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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.

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.

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 lubricating efficiency is an important property of diesel fuel since several diesel engine parts, such as pumps and injectors, are lubricated by the fuel itself only. The evolution of oxidation products during oxidative deterioration may as well affect the lubricating properties of the biodiesel fuel blends and thus the proper functioning of a diesel engine. In this study Fatty Acid Methyl Esters were produced from various types of feedstock that significantly differentiate in their fatty acid profile. Each methyl ester was blended with an Ultra Low Sulphur Automotive Diesel (ULSD) at a concentration of 7% v/v which is currently the maximum acceptable FAME content according to the European Standard EN590. The B7 biodiesel blends were evaluated regarding fundamental physicochemical properties as well as their lubricating efficiency. Oxidation stability was examined on a Rancimat apparatus according to EN 15751 standard.

Air pollution caused by diesel emissions, especially NOx, particulate matter, carbon monoxide and unburned hydrocarbons, has been a noteworthy matter. In Europe and the United States, legislative efforts towards improving air quality not only lead manufacturers to develop and introduce further improved emission control systems, but also the trigger demanding requirements on the oil industry towards producing advanced fuels. Therefore, much work on the effects of fuel properties on the emissions and engine performance has been performed worldwide. The fuels produced by the refineries usually comply with the existing specifications. However, alterations in the fuel properties may occur through the supply chain to the service stations due to failures of the distribution system or adulteration with lower value and taxation fuels (heating oil, marine diesel or industrial solvents).

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.

In this study, the transesterification process of 4 different vegetable oils (sunflower, rapeseed, olive oil and used frying oil) took place utilizing ethanol, in order to characterize the ethyl esters and their blends with diesel fuel obtained as fuels for internal combustion engines. All ethyl esters were synthesized using calcium ethoxide as a heterogeneous solid base catalyst. The ester preparation involved a two-step transesterification reaction, followed by purification. The effects of the mass ratio of catalyst to oil, the molar ratio of ethanol to oil, and the reaction temperature were studied on conversion of sunflower oil to optimize the reaction conditions in both stages. The rest of the vegetable oils were converted to ethyl esters under optimum reaction parameters. The optimal conditions for first stage transesterification were an ethanol/oil molar ratio of 12:1, catalyst amount (3.5%), and 80 °C temperature, whereas the maximum yield of ethyl esters reached 80.5%.

This study examines the impact of ETBE and ethanol addition on the main properties of motor gasoline. European Union mandates the use of biofuels in all transport fuels, according to the 2003/30/EC Directive. The addition of ethanol, a known octane enhancing component, in small proportions significantly increases the vapor pressure of the final gasoline, exceeding the maximum specification limits. ETBE (ethyl tert-butyl ether) is on the other hand an excellent but expensive octane enhancing component with beneficial impact on vapor pressure of the final gasoline. This paper examines the ability of ETBE to act as a stabilizer in gasoline - ethanol blends. Two gasoline samples with different chemical compositions and characteristics were prepared by blending basic refinery components. In each sample, ETBE was added in concentrations of 2, 4, and 6 % V/V respectively. In each of these ETBE - gasoline blends, ethanol was added in concentrations from 1 to 6 % V/V in 1% steps.

The objective of this paper was to evaluate the performance and airborne emissions of a diesel-water emulsion in 4 public buses operated in the area of Athens. The fuels used were a typical automotive diesel from the Greek market, a low sulfur diesel and a diesel-water emulsion of 13 % v/v water in low sulfur diesel. The fuels were characterized by exposing their physicochemical properties according to EN 590. The measurements of emissions of carbon monoxide, unburned hydrocarbons and carbon dioxide did not show any significant differences among the three fuels. The effects on NOx emissions can be termed as mixed, bearing also in mind that they represent engine operation at no load. The beneficial effect of the emulsified diesel fuel could be readily observed in the case of smoke opacity emissions.

In this paper, two diesel fuels were examined in a single cylinder diesel engine under an emissions measurement test of 72 hours total duration. The test cycle included steady state measurements and transient measurements. The two test fuels were a typical automotive diesel fuel, complying with the specifications of the EN 590 European standard for the year 2004 (sulfur content 350 mg/kg), and an ultra low sulfur diesel fuel containing 15% GTL, complying with the specifications of the EN 590 European standard for the year 2008 (sulfur content 10 mg/kg). Exhaust emissions measurements included gaseous pollutants (carbon monoxide, hydrocarbons, nitrogen oxides), and particulate matter emissions. In all cases carbon monoxide and hydrocarbons emissions were very low. Nitrogen oxides emissions did not show a clear trend, indicating that this pollutant is affected mainly by the engine and less by the fuel.

The present paper is an effort to evaluate ethanol in diesel fuel and its main alternatives. The fuels used were an ultra low sulfur diesel fuel containing 15% by volume gas-to-liquid (GTL), JP-5 and JP-8 fuels produced in Greece and biodiesel produced from animal fats. The fuels were tested for compliance to the respective specifications at the Fuels Laboratory of the National Technical University of Athens (NTUA). The test fuel matrix consisted of blends of 5-15 % by volume ethanol with diesel, JP-5, JP-8 and with mixtures of the above with 5% by volume biodiesel. The test fuels were used in a stationary single-cylinder diesel engine with indirect injection, in order to evaluate their performance and emissions under various loads.

The present paper aims to discuss the quality characteristics of Jet Fuels used in the Greek market in comparison with fuels used in other countries and to evaluate jet fuels along with diesel and biodiesel on a diesel engine. To establish the quality characteristics for Jet Fuels of the Greek market, fuel samples were collected from the local refineries on a regular basis, thus monitoring the fuel quality fluctuation over time. JP8, along with diesel and biodiesel, were used alone and in mixtures on a single cylinder stationary diesel engine. Emissions and volumetric fuel consumption were measured under various loads.

This work includes an assessment of the lubricity of Greek road diesel fuel of low sulfur content, and the effect of the addition of two different types of biodiesel which can be produced from raw materials abundant in the Mediterranean area. In this study, a series of representative fuels of the Greek fuel market were tested. In some of them, the lubricity was measured three times, during a period of three months from the day of each sample was produced. In all cases a decrease of the wear scar diameter (WSD) was measured; this behaviour could be attributed to the oxidation reactions that take place during the storage period. In order to monitor the effect of the addition of biodiesel on the lubricity of road diesel, biodiesels produced from sunflower oil and olive oil were used. The use of rape seed oil biodiesel as a diesel fuel substitute is a commercial event in Central Europe; in the United States the soybean oil biodiesel has been examined in detail.