Evaluation of Auto-Ignition Characteristics of Diesel Surrogate Fuels with the Same Derived Cetane Numbers at Changed Thermodynamic Environments

The ignition tendency of diesel fuels is highly sensitive to ambient conditions and fuel properties.In this study,the ignition characteristics of different diesel surrogate fuels with the same derived cetane numbers(DCN)were measured and compared in varied thermodynamic and oxidizing environments.The combustion pressures,heat release rates,ignition delays,and combustion delays of the test fuels were compared.The experimental results showed that the diesel surrogate fuels with the same DCNs exhibit similar ignition propensity at standard DCN test conditions.Further,for the test conditions of high cetane fuels,high ambient temperatures,and suficient oxygen concentrations,surrogate fuels with the same DCN have similar ignition behaviors,and using the DCN to evaluate fuel ignition tendency is appropriate.However,for the test conditions of low cetane fuels,low ambient temperatures,and reduced oxygen concentrations,different ignition behaviors are observed for the surrogate fuels with the same DCN,so at these conditions using DCN as the evaluation index for fuel ignition tendency may lead to higher uncertainty.

Descriptors-based machine-learning prediction of cetane number using quantitative structure–property relationship

The physicochemical properties of liquid alternative fuels are important but difficult to measure/predict, especially when complex surrogate fuels are concerned. In the present work, machine learning is used to develop quantitative structure–property relationship models. The fuel chemical structure is represented by molecular descriptors, allowing the linking of important features of the fuel composition and key properties of fuel utilization. Feature selection is employed to select the most relevant features that describe the chemical structure of the fuel and several machine learning algorithms are tested to construct interpretable models. The effectiveness of the methodology is demonstrated through the development of accurate and interpretable predictive models for cetane numbers, with a focus on understanding the link between molecular structure and fuel properties. In this context, matrix-based descriptors and descriptors related to the number of atoms in the molecule are directly linked with the cetane number of hydrocarbons. Furthermore, the results showed that molecular connectivity indices play a role in the cetane number for aromatic molecules. Also, the methodology is extended to predict the cetane number of ester and ether molecules, leveraging the design of alternative fuels towards fully sustainable fuel utilization.

Variations of cetane number of jatropha biodiesel blends with mineral diesel

Cetane number(CN)-a prime indicator of diesel fuel quality,is a quantity indicating the combustion behaviour of diesel fuel and compression required for ignition in diesel engines.This study examines the determination of CN of Jatropha biodiesel blends with mineral diesel using their physical properties,and their variations of CN with percentage composition of Jatropha biodiesel in the blends.Jatropha biodiesel,converted through a transesterification process of its oil,is obtained and blended with diesel to obtain blend B10(10%biodiesel and 90%diesel)on a volumetric basis,at 25℃ ambient temperature and the same basis was employed for blends B20,B30,B40 and B50.The specific gravity and mid-distillation characteristic were obtained using a hydrometer and distillation curve apparatus based on ASTM D1298 and D86 standards respectively.The CN of Jatropha oil,its biodiesel and Jatropha biodiesel blends with diesel were analytically determined,employing the empirical relationship between measured physical properties of a two-variable cetane index equation.The results show that the CN of the Jatropha biodiesel increases significantly(about 29%)after transesterification compared with that of the Jatropha oil.Moreover,the specific gravity and CN of the blends increase with the percentage composition of Jatropha biodiesel in the blends.The CN of Jatropha biodiesel is 44.10,which is 8.7%higher than that of mineral diesel(40.62).It can be implied from the research outcomes that blending Jatropha biodiesel with diesel increases the CN of the blends,thus,could be used as cetane point(number)enhancer.

Diesel and Jet Fuels from Bitumen-derived Middle Distillates

Narrow fractions of light gas oils obtained from various upgrading processes of Athabasca oilsands bitumen were investigated as diesel and jet fuels. The relationship among the boiling range, cetane number, smoke point, and other properties such as aromatics content, aniline point, and the sulfur and nitrogen content was also studied. The study reveals that when appropriate processes and distillation boiling ranges are selected, oilsands bitumen can produce diesel and jet fuels that meet stringent environmental regulations and future product specifications. New correlations to predict CN and smoke point were developed as a function of density, boiling ranges by simulated distillation, and mono- and total aromatics by supercritical fluid chromatography. The correlations apply to bitumen-derived middle distillates that have a wide range of boiling points.

