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A project has been undertaken to optimize the engine control software calibration of a modern heavy-duty diesel engine for operation with gas-to-liquids (GTL) diesel fuel, with the objective of developing an understanding of the scope for optimization with this fuel, which has different physical and combustion properties to that of conventional, crude-derived diesel. A data-driven, model-based calibration technique utilizing artificial neural networks was used to develop optimized transient and steady-state calibrations with both conventional diesel fuel, as well as neat GTL fuel. The engine control parameters that were optimized were injection timing, exhaust gas recirculation rate, rail pressure, and charge mass. The optimization aimed to minimize fuel consumption without deterioration in engine-out nitrogen oxide (NOx) and soot emissions. This paper reports on the calibration optimization methodology employed and the results achieved to date.

A study was performed to quantify the impact of blending Fatty Acid Methyl Ester (FAME) with Gas-to-Liquids (GTL) diesel fuel on engine exhaust emissions. Fuels that were considered in the study included blends of GTL and EN590 diesel containing 0, 7, and 20 volume % of Soy and Rapeseed Methyl Ester (SME and RME). Part of the study focused on European engine technology, and tests were performed on a Euro 3 passenger car engine and a Euro V heavy-duty engine. A limited study was performed using a heavy-duty engine meeting the US 2004 emission standards, in which case comparisons between the GTL diesel and FAME blends were made with US 2D and California Air Resources Board (CARB) reference fuels. The results showed particulate mass (PM) reductions to varying degrees with all of the GTL/FAME blends.

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.

A novel in situ method was performed for measuring emissions and fuel consumption of transport refrigeration units (TRUs). The test matrix included two fuels, two exhaust configurations, and two TRU engine operating speeds. The test fuels were California ultra low sulfur diesel and gas-to-liquid (GTL) diesel. The exhaust configurations were a stock original equipment manufacturer (OEM) muffler and a Thermo King pDPF™ diesel particulate filter. The two TRU engine operating speeds were high and low, as controlled by the TRU user interface. Test results indicate that GTL diesel fuel reduces all regulated emissions at high and low engine operating speeds. Separately, the application of a Thermo King pDPF reduced regulated emissions, in some cases almost entirely. Finally, the application of both GTL diesel and a Thermo King pDPF reduced regulated emissions at high engine operating speed, but with an increase in oxides of nitrogen (NOx) at low engine speed.

World wide, energy policy makers are increasingly keen to move away from petroleum based fuels to more diverse and renewable sources of energy for reasons of environmental protection, energy security and continued economic development. A well-known example is Gas-To-Liquid (GTL) diesel fuel which is derived from natural gas and thus provides a diversification away from crude oil, which is the feedstock for 97% of the world transport fuels. Towards the same goal, Fatty Acid Methyl Esters (FAME), from vegetable oils, recycled oils, or animal fat, are being used with increasing frequency as blends with diesel fuel, even at a concentration of 30% in some captive fleets (B30). In this paper, the impacts on engine pollutant emissions and performance are evaluated.

The results of an optical investigation into the combustion characteristics of GTL (Gas-To-Liquids) diesel fuel are presented. The investigation was carried out using a high pressure, constant volume combustion chamber with optical access, fitted with a modern diesel injection system. Combustion images were captured under conditions which simulate those present in a diesel engine. A low sulphur diesel fuel meeting the European EN590 specification was used as a reference. Image capture and subsequent analysis was performed by means of an AVL Visioscope system which used the two-colour method to yield quantitative information regarding flame temperature and soot concentration. Conditions in the combustion chamber are preset by combusting a pre-charge to generate the necessary pressure, temperature, and residual gas fraction. This allowed the effect of varying oxygen concentration at the start of diesel combustion to be investigated.

A Mercedes E320 CDI vehicle has been modified for more optimal operation on Gas-To-Liquids (GTL) diesel fuel, in order to demonstrate the extent of exhaust emission reductions which are enabled by the properties of this fuel. The engine hardware changes employed comprised the fitment of re-specified fuel injectors and the reduction of the compression ratio from 18:1 to 15:1, as well as a re-optimisation of the software calibration. The demonstration vehicle has achieved a NOx emission of less that 0.08 g/km in the NEDC test cycle, while all other regulated emissions still meet the Euro 4 limits, as well as those currently proposed for Euro 5. CO2 emissions and fuel consumption, were not degraded with the optimised engine. This was achieved whilst employing only cost-neutral engine modifications, and with the standard vehicle exhaust system (oxidation catalyst and diesel particulate filter) fitted.

