Surrogate Blends Research Articles

A reduced kinetic model for the oxidation of supercritical ethanol/gasoline surrogate blends

A reduced kinetic model for the oxidation of supercritical ethanol/gasoline surrogate blends

Validation of octane hyperboosting phenomenon in prenol and structurally related olefinic alcohols

Hyperboosting is a recently discovered phenomenon in which the research octane number (RON) of a blend is higher than both the neat blendstock and the neat fuel it was blended into. RON is a measure of a fuel’s resistance to knock, and knock is a cause of engine inefficiency. Blends which exhibit hyperboosting are blends in which an overall improvement in engine efficiency may be expected. The first discovery of hyperboosting came from blending experiments in which prenol was blended into several different base fuels. Here, ignition delay time (IDT) measurements taken using a commercially available constant volume combustion chamber called the Advanced Fuel Ignition Delay Analyzer (AFIDA) are presented. The data show that some prenol blends have longer IDTs (lower reactivity) than either neat prenol or the base fuel, providing further evidence of hyperboosting. Additionally, more blending data is presented in which the base fuel is varied, which allows for a better understanding of hyperboosting sensitivity to chemical classes. The data indicate that aromatics may inhibit, and branched alkanes may enhance the magnitude of hyperboosting observed. Enthalpy of vaporization estimates are also given for several molecules which are blended into a 4-component surrogate. These estimates are derived from Equation of State simulations and reveal that there is no observable correlation between hyperboosting and enthalpy of vaporization. Blending data for molecules which share structural similarities with prenol are also presented. Structure property relationships are suggested, in which the double bond motif of prenol seems to play an important role in hyperboosting. This may help to understand hyperboosting and its underlying mechanism. Lastly, blending curves of surrogate blends with prenol experienced hyperboosting under lean (Homogeneous Charged Compression Ignition-HCCI) operating conditions, which validates that hyperboosting is not an artifact of the octane test methods, but inherent to the properties of prenol.

Flow virometry for water-quality assessment: protocol optimization for a model virus and automation of data analysis

Flow virometry (FVM) can support advanced water treatment and reuse by delivering near-real-time information about viral water quality. But maximizing the potential of FVM in water treatment and reuse applications requires protocols to facilitate data validation and interlaboratory comparison—as well as approaches to protocol design to extend the suite of viruses that FVM can feasibly and efficiently monitor. We address these needs herein. First, we optimize a sample-preparation protocol for a model virus using a fractional factorial experimental design. The final protocol for FVM-based detection of T4—an environmentally relevant viral surrogate—blends and improves on existing protocols developed using a traditional pipeline-style optimization approach. Second, we test whether density-based clustering can aid and improve analysis of viral surrogates in complex matrices relative to manual gating. We compare manual gating with results obtained through algorithmic clustering: specifically, by leveraging the OPTICS (Ordering Points to Identify Cluster Structure) ordering algorithm. We demonstrate that OPTICS-assisted clustering can work as well or better than manual gating of FVM data, and can identify features in FVM data difficult to detect through manual gating. We demonstrate our combined sample-preparation and automated data-analysis pipeline on wastewater samples augmented with viral surrogates. We recommend use of this protocol to validate instrument performance prior to and alongside application of FVM on environmental samples. Adoption of a consistent, optimized analytical approach that (i) centers on a widely available, easy-to-use viral target, and (ii) includes automated data analysis will bolster confidence in FVM for microbial water-quality monitoring.

