Jim Barker

Diesel Injector Deposits - An Issue That Has Evolved with Engine Technology

Diesel engines have traditionally been favoured in heavy-duty applications for their fuel economy, robustness, reliability and relative lack of fuel sensitivity. Recently it has seen a growth in its popularity in light duty applications due particularly to its fuel efficiency. However, as the engine technology and particularly the fuel injection equipment has evolved to meet ever stricter emissions legislation the engines have become more sensitive to deposit formation resulting from changes in fuel quality. This paper reviews bouts of concern over diesel fuel injector deposits, possible causes for the phenomenon and test methods designed to screen fuels to eliminate problems.

Chirality and diastereoselection in the μ-oxo diiron complexes L2Fe–O–FeL2 (L = bidentate salicylaldiminato)

A number of bis(salicylaldiminato) (Schiff base) complexes of Fe(II) i.e. L(2)Fe with a variety of ligand substituents and functionality are synthesised, usually by salt metathesis but on one occasion via the (sal)(2)Fe complex, and characterised by standard methods. Two molecular structure determinations indicate the expected tetrahedral geometry. Treatment with dry oxygen yielded the Fe(III) complexes [(FeL(2))(2)-mu-O], generally in high yield and in the absence of hydroxylated impurities; one bulky complex L(2)Fe gave no oxidation product for steric reasons, and one hydroxyl-substituted compound gave an insoluble product. Five molecular structures of these [(FeL(2))(2)-mu-O] compounds were determined. All were homochiral in the sense that the absolute configuration at Fe was the same for both atoms. Three of the structures - those based on optically pure salicylaldimine ligands - were diastereomeric. For two, the diastereomers observed are those predicted on the basis of steric considerations, while a third highly distorted and congested structure represents the unexpected diastereomer. Powder X-ray diffraction confirms high phase purity of the bulk samples (i.e. they are diastereomerically pure to the level detectable). These investigations, coupled with molecular structure and NMR studies on model gallium complexes, indicate that the diastereoselection arises from cooperative interactions across the oxo bridge.

A Novel Technique for Investigating the Nature and Origins of Deposits Formed in High Pressure Fuel Injection Equipment

Recent developments in diesel fuel injection equipment coupled with moves to using ULSD and biodiesel blends has seen an increase in the number of reports, from both engine manufacturers and fleet operators, regarding fuel system deposit issues. Preliminary work performed to characterise these deposits showed them to be complicated mixtures, predominantly carbon like but also containing other possible carbon precursor materials. This paper describes the application of the combination of hydropyrolysis, gas chromatography and mass spectrometry to the analysis of these deposits. It also discusses the insights that such analysis can bring to the constitution and origin of these deposits.

Insights into deposit formation in high pressure diesel fuel injection equipment

The need to meet the US 2007 emissions legislation has necessitated a change in Diesel engine technology, particularly to the fuel injection equipment (FIE). At the same time as these engine technology changes, legislation has dictated a reduction in fuel sulphur levels and there has also been increased use of fatty acid methyl esters (FAME) or biodiesel as a fuel blending component. The combination of changes to the engine and the fuel has apparently led to a sharp rise in the number of reports of field problems resulting from deposits within the FIE. The problem is usually manifested as a significant loss of power or the engine failing to start. These symptoms are often due to deposits to be found within the fuel injectors or to severe fouling of the fuel filter. The characteristics of the deposits found within different parts of the fuel system can be noticeably different. A variety of analytical techniques have been investigated to gain knowledge of the characteristics of these different forms of deposit. Work has also been performed to characterise some of the fuels that may be causing the deposits. This paper concentrates on the characterisation of deposits found specifically in the fuel injectors. Deposits found within different parts of the injector have been analysed using, Gas Chromatography with Mass Spectrometry detection (GC/MS), Fourier Transform Infra-red analysis (FTIR), Inductively Coupled Plasma spectroscopy (ICP), Nuclear Magnetic Resonance spectroscopy (NMR) and elemental analysis. Fuel samples that have been associated with the deposit formation have also been analysed. The techniques discussed are high resolution mass spectrometry, and ICP. The results are also placed in context with previously published work on both filter and injector deposits.

Organic-soluble optically pure anionic metal complexes PPh4[MIII(S,S-EDDS)]·2H2O (M = Fe, Co, Cr)

The first organic-soluble, optically and diastereomerically pure EDDS metal complexes have been synthesised. A number of synthetic approaches were attempted, but finally the tetraphenylphosphonium series emerged as providing readily accessible compounds of trivalent Cr, Fe and Co in reasonable yields via the silver salts without the need to perform ion-exchange chromatography. The species PPh(4)[M(III)(S,S-EDDS)] are very soluble in methanol, acetonitrile and even THF but isolation was facilitated by addition of stoichiometric water giving the highly crystalline but still conveniently soluble title compounds. The structures of the three isomorphous crystals comprise H(2)O-bridged extended hydrogen bonded structures with large channels occupied by the counterion molecules. The magnetic properties and circular dichroism spectra are reported along with comparative data for water-soluble NH(4)[Fe(III)(S,S-EDDS)]. Phase purity (and hence diastereomeric purity) in the paramagnetic systems is assessed through powder XRD. The practical utility of this type of compound was confirmed by optical resolution of (+/-)-[Ru(II)(bpy)(3)]Cl(2).

