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The effect of using diesel-biodiesel-bioethanol blends on the fuel feed pump of a small-scale internal combustion engine
Full text linkBiofuels represent an environmental-friendly and feasible alternative to fossil fuels for internal combustion engines. The use of diesel-biodiesel-bioethanol fuel blends (ternary blends) is one of the most interesting solutions in terms of fossil fuels substitution. They provide an improvement of exhausts gas emissions without any significant sacrifices in terms of energy-conversion efficiency. However, engine operation may be affected by the fuel substitution especially in the auxiliary mechanical fuel-feed systems, traditionally designed for low-density and high-viscosity fossil fuels. In the proposed work, two easy-to-use experimental-based mathematical models have been obtained by using the response surface method to assess the behaviour of fuel feed-pumps when biofuels blends are used. Density and mass flow-rates have been measured for several fuel mixtures and at different temperatures. The proposed equations are intended to be used as a practical tool, based on the optimal behaviour of the fuel feed-pump, in order to choose the best ternary fuel-mixture composition and/or predict/infer the engine performances under non-tested conditions (i.e., other mixtures' compositions and temperatures, however within the inquired domain)
Proposal of a predictive mixed experimental-numerical approach for assessing the performance of farm tractor engines fuelled with diesel-biodiesel-bioethanol blends
Full text linkThe effect of biofuel blends on the engine performance and emissions of agricultural machines can be extremely complex to predict even if the properties and the effects of the pure substances in the blends can be sourced from the literature. Indeed, on the one hand, internal combustion engines (ICEs) have a high intrinsic operational complexity; on the other hand, biofuels show antithetic effects on engine performance and present positive or negative interactions that are difficult to determine a priori. This study applies the Response Surface Methodology (RSM), a numerical method typically applied in other disciplines (e.g., industrial engineering) and for other purposes (e.g., set-up of production machines), to analyse a large set of experimental data regarding the mechanical and environmental performances of an ICE used to power a farm tractor. The aim is twofold: i) to demonstrate the effectiveness of RSM in quantitatively assessing the effects of biofuels on a complex system like an ICE; ii) to supply easy-to-use correlations for the users to predict the effect of biofuel blends on performance and emissions of tractor engines. The methodology showed good prediction capabilities and yielded interesting outcomes. The effects of biofuel blends and physical fuel parameters were adopted to study the engine performance. Among all possible parameters depending on the fuel mixture, the viscosity of a fuel blend demonstrated a high statistical significance on some system responses directly related to the engine mechanical performances. This parameter can constitute an interesting indirect estimator of the mechanical performances of an engine fuelled with such blend, while it showed poor accuracy in predicting the emissions of the ICE (NOx, CO concentration and opacity of the exhaust gases) due to a higher influence of the chemical composition of the fuel blend on these parameters; rather, the blend composition showed a much higher accuracy in the assessment of the mechanical performance of the ICE
Analysis of Cryoscopic Behaviour of Diesel-Biodiesel Blends Using Industrial Freezer
No full textAs opposed to gasoline, diesel oil has a lower limit temperature for its use in internal combustion engines (ICEs), which ranges between -7 oC and -20 oC for the summer/winter formulation: it is therefore close to the average winter temperature typical of some European countries. In approaching such temperature, the formation of paraffins alters the physical characteristics of diesel oil (viscosity in particular) and makes it impossible to be used in ICEs. The same, aggravated problem is presented also by biodiesel and diesel-biodiesel blends, which are very interesting given their benefits in terms of performance and pollutant reduction in conventional compression-ignition engines (e.g., agricultural and operating machinery, cogeneration systems).
