Application of JP-8 in a heavy duty diesel engine

An experimental study was carried out to investigate the combustion and emission of JP-8 and diesel fuel in an optically-accessible single-cylinder heavy duty diesel engine equipped with a high pressure common-rail injection system in order to evaluate the feasibility of JP-8 application in diesel engine. The basic spray characteristics, including spray tip penetration and spray angle, were investigated with macroscopic spray images obtained by the Mie-scattering method. The combustion and emission characteristics were analyzed on the basis of the results obtained from the spray experiments. Visualization by direct imaging was used to characterize the combustion process.It was found that JP-8 had a shorter spray tip penetration and wider spray angle than diesel fuel mainly due to the faster vaporization characteristic of JP-8. The peak heat release rate was higher and the premixed burn portion was larger with JP-8 due to its superior mixing rate through faster vaporization characteristics. Furthermore, ignition delay with JP-8 was longer than that with diesel fuel due to the lower cetane number of JP-8. In terms of emission, JP-8 showed a benefit in smoke reduction while it produced larger amounts of HC and NO_x. Longer ignition delay and accelerated oxidation in the late stage of JP-8 combustion were verified by direct imaging.     

The effect of diluent on flame structure and laminar burning speeds of JP-8/oxidizer/diluent premixed flames

Experimental studies have been performed to investigate the flame structure and laminar burning speed of JP-8/oxidizer/diluent premixed flames at high temperatures and pressures. Three different diluents including argon, helium, and a mixture of 14% CO₂ and 86% N₂ (extra diluent gases), were used. The experiments were carried out in two constant volume spherical and cylindrical vessels. Laminar burning speeds were measured using a thermodynamics model based on the pressure rise method. Temperatures from 493 to 700 K and pressures from 1 to 11.5 atm were investigated. Extra diluent gases (EDG) decrease the laminar burning speeds but do not greatly impact the stability of the flame compared to JP-8/air. Replacing nitrogen in the air with argon and helium increases the range of temperature and pressure in the experiments. Helium as a diluent also increases the temperature and pressure range of stable flame as well as the laminar burning speed. Power law correlations have been developed for laminar burning speeds of JP-8/air/EDG and JP-8/oxygen/helium mixtures at a temperature range of 493-700 K and a pressure range of 1-10 atm for lean mixtures.     

Aviation fuel JP-5 and biodiesel on a diesel engine

Naval aviation turbine fuel, JP-5, has been accepted as alternative to JP-8 in the frame of the Single Fuel Policy. This has resulted in some ongoing research on JP-5 fuel for its application as a naval single fuel. The necessity to cope with the environmental problems identified in the process of implementing the Single Fuel Policy as well as the strict requirements of modern diesel engines has lead to the need of improved single fuel quality. The development of biomass derived substitutes for diesel, such as biodiesel, is a possible attractive solution. The present paper is an effort to evaluate JP-5 along with diesel and biodiesel for use in a diesel engine. These fuels were used alone and in various mixture fractions in a single cylinder stationary diesel engine in order to evaluate their performance under defined operating conditions of the engine. JP-5 reduced both the NOx and particulate matter emissions as compared to the reference fuel case. Biodiesel significantly lowered particulate emissions, but slightly increased NOx emissions and fuel consumption. Fuel sulfur content has an undesired effect on smoke opacity. Biodiesel increased the fuel consumption when added to petroleum fuels and the increase was larger at high engine loads. Diesel and JP-5 showed similar fuel consumption, with diesel consumption increasing at high engine loads. Ternary blends showed similar behavior. The blends with lower biodiesel content showed lower volumetric fuel consumption.     

