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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.

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.

This paper describes some of the recent work carried out in our laboratory regarding the effects of novel oxygen and nitrogen containing compounds on the antiknock quality of unleaded gasoline and their effects on some other gasoline properties. In particular, the research included Research Octane Number (RON) measurements and the evaluation of the effects of the most effective antiknock compounds on Dry Vapour Pressure Equivalent (DVPE), distillation temperatures, aromatic content, olefins, and oxygen content. Emphasis was given in studying chemical structures that can be derived from renewable raw materials. The compounds tested included substituted phenols, furan derivatives, aliphatic amines, various amide structures and Mannich base phenols. Methyl t-butyl ether (MTBE), the most widespread oxygenate currently used in gasoline, was used as a yardstick for assessing the quality of the compounds tested.

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.

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 Diesel engine and especially the direct injection type one is considered to be one of the most efficient thermal engines known to man up to now. It has an efficiency that in some cases is 30 to 40% higher than its competitor the spark ignition engine. The efficiency of the direct injection diesel engine has been considerably improved during the last decade resulting to low fuel consumption and lower absolute values of pollutant emissions. If we consider the green house effect caused by the emitted CO2 it is revealed the environmental importance of high engine efficiency. In the present work a theoretical investigation is conducted using a detailed simulation model for engine performance prediction, to examine the possibilities for improving engine efficiency. The simulation model used is a complete open cycle model for the engine and its subsystems. Such phenomenological models are very suitable for the prediction of engine performance.

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.

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.

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%.

During the past years most fundamental research worldwide has been concentrated on the direct injection diesel engine (DI). This engine has a lower specific fuel consumption when compared to the indirect injection diesel engine (IDI) used up to now in most passenger cars. But the application of the direct injection engine on passenger cars and light trucks has various problems. These are associated mainly with its ability to operate at high engine speeds due to the very low time available for combustion. To overcome these problems engineers have introduced various techniques such as swirl and squish for the working fluid and the use of extremely high pressure fuel injection systems to promote the air-fuel mixing mechanism. The last requires the solution of various problems associated with the use of the high pressure and relatively small injector holes.

During the last years a great deal of effort has been made for the reduction of pollutant emissions from direct injection Diesel Engines. Towards these efforts engineers have proposed various solutions, one of which is the use of gaseous fuels as a supplement for liquid diesel fuel. These engines are referred to as dual combustion engines i.e. they use conventional diesel fuel and gaseous fuel as well. The ignition of the gaseous fuel is accomplished through the liquid fuel, which is auto-ignited in the same way as in common diesel engines. One of the fuels used is natural gas, which has a relatively high auto-ignition temperature. This is extremely important since the CR of most conventional diesel engines can be maintained. In these engines the released energy is produced partially from the combustion of natural gas and from the combustion of liquid diesel fuel.

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 need of a more realistic and dynamic driving cycle which simulates real-world driving conditions in the largest city in the greater area of Balkans, led to the development of the Athens Driving Cycle (ADC). Emission and fuel consumption measurements were conducted over the ADC and compared with those of the New European Driving Cycle (NEDC) using a chassis dynamometer. A Euro II compliant diesel vehicle was used in this study, fuelled with a typical automotive diesel fuel and biodiesel blends at proportions of 5, 10, and 20 % respectively. The unregulated emissions were characterized by determining the soluble organic fraction (SOF) in the particulate matter, together with qualitative hydrocarbon analysis present in the SOF fraction, and of carbonyl compounds (aldehydes, ketones). Emissions of NOx, CO, THC, CO2, and PM10 were also measured over the two test cycles.

During recent years, the deterioration of greenhouse phenomenon, in conjunction with the continuous increase of worldwide fleet of vehicles and crude oil prices, raised heightened concerns over both the improvement of vehicle mileage and the reduction of pollutant emissions. Diesel engines have the highest fuel economy and thus, highest CO2 reduction potential among all other thermal propulsion engines due to their superior thermal efficiency. However, particulate matter (PM) and nitrogen oxides (NOx) emissions from diesel engines are comparatively higher than those emitted from modern gasoline engines. Therefore, reduction of diesel emitted pollutants and especially, PM and NOx without increase of specific fuel consumption or let alone improvement of diesel fuel economy is a difficult problem, which requires immediate and drastic actions to be taken.

The introduction to the European market of higher levels of biodiesel blends focuses the research interest on the compatibility problems of the diesel fuel distribution system. The influence of metals in the oxidation stability and lubricity of two different types of commercially available FAMEs (without antioxidant additive) was investigated. Zinc (Zn), Copper (Cu) and Tin (Sn), were added in the form of solid metals (heterogeneous catalysis in liquid phase oxidation) and examined for their impact on the oxidation stability of biodiesel fuel. Oxidation stability was determined by Rancimat accelerated oxidation method, according to European Standard EN14214. Additionally, in order to examine the effect of the above mentioned metals in the presence of antioxidant additive, BHT was added in both biodiesel samples and oxidation stability determinations were carried out, as well.

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.

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.

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 describes the effect of different types of biodiesel (fatty acid methyl esters, FAME) on the oxidative stability of low and ultra low sulfur automotive diesel fuels. Eight different samples of FAME were employed to create blends of 2, 3, 4, 5, 7, and 10% v/v with four different types of diesel fuels. The samples were analyzed using the modified Rancimat method (EN 15751). The aim of this paper was to evaluate the impact of biodiesel source material and biodiesel concentration in diesel fuel, on the oxidation stability of the final blend. Moreover, the effect of sulfur content and the presence of cracked stocks in the base diesel fuel, on the oxidation stability of the final blends were also investigated.

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.