The Application of New Approaches to the Analysis of Deposits from the Jet Fuel Thermal Oxidation Tester (JFTOT).

Paper #:
  • 2017-01-2293

  • 2017-10-08
Studies of diesel system deposits continue to be the subject of interest and publications worldwide. The introduction of high pressure and temperature common rail systems with the concomitant use of fuels of varying solubilising ability (e.g. ULSD and FAME blends) have seen deposits formed at the tip of the injector and on various internal injector components. Though deposit control additives (DCAs) have been successfully deployed to mitigate the deposit formation, work is still required to understand the nature and composition of these deposits. The study of both tip and internal diesel injector deposits (IDID) has seen the development of a number of bench techniques in an attempt to mimic field injector deposits in the laboratory. One of the most used of these is the jet fuel thermal oxidation tester or JFTOT (ASTM D3241). The tester was originally designed to assess the oxidation of jet fuel based on the principle that low stability fuels produce deposits that form on metal surfaces. Recently it has been modified so that under suitable conditions it may be used to determine the deposit forming potential of diesel fuels. The JFTOT technique has been used by a number of groups to try and understand diesel injector deposits. The ineradicable nature of the material on the JFTOT tube has seen the deposits analysed by laser scanning microscopy, ellipsometry and recently infra-red microscopy. Other methods have been invasive involving either solvent washing or scraping off the deposit. In this paper other techniques for the analysis of deposits will be described. Three separate techniques will be described. Fourier Transform Infra-red Microscopy (FTIRM) will be used to describe the surface characteristics, whilst Time of Flight Secondary Ion Mass Spectrometry (TofSIMS) will be used to understand the layer characteristics of any deposit. The final technique described will be direct analysis in real time mass spectrometry (DART) using ambient mass spectrometry. The advantage of the method is that mixtures and objects can be subjected to mass spectrometric analysis with the minimum of pre-treatment and sample preparation. Thus the technique is well suited for analysing deposits on JFTOT tubes as it requires little sample preparation. A number of studies of materials deposited on JFTOT tubes will be described showing the suitability of these techniques for analysing and providing the potential characterisation of JFTOT deposits.
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