Study of oxygenated biomass fuel blends on a diesel engine

Vegetable methyl ester was added in ethanol–diesel fuel to prevent separation of ethanol from diesel in this study. The ethanol blend proportion can be increased to 30% in volume by adding the vegetable methyl ester. Engine performance and emissions characteristics of the fuel blends were investigated on a diesel engine and compared with those of diesel fuel. Experimental results show that the torque of the engine is decreased by 6%–7% for every 10% (by volume) ethanol added to the diesel fuel without modification on the engine. Brake specific fuel consumption (BSFC) increases with the addition of oxygen from ethanol but equivalent brake specific fuel consumption (EBSFC) of oxygenated fuels is at the same level of that of diesel. Smoke and particulate matter (PM) emissions decrease significantly with the increase of oxygen content in the fuel. However, PM reduction is less significant than smoke reduction. In addition, PM components are affected by the oxygenated fuel. When blended fuels are used, nitrogen oxides (NO_x) emissions are almost the same as or slightly higher than the NO_x emissions when diesel fuel is used. Hydrocarbon (HC) is apparently decreased when the engine was fueled with ethanol–ester–diesel blends. Fuelling the engine with oxygenated diesel fuels showed increased carbon monoxide (CO) emissions at low and medium loads, but reduced CO emissions at high and full loads, when compared to pure diesel fuel.     

Comparison of emissions of a direct injection diesel engine operating on biodiesel with emulsified and fumigated methanol

Biodiesel is an alternative fuel for internal combustion engines. It can reduce carbon monoxide (CO), hydrocarbon (HC) and particulate matter (PM) emissions, compared with diesel fuel, but there is also an increase in nitrogen oxides (NO_x) emission. This study is aimed to compare the effect of applying a biodiesel with either 10% blended methanol or 10% fumigation methanol. The biodiesel used in this study was converted from waste cooking oil. Experiments were performed on a 4-cylinder naturally aspirated direct injection diesel engine operating at a constant speed of 1800 rev/min with five different engine loads. The results indicate a reduction of CO₂, NO_x, and particulate mass emissions and a reduction in mean particle diameter, in both cases, compared with diesel fuel. It is of interest to compare the two modes of fueling with methanol in combination with biodiesel. For the blended mode, there is a slightly higher brake thermal efficiency at low engine load while the fumigation mode gives slightly higher brake thermal efficiency at medium and high engine loads. In the fumigation mode, an extra fuel injection control system is required, and there is also an increase in CO, HC and NO₂ (nitrogen dioxide) and particulate emissions in the engine exhaust, which are disadvantages compared with the blended mode.     

Exhaust emissions and health effects of particulate matter from agricultural tractors operating on rapeseed oil methyl ester

Exhaust emissions and their effects on the environment and human health, such as mutagenicity of particulate matter (PM) and ozone-forming potential, must be considered when using an alternative fuel. In the present work, a test engine and two agricultural tractors ran on rapeseed oil methyl ester (biodiesel) or conventional diesel fuel as well as blends thereof. The objective was to detect any disproportionately positive or negative effects depending on blend levels, because conventional diesel fuel and biodiesel can be blended in every ratio. Generally, emissions of regulated compounds changed linearly with the blend level. The known positive and negative effects of biodiesel varied accordingly. Overall, no optimal blend was found. Increasing biodiesel content of the fuel caused a linear increase in benzene emissions in the agricultural five-mode engine test, an effect that may be explained from previous studies on precombustion chemistry. In using the test engine, it was found that PM from biodiesel significantly reduced mutagenic potential compared with that from diesel fuel, although in this work PM masses were found to be reproducibly higher for biodiesel from rapeseed oil compared with conventional diesel fuel. Ozone precursors increased 10–30% when using biodiesel compared with conventional diesel fuel. Emissions of aldehydes and alkenes are mainly responsible for this effect. N₂O emissions increased when using a catalytic converter.     

