The viscosity of diesel oil and mixtures with straight vegetable oils: Palm, cabbage palm, cotton, groundnut, copra and sunflower

The feed back experience of using straight vegetable oil (SVO) as a fuel in the existing diesel engines evidences the need for fitting several physical properties, among them the fuel viscosity. An empirical modelling is proposed in order to interpolate viscosity to any kind of diesel oil/SVO blend. This model is fitted on an experimental viscosity database on blends, varying the SVO mass proportion in the blend, the blend temperature between cloud point and 353 K, and including six vegetable oils varying the fatty acids composition. Extrusion rheology was also checked by varying the pressure drop. Measurements show that blends behave Newtonian.     

Straight vegetable oil use in Micro-Gas Turbines: System adaptation and testing

The aim of this research work is to investigate the use of straight vegetable sunflower oil (SFO), a liquid biofuel, in a Micro-Gas Turbine (MGT). Compared to conventional diesel engines, micro-gas turbines represent a very reliable, clean and performing small scale cogeneration technology. Commercial gas turbines have already been tested with unconventional fuels, such as biomass derived fuels; however, research work on using Straight Vegetable Oil (SVO) as fuel in MGTs are really scarce.The chemical and physical characteristics of SVO are different from fossil diesel oil and rather far from the common technical specifications for gas turbine liquid fuels, not only in terms of kinematic viscosity and Lower Heating Value, but also as regards other issues as contaminant levels and composition, fuel cold properties, ignition properties, etc. Therefore, particular attention has to be given to the atomization and evaporation phases, as these are the most critical steps to achieve stable and efficient long term operation.An analysis based on numerical correlations available from literature was initially adopted for the analysis of the atomization process, supported by CFD modeling to qualitatively investigate the flow pattern. Control parameters were revised and set so to produce a sunflower oil spray having evaporation time comparable to diesel, and minor adaptations to the fuel line were designed and installed on the MGT.Tests with blends and straight vegetable oil were carried out to assess the difference between the standard and the modified machine, fed by diesel, in terms of exhaust emissions, power output and performances, that were similar to the standard diesel-fed MGT. Measured exhaust emissions were as expected well below those typical of diesel engines of the same size fed with VO. The experimental campaign confirmed that it is possible to operate a MGT fed with SVO through the adoption of minor modifications and by adjusting control parameters.     

植物油及其衍生物在柴油机上的应用

评述了植物油及其衍生物在柴油机上应用的前景和可行性,讨论了目前纯植物油、生物柴油和它们的混合物在柴油机上使用的最新研究成果。比较了植物油及其衍生物和传统柴油的性质以及柴油机燃用这些燃料时的性能和排放特性。     

Vegetable oils as renewable fuels for power plants based on low and medium speed diesel engines

There is a high potential for plant oils as alternative fuel for low and medium speed diesel engines, making petroleum-derived fuels likely to be replaced in these types of engines. Vegetable oils have important advantages over both heavy fuel oil (HFO) and marine gas oil (MGO), the fuels currently used in diesel power plants by large two stroke low-speed diesel engines and by medium speed diesel engines, respectively. The emission of certain pollutants and greenhouse gases like SO_x, soot and, mainly, CO₂ can be reduced by using vegetable oils in these types of engines. This work discusses the potential of vegetable oils as fuel for power plant diesel engines and the problems that can be derived from their use. Current experiences with medium speed diesel engines together with the analysis carried out in this paper indicate that vegetable oils can substitute HFO and MGO, without almost any engine modification.     

Use of straight vegetable oil mixtures of rape and camelina as on farm fuels in agriculture

