Impact of Ethanol–Diesel Blend on CI Engine Performance and Emissions

Abstract

The aim of this study was to assess the impact of adding ethanol to diesel fuel on particulate matter (PM) and nitrogen oxides (NOx) emissions in the Perkins 854E compression-ignition engine. Tests were carried out under European Stationary Cycle (ESC) conditions using the Horiba Mexa 1230 PM analyzer (HORIBA, Ltd., Kyoto, Japan) for particulate measurement and the AVL CEB II analyzer (AVL, Graz, Austria) for NO_x concentration. The engine under investigation featured direct injection, turbocharging, a common-rail fuel supply system, and complied with the Stage IIIB/Tier 4 emission standard. Two types of fuel were used: conventional diesel fuel (DF) and diesel with a 10% ethanol additive by volume (DFE10). In addition to emissions measurements, key engine performance parameters, such as torque, effective power, and fuel consumption, were analyzed. The ESC test was specifically chosen to isolate the influence of the fuel’s properties by avoiding the effects of changes in combustion control strategies. Due to the lower calorific value of DFE10 compared to DF, a slight increase in fuel consumption was observed under certain operating conditions. Nevertheless, overall engine performance remained largely unchanged. The test results showed that the use of DFE10 led to a significant 44% reduction in particulate matter emissions and a moderate 2.2% decrease in NO_x emissions compared to conventional diesel fuel. These findings highlight the potential of ethanol as a diesel fuel additive to reduce harmful exhaust emissions without negatively affecting the performance of modern diesel engines.

1. Introduction

The sought-after solutions for powering compression-ignition engines with liquid fuels focus on several key areas that aim to improve efficiency, reduce harmful emissions, and adapt to changing environmental and regulatory requirements [1,2,3]. One such approach includes fueling a diesel engine with an ethanol additive. Ethanol addition is much more commonly used for gasoline than for diesel fuel [4,5,6,7]. This is due to several key differences in the physicochemical properties of ethanol and in the design and operating principles of spark-ignition and compression-ignition engines [8,9,10]. However, it is still an interesting research problem. Such fueling of compression-ignition engines with ethanol additive diesel fuel could be used, for example, in agricultural vehicles or in vehicle fleets where companies emphasize ecology [11,12,13]. Research on the addition of ethanol to diesel fuel is mainly focused on evaluating the effects of such an additive on engine characteristics, exhaust emissions, and fuel efficiency [14,15,16]. Ethanol is relatively easy to produce, has lower carbon emissions than fossil fuels, and can be used as a renewable energy source [17,18,19]. However, depending on the proportion of ethanol in the blend, there may be changes in exhaust emissions, including a reduction in particulate matter and carbon monoxide emissions, but at the same time, there may be an increase in nitrogen oxide (NO_x) emissions [20,21,22]. In the case of ethanol, its addition to diesel fuel can affect the lubricating properties of the fuel, which can lead to increased wear on engine components if appropriate design modifications are not made [23,24,25]. The development of technology for powering compression-ignition engines with liquid fuels is moving in the direction of increasing efficiency, reducing emissions, and using alternative and renewable fuels [26,27,28]. Innovations in biofuels, hybridization, combustion optimization, and emission reduction systems are key. Although research into feeding diesel engines with ethanol blends is ongoing, the current state of knowledge indicates the need for further analysis to optimize such fuels for energy efficiency, emissions, and engine durability [20,26,27,28,29]. The introduction of ethanol into diesel fuel may have environmental benefits but requires consideration of the potential challenges associated with engine operation.