СПОСОБ ПОЛУЧЕНИЯ ОПТИМАЛЬНОГО СОСТАВА СМЕСЕВОГО ЭКОЛОГИЧЕСКИ ЧИСТОГО ДИЗЕЛЬНОГО ТОПЛИВА

The issue of improving the quality and finding alternative resources in the fuel sector leads to the use of environmentally friendly materials with improved characteristics. The article presents a calculation method, the purpose of which is to determine the engine-optimal composition of environmentally friendly mixed diesel fuel with improved ecological characteristics consisting of three main components: hydrotreated diesel fuel, biodiesel obtained by transesterification and biodiesel obtained by hydrotreating of vegetable oils. During the work, the individual characteristics of the components were determined. Those characteristics are required to be in compliance with the requirements for diesel fuels (density, viscosity, lubricating properties, sulfur content, cetane number). The qualitative and quantitative composition was investigated by chromatographymass spectrometry method. Classes of hydrocarbons and their specific representatives in each of the components were determined. Using the results of the previous stages, the calculation of the optimal composition of the components was performed using the Ansys Reaction Workbench software. The algorithm for entering the necessary initial data for working with the program, utility-aided calculation of the coefficients of dependencies of individual and thermodynamic properties of substances used in calculations were considered, thereby complementing the basic library of chemical compounds for Ansys Surrogate Blend Optimizer. As a result, a group composition for hydrocarbons was obtained that meets the requirements of the standards for further calculation of the optimal component composition. The usage of mixed diesel fuel that meets GOST R 52368-2005 "EURO diesel fuel Specifications" will not only improve the performance characteristics required in modern diesel vehicles, but also meet the standards of environmental parameters when using it. The appliance of mathematical models for calculating the optimal composition of fuels makes it possible to predict the properties of mixed compositions without experimental determination of the properties and without spending additional resources.

Particulate Matter Emissions in Gasoline Direct-Injection Spark-Ignition Engines: Sources, Fuel Dependency, and Quantities

This study investigates sources of particulate matter (PM) from a direct-injected spark-ignition (DISI) engine, all of which are likely the result of poor mixture formation, although through varying mechanisms. Nine unique gasoline formulations, including both oxygenated and non-oxygenated fuels, with varying distillation curves and concentrations of different hydrocarbon classes were employed to investigate the effect of fuel on soot formation. The engine experiments were further supported by reacting and non-reacting experiments in a spray-chamber.The metal-engine experimental results indicated that engine-out PM emissions of the nine fuels generally conforms to their sooting tendency, here quantified by Particulate Matter Index (PMI). Discrepancies with the engine-out PM emissions and PMI were observed under transient operating condition, which is not reflective of the test conditions used to formulate the PMI. A diisobutylene surrogate blend and a high-olefin full-boiling range fuel were investigated further in the optically-accessible engine, showing soot generation from different sources. These differences came from the variation in their spray characteristics, as confirmed in the non-reactive spray-chamber experiments.While the earlier tests were conducted with a fouled injector, the injector was later cleaned and fuels were tested in the optical engine. High olefin fuel and diisobutylene blend showed significantly lower soot emissions with clean injector. E30 fuel exhibited spray impingement and subsequent diffusive combustion, known as pool fire, on the piston top characterized by a yellow flame due to soot luminosity. A final round of experiments in the spray-chamber mimic this pool fire mechanism. A stoichiometric flame was initiated after a spray has impinged on a wall and formed a film. Results showed a large time delay between the flame passing over the fuel film and the formation of soot mass. The slow soot formation via pyrolysis in spray-chamber suggest that pyrolysis may not be a dominating soot-production pathway in SI engines, even for conditions with significant wall wetting. The findings of this study highlight the many considerations which influence the effective design of a combustion system when the minimization of PM emissions is a goal, and the ways in which fuel formulation can change soot-production pathways in DISI engines.

Design and evaluation of surrogate mixtures for diesel based on the isolated droplet configuration

