Pure Diesel Operation Research Articles

Investigation on NOx control of a CI engine through the collective effect of hydrogen and biodiesel blend at modified compression ratio

The main challenges with using biodiesel in CI engines are higher NOx emissions and reduced brake thermal efficiency. These biodiesel-related issues can be handled by concurrently introducing gaseous fuels along with primary fuel into CI engines. This study examines the effects of hydrogen in a dual fuel mode operation with diesel and Calophyllum inophyllum biodiesel blend (B20) at different compression ratios on the engine's performance, combustion, and emission characteristics. A single-cylinder, 4-stroke, variable compression ratio engine operating at 1500 rpm was used for the research. A standard compression ratio (SCR) of 17.5 and a modified compression ratio (MCR) of 15.5 at a constant hydrogen flow rate of 6 L per minute (lpm) were used with diesel and B 20. The addition of hydrogen with diesel and B20 resulted in higher cylinder pressure and heat release rate when compared to pure diesel and B20 operation. This resulted in a shorter delay period (by an average of 9.4 % and 7.1 %) with lower peak pressure than pure diesel and B20 operation. During the dual fuel mode of H2 with B 20 at a modified compression ratio, the maximum heat release rate was decreased and its occurrence was retarded. NOx, UBHC, and CO emissions of the engine were decreased significantly by an average of 20.8% 43.7, %, and 22 % respectively with 37.7 % increase in smoke opacity. The increase in NOx emission with the use of H2 with diesel was reduced by operating H2 with B20 and at a reduced compression ratio. This lower emission was achieved with a compromise of a marginal decrease in engine brake thermal efficiency.

Numerical Simulation Research on Combustion and Emission Characteristics of Diesel/Ammonia Dual-Fuel Low-Speed Marine Engine

Amid increasingly stringent global environmental regulations, marine engines are undergoing an essential transition from conventional fossil fuels to alternative fuels to meet escalating regulatory requirements. This study evaluates the effects of injection pressure, the timing of ammonia injection, and the pre-injection of ammonia on combustion and emissions, aiming to identify optimal operational parameters for low-speed marine engines. A three-dimensional model of a large-bore, low-speed marine engine in a high-pressure diffusion mode was developed based on computational fluid dynamics (CFD). Simulations were conducted under 25%, 50%, 75% and 100% loads with a high ammonia energy substitution rate of 95%. The results indicate that, compared to traditional pure diesel operation, adjusting the injection pressure and the ammonia injection timing, along with employing appropriate pre-injection strategies, significantly enhances in-cylinder pressure and temperature, improves thermal efficiency, and reduces specific fuel consumption. Additionally, the dual-fuel strategy using diesel and ammonia effectively reduces nitrogen oxide emissions by up to 37.5% and carbon dioxide emissions by 93.7%.

Effect of Ammonia Addition on Combustion and Emission Characteristics of Diesel Engine Under Various Operating Conditions

ABSTRACT Ammonia is a carbon-free alternative fuel and a hydrogen carrier. Ammonia diesel dual fuel (ADDF) combustion mode is one of the promising ways to reduce carbon emissions in CI engines. However, present researches are mainly based on combustion and emissions for naturally aspirated diesel engine under specific operating condition. This paper aims to illustrate the impacts of replacing diesel with ammonia in a turbocharged diesel engine under various operating conditions. Hence, the effects of various ammonia substitution rate (ASR) on combustion and emission characteristics are numerically investigate by using GT-Power software for nine groups of different operating conditions with low, medium and high speeds and loads. Results show maximum 70% of input energy can be provided by ammonia for nine groups of different operating conditions, and the brake mean effective pressure (BMEP) and the indicated thermal efficiency (ITE) increases with the increase of ASR. Secondly, increasing ASR decreases the peak cylinder pressure (PCP) under different operating conditions, but increases the maximum pressure rise rate (MPRR) at certain operating conditions. Among them, under medium-speed and high-load conditions, the MPRR reaches the highest value, about 0.587 MPa/(°CA), but does not exceed 0.6 MPa/(°CA). Thirdly, increasing ASR changes the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Finally, adding ammonia reduces the NOx, CO and HC emissions, and the decrease is 15.2%–43.2%, 76.2%–82.3%, 70%–79.6%, respectively.