Hydrodesulfurization of JP-8 fuel and its microchannel distillate using steam reformate

A field-deployable process for generation of clean desulfurized fuel from JP-8 feedstock is described. The process employs a compact hydrodesulfurization unit, operated in the vapor phase using steam reformate provided by an integrated steam reformer, as a replacement for hydrogen co-feed gas. The process includes a microchannel distillation unit upstream of the hydrodesulfurizer unit, which allows use of a lighter feed fraction to be processed in place of the full JP-8. The novel microchannel distillation concept is described and performance data for the unit, operating as a rectifier, are provided. Since the generated light fraction fuel from microchannel distillation contains fewer refractory sulfur components, the subsequent HDS process can readily achieve a significant sulfur reduction. The overall process can generate an ultra-clean JP-8 light fraction fuel with approximately 300 ppb sulfur residual. Hydrodesulfurization of full JP-8 fuel without the microchannel distillation unit was also studied. The effect of various operating parameters on the overall hydrodesulfurization performance, as well as the conversion of some individual sulfur components such as 2,3-dimethyl-benzothiophene, 2,3,5-trimethyl-benzothiophene and 2,3,7-trimethyl-benzothiophene, were investigated. Steam content in reformate at 30 mol% or less was found to improve HDS performance compared with dry reformate, despite a decrease in hydrogen partial pressure. However, at even higher concentrations of steam, hydrodesulfurization performance decreased.     

Flame structure and laminar burning speeds of JP-8/air premixed mixtures at high temperatures and pressures

Jet propellant 8 (JP-8)/air laminar burning speed was experimentally measured and its flame structure was studied at high temperatures and pressures using a high-speed camera. The experimental facilities included a spherical vessel, used for the measurement of burning speed, and a cylindrical vessel, used in a shadowgraph system to study flame shape and structure and to measure burning speed. A thermodynamic model was developed to calculate burning speeds using the dynamic pressure rise in the vessel due to the combustion process. The model consists of a central burned gas core of variable temperature surrounded first by a reaction sheet, then by an unburned gas shell with uniform temperature and lastly by thermal boundary layers at the wall and electrodes. Radiation from burned gases to the walls was also included in the model. Burning speeds of laminar flames of JP-8/air were calculated for a wide range of conditions. A Power law correlation was developed to calculate laminar burning speed at temperatures ranging from 500-700 K, pressures of 1-6 atm and equivalence ratios of 0.8-1. Flame structure and cell formations were observed using an optical system. Experimental results showed that pressure and the fuel-air equivalence ratio have a strong influence on flame structure.     

Effect of alternative fuels on exhaust emissions during diesel engine operation with matched combustion phasing

The present work focuses on an experimental comparison of diesel emissions produced by three fuels: an ultra low sulfur diesel fuel (BP15), a pure soybean methyl-ester biodiesel fuel (B100), and a synthetic Fischer-Tropsch fuel (FT), practically free of sulfur and aromatic compounds, and produced in a gas-to-liquid process. The study was carried out using a 2.5 L direct injection common-rail turbodiesel engine operated at 2400 rpm and 64 N m torque (19% of maximum torque). The engine was tested with single and split (pilot and main) injections and without exhaust gas recirculation (EGR). The study has two objectives. The first objective is to investigate the impact of the start of injection (SOI) on performance and emissions of each fuel. The second objective is to study the isolated impacts of the test fuels on pollutant emissions by adjusting the injection parameters (SOI and fuel rail pressure) for each fuel, while producing practically the same combustion phasing. When the combustion phasing occurs similarly, this study has confirmed that the FT fuel can reduce all regulated diesel emissions under both single and split injection strategies. Finally, it has been confirmed that biodiesel can reduce particle mean diameter in comparison with BP15. However, higher PM mass emission for B100 has been observed under the condition of matched combustion phasing. The increase of the PM mass emission is probably due to the unburned or partially burned hydrocarbon (HC) emissions.     

Determination of sulfur contaminants in military jet fuels

Military jet fuel samples have been characterized by gas chromatography with a sulfur chemiluminescence detector and a mass spectrometer (GC-SCD-MS). Sixteen distinct organosulfur compounds were quantified in the jet fuel samples. The structures and the concentrations for seven of them are determined in this study. Although the total sulfur content of jet fuel varies from sample to sample, the individual organosulfur distribution remains unchanged for six jet fuel samples obtained over a 4-year period. The two major sulfur compounds are determined to be 2,3-dimethylbenzothiophene and 2,3,7-trimethylbenzothiophene. These two major compounds are determined to be good representative compounds in jet fuel surrogates for computational studies of jet fuel catalysis such as JP-8 reformation.     