The development of simplified surrogate mixtures able to replicate combustion-related behaviors of chemically complex fuels is essential for their simulation with computational tools, a key step towards the design of high-efficiency and low-emission combustion applications. This work proposes to use the isolated droplet configuration as a benchmark to formulate and validate surrogates that capture the vaporization and soot production characteristics of a first-fill diesel and a diesel-biodiesel mixture. To that end, droplet vaporization experiments and a multicomponent model were coupled to produce blends matching the evaporation behavior, whereas the soot tendency was incorporated through tests at the ASTM D1322 smoke point lamp and the Oxygen Extended Sooting Index (OESI). The so-obtained surrogate blends were subsequently validated for both characteristics. Their evaporation curves proved to match remarkably well those obtained for the target fuels, with noticeable improvements when increasing the number of compounds in the mixture. As for the sooting behavior, the proposed blends achieved a good emulation in terms of the design parameter (OESI), confirming the validity of the proposed methodology. On the other hand, an additional and independent validation of the sooting propensity through the quantification of the mass of soot produced by isolated droplets under a high-temperature and reducing atmosphere revealed significantly higher soot yields for the surrogates when compared to the target fuels. These results highlight the relevance of the configuration used when designing and validating surrogates, since the same blends can provide substantial differences when evaluated through different sooting indices.

Synthesis of Surrogate Blends Corresponding to Petroleum Middle Distillates, Oxidative and Extractive Desulfurization Using Imidazole Ionic Liquids

Surrogate fuels are composed of a few pure components, mixed together in order to imitate a real fuel’s characteristics regarding its combustion and emission. In this study, four surrogate feeds were synthesized, corresponding to petroleum middle distillates. The desulfurization of the surrogate blends was performed using the hydrogen peroxide–acetic acid oxidative system. Consequently, extractive desulfurization was carried out using imidazolium-based ionic liquids, namely 1-butyl-3-methylimidazolium bromide [BMIM][Br] and 1-butyl-3-methylimidazolium hydrogen sulfate [BMIM][HSO4], in a multiple extraction cycle procedure. Both ionic liquids were synthesized and characterized with spectroscopic techniques. The influence of the extraction temperature process was studied. In each extraction cycle, the sulfur concentration and the physical properties of the surrogate extraction products were estimated. The used ionic liquids were regenerated with a reasonably effective method. The synthesized and recycled ionic liquids showed high desulfurization efficiency, while [BMIM][Br] prevailed. Additionally, extractive desulfurization in oxidized surrogate LCO using ionic liquids is comparable with that using acetonitrile, since it has an advantage in terms of mass yield.

Pyrolysis and oxidation of a light naphtha fuel and its surrogate blend

An experimental and kinetic study on pyrolysis and oxidation of a real light naphtha fuel and its surrogate blend were conducted. Based on the chemical functional group method, a three-component surrogate blend for the target naphtha was formulated, which contains 64.2 mol% iso-pentane, 21.0 mol% n-hexane, and 14.8 mol% methylcyclopentane. The pyrolysis and oxidation characteristics of the target naphtha fuel and the formulated surrogate were compared using a jet-stirred reactor (JSR) at the equivalence ratios of 0.5, 1.0, 2.0 and ∞, across the temperature range from 700 to 1100 K, and at atmospheric pressure. Mole fractions of the three components, oxygen, hydrogen, CO, CO2, and C1-C4 hydrocarbons were measured by gas chromatograph. Similar global reactivities between the two test fuels were observed in both pyrolysis and oxidation experiments. In addition, a detailed chemical kinetic model was constructed and validated against the species mole fraction profiles measured in JSR experiments. The present model can provide reasonable prediction of the experimental measurements of the species mole fractions in pyrolysis and oxidation of the surrogate blend. Uncertainty-weighted sensitivity analysis indicates that the model prediction of the consumption of the three components of the surrogate blend in pyrolysis are dominated by the rate constants for H-abstraction reactions of isopentane, n-hexane, methylcyclopentane and propene by H atom and methyl radical. The model predictions of the oxidation reactivity of the surrogate blend mainly depend on H-abstraction reactions from the three surrogate components by HO2 radical at 800 K, while the H-abstraction reactions from aldehyde and alkene intermediates become more significant at 950 K.