Possibilities for using straight vegetable oil (SVO) from Camelina sativa (L.) Crantz (camelina or false flax) and its mixtures with Brassica napus (rape) SVO as fuel in adapted diesel engines are described with chemical parameters, measurements in a test engine and a field test in a tractor. Camelina as a crop is attracting attention in organic farming and is often used in mixed cropping systems with low competition to food production area. Camelina SVO has low oxidation stability. Its polymerization affinity limits the storage time and increase the risk of coking at hot motor components and of thickening processes in the lubricant oil of the engine. In mixtures with rape and camelina SVO, threshold limits for Conradson Carbon Residues and for oxidation resistance were exceeded. The oxidation resistance could be prolonged by the addition of commercial antioxidants. Camelina and rape SVO showed very similar burning characteristics at full-to-medium partial engine loads. Under low partial loads and idle load, the burning function of the various fuels was increasingly delayed, beginning with diesel fuel over pure rape SVO, then a mixture containing 700 dm³ m⁻³ rape SVO, and 300 dm³ m⁻³ camelina SVO, through to pure camelina SVO. The exhaust emissions of NO_x-, CO-, particles and HC of rape SVO, camelina SVO and their described mixture were not significantly different. The typically higher NO_x- and lower HC-emissions of SVO compared to diesel fuel were apparent. The results principally reveal the usability of a cold pressed, non-refined camelina-rape SVO mixture in adapted diesel engines.     

Performance analysis of a mono-cylinder diesel engine using soy straight vegetable oil as fuel with varying temperature and injection angle

Experimental results are presented for a compression ignition engine with one cylinder refrigerated by air, fueled with soy straight vegetable oil (SVO), filtered at 500 nm and blended with diesel at volume percentages of 10, 30, 50, 70 and 100%. Performance tests varying the injection angle and the fuel temperature were conducted. The results show an increase in torque and power compared to pure diesel, especially with the SVO50 and SVO70 mixtures. However, there was an increase in the specific consumption, although engine efficiency was only slightly lower due to the lower heating value of oil. The use of SVO as fuel is feasible, but durability tests must be performed, mainly to discover potential maintenance problems.     

Small-scale production of straight vegetable oil from rapeseed and its use as biofuel in the Spanish territory

Biofuels nowadays are an important topic of study. The most significant point is the availability of bioethanol or biodiesel and their production from different raw materials. It is already known that large-scale production of first-generation biodiesel cannot be seen as an alternative to fossil fuels due to land requirements, competition with food, increase in fertilizer requirements and pressure on tropical forests among others. This fact does not necessarily apply to second-generation biofuels or small-scale niche productions. Straight vegetable oil (SVO) can be used directly in diesel engines with minor modifications. Our proposal is a small-scale SVO production system for self-supply in agricultural machinery. In this paper a model to provide SVO to local farmers in a specific area in Catalonia (Spain) is presented. We also present a discussion about the regulations to be changed in order to make possible the incorporation of SVO as engine fuel in diesel vehicles and a comparative analysis between the emissions of tractors fed with SVO and petrodiesel. Moreover, a quantitative economic analysis of modifying diesel engines and long-term operability costs are shown and a first-run economic analysis comparing the actual crop rotation with the proposed one and some alternatives is studied.     

Comparison of fuel characteristics of green (renewable) diesel with biodiesel obtainable from algal oil and vegetable oil

To fulfill the need of renewable, sustainable, and cleaner form of fuel, scientists are attracted toward biodiesel and hydrotreated vegetable oil or green (renewable) diesel. Biodiesel is generally obtained from vegetable oil by the process of transesterification while green diesel is obtained by hydrogenation. However, chemically both are completely different and thus their physical properties are highly affected. In present work, authors have compared the important properties of Pongamia biodiesel, algal biodiesel and hydrotreated vegetable oil. It is observed that both the biofuels may be blended for use in diesel engines as this will complement their fuel characteristics.     

Impact of straight vegetable oil-diesel blends application on vehicle regulated and non-regulated emissions over legislated and real world driving cycles

