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Isobaric Combustion at a Low Compression Ratio

King Abdullah University of Science & Technology-Aibolat Dyuisenakhmetov, Harsh Goyal, Moez Ben Houidi, Rafig Babayev, Bengt Johansson
Saudi Aramco-Jihad Badra
  • Technical Paper
  • 2020-01-0797
To be published on 2020-04-14 by SAE International in United States
In a previous study, it was shown that isobaric combustion cycle, achieved by multiple injection strategy, is more favorable than conventional diesel cycle for the double compression expansion engine (DCEE) concept. In spite of lower effective expansion ratio, the indicated efficiencies of isobaric cycles were approximately equal to those of a conventional diesel cycle. Isobaric cycles had lower heat transfer losses and higher exhaust losses which are advantageous for DCEE since additional exhaust energy can be converted into useful work in the expander. In this study, the performance of low-pressure isobaric combustion (IsoL) and high-pressure isobaric combustion (IsoH) in terms of gross indicated efficiency, energy flow distribution and engine-out emissions is compared to the conventional diesel combustion (CDC) but at a relatively lower compression ratio of 11.5. The experiments are conducted in a Volvo D13C500 single-cylinder heavy-duty engine using standard EU diesel fuel. The current study consists of two sets of experiments. In the first set, the effect of exhaust gas recirculation (EGR) is studied at different combustion modes using the same air-fuel ratio obtained…
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Combustion System Optimization of a Light-Duty GCI Engine Using CFD and Machine Learning

Aramco Research Center-Yuanjiang Pei
Argonne National Laboratory-Pinaki Pal, Sibendu Som
  • Technical Paper
  • 2020-01-1313
To be published on 2020-04-14 by SAE International in United States
In this study, the combustion system of a light-duty compression ignition engine running on a market gasoline fuel with Research Octane Number (RON) of 91 was optimized using computational fluid dynamics (CFD) and Machine Learning (ML). This work was focused on optimizing the piston bowl geometry at two compression ratios (CR) (17 and 18:1) and this exercise was carried out at full-load conditions (20 bar indicated mean effective pressure, IMEP). First, a limited manual piston design optimization was performed for CR 17:1, where a couple of pistons were designed and tested. Thereafter, a CFD design of experiments (DoE) optimization was performed where CAESES, a commercial software tool, was used to automatically perturb key bowl design parameters and CONVERGE software was utilized to perform the CFD simulations. At each compression ratio, 128 piston bowl designs were evaluated. Subsequently, a Machine Learning-Grid Gradient Algorithm (ML-GGA) approach was developed to further optimize the piston bowl design. This extensive optimization exercise yielded significant improvements in the engine performance and emissions compared to the baseline piston bowl designs. Up to…
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Isobaric Combustion for High Efficiency in an Optical Diesel Engine

King Abdullah University of Science & Technology-Gustav Nyrenstedt, Abdullah Al Ramadan, Qinglong Tang, Moez Ben Houidi, Bengt Johansson
Saudi Aramco-Jihad Badra, Emre Cenker
  • Technical Paper
  • 2020-01-0301
To be published on 2020-04-14 by SAE International in United States
Isobaric combustion has been proven a promising strategy for high efficiency as well as low nitrogen oxides emissions, particularly in heavy-duty Diesel engines. Previous single-cylinder research engine experiments have, however, shown high soot levels when operating isobaric combustion. The combustion itself and the emissions formation with this combustion mode are not well understood due to the complexity of multiple injections strategy. Therefore, experiments with an equivalent heavy-duty Diesel optical engine were performed in this study. Three different cases were compared, an isochoric heat release case and two isobaric heat release cases. One of the isobaric cases was boosted to reach the maximum in-cylinder pressure of the isochoric one. The second isobaric case kept the same boost levels as the isochoric case. Results showed that in the isobaric cases, liquid fuel was injected into burning gases. This resulted in shorter ignition delays and thus a poor mixing level. The lack of fuel/air mixing was clearly the main contributor to the high soot emissions observed in isobaric combustion. The lower heat losses of the isobaric strategy were…
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Validation of Computational Models for Isobaric Combustion Engines

