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Internal diesel injector deposits (IDID) are now a well understood phenomenon and a standard test procedure has been developed and partially approved by the Coordinating European Council (CEC). The engine test procedure has been approved for simulation of sodium soap deposits by dosing the test fuel with a sodium salt and dodecenyl succinic acid (DDSA), whilst amide lacquer deposits simulation by dosing the test fuel with a low molecular weight (MWt) polyisobutylene succinimide (PIBSI) is still under development. The solubility of these contaminants in the base fuel should be reasonably constant to achieve consistent results. With the introduction of diesel from varying sources, this study focused on the effect of near-zero aromatics EN 15940 compliant gas-to-liquids GTL diesel, very similar to hydrotreated vegetable oil (HVO), on IDID severity across two different engine platforms, and the response of a modern deposit control additive.

The success of modern diesel passenger cars is, to some extent, attributable to the advent of common rail diesel injection technology. Today almost all new diesel engines use this technology which is characterised by high fuel injection pressure and very small diameter nozzle holes. The industry rapidly developed a new test procedure to assess a fuel's propensity to cause injector fouling and also to assess the ability of additives to clean and to keep such injectors clean. The CEC F-98-08 DW10 test procedure was approved in March 2008 by the CEC and is now considered an industry standard test method. The test method requires 1ppm zinc to be dosed into all test fuels in order to accelerate injector fouling. This paper presents DW10 test results for gas-to-liquids (GTL) diesel. A similar test method, using a different engine, was developed in-house and showed good correlation with the DW10 test.

There is a worldwide drive to reduce the dependence on fossil fuels, mainly driven by volatility in the crude oil price, political instability in oil-producing countries and environmental concerns. In several European countries, diesel passenger cars outsell gasoline-powered cars by a significant margin. Common rail diesel injection technology has played a significant role in making diesel engines more acceptable in light-duty applications, given the significantly improved emissions (due to better atomization) and engine noise offered by this technology. These developments have contributed to a renewed interest in alternative diesels like biodiesel and Gas to Liquid (GTL) diesel. Recently, CEN TS 15940:2012 was approved for publication. This specification will enable paraffinic diesel (including GTL diesel) to be sold commercially as a neat fuel or as a blend, containing up to 7% fatty acid methyl ester biodiesel (FAME).

The combination of high crude oil prices, energy security concerns and environmental drivers have resulted in an increased focus on alternative fuels. Gas to liquids (GTL) diesel is considered to be a promising alternative diesel fuel, given that it can be used directly as a diesel fuel or be blended with petroleum-derived diesel or biodiesel. GTL diesel fuels are predominantly paraffinic and possess several excellent inherent properties including virtually zero sulfur, very low aromatics (≺1%) and very high cetane values (typically ≻75). Currently GTL diesel is mostly sold into the European market as a blend stock for the extending and upgrading of petroleum-derived diesel fuels. Given GTL diesel's inherent paraffinic nature, the density of this product is below the European minimum 820 kg/m₃ EN590 specification (at 15°C).

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.