Information on the Aromatic Structure of Internal Diesel Injector Deposits From Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS)

The nature of internal diesel injector deposits (IDID) continues to be of importance to the industry, with field problems such as injector sticking, loss of power, increased emissions and fuel consumption being found. The deposits have their origins in the changes in emission regulations that have seen increasingly severe conditions experienced by fuels because of high temperatures and high pressures of modern common rail systems and the introduction of low sulphur fuels. Furthermore, the effect of these deposits is amplified by the tight engineering tolerances of the moving parts of such systems. The nature and thus understanding of such deposits is necessary to both minimising their formation and the development of effective diesel deposit control additives (DCA). The focused ion beam technique coupled with time of flight secondary -ion mass spectrometry (ToF-SIMS) has the ability to provide information on diesel engine injector deposits as a function of depth for both organic and inorganic constituents. Our previous work with this novel technique is unique in that it has shown layering effects in deposits which may be due to the residual fuel either evaporating and leaving residues or being unable to keep insoluble residues in solution during the injection process. As part of our on-going work to understand the nature of field deposits, the aromatic compounds present have been investigated. To help interpret the results for the aromatic structures present, spectra of a model polycyclic aromatic hydrocarbon (PAH), coronene (C24H12), and coal tar pitch (CTP) have been used as a basis to determine the ring structure of internal diesel; deposits. This work confirms the presence of aromatic ring structures of greater than six rings in composition in injector needle carbonaceous deposits. Introduction The current industry interest in internal diesel injector deposits (IDID) shows no sign of decline. In fact, CRC (Central Research Council Diesel Performance Group-Deposit Panel Bench/Rig/Investigation sub panel), CEN (Committee European de NormalisationTC19/WG24Injector Deposit Task Force, engine test, and CEC (Coordinating European Council TDFG-110) in Europe have sub committees and panels investigating the production and characterization of these deposits. This interest continues because injector malfunction is manifested in: • Reduced fuel economy • Higher emissions • Misfiring

A study of the reactivity of (methyl 2-acetamidoacrylate)-tricarbonyliron(0) leading to a novel synthesis of β,β,β-trialkyl α-amino acids

Abstract (Methyl 2-acetamidoacrylate)tricarbonyliron(0) ( 3 ) reacts with 2 equivalents of methyllithium to give methyl N -acetylalaninate ( 4 ) and 2-acetamido-4-oxopentanoate ( 5 ) when the reaction is quenched with trifluoroacetic acid. Production of methyl N -acetylalaninate is dependent only on the presence of trifluoroacetic acid, and the ratio of 4 to 5 generated in these reactions is related to the quantity of trifluoroacetic acid used to quench them. Addition of two equivalents of methyllithium followed by tertiary haloalkanes gives protected β,β,β-trialkyl α-amino acids which may be hydrolysed to give tert-leucine ( 13 ) and the new α-amino acids 2-amino-3,3-dimethylpentanoic acid ( 14 ) and 2-amino-3,3-dimethylhexanoic acid ( 15 ).

Surprising reactivity of (methyl 2-acetamidoacrylate)tricarbonyliron(0) leading to the synthesis of β,β,β,-trialkyl α-amino acids

Addition of methyllithium followed by tertiary haloalkanes to readily available and air-stable (methyl 2-acetamidoacrylate)tricarbonyliron(0)1, gives protected β,β,β-trialkyl α-amino acids which are hydrolysed to give tert-leucine 10 and the new α-amino acids 2-amino-3,3-dimethylpentanoic acid 11 and 2-amino-3,3-dimethylhexanoic acid 12.

Addressing the Issue of Fuel Filter Fouling with Recent Changes in Fuel Quality

The recent introduction of biodiesel blends to the U.S. market has coincided with an increase in the reported problems of fouling of fuel filters and fuel injection equipment, manifested in power loss, noise, vibration, and increased filter changes. However, the introduction of biodiesel has to a large extent coincided with the introduction of ultra low sulfur diesel fuel and changes in engine technology, leading to higher fuel injection pressures. It is thus proposed that current incidences of fouling are not a problem brought about solely as a result of the introduction of biodiesel. A review of known fuel degradation mechanisms suggests that the effects of increased fuel pressure and also high shear environments should be examined as a probable cause of increasing deposit formation. Deposit formation on both fuel filters and injectors has previously been attributed to a variety of sources including: Biological contamination, both aerobic and non-aerobic, water contamination, adulteration with lubricating oil, fuel additive interactions, and biodiesel degradation. The deposits currently being encountered appear to be more akin to the high carbon content particles found in diesel exhaust than those previously described and are frequently found in the presence of deposit precursor molecules. This paper concentrates on the issue of fuel filter fouling, presents the analysis of currently encountered deposits, relates these results to some of the degradation mechanisms alluded to above, and suggests possible precursor molecules in fuels both pre and post stressing to support the proposed mechanisms. It is also shown that existing fuel quality tests do not correlate well with reported fouling propensity, suggesting that new test methods are required to ensure future fuels are fit for purpose.

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

Studies of diesel system deposits continue to be the subject of interest and publications worldwide. The introduction of high pressure common rail systems resulting in high fuel temperatures in the system with the concomitant use of fuels of varying solubilizing 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 analyzed 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 yielding both chemical and metrological characteristics of the deposits. Fourier Transform Infrared Microscopy (FTIRM), and Time-of- Flight Secondary Ion Mass Spectrometry (ToFSIMS) will be used to describe the surface characteristics. Measurements from a Profile meter will be used to estimate deposit surface roughness and data from Scanning Electron Microscopy (SEM) will be employed to describe the morphology. The final techniques described will be Direct Analysis In Real Time Mass Spectrometry (DARTMS) using ambient mass spectrometry. and Fourier Transform Ion Cyclotron Resonance Mass spectrometry (FTICRMS) The advantage of the DART 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 analyzing 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 analyzing and providing the potential characterization of JFTOT deposits. The FTICRMS will be used to assign species in the JFTOT test fuels both pre and post test.