Power generation using coir-pith and wood derived producer gas in diesel engines

Partial combustion of biomass in the gasifier generates producer gas that can be used for heating purposes and as supplementary or sole fuel in internal combustion engines. In this study, the potential of coir-pith and wood chips as the feedstock for gasifier is analyzed. The performance of the gasifier–engine system is analyzed by running the engine for various producer gas–air flow ratios and at different load conditions. The system is experimentally optimized with respect to maximum diesel savings and lower emissions in the dual fuel mode operation while using coir-pith and wood chips separately. The performance and emission characteristics of the dual fuel engine are compared with that of diesel engine at different load conditions. Specific energy consumption in the dual fuel mode of operation is found to be in the higher side at all load conditions. The brake thermal efficiency of the engine while using wood chips in the dual mode operation is higher than that of coir-pith. The CO emission is higher in the case of dual fuel mode of operation as compared to that of diesel mode. In the dual fuel mode of operation, the higher diesel savings is achieved while using wood chips as compared to that of coir-pith. The comparison of the performance and emission characteristics of the dual fuel engine with diesel engine is also described.     

Combustion and emissions characteristics of compression-ignition engine using dual ammonia-diesel fuel

This study investigated the combustion and emissions characteristics of a compression-ignition engine using a dual-fuel approach with ammonia and diesel fuel. Ammonia can be regarded as a hydrogen carrier and used as a fuel, and its combustion does not produce carbon dioxide. In this study, ammonia vapor was introduced into the intake manifold and diesel fuel was injected into the cylinder to initiate combustion. The test engine was a four-cylinder, turbocharged diesel engine with slight modifications to the intake manifold for ammonia induction. An ammonia fueling system was developed, and various combinations of ammonia and diesel fuel were successfully tested. One scheme was to use different combinations of ammonia and diesel fuel to achieve a constant engine power. The other was to use a small quantity of diesel fuel and vary the amount of ammonia to achieve variable engine power. Under the constant engine power operation, in order to achieve favorable fuel efficiency, the preferred operation range was to use 40-60% energy provided by diesel fuel in conjunction with 60-40% energy supplied by ammonia. Exhaust carbon monoxide and hydrocarbon emissions using the dual-fuel approach were generally higher than those of using pure diesel fuel to achieve the same power output, while NO_x emissions varied with different fueling combinations. NO_x emissions could be reduced if ammonia accounted for less than 40% of the total fuel energy due to the lower combustion temperature resulting in lower thermal NO_x. If ammonia accounted for the majority of the fuel energy, NO_x emissions increased significantly due to the fuel-bound nitrogen. On the other hand, soot emissions could be reduced significantly if a significant amount of ammonia was used due to the lack of carbon present in the combination of fuels. Despite the overall high ammonia conversion efficiency (nearly 100%), exhaust ammonia emissions ranged from 1000 to 3000 ppmV and further after-treatment will be required due to health concerns. On the other hand, the variable engine power operation resulted in relatively poor fuel efficiency and high exhaust ammonia emissions due to the lack of diesel energy to initiate effective combustion of the lean ammonia-air mixture. The in-cylinder pressure history was also analyzed, and results indicated that ignition delay increased with increasing amounts of ammonia due to its high resistance to autoignition. The peak cylinder pressure also decreased because of the lower combustion temperature of ammonia. It is recommended that further combustion optimization using direct ammonia/diesel injection strategies be performed to increase the combustion efficiency and reduce exhaust ammonia emissions.     

Effect of variation in LPG composition on emissions and performance in a dual fuel diesel engine

This paper investigates the effect of variation in LPG composition on emissions and performance characteristics in a dual fuel engine run on diesel fuel and five gaseous fuel of LPG with different composition. To quantify the best LPG composition for dual fuel operation especially in order to improve the exhaust emissions quality while maintaining high thermal efficiency comparable to a conventional diesel engine, a two-cylinder, naturally aspirated, four-stroke, DI diesel engine converted to run as pilot-injected dual fuel engine. The tests and data collection were performed under various conditions of load at constant engine speed. From the results, it is observed that the exhaust emissions and fuel conversion efficiency of the dual fuel engine are found to be affected when different LPG composition is used as higher butane content lead to lower NO_x levels while higher propane content reduces CO levels. Fuel #3 (70% propane, 30% butane) with mass fraction 40% substitution of the diesel fuel was the best LPG composition in the dual fuel operation except that at part loads. Also, tests were made for fuel #3-diesel blend in the dual fuel operation at part loads to improve the engine performances and exhaust emissions by using the Exhaust Gas Recirculation (EGR) method.     

