Internal Diesel Injector Deposits Research Articles

Development and Application of an Engine Test Method to Rate the Internal Injector Deposit Formation of Diesel Fuels and Additives

<div class="section abstract"><div class="htmlview paragraph">Design efforts to improve the hydraulic efficiency of high-pressure diesel fuel systems and thus further improve overall engine efficiency have resulted in the utilisation of low-spill control valves and reduced injector component clearances to reduce general leakage losses. Overall, these advances have contributed significantly to the high efficiency diesel engines of today. However, the combination of very high fuel pressures, cavitation and low fuel leakage volumes increases the heating of the remaining fuel, increasing temperature and, in turn, the propensity for deposits to form inside the injector. This deposit phenomenon is commonly known as Internal Diesel Injector Deposits (IDID) and can cause rough engine running and failed engine starts requiring injector cleaning or replacement. Methods studying this phenomenon are under development in the industry. Meanwhile this paper describes the development and application of an in-house engine test method to rate the IDID control performance of deposit control additives (DCA). A 2.0L, 4-cylinder light-duty engine is run with a fuel containing a contaminant to provoke the occurrence of deposit formation within a reasonable test duration. In ‘keep clean’ test mode the performance of the DCA is assessed based on its ability to prevent IDID symptoms that routinely manifest in unadditivated test runs, primarily between-cylinder deviation in exhaust port gas temperature as the operation of individual injectors is impaired by deposits. In ‘clean up’ test mode the DCA is assessed on its ability to reverse IDID symptoms that manifested in a preceding unadditivated test run. In initial tests the methodology has proved capable of differentiating between a novel DCA chemistry that exhibits good IDID control behaviour in keep clean and clean up modes and a conventional DCA chemistry that did not. Temperature deviations were reduced applying the novel DCA at premium dose in keep clean mode. In clean up mode, temperature deviations were reduced from the end of dirty up to the end of clean up, with premium plus dose rate of the novel DCA. In both cases the improvements were statistically significant at the 95% confidence level.</div></div>

Factors Influencing the Formation of Soft Particles in Biodiesel

<div class="section abstract"><div class="htmlview paragraph">In order to mitigate the effect of fossil fuels on global warming, biodiesel is used as drop in fuel. However, in the mixture of biodiesel and diesel, soft particles may form. These soft particles are organic compounds, which can originate from the production and degradation of biodiesel. Further when fuel is mixed with unwanted contaminants such as engine oil the amount soft particles can increase. The presence of these particles can cause malfunction in the fuel system of the engine, such as nozzle fouling, internal diesel injector deposits (IDID) or fuel filter plugging. Soft particles and the mechanism of their formation is curtail to understand in order to study and prevent their effects on the fuel system. This paper focuses on one type of soft particles, which are metal soaps. More precisely on the role of the short chain fatty acids (SCFA) during their formation. In order to do so, aged and unaged B10 was studied. The fuel matrixes were mixed with a calcium source such as calcium oxide (CaO), calcium carbonate (CaCO<sub>3</sub>) and engine oil. The importance of SCFA was studied by influencing the presence of the acids, by degrading the fuel, by the addition of formic acid and by inert gas bubbling. The created deposits and fuels mixtures were examined with the use of pH measurements, Fourier-transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC-MS) and ion chromatography (IC). Opposed to the expectations, the results indicate that SFCA in not the most important factor for the formation of soft particles. It is shown that the calcium sources influenced the consistency and amount of the created soft particles. From the tested contaminants, CaO showed the highest yield towards precipitates. While degradation of the fuels showed to be the most important factor to form soap type soft particles.</div></div>

Internal Diesel Injector Deposit Chemical Speciation and Quantification Using 3D OrbiSIMS and XPS Depth Profiling