2. Materials and Methods

2.1. Test Stand

Tests on the dynamometer bench at the Institute of Vehicles and Construction Machinery Engineering are advanced tests that allow for the performance of engines to be assessed. The dynamometer is a key tool for analyzing performance, emissions, and fuel consumption under controlled conditions. The purpose of dynamometer testing is to evaluate engine performance, i.e., to measure power, torque, speed, and efficiency of the engine, and to analyze the engine’s performance characteristics under different load conditions. The dynamometer bench also allows for the concentration of toxic exhaust components to be measured and the effect of different fuels on emissions to be assessed. It is also possible to optimize fuel consumption by determining fuel consumption in different engine modes and testing alternative fuels or fuel additives. Empirical tests were conducted using an engine dynamometer, which was set up with a 4-cylinder Perkins 854E compression-ignition engine. The bench was fitted with a SCHENCK dynamometer to measure the engine’s torque, with an accuracy of ±2 Nm. In addition to torque measurement, the tests allowed for the measurement of fuel consumption with an accuracy of 1%, as well as the monitoring of the engine’s crankshaft speed. The test setup and measurement equipment are illustrated in Figure 1.

The technical specifications of the engine are provided in

Table 1. Technical specifications of Perkins 854E engine (Perkins Engines Company Limited, Cambridgeshire, UK) [31].

Mode	Unit	Value/Feature
Cylinder arrangement	-	in-line
Engine displacement	dm3	3.4
Number of cylinders	-	4
Maximum torque	Nm	450
Nominal power	kW	86
Speed at maximum torque	rpm	1400
Nominal power speed	rpm	2200
Compression ratio	-	17
Cylinder diameter	mm	99
Piston stroke	mm	110
Engine type	-	compression-ignition

. Measurements of the toxic components in the exhaust gases were carried out using AVL CEB II (AVL, Graz, Austria) and Horiba Mexa 1230 PM analyzers. (HORIBA, Ltd., Kyoto, Japan)

Table 2. The error associated with the AVL CEB II [30,31].

Species	Range	Analyzer Error
NOx	High: 50–10,000 Low: 30–5000	±2 ppm ±1 ppm

presents the measurement ranges and associated errors for the exhaust gas toxic components as measured by the AVL CEB II analyzer. Determining engine performance parameters and exhaust gas composition, the authors repeated each measurement point five times. Of the results obtained, the two outliers were discarded, and the other three were averaged. The figures presented in the article show just these average values. Once the empirical tests were completed, measurement errors were also taken into account during their analysis, which are described in detail in Section 2 of the article.

For PM, the accuracy of measurements is 1 mg/m³.

Tests on a dynamometer bench at the Institute of Vehicles and Construction Machinery Engineering are a central tool for the evaluation of engine performance and emissions, particularly in the context of using alternative fuels such as ethanol. The results of such tests are necessary for the design of more eco-friendly and efficient drive technologies. There are many positives from making tests on a dynamometer bench. First of all, the dynamometer allows for controlled test conditions, which gives reliable and consistent test results. A laboratory test is cheaper and faster than testing under actual operating conditions.

2.2. Fuel

While the engine was being tested on a dynamometer at the Institute of Vehicles and Construction Machinery Engineering, it was powered by two fuels. First, tests were conducted feeding the engine with diesel fuel (DF), which formed the basis for comparing the results obtained. Then, empirical tests were performed, feeding the engine with diesel fuel with 10% ethanol addition (DFE10).

Table 3. Selected physical properties of DF and of DFE10 [28,32,33].

Properties	Unit	Method	DF	DFE10
Kinematic viscosity (at 40 °C)	${\displaystyle \frac{{\mathrm{m}\mathrm{m}}^2}{\mathrm{s}}}$	ISO 8217	2.9	1.8
Density (at 15 °C)	${\displaystyle \frac{\mathrm{k}\mathrm{g}}{{\mathrm{m}}^3}}$	ISO 12185	835	810
Dynamic viscosity (at 40 °C)	Pa∙s	ISO 3104	$2.5\times {10}^{-3}$	$1.9\times {10}^{-3}$
Pour point	K	ISO 3016	237	226
Flash point	K	ISO 2719	345	339

and

Table 4. Selected chemical properties and energy properties of DF and DFE10 [34,35,36].