In view of limited crude oil resources, alternative fuels for internal combustion engines are currently being intensively researched. Synthetic fuels from natural gas offer a promising interim option before the development of CO2-neutral fuels. Up to a certain degree, these fuels can be tailored to the demands of modern engines, thus allowing a concurrent optimization of both the engine and the fuel. This paper summarizes investigations of a Gas-To-Liquid (GTL) diesel fuel in a modern, post-EURO 4 compliant diesel engine. The focus of the investigations was on power output, emissions performance and fuel economy, as well as acoustic performance, in comparison to a commercial EU diesel fuel. The engine investigations were accompanied by injection laboratory studies in order to assist in the performance analyses.

The results of a comprehensive experimental investigation into the exhaust emission performance and combustion properties of neat and blended Gas-To-Liquids (GTL) diesel fuel are presented. A sulphur-free European diesel fuel was used as the reference fuel, and two blends of the GTL diesel fuel with the reference fuel, containing 20% and 50% GTL diesel fuel respectively, were investigated. The study was based on a Mercedes Benz 2.2 liter passenger car diesel engine and presents emission data for both the standard engine calibration settings, as well as settings which were optimized to match the characteristics of each fuel. Vehicle emission tests showed that the GTL diesel fuel results in reductions in HC and CO emissions of greater than 90%, while PM is reduced by 30%, and NOx remains approximately unchanged. Engine bench dynamometer tests showed reductions in soot of between 30% and 60%, and NOx reductions of up to 10% with the GTL diesel fuel, depending on the operating point.

Diesel exhaust particle number concentrations and size distributions, as well as gaseous and particulate mass emissions, were measured during steady-state tests on a US heavy-duty engine and a European passenger car engine. Two fuels were compared, namely a Fischer-Tropsch diesel fuel manufactured from natural gas, and a US D2 on-highway diesel fuel. With both engines, the Fischer-Tropsch fuel showed a considerable reduction in the number of particles formed by nucleation, when compared with the D2 fuel. At most test modes, particle number emissions were dominated by nucleation mode particles. Consequently, there were generally large reductions (up to 93%) in the total particle number emissions with the Fischer-Tropsch fuel. It is thought that the most probable cause for the reduction in nucleation mode particles is the negligible sulphur content of the Fischer-Tropsch fuel. In general, there were also reductions in all the regulated emissions with the Fischer-Tropsch fuel.

The Fischer-Tropsch (FT) process can be used to synthesize diesel fuels from a variety of energy sources, including coal, natural gas and biomass. Diesel fuels produced from the FT process are essentially sulfur-free, have very low aromatic content, and have excellent ignition characteristics. Because of these favorable attributes, FT diesel fuels may offer environmental benefits over transportation fuels derived from crude oil. Previous tests have shown that FT diesel fuel can be used in unmodified engines and have been shown to lower regulated emissions. Whereas exhaust emissions reductions from these previous studies have been impressive, this paper demonstrates that far greater exhaust emissions reductions are possible if the diesel engine is optimized to exploit the properties of the FT fuels. A Power Stroke 7.3 liter turbocharged diesel engine has been modified for use with FT diesel.

Regulatory standards on diesel engines emissions will decidedly become more restrictive in coming years. This has led to the development and implementation of alternative fuels. The objective of this paper is to evaluate the potential of Sasol Fischer-Tropsch (FT) diesel fuel to improve the reduction of emissions in a direct injection diesel engine with a high pressure common-rail injection system (HDI engine from PSA Peugeot-Citroën). In principle, FT diesel fuel shows significant advantages in reducing emissions over a standard diesel fuel due to its low aromaticity, high cetane rating and high H/C rating. Initial tests with two 406 HDI Euro 2 vehicles with standard calibration showed very favourable trends on exhaust emissions in comparaison with reference fuel (CEC RF73-A-93 type). Sasol FT diesel fuel gave significant improvement on specific fuel consumption, and decreased the HC, CO, CO2 and particulate emissions without degrading NOx emissions.

Comparative exhaust emission tests were performed with five diesel fuels, namely a Sasol Fischer-Tropsch diesel, a fuel meeting the CARB diesel fuel specification, a fuel meeting the US 2-D diesel fuel specification, and two blends of the Fischer-Tropsch diesel and the 2-D diesel. Hot-start and cold-start heavy-duty transient emission tests were performed using a 1999 model year DDC series 60 engine. Regulated exhaust emissions with the Fischer-Tropsch diesel were significantly lower than with the 2-D and CARB diesel fuels, in both the hot-start and cold-start tests. When compared with test results obtained previously with a 1991 engine, it was found that the reduction in NOX with the Fischer-Tropsch fuel was smaller in the 1999 engine, while the reduction in PM was greater.