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Home All issues Volume 79 (2024) Sci. Tech. Energ. Transition, 79 (2024) 33 Full HTML
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Issue
Sci. Tech. Energ. Transition
Volume 79, 2024
Article Number 33
Number of page(s) 11
DOI https://doi.org/10.2516/stet/2024033
Published online 11 June 2024

© The Author(s), published by EDP Sciences, 2024

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1 Introduction

Biodiesel, which is derived from biomass and has lower emissions compared to petroleum diesel [1], has been recognized as a promising alternative fuel for compression-ignition engines [2, 3]. It is renewable and can be produced with lower environmental impact [4]. However, the properties of biodiesel can vary widely depending on the type of feedstock and production process used, which can lead to certain challenges when used as a sole fuel in diesel engines [5, 6]. One challenge associated with using biodiesel as a sole fuel is its potential impact on engine power output [7]. This reduction in power can be attributed to the lower calorific value of biodiesel [8, 9] which affects the combustion process and can result in lower engine performance [10]. Another challenge is that biodiesel has a higher oxygen content compared to petroleum diesel, which can lead to increased carbon deposits on injectors and combustion chambers [7]. Higher cylinder pressure is also a potential issue when using biodiesel as a sole fuel [7]. To address these challenges, biodiesel is often blended with petroleum diesel [11, 12], or used as an additive to mitigate the potential drawbacks associated with its use as a sole fuel [12, 13]. Blending biodiesel with diesel can help improve its energy content and combustion characteristics, and minimize the impact on engine power output, deposits, and cylinder pressure [14, 15].

Studies have shown that the addition of ethanol to biodiesel can increase its ignition delay and reduce its viscosity, leading to an increase in engine power output and a reduction in engine deposits [16]. Furthermore, the high volatility of ethanol can enhance the air/fuel mixing process and improve the combustion efficiency, resulting in lower cylinder pressure and reduced emissions [17].

The use of ethanol, characterized by a low viscosity and density, results in better atomization and more complete combustion with an improvement in engine performance [18]. As well as the high amount of oxygen, about 34% by weight, helps to reduce emissions. [19]. Additionally, the existence of the hydroxyl (OH) group and the elevated oxygen levels in alcohol-blended fuel contribute to the enhanced oxidation of soot during the controlled mixing and late combustion phases [20]. However, blending biodiesel with alcohol has its own drawbacks. Many research studies have noted that the main issues associated with adding alcohols to biodiesel are their poor miscibility and their instability in the mixture, which depend on many factors such as their blending ratio, the temperature and the time before the separation of the phases, etc. [21, 22].

The use of ethanol in diesel engines as a blending fuel has several disadvantages. Thus, its low cetane number and calorific value influence the characteristics of the mixture [23, 24].

Several studies have been performed on the blending effects of ethanol on diesel/biodiesel engine performance and emissions:

Wei et al. [25] conducted an experimental investigation on a naturally-aspirated, 4-cylinder direct-injection diesel engine fueled with different blends (5%, 10% and 15%) of ethanol- and butanol-biodiesel. The authors observed a rise in SFC for the various alcohol–biodiesel blends compared to pure diesel, which increased by increasing the percentage of alcohol in biodiesel; this is due to the lower calorific values of ethanol and butanol. A small drop in BTE, at low loads, was observed in the case of ethanol–biodiesel blends, explained by its low combustion temperature and high latent heat of evaporation, which make the cooling effect more significant. At medium and high loads, the cooling effect of alcohol disappears due to the increase in combustion temperature created by the increase in load. Both types of alcohol–biodiesel blends led to an increase in CO emissions. This was explained firstly by the fact that the higher latent heat of evaporation of the alcohol reduced the temperature of gases in the cylinder and secondly by the low viscosity provide a lean air-fuel mixture. A significant reduction in NOx was recorded by adding 10% and 15% of ethanol but an increase by adding butanol was noted compared to pure diesel.

Wai et al. [8] carried out an experimental work on a 3-liters, four-cylinder diesel engine fueled with various ethanol–biodiesel blends. Two percentages, 5% and 10% of ethanol were mixed with three percentages, 10%, 20% and 100% of biodiesel to obtain B10E5, B10E10, B20E5, B20E10, B100E5 and B100E10 blends. They noticed an increase in BSFC with an increasing proportion of ethanol and biodiesel, explained by their lower calorific values than pure diesel. The oxygen richness of the different mixtures leads to an improvement in the thermal efficiency of the engine. A decrease in the emission of smoke while an increase in NOx was observed by adding more ethanol to biodiesel, due to higher combustion temperatures and greater oxygen contents.