Straight vegetable oil (SVO) has been considered as a possible alternative to fossil diesel-engine fuel since the development of diesel engines. In Europe, SVOs achieved a measurable share in biofuels market reaching 4%. This study attempts to identify the impact of untreated SVO application on fuel consumption and emissions, regulated and non-regulated, on a Euro 3 common rail diesel passenger car. Three different vegetable oils (cottonseed, sunflower, and rapeseed) were blended with diesel fuel, on a 10-90% v/v ratio each. Chassis dynamometer measurements were conducted including both regulated and non-regulated pollutants. In the case of rapeseed oil-diesel blend, carbonyl compounds (10 aldehydes and ketones) were investigated. In addition to the legislated procedure (NEDC), the Artemis driving cycles were used for quantifying the fuels’ impact over realistic driving conditions. Results indicate that all blends have limited effects on gaseous pollutants and vehicle performance. Statistically significant increases on CO₂, CO and HC were recorded over NEDC in the order of 3, 39 and 31%. Reductions were observed on PM emissions particularly for the sunflower oil blends, while NOx remained at baseline levels. Comparison with the emission levels measured when using esterified fuels of the same feedstocks suggests that SVO presence does not affect engine exhaust in the same way as biodiesel. The vegetable oil presence in the fuel appeared to suppress the formation of nucleation mode particles. Straight rapeseed oil increased carbonyl compound emissions over all cycles tested and resulted in higher acroleine/acetone presence in the carbonyl compound composition.     

Performance and emissions characteristics of Jatropha oil (preheated and blends) in a direct injection compression ignition engine

The scarce and rapidly depleting conventional petroleum resources have promoted research for alternative fuels for internal combustion engines. Among various possible options, fuels derived from triglycerides (vegetable oils/animal fats) present promising “greener” substitutes for fossil fuels. Vegetable oils, due to their agricultural origin, are able to reduce net CO₂ emissions to the atmosphere along with import substitution of petroleum products. However, several operational and durability problems of using straight vegetable oils in diesel engines reported in the literature, which are because of their higher viscosity and low volatility compared to mineral diesel fuel.In the present research, experiments were designed to study the effect of reducing Jatropha oil’s viscosity by increasing the fuel temperature (using waste heat of the exhaust gases) and thereby eliminating its effect on combustion and emission characteristics of the engine. Experiments were also conducted using various blends of Jatropha oil with mineral diesel to study the effect of reduced blend viscosity on emissions and performance of diesel engine. A single cylinder, four stroke, constant speed, water cooled, direct injection diesel engine typically used in agricultural sector was used for the experiments. The acquired data were analyzed for various parameters such as thermal efficiency, brake specific fuel consumption (BSFC), smoke opacity, CO₂, CO and HC emissions. While operating the engine on Jatropha oil (preheated and blends), performance and emission parameters were found to be very close to mineral diesel for lower blend concentrations. However, for higher blend concentrations, performance and emissions were observed to be marginally inferior.     

Study the influence of pre-heating on atomization of straight vegetable oil through Ohnesorge number and Sauter mean diameter

Vegetable oil has been considered as one of the most promising alternative fuels for compression ignition engine in recent years. However, the atomization of vegetable oil seems to be different than that of diesel fuel because of having different properties. Atomization and vaporization of fuel are greatly influenced by physical properties of fuel and these properties are temperature dependent. Thus, impact of pre-heating on atomization of straight vegetable oil (SVO) needs to be examined. In the fluid mechanics literature, Ohnesorge jet disintegration classification is most commonly accepted to describe the atomization quality of water jet break-up. A water jet having higher Reynolds number in the atomization regime was considered to atomize quickly after discharge from downstream the nozzle as per this classification. This concept of Ohnesorge classification was used in the present work to study the atomization of SVO. The atomization quality of fuel is judged by the droplet diameter of fuel because it plays a vital role in a primary spray break up and formation process. The main objective of this study was to study the influence of pre-heating on atomization quality of non-edible karanj oil (Pongamia Pinnata) through Ohnesorge number and Sauter mean diameter (SMD). The focus was on atomization quality rather than atomization characteristics of fuel. In this study, effort was made to study atomization quality of SVO in a simplest, easiest and cost effective way by measuring only physical properties of fuel and fuel flow rate. The dimensionless Ohnesorge number and correlation given by Elkotb for SMD were used to predict the atomization quality of SVO with rise in temperature. The study showed that SMD of karanj oil decreases with increase in temperature which in turn improves the air-fuel mixing rate and thus atomization. The Ohnesorge classification showed improvement in atomization of karanj oil while moving from regime I to IV with pre-heating. It is concluded that smaller SMD and higher Reynolds number of karanj oil at 90 °C in regime IV leading to better atomization as compared to karanj oil at room temperature.     

