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Autoignition of Isooctane beyond RON and MON Conditions

SAE International Journal of Fuels and Lubricants

King Abdullah University of Science & Technology-Jean-Baptiste Masurier, Muhammad Waqas, Mani Sarathy, Bengt Johansson
  • Journal Article
  • 2018-01-1254
Published 2018-04-03 by SAE International in United States
The present study experimentally examines the low-temperature autoignition area of isooctane within the in-cylinder pressure-in-cylinder temperature map.Experiments were run with the help of a Cooperative Fuel Research (CFR) engine. The boundaries of this engine were extended so that experiments could be performed outside the domain delimited by research octane number (RON) and motor octane number (MON) traces. Since homogeneous charge compression ignition (HCCI) combustion is governed by kinetics, the rotation speed for all the experiments was set at 600 rpm to allow time for low-temperature heat release (LTHR). All the other parameters (intake pressure, intake temperature, compression ratio, and equivalence ratio) were scanned, such as the occurrence of isooctane combustion.The principal results showed that LTHR for isooctane occurs effortlessly under high intake pressure (1.3 bar) and low intake temperature (25 °C). Increasing the intake temperature leads to the loss of the LTHR and therefore to a smaller domain on the pressure-temperature trace. In such a case, the LTHR domain is restricted from 20 to 50 bar in pressure and from 600 to 850 K in…
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Reduced Gasoline Surrogate (Toluene/n-Heptane/iso-Octane) Chemical Kinetic Model for Compression Ignition Simulations

Aramco Research Center-Yu Zhang, Tom Tzanetakis, Yuanjiang Pei
King Abdullah University of Science & Technology-Mani Sarathy, Nour Atef, Adamu Alfazazi
Published 2018-04-03 by SAE International in United States
Toluene primary reference fuel (TPRF) (mixture of toluene, iso-octane and heptane) is a suitable surrogate to represent a wide spectrum of real fuels with varying octane sensitivity. Investigating different surrogates in engine simulations is a prerequisite to identify the best matching mixture. However, running 3D engine simulations using detailed models is currently impossible and reduction of detailed models is essential. This work presents an AramcoMech reduced kinetic model developed at King Abdullah University of Science and Technology (KAUST) for simulating complex TPRF surrogate blends. A semi-decoupling approach was used together with species and reaction lumping to obtain a reduced kinetic model. The model was widely validated against experimental data including shock tube ignition delay times and premixed laminar flame speeds. Finally, the model was utilized to simulate the combustion of a low reactivity gasoline fuel under partially premixed combustion conditions.
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Auto-Ignition and Spray Characteristics of n-Heptane and iso-Octane Fuels in Ignition Quality Tester

King Abdullah University of Science & Technology-Mohammed Jaasim Mubarak Ali, Ayman Elhagrasy, Mani Sarathy, Sukho Chung, Hong G. Im
Published 2018-04-03 by SAE International in United States
Numerical simulations were conducted to systematically assess the effects of different spray models on the ignition delay predictions and compared with experimental measurements obtained at the KAUST ignition quality tester (IQT) facility. The influence of physical properties and chemical kinetics over the ignition delay time is also investigated. The IQT experiments provided the pressure traces as the main observables, which are not sufficient to obtain a detailed understanding of physical (breakup, evaporation) and chemical (reactivity) processes associated with auto-ignition. A three-dimensional computational fluid dynamics (CFD) code, CONVERGE™, was used to capture the detailed fluid/spray dynamics and chemical characteristics within the IQT configuration. The Reynolds-averaged Navier-Stokes (RANS) turbulence with multi-zone chemistry sub-models was adopted with a reduced chemical kinetic mechanism for n-heptane and iso-octane. The emphasis was on the assessment of two common spray breakup models, namely the Kelvin-Helmholtz/Rayleigh-Taylor (KH-RT) and linearized instability sheet atomization (LISA) models, in terms of their influence on auto-ignition predictions. Two spray models resulted in different local mixing, and their influence in the prediction of auto-ignition was investigated. The relative importance…
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Numerical Simulations of High Reactivity Gasoline Fuel Sprays under Vaporizing and Reactive Conditions

