Knock Properties of Oxygenated Blends in Strongly Charged and Variable Compression Ratio Engines

Ling, Zhengyang; Burluka, Alexey; Azimov, Ulugbek

doi:10.4271/2014-01-2608

Cited by 5 publications

(7 citation statements)

References 24 publications

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“…One is that n-butanol can be sourced from renewable bio-energy sources. The blending of oxygenates like n-butanol with gasoline, also enables more complete combustion, potentially leading to reductions in pollutant emissions such as carbon monoxide and soot [5]. Mixtures of other butanol isomers (2-butanol and tert-butanol) blended with TRF mixtures have previously been studied under shock tube conditions [6] demonstrating that at lower temperatures, these butanol isomers lengthened ignition delays of the mixtures, thus acting as octane boosters.…”

Section: Introductionmentioning

confidence: 99%

The influence of n -butanol blending on the ignition delay times of gasoline and its surrogate at high pressures

Agbro

Tomlin

Lawes

et al. 2017

Fuel

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The influence of blending n-butanol at 20% by volume on the ignition delay times for a reference gasoline was studied in a rapid compression machine (RCM) for stoichiometric fuel/air mixtures at 20 bar and 678 K-858 K. Delay times for the blend lay between those of stoichiometric gasoline and stoichiometric n-butanol across the temperature range studied. At lower temperatures, delays for the blend were however, much closer to those of n-butanol than gasoline despite n-butanol being only 20% of the mixture. Under these conditions n-butanol acted as an octane enhancer over and above what might be expected from a simple linear blending law. The ability of a gasoline surrogate, based on a toluene reference fuel (TRF), to capture the main trends of the gasoline/ n-butanol blending behaviour was also tested within the RCM. The 3-component TRF based on a mixture of toluene, n-heptane and iso-octane was able to capture the trends well across the temperature range studied. Simulations of ignition delay times were also performed using a detailed blended nbutanol/TRF mechanism based on the adiabatic core assumption and volume histories from the experimental data. Overall, the model captured the main features of the blending behaviour, although at the lowest temperatures, predicted ignition delays for stoichiometric n-butanol were longer than those observed. A bruteforce local sensitivity analysis was performed to evaluate the main chemical processes driving the ignition behaviour of the TRF, n-butanol and blended fuels. The reactions of fuel + OH dominated the sensitivities at lower temperatures, with H abstraction from nn-butanol and the blend. At higher temperatures the decomposition of H 2 O 2 and reactions of HO 2 and that of formaldehyde with OH became critical, in common with the ignition behaviour of other fuels. Remaining uncertainties in the rates of these key reactions are discussed.

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Section: Introductionmentioning

confidence: 99%

The influence of n -butanol blending on the ignition delay times of gasoline and its surrogate at high pressures

Agbro

Tomlin

Lawes

et al. 2017

Fuel

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“…As the volume fraction of iso-butanol is increased further to 10% (iB10), the mean peak pressure increases relative to iB05, and the mean crank angle location decreases. Generally, alcohols have been reported in the literature to display faster burning velocities than iso-octane and toluene (large components of the 5-C surrogate), which would be expected to produce an increase in the maximum pressure for fuels with similar calorific values. ,,,,, In the literature, iso-butanol has been shown to produce laminar burning velocities similar to, but slightly faster than, those of gasoline, iso-octane, and toluene, at similar conditions. − However, interpreting laminar burning velocities in the context of SI engine conditions can be uncertain, as highlighted in the works of Serras-Pereira et al and Aleiferis et al These studies describe issues with interpreting such data due to nonidealistic phenomena during engine combustion, such as turbulence, flame cellularity, and changing temperatures and pressures. Aleiferis et al utilized a high speed to obtain images of flame growth within a direct injection SI research engine, for a RON 95 gasoline, iso-octane, ethanol, n-butanol, ethanol, and methane.…”

Section: Resultsmentioning

confidence: 99%

“…This indicates a lower burning velocity than the reference gasoline, as peak pressure may be applied as a proxy for the burning rate for fuels of comparable calorific values. 3,51,52 This behavior was attributed to the broad compositional differences between the TRF and gasoline. The utilized TRF contained a higher concentration of paraffins, particularly the relatively slow burning iso-octane, while containing no ethanol or olefinic components, which have been shown to have higher burning velocities than iso-octane and toluene.…”

Section: Resultsmentioning

confidence: 99%

“…The Leeds University Ported Optical Engine, Mk II with a disc-shaped combustion chamber (LUPOE-2D) is capable of achieving the high end of compression pressures required to investigate combustion under modern SI engine conditions relevant to downsized, turbo-charged engines, as seen in various previous works. ,, The LUPOE-2D currently features a disc-shaped cylinder head, with a centrally located spark (consisting of a 0.5 mm steel anode, housed in a 3 mm diameter alumina sheath), to minimize the impact of turbulence and facilitate the generation of uniform in-cylinder fluid flow. This configuration is not typical of common SI engines (which often utilize a significantly off-center spark location) and may impact on the likelihood of engine knock within the LUPOE-2D, relative to an otherwise identical engine.…”