Numerical modelling of a heavy-duty diesel-hydrogen dual-fuel engine with late high pressure hydrogen direct injection and diesel pilot

Direct gaseous fuel injection in internal combustion engines is a potential strategy for improving in-cylinder combustion processes and performance while reducing emissions and increasing hydrogen energy share (HES). Through use of numerical modelling, the current study explores combustion in a compression ignition engine utilising a late compression/early power stroke direct gaseous hydrogen injection ignited by a diesel pilot at up to 99% HES. The combustion process of hydrogen in this type of engine is mapped out and compared to that of the same engine using methane direct injection. Four distinct phases of combustion are found which differ from that of pure diesel operation. Interaction of the injected gas jet with the chamber walls is found to have a considerable impact on performance and emission characteristics and is a factor which needs to be explored in greater detail in future studies. Considerable performance increase and carbon-based emission reductions are identified at up to 99% HES at high load but low load performance greatly deteriorated when 95% HES was exceeded due to a much reduced diesel pilot struggling to ignite the main hydrogen injection.

Mitigating carcinogenic smoke opacity in a light-duty diesel engine by utilizing cyclohexanol, polyethylene glycol, and 2-methoxyethanol.

Diesel fuel reformulation is an attractive method to reduce hazardous smoke emissions because it does not require modifications to the existing engine infrastructure. As the concerns about global warming and air pollution are mounting, high-efficiency diesel engines with low smoke emissions have become more attractive. This study demonstrates that three alcohols, viz. cyclohexanol, polyethylene glycol, and 2-methoxyethanol, can be added to fossil diesel up to 3% by vol. to reduce carcinogenic smoke emissions in a one-cylinder, common rail direct injection (CRDI) diesel engine. The experimental investigations revealed that smoke could be reduced by up to 66.2%, 39.6% and 14% using 3% by vol. addition of cyclohexanol, polyethylene glycol, and 2-methoxyethanol to diesel, respectively, when compared to pure diesel operation. 1% addition by vol. of cyclohexanol and 2-methoxyethanol could reduce NOx and smoke emissions under all load conditions. CO emissions are slightly higher for all alcohol at high load conditions. HC emissions for the test fuels are lower than pure diesel operation at low load conditions, increasing at high loads. These emissions, however, can be reduced by using suitable after-treatment devices.

Study of the Effects of Regenerative Braking System on a Hybrid Diagnostic Train

Nowadays, mobility represents a key sector to achieve the goal of carbon neutrality. Indeed, the development of hybrid powertrains is contributing to a reduction in the environmental impact of vehicles. One of the most promising energy-saving solutions is regenerative braking, which enables deceleration while recovering energy, otherwise wasted. Even though much scientific community effort has been addressed to the optimization of this technology in the automotive field, the increase of energy storage systems efficiencies enables the overcoming of the constraints related to the reuse of electric energy in railway vehicles. This solution could be extremely useful for those railway vehicles which operate on non-electrified lines, where traction is usually provided by diesel engines. For this reason, the present work focuses on how regenerative braking technology could be exploited in diesel-powered rail applications. In further detail, a diagnostic train working on real railway lines has been considered as a case study. Given the real duty-cycle of the vehicle, a simulation model has been developed with the aim of evaluating the amount of energy recovered during braking phases and, consequently, the fuel saving and the avoided CO2 emissions. As a result, the analysis shows an improved energy efficiency of propulsion system. Compared with a pure diesel operation, it leads to fuel savings of 20%, a reduction of CO2 emissions of 22.3 kg with 23.25 kWh stored in the battery at the end of the route.

Effects of ammonia on combustion, emissions, and performance of the ammonia/diesel dual-fuel compression ignition engine

Ammonia is currently receiving more interest as a carbon-free alternative fuel for internal combustion engines (ICE). A promising energy carrier, easy to store and transport, being liquid, and non-carbon-based emissions which make ammonia a green fuel to decarbonize ICE and to reduce greenhouse gas (GHG) emissions. This paper aims to illustrate the impacts of replacing diesel fuel with ammonia in an ammonia/diesel dual fuel engine. Hence, the effects of various ammonia diesel ratios on emissions and engine performance were experimentally investigated. In addition, a developed 1D model is used to analyze the combustion characteristics of ammonia and diesel. Results show 84.2% of input energy can be provided by ammonia meanwhile indicated thermal efficiency (ITE) is increased by increasing the diesel substitution. Moreover, increasing the ammonia energy share (AES) changed the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Therefore, combustion duration and combustion phasing decreased by 6.8CAD and 32CAD, respectively. Although ammonia significantly reduced CO2, CO, and particulate matter (PM) emissions, it also increased NOX emissions and unburned ammonia (14800 ppm). Furthermore, diesel must be replaced with more than 35.9% ammonia to decrease GHG emissions, since ammonia combustion produces N2O (90 ppm) that offsets the reduction of CO2.