Pyrolysis of 2-methylfuran/jet fuel surrogate blends: An experimental and kinetic modeling study

Owing to significant advantages over traditional biofuels, 2-methylfuran (MF) has arisen extensive interest as next generation biofuels. Atmospheric pressure pyrolysis of a 1:1 blend of MF with a three-component (3C) surrogate jet fuel was conducted in a flow tube using synchrotronphotoionization and molecular beam mass spectrometry techniques within a temperature range of 898–1223 K. Therein, the 3C surrogate fuel consists of 66.2% n-dodecane (NC12H26), 18.0% 1,3,5-trimethylcyclohexane (T135MCH) and 15.8% n-propylbenzene (NPB, A1C3H7). The detailed kinetic model including 579 species and 3474 reactions was developed via validating against both measured and literature data with reasonable agreement. MF exhibits no obvious influence on the 3C components pyrolysis. However, 3C mixtures play an important roles in MF decomposition: lower initial temperature and different decomposition pathways. In the meantime, n-propylbenzene (NPB) pyrolysis curve in 3C and 3C+MF significantly transfers to low temperature zone after 1000 K in contrast to pure NPB, while smaller change was found in the decomposition curve of n-dodecane. Compared with 3C pyrolysis, 3C+MF blends have less formation of aromatic species and light hydrocarbons except for vinylacetylene (C4H4) and acetylene (C2H2). Allyl radical (C3H3) has significant roles in benzene ring formation. The combination of allyl radical with propargyl radical producing benzene and H radical (aC3H5 + C3H3 = A1 + 2H) has the highest contribution to the benzene formation in both 3C and 3C+MF. Moreover, most of naphthalene (A2) formation is also related to C3H3 radical via reaction: A1CH2 + C3H3 = A2 + H, rather than via HACA (hydrogen abstraction carbon addition) reaction. Interaction of fuel blends was mainly presented through the common and important sensitive reactions which are much to do with CH3 and H radicals. The overview of product distribution was investigated by providing comparisons of carbon conversion rates during the pyrolysis of 3C and 3C+MF. These results will be helpful to better understand the pyrolysis properties of MF/jet fuel surrogate blends and could contribute to developing new generation biofuels for aviation.

Rapid prediction of fuel research octane number and octane sensitivity using the AFIDA constant-volume combustion chamber

Current research octane number (RON) and motor octane number (MON) gasoline performance characterization techniques use dated, complex engine testing methodology and limit researchers’ ability to easily characterize small volumes of experimental fuels. A novel methodology is presented that correlates measured ignition delay (ID) time to RON in an Advanced Fuel Ignition Delay Analyzer (AFIDA) constant-volume combustion chamber device at a single pressure/temperature condition, with an r2 of 0.99 and standard error (SE) of 1.0. The correlation of the slope of the ID time between two additional temperature points to octane sensitivity (S) produces an r2 of 0.97 and SE of 0.69; however, fuels with S > 12 are indistinguishable. These results are based on methodology calibration using 31 primary and toluene reference fuels containing 0%─40% ethanol with RON values ranging from 85 to 113. Validation of these methods using a 102-sample fuel matrix spanning an array of base fuels and additive chemistry designed to test the robust applicability of the method, along with pump gasoline and high-octane surrogate blend samples, demonstrates an r2 of 0.94 and SE of 1.3 for the RON correlation over all samples, whereas the equivalent S correlation produces an r2 of 0.78 and SE of 1.2 by excluding two additives, 3-pentanone and diisobutylene, which displayed poor S correlation results. This novel AFIDA analysis method can be performed in 1 h and with 40 mL of fuel, offering significant improvements in time and volume requirements over traditional techniques.

Experimental Characterization of Flame Structure and Soot Volume Fraction of Premixed Kerosene Jet A-1 and Surrogate Flames

Modeling the chemical reactions and soot processes in kerosene flames is important to support the design of future generations of low-emission aircraft engines. To develop and validate these models, detailed experimental data from model flames with well-defined boundary conditions are needed. Currently, only few data from experiments with real aircraft engine fuels are available. This paper presents measurements of temperature, species and soot volume fraction profiles in premixed, flat flames using Jet A-1 kerosene and a two-component surrogate blend. Measurements were performed using a combination of TDLAS, GC and laser extinction. The results show that the flame structure in terms of temperature and species profiles of the kerosene and surrogate flames are very similar but differ greatly in the resulting soot volume fractions. Furthermore, the study shows that the available chemical mechanisms can correctly predict the temperature profiles of the flames but show significant differences from the experimentally observed species profiles. The differences in the sooting tendency of the kerosene and the surrogate are further investigated using detailed chemical mechanisms.

