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A study was conducted to investigate the relative influence of charge cooling and autoignition chemistry on the greater knock resistance seen by alcohol fuels compared to petrols when operating under “Beyond RON” conditions in a Port Fuel Injection (PFI) engine. The methodology employed was that of a modelling study calibrated and validated using experimental data, with ethanol and iso-octane used as representatives of the alcohol fuels and petrols respectively. A two zone combustion model combined with an empirical knock model formed the centre of the modelling work, with the experimental investigation conducted on a boosted PFI engine. The comparison of knock resistance between ethanol and iso-octane showed that autoignition chemistry plays the largest role in the knock resistance advantage of ethanol. This dominance by autoignition chemistry is partly aided by PFI's poor use of the charge cooling capacity of ethanol.

Iso-stoichiometric ternary blends - in which three-component blends of gasoline, ethanol and methanol are configured to the same stoichiometric air-fuel ratio as an equivalent binary ethanol-gasoline blend - can function as invisible "drop-in" fuels suitable for the existing E85/gasoline flex-fuel vehicle fleet. This has been demonstrated for the two principal means of detecting alcohol content in such vehicles, which are considered to be a virtual, or software-based, sensor, and a physical sensor in the fuel line. Furthermore when using such fuels the tailpipe CO₂ emissions are essentially identical to those found when the vehicle is operated on E85. Because of the fact that methanol can be made from a wider range of feed stocks than ethanol and at a cheaper price, these blends then provide opportunities to improve energy security, to reduce greenhouse gas emissions and to produce a fuel blend which could potentially be cheaper on a cost-per-unit-energy basis than gasoline or diesel.

The world's first large scale commercial Gas-to-Liquids (GTL) fuel production plant using low temperature Fischer-Tropsch (LTFT) technology, Oryx GTL, has been in operation in Qatar since 2007. The first on-specification diesel fuel produced by this plant was subjected to a comprehensive fit-for-purpose validation program, part of which comprised exhaust emission tests which were conducted with two different passenger cars and two different heavy-duty engines. Three neat GTL diesel fuels were included in the study: commercial GTL diesel fuel, an equivalent full boiling range GTL diesel fuel produced in a pilot plant, and a GTL diesel fuel with a narrower distillation range. Commercial sulfur-free (≺10 mg/kg) European EN590 diesel fuel was used as the reference fuel. In addition, tests were performed with two different blending ratios (20% and 50%) of GTL diesel in the EN590 diesel.

This paper reports on the comprehensive applications testing of the first commercial volumes of Gas-to-Liquids (GTL) diesel produced via the Sasol Slurry Phase Distillate™ (Sasol SPD™) process, a Low Temperature Fischer-Tropsch (LTFT) process, at the Oryx GTL plant in Qatar. The technical literature is well populated with results of emissions and applications studies of GTL diesel; however, these results have been limited to product produced at pilot plant and relatively small commercial scale. To ensure that diesel produced commercially not only matches the performance of material previously produced at pilot plant scale using the same technology, but is also fit-for-purpose in the broader sense, a series of chemical assessments and applications testing was performed using both neat and blended diesel fuels. These included emissions tests in passenger cars and heavy-duty applications, engine durability, injector fouling performance and a passenger car fleet trial.

It has been shown that modern spark-ignition engines exhibit greater resistance to auto-ignition for fuels with increased octane sensitivity (RON − MON). This is often presented in terms of the Octane Index, OI = RON − K(RON − MON) with modern engines generally correlating with negative K values. Most of the studies have either presented detailed research type engine tests which show directly the impact on knock limited spark advance (KLSA), or have shown overall vehicle performance benefits and thus have inferred the KLSA response to OI. The aim of this research was to directly measure and compare the actual responses of various engine control parameters of modern production vehicles having different technology levels, to fuels with different OI values derived through different sensitivities. Comprehensive testing was performed at an altitude of over 1500 metres and confirmatory testing performed near sea level.

An EU4 compliant vehicle was tested according to the ECE R83.05 procedure, with dilute and speciated modal analysis, on a European EN228:2004 gasoline and 3 South African gasolines, one of which is a synthetic gasoline made from coal using the Fischer-Tropsch process. The synthetic fuel had broadly similar regulated emissions to the EN228 fuel while the two South African crude derived fuels had significantly higher HC and NOx emissions. The synthetic fuel's exhaust olefins were similar to the EN228 fuel and aromatics were significantly lower than all the other fuels. The photochemical reactivity of the synthetic fuel was seen to be similar to the EN228 while the South African crude derived fuels were significantly higher.