Experimental study on the effects of injection timing and n-butanol energy ratio on combustion and emissions of n-butanol/diesel DFDI engine

In this paper, a dual-fuel direct injection (DFDI) system was designed by utilizing two common-rail direct-injection systems in a modified single-cylinder engine. Diesel and n-butanol were directly injected to realize the stratifications of fuel-air mixtures and reactivity. The effects of the n-butanol energy ratio (BER) and fuel injection timing on engine combustion and emission characteristics were studied under low and medium load. The combustion phase was retarded, indicated thermal efficiency (ITE) decreased and COV of IMEP increased as increasing BER under each load. Under low load, the n-butanol injection timing was suggested near 125° CA BTDC to increase ITE, by modifying the stratification of the n-butanol at a favorable level. With an advance of diesel injection timing, the combustion phase was advanced at first and then retarded; ITE was also increased firstly and then decreased. Under medium load, the two-stage high temperature heat release event could be observed. Early n-butanol injection condition was preferred to achieve higher ITE and lower COV of IMEP. The early diesel injection operation was suggested under medium load for increased ITE, together with the decreased nitrogen oxide and soot emissions. In general, compared with pure diesel operation, stable and high-efficient combustion could be achieved in n-butanol/diesel DFDI mode, while the ITE could increase 2.8%; NOx and Soot emission decreased 82% and 79%.

Effects of Diesel Hydrocarbon Components on Cetane Number and Engine Combustion and Emission Characteristics

Commercial diesel consists of hundreds of hydrocarbons such as alkanes, cycloalkanes, and aromatics. The components of the fuel’s composition are what determine its physical and ignition properties, and their variations affect engine performance. In this study, n-heptane, n-dodecane, tetralin, and decalin were chosen as typical additives to blend with commercial diesel according to the China VI standard (Heavy Duty Diesel Vehicle Pollutant Emission Limits and Measurement Methods) in 20% and 50% volume fractions, respectively. The physical properties of the fuel blends, such as viscosity, density, cetane number (CN), and distillation range, were measured first. Then, the commercial diesel’s lower heat value was measured, and blended fuels were calculated accordingly. The CN of the blended fuel is tested by an Ignition Quality Tester (IQT), which is known as the derived cetane number (DCN). The results show that adding n-dodecane increases the value of DCN, while tetralin reduces the DCN, and n-heptane and decalin have negative effects. This study uses a type of WP12 diesel engine made by Weichai that meets China’s emission regulation 6. During the tests, the fuel injection strategy was kept as a pure diesel operation without any modifications. Compared with pure diesel operation, the bench test results show the following characteristics: the maximum torque output increased with increased decalin, followed by tetralin and n-dodecane, while n-heptane has a side effect compared to pure diesel operation. The addition of n-dodecane and n-heptane can reduce fuel consumption, while tetralin will increase it, and decalin has no obvious effect on fuel consumption. It was found that n-heptane increases HC and NOx emissions significantly. Furthermore, n-dodecane slightly increases CO, HC and NOx emissions. Decalin increases CO and HC emissions when mixed in a large proportion. In addition, tetralin causes a substantial increase in HC, CO and NOx emissions at medium and high loads.

Effects of Polyoxymethylene Dimethyl Ethers Addition in Diesel on Real Driving Emission and Fuel Consumption Characteristics of a CHINA VI Heavy-Duty Vehicle

Polyoxymethylene dimethyl ethers (PODE), as the most potential oxygenated alternative fuel for diesel engines, is widely investigated. Considering the importance of research on real driving emissions (RDE) and the few studies focus on the emission characteristics of the PODE/diesel blended fuels under real driving conditions, a portable emission measurement system (PEMS) was applied to measure the RDE of a heavy-duty tractor fueled with diesel or PODE/diesel blends. The tests were carried out in accordance with the relevant regulations of the CHINA VI emission standards. The second-by-second data from PEMS and the OBD system were utilized to construct engine transient operating maps. The results indicated that the addition of PODE can still decrease CO and PN emissions significantly under real driving conditions, although the low load conditions are still the areas of high brake specific CO and brake specific PN emissions. The NOx emissions, however, were not reduced as the results of the steady-state experiment of the same model of the engine. Fuel mass consumption raised when PODE was added, while the overall brake thermal efficiency improved, especially for the blending ratio of 30%, up to 40.3%, which is higher than 38.4% of pure diesel operation.