Section: Methodsmentioning

confidence: 99%

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Influence of Iso-Butanol Blending with a Reference Gasoline and Its Surrogate on Spark-Ignition Engine Performance

Michelbach

Tomlin

2021

Energy Fuels

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This study investigated the ability of a five-component gasoline surrogate (iso-octane, toluene, n-heptane, 1-hexene, and ethanol) to replicate the combustion and knocking behavior of a reference gasoline (PR5801 – RON 95.4, MON 86.6), under pressure boosted spark-ignition engine conditions at various levels of blending with iso-butanol. The ability of the neat surrogate was first evaluated for stoichiometric air/fuel mixtures, at an intake temperature and pressure of 320 K and 1.6 bar, respectively, and an end of compression pressure of 30 bar, over a range of spark discharge timings. Throughout this regime, the surrogate was found to produce a good representation of the gasoline, particularly in terms of mean engine cycle properties, knock onsets, and knock intensities. This high degree of similarity between the surrogate and gasoline has also seen previous rapid compression machine work, at comparable end-gas temperatures (Int. J. Chem. Kinet.202153787808). However, significant differences were observed between the cyclic variability of surrogate and gasoline results, which was attributed to compositional differences between the two fuels. This study also investigated the impact of iso-butanol blending (at ratios of 5–70% iso-butanol by volume) on the performance of the gasoline at knocking and nonknocking conditions, as well as the ability of the surrogate to replicate the observed blending behavior, at the same experimental conditions. In general, increasing the iso-butanol volume was shown to decrease the knocking propensity of the fuel, except for a nonlinear crossover behavior witnessed for 5% and 10% iso-butanol blends, wherein the 5% blend became less reactive than the 10% blend due to the heavy suppression of NTC behavior in the 10% blend. Even at such low concentrations, iso-butanol appears to act as a strong radical sink, as identified by brute-force sensitivity analysis of predicted knock onsets. This is consistent with the findings of the aforementioned rapid compression machine study. Blends of 20–50% iso-butanol were found to be optimal for use in SI engines, providing considerable antiknock benefits and comparable indicated power to gasoline, with blends of 20–30% being the most viable due to the lower quantities of biofuel required. Under blending with iso-butanol, the surrogate continued to perform well, but blends were observably less reactive than the corresponding gasoline blends at spark advance timings <8 °CA before top dead center. The consistency found between trends within the literature sourced rapid compression machine measurements, and engine data presented in this study highlight the proficiency of fundamental measurements in predicting combustion behavior within an engine at similar thermodynamic conditions.

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“…For all investigations described in this paper, the isooctane fuel was used with two fuel-air equivalence ratios of 0.8 and 1.0. The flame structures were investigated at two engine speeds, information about this engine, its air-fuel system and the data acquisition system can be found in [23]. The operation characteristics of LUPOE-2D under different conditions are presented in Tables 3.…”

Section: Research Enginementioning

confidence: 99%

Characterization of flame front wrinkling in a highly pressure-charged spark ignition engine

Zhang

Morsy

Ling

et al. 2022

Experimental Thermal and Fluid Science

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Particle Image Velocimetry (PIV) technique has been employed to investigate turbulent flame propagation in a relatively quiescent, optically accessed, boosted, two-stroke spark ignition engine.Turbulence scales and flame structure have been characterized based on Fourier analysis of an independent stationary coordinate at elevated pressures. Analysis shows that turbulence, with an initial rms value of 𝑢′, is modified by flames, and the strong induced velocity field ahead of it. As the flame grows, the persistence of larger scale structures as well as smaller scale wrinkling is apparent. Power spectral density (PSD) of flame wrinkling exhibit the same general trend under different operating conditions. These are in a good agreement with the previous data measured from other rigs (i.e. burners and bombs), which featured lower pressures. These functions have been normalized by terms of wrinkling parameters and other turbulence parameters. General PSD functions are developed. These can predict the flame wrinkling behavior at low and high pressures, in different experimental apparatuses.

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Knock Properties of Oxygenated Blends in Strongly Charged and Variable Compression Ratio Engines

Cited by 5 publications

References 24 publications

The influence of n -butanol blending on the ignition delay times of gasoline and its surrogate at high pressures

The influence of n -butanol blending on the ignition delay times of gasoline and its surrogate at high pressures

Influence of Iso-Butanol Blending with a Reference Gasoline and Its Surrogate on Spark-Ignition Engine Performance

Characterization of flame front wrinkling in a highly pressure-charged spark ignition engine

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