Shrivastava et al. [26] have used a tri-mixture of Karanja biodiesel–ethanol–diesel in a CI engine. The maximum BTE was given by a mixture containing 20% of biodiesel and 10% of ethanol, under full load conditions, but it was less by 2% than pure diesel. Similar SFC values have been recorded at 75% load. A reduction in CO and NOx emissions, while an increase in CO2 emission, was observed for the ethanol–biodiesel blends compared to baseline diesel.

Vergel-Ortega et al. [27] studied the performance and emissions of a single-cylinder diesel engine fueled with alternative fuels constituted by commercial diesel and biodiesels derived from residues of palm oil (3%) and sunflower oil (2%) mixed with ethanol (2% and 4%). The performance of four different fuels, including three biodiesel blends and pure diesel, was tested on a single-cylinder diesel engine under nine different operation modes. The research showed that pure diesel had the lowest SFC and the highest BTE. The biodiesel blend with 4% ethanol gave an increase of 5% in SFC and a decrease of 2.5% in BTE when compared to pure diesel. Moreover, the addition of ethanol resulted in an improvement in BTE when compared to the biodiesel-based fuel, which presented the lowest value. Pure diesel had the highest value of CO and CO2 emissions, with a decrease being observed for biodiesel blends as ethanol percentage increases. The presence of ethanol leads to a more complete combustion, which results in a decrease in CO emissions. Additionally, due to the lower amount of carbon and C/H ratio in ethanol, a reduction in CO2 emission was observed. NOx emissions increased with the addition of biodiesel compared to pure diesel. However, this was compensated by the addition of ethanol, resulting in a significant reduction of NOx in the exhaust gases as the percentage of ethanol increased.

Yerrennagoudaru and Manjunatha [28] conducted an experimental investigation on a twin-cylinder diesel engine using various biofuel–ethanol blends: 70% canola oil biodiesel mixed with 30% ethanol, 50% soyabean oil biodiesel with 50% ethanol and 50% palm oil blended with 50% ethanol. These blends were compared to pure diesel fuel. This study showed that these mixtures can be good alternative fuels, giving performance, such as SFC and BTE, close to that given by pure diesel and reducing emissions such as HC, CO2 and NOx.

Considering the scientific literature, biodiesel environmental benefits in terms of fuel consumption and emissions depend heavily on its proprieties which are directly related to its production process. Microwave-assisted transesterification has emerged as a promising technique for high-quality biodiesel production [29]. As a chemical process for biodiesel production, this technique has been recently largely studied, with substantial investigations dedicated to the impacts of binary blends with petrodiesel on engine performance and emissions. However, research on ternary blends such as biodiesel, alcohol, and petrodiesel is scarce.

Therefore, the current study aims to contribute to a deeper comprehension of the combined effects of microwave-produced biodiesel and ethanol, blended with petrodiesel, on a single-cylinder CI engine performance and emissions under various operating conditions and without altering the engine design or the fuel injection characteristics. The biodiesel was obtained by transesterification of sunflower oil, using ethanol and NaOH as a catalyst, in a microwave-heated reactor [30]. The effect of adding small amounts of ethanol to biodiesel–diesel blends on various engine performance parameters and emissions was assessed. The parameters that were analysed include engine brake power (BP), brake mean effective pressure (BMEP), brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), as well as emissions of carbon monoxide (CO), carbon dioxide (CO2), and nitrogen oxides (NOx). These parameters are evaluated under different load and engine speed conditions to comprehensively understand the impact of ethanol addition on the engine performance and emissions compared to pure diesel and biodiesel–diesel blends. The analysis and discussion of the results provide insights into the impact of ethanol addition on the overall engine performance, fuel consumption, thermal efficiency, and emissions, and contribute to the understanding of the potential benefits and drawbacks of using ethanol–biodiesel–diesel blends as an alternative fuel in compression ignition engines.

2 Experimental setup and methodology

The main objective of this research work is to study, experimentally, the mechanical and thermochemical characteristics of CI engines fueled with different fuel blends: diesel–biodiesel and diesel–biodiesel–ethanol mixtures. The obtained results are compared with those of pure diesel fuel.