Consequences of suplementing the HHO gas and CNG with EGR on diesel engine characteristics

Water electrolyzed hydroxyl gas (HHO or Brown gas) and compressed natural gas (CNG) are the important and promising alternatives to the pure fossil fuels. The global concern is about GHG emission in the environment and ambient air pollution steered by mass consumption of fossil fuels in automobile industries and power sectors. In this study, the combustion, performance and emission characteristics of HHO gas and CNG mixtures supplied to intake manifold of compression ignition engine using diesel as a pilot fuel are studied. The same investigations are repeated with various exhaust gas re-circulation (EGR) proportions to study the impact of EGR on multi fuel mode (diesel + HHO gas + CNG) in a Diesel engine. The multi fueled engine performance, combustion and emission parameters are presented and compared with graph and analytical discussion. The results indicated that at full load, the NOx emission decreased by 4% (without EGR), 18% (with 10% EGR) and smoke density decreased by 78% with multi fuel mode comparing to the pure diesel operation at constant speed of 1500 rpm. Also more enhanced performance by improving the brake thermal efficiency by 17%, reducing the brake specific energy consumption by 19%, resulted better fuel economy, and power due to better combustion.

Effect of Nitromethane and Jatropha Biodiesel on the Combustion, Performance and Emission Characteristics of Diesel Engine

The experimental work reported has been carried out in two parts; Jatropha biodiesel production and engine test. The engine test has been carried out on a direct injection, single-cylinder, water-cooled stationary diesel engine. Several diesel fuel blends which contain 10% and 20% by volume of JBD and 1% and 3% nitromethane were prepared. The effects of these blends on the combustion, performance, and emission characteristics of diesel engine were studied. The tests were performed under constant speed and varying load conditions without altering injection timing. A maximum increase of 11.73%, 3.2 % and 7.68 % in the brake thermal efficiency, the brake specific fuel consumption and exhaust gas temperature were achieved respectively for 20% Jatropha biodiesel and 3% nitromethane at full engine load. Compared to the pure diesel operation, the peak in-cylinder pressure of blended fuels was lower at the full load conditions. Also, the maximum net heat release rate of blended fuels was lower than that of diesel at all loading conditions. In regards to the engine emissions, the results showed that the blended fuels reduced carbon monoxide at 18.6–28.9% and unburned hydrocarbon of 7.5-24.2%, while increased the emission of nitrogen oxides at 6.9–14.3% and carbon dioxide at 4.3-10.5%.

Comparative study of low NOx and CO2 emission novel biodiesels on direct injection CI Engine

In this experimental study an attempt is made to find out a biodiesel, whose NOx and CO2 emissions are less and encouraging. Vegetable oils namely Babul oil (Acacia Arabica), Tung Oil (Aleurites fordii) and Grape seed oil (vitis vinifera) were transesterified to reduce their viscosity. These biodiesels were studied as fuel in direct injection 3.7 kW, 1500 rpm with electrical resistance loading. Experiments were conducted at constant speed of 1500 rpm at different percentages of full load of the engine. Out of these three, Grape seed oil methyl ester (GSME) has its performance closer to that of diesel fuel followed by Babul Oil Methyl Ester (BOME) and Tung Oil Methyl Ester (TOME). The brake thermal efficiency of GSME is marginally lower than that of Diesel at full load. The CO2 emissions of these biodiesels were 13%, 17% and 29% lower than that of diesel fuel emissions at full load for BOME, GSME and TOME respectively. The NOx emissions of BOME and TOME were lower by 22% and 27% lower than that of diesel fuel. However the smoke emissions are higher than that of pure diesel operation of the engine.