Deposition characteristics of diesel and bio-diesel fuels

The aim of this study is to investigate the deposition characteristics of different types of fuels by using the hot surface deposition test (HSDT) as a substitute procedure for real engine deposit tests. Deposit development, deposit compositions and deposit surface temperature fluctuation for diesel fuels and bio-diesel fuels (palm oil based and coconut oil based) are discussed. Deposit development depended on hot surface temperature, overlapping conditions, fuels, deposit properties, initial stage of deposition and competition phenomena during deposit formation. Results show DFP having 1% B100C in composition, showed a greater deposit development rate compared to DF, which resulted in a relatively large amount of deposits for DFP. However, for bio-diesel fuels, B100C obtained a slower deposit development rate compared to B100 although the test conditions were changed. Due to the lower value of MEP and shorter droplet lifetime before MEP, utilization of B100C had a greater potential in reducing deposit formation compared to B100.     

Determination of JP-8 components in soils using solid-phase microextraction–gas chromatography–mass spectrometry

Jet Propellant-8 (JP-8) is a military fuel associated with a large percentage of chemical exposures documented by the US Department of Defense. A fast and sensitive solid-phase microextraction–gas chromatographic–mass spectrometric (SPME–GC–MS) method has been developed for the determination of 34 ‘marker compounds’ found in JP-8. Linear ranges (R² > 0.99) were determined for each marker component and precision was measured (<16% RSD) for these components over four concentrations within each calibration range. The method was applied for the analysis of JP-8 components from soil. The use of SPME over other sample extraction techniques eliminates solvents, minimizes sample handling, and increases sensitivity.     

Emissions from different alternative diesel fuels operating with single and split fuel injection

Few factors affect diesel combustion and emissions more significantly than the composition of the fuel and the fuel injection process. In this paper, both of these factors are considered by comparing conventional, synthetic and vegetable oil-derived diesel fuels and by comparing a single pulse injection and a split (pilot and main) injection process. This paper focuses on characterization of the combustion process and emissions produced by three substantially different diesel fuels: an ultra low sulfur diesel fuel (BP15), a pure soybean methyl ester (B100), and a synthetic, practically free of sulfur and aromatic compounds, Fischer-Tropsch fuel (FT) produced in a gas-to-liquid process. The study was carried out in a direct injection (DI) 2.5 L common-rail turbodiesel engine working at four engine operation modes, spanning conditions of most interest in the engine map. In all modes the engine was tested with single and split injection (pilot and main), with constant start of injection (SOI), and without exhaust gas recirculation (EGR). Using the results from thermodynamic analysis, this study confirms that the ignition character of the fuel affects the start of the combustion process, notably for the whole combustion process when the single injection is used, and during the combustion process after the pilot injection when the split injection is used. In general, the FT fuel can reduce both NOx and PM specific emissions in all modes under both single and split injection modes, bypassing the nitrogen oxides-particulate matter (NOx-PM) trade-off. Finally, this work confirms that biodiesel can reduce the particle concentration. However, in some cases an increase of PM mass emission has been observed and this increase of the PM mass emission is due to unburned or partially burned hydrocarbon (HC) emissions.     

Deep desulfurization of diesel fuels: kinetic modeling of model compounds in trickle-bed

Five catalysts with different hydrodesulfurization (HDS) and hydrogenation activity were tested in HDS of fresh crude heavy atmospheric gas oil (HAGO) (1.33 wt% S), two partially hydrotreated HAGO (1100 and 115 ppm S) and two model compounds, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT), dissolved in model solvents and HAGO. Aromatic compounds in the liquid decreased significantly the HDS rate of 4,6-DMDBT, especially for catalysts with high hydrogenation activity. H₂S displayed a similar inhibition effect with all catalysts. These effects were extremely pronounced in HAGO where the DBT HDS rate decreased by a factor of 10 while 4,6-DMDBT – of 20 relative to paraffinic solvent. The feasibility of using a highly active hydrogenation catalyst for deep HDS of HAGO is diminished by the strong impact of aromatics.     