The comparison of engine performance and exhaust emission characteristics of sesame oil–diesel fuel mixture with diesel fuel in a direct injection diesel engine

The use of vegetable oils as a fuel in diesel engines causes some problems due to their high viscosity compared with conventional diesel fuel. Various techniques and methods are used to solve the problems resulting from high viscosity. One of these techniques is fuel blending. In this study, a blend of 50% sesame oil and 50% diesel fuel was used as an alternative fuel in a direct injection diesel engine. Engine performance and exhaust emissions were investigated and compared with the ordinary diesel fuel in a diesel engine. The experimental results show that the engine power and torque of the mixture of sesame oil–diesel fuel are close to the values obtained from diesel fuel and the amounts of exhaust emissions are lower than those of diesel fuel. Hence, it is seen that blend of sesame oil and diesel fuel can be used as an alternative fuel successfully in a diesel engine without any modification and also it is an environmental friendly fuel in terms of emission parameters.     

An evaluation of the life cycle cost of rapeseed oil as a straight vegetable oil fuel to replace petroleum diesel in agriculture

The use of straight vegetable oil (SVO) as biofuel has been recognized as a valid substitute of diesel fuel in the agricultural sector under specific circumstances. Its direct use reduces most of the chemical processes involved when converting it into biodiesel, thus lowering harmful emissions. This study presents the economic analysis of a self-supply farming model that uses rapeseed as its fuel base. This model addresses agricultural environmental concerns and can even minimize dependence on the fluctuating costs of diesel fuel. The use of SVO in agriculture can help reduce farmers’ vulnerability to fossil fuel prices. The economic evaluation of the model proposed in this study shows clear economic benefits of introducing rapeseed to the traditional crop rotation of wheat and barley. The key factors analyzed in this model are diesel fuel price, diesel fuel grants and crop aids. The current situation in Spain favors the use of diesel fuel in agriculture rather than rapeseed SVO due to an 8% profit difference. However, results show that changes in key factors slightly affect the profit margin, calculating a difference of only 3.7% for particular factor combinations. Combined environmental-friendly agriculture supporting policies are necessary to cover this slight profit difference to promote this biofuel.     

Assessing combustion and emission performance of direct use of SVO in a diesel engine by oxygen enrichment of intake air method

This work investigated the effect of the oxygen enrichment in the intake air of diesel engines on the combustion and emissions performance using rape seed oil (RSO) as a fuel. The purpose of the paper is to investigate the potential of oxygen enrichment in the intake air method to restrain the deterioration of particulate emissions of the RSO due to its high viscosity so as to explore the possibility of direct use of SVO (straight vegetable oil) in diesel engines, which can reduce CO₂ emissions and save cost. The combustion parameters such as ignition delay, heat release rate, in-cylinder peak temperature and pressure were determined. Engine out particulate and gaseous emissions of the RSO were measured at oxygen concentrations from 21% (by volume) (no enrichment) to 24% (by volume) and compared to diesel results. The enrichment of the intake air with oxygen decreased the ignition delay and premixed combustion duration, and increased the in-cylinder peak pressure and temperature. The particulate, CO and hydrocarbon emissions were significantly reduced while the NOx emissions increased as the oxygen enrichment rate increased. 22% oxygen enrichment rate was suggested to achieve lower than diesel particulate emissions with the lowest NOx penalty. Increased NOx could be controlled by other methods. The results show that the oxygen enrichment in intake air method enabled direct combustion of SVO in diesel engines with reduced particulate, hydrocarbon and CO emissions.     

Experimental investigations of a four-stroke single cylinder direct injection diesel engine operated on dual fuel mode with producer gas as inducted fuel and Honge oil and its methyl ester (HOME) as injected fuels