<div class="section abstract"><div class="htmlview paragraph">The impact of internal diesel injector deposits (IDIDs) on engine performance, efficiency and emissions remains a major concern in the automotive industry. This has been compounded in recent years by fuel injection equipment developments and changes to diesel fuel towards ultra-low sulfur diesel (ULSD) and biodiesel as well as the introduction of new fuels such as hydrotreated vegetable oil (HVO). Prevention and mitigation of such deposit formation requires an understanding of the formation process, which demands a chemical explanation. The chemistry of these deposits therefore remains a key research interest to the industry using the latest analytical methodologies to inform and build further on previous investigations. In this work, 3D OrbiSIMS analysis using a time of flight-secondary ion mass spectrometer (ToF-SIMS) with hybrid Orbitrap<sup>TM</sup> functionality has been employed for chemical speciation and depth profiling of IDIDs in-situ on two injector needle samples from field failures in China and Eastern USA. The instrument’s soft gas cluster ion beam (GCIB) and high mass resolution enables unequivocal identification of chemistries from several classes of compounds. Here, chemistries identified include alkylbenzene sulfonates, zinc oxides, sodium and calcium salts, carboxylic acids, carbonaceous/polyaromatic hydrocarbons and metal substrate related material. With depth profiling, the distributions of these materials are traced throughout the deposit thickness. Given the semi-quantitative nature of SIMS data, X-ray photoelectron spectroscopy (XPS) depth profiling using an argon GCIB has also been employed to provide parallel data of atomic concentration through the deposit thickness. This data is complementary to SIMS as it places the chemical information in a quantitative context, most notably showing that despite the extreme intensities of salt material in the SIMS data, carbon is the main element throughout both IDIDs. Together the techniques show in general the more functionalized chemistries are at the deposit surface, with underlying salt layers and innermost layers of more amorphous organic material. These techniques represent a new method of comprehensive IDID characterization that affords diagnostic chemical information alongside elemental quantification, thus complementing previous studies.</div></div>

Use of ionic liquids to minimize sodium induced internal diesel injector deposits (IDIDs)

The first successful extraction of up to 99.1% of Na+ from a model diesel fuel at a Na+ concentration of just 3 mg kg−1 using a range of ionic liquids.

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.

Impact of fuel on real diesel injector performance in field test

This work assessed the potential impact of diesel fuel complying with the EN 590 standard on real diesel injector performance in a long-term field test. Injector deposit formation has been attributed to diesel fuel instability during storage in relation to fuel injection equipment (FIE) operating conditions. These deposits can occur at different locations within FIE and impact on fuel spray characteristics, causing threats to the proper functioning of the fuel injectors. The long-term field tests were performed with two new vehicles fitted with an advanced common rail (CR) fuel injection system, meeting the requirements of Euro 5. A high quality diesel fuel meeting the requirements of the EN 590 standard was used for both vehicles. A scanning electron microscope with energy dispersive X-ray spectrometry (EDS) and an electron backscatter diffraction (EBSD) detector was used for observation and imaging of external, coking injector deposits around the nozzle fuel-flow holes and internal diesel injector deposits (IDID) in the area of the nozzle needle. An elemental analysis was performed by energy dispersive X-ray spectroscopy analysis (EDX). Evaluation of the macroscopic characteristics revealed that, despite the formation of external and internal injector deposits, there was no measurable loss of flow through the injectors. As a result, while injector deposits have adverse impacts on some injector macroscopic characteristics, they did not cause a significant deterioration of the injectors’ operating characteristic and their real performance.

Prediction of threats caused by high FAME diesel fuel blend stability for engine injector operation

It is well known that the reduced stability of FAME diesel fuel blends is of particular threat to diesel engines and especially high pressure common rail (HPCR) systems operation. As has been ascertained, internal diesel injector deposits are more likely to form in modern diesel fuel systems because of their higher operating pressures and temperatures, which can intensify oxidation and decomposition of the chemically unstable components of diesel fuels, particularly those contained in FAME. This paper presents the results of accurate and sensitive evaluation of laboratory test methods for the determination of oxidation, storage and thermal diesel fuel stability, verified via dynamometer engine testing, from the point of view predicting the possibility of threats caused by aged diesel fuel with various FAME contents for HPCR in-system performance.

Types of internal Diesel injector deposits and counteracting their formation

The paper attempts to distinguish types of IDID (Internal Diesel Injector Deposits) with regard to the mechanism of formation, factors facilitating their formation and the method of identification. Investigations into their formation mechanism have been discussed in the paper. The results of the investigations into the chemical nature and probable source of these deposits have also been discussed. It has been pointed out that modern common rail fuel injection systems might be less tolerant to deposits due to tighter fitting tolerances, lower mass of parts and sophisticated injection strategies. Various approaches to IDID formation counteracting have also been discussed.

The reasons and adverse effect of internal diesel injector deposits formation

The paper report on the state of affairs so far in the scope of internal diesel injection deposits (IDID) issue affecting modern diesel high pressure common rail (HPCR) systems. Different types of deposits have been described and the factors supporting their creation. These deposits have been extensively studied to understand their formation mechanisms and composition. To this end an engine test procedure was developed to assess the deposit forming tendencies of various types. Findings of two long time dynamometer engine tests in which the course of the IDID formation and HPCR performance impairing was followed by measurement different engine parameters have been reported. Performance evaluation of HPCR injectors before and after tests have been presented also.

Internal Diesel Injector Deposits: Theory and Investigations into Organic and Inorganic Based Deposits

Internal Diesel Injector Deposits: Theory and Investigations into Organic and Inorganic Based Deposits