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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.

During the last years a great effort has been made by many NATO nations to move towards the use of one military fuel for all the land-based military aircraft, vehicles and equipment employed on the military arena. This idea is known to as the Single Fuel Concept (SFC). The fuel selected for the idea of SFC is the JP-8 (F-34) military aviation fuel which is based upon the civil jet fuel F-35 (Jet A-1) with the inclusion of military additives possessing anti-icing and lubricating properties. An extended experimental investigation has been conducted in the laboratory of Thermodynamic and Propulsion Systems at the Hellenic Air Force Academy. This investigation was conducted with the collaboration of the respective laboratories of National Technical University of Athens and Hellenic Naval Academy as well.

A transient analysis simulation program is developed for studying the response of an indirect injection, naturally aspirated, diesel engine after a rapid increase in load when this is equipped with various types of indirect acting governors. Analytical expressions are presented for the better simulation of engine mechanical friction, inertia moments and heat loss to the walls under transient conditions, governor dynamics for both the sensing element and the servopiston, soot emissions and the fuel pump operation. Various types of governor sensing elements (i.e. mechanical, electrical, two-pulse) and feedbacks (i.e. unity and vanishing) for the servomechanism are studied. Explicit diagrams are given to show how each combination of governor type and technical parameters (i.e. mass and number of flyweights, geometrical dimensions, amplification factors) affects the speed response as well as the speed droop and the recovery period of the particular engine.

In the past years various models have been proposed for the modelling of performance and pollutants emissions from DI diesel engines. These models range from complicated 3D detailed ones up to simple two zone phenomenological ones. The latter ones although simple offer solutions in engine study and are widely used due to their low computational cost and simplicity. In the present work a multi-zone model for direct injection diesel engines is presented together with its application on a direct injection diesel engine located at the authors laboratory. Multi-zone models usually fail to predict adequately both pollutants emissions and performance and thus focus mainly on pollutants emissions. Of course this is not acceptable since the formation of pollutants is strongly related to the combustion mechanism. In the present work an effort has been made to overcome this problem and predict both performance and emissions throughout the engine operating range.

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.

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.

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.

A great deal of research is taking place at the present time in the field of diesel engines, especially regarding the emission of gaseous pollutants and soot. This research is essential for engine manufacturers since it is difficult for diesel engines to meet current standards regarding soot and nitric oxide emissions. The problem will become even more severe when the new legislation will be applicable requiring a 50% reduction of existing levels. Many manufacturers and researchers feel that engines will be difficult to meet this criterion without the use of other techniques such as gas aftertreatment or newly developed fuels (low sulfur content, etc.). The aim of this research is to examine the effect of fuel composition and physical properties on the mechanism of combustion and pollutants formation.

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.

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.

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.

Neural networks (NN) for marine engines, using raw measurement data from laboratory measurements, are developed and verified. These models can be utilized as virtual sensors of engine-out NOx emissions and lambda (λ). Investigations for the optimal NN configuration targeting models were carried so they can capture the dynamic behavior of a marine diesel engine, can generalize within the training range, and have the minimum complexity due to execution performance and portability reasons. Two configurations of NNs are investigated, the recurrent (RNN) and the time-delay neural network (TDNN). The resulting NN models are deployed on a prototype engine control unit (ECU) platform and are validated in real time for operating points and patterns that are not included in the training dataset. The real-time validation shows that the predicted quantities remain consistent in most operating areas and the dynamic behavior of the system is captured and reproduced accurately.

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.

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.

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.