In order to meet the energy requirements, there has been growing interest in alternative fuels like biodiesels, methyl alcohol, ethyl alcohol, biogas, hydrogen and producer gas to provide a suitable diesel oil substitute for internal combustion engines. Vegetable oils present a very promising alternative to diesel oil since they are renewable and have similar properties. Vegetable oils offer almost the same power output with slightly lower thermal efficiency when used in diesel engine [Srivastava A, Prasad R. Triglycerides-based diesel fuels. Renew Sustain Energy Rev 2000;4:111–33. [1]; Vellguth G. Performance of vegetable oils and their monoesters as fuels for diesel engines. SAE 831358, 1983. [2]; Demirbas A. Biodiesel production from vegetable oils via catalytic and non-catalytic supercritical methanol transesterification methods. Int J Prog Energy Combust Sci 2005;31:466–87. [3]; Jajoo BN, Keoti RS. Evaluation of vegetable oils as supplementary fuels for diesel engines. In: Proceedings of the XV national conference on IC engines and combustion, Anna University Chennai, 1997. [4]; Altin R, Cetinkaya S, Yucesu HS. The potential of using vegetable oil fuels as fuel for diesel engines. Int J Energy Convers Manage 2000;42:529–38, 248. [5]; Gajendra Babu MK, Chandan Kumar Das LM. Experimental investigations on a Karanja oil methyl ester fuelled DI diesel engine. SAE 2006-01-0238, 2006. [6]; Agarwal D, Kumar Agarwal A. Performance and emission characteristics of a Jatropha oil (preheated and blends) in a direct injection compression ignition engine. Int J Appl Therm Eng 2007;27:2314–23. [7]]. Research in this direction with edible oils have yielded encouraging results, but their use as fuel for diesel engine has limited applications due to higher domestic requirement [Scholl Kyle W, Sorenson Spencer C. Combustion Analysis of soyabean oil methyl ester in a direct injection diesel engine. SAE 930934, 1993. [8]; Nwafor OMI. Effect of advanced injection timing on the performance of rapeseed oil in diesel engines. Int J Renew Energy 2000;21:433–44. [9]; Nwafor OMI. The effect of elevated fuel inlet temperature on performance of diesel engine running on neat vegetable oil at constant speed conditions. Renew Energy 2003;28:171–81. [10]]. In view of this, Honge oil (Pongamia Pinnata Linn) being non-edible oil could be regarded as an alternative fuel for CI engine applications. The viscosity of Honge oil is reduced by transesterification process to obtain Honge oil methyl ester (HOME).Gasification is a process in which solid biomass is converted into a mixture of combustible gases, which complete their combustion in an IC engine. Hence, producer gas can act as a promising alternative fuel, especially for diesel engines by substituting considerable amount of diesel fuels. Downdraft moving bed gasifiers coupled with IC engine are a good choice for moderate quantities of available biomass, up to 500 kW of electric power. Hence, bioderived gas and vegetable liquids appear more attractive in view of their friendly environmental nature. Since vegetable oils produce higher smoke emissions, dual fuel operation could be adopted for improving their performance.     

Progress in biodiesel processing

Biodiesel is a notable alternative to the widely used petroleum-derived diesel fuel since it can be generated by domestic natural sources such as soybeans, rapeseeds, coconuts, and even recycled cooking oil, and thus reduces dependence on diminishing petroleum fuel from foreign sources. The injection and atomization characteristics of the vegetable oils are significantly different than those of petroleum-derived diesel fuels, mainly as the result of their high viscosities. Modern diesel engines have fuel-injection system that is sensitive to viscosity change. One way to avoid these problems is to reduce fuel viscosity of vegetable oil in order to improve its performance. The conversion of vegetable oils into biodiesel is an effective way to overcome all the problems associated with the vegetable oils. Dilution, micro-emulsification, pyrolysis, and transesterification are the four techniques applied to solve the problems encountered with the high fuel viscosity. Transesterification is the most common method and leads to monoalkyl esters of vegetable oils and fats, now called biodiesel when used for fuel purposes. The methyl ester produced by transesterification of vegetable oil has a high cetane number, low viscosity and improved heating value compared to those of pure vegetable oil which results in shorter ignition delay and longer combustion duration and hence low particulate emissions.     