Combustion and emissions of a DI diesel engine fuelled with diesel-oxygenate blends

Combustion and emissions of a DI diesel engine fuelled with diesel-oxygenate blends were investigated. The results show that there exist the different behaviors in the combustion between the diesel-diglyme blends and the other five diesel-oxygenate blends as the diglyme has the higher cetane number than that of diesel fuel while the other five oxygenates have the lower cetane number than that of diesel fuel. The smoke concentration decreases regardless of the types of oxygenate additives, and the smoke decreases with the increase of the oxygen mass fraction in the blends without increasing the NO_x and engine thermal efficiency. The reduction of smoke is strongly related to the oxygen-content of blends. CO and HC concentrations decrease with the increase of oxygen mass fraction in the blends. Unlike conventional diesel engines fueled with pure diesel fuel, engine operating on the diesel-oxygenate blends presents a flat NO_x/Smoke tradeoff curve versus oxygen mass fraction.     

Regulated and unregulated emissions from a light-duty diesel engine with different sulfur content fuels

Five different sulfur content fuels were used on a light-duty diesel engine to study the effect of fuel sulfur on emissions. Four regulated emissions: smoke, nitrogen oxide (NO_x), unburned hydrocarbon (HC) and carbon monoxide (CO) emissions of the engine were investigated, as well as three unregulated emissions: formaldehyde (HCHO), acetaldehyde (MECHO) and sulfur dioxide (SO₂). The smoke emission decreases continuously and remarkably with the fuel sulfur content, and the fuel sulfur has more influence on smoke emission at lower engine load. The concentration of NO_x emissions did not change significantly with the different sulfur content fuels. As the fuel sulfur content decreases, the concentrations of HC and CO emissions have distinct reduction. The HCHO emission values are very low. The MECHO emission decreases with increasing engine load, and it continuously decreases with the fuel sulfur content and it could not be detected at higher engine load with 50 ppm sulfur fuel. The SO₂ emission increases continuously with the engine load, and obviously decreases with the fuel sulfur contents.     

Comparison of exhaust emissions and their mutagenicity from the combustion of biodiesel, vegetable oil, gas-to-liquid and petrodiesel fuels

Efforts are under way to reduce diesel engine emissions (DEE) and their content of carcinogenic and mutagenic polycyclic aromatic hydrocarbons (PAH). Previously, we observed reduced PAH emissions and DEE mutagenicity caused by reformulated or newly developed fuels. The use of rapeseed oil as diesel engine fuel is growing in German transportation businesses and agriculture. We now compared the mutagenic effects of DEE from rapeseed oil (RSO), rapeseed methyl ester (RME, biodiesel), natural gas-derived synthetic fuel (gas-to-liquid, GTL), and a reference petrodiesel fuel (DF) generated by a heavy-duty truck diesel engine using the European Stationary Cycle. Mutagenicity of the particle extracts and the condensates was tested using the Salmonella typhimurium mammalian microsome assay with strains TA98 and TA100. The RSO particle extracts increased the mutagenic effects by factors of 9.7 up to 17 in strain TA98 and of 5.4 up to 6.4 in strain TA100 compared with the reference DF. The RSO condensates caused up to three times stronger mutagenicity than the reference fuel. RME extracts had a moderate but significantly higher mutagenic response in assays of TA98 with metabolic activation and TA100 without metabolic activation. GTL samples did not differ significantly from DF. Regulated emissions (hydrocarbons, carbon monoxide, nitrogen oxides (NO_x), and particulate matter) remained below the limits except for an increase in NO_x exhaust emissions of up to 15% from the tested biofuels.     