Properties	Unit	Method	DF	DFE10
Cetane number	-	ISO 5165	54.6	49.8
Total aromatic	% v/v	EN 12916	23.1	19.8
Lower Heating	${\displaystyle \frac{\mathrm{J}}{\mathrm{k}\mathrm{g}}}$	PN-86/C-04062	$42.6\times {10}^6$	$40.1\times {10}^6$

present the main physical and chemical properties of both fuels. These parameters alone allow us to set the hypothesis that DFE10 can be an alternative to traditional diesel fuel.

The addition of 10% ethanol to diesel fuel affects the physicochemical properties of the fuel, and this in turn has implications for the operation of the compression-ignition engine. The density of a mixture of 10% ethanol and 90% diesel by volume is lower than that of pure diesel (about 5%) [37,38,39]. Diesel has about 15% higher viscosity than ethanol; therefore, the addition of ethanol lowers the viscosity of the mixture, which may affect the lubrication of the injection system. The flash point of DFE10 is lower than that of pure DF diesel, which requires caution during storage and transportation [40,41,42]. The cetane number of DFE10 will be lower than that of pure diesel fuel, which may hinder ignition and require ignition enhancing additives (e.g., cetane agents). The heating value of DFE10 will be lower than that of pure diesel, which may lead to a slight increase in fuel consumption [43,44,45]. DFE10 will require slightly less air for complete combustion than pure diesel. The addition of ethanol improves combustion due to its oxygen content, which can lead to lower particulate matter (PM) and carbon monoxide (CO) emissions [32,46]. Blending diesel fuel with 10% ethanol has both advantages and disadvantages. On the one hand, it improves combustion and reduces emissions of some harmful components; on the other hand, it requires engine and fuel infrastructure modifications due to its lower cetane number, heating value, and potential mixture stability problems.

2.3. ESC Test

Static and dynamic tests used in vehicle homologation procedures are essential for ensuring that vehicles meet specific safety, emissions, fuel efficiency, and other required standards [46,47]. These tests are conducted under both static (stationary vehicle) and dynamic (vehicle in motion) conditions, depending on the type of test being performed. The ESC (European Stationary Cycle) test is an important part of vehicle approval procedures, particularly for evaluating the emissions and fuel efficiency of internal combustion engines [42,48,49]. The ESC test is specifically designed to assess how vehicles—ranging from motorcycles and cars to stationary engines—emit pollutants when operating under idle or other controlled static conditions. It is a key component of the European vehicle or engine approval process, helping to ensure compliance with European emission regulations. The test plays a crucial role in determining whether a vehicle meets the emission standards set by the European Union, such as Euro 4, Euro 5, and Euro 6 standards. The primary purpose of the ESC test is to measure the emissions of pollutants, including nitrogen oxides (NO_x), particulate matter (PM), hydrocarbons (HCs), and carbon monoxide (CO), under static conditions [44,45,50]. Additionally, the test evaluates fuel efficiency by measuring fuel consumption and greenhouse gas emissions during various phases of engine operation under controlled conditions. Ultimately, the ESC test helps to verify whether a vehicle complies with emission standards across different engine operating states. The results of emissions are typically expressed in grams per kilowatt-hour (g/kWh).

Table 5. ESC test modes [30,46,47].

Mode	Weight, %	Engine Speed	Load, %
1	15	Low idle	0
2	8	A	100
3	10	B	50
4	10	B	75
5	5	A	50
6	5	A	75
7	5	A	25
8	9	B	100
9	10	B	25
10	8	C	100
11	5	C	25
12	5	C	75
13	5	C	50

outlines the test modes used in the ESC test.