A new approach for producing mid-ethanol fuels E30 based on low-octane hydrocarbon surrogate blends

Development of mid-ethanol fuel with an ethyl alcohol content of 20–40% (E30 fuel), which is devoid of phase instability problems and can potentially be applied to automotive technology without modifications, and it is a promising area. One of the promising ways is to develop high-octane Е30 fuel based on cheap low-octane fractions, which will significantly improve the economic parameters of fuel production. This research paper investigates the influence of bioethanol at a concentration of 5–85 wt% on the change in an antiknock performance of low-octane hydrocarbon fractions, involving heavy hydrocracked naphtha and straight run hydrotreated naphtha, as well as low-octane surrogate blends of individual hydrocarbons of various groups, containing n-heptane, isooctane, toluene, p-xylene, cyclohexane, n-pentane, n-hexane, and isooctene. The results indicated that the antiknock performance of bioethanol in low-octane hydrocarbon fractions was increased in the series: olefins <naphthenes <aromatics <paraffins <isoparaffins according to the research method, where it was reached to the maximum in a concentration of 10–30 wt%. What's more, the boundary values of the antiknock performance of bioethanol at a concentration of 20–40 wt% in low-octane hydrocarbon fractions, expressed in octane ethanol blending numbers were investigated as: RONBL = 130–156, MONBL = 108–133.

Preliminary study on the influence of Octane Sensitivity on knock statistics in a GDI engine

In the 3D-CFD practice, actual gasoline fuels are usually replaced by surrogate blends composed of Iso-Octane, n-Heptane and Toluene (Toluene Reference Fuels, TRFs). In this work, the impact of surrogate formulation on the probability of end-gas auto-ignition is investigated in a single cylinder engine. CFD simulations are run on equal charge stratification to discern the effect of fuel reactivity from that of evaporation and mixing. Blends are formulated using an internal methodology, coupled with a proprietary method to predict knock statistical occurrence within a RANS framework. Chemical kinetics calculations of Ignition delay times are performed in a 0D constant pressure reactor using a mechanism for gasoline surrogates, proposed by the Clean Combustion Research Center of King Abdullah University of Science and Technology (KAUST), consisting of 2406 species and 9633 reactions. Surrogates mimic a commercial European gasoline (ULG95). Five different formulations are presented. Three are characterised by equal RON (95) with progressively decreasing Octane Sensitivity S. The fourth and the fifth have a sensitivity of 10 but with lower RON (92.5 and 90). The combinations allow the reader to separate the effects of octane sensitivity from those of RON quality of the tested fuels. Applying the different surrogates, changes in each of autoignition phasing, magnitude and statistical probability are investigated. Results confirm the dependency of knock occurrence on the Octane Sensitivity, as well as the need to include engine-specific and operation-specific characteristics in the analysis of knock. The Octane Index (OI) formulation developed by Kalghatgi is discussed.

Assessment of the Oxidative Desulfurization of Middle Distillate Surrogate Fuels with Spectroscopic Techniques.

The oxidative desulfurization of five (5) model sulfur compounds and eleven (11) surrogate blends was investigated using the hydrogen peroxide (H2O2)-acetic acid (CH3COOH) system. Consequently, extractive desulfurization was carried out using conventional solvents. The model sulfur compounds, as well as the solvent, are present in petroleum middle distillates. The selection of the compounds was made so that they represent various kinds of sulfur compounds. The goal of this study was the implementation of a simple and economical oxidative and extractive system for the desulfurization of surrogate mixtures with an intermediate sulfur concentration 1% w/w, at the mild temperature of 70°C, and without the use of supplementary and assisting methods such as heterogeneous catalysis or ultrasound irradiation. The sulfur content was estimated using X-ray fluorescence. The progress of the oxidation reaction was monitored using liquid FT-IR. The solid sediments of the oxidation procedure were identified with solid-state FT-IR and 1H NMR spectroscopy.