Some varieties of biodiesel, such as biodiesel from palm oil, solidify at 13 oC, whilst others, more suitable for winter temperatures, solidify at -10 oC (biodiesel from canola seeds), which is nevertheless a higher temperature than that of diesel oil. In this work, a simple industrial freezer set at -21 oC was used to assess the freezing temperatures of many solutions of multiple components with different freezing points (diesel-biodiesel blends). The illustrated procedure use slow-cost and simple equipment thus allowing to reproduce similar experiments in industrial environments. The elaborations carried out have included the use of polynomial functions to fit the data and the identification of temperature tangency traits. Although the results are not in the form of the usual significant temperatures indicated by standards as cold-flow properties for fuels (i.e., pour point, cloud point, cold filter plugging point), they are substantially aligned with the literature data. However, the outcomes in the
form of upper and lower liquid-to-solid temperatures are very interesting and useful to give the experimenters/users practical indications about the opportunity of using diesel-biodiesel blends with different compositions
The kinematic viscosity of conventional and bio-based fuel blends as a key parameter to indirectly estimate the performance of compression-ignition engines for agricultural purposes
No full textThe partial replacement of conventional fuels with “bio-based” fuels represents a viable energy strategy for cleaner distributed-power generation (agricultural/co-generative units). Although internal combustion engines represent a well-established technology, they will continue to play a crucial role in this energy revolution thanks to their flexibility of use and reliability. Considering compression-ignition engines, the fuel change is simple and requires no modification. Yet some critical issues related to different fuel viscosity may arise. The aim of this study is, therefore, to investigate with a mixed experimental–numerical approach: (a) the kinematic viscosity of many fuel blends (diesel oil-biodiesel-bioethanol) at the standard temperatures of 40 °C and 100 °C, and (b) the effects of the fuel viscosity on engine performance. The data and the mathematical model obtained through the Response Surface Methodology allowed observing that: (a) the fuel-feed system should include a preheater to obtain the same fuel viscosity in blends as in pump diesel oil and avoid issues in the fuel feed; (b) the viscosity at 40 °C progressively increases by 38% (from 3.03 to 4.18 mm2 s−1) as the biodiesel percentage in the blend spans from 0 to 100%; (c) bioethanol fluidizes the blends, reducing the viscosity by about 2% per percentage point of bioethanol in the blend. Also, some trials on a farm tractor fuelled with some of these blends allowed to identify that ternary blends with a viscosity > 3.33 mm2 s−1, whatever the composition within the validity ranges of models (0 ≤ biodiesel ≤ 100, 0 ≤ bioethanol ≤ 3), give rise to the maximum torque increment
The Kinematic Viscosity of Conventional and Bio-Based Fuel Blends as a Key Parameter to Indirectly Estimate the Performance of Compression-Ignition Engines for Agricultural and Cogeneration Purposes
No full textThe partial replacement of conventional fuels with “bio-based” fuels represents a viable energy strategy in the medium-short term for cleaner distributed-power generation (agricultural and co-generative units). Although the internal combustion engine is a traditional and well-established technology, it will continue to play a crucial role in this energy revolution thanks to its flexibility of use and reliability. Considering compression-ignition engines, the fuel change is particularly simple to carry out and requires no particular modification. Yet some critical issues related to the variation of the fuel viscosity may arise. For these reasons, the kinematic viscosity of many fuel blends (diesel oil-biodiesel-bioethanol) was inquired at the two typical temperatures of 40 °C and 100 °C, referred by standards. On the basis of the collected data and of the mathematical model obtained through the Response Surface Methodology, it was possible to observe that: (a) in order to have a blend with the same viscosity of diesel oil at 40 °C (3.03 mm2 s-1), the fuel-feed system should work at higher temperatures (about +28 °C) and hence a preheater is required to ensure that the fuel pump operates at its nominal flowrate; (b) the viscosity at 40 °C progressively increases by 38% (from 3.03 to 4.18 mm2 s-1) as the biodiesel percentage in the blend spans from 0 to 100%; (c) bioethanol fluidizes the blends, reducing the viscosity by about 2% for each percentage point of bioethanol in the blend. Also, a set of trials on a farm tractor fuelled with some of these blends allowed: (a) to obtain another numerical model using the fuel viscosity as statistically-significant estimation parameter, (b) to observe that it is possible to have a torque increment of about 49.3 Nm per each an increment of 1 mm2 s-1 of the blend viscosity (regardless of whether the cause is the viscosity itself or other properties that change concomitantly with it). These results have been used to propose an alternative fuelling for the farm tractor, having observed that the best increase of the torque can be obtained when the used ternary fuel blend has a viscosity greater than 3.33 mm2 s-1, whatever the composition within the validity ranges of the models (0 ≤ biodiesel ≤ 100, 0 ≤ bioethanol ≤3)
Use of diesel-biodiesel-bioethanol blends in farm tractors: first results obtained with a mixed experimental-numerical approach
Full text linkThe fuelling of internal combustion engines with biofuels has certainly many environmental and energetic advantages. These advantages are particularly effective in the agricultural sector, where an integrated biofuel supply-chain would further benefit the overall carbon balance. Unfortunately, there are also some drawbacks, mainly concerning the engine performances (lowering of the torque curve), but also environmental (possible raising of the NOx emissions). However, by appropriately mixing two biofuels with known opposite effects on the combustion process, it is theoretically possible to compensate the aforementioned disadvantages. In this work, some experiments were carried out in this direction by fuelling a farm tractor with four different fuel mixes; the collected data were processed through the Response Surface Methodology to obtain multi-parameter regression equations useful to identify the optimal fuel mixtures composition. Thanks to this approach, it was found that biodiesel has a positive effect on the torque, while the addition of bioethanol has a much bigger detrimental effect; on the contrary, bioethanol should be added to a mixture with a minimum of 8-12 % of biodiesel to get advantages in terms of NOx concentration reduction
PROPOSAL OF A MIXED EXPERIMENTAL-NUMERICAL APPROACH TO EVALUATE THE EFFECTS OF DIESEL-BIODIESEL-BIOETHANOL BLENDS FOR FUELLING FARM TRACTORS
No full textBiofuels have always been of a certain interest in the technical-motor field, due to the beneficial effects they can produce when used to fuel internal combustion engines. Liquid biofuels such as biodiesel and bioethanol are being studied in particular applied to Diesel engines, widely used in heavy-duty applications and, therefore, also in agriculture. In this last field, moreover, the interest is even greater, thanks to the possibility to create interesting supply-chain economies and reduce the energy demands of the sector by proposing a partial self-sufficiency.
