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Biofuels are a promising alternative to fossil fuels as their availability has been reduced during the last decades and they are the main sources of greenhouse gases emissions. Moreover, the targets of the international regulations include reduction of fossil fuels consumption, and improvement of the sustainability of the vehicle fleet. Blending gasoline with biofuels will result in changes in fuel blending procedures and combustion process especially for the gasoline direct injection (GDI) engines. In this article, flame visualization using chemiluminescence techniques in a Single Cylinder Optical Research Engine (SCORE) is presented, with an adjusted intake pressure of 850 mbar and early intake single injection (280 CAD BTDC), by using 100% hydrocarbon-based gasoline, E10 (90% gasoline - 10% ethanol) and ETBE20 (80% gasoline - 20% ethyl tert-butyl ether). ETBE20 is a potential alternative for E10, as it contains the same amount of renewable fuel and has low water solubility.

In the frame of circular economy, wastes are perceived as sources not only for the recovery of high added-value compounds but also for energy production. Coffee is one of the most popular beverages with the consumption continuously increasing and generating huge amounts of solid residues in return. This solid waste after the extraction of the coffee beverage is known as Waste or Spent Coffee Grounds (WCG). Among others, the valorization has the potential to be directed as a bioresource for sustainable energy and particularly for the production of alternative liquid fuels for internal combustion engines. The aim of the current study is to formulate alternative fuel from WCG and to examine the fundamental properties per relevant specifications and requirements. Parameters related to stability, cold flow properties, lubricating characteristics and ignition quality are studied in comparison with other types of biodiesel fuel.

Many incidents associated with filter plugging have extensively been reported in microbially contaminated diesel and biodiesel fuel systems, especially under long term storage conditions. In this study a quantitative assessment of the undesirable insoluble solids produced in contaminated biodiesel fuels was carried out in order to evaluate their evolution rate during biodeterioration. For this purpose, a series of contaminated biodiesel fuel microcosms were prepared and stored for six months under stable conditions. The quantity of the particulate contaminants was monitored during storage by a multiple filtration technique which was followed at the end by a comparison with the active bioburden per ATP bioluminescence protocol. Additionally, identical microcosms were treated with a commercially available biocide in order to examine the latter’s activity both on solids formation and the microbial proliferation.

Renewable substitutes for transportation fuels have had an important role in the recent years. Hydrotreated vegetable oils (HVO) are produced from two stage hydrotreating process of vegetable oils. The second stage of this hydroteating process is used to convert normal paraffins to isoparaffins in order to improve cold flow properties of these fuels. As this stage is a high energy consuming process, it is of interest to investigate the characteristics and the usability of the first stage of hydrotreatment of lipids. This paper examines the properties of alternative fuel derived from the hydrotreatment of used cooking oil (UCO). Used cooking oil is a difficult feedstock for biodiesel production. The hydrotreating of UCO converts triglycerides mainly into normal paraffins within the diesel fuel range. The hydrotreated UCO (HUCO) has an excellent cetane number and cetane index (>90), but very poor cold flow properties.

In accordance to the current environmental policy of the European Union by 2020, 10% of the transport fuel in every country comes from renewable sources such as biofuels. One of the most popular biofuels, (bio) ethanol is a probable suitable candidate for addition in diesel fuel because of its cleaner combustion and the ability to reduce emissions of gaseous pollutants. However, its use presents some important problems, attributed mainly to its incompatibility with diesel fuel during mixing due to the difference in the polarity. For this reason, substances that act as stabilizers of these mixtures are used, one of the most suitable being butanol. This substance is compatible with diesel fuel and ethanol, acting as a chemical bridge between the two, but also exhibits positive combustion behavior, as it is also an oxygenate that can be produced from renewable sources as well. The aim of this work was to investigate the behavior of diesel-ethanol mixtures using butanol as co-solvent.

Additives that enhance properties, such as cetane number or cold flow, are introduced in diesel-biodiesel blends in order to upgrade its performance as well as to aid its handling and distribution. Furthermore, in order to protect the engine and fuel operating system equipment, diesel fuel may be treated with corrosion inhibitors and detergents. However, additives could also have an impact on other parameters beyond those that they are intended to boost. In the present study the effect of diesel fuel improvers on fuel’s microbial stability is examined. An additive-free ultra low sulfur diesel (ULSD) was blended with Soybean Fatty Acid Methyl Esters (FAME) and the resulting blend was treated separately with a series of commercially available diesel fuel additives.

The aim of this study is to investigate the lubricity of hydrocarbons that constitute components of petroleum diesel fuel. A number of typical hydrocarbon compounds were selected as representative of the group types of alkanes (paraffins), cycloalkanes (naphthenes) and aromatics, similar to those that are present in diesel fuel. The lubricity of these substances was examined in a High Frequency Reciprocating Rig (HFRR) apparatus according to the ISO 12156-1 standard method. Thereafter, a series of diesel surrogate fuel were prepared from the above substances based on literature data for diesel fuel composition and on the previously obtained results. These model fuels were assessed regarding their lubricating performance in order to evaluate how each individual component can affect the lubricity of the final fuel.