Experimental evaluation of Salvinia molesta oil biodiesel/diesel blends fuel on combustion, performance and emission analysis of diesel engine

In this work, biodiesel produced from an aquatic weed, Salvinia molesta in the blended form was tested as fuel in single cylinder diesel engine. The properties of S. molesta biodiesel and its blends were measured and compared with diesel. A water-cooled single cylinder diesel engine coupled with eddy current dynamometer was used for experimental work. The S. molesta biodiesel blended with diesel as B10, B20 and B30 on volume basis were used as fuel for conducting the combustion, performance and emission analysis of diesel engine and compared with that of pure diesel operation. The combustion parameters showed maximum reduction in peak pressure and HRR as 1.89% and 6.79%, respectively for B20 as compared to diesel. The performance analysis showed a brake thermal efficiency of 29.51% and minimum BSFC of 0.3081 kg/kWh with B20. The emissions showed maximum reduction of CO, CO2, UBHC, NO, smoke as 14%, 3.38% and 20.83%, 12.86%, 10.99%, respectively with B20 as compared to diesel. Thus, B20 can be used as an alternate fuel for diesel engines.

Physical properties of exhaust soot from dimethyl carbonate-diesel blends: Characterizations and impact on soot oxidation behavior

This study presents the physical properties and oxidation reactivity of exhaust soot from a modern direct injection diesel engine fueled with dimethyl carbonate (DMC)-diesel blends and discusses the relationship between physical properties and oxidation reactivity of soot. The soot morphology, size, fractal dimension and nanostructure were analyzed by transmission electron microscopy and Raman scattering spectrometry. The thermogravimetric analysis was carried out to characterize soot oxidation reactivity in the form of apparent activation energy. The results showed that soot aggregates from DMC/diesel blended fuels exhibited fewer and smaller primary particles as well as small-sized clusters than the diesel soot aggregates. Soot primary particles presented shorter fringe length, wider separation distance and greater tortuosity with increasing DMC blending amount, while the degree of graphitization for soot presented an increasing trend. It was also found that soot from DMC/diesel blends, or low loading operation had higher oxidation reactivity than those from pure diesel or heavy loading operation. Among the physical properties, fractal dimension and primary particle size appeared to be insignificant than the nanostructure for governing the soot oxidation reactivity. Further analysis showed the separation distance was more correlated with soot oxidation characteristics than fringe length and tortuosity. These results illustrated that the use of DMC blended diesel fuel affects the physical properties of soot, enhances soot particle oxidation reactivity, which will be significant for improving the regeneration efficiency of after-treatment device.

Experimental Investigation of PPCI Engine fuelled with Ethanol

Emissions are among those crucial factors that create a huge stress on the people related to engine industry. LTC concepts like HCCI and PPCI are proved as potential solutions for reducing NOX emissions. The impact of ethanol premixed fraction on PPCI mode diesel engine has been investigated in this study. Various ethanol flow rates like 0.27, 0.45, 0.54, 0.72 and 0.81 kg/hr are fumigated in conventional single cylinder diesel engine. Ethanol is used due to the fact that it is available naturally as well as manufactured industrially. The combustion, emission and performance characteristics are plotted for each and every load with various premixed fractions and then the results are compared to pure diesel operation. It is clear from the results that the range of stable operation is being confined by ethanol for different premixed fractions. It can be safely said that for all stable operation, the NOX emission is exceptionally less compared to pure diesel, though, the Un burnt Hydrocarbon & Carbon monoxide emissions are comparatively more. NOX and smoke are decreased for all the premixed fractions at full load. At medium load operations, less NOX, smoke opacity, CO and HC is obtained. Also, at low load operations, there is less NOX and smoke opacity up to premixed fraction 0.3, but HC and CO emissions increases on further increase in the premixed fraction.

Investigation of the effects of diesel-fusel oil fuel blends on combustion, engine performance and exhaust emissions in a single cylinder compression ignition engine

Increasing harmful effects of global warming, consumption of energy and depletion of fossil-based fuels have directed the researches on alternative fuels such as ethanol, methanol, natural gas for compression ignition engines. Among these fuels, alcohols are preferred due to their advantages such as oxygen content, renewable fuel and availability by biomass sources. Fusel oil is obtained as a by-product in ethanol production and it has no usage area and no value for the economy of the country. In this study, pure diesel and fusel oil were mixed in certain proportions. The effects of test fuels on combustion, engine performance and exhaust emissions were examined comprehensively at different engine loads and speeds. In the calculation of heat release rate single-zone combustion model and the first thermodynamics were used. At full load operating conditions similar pressure traces were obtained with F5 and F10 compared to diesel. Specific fuel consumptions were calculated as 201.3, 240.1 and 261.9 g/kWh at 2200 rpm with the usage of diesel, F5 and F10 fuels respectively. In addition, it was determined that as the ratio of fusel oil in the blend increased, CO emissions increased according to the pure diesel operation and smoke and NOx emissions decreased.