Flue gas cleaning in power stations by using electron beam technology. Influence on PAH emissions

The electron beam technology (EBT), proven treatment for SO₂ and NO_x removal, is applied to different power stations as hot gas cleaning system. In this paper, an assessment of this technique installed in a Bulgarian power station on organic emissions is analyzed. The Polycyclic Aromatic Hydrocarbons (PAH) content, not only emitted in the gas phase but also trapped in the solid phase, has been carried out before and after the irradiation. The main aim has been to know whether the EBT affects organic emissions, like PAH, as it happens with inorganic pollutants, like SO₂ and NO_x, studying EBT effects from an organic environmental point of view.     

Hot gas cleaning in power stations by using electron beam technology. Influence on PAH emissions

The Electron Beam Technology (EBT), proven treatment for SO₂ and NO_x removal, is applied to different power stations as a hot gas cleaning system. In this paper, an assessment of this technique installed in a Bulgarian power station on organic emissions is analyzed. The Polycyclic Aromatic Hydrocarbons (PAH) content, not only emitted in the gas phase but also trapped in the solid phase, has been carried out before and after the irradiation. The main aim has been to know whether the EBT affects organic emissions, like PAH, as it happens with inorganic pollutants, like SO₂ and NO_x, studying EBT effects from an organic environmental point of view.     

Experimental study of the performance and emission characteristics of diesel engine using direct and indirect injection systems and different fuels

An experimental study of the performance and emission characteristics of diesel engine using direct and indirect injection combustion systems are carried out on a same model of two diesel engines fuelled with diesel and the blend of diesel and Chinese pistache biodiesel. The results show that the NO_x emissions from the indirect injection combustion system (ICS) fuelled with diesel are reduced by around two thirds, compared to that from direct injection combustion system (DCS). Smoke emissions from the engine using ICS are all significantly lower than that of DCS, reduced by 70% for diesel; by 50-60% for the blend. The brake thermal efficiencies (BTEs) reduced by 8-10%, compared to that of DCS; the fuel consumptions increased by around 7-9%. It is also found that carbon monoxide (CO) emissions are reduced when the engine run at engine high power outputs, so are the hydrocarbon (HC) emissions from ICS at the peak power outputs. It is found that, when fuelled with the blend, the effects of ICS to the performance and emissions of diesel engine are very similar to that of running with diesel. For ICS engine fuelled with diesel and the blend fuel, the BSFCs for the blend are around 5% higher; the BTEs are around 2-4% lower; the reductions of NO_x from the blend fuel are 5.1-8.4% on average for the ICS; the reductions of smoke from the blend fuel are 26.8-31.7% on average for the ICS. CO emissions are around a half lower; and HC emissions are around one fifth lower, compared to that of fuelling with diesel. Comparing to that of DCS fuelled with diesel, using ICS fuelled with the blended fuel has much lower emissions. NO_x emissions decreased by 65.6% and 66.1%; smoke emissions decreased by 75.7% and 80.2%; CO emissions decreased by 55.8% and 46.0%; HC emissions decreased by 24.9% and 18.9%; with the BSFCs around 14.6-14.9% higher and the BTEs around 9.7-10.0% lower.     

Deep desulphurization of diesel fuels on bifunctional monolithic nanostructured Pt-zeolite catalysts

