoline direct injection (GDI) engine were sampled using the bottle in bag method and analysed using gas chromatography/mass spectrometry (GC/MS). The GDI engine was run two times using two specially mixed fuels: a typical European base fuel containing additive and a fuel representing worst-case of European gasolines, which is a standardized European fuel, CEC RF 86-A-96, prone to form deposits. The engine was run 60 h for each fuel simulating city driving. Emissions were taken at times 0 h (at the start of the engine), 30 h and 60 h. As a complement, particulate emissions derived from the additized base fuel were sampled on a glass filter during the first 30 h engine run. The extractable organics contained in the filter were analysed using GC/MS analysis. Generally, the emissions were dominated by gasoline components with similar relations as in the gasoline.

Combustion chamber deposits (CCDs) from a gasoline direct injection stratified charge SI engine were analysed. The engine was run with two fuels: a typical European base fuel, containing 9.8% MTBE, and a low volatility worst case fuel. The worst case fuel is a standardized European fuel, CEC RF 86-A-96, prone to form deposits. It contains high amounts of aromatics and olefins but no MTBE. The deposits were analyzed in several ways; thermal desorption followed by gravimetric analysis, fast neutron activation analysis and solid-state 13C nuclear magnetic resonance spectroscopy. Up to 50% of the deposits, formed inside the GDI engine, consist of volatiles. The composition of the deposits is strongly related to the composition of the engine oil. The fraction of volatiles in the deposits decreased in the order: cylinder head, piston squish surface and piston bowl. The deposits from the piston squish surface contained the highest fraction of oxygen, about 30 %.

This work investigates the influence of fuel parameters on deposit formation and emissions in a four-cylinder direct injection stratified charge (DISC) SI engine. The engine tested is a commercial DISC engine with a wall-guided combustion system. The combustion chamber deposits (CCDs) were analyzed with gas chromatography / mass spectrometry as well as thickness and mass measurements. Intake valve deposits (IVDs) were analyzed for mass, while internal injector deposits were evaluated using spray photography. The CCD build-up was obtained with the CEC1 F-020-A-98 performance test for evaluation of the influence of fuels and additives on IVDs and CCDs in port fuel injected SI engines. The 60 h test is designed to simulate city driving. Four fuels were compared in the study: a base gasoline, with and without a fuel additive, a specially blended high volatility gasoline, and a fuel representing the worst case of European gasolines; neither of the latter two had additives.

The purpose of this work was to investigate the influence of fuel parameters on emissions, combustion and cycle to cycle IMEP variations in a single cylinder version of a commercial direct injection stratified charge (DISC) spark ignition engine. The emission measurements employed both conventional emission measurement equipment as well as on-line gas chromatography/mass spectrometry (GC/MS). Four different fuels were compared in the study. The fuel parameters that were studied were distillation range and MTBE (Methyl Tert Buthyl Ether) content. A European certification gasoline fuel was used as a reference. The three other fuels contained 10% MTBE. The measurements were performed at a low engine speed and at a low, constant load. The engine was operated in stratified mode. The start of injection was altered 15 crankangle degrees before and after series calibration with fixed ignition timing in order to vary mixture preparation time.