King Abdullah University of Science & Technology-Hammam H. Aljabri, Rafig Babayev, Xinlei Liu, Bengt Johansson, Hong G. Im
Saudi Aramco-Jihad Badra
  • Technical Paper
  • 2020-01-0806
To be published on 2020-04-14 by SAE International in United States
The focus of this study is to aid the development of the isobaric combustion engine by investigating multiple injection strategies at moderately high pressures. A three-dimensional (3D) commercial computational fluid dynamics (CFD) code, CONVERGE, was used to conduct simulations. The validation of the isobaric combustion case was carried out through the use of a single injector with multiple injections. The computational simulations were matched to the experimental data using methods outlined in this paper for different multiple injection cases. A sensitivity analysis to understand the effects of different modeling components on the quantitative prediction was carried out. First, the effects of the kinetic mechanisms were assessed by employing different chemical mechanisms, and the results showed no significant difference in the conditions under consideration. Next, different liquid fuel properties were examined, and it was found that the physical properties of the fuels have a notable effect in terms of evaporation and atomization, which lead to a variation in the considered numerical case. The effect of thermodynamics properties was also investigated by testing different equations of state…
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Optical Study on the Fuel Spray Characteristics of the Four-Consecutive-Injections Strategy Used in High-Pressure Isobaric Combustion

King Abdullah University of Science & Technology-Qinglong Tang, Ramgopal Sampath, Priybrat Sharma, Gustav Nyrenstedt, Abdullah Al Ramadan, Moez Ben Houidi, Bengt Johansson, Gaetano Magnotti
Saudi Aramco-Jihad Badra
  • Technical Paper
  • 2020-01-1129
To be published on 2020-04-14 by SAE International in United States
High-pressure isobaric combustion used in the double compression expansion engine (DCEE) concept was proposed to obtain higher engine brake thermal efficiency than the conventional diesel engine. Experiments on the metal engines showed that four consecutive injections delivered by a single injector can achieve isobaric combustion. Improved understanding of the detailed fuel-air mixing with multiple consecutive injections is needed to optimize the isobaric combustion and reduce engine emissions. In this study, we explored the fuel spray characteristics of the four-consecutive-injections strategy using high-speed imaging with background illumination and fuel-tracer planar laser-induced fluorescence (PLIF) imaging in a heavy-duty optical engine under non-reactive conditions. Toluene of 2% by volume was added to the n-heptane and served as the tracer. The fourth harmonic of a 10 Hz Nd:YAG laser was applied for the excitation of toluene. The PLIF image distortion caused by the side window curvature and the optical piston was mitigated using a correction lens and corrected with a grid mapping technique. The effects of hydraulic delay and injection dwell on the in-cylinder liquid-phase fuel penetration and vapor-phase…
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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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Standardized Gasoline Compression Ignition Fuels Matrix

King Abdullah University of Science & Technology-Abdullah AlRamadan, Ahfaz Ahmed
Saudi Aramco-Jihad Badra, Radwan Bakor, Mohammed Almansour, Jaeheon Sim, Yoann Viollet, Junseok Chang
Published 2018-04-03 by SAE International in United States
Direct injection compression ignition engines running on gasoline-like fuels have been considered an attractive alternative to traditional spark ignition and diesel engines. The compression and lean combustion mode eliminates throttle losses yielding higher thermodynamic efficiencies and the better mixing of fuel/air due to the longer ignition delay times of the gasoline-like fuels allows better emission performance such as nitric oxides (NOx) and particulate matter (PM). These gasoline-like fuels which usually have lower octane compared to market gasoline have been identified as a viable option for the gasoline compression ignition (GCI) engine applications due to its lower reactivity and lighter evaporation compared to diesel. The properties, specifications and sources of these GCI fuels are not fully understood yet because this technology is relatively new. In this work, a GCI fuel matrix is being developed based on the significance of certain physical and chemical properties in GCI engine operation. Those properties were chosen to be density, temperature at 90 volume % evaporation (T90) or final boiling point (FBP) and research octane number (RON) and the ranges of…
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Spray Modeling for Outwardly-Opening Hollow-Cone Injector