King Abdullah University of Science & Technology-Balaji Mohan, Mohammed Jaasim Mubarak Ali, Ahfaz Ahmed, Francisco Hernandez Perez, William Roberts, Mani Sarathy, Hong Im
Saudi Aramco-Jaeheon Sim
Published 2018-04-03 by SAE International in United States
Gasoline compression ignition (GCI) engines are becoming more popular alternative for conventional spark engines to harvest the advantage of high volatility. Recent experimental study demonstrated that high reactivity gasoline fuel can be operated in a conventional mixing controlled combustion mode producing lower soot emissions than that of diesel fuel under similar efficiency and NOx level [1]. Therefore, there is much interest in using gasoline-like fuels in compression ignition engines. In order to improve the fidelity of simulation-based GCI combustion system development, it is mandatory to enhance the prediction of spray combustion of gasoline-like fuels. The purpose of this study is to model the spray characteristics of high reactivity gasoline fuels and validate the models with experimental results obtained through an optically accessible constant volume vessel under vaporizing [2] and reactive conditions [3]. For reacting cases, a comparison of PRF and KAUST multi-component surrogate (KMCS) mechanism was done to obtain good agreement with the experimental ignition delay. From this study, some recommendations were proposed for GCI combustion modelling framework using gasoline like fuels.
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Blending Octane Number of Toluene with Gasoline-like and PRF Fuels in HCCI Combustion Mode

King Abdullah University of Science & Technology-Muhammad Umer Waqas, Jean-Baptiste Masurier, Mani Sarathy, Bengt Johansson
Published 2018-04-03 by SAE International in United States
Future internal combustion engines demand higher efficiency but progression towards this is limited by the phenomenon called knock. A possible solution for reaching high efficiency is Octane-on-Demand (OoD), which allows to customize the antiknock quality of a fuel through blending of high-octane fuel with a low octane fuel. Previous studies on Octane-on-Demand highlighted efficiency benefits depending on the combination of low octane fuel with high octane booster. The author recently published works with ethanol and methanol as high-octane fuels. The results of this work showed that the composition and octane number of the low octane fuel is significant for the blending octane number of both ethanol and methanol. This work focuses on toluene as the high octane fuel (RON 120). Aromatics offers anti-knock quality and with high octane number than alcohols, this work will address if toluene can provide higher octane enhancement. Our aim is to investigate the impact of three gasoline-like fuels and two Primary Reference Fuels (PRFs). More specifically, fuels are FACE (Fuels for Advanced Combustion Engines) I, FACE J, FACE A, PRF…
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Compression Ignition of Light Naphtha and Its Multicomponent Surrogate under Partially Premixed Conditions

King Abdullah Univ of Science & Tech-R. Vallinayagam, S. Vedharaj, Yanzhao An, Alaaeldin Dawood, Mani Sarathy, Bengt Johansson
Saudi Aramco-Junseok Chang
Published 2017-09-04 by SAE International in United States
Light naphtha is the light distillate from crude oil and can be used in compression ignition (CI) engines; its low boiling point and octane rating (RON = 64.5) enable adequate premixing. This study investigates the combustion characteristics of light naphtha (LN) and its multicomponent surrogate under various start of injection (SOI) conditions. LN and a five-component surrogate for LN, comprised of 43% n-pentane, 12% n-heptane, 10% 2-methylhexane, 25% iso-pentane and 10% cyclo-pentane, has been tested in a single cylinder optical diesel engine. The transition in combustion homogeneity from CI combustion to homogenized charge compression ignition (HCCI) combustion was then compared between LN and its surrogate.The engine experimental results showed good agreement in combustion phasing, ignition delay, start of combustion, in-cylinder pressure and rate of heat release between LN and its surrogate. The low temperature reaction (LTR) phase exhibited by LN and its surrogate were comparable, while ignition delay was prolonged as SOI is advanced from CI to HCCI combustion. Combustion images for LN and its surrogate were nearly similar, showing equal behaviour in both fuels.…
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Blending Behavior of Ethanol with PRF 84 and FACE A Gasoline in HCCI Combustion Mmode

King Abdullah Univ. of Science & Tech.-Muhammad Umer Waqas, Nour Atef, Eshan Singh, Jean-Baptiste MASURIER, Mani Sarathy, Bengt Johansson
Published 2017-09-04 by SAE International in United States
The blending of ethanol with PRF (Primary reference fuel) 84 was investigated and compared with FACE (Fuels for Advanced Combustion Engines) A gasoline surrogate which has a RON of 83.9. Previously, experiments were performed at four HCCI conditions but the chemical effect responsible for the non-linear blending behavior of ethanol with PRF 84 and FACE A was not understood. Hence, in this study the experimental measurements were simulated using zero-dimensional HCCI engine model with detailed chemistry in CHEMKIN PRO. Ethanol was used as an octane booster for the above two base fuels in volume concentration of 0%, 2%, 5% and 10%.The geometrical data and the intake valve closure conditions were used to match the simulated combustion phasing with the experiments. Low temperature heat release (LTHR) was detected by performing heat release analysis. LTHR formation depended on the base fuel type and the engine operating conditions suggesting that the base fuel composition has an important role in the formation of LTHR. The effect of ethanol on LTHR was explained by low temperature chemistry reactions and OH/HO2…
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Simulating HCCI Blending Octane Number of Primary Reference Fuel with Ethanol