Study of combustion, performance and emissions of a diesel engine fueled with ternary fuel in blended and fumigation modes

The present study aimed to compare the combustion, performance and emissions of a diesel engine fueled with diesel, biodiesel and ethanol in the blended and fumigation modes. In addition, a combined fumigation and blended mode (F + B) of fueling was introduced to understand its behavior in comparison with the blended and fumigation modes. In the blended mode, the fuel was composed of 80% diesel, 5% biodiesel and 15% ethanol (DBE), by volume. In the fumigation mode, a mixture of biodiesel and ethanol (BE) was injected into the intake manifold and diesel fuel was used as the main fuel. In the F + B mode, half of the BE mixture was injected into the intake manifold and another half of the DB mixture was mixed with diesel to form the main fuel. The experiments were conducted at a speed of 1800 rpm with five engine loads at a constant mixture percentage of D80B5E15 for the three fueling modes to provide the same fuel composition for comparing the effects of the three fueling modes.According to the average of five loads, compared to the pure diesel operation, the blended mode causes increases in peak heat release rate (HRR), ignition delay (ID), BSFC, CO, HC and NO2; drops in duration of combustion (DOC), CO2, NOX, PM, total number concentration (TNC) and geometric mean diameter (GMD); and similar peak in-cylinder pressure and BTE. While the fumigation mode leads to higher peak HRR, DOC, BSFC, CO, HC, NO2 and TNC; lower ID, BTE and NOX; and similar peak in-cylinder pressure, CO2, PM and GMD in comparison with the diesel mode. In addition, the F + B mode has the effects between those of the fumigation and blended modes. Among the three fueling modes, the blended mode gives the highest engine performance and lowest emissions, except for NOX. In contrast, the fumigation mode gives the worst engine performance and emissions, except for NOX.

The Impact of Diesel/LPG Dual Fuel on Performance and Emissions in a Single Cylinder Diesel Generator

Compared to other engines of the same size, diesel engines are more economical in addition to their ability to generate high power. For this reason, they are widely used in many fields such as industry, agriculture, transportation, electricity generation. The increasing environmental concerns and diminishing oil resources led researchers to improve fuel consumption and emissions. In this context, the usage of Liquefied Petroleum Gas (LPG) fuel in diesel engines is one of the important research subjects that has been keeping up to date. This paper investigates the effects of LPG direct injection towards the end of air inlet period on engine emissions and performance characteristics. A four-stroke, air cooled, single cylinder diesel engine was modified to direct injection of LPG for diesel/LPG dual fuel operation. An Electronic Control Unit (ECU) was designed and used to adjust LPG injection timing and duration. LPG injection rates were selected as 30%, 50% and 70% on a mass base. The test engine was operated at 3000 rpm constant engine speed under varying load conditions. Throughout the experiments, it was observed that smoke density significantly reduced on the dual-fuel operation, compared to the pure diesel operation. Carbon Monoxide (CO) and Hydrocarbon (HC) emissions decreased by 30% and 20%, respectively. Brake Specific Fuel Consumption (BSFC) decreased by 8%. Nitrogen Oxide (NOx) emissions increased by 6% while effective efficiency increased up to 1.25%.

An experimental investigation of biodiesel-biogas dual-fuel engine based on energy and exergy analysis

In the present work, exergy analysis has been performed on the biodiesel-biogas dual fuel (DF) engine. The DF operation has been studied with biodiesel (Jatropha curcas) as the pilot fuel to ignite the main fuel (biogas). The experiments were performed at a constant engine speed of 1500 rpm with varying engine loads and optimised injection timings for both diesel and DF modes. The results indicate that DF operation at low load produces poor performance and emission characteristics, however, no significant variations were observed between diesel-DF and biodiesel-DF operations. At 23% of engine load, exergy efficiencies were found to be 8.53% and 8.4% for diesel-DF and biodiesel-DF operations respectively; compared to 12.57% for pure diesel operation. Nevertheless, at higher loads, exergetic performances of DF operations were significantly improved. Furthermore, oxides of nitrogen (NOx) emissions from DF operations were significantly reduced compared to that with diesel operation.