To calculate speeds A, B, and C, two specific motor speeds need to be determined. First, the motor speed at 70% of maximum power, denoted as n_hi, must be identified. Then, the motor speed at 50% of maximum power, denoted as n_lo, is determined. With these two values, the motor speeds A, B, and C can be calculated [30,46,47]:

$$\begin{gathered} A=n_{lo}+0.25(n_{hi}-n_{lo}) \\ B=n_{lo}+0.50(n_{hi}-n_{lo}) \\ C=n_{lo}+0.75(n_{hi}-n_{lo}) \end{gathered}$$

The ESC test is characterized by high average load factors and elevated exhaust gas temperatures. Figure 2 provides a graphical representation of the procedure for conducting an ESC test on a dynamometer bench at the Warsaw University of Technology.

The ESC (European Stationary Cycle) test is a key test in the vehicle approval process in Europe. It helps determine how vehicles and internal combustion engines affect the environment by testing emissions and fuel efficiency under static conditions. Such tests are important in ensuring that vehicles meet emission and fuel efficiency standards, which has a significant impact on environmental protection and human health.

3. Results

This section presents the torque and effective power curves (Figure 3). The tests depicted in this figure were conducted at the maximum (volumetric) fuel rate and across the full range of crankshaft speeds for the test engine. The following figure (Figure 4) displays the curves for hourly fuel consumption and specific fuel consumption, with the same operating conditions of the internal combustion engine as in the previous tests.

Figure 5, Figure 6, Figure 7, Figure 8 and Figure 9 display the concentrations of nitrogen oxides and particulate matter, along with the emissions of the aforementioned toxic exhaust gas components, as determined in the ESC test for both tested fuels.

4. Discussion

This article discusses the results obtained on a Perkins engine at its factory standard settings. Intentionally, no modifications were made to the engine settings to see if the DFE10 tested could be a potential replacement for conventional diesel fuel used in compression-ignition engines, particularly those with a common-rail power system. In this study, an addition of 10% ethanol to diesel fuel was used due to the fact that such a mixture of the two liquids was stable (did not delaminate) for a minimum of seven days prior to empirical testing. Larger concentrations of ethanol in the mixture with diesel resulted in delamination of the mixture, and stabilizing additives would have to be added to the mixture for it to be commercially used in internal compression ignition combustion engines. Therefore, in the end, only fuel of the type DFE10 was used for testing, i.e., a fuel that proved to be a stable mixture. During the experiment, the focus was on determining the basic parameters of engine operation and the two main toxic components in the exhaust gas, which the authors of the article considered to be the most important from the point of view of the exhaust gas cleaning process in compression-ignition engines. The most important conclusions and reflections from the research and its analysis are presented below:

1.

Speed characteristics at full load:

-

Achieving higher torque (above 1400 rpm) and effective power (across the range) for DFE10 compared to DF (Figure 3). The maximum increase is 5%. It can be seen from the above that the addition of ethanol alters the combustion process, which increases torque, especially at higher engine crankshaft speeds. Despite the lower energy density of ethanol, its addition improves the thermal efficiency of the engine, leading to better utilization of the energy contained in the fuel. Ethanol has a higher boiling and evaporation temperature, which reduces heat loss. As a result, the DFE10 blend allows for a higher effective power output compared to pure diesel under the same engine-operating conditions.

-

Achieving lower specific and hourly fuel consumption (across the speed range) for DFE10, with a maximum reduction of 3% (Figure 4). The lower specific and hourly fuel consumption for the diesel blend with 10% ethanol (DFE10) compared to pure diesel is due to the different combustion process. The addition of ethanol to diesel, despite the lower energy density of such a blend, allows for a more optimal use of the energy contained in the fuel. In addition, ethanol has a higher evaporation coefficient, which affects the combustion process in the engine, reducing energy losses. The DFE10 blend can also reduce heat loss, leading to better temperature distribution in the running engine. As a result, an engine fueled with this blend uses less fuel, resulting in a reduction in overall fuel consumption compared to pure diesel.

2.

Concentrations and emissions:

-

Speed characteristics (Figure 5): The data show that NO_x concentrations are higher with DFE10, with a maximum increase of 15%. However, particulate matter (PM) emissions are significantly lower, showing a reduction of 30% compared to diesel fuel (DF).