Medium-Pressure Hydro-upgrading (MHUG) Technology for Producing Clean Diesel Fuel

Abstract： This article introduces the development and application of the medium-pressure hydro-upgrading （MHUG） tech- nology developed by the Research Institute of Petroleum Processing （RIPP）. The MHUG technology based on the chemistry of diesel hydro-upgrading reactions has the advantages of flexible product slate and excellent product quality that can in- crease the cetane rating of diesel fuel up to more than 15 units. The hydrotreating and hydro-upgrading catalysts associated with the MHUG technology have outstanding performance to meet the demand of MHUG technology for hydro-saturation and selective ring-opening of aromatic rings. New MHUG process flow scheme can further increase the yield and selectivity of target products. Commercial application of multiple MHUG units has revealed that the MHUG technology designated for clean diesel production features good feedstock adaptability and operating stability.

The DDA-II Process for Manufacture of Diesel Fuel Meeting the Euro-IV or even Higher Emission Standard

The DDA-Ⅱ process aimed at manufacture of diesel fuel meeting the Euro-Ⅳ emission standard from inferior diesel feedstock has been developed and tested in pilot scale. This technology adopts non-noble metal catalysts and a highly integrated two-stage process scheme featuring low investment and operating cost and convenience in operation. Under an appropriate process regime the DDA-Ⅱ technology can process FCC LCO, a blend of straight-run diesel and FCC LCO, or the SR diesel to yield the diesel product streams meeting the Euro-Ⅳ or even higher emission standards.

Theoretical Analysis of Ignition in Diesel Engines

The present work investigates the influence of ignition delay on the diesel engine performance. A theoretical model is used via a program written by MATLAB, to compute the ignition delay in (ms) for a diesel engine at identical operation conditions. The ignition delay in the diesel engines using different reference diesel fuels with different cetane numbers of 40 and 50 was investigated. Effect of the operating conditions such as the engine compression ratios, intake pressures and temperatures on the ignition delay, was investigated. Influences of engine speed changes on ignition delay at low, moderate and high conditions were represented. Comparisons between obtained results for the two types of the used fuels were also represented. The results show that the ignition delay decreases with increasing the engine speed, the engine compression ratio, cetane number, intake pressure and temperature. The compression ratio causes remarkable reduction in ignition delay.

Investigation of extracted Sclerocarya birrea seed oil as a bioenergy resource for compression ignition engines

Sclerocarya birrea(Marula)seed oil was extracted and characterized for its physico-chemical properties and fatty acid compositions,respectively,by using standardized laboratory methods of the Association of Official and Analytical Chemist(AOAC).The fuel and lubrication properties of marula oil were also determined by using the ASTM methods,and the oil was evaluated in terms of its antiwear,viscometrics,volatility,stability,environmental compatibility properties and energy content.It was found that the high percentage of mono-unsaturated oleic acid(73.6%)provided the oiliness that makes marula oil a natural alternative to genetically modify high oleic acid sunflower oil used in biodiesel production.The aggregate properties of seed oiliness as exemplified by the high oleic acid content,high saponification value(178.6 mg/KOH)and viscosity(41 mm2/s)makes marula oil to be prospective based oil for engine crank case biolubricants with antiwear and friction reduction properties.However,the higher oil viscosity exhibited by marula seed oil in comparison to diesel could pose some durability problems to compression ignition engines,when used directly as fuel.Nonetheless,the reduction of oil viscosity would be required by heating,blending with diesel fuel,or by transesterification to forestall the risk of engine failure resulting from the use of unmodified marula oil.The flash point of marula oil(235℃)is somewhat close to that of monograde SAE 40 mineral oil(240℃),and appreciably higher than that of diesel fuel(52℃).The high flash point makes the seed oil less flammable and ensures safer handling and transportation.While,the low pour point(-13.7℃)ensures the oil usability for engines at cold start and under low load conditions.The oxidation stability of marula oil is ascribed to the traces of natural antioxidants presented in the oil and improves the oil’s shelf life,notwithstanding the high peroxide value(4.58 mequiv/kg),and linolenic acid content(0.3%),which ought to have been the culprit for lipolytic hydrolysis and rancidity.Furthermore,marula seed oil is more biodegradable and environmentally friendly than oils derived from petroleum crude.The closely related cetane number(47.8)and heating values(38.2 mJ/kg)of marula oil to diesel fuel would undeniably sustain the combustion efficiency of diesel fuel and also supply a comparable engine performance output in compression ignition engines.The candidacy of marula seed oil,as a bioenergy resource for alternative fuel,fuel additives and lubricants,will no doubt expand the energy supply mix,conserve fossil fuel reserves and mitigate environmental contamination.