Combustion of methylcyclohexane at elevated temperatures to investigate burning velocity for surrogate fuel development

To overcome the complexity associated with the development of detailed kinetic models for real transportation fuels, surrogate fuel models offer an excellent alternative. The present study reports laminar burning velocity (LBV) measurements of methylcyclohexane (MCH) + air mixtures for mixture temperatures up to 610 K using externally heated diverging channel method (EHDC) method at 1 atm pressure. MCH is a commonly used surrogate blend for aviation fuels, gasoline, and diesel, whose kinetic model is simpler to develop. The measurement of laminar burning velocity forms the basis of kinetic model development for such surrogate fuels. The present work reports the measured LBV values for an equivalence ratio range, φ = 0.7–1.4, and their comparison with available experimental data and detailed kinetic model predictions for a mixture temperature range, 353–610 K. Temperature exponent, α is derived using the power-law correlation and good consistency with kinetic model predictions is observed up to 500 K mixture temperatures. At 610 K mixture temperature, an overprediction of ≈12% at φ = 1.05 is observed with JeTSurF 2.0 (2010) model and 27% overprediction with the kinetic model of PoliMi (2014) φ = 1.1. Overall, the reported LBV measurements show slightly better match with the JeTSurF 2.0 (2010) kinetic model than the Wang (2014) kinetic model. Reaction pathway diagrams are drawn to highlight the importance of C2H4 and C2H3 radicals for an increase in the overall reaction rate at 610 K.

Flash boiling combustion of isomeric butanol and gasoline surrogate blends using constant volume spray chamber and GDI optical engine

Flash boiling spray has been regarded as a promising fuel injection technology. Many investigations have been focused on spray physics and mechanisms of flash boiling spray, but information on flash boiling of alcohols in GDI engines is very limited. In this paper, the spray characteristics, flame propagation, combustion analysis, and PN emissions of butanol isomers under flash boiling spray have been studied. A constant volume chamber with a high-speed camera used to investigate the flash boiling spray of butanol isomers and gasoline surrogate blends. The flash boiling spray was tested at 180 °C and compared to subcooled spray at 25 °C. The tested gasoline surrogates are primary reference fuel (PRF) and toluene primary reference fuel (TPRF). The flash boiling leads to the collapse of the spray six plumes into a single extended spray plume with longer spray penetration compared to subcooled injection. The spray study then extended to study the effects of flash boiling injection on flame development and PN emissions of the GDI optical engine. The results reveal that flash boiling injection leads to lower apparent flame speed and flame area compared to subcooled injection due to the lean-like burn condition, and yellow flame spots are diminished. The peak in-cylinder pressure and apparent heat release rate are reduced with longer ignition delay when the flash boiling injection is applied. The flame lasted longer under flash boiling conditions with improved late combustion phase, which results in higher heat released. The PN emissions reduced with flash boiling spray compared to subcooled conditions.

On the combustion and sooting behavior of standard and hydro-treated jet fuels: An experimental and modeling study on the compositional effects