Potential for reducing emissions in a diesel engine by fuelling with conventional biodiesel and Fischer-Tropsch diesel

A gas-to-liquid (GTL) fuel derived from Low Temperature Fischer-Tropsch process has been tested in an automotive diesel engine fulfilling Euro 4 emissions regulations. Both regulated and non-regulated emissions have been compared with those of a commercial diesel fuel, a commercial biodiesel fuel and a GTL-biodiesel fuel (30% and 70% v/v, respectively) in order to check blending properties, synergistic effects and compatibility between first and second generation production technologies for biofuel consumption in current diesel engines. After presenting a detailed literature review, and confirming that similar efficiencies are attained with the four tested fuels under identical road-like operating conditions (this meaning fuel consumption is inversely proportional to their heating values), significant reductions in smoke opacity, particulate matter emissions and particle number concentration were observed with both GTL and biodiesel fuels, with small changes in NO_x emissions. Compared with the reductions in PM emissions derived from the use of biodiesel fuels, those derived from using GTL fuels were quite similar, despite its lower soot emissions reductions. This can be explained by the lower volatile organic fraction of the PM in the case of GTL. By adequately blending both fuels, a considerable potential to optimise the engine emissions trade-off is foreseen.     

Transient testing of soy methyl ester fuels in an indirect injection,compression ignition engine

An evaluation of the exhaust emissions from a compression ignition engine for fuels composed of 100 and 30% methyl esters of soy oil (SME) is described. These fuels were compared with a low-sulfur, petroleum #2 diesel fuel in a Caterpillar 3304, prechamber, 75 kW diesel engine, operated over heavy- and light-duty transient test cycles developed by the United States Bureau of Mines. More than 60 h of testing was performed on each fuel. The objective was to determine the influence of the fuels upon diesel particulate matter (DPM) and gaseous emissions. The effect of a modern diesel oxidation catalyst (DOC) also was determined in an effort to minimize emissions. Neat SME produced a higher volatile fraction of the DPM, but much less carbon soot fraction, leading to overall DPM reductions of 23 to 30% for the light- and heavy-duty transients. The DOC further reduced the volatile fraction and the total DPM. The SME fuel reduced gaseous emissions of CO by 23% and hydrocarbons by over 30% without increasing NO_x. The DOC further reduced CO and hydrocarbon levels. Mutagenicity of the SME exhaust was low. Results indicate that SME fuel, used with a proper DOC, may be a feasible emission reduction technology for underground mines. References to specific products do not imply endorsement by the U.S. Bureau of Mines, a now defunct agency.     

Emissions from large-scale medium-speed diesel engines: 1. Influence of engine operation mode and turbocharger

The operation of four – stroke diesel engines in either propulsion or generator mode application has a strong influence on gaseous, smoke (soot) and particulates emissions. Tests were made with a supercharged after-cooled large-scale diesel engine (mean speed  500 rpm, power per cylinder  1 MW) burning mainly heavy fuel oil. Gaseous emissions (NOx, CO, HC) were measured according to the IMO technical code, smoke (soot) emissions were determined optically and particulate matter (PM) was measured using a gravimetric impactor for five size fractions. Impact on gaseous emissions, smoke (soot) and PM was found when analysing the effects of the engine operating mode, fuel nozzle, start of injection (SOI), and load (speed). Results show that the exhaust emission was also highly dependent on the engine turbocharger system, especially the by-pass control, but was not affected by waste gate control. The gaseous and soot emissions were less for the generator mode in the total load region, decreasing with the load. PM emissions were found to decrease with the load for the propulsion mode, while showing an increase with the load for the generator mode.     