The preparation of Pt-zeolite catalysts, including choice of the noble metal precursor and loading (1.0–1.8 wt.%), was optimized for maximizing the catalytic activity in thiophene hydrodesulphurization (HDS) and benzene hydrogenation (HYD). According to data obtained by HRTEM, XPS, EXAFS and FTIR spectroscopy of adsorbed CO, the catalysts contained finely dispersed Pt nanoparticles (2–5 nm) located on montmorillonite and zeolite surfaces as: Pt⁰ (main, ν_CO = 2070–2095 cm⁻¹), Pt^δ+ (ν_CO = 2128 cm⁻¹) and Pt²⁺ (ν_CO = 2149–2155 cm⁻¹). It was shown that the state of Pt depended on the Si/Al zeolite ratio, montmorillonite presence and Pt precursor. The use of H₂PtCl₆ as the precursor (impregnation) promoted stabilization of an oxidized Pt state, most likely Pt(OH)_xCl_y. When Pt(NH₃)₄Cl₂ (ion-exchange) was used, the Pt⁰ and hydroxo- or oxy-complexes Pt(OH)₆²⁻ or PtO₂ were formed. The addition of the Ca-montmorillonite favoured stabilization of Pt^+δ. The Cl⁻ ions inhibit reduction of oxidized Pt state to Pt particles. The Pt-zeolite catalyst demonstrated high efficiency in ultra-deep desulphurization of DLCO. The good catalyst performance in hydrogenation activity and sulphur resistance can be explained by the favourable pore space architecture and the location and the state of the Pt clusters. The bimodal texture of the developed zeolite substrates allows realizing a concept for design of sulphur-resistant noble metal hydrotreating catalyst proposed by Song [C. Song, Shape-Selective Catalysis, Chemicals Synthesis and Hydrocarbon Processing (ACS Symposium Series 738), Washington, 1999, p. 381; Chemtech 29(3) (1999) 26].     

Effects of ethyl tert-butyl ether addition to diesel fuel on characteristics of combustion and exhaust emissions of diesel engines

The effects of ethyl tert-butyl ether (ETBE) addition to diesel fuel on the characteristics of combustion and exhaust emissions of a common rail direct injection diesel engine with high rates of cooled exhaust gas recirculation (EGR) were investigated. Test fuels were prepared by blending 0, 10, 20, 30 and 40 vol% ETBE to a commercial diesel fuel. Increasing ETBE fraction in the fuel helps to suppress the smoke emission increasing with EGR, but a too high fraction of ETBE leads to misfiring at higher EGR rates. While the combustion noise and NO_x emissions increase with increases in ETBE fraction at relatively low EGR rates, they can be suppressed to low levels by increasing EGR. Though there are no significant increases in THC and CO emissions due to ETBE addition to diesel fuel in a wide range of EGR rates, the ETBE blended fuel results in higher aldehyde emissions than the pure diesel fuel at relatively low EGR rates. With the 30% ETBE blended fuel, the operating load range of smokeless, ultra-low NO_x (<0.5 g/kWi h), and efficient diesel combustion with high rates of cooled EGR is extended to higher loads than with the pure diesel fuel.     

Biodiesel CO2 emissions: A comparison with the main fuels in the Brazilian market

The use of biodiesel is increasing as an attractive fuel due to the depleting fossil fuel resources and environmental degradation. This paper presents results of an investigation on the potentials of biodiesel as an alternative fuel and main substitute of diesel oil, comparing the CO₂ emissions of the main fuels in the Brazilian market with those of biodiesel, in pure form or blended in different proportions with diesel oil (2%, 5%, and 20%, called B2, B5, and B20, respectively). The results of the study are shown in ton CO₂ per m³ and ton CO₂ per year of fuel. The fuels were analyzed considering their chemical composition, stoichiometric combustion parameters and mean consumption for a single vehicle. The fuels studied were: gasoline, diesel oil, anhydrous ethyl alcohol (anhydrous ethanol), and biodiesel from used frying oil and from soybean oil. For the case of biodiesel, its complete life cycle and the closed carbon cycle (photosynthesis) were considered. With data provided by the Brazilian Association of Automotive Vehicle Manufacturers (ANFAVEA) for the number of vehicles produced in Brazil, the emissions of CO₂ for the national fleet in 2007 were obtained per type of fuel. With data provided by the Brazilian Department of Transit (DENATRAN) concerning the number of diesel vehicles in the last five years in Brazil, the total CO₂ emissions and the percentage that they would decrease in the case of use of pure biodiesel, B100, or several mixtures, B2, B5 and B20, were calculated. Estimates of CO₂ emissions for a future scenario considering the mixtures B5 and B20 are also included in this article.