The test bench, presented in Figure 1, is composed of a LOMBARDINI type, single-cylinder, air-cooled, diesel engine, an electrical dynamometer for torque measurement, an electric charge rheostat for loading the engine, and a Testo 350 gas analyzer for exhaust gas emissions measurement.

thumbnail Fig. 1

Experimental setup.

The engine loading operation was fixed at 2500 W by the electrical charge rheostat, which represents half of the maximum load supported by the engine according to the technical specifications. The mechanical engine torque was directly measured using a scale on the outer casing of the dynamometer. The engine speed was obtained by an optical tachometer type VT-8204. Measurements were conducted in the speed range of 800–3200 rpm. Each measurement was repeated three times to enhance the result’s robustness and minimize the measurement errors. The average values were then calculated.

The characteristics of the tested engine are presented in Table 1. The gas analyzer specifications are detailed in Table 2.

Table 1

Engine characteristics.

Table 2

Gaz analyzer specifications.

The biodiesel used in this study was produced by a microwave-assisted transesterification process of sunflower oil carried out in the presence of ethanol and NaOH as a catalyst [30].

Traditionally, the process of transforming vegetable oils like sunflower oil into biodiesel faced a major hurdle due to the sluggish mixing of oil and alcohol, the essential reactants. This challenge led to the need for high temperatures, and catalyst usage, ultimately increasing energy consumption and production costs. However, microwave heating technology has emerged as one of the promising solutions for cost-effective biodiesel production thanks to its reduced reaction time and catalysts and to the high reaction yields [31].

As described in previous work [32], the biodiesel production system, depicted in Figure 2, consists of a modified microwave oven equipped with a stirrer, reagent supply inputs and a thermocouple to control the reaction temperature.

thumbnail Fig. 2

Biodiesel production using microwave-assisted technique.

The biodiesel production process is illustrated in Figure 3. This chemical process was optimized to obtain a more than 98% reaction yield in less than 1 min under an alcohol-to-oil molar ratio of 6:1, a 2% by mass of NaOH catalyst and a reaction temperature of 70 °C [30].

thumbnail Fig. 3

Biodiesel production process.

Four fuel mixtures were tested: pure diesel fuel, 90% diesel blended with 10% of biodiesel, a mixture of 87.5% of pure diesel fuel with 10% of biodiesel and 2.5% of ethanol and a mixture of 85% of pure diesel fuel with 10% of biodiesel and 5% of ethanol, labelled B0, B10, B10E2.5, and B10E5, respectively.

The main properties of ethanol, BD and pure diesel fuel are presented in Table 3.

Table 3

Main properties of tested fuels [30, 33–35].

3 Uncertainties analysis

To evaluate the reliability of the measurements an uncertainty analysis was performed using the standard deviation method [36] based on the specifications provided by the device’s user manuals (Table 4).

Table 4

Uncertainties of measurement instruments.

4 Results and discussion

The effects of the various fuel blends (B0, B10, B10E2.5 and B10E5) on engine operation and emissions characteristics were studied under 1/2 load. This study seeks to analyze the obtained results of BP, BMEP, SFC and BTE, followed by a discussion on the emissions of CO, CO2 and NOx.

4.1 Engine performance

4.1.1 Brake power (BP)

The evolutions of the brake power and its percentile variations compared to B0, the function of the engine speed for the different fuels, under 1/2 load, are presented in Figure 4.

thumbnail Fig. 4

Evolutions of BP and their relative changes with reference to B0, function of engine speed.

Adding 10% of BD increased slightly the engine power compared to B0. This effect was more noticeable at high speeds (>2000 rpm), reaching 6%. This increase in BP became progressively greater with the addition of ethanol and reached 16% at 1700 rpm for B10E2.5 and 13% at 2500 rpm for B10E5. A similar result was found by Bhurat et al. [37] for an engine powered by a mixture of ethanol–biodiesel–diesel, under various loads.

This behaviour can be attributed to the high cetane number of biodiesel and the high oxygen content in both biodiesel and ethanol, despite their low LHVs compared to B0 [38].

4.1.2 Brake mean effective pressure (BMEP)

The effects of the various fuel blends on BMEP are shown in Figure 5. All the blends exhibit an increase in BMEP, compared to B0, at all speeds range. The maximum enhancement was obtained by B10 showing an increase of an average value of 13%.

thumbnail Fig. 5

Variations of BMEP and their relative changes with reference to B0, function of engine speed.