Emission characteristics using methyl soyate–ethanol–diesel fuel blends on a diesel engine

A blend of 20% (v/v) ethanol/methyl soyate was prepared and added to diesel fuel as an oxygenated additive at volume percent levels of 15 and 20% (denoted as BE15 and BE20). We also prepared a blend containing 20% methyl soyate in diesel fuel (denoted as B20). The fuel blends that did not have any other additive were stable for up to 3 months. Engine performance and emission characteristics of the three different fuels in a diesel engine were investigated and compared with the base diesel fuel. Observations showed that particulate matter (PM) emission decreased with increasing oxygenate content in the fuels but nitrogen oxides (NO_x) emissions increased. The diesel engine fueled by BE20 emitted significantly less PM and a lower Bosch smoke number but the highest NO_x among the fuel blends tested. All the oxygenate fuels produced moderately lower CO emissions relative to diesel fuel. The B20 blend emitted less total hydrocarbon (THC) emissions compared with base diesel fuel. This was opposite to the fuel blends containing ethanol (BE15, BE20), which produced much higher THC emission.     

Influence of waste cooking oil biodiesel on the nanostructure and volatility of particles emitted by a direct-injection diesel engine

To reduce air pollution and the reliance on fossil fuel, biodiesel has been widely investigated as an alternative fuel for diesel engines. The purpose of this study is to investigate the influence of waste cooking oil (WCO) biodiesel on the physical properties and the oxidation reactivity of the particles emitted by a diesel engine operating on WCO biodiesel as the main fuel. Experiments were conducted on a direct-injection diesel engine fueled with biodiesel, B75 (75% biodiesel and 25% diesel on volume basis, v/v), B50, B20, and diesel fuel, at five engine loads and at an engine speed of 1920 rev/min. Particulate samples were collected to analyze the particulate nanostructure, volatility, and oxidation characteristics. Biodiesel or low-load operation leads to smaller primary particles and more disordered nanostructures having shorter and more curved graphene layers. It can be found that particles from biodiesel, blended fuels, or low-load operation have higher volatile mass fractions and faster oxidation reaction rates than particles from diesel or heavy-load operation. The higher oxidation reaction rates are due mainly to the smaller particle size, the more disordered nanostructure, and the higher volatile mass fraction. It is also found that changes in primary particle size and particulate nanostructure are not directly proportional to the biodiesel content, while changes in particulate volatility and particulate oxidation reactivity are proportional to the biodiesel content. The use of biodiesel can enhance particulate oxidation reactivity and the regeneration of soot particles in an after-treatment device.

Copyright © 2016 American Association for Aerosol Research     

Influence of fuel sulfur on the characterization of PM10 from a diesel engine

To study the effects of fuel sulfur content on the characteristics of diesel particle emitted from a typical engine used in China, two types of diesel fuel with sulfur content of 30 ppm and 500 ppm were used in this engine dynamometer test under six operation conditions corresponding to 20%, 50% and 80% load at 1400 rpm and 2300 rpm engine speeds, respectively. Gaseous pollutants and particulate matter (PM) emissions were sampled with AVL AMA4000 and Model 130 High-Flow Impactor (MSP Corp), respectively. More specifically, the PM mass, total carbon (TC), organic carbon (OC), elemental carbon (EC) and water-soluble ion distribution were also measured. Compared with high sulfur diesel, the application of low sulfur diesel can lower fuel-based PM emissions by 9.2-56.6%. At 1400 rpm, the low sulfur diesel decreased both OC and EC by 5-34% and about 20%; while at 2300 rpm, the low sulfur fuel decreased OC by 33-57% and increased EC emission, resulting in a lower OC/EC ratio. The evidence implicating that OC oxidation was promoted by low sulfur diesel, but the effect on EC oxidation was dependent on engine speed. The linear regression has been conducted between TC and PM₁₀, and the slopes were 0.88 and 0.80 for low sulfur diesel and high sulfur one, respectively. Higher sulfate content was detected in the 0.13 μm particles when using the high sulfur diesel, but the percentage of sulfate was 0.9% for PM₁₀ from both diesel fuels. Comparing with that of 500 ppm, EC increased sharply to a maximum of 114% in particles of 0.13 μm when using 30 ppm sulfur diesel at 2300 rpm.     

