Diesel-type Fuels Research Articles

Autoignition of sustainable fuels under dual operation with H2-carriers in a constant volume combustion chamber

The expected increase in the use of environmentally friendly liquid fuels in medium and heavy-duty compression ignition engines (for both off-road and transport applications), together with the well-documented benefits of hydrogen-carriers to decrease energy dependence and to achieve a neutral-carbon economy (internal combustion engines highly contributing to the global CO2 emissions), have motivated this work. The autoignition characteristics of different alternative diesel-type fuels (hydrotreated vegetable oil, advanced biodiesel and blends of conventional diesel fuel with polyoxymethylene dimethyl ether and 1-butanol) under dual-fuel operation with H2, NH3, and CH4 were studied in a constant volume combustion chamber at 535 and 600 °C. The high reactivity fuel was replaced by the gaseous fuel up to 40 % by energy. The main ignition delay time was significantly affected not only by the type of low reactivity fuel, with ammonia considerably retarding autoignition, but also by the nature of the liquid fuel, biodiesel being the less sensitive to the presence of the H2-carrier fuel. Results also proved that the higher the reactivity of the diesel-type fuel (quantified through the cetane number), the lower the influence of the gaseous fuel on the autoignition time.

Experimental study of influence of Liquefied Petroleum Gas addition in Hydrotreated Vegetable Oil fuel on ignition delay, flame lift off length and soot emission under diesel-like conditions

The fundamental behaviour on ignition and combustion characteristics of blends of Hydrotreated Vegetable Oil and Liquid Petroleum Gas was investigated in a constant high pressure, high temperature combustion chamber, using a prototype lab-scale injection system adapted from a conventional common-rail system to conduct the injection events, ensuring that fuel was liquid at any point of the injection system and avoiding the formation of fuel vapour bubbles that could alter the injected fuel behaviour.The ignition delay, flame lift-off length and the soot formation were studied by means of high-speed imaging techniques, for different operating conditions. The aim of the work is to characterize the effect of Hydrotreated Vegetable Oil-Liquid Petroleum Gas blend ratios on the previously mentioned parameters.Experimental results show that the behaviour of the fuel blends follow the expected trends of conventional diesel type fuels when varying ambient temperature, density and injection pressure. Hydrotreated Vegetable Oil, being the highest reactivity fraction, controls auto ignition of the blend. However, Liquid Petroleum Gas acts as combustion inhibitor increasing both ignition delay and lift-off length as its ratio in the blend increases. As a consequence, the differences observed in terms of flame radiation suggest that increasing Liquid Petroleum Gas fraction reduces soot formation as it promotes a higher air/mixture.

Synthesis and Characterization of New Solketal Alkylesters Usable as Diesel Biobased Fuel Additives

There are described experimental studies on the esterification of solketal, (the cyclic acetal produced from glycerol and acetone reaction), by transesterification reactions of the -OH group with methyl esters of C3 -C10aliphatic acids (propionic, pentanoic, hexanoic, octanoic and decanoic). The goal was to obtain better additives for diesel and biodiesel fuels, as compared to solketal. The measured physical properties (especially density, viscosity and water solubility) of the synthesized solketal esters, closer to the corresponding ones for the diesel and biodiesel fuels, permit to suppose that these new compounds should be better additives for diesel type fuels, as compared with solketal. For three of these esters there were studied the liquid-vapor equilibrium at different temperatures, determining also the Antoine equation coefficients for the calculation of vapor pressure.

Characterization of CoCu- and CoMn-Based Catalysts for the Fischer–Tropsch Reaction Toward Chain-Lengthened Oxygenates

The need for a sustainable energy supply in the face of depleting oil reserves has reignited the importance of Fischer–Tropsch (FT) synthesis technology. Presently, the FT process is practiced at the industrial scale to predominately produce synthetic diesel-type fuels and lubricants. More recently, the possibility of hydrogenating CO toward oxygenates, and not just hydrocarbons, has been explored. We have developed a series of CoCuMn and CoMnK catalysts prepared via the oxalate co-precipitation route that are capable of forming oxygenates with desirable selectivity. Upon H2-assisted thermal decomposition of the resultant mixed metal Co1Cu1Mn1 oxalates, catalysts naturally exhibited a cobalt core–copper shell configuration with Mn5O8 dispersed throughout the catalyst nanoparticle as determined via Atom Probe Tomography (APT). We suggest structural changes are induced by the CO and H2 reactants to form the catalytically active phase under real-time reaction conditions as demonstrated by corroborative Density Functional Theory calculations and experimental evidence. APT studies also show that a Co4Mn1K0.1 catalyst post reaction contained a cobalt carbide phase as determined from a Co/C ratio of 2/1. Manganese and potassium were found only in the outermost part of the particle. Both catalysts were found to contain the presence of a Mn5O8 oxidic phase before and post reaction which we attribute to the high activity toward oxygenates of these two catalysts.