The increase in BMEP, compared to B0, when adding BD is mainly due to the high cetane number and oxygen content of BD. The addition of ethanol to the BD–diesel mixture decreased slightly BMEP, which can be attributed mainly to the low cetane number and LHV of ethanol compared to BD. In addition, ethanol has a high heat of vaporization and high autoignition temperature, requiring more time to vaporize under low load conditions and low temperatures, as explained by Karin et al. [39]. Similar results were also reported by Freitas et al. [40], attributing this slight decrease to the low cetane number of ethanol compared to biodiesel. They also stated that this decrease would not be perceived in transport applications.

4.1.3 Brake specific fuel consumption (BSFC)

The variation of the specific fuel consumption is shown in Figure 6. It is clear that, at low and medium speeds, the substitution of diesel fuel for biodiesel and then the addition of ethanol, reduced the specific fuel consumption of the engine, with a small advantage for biodiesel compared to ethanol. However, at high speeds (>2300 rpm), the addition of biodiesel and then ethanol, increased the engine SFC compared to pure diesel fuel.

thumbnail Fig. 6

Evolutions of SFC and their relative changes with reference to B0, function of engine speed.

Adding oxygenated fuels such as BD and ethanol, makes the blends leaner which improves the mixture volatility and homogeneity. Consequently, the combustion is more efficient, reducing fuel consumption, especially at low and medium engine speeds. However, at high speeds, the decrease in the volumetric efficiency and the low LHV of the biodiesel and ethanol results in more fuel consumption [41].

Similar behaviour was reported by Kukana and Jakhar [42] and was explained by the fact that the addition of alcohol improves combustion efficiency, resulting in a decrease in SFC. Comparable results were also found by Pidol et al. [43].

4.1.4 Brake Thermal efficiency (BTE)

The brake thermal efficiency (BTE) is an indicator of how well the chemical energy contained in the fuel is converted into mechanical work at the engine crankshaft. Figure 7 presents the variations of BTE, given by the fuel blends, and the function of the engine speed. As expected, the BTE behaviour is the inverse of that of SFC since they are inversely proportional. Adding biodiesel and ethanol enhanced BTE at low and medium speeds. However, at high engine speeds, BTE is reduced. This result is explained in the same way as for SFC.

thumbnail Fig. 7

Evolutions of BTE and their relative changes with reference to B0, function of engine speed.

Jayapal and Radhakrishnan [44] attributed the decrease in BTE of biodiesel, at high rpm, to its low calorific value and poor atomization characteristics due to higher viscosity, leading to less complete combustion.

The maximum values of BTE, obtained at a speed range of 1900–2100 rpm, gave an improvement, over pure diesel fuel, by 7.6%, 6.7%, and 2.5%, for B10, B10E2.5 and B10E5, respectively. It is evident that adding ethanol to the biodiesel–diesel blend has a slight negative impact on BTE which can be mainly attributed to the low cetane number and LHV of ethanol [45].

4.2 Exhaust gas emissions

4.2.1 Carbon monoxide (CO)

The variations of carbon monoxide emissions function of the engine speed are presented in Figure 8.

thumbnail Fig. 8

Variations of CO emissions and their relative changes with reference to B0, function of engine speed.

It is evident that blending pure diesel fuel with 10% biodiesel resulted in a significant rise in CO emissions, reaching an average of 190% at all speeds range. Nonetheless, the addition to this blend of 2.5% ethanol helped in mitigating this increase, especially at low and medium speeds with an average decrease of 32% compared to B0. However, increasing the amount of ethanol in the blend up to 5% has a limited impact on decreasing CO emissions of the biodiesel–diesel blend, especially at medium and high speeds.

The same behavior was reported by Hulwan and Joshi [46], under low loads. They explained the drastic increase in CO emissions by the drop in the cylinder gas temperature and the delayed combustion process which weakened the oxidation process despite the high oxygen amount available.

In contrast to this, other studies have reported a decrease in CO emissions by the addition of alcohol [47, 48]. However, this impact depends closely on the amount and the type of alcohol used [49].