X-ray scattering and spectroscopy studies on diesel soot from oxygenated fuel under various engine load conditions

Diesel soot from reference diesel fuel and oxygenated fuel under idle and load engine conditions was investigated with X-ray scattering and X-ray carbon K-edge absorption spectroscopy. Up to five characteristic size ranges were found. Idle soot was generally found to have larger primary particles and aggregates but smaller crystallites, than load soot. Load soot has a higher degree of crystallinity than idle soot. Adding oxygenates to diesel fuel enhanced differences in the characteristics of diesel soot, or even reversed them. Aromaticity of idle soot from oxygenated diesel fuel was significantly larger than from the corresponding load soot. Carbon near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was applied to gather information about the presence of relative amounts of carbon double bonds (CC, CO) and carbon single bonds (C-H, C-OH, COOH). Using scanning X-ray transmission microspectroscopy (STXM), the relative amounts of these carbon bond states were shown to vary spatially over distances approximately 50 to 100 nm. The results from the X-ray techniques are supported by thermo-gravimetry analysis and high-resolution transmission electron microscopy.     

Emission characteristics of diesel, gas to liquid, and biodiesel-blended fuels in a diesel engine for passenger cars

The need for diversification of energy sources and reducing various emissions including CO₂ emission in diesel engine can be met with alternative diesel fuels such as gas to liquid (GTL) and GTL–biodiesel blends. But there should be a clear understanding of the combustion and engine-out emission characteristics for alternative fuels. In this respect, an experimental study was conducted on a 2.0 L 4 cylinders turbocharged diesel engine fuelled with those alternative diesel fuels to investigate the engine-out emission characteristics under various steady-state engine operating conditions. The results revealed that noticeable decreases in THC (22–56%) and CO (16–52%) emissions for GTL–biodiesel blends were observed, whereas NOx emissions for GTL–biodiesel blends increased by a maximum of 12% compared to diesel. With regard to particle size distributions (PSDs) for GTL–biodiesel blends, the particulate matter (PM) number concentration in accumulation mode decreased, as a result of the excess oxygen content in biodiesel. Contrary to the tendency in the accumulation mode, there was a slight increase in the PM number concentration in the nucleation mode under the operating conditions wherein the exhaust gas recirculation (EGR) strategy was applied. The total PM number concentration for G + BD40 decreased by a maximum of 46% compared to that for diesel. From these results of enhanced emission characteristics compared to diesel and GTL fuel, the potential for the use of GTL–biodiesel blends could be confirmed.     

Characterization of Particulate Matter Morphology and Volatility from a Compression-Ignition Natural-Gas Direct-Injection Engine

The particulate matter (PM) emitted from a single-cylinder compression-ignition, natural-gas engine fitted with a High-Pressure Direct-Injection (HPDI) system distinctly different from a duel fuel engine was investigated, and characterized by size distribution, morphology, mass-mobility exponent, effective density, volatility, mixing state, and primary particle size using transmission electron microscopy (TEM), and tandem measurements from differential mobility analyzers (DMA) and a centrifugal particle mass analyzer (CPMA). Six engine conditions were selected with varying load, speed, exhaust gas recirculation (EGR) fraction, and fuel delivery strategy. An increase in engine load increased both the number concentration and the geometric mean diameter of the particulate. The fraction of the number of purely volatile particles to total number of particles (number volatile fraction, NVF) was found to decrease as load increased, although at the lower speed, partially premixed mode, the lowest NVF. All size distributions were also found to be unimodal. The size-segregated ratio of the mass of internally mixed volatile material to total particle mass (mass volatile fraction, MVF) decreased with load and with particle mobility-equivalent diameter. A roughly constant amount of volatile material is likely produced at each engine mode, and the decrease in MVF is due to the increase in PM number with load. Effective density and mass-mobility exponent of the non-volatile soot at the different engine loads were the same or slightly higher than soot from traditional diesel engines. Denuded effective density trends were observed to collapse to approximately the same line, although engine modes with higher MVFs had slightly higher effective densities suggesting that the soot structures have collapsed into more dense shapes—a suspicion that is confirmed with TEM images. TEM results also indicated that primary particle size first decreases from low to medium load, then increases from medium to high load. An increase in EGR was also seen to increase primary particle size. Coefficients were determined for a relation that gives primary particle diameter as a function of projected area equivalent diameter. A decrease in load or speed results in a stronger correlation.