FAME is the most common renewable component of conventional automotive diesel. Despite the advantages, biodiesel is more susceptible to oxidative deterioration and due to its chemical composition as well as its higher affinity to water, is considered to be a favorable substrate for microorganisms. On the other hand, apart from biodiesel, alcohols are considered to be promising substitutes to conventional diesel fuel because they can offer higher oxygen concentration leading to better combustion characteristics and lower exhaust emissions. More specifically, n-butanol is a renewable alcohol demonstrating better blending capabilities and properties when it is added to diesel fuel, as its composition is closer to conventional fuel, when compared ethanol to for example. Taking into consideration the alleged disinfectant properties of alcohols, it would be interesting to examine also the microbial stability of blends containing n-butanol in various concentrations.

The aim of this study was to investigate the effect of a variety of phenolic type antioxidant additives on the microbial stability of biodiesel and diesel/biodiesel blends. Six synthetic phenolic type antioxidant agents were added in FAME at concentrations up to 1000 ppm. Treated FAME was also blended with Ultra Low Sulfur Diesel (ULSD) fuel at a concentration of 7% v/v in order to examine the activity of the substances in the final blends. The oxidation stability in the presence of the phenolic compounds was determined by carrying out measurements under accelerated oxidation process in the Rancimat unit. The effectiveness of those antioxidant agents against microbial contamination in biodiesel fuel was studied under certain testing protocols for detecting microbiological activity in the fuel supply chain and for evaluating antimicrobials against fuel bio-deterioration.

The fuel supply chain faces challenges associated with microbial contamination symptoms. Microbial growth is an issue usually known to be associated with middle distillate fuels and biodiesel, however, incidents where microbial populations have been isolated from unleaded gasoline storage tanks have also been recently reported. Alcohols are employed as gasoline components and the use of these oxygenates is rising, especially ethanol, which can be a renewable alternative to gasoline, as well. Despite their alleged disinfectant properties, a number of field observations suggests that biodeterioration could be a potential issue in fuel systems handling ethanol-blended gasoline. For this reason, in this study, the effect of alcohols on microbial proliferation in unleaded gasoline fuel was assessed. Ethanol (EtOH), iso-propyl alcohol (IPA) and tert-butyl-alcohol (TBA) were evaluated as examples of alcohols utilized in gasoline as oxygenates.

The present work investigates the effect of low levels CO2 addition on the combustion characteristics inside a single cylinder optical engine operated under low load conditions. The effects of dilution levels (up to 7.5% mass flow rate CO2 addition), the number of pilot injections (single or double pilot injections) and injection pressure (25 or 40 MPa), are evaluated towards the direction of achieving a partially premixed combustion (PPC) operation mode. The findings are discussed based on optical measurements and via pressure trace and apparent rate of heat release analyses in a Ricardo Hydra optical light duty diesel engine. The engine was operated under low IMEP levels of the order of 1.6 bar at 1200 rpm and with a CO2 diluent-enhanced atmosphere resembling an environment of simulated low exhaust gas recirculation (EGR) rates. Flame propagation is captured by means of high speed imaging and OH, CH and C2 line-of-sight chemiluminescence respectively.

Problems with the low-temperature operability performance of biodiesel in blends with petroleum diesel are infrequent, but continue to limit the use of biodiesel during winter months. A troubling aspect of this problem is that in some cases precipitates above the blend Cloud Point (CP) have been detected and have led to plugging of fuel filters and subsequent engine stalling, as well as plugging of fuel dispenser filters. Many researchers found that the saturated monoglyceride content was a main component of the material that was found on plugged fuel filters, as well as traces of Saturated DiGlycerides (SDG), were also present on the plugged fuel filters. This is the reason which forced the organization of standardization to suggest a procedure in order to predict the content of the Saturated MonoGlycerides (SMG) even with uncertainty which can vary from −50% to +50%. The model which was used will be the same as that which was introduced in the Annex C of EN 14214+A1:2013.

For many years Rancimat was the only standardized method for measuring the oxidation stability of FAME and FAME/diesel blends. However this method is not applicable to pure conventional petroleum products and so the effect of FAME on diesel fuel stability could not be evaluated directly. Recently a Rapid Small Scale Oxidation Test (RSSOT) that covers the determination of the stability of biofuels and petroleum products was developed and standardized. In this study the oxidation stability of seven different types of FAMEs was assessed, either neat or blended with three types of ULSD fuel, by employing both the Rancimat and the RSSOT accelerated oxidation methods. The determinations from either test were analyzed and a comparative assessment of these two method was carried out.