Plant oils as fuels for compression ignition engines: A technical review and life-cycle analysis

As an alternative fuel for compression ignition engines, plant oils are in principle renewable and carbon-neutral. However, their use raises technical, economic and environmental issues. A comprehensive and up-to-date technical review of using both edible and non-edible plant oils (either pure or as blends with fossil diesel) in CI engines, based on comparisons with standard diesel fuel, has been carried out. The properties of several plant oils, and the results of engine tests using them, are reviewed based on the literature. Findings regarding engine performance, exhaust emissions and engine durability are collated. The causes of technical problems arising from the use of various oils are discussed, as are the modifications to oil and engine employed to alleviate these problems. The review shows that a number of plant oils can be used satisfactorily in CI engines, without transesterification, by preheating the oil and/or modifying the engine parameters and the maintenance schedule. As regards life-cycle energy and greenhouse gas emission analyses, these reveal considerable advantages of raw plant oils over fossil diesel and biodiesel. Typical results show that the life-cycle output-to-input energy ratio of raw plant oil is around 6 times higher than fossil diesel. Depending on either primary energy or fossil energy requirements, the life-cycle energy ratio of raw plant oil is in the range of 2–6 times higher than corresponding biodiesel. Moreover, raw plant oil has the highest potential of reducing life-cycle GHG emissions as compared to biodiesel and fossil diesel.     

Characterization and effect of using rubber seed oil as fuel in the compression ignition engines

Vegetable oils pose some problems when subjected to prolonged usage in compression ignition engines because of their high viscosity and low volatility. The common problems are poor atomization, carbon deposits, ring sticking, fuel pump failure, etc. Converting the high viscosity vegetable oil into its blends or esters can minimize these problems. The various blends of rubber seed oil and diesel were prepared and its important properties such as viscosity, calorific value, flash point, fire point, etc. were evaluated and compared with that of diesel. The blends were then subjected to engine performance and emission tests and compared with that for diesel. It was found that 50–80% of rubber seed oil blends gave the best performance. Long run tests were conducted using optimized blend and diesel. It was found that blend fueled engine has higher carbon deposits inside combustion chamber than diesel-fueled engine. Utilization of blends requires frequent cleaning of fuel filter, pump and the combustion chamber. Hence, it is recommended that rubber seed oil–diesel blend fuel is more suitable for rural power generation.     

Use of tobacco seed oil methyl ester in a turbocharged indirect injection diesel engine

Vegetable oils and their methyl/ethyl esters are alternative renewable fuels for compression ignition engines. Different kinds of vegetable oils and their methyl/ethyl esters have been tested in diesel engines. However, tobacco seed oil and tobacco seed oil methyl ester have not been tested in diesel engines, yet. Tobacco seed oil is a non-edible vegetable oil and a by-product of tobacco leaves production. To the author's best knowledge, this is the first study on tobacco seed oil methyl ester as a fuel in diesel engines.In this study, potential tobacco seed production throughout the world, the oil extraction process from tobacco seed and the transesterification process for biodiesel production were examined. The produced tobacco seed oil methyl ester was characterized by exposing its major properties. The effects of tobacco seed oil methyl ester addition to diesel No. 2 on the performance and emissions of a four cycle, four cylinder turbocharged indirect injection (IDI) diesel engine were examined at both full and partial loads. Experimental results showed that tobacco seed oil methyl ester can be partially substituted for the diesel fuel at most operating conditions in terms of performance parameters and emissions without any engine modification and preheating of the blends.     

Performance evaluation of a diesel engine fueled with methyl ester of castor seed oil

In this investigation, castor methyl ester (CME) was prepared by transesterification using potassium hydroxide (KOH) as catalyst and was used in four stroke, single cylinder variable compression ratio type diesel engine. Tests were carried out at a rated speed of 1500 rpm at different loads. Straight vegetable oils pose operational and durability problems when subjected to long term usages in diesel engines. These problems are attributed to high viscosity, low volatility and polyunsaturated character of vegetable oils. The process of transesterification is found to be an effective method of reducing vegetable oil viscosity and eliminating operational and durability problems. The important properties of methyl ester of castor seed oil are compared with diesel fuel. The engine performance was analysed with different blends of biodiesel and was compared with mineral diesel. It was concluded that the lower blends of biodiesel increased the break thermal efficiency and reduced the fuel consumption. The exhaust gas temperature increased with increasing biodiesel concentration. The results proved that the use of biodiesel (produced from castor seed oil) in compression ignition engine is a viable alternative to diesel.