4.2.2 Carbon dioxide (CO2)

Figure 9 presents the emissions levels of CO2, for the different fuel blends, and the function of the engine speed. It is very important to discuss CO2 emissions produced by ICEs since it contributes significantly to climate change.

thumbnail Fig. 9

Variations of CO2 emissions and their relative changes with reference to B0, function of engine speed.

This study showed that adding biodiesel reduces CO2 emissions compared to pure diesel fuel. Thanks to the oxygen content in biodiesel, a more stable and complete combustion is obtained [50]. Furthermore, adding ethanol was more beneficial for reducing CO2 emissions. Increasing the ethanol blending ratio reduced CO2 emissions at all speed range. This effect was more obvious at low engine speeds. For example, at 1000 rpm, the CO2 drop reached 50% and 55%, compared to B0, for 2.5% and 5% of ethanol added to B10, respectively. As it was explained previously for CO, the presence of ethanol in the mixture brings more oxygen which improves the combustion quality and thus reduces CO2 emission levels. Similar results were found by Vergel-Ortega et al. [48]. They stated that this effect is due to the lower amount of carbon and low C/H ratio of ethanol.

4.2.3 Nitrogen oxide (NOx)

It is crucial to understand the impact of the blends on NOx emissions, as even small changes in their emission levels can have significant consequences.

In a diesel engine, the fuel mixture contains a high amount of air, which primarily consists of oxygen and nitrogen. At low temperatures, nitrogen does not interact significantly, but as the temperature increases, it reacts with oxygen and undergoes oxidation, resulting in the formation of nitrogen oxide. This phenomenon is more relevant at higher temperatures and can contribute to air pollution [51].

Figure 10 presents the variations, at various engine speeds, of NOx emissions, for tested fuels, and its relative change for B10, B10E2.5 and B10E5, compared to B0.

thumbnail Fig. 10

Variations of NOx emissions and their relative changes with reference to B0, function of engine speed.

The addition of biodiesel and ethanol has a positive effect on the decrease of NOx emissions. This effect is more significant at low and medium speeds than at high speeds. The maximum reduction was given by B10E5 with a value near 90%, at 1000 rpm.

Although adding 2.5% ethanol to B10 gave better results than B0, it was not entirely beneficial compared to B10. However, by adding more ethanol (5%) to B10, NOx emissions decreased significantly, and better results were obtained even compared with B10.

This can be explained by the fact that adding a small amount of ethanol to the BD blend, provides more oxygen in the mixture to react with nitrogen, hence, more NOx is produced. However, due to its high latent heat of vaporization, adding more ethanol prolongs the fuel vaporization and mixing duration, resulting in lower combustion temperatures and then less NOx is produced.

Similar results were obtained by Jamrozik et al. [52]. They explained these opposite effects of ethanol on NOx emissions by the competition between two factor groups. On one hand, the low cetane number and the significant amount of oxygen in the ethanol blends cause high peak heat release, which increases the in-cylinder temperature and hence NOx emissions. On the other hand, a high value of heat of evaporation of ethanol and low flame temperature tend to reduce the in-cylinder temperature, resulting in NOx emissions decrease.

Ma et al. [49] stated that the NOx emissions drop in BD–ethanol blends is mainly due to the cooling effect of ethanol associated with its lower calorific value and higher latent heat of evaporation reducing the combustion temperature and consequently NOx emissions.

5 Conclusions

The main goal of the present research was to study, experimentally, the performances and emissions characteristics of a single-cylinder CI engine fueled by diesel–biodiesel and diesel–biodiesel–ethanol blends. The effect of adding small quantities of ethanol (2.5% and 5%) to 10% of biodiesel blend (B10), on the engine power, mean effective pressure (BMEP), specific fuel consumption (SFC), thermal efficiency (BTE), and on CO, CO2 and NOx emissions was investigated under half load conditions and at engine speeds ranging from 1000 to 2500 rpm. The most important results are summarized as follows:

  • BD increased slightly the engine power compared to pure diesel fuel. This effect was more noticeable with the addition of ethanol especially at high speeds. This result was attributed to the high cetane number of biodiesel and then the high oxygen content in both biodiesel and ethanol.

  • All the blends exhibit an increase in BMEP compared to pure diesel fuel, at all speeds range. The maximum enhancement was obtained by BD thanks to its high cetane number and oxygen content. The addition of ethanol to the BD–diesel mixture decreased slightly BMEP, which can be attributed mainly to the low cetane number and LHV of ethanol compared to BD.