The scope of this work is to examine the use of hydroprossed used cooking oils as substitute for automotive diesel fuel. Hydroprocessing is an alternative method for the transformation of vegetable oils into high quality transport fuels, even if the quality of the oils is low, such as used cooking oils. In the present work, the utilization of hydroprocessed used cooking oil (HUCO) as neat fuel was proved to be very difficult, due to its very poor cold flow properties; therefore, mixtures of the HUCO with low quality middle distillates (a low cetane number gasoil and a light cycle oil) were prepared and evaluated. Throughout the process the formed blends were evaluated according to the european standard EN 590. The following points were mainly recorded: The lower density of HUCO was beneficial, permitting the use of poor quality distillates, in specific concentrations, and the high cetane number of HUCO was appreciable, improving the worse behavior of the other components.

The ability of a catalyst to enhance the performance of synthesized biobased lubricant basestock was investigated in this study. Pomace olive oil, cottonseed oil, used frying oil and methyl oleate were utilized as starting materials for the production of the biobased lubricants and a two stages transesterification methodology was followed. Initially the oils were converted to their corresponding fatty acid methyl esters via methanolysis. The resulting methylesters were subsequently transesterified with TMP producing the desired oleochemical ester. These syntheses were carried out in the presence of either sodium methoxide or Ca/TEA alkoxide as catalysts. Following the purification phase, the synthesized esters were evaluated as potential biolubricants regarding their physicochemical properties such as viscosity index, pour point and acid value.

Cylinder pressure measurements are common practice for internal combustion reciprocating engines during field or lab applications for the purpose of combustion analysis, condition monitoring etc. The most accurate method is to measure cylinder pressure using a crank angle encoder as a trigger source to guarantee cylinder pressure measurement at predefined crank angle events. This solution, even though favorable, presents a number of practical difficulties for field applications and increased cost, for this reason its use is practically restricted to lab applications. Therefore a commonly used approach for ad hoc measurements is to digitize samples at fixed time intervals and then convert time into crank angle assuming a constant rotational speed. But if engine rotational speed is not constant within the engine cycle this may result to incorrect cylinder pressure CA referencing.

High efficiency, power concentration and reliability are the main requirements from Diesel Engines that are used in most technical applications. This becomes more important with the increase of engine size. For this reason the aforementioned characteristics are of significant priority for both marine and power generation applications. To guarantee efficient engine operation and maximum power output, both research and commercial communities are increasingly interested in methods used for supervision, fault-detection and fault diagnosis of large scale Diesel Engines. Most of these methods make use of the measured cylinder pressure to estimate various critical operating parameters such as, brake power, fuel consumption, compression status, etc. The results obtained from the application of any diagnostic technique, used to assess the current engine operating condition and identify the real cause of the malfunction or fault, depend strongly on the quality of these data.

This study investigates the impact of mid-high biodiesel blends on the criteria and PAH emissions from a modern pick-up diesel vehicle. The vehicle was a Euro 4 (category N1, subclass III) compliant common-rail light-duty goods pick-up truck fitted with a diesel oxidation catalyst. Emission and fuel consumption measurements were performed on a chassis dynamometer equipped with CVS, following the European regulations. All measurements were conducted over the certification New European Driving Cycle (NEDC) and the real traffic-based Artemis driving cycles. Aiming to evaluate the fuel impact on emissions, a soy-based biodiesel, a palm-based biodiesel, and an oxidized biodiesel obtained from used frying oils were blended with a typical automotive ultra-low-sulfur diesel at proportions of 30, 50 and 80% by volume. The experimental results revealed that CO₂ emissions and fuel consumption exhibited an increase with biodiesel over all driving conditions.

In this study, regulated, unregulated exhaust emissions and fuel consumption with ultra low sulphur diesel and soy-based biodiesel blends at proportions of 10 and 30% v/v have been investigated. A Euro 4 compliant SUV, equipped with a 2.2 litre common-rail diesel engine and an oxidation catalyst was tested on a chassis dynamometer with constant volume sampling (CVS) technique. Emission and fuel consumption measurements were performed over the New European Driving Cycle (NEDC) and the non-legislated Artemis driving cycles which simulate urban, rural, and highway driving conditions in Europe. The regulated pollutants were characterized by determined NOx, PM, CO, and HC. CO2 was also quantified in the exhaust. Overall, 16 PAHs, 4 nitro-PAHs, 6 oxy-PAHs, 13 carbonyl compounds and particulate alkanes ranged from C13 to C35 were determined in the exhaust.

To reduce the fuel related logistic burden, NATO Armed Forces are advancing the use of a single fuel for both aircraft and ground equipment. To this end, F-34 is replacing distillate diesel fuel in many applications. Yet, unacceptable wear due to poor lubricity was illustrated by tests conducted with kerosene on High Frequency Reciprocating Rig. Therefore, HFRR tests were performed with fatty acid methyl esters of sunflower, palm, cotton-seed, tobacco-seed, olive, rape-seed and used frying oils, at volume concentrations from 0.05% to 0.6%. This study showed that the biodiesels used, produced a significant decrease in the wear scar diameter at concentrations of 0.2% to 0.4 %. Biodiesels derived from non-polyunsaturated oils, such as palm and olive gave better lubrication at certain concentrations.