King Abdullah University of Science and Technology-Eshan Singh, Muhammad Waqas, Bengt Johansson, Mani Sarathy
Published 2017-03-28 by SAE International in United States
The blending of ethanol with primary reference fuel (PRF) mixtures comprising n-heptane and iso-octane is known to exhibit a non-linear octane response; however, the underlying chemistry and intermolecular interactions are poorly understood. Well-designed experiments and numerical simulations are required to understand these blending effects and the chemical kinetic phenomenon responsible for them. To this end, HCCI engine experiments were previously performed at four different conditions of intake temperature and engine speed for various PRF/ethanol mixtures. Transfer functions were developed in the HCCI engine to relate PRF mixture composition to autoignition tendency at various compression ratios. The HCCI blending octane number (BON) was determined for mixtures of 2-20 vol % ethanol with PRF70. In the present work, the experimental conditions were considered to perform zero-dimensional HCCI engine simulations with detailed chemical kinetics for ethanol/PRF blends. The simulations used the actual engine geometry and estimated intake valve closure conditions to replicate the experimentally measured start of combustion (SOC) for various PRF mixtures. The simulated HCCI heat release profiles were shown to reproduce the experimentally observed trends, specifically…
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Evaluation of Anti-Knock Quality of Dicyclopentadiene-Gasoline Blends

King Abdullah University of Science and Technology-Mohannad Al-Khodaier, Vijai Shankar Bhavani Shankar, Muhammad Waqas, Nimal Naser, Mani Sarathy, Bengt Johansson
Published 2017-03-28 by SAE International in United States
Increasing the anti-knock quality of gasoline fuels can enable higher efficiency in spark ignition engines. In this study, the blending anti-knock quality of dicyclopentadiene (DCPD), a by-product of ethylene production from naphtha cracking, with various gasoline fuels is explored. The blends were tested in an ignition quality tester (IQT) and a modified cooperative fuel research (CFR) engine operating under homogenous charge compression ignition (HCCI) and knock limited spark advance (KLSA) conditions. Due to current fuel regulations, ethanol is widely used as a gasoline blending component in many markets. In addition, ethanol is widely used as a fuel and literature verifying its performance. Moreover, because ethanol exhibits synergistic effects, the test results of DCPD-gasoline blends were compared to those of ethanol-gasoline blends. The experiments conducted in this work enabled the screening of DCPD auto-ignition characteristics across a range of combustion modes. The synergistic blending nature of DCPD was apparent and appeared to be greater than that of ethanol. The data presented suggests that DCPD has the potential to be a high octane blending component in gasoline;…
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Auto-Ignition of Iso-Stoichiometric Blends of Gasoline-Ethanol-Methanol (GEM) in SI, HCCI and CI Combustion Modes

Eindhoven University of Technology-Jeroen Feijs
King Abdullah University of Science and Technology-Muhammad Waqas, Nimal Naser, Mani Sarathy, Gustav Nyrenstedt, Bengt Johansson
Published 2017-03-28 by SAE International in United States
Gasoline-ethanol-methanol (GEM) blends, with constant stoichiometric air-to-fuel ratio (iso-stoichiometric blending rule) and equivalent to binary gasoline-ethanol blends (E2, E5, E10 and E15 in % vol.), were defined to investigate the effect of methanol and combined mixtures of ethanol and methanol when blended with three FACE (Fuels for Advanced Combustion Engines) Gasolines, I, J and A corresponding to RON 70.2, 73.8 and 83.9, respectively, and their corresponding Primary Reference Fuels (PRFs). A Cooperative Fuel Research (CFR) engine was used under Spark Ignition and Homogeneous Charge Compression Ignited modes. An ignition quality tester was utilized in the Compression Ignition mode. One of the promising properties of GEM blends, which are derived using the iso-stoichiometric blending rule, is that they maintain a constant octane number, which has led to the introduction of methanol as a drop-in fuel to supplement bio-derived ethanol. A constant RON/HCCI fuel number/derived Research octane number property was observed in all three combustion modes for high RON fuels, but for low RON fuels, the iso-stoichiometric blending rule for constant octane number did not appear to…
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