The analysis of diesel and related fuels, new fuels and components by mass spectrometry and other techniques for propensity for fouling in common-rail diesel injection systems

Abstract

Over the last decade, fuel injector deposits in common rail diesel engines have increased in incidence. Concurrently, increasingly strict emission legislation has resulted in multiple changes to both diesel fuel composition and fuel injection systems. Much interest surrounds these deposits due to associated field performance issues.

Novel analytical approaches were developed and applied for the characterisation of deposit components and deposit and non-deposit forming fuels from the field, using multiple chromatography and mass spectrometry techniques. Identification of recognised and currently unrecognised deposit forming components, and a greater understanding of the chemistry of the deposits and the diesel fuel through comparing and contrasting of complimentary data was achieved.

A targeted screening method was developed for known deposit forming component classes and applied to characterise diesel fuels and various FIE deposits. Positive ion electrospray ionisation ultrahigh pressure supercritical fluid chromatography mass spectrometry (ESI UHPSFC-MS) afforded the detection of fatty acid methyl esters (FAMEs), FAME oxidation products, monoacylglycerols and sterol glucosides, while negative ion ESI UHPSFC-MS afforded detection of free fatty acids. Additionally polyisobutylene, polypropylene glycol and additional additives were observed within fuel filter samples. Internal diesel injector deposit (IDID) results were indicative of possible metal carboxylate salt or aged fuel IDIDs.

Analysis protocol flow trees were also devised from this work to assist analysts with characterisation of (IDID) components in fuels (diesels, biodiesels), IDIDs and fuel filter deposits, as well as fuels.

A new species (fatty acid sterol esters) was identified from biodiesel within mineral diesels blends, believed to be unseen previously and currently an unrecognised deposit-forming component.

Further advancement of the analysis method for jet fuel thermal oxidation test (JFTOT) rod deposits and associated diesel fuels, firstly to validate previously unexpected results and to optimise sample preparation methodologies.

A novel positive ion ESI UHPSFC-MS method was developed for the detection and quantitation of the new fiscal fuel marker ACCUTRACE™S10, assisting HMRC to combat fuel laundering, with reported losses of £1.1 billion per annum at present and limiting the damage to vehicles resulting from using adulterated fuel.

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Identifiers

ORCID for Graham Langley: orcid.org/0000-0002-8323-7235

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