However, the effects of the many biofuels on the performance and environmental impact of a machine can be different and, sometimes, even antithetical. Hence, the maximisation of biofuels properties requires necessarily the search for a trade-off in their use, e.g. by mixing them in appropriate percentages. A chemical-analytical approach to this problem, even if theoretically possible, could be extremely simplifying at the modelling level and too little generalizable due to the extreme variety of technical solutions (EGR, SCR) adopted in engines and regulations of them. For this reason, the approach to these topic has always been purely-experimental, even if the interpretation of the resulting effects is often difficult and, generally, little predictive. Therefore, we decided to apply the Response Surface Methodology, usually adopted in other areas characterized by very complex phenomena (i.e., in industrial engineering), to process the data collected during some tests at the dyno on a New Holland T4020V tractor. Through this technique we have obtained multi-parameter regression equations that can be useful to describe the tractor outputs (performance curves, pollutants) and identify the optimal fuel-blends composition. Finally, through the same technique, we have found that bioethanol should be added only to blends having a minimum of 8-12% of biodiesel to give advantages in terms of NOx concentration reduction
Biolubricant ageing analysis: Proposal for a real-engine test and chemical characterization
No full textBiolubricants are the most promising renewable alternative in the lubrication industry. Given the environmental benefits, a comprehensive understanding of the actual performance of biolubricants is essential for their conscious use, particularly in internal combustion engines. In this study, a commercial ester-based biolubricant (PLANTO MOT SAE 10W40) was tested to assess its degradation behavior during engine operation. This study aims at evaluating the accelerated ageing behavior of a biolubricant after on/off test cycles on an internal combustion engine under real operating conditions. It was observed that the density of the biolubricant increased steadily after 120 cycles, while its kinematic viscosity steadily dropped over time at both 40 °C and 100 °C, which is consistent with normal ageing of lubricants. TBN was stable during ageing but with a minor decrease at 120 cycles, which is a sign of reduced acid neutralization effectiveness, despite the slow increase in oxidation levels confirming that the lubricant resisted oxidation well over the testing period. Analyzing wear metals, additives, and pollution over time offers essential information on how the biolubricant degrades in challenging conditions. Emission analysis for the same engine using the biolubricant showed a noticeable decrease in CO emissions by 16.6 % compared to the same engine using a conventional lubricant, a slight drop in CO2 emissions by 12.9 %, a significant reduction in NOx emissions by 12.0 %. The biolubricant contributed to the reduction of UHCs by 2.5 %. The potential of biolubricants to minimize incomplete combustion byproducts, lower greenhouse gas and polluting emissions is reflected in these findings
Experimental Investigation and RSM Modeling of the Effects of Injection Timing on the Performance and NOx Emissions of a Micro-Cogeneration Unit Fueled with Biodiesel Blends
Full text linkThe (partial or total) substitution of petro-diesel with biodiesel in internal combustion engines (ICEs) could represent a crucial path towards the decarbonization of the energy sector. However, critical aspects are related to the controversial issue of the possible increase in Nitrogen Oxides (NOx) emissions. In such a framework, the proposed study aims at investigating the effects of biodiesel share and injection timing on the performance and NOx emissions of a diesel micro combined heat and power (CHP) system. An experimental campaign has been conducted considering the following operating conditions: (i) a reference standard injection timing (17.2° BTDC), an early injection timing (20.8° BTDC), and a late injection timing (12.2° BTDC); (ii) low (0.90 kW), partial (2.45 kW), and full (3.90 kW) output power load; and (iii) four fuel blends with different biodiesel (B) shares (B0, B15, B30, and B100). Experimental data were also elaborated on thanks to the response surface modelling (RSM) technique, aiming at (i) quantifying the influences of the above-listed variables and their trends on the responses, and (ii) obtaining a set of predictive numerical models that represent the basis for model-based design and optimization procedures. The results show: (i) an overall improvement of the engine performance due to the biodiesel presence in the fuel blend —in particular, B30 and B100 blends have shown peak values in both electrical (29%) and thermal efficiency (42%); (ii) the effective benefits of late SOI strategies on NOx emissions, quantified in an overall average NOx reduction of 27% for the early-to-late injection, and of 16% for the standard-to-late injection strategy. Moreover, it has emerged that the NOx-reduction capabilities of the late injection strategy decrease with higher biodiesel substitution rates; through the discussion of high-prediction-capable, parametric, data-driven models, an extensive RSM analysis has shown how the biodiesel share promotes an increase of NOx whenever it overcomes a calculated threshold that is proportional to the engine load (from about 66.5% to 85.7% of the biodiesel share)
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