-

Load characteristics at 1300 rpm (Figure 6): At this constant engine speed, NO_x concentrations are higher for DFE10 throughout the load range, with a maximum increase of 20%. On the other hand, PM emissions for DFE10 are consistently lower, showing a reduction of up to 30% at higher engine loads.

-

Load characteristics at 1600 rpm (Figure 7): NO_x concentrations are higher for DFE10, especially at high engine loads, with a maximum difference of 14%. However, particulate matter (PM) concentrations for DFE10 are 32% lower over the entire load range tested, especially at low engine loads.

-

Load characteristics at 1900 rpm (Figure 8): At higher loads, NO_x concentrations are approximately 10% lower for DFE10. As the engine load decreases, the emissions of both fuels become more similar, with a maximum difference of only 4%. For DFE10, particulate emissions are significantly lower, showing a reduction of 48% over the entire load range tested, especially at low engine loads.

3.

Specific NO_x emissions determined by the ESC test for the Perkins 854E engine are 2.2% lower with DFE10 compared to DF. Additionally, specific particulate matter (PM) emissions are 44% lower for DFE10 compared to conventional diesel fuel (DF). This suggests that DFE10 offers a significant reduction in PM emissions, with a small reduction in NO_x emissions, which may be beneficial from an environmental perspective.

In view of the above, it can be concluded that the concentrations or NO_x emissions are higher for DFE10 compared to pure diesel (DF) mainly due to the lower cetane number of ethanol. For fuels with a lower cetane number, the auto-ignition delay is longer, resulting in later ignition of the fuel and a less controlled combustion process. This can lead to uneven combustion, with higher temperature peaks in selected phases of the combustion cycle, which can lead to increased emissions of nitrogen oxides (NO_x) and other undesirable pollutants. On the other hand, the addition of ethanol to diesel fuel results in lower PM emissions because combustion occurs at higher temperatures and more cleanly, reducing the amount of unburned particles in the exhaust.

5. Conclusions

The differences observed in the selected and tested combustion indices can primarily be attributed to the physico-chemical properties of the fuels tested. The key factors influencing these differences are the cetane number, fuel density, and calorific value of the fuels, which directly affect the combustion process and engine performance. DFE10 has a lower cetane number compared to conventional diesel (DF). This results in a longer ignition delay time in the compression-ignition engine, which leads to a later start of combustion of the fuel–air mixture. A longer ignition delay can affect the dynamics of the combustion process and thus the exhaust emissions and the efficiency of converting the chemical energy of the fuel into mechanical work. It is worth noting that no modifications were applied to the engine controller during the tests, meaning that the injection timing and other performance parameters of the power unit remained unchanged. This may suggest that potential differences in combustion characteristics are due solely to the properties of the fuel itself, rather than adjustments to the combustion control strategy. In addition, DFE10 exhibits a lower calorific value compared to conventional diesel, which may affect important engine performance parameters, such as maximum power, torque, and fuel consumption. A reduced calorific value means that a larger volume of fuel needs to be burned to obtain the same amount of heat energy. This can lead to slightly increased fuel consumption under certain operating conditions. Nevertheless, analysis of the test results showed that no significant differences in engine performance or combustion were observed when the Perkins unit was fueled with DFE10. The lack of significant deviations suggests that this fuel can be a direct replacement for conventional diesel without the need for costly fuel system modifications or engine control strategies. In conclusion, the study authors indicate that DFE10 has the potential to replace diesel fuel (DF) in standard diesel engines without the need for significant structural or adaptive modifications. A key prerequisite for its successful use remains meeting the quality standards set out in the current diesel fuel regulations. Particularly relevant are the requirements set out in the World Fuel Charter, which relate, among other things, to the sulfur content, oxidative stability and rheological properties of the fuel. Adherence to these standards will ensure optimum engine performance and compliance with current exhaust emission regulations, which is extremely important in the context of increasing environmental requirements and efforts to reduce harmful emissions into the atmosphere.