Rozdíly v reologickém profilu motorové nafty a bionafty B30

Biodiesel represents a promising alternative to regular fossil diesel. Fuel viscosity markedly influences injection, spraying and combustion, viscosity is thus critical factor to be evaluated and monitored. This work is focused on quantifying the differences in temperature dependent kinematic viscosity regular diesel fuel and B30 biodiesel fuel. The samples were assumed to be Newtonian fluids. Vis­co­si­ty was measured on a digital rotary viscometer in a range of 0 to 80 °C. More significant difference between minimum and maximum values was found in case of diesel fuel in comparison with biodiesel fuel. Temperature dependence of both fuels was modeled using several mathematical models – polynomial, power and Gaussian equation. The Gaussian fit offers the best match between experimental and computed data. Description of viscosity behavior of fuels is critically important, e.g. when considering or calculating running efficiency and performance of combustion engines. The models proposed in this work may be used as a tool for precise prediction of rheological behavior of diesel-type fuels.

Analysis of Fuel Options for SOFC-Based Power Systems in Undersea Vehicles

In a departure from NUWCDIVNPT's original focus on diesel-type (logistics) fuels, methane is looking more attractive for Unmanned Undersea Vehicle (UUV) applications, at least for first generation SOFC-powered UUVs. Even though the energy density for methane is roughly half that of diesel-type fuel, the savings in oxygen and carbon dioxide sorbent storage result in system energy metrics similar to those for S-8-based systems. In addition, the fuel processor control and system start-up can be greatly facilitated by using methane instead of a liquid hydrocarbon fuel. Switching to a methane fuel feed has the following advantages: • High Hydrogen-to-Carbon ratio (this lowers O2 and CO2 sorbent storage requirements) • Facilitates steam reforming versus diesel-type fuels • Greater ease of start-up and system power transient control • Risk mitigation for potential SOFC coking • Low boiling point, thus avoiding logistics of vaporizing diesel-type fuels and producing carbon residue.

Converting Waste Plastic to Hydrocarbon Fuel Materials

ABSTRACT The increased demand and high price for energy sources are driving efforts to convert organic compounds into useful hydrocarbon fuels. Although much of this work has focused on biomass, there are strong benefits to deriving fuels from waste plastic material. Waste plastic is abundant and its disposal creates large problems for the environment. Plastic does not break down in landfills, is not easily recycled and degrades in quality during the recycling process, and can produce waste ash, heavy metals, and potentially harmful gas emissions if incinerated at high temperatures. However, chemical processes that can be used to convert plastics into hydrocarbon fuels have unlimited applications in residential and industrial heating, transportation, and electricity generation. These chemical processes are used to break down the long carbon chains found in plastic into the shorter chains found in gasoline or diesel-type fuels. Natural State Research (NSR) has invented a simple and economically viable process to decompose the hydrocarbon polymers of waste plastic into the shorter chain hydrocarbons of liquid fuel (patent pending). The method and principal of the process/production will be discussed.

Effect of Gas-to-Liquid Diesel Fuels on Combustion Characteristics, Engine Emissions, and Exhaust Gas Fuel Reforming. Comparative Study

New diesel-type fuels such as biodiesels and gas-to-liquid (GTL) fuel have been developed in order to aid vehicle manufacturers in achieving forthcoming emission regulations, by improving engine out emissions and exhaust gas after-treatment performance. Furthermore, synthetic fuels are virtually free of sulfur and aromatic hydrocarbons and can improve the performance and durability of the catalytic fuel reformers that are designed to provide H2 to fuel cells, internal combustion (IC) engines, and after-treatments. Combustion and exhaust-gas reforming experiments with GTL and ultralow sulfur diesel (ULSD) were run under several engine and reformer operating regimes. Using a single cylinder bench engine, the combustion of GTL fuel (and blends with conventional diesel fuel) was found to reduce NOx emissions substantially and improve engine thermal efficiency but led to an increase in smoke for the default injection timing in the experiment. However, by optimizing the injection timing in a GTL-fueled engine, the harmful emissions of NOx and smoke were both reduced simultaneously while still giving improvements in engine thermal efficiency. In general, it was found that the NOx/particulates tradeoff curve shifted to lower emissions for GTL fuel and GTL fuel blends. During exhaust-gas reforming, the use of GTL fuel was found to increase fuel conversion, while producing more hydrogen and less methane.