Copyright 2015 American Association for Aerosol Research     

Compression ignition engine modifications for straight plant oil fueling in remote contexts: Modification design and short-run testing

Though many plant oils have a similar energy density to fossil diesel fuel, several properties of plant oils are considerably different from those of diesel. Engine modifications can overcome some of these differences. An engine modification kit has been designed and tested for a slow speed, stationary, indirect-injection diesel engine - the Lister-type CS 6/1, common throughout the developing world. The kit allows waste vegetable oil fueling with similar performance to that of diesel fueling. The kit’s simple yet robust design is targeted for use as a development mechanism, allowing remote farmers to use locally grown plant oils as a diesel substitute.The modification kit includes a preheating system and the tuning of the injector pressure and timing to better atomize given the unique properties of straight plant oils. The design methodology for the modifications is detailed and a suite of performance test results are described including fuel consumption, efficiency, pre-combustion chamber pressure, and various emissions. The results of the study show how a combination of preheating the high pressure fuel line, advancing the injector timing and increasing the injector valve opening pressure allows this engine to efficiently utilize plant oils as a diesel fuel substitute, potentially aiding remote rural farmers with a lower cost, sustainable fuel source - enabling important agro-processing mechanization in parts of the world that needs it most.     

Laboratory endurance test of a sunflower oil blend in a diesel engine

The effects of using a 25/75 blend (v/v) of alkali refined sunflower oil and diesel fuel in a direct-injection diesel engine were compared to a baseline test with diesel fuel. There were no significant problems with engine operation during the baseline test. However, problems were experienced while using the blended fuel. The major problems were (a) abnormal buildup on the injection nozzle-tips, (b) injector needle sticking, (c) secondary injection, (d) carbon buildup in the intake ports, (e) carbon deposits on the exhaust valve stems, (f) carbon filling of the compression ring grooves, and (g) abnormal lacquer and varnish buildup on the third piston land. The 25.75 blend cannot be recommended for long-term use in a direct-injection engine.     

In situ formation of onion-like carbon from the evaporation of ultra-dispersed nanodiamonds

We report the in situ formation of onion-like carbon (OLC) by evaporation from a nanodiamond source under ultra-high vacuum conditions. The OLC is characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) and is found to be highly defective but completely separated. The absence of any signature in XPS, Raman spectra and TEM associated with nanodiamond in the film suggests that the OLC is formed from carbon vapor or by the direct evaporation of only the smallest particles resulting from nanodiamond graphitization. The method thus provides a route to the formation of individually separated OLC nanoparticles.     

Investigation on Particulate Oxidation from a DI Diesel Engine Fueled with Three Fuels

In this study, particles generated from a direct-injection (DI) diesel engine fueled with biodiesel, ultra-low-sulfur diesel (ULSD, <10 ppm-wt), and low-sulfur diesel (LSD, <500 ppm-wt) were investigated experimentally for their oxidation properties, using the thermogravimetric analysis (TGA), at five engine loads. Kinetic analysis of particulate oxidation was conducted based on the mass loss curves obtained from the TGA. The activation energy was found to be in the range of 142–175, 76–127, and 133–162 kJ/mol for the particulate samples for ULSD, biodiesel, and LSD, respectively. The particulate oxidation rate decreases with the increase of engine load for each fuel, and at each engine load, the oxidation rate decreases in the order of biodiesel, LSD, and ULSD. The primary particle size, nanostructure, and volatile fraction were also investigated for different particulate samples. The results indicate that the higher oxidation rate of biodiesel particles could be related to the smaller primary particle size, the more disordered nanostructure, and the larger volatile fraction, compared with the ULSD and LSD particles. The increase of sulfur content in a diesel fuel has a limited influence on primary particle size and nanostructure, while inducing a larger volatile fraction, which might be one of the reasons for the stronger oxidative reactivity of the LSD particles, compared with the ULSD particles.

Copyright 2012 American Association for Aerosol Research