  • The engine SFC was reduced by the addition of BD and ethanol, especially at low and medium speeds, thanks to their high oxygen contents which improves the mixture volatility and homogeneity and consequently the combustion efficiency. However, at high engine speeds, an increase in SFC was recorded compared to pure diesel fuel, due to the decrease in the volumetric efficiency and the low LHV of BD and ethanol.

  • The engine BTE behaviour was the inverse of that of SFC since they are inversely proportional. Adding BD and ethanol enhanced BTE at low and medium speeds. However, at high engine speeds, it was reduced. This is due to the same reasons as for SFC.

  • Blending pure diesel fuel with 10% of BD resulted in a significant rise in CO emissions at all speed range. Nonetheless, the addition of 2.5% ethanol helped in mitigating this increase, especially at low and medium speeds. Increasing the amount of ethanol in the blend up to 5% had a limited impact on decreasing CO emissions. This result was explained by the drop in the cylinder gas temperature and the delayed combustion process which weakened the oxidation process despite the high oxygen contents of BD and ethanol.

  • Adding BD reduced CO2 emissions, compared to pure diesel fuel, thanks to its high oxygen content. Furthermore, adding ethanol was more beneficial for reducing CO2 emissions due to the lower amount of carbon and low C/H ratio of ethanol.

  • NOx emissions were positively affected by the addition of BD and ethanol compared to pure diesel fuel. In addition, it was noticed that adding 2.5% ethanol increased NOx emissions compared to B10. However, better results were obtained by adding more ethanol (5%) to B10. This can be explained by the fact that the presence of a small amount of ethanol provided more oxygen in the mixture to react with nitrogen, hence, more NOx was produced. However, due to its high latent heat of vaporization, adding more ethanol prolongs the fuel vaporization and mixing duration, resulting in lower combustion temperatures and then less NOx was produced with 5% ethanol.

Finally, due to their similar physical and chemical properties to those of petroleum fuel, biodiesels have the potential to serve as a viable alternative in CI engines, particularly when derived from renewable and sustainable sources. Adding alcohol could reduce the drawbacks of biodiesels, such as low engine power and efficiency. Nevertheless, this positive effect depends closely on the alcohol type and blending ratio.

Acknowledgments

The authors did not receive support from any organization for the submitted work.

Funding

The authors have no financial or proprietary interests in any material discussed in this article.

Conflicts of interest

The authors declare that there is no conflict of interest.

Author contribution statement

All authors contributed to the study’s conception and design. Material preparation, data collection and analysis were performed by Fakher Hamdi, Ilhem Yahya and Mehrez Gassoumi. The first draft of the manuscript was written by Fakher Hamdi, Zouhair Boutar and Mansour Al Qubeissi, then reviewed and edited by Raja Mazuir Raja Ahsan Shah, Ridha Ennetta and Hakan Serhad Soyhan. The current research work was conducted under the supervision of Ridha Ennetta and Hakan Serhad Soyhan. All authors read and approved the final manuscript.

References

All Tables

Table 1

Engine characteristics.

In the text
Table 2

Gaz analyzer specifications.

In the text
Table 3

Main properties of tested fuels [30, 33–35].

In the text
Table 4

Uncertainties of measurement instruments.

In the text

All Figures

thumbnail Fig. 1

Experimental setup.
In the text
thumbnail Fig. 2

Biodiesel production using microwave-assisted technique.
In the text
thumbnail Fig. 3

Biodiesel production process.
In the text
thumbnail Fig. 4

Evolutions of BP and their relative changes with reference to B0, function of engine speed.
In the text
thumbnail Fig. 5

Variations of BMEP and their relative changes with reference to B0, function of engine speed.
In the text
thumbnail Fig. 6

Evolutions of SFC and their relative changes with reference to B0, function of engine speed.
In the text
thumbnail Fig. 7

Evolutions of BTE and their relative changes with reference to B0, function of engine speed.
In the text
thumbnail Fig. 8

Variations of CO emissions and their relative changes with reference to B0, function of engine speed.
In the text
thumbnail Fig. 9

Variations of CO2 emissions and their relative changes with reference to B0, function of engine speed.
In the text
thumbnail Fig. 10

Variations of NOx emissions and their relative changes with reference to B0, function of engine speed.
In the text

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