In a context of growing level of environmental awareness, emission from aviation are the subject of increasing scrutiny. This situation poses important challenges because, due to safety, practical and economic factors, aero-transportation technologies are not likely to undergo rapid paradigm shifts. An area where important innovations are being introduced is fuel technology: fuels from alternative processes, potentially from renewable sources, offer the opportunity of limiting the carbon footprint of transportation, moreover, a better control on fuel quality can contribute to reducing emissions.Hydro-treating of oil based fuels can reduce their sulfur and aromatic content promoting a cleaner combustion. In order to better understand the impact of hydro-treating on emissions of PAHs and soot from jet fuels, new speciation data covering oxidation intermediates and soot precursors were measured in a flow reactor for a standard jet fuel and its hydro-treated counterpart. Using a detailed kinetic mechanism and complex surrogate blends mimicking the composition of the real fuels, the speciation data from the flow reactor were simulated. Additionally, soot formation trends were calculated and compared with previously published data. Using the kinetic model, which is based on mechanistic principles, it was possible to separate the relative contribution of different processes and, for the fuel blends of interest, the role played by specific components in the PAHs and soot formation. The results obtained provide useful information towards more effective fuel formulation strategies and fuel blends modeling.

Evaluation of Oxidative Desulfurization and Solvent Extraction of Model Sulfur Compounds, Present in Petroleum Middle Distillates, with Infrared and Nuclear Magnetic Resonance Spectroscopy

Oxidative desulfurization has attracted considerable attention, since it can remove the refractory sulfur compounds under relatively mild conditions. The types of the sulfur compounds and the composition of the distillate affect the efficiency of the method. The composition of a distillate determines its properties and its performance characteristics, but it is too complex to model it exactly. In the present study, simple surrogate blends of eight model sulfur compounds in the range of petroleum middle distillates were created and oxidized, using the hydrogen peroxide-acetic acid system, at reaction temperatures of 50 and 70 °C. The total sulfur content was constant at 1% w/w. The organic phase of the oxidized products was extracted with acetonitrile and methanol. The sulfur content was determined using X-ray fluorescence and the mass yield was calculated. Liquid phase infrared spectra were obtained during the oxidation and the extractive desulfurization processes. The solid sediments that were precipitated in specific cases were identified using solid-state infrared and proton nuclear magnetic resonance. The influence of temperature upon the formation of sulfoxides or sulfones during the oxidative desulfurization of the sulfur compounds was studied in detail. The oxidation temperature of 70 °C was shown to be suitable for the completion of the oxidative desulfurization while both extraction solvents were efficient in the removal of the sulfur compounds.

Compositional Effects on Sooting Tendencies of Diesel Surrogate Fuels with Four Components

Systematic investigations of the effects of fuel compositions on sooting tendencies were performed in co-flow methane/air diffusion flames doped with different surrogate blends. Test surrogate fuel...

High-pressure ignition delay time measurements of a four-component gasoline surrogate and its high-level blends with ethanol and methyl acetate

Ignition delay times of a gasoline surrogate (iso-octane/toluene/n-heptane/1-hexene at 55/25/15/5% by liquid volume, developed in McCormick et al. 2017) with high-level bioblendstock-gasoline surrogate blends (50% and 85% biofuel by liquid volume of each ethanol and methyl acetate) were collected behind reflected shock waves. Post-reflected-shock temperatures ranged from 968 to 1361 K at pressures of about 4, 10, 25, and 50 atm. Data were collected for real fuel–air mixtures at fuel lean and stoichiometric conditions (φ = 0.5, 1.0) with focus on the more-practical, fuel-lean conditions. Ignition delay times were measured from OH* chemiluminescence around 307 nm using an endwall diagnostic. The RON and MON of the surrogate were 90.3 and 84.7, respectively. Ethanol was chosen due to its wide use in flex-fuel vehicles and availability, while also providing an increased octane rating. Methyl acetate was chosen for its especially high octane rating to investigate the effect of an extreme case. To validate the gasoline surrogate, the data are compared to real gasoline (RD387) and several gasoline surrogate experiments from the literature. Using the wide range of pressures studied, the gasoline surrogate’s pressure dependence was quantified to account for test-to-test variations using regression analysis. Similarly, a global correlation for gasoline and its surrogates was developed using all available data from the literature. Two modern chemical kinetics models targeting gasoline and its surrogates are compared to the ignition delay time measurements. These new high-pressure, high-bioblendstock concentration tests provide required chemical kinetic data for optimizing fuel and engine design.