KAUST-Jaeheon Sim, Ahmed Elwardany, Hong Im
Saudi Aramco-Jihad Badra
Published 2016-04-05 by SAE International in United States
The outwardly-opening piezoelectric injector is gaining popularity as a high efficient spray injector due to its precise control of the spray. However, few modeling studies have been reported on these promising injectors. Furthermore, traditional linear instability sheet atomization (LISA) model was originally developed for pressure swirl hollow-cone injectors with moderate spray angle and toroidal ligament breakups. Therefore, it is not appropriate for the outwardly-opening injectors having wide spray angles and string-like film structures. In this study, a new spray injection modeling was proposed for outwardly-opening hollow-cone injector. The injection velocities are computed from the given mass flow rate and injection pressure instead of ambiguous annular nozzle geometry. The modified Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) breakup model is used with adjusted initial Sauter mean diameter (SMD) for modeling breakup of string-like structure. Spray injection was modeled using a Lagrangian discrete parcel method within the framework of commercial CFD software CONVERGE, and the new model was implemented through the user-defined functions. A Siemens outwardly-opening hollow-cone spray injector was characterized and validated with existing experimental data at the injection…
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Effects of In-Cylinder Mixing on Low Octane Gasoline Compression Ignition Combustion

King Abdullah University of Science and Technology-Ahmed Elwardany, Jaeheon Sim, Hong Im
Saudi Aramco-Jihad Badra, Yoann Viollet, Junseok Chang
Published 2016-04-05 by SAE International in United States
Gasoline compression ignition (GCI) engines have been considered an attractive alternative to traditional spark ignition engines. Low octane gasoline fuel has been identified as a viable option for the GCI engine applications due to its longer ignition delay characteristics compared to diesel and in the volatility range of gasoline fuels. In this study, we have investigated the effect of different injection timings at part-load conditions using light naphtha stream in single cylinder engine experiments in the GCI combustion mode with injection pressure of 130 bar. A toluene primary reference fuel (TPRF) was used as a surrogate for the light naphtha in the engine simulations performed here. A physical surrogate based on the evaporation characteristics of the light naphtha has been developed and its properties have been implemented in the engine simulations. Full cycle GCI computational fluid dynamics (CFD) engine simulations have been successfully performed while changing the start of injection (SOI) timing from -50° to -11 ° CAD aTDC. The effect of SOI on mixing and combustion phasing was investigated using detailed equivalence ratio-temperature maps…
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Modeling of Heating and Evaporation of FACE I Gasoline Fuel and its Surrogates

KAUST-Jaeheon Sim, Muneeb Khurshid, Mani Sarathy, Hong Im
KAUST, Alexandria University-Ahmed Elwardany
Published 2016-04-05 by SAE International in United States
The US Department of Energy has formulated different gasoline fuels called ''Fuels for Advanced Combustion Engines (FACE)'' to standardize their compositions. FACE I is a low octane number gasoline fuel with research octane number (RON) of approximately 70. The detailed hydrocarbon analysis (DHA) of FACE I shows that it contains 33 components. This large number of components cannot be handled in fuel spray simulation where thousands of droplets are directly injected in combustion chamber. These droplets are to be heated, broken-up, collided and evaporated simultaneously. Heating and evaporation of single droplet FACE I fuel was investigated. The heating and evaporation model accounts for the effects of finite thermal conductivity, finite liquid diffusivity and recirculation inside the droplet, referred to as the effective thermal conductivity/effective diffusivity (ETC/ED) model. The temporal variations of the liquid mass fractions of the droplet components were used to characterize the evaporation process. Components with similar evaporation characteristics were merged together. A representative component was initially chosen based on the highest initial mass fraction. Three 6 components surrogates, Surrogate 1-3, that match…
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