CHARACTERISTICS OF HOMOGENEOUS CHARGE COMPRESSION IGNITION (HCCI) COMBUSTION AND EMISSIONS OF n-HEPTANE

ABSTRACT This paper reports the outcome from a systematic investigation carried out on HCCI (Homogeneous Charge Compression Ignition) combustion of a diesel type fuel. The n-heptane was chosen in this study to study the HCCI combustion characteristics of diesel engines with premixed charge by port fuel injection. Measurements were carried out in a single-cylinder, 4-stroke and variable compression ratio engine. Premixed n-heptane/air/EGR mixture was introduced into the cylinder by a port fuel injector and an external EGR system. The operating regions with regard to Air/Fuel ratio (A/F) and EGR rate were established for different compression ratios and intake temperatures. The effects of compression ratios, intake temperatures, A/F and EGR rates on knock limit, auto-ignition timing, combustion rate, IMEP and engine-out emissions, such as NOx, CO, and unburned HC, were analysed. The results have shown HCCI combustion of n-heptane could be implemented without intake charge heating with a typical diesel engine compression ratio. The attainable HCCI operating region was mainly limited by the knock limit, misfire, and low IMEP respectively. Higher intake temperature or compression ratio could extend the misfire limit of the HCCI operation at low load area but they would reduce the maximum IMEP limit at higher load conditions. Compared with conventional diesel combustion, HCCI combustion with diesel type fuels would lead to extremely low NOx emissions (less than 5 ppm) and smoke free exhaust, but would produce higher HC and CO emissions. An increase in intake temperature or compression ratio helped to reduce HC and CO emissions.

EFFECT OF RECYCLED BURNED GASES ON HOMOGENEOUS CHARGE COMPRESSION IGNITION COMBUSTION

ABSTRACT Homogeneous Charge Compression Ignition (HCCI) also known as Controlled Auto-Ignition (CAI) combustion, has recently emerged as a viable alternative combustion process to the conventional spark ignition (SI) gasoline and compression ignition (CI) Diesel engines, due to its potential for extremely low emissions and good fuel economy. One of the most important means of achieving and controlling HCCI combustion is to use recycle burned gases (EGR). In order to understand better the effects of recycled burned gases on such combustion process, detailed analytical studies were performed. Since HCCI combustion is a process dominated by chemical kinetics of the fuel-air mixture, an engine simulation model with detailed chemical kinetics has been developed and applied to a four-stroke gasoline engine fuelled with isooctane. After calibration and validation, the engine simulation mode was used to investigate the effects of EGR on HCCI combustion in a four-stroke gasoline engine. The characteristics of HCCI combustion investigated include the autoignition timing, the partial burning and knocking combustion, and NO emission. The heat capacity, dilution, chemical, and charge heating effects on the HCCI combustion process were studied individually by means of a series of analytical studies. When isothermal EGR is used, such as in HCCI combustion with diesel type fuels, the heat capacity has the largest effect on extending the combustion duration and slowing down the rate of the combustion. The larger heat capacity of EGR gases tends to retard the start of autoignition. The dilution of oxygen by EGR has little effect on autoignition but it has a similar effect on extending the combustion duration to that of the dilution effect. The dilution effect of EGR on lowing heat release rate is only noticeable at high concentrations. Finally, the chemical effect of CO2 and H2O was found to be negligible. When hot EGR is used in HCCI combustion, the charge heating effect of EGR has much greater effect on ignition timing and some less significant effect on the combustion duration and heat release rate than the other effects.

An investigation of using various diesel-type fuels in homogeneous charge compression ignition engines and their effects on operational and controlling issues

Homogeneous charge compression ignition (HCCI) engines appear to be a future alternative to diesel and spark-ignited engines. The HCCI engine has the potential to deliver high efficiency and very low NOx and particulate matter emissions. There are, however, problems with the control of ignition and heat release range over the entire load and speed range which limits the practical application of this technology. The aim of this paper is to analyse the use of different types of diesel fuels in an HCCI engine and hence to find the most suitable with respect to operational and control issues. The single-zone combustion model with convective heat transfer loss is used to simulate the HCCI engine environment. n-Heptane, dimethyl ether and bio-diesel (methyl butanoate and methyl formate) fuels are investigated. Methyl butanoate and methyl formate represent surrogates of heavy and light bio-diesel fuel respectively. The effects of different engine parameters such as equivalence ratio and engine speed on the ignition timing are investigated. The use of internal exhaust gas recirculation is investigated as a potential strategy for controlling the ignition timing. The results indicate that the use of bio-diesel fuels will result in lower sensitivity of ignition timing to changes in operational parameters and in a better control of the ignition process when compared with the use of n-heptane and dimethyl ether.

Investigating the Effects of Cetane Improvers on Specification Test Requirements and Related Properties of Diesel-Type Fuels

Abstract : The effects of alkyl nitrate-type cetane improvers on Military and Federal specification requirements of diesel-type fuels were investigated. The presence of these alkyl nitrates was found to adversely affect specific test requirements as a result of their thermal instability which initiated oxidation-polymerization reactions. Subsequent evaluations, which necessitated the development of an accelerated screening technique for determining relative thermal stability, indicated that cyclohexyl nitrate exhibited the least resistance towards thermal stability under these static test conditions. In addition, there were indications that under conditions of accelerated storage, the quality of diesel fuel may be altered by the additions of these alkyl nitrates. (Author)