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On Maximizing Argon Engines' Performance via Subzero Intake Temperatures in HCCI Mode at High Compression Ratios

King Abdullah University of Science & Technology-Ali Elkhazraji, Abdulrahman Mohammed, Sufyan Jan, Jean-Baptiste Masurier, Robert Dibble, Bengt Johansson
  • Technical Paper
  • 2020-01-1133
To be published on 2020-04-14 by SAE International in United States
Maximizing the indicated thermal efficiency with minimal amount of emissions is one of the main challenges to overcome in the field of internal combustion engines. The main obstacle that hinders achieving this goal is the typically low thermodynamic efficiency which is the ratio of the positive produced work on the piston to the amount of heat released inside the cylinder. Many concepts and technologies were innovated to maximize the thermodynamic efficiency. One of the main guidelines that have been followed to achieve so, is the ideal Otto’s cycle that predicts that increasing the compression ratio and/or the specific heat ratio of the combustion reactants, will maximize the thermodynamic efficiency. This study combines both high compression ratios and a high specific heat ratio via two of the main approaches used to maximize the thermodynamic efficiency. First, is the HCCI combustion mode. HCCI is typically operated at fuel-lean conditions, allowing to operate at higher compression ratios without having intense knock (pressure waves, generated by undesired autoignition, that can damage the engine). Second, air was replaced by an…
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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 work, the performance of isobaric combustion cycles in terms of indicated efficiency, emissions, and energy flow distribution is compared to the conventional diesel cycle but at a relatively lower compression ratio. A standard 17-compression ratio piston is replaced by a low 11.5-compression ratio piston. GT power simulations suggest that a low compression ratio of the high-pressure unit of DCEE could lead to an improvement in efficiency. The current study consists of two sets of experiments. In the first set of experiments, the intake pressure and intake temperatures are increased to…
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Effects of geometry on passive pre-chamber combustion characteristics

King Abdullah University of Science & Technology-Mickael Silva, Sangeeth Sanal, Ponnya Hlaing, Bengt Johansson, Hong G. Im
Saudi Aramco-Emre Cenker
  • Technical Paper
  • 2020-01-0821
To be published on 2020-04-14 by SAE International in United States
Towards a fundamental understanding of the ignition characteristics of pre-chamber (PC) combustion engines, computational fluid dynamics (CFD) simulations were conducted using CONVERGE. To assist the initial design of the KAUST pre-chamber engine experiments, the primary focus of the present study was to assess the impact of design parameters such as throat diameter, nozzle diameter, and nozzle length. The well-stirred reactor combustion model coupled with a methane oxidation mechanism reduced from GRI 3.0 was used. A homogeneous charge of methane and air with λ = 1.3 on both the PC and main chamber (MC) was assumed. The geometrical parameters were shown to affect the pre-chamber combustion characteristics, such as pressure build-up, radical formation, and heat release as well as the composition of the jets penetrating and igniting the main chamber charge. In addition, the backflow of species pushed inside the pre-chamber due to the flow reversal (FR) event was analyzed. It was found that the narrow throat type of pre-chamber is strongly influenced by the throat diameter, but weakly influence by nozzle length. A flow reversal…
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Effects of Pre-chamber Enrichment on Lean Burn Pre-chamber Spark Ignition Combustion with a Narrow-throat Geometry

King Abdullah University of Science & Technology-Ponnya Hlaing, Manuel Echeverri Marquez, Eshan Singh, Fahad Almatrafi, Moez Ben Houidi, Bengt Johansson
Saudi Aramco-Emre Cenker
  • Technical Paper
  • 2020-01-0825
To be published on 2020-04-14 by SAE International in United States
Pre-chamber spark ignition (PCSI) combustion is an emerging lean-burn combustion mode capable of extending the lean operation limit of an engine. The favorable characteristic of short combustion duration at the lean condition of PCSI results in high indicated efficiencies and low specific fuel consumption compared to conventional spark ignition combustion. Since the engine operation is typically lean, PCSI can significantly reduce engine-out NOx emissions while maintaining relatively short combustion duration. In this study, experiments were conducted on a heavy-duty engine at mid to low loads to study the effects of pre-chamber enrichment on globally lean combustion with methane fuel injection in both pre and main chambers. Two parametric variations were performed where, in the first study, the total fuel energy input to the engine was fixed while the intake pressure was varied, which resulted in varying the global air excess ratio. In the second, the intake pressure was fixed while the amount of fuel injection was changed to alter the global air excess ratio. At each global air excess ratio, the fuel injection to the…
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Optical diagnostics of isooctane and n-heptane isobaric combustion

King Abdullah University of Science & Technology-Abdullah S. Al Ramadan, Gustav Nyrenstedt, Moez Ben Houidi, Bengt Johansson
  • Technical Paper
  • 2020-01-1126
To be published on 2020-04-14 by SAE International in United States
Isobaric combustion has demonstrated a great potential to reach high thermodynamic efficiency in the advanced Double Compression Expansion Engine (DCEE) concept. It appears as one of few viable choices for applications with high-pressure combustion. At these conditions, releasing heat at a constant pressure minimizes the peak in-cylinder pressure and, hence, mitigates excessive mechanical stress on the engine. This study focus on the effect of fuels on the multiple-injection isobaric combustion. A single-cylinder heavy-duty engine was utilized to test and compare the isobaric combustion with pure isooctane and n-heptane fuels. The engine was equipped with a fully optical piston to allow studying multiple-injection interactions and combustion behavior using high-speed acquisition of chemiluminescence. Two isobaric cases has been studied with peak pressure of 50 bar (IsobaricL) and 70 bar (IsobaricH). These two cases were compared with conventional diesel combustion (CDC) case that shares similar intake conditions as the IsobaricL but with peak cylinder pressure as the IsobaricH. For cases with high soot luminosity, a short band-pass filter was used to avoid image saturation. Fuels with short ignition…
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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
Combustion control is increasingly important for high efficiency in the compression ignition engines of the future. Especially, isobaric combustion has been targeted as an area of interest. Earlier studies have highlighted the increased performance as well as difficulties, utilizing multiple close injections for combustion control. These difficulties include low oxygen concentration and high emissions. This study aims to experimentally investigate the cause of these in an optical heavy-duty Volvo D13 engine. High-speed imaging, as well as laser studies, are utilized towards this purpose. By using a quartz piston as well as windows in the liner, a comprehensive view-field was established. Combustion behavior, in terms of ignition delay, mixing and chamber utilization is investigated. By using an alternating number of injections at different times, the effects of achieving isobaric combustion as well as injector dwell time are concluded. Results show that complexities when using multiple injections origin from the behavior of spraying into an already combusted zone. Slower mixing, as well as longer ignition delays, are observed for multiple injections as compared to a single injection.…
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A numerical study on the ignition of lean CH4/air mixture by a pre-chamber-initiated turbulent jet

King Abdullah University of Science & Technology-Sangeeth Sanal, Mickael Silva, Ponnya Hlaing, Bengt Johansson, Hong G. Im
Saudi Aramco-Emre Cenker
  • Technical Paper
  • 2020-01-0820
To be published on 2020-04-14 by SAE International in United States
Ultra-lean combustion in a spark-ignited (SI) engine is one of the most promising methods explored to reduce the nitrogen oxides (NOx) emissions and increases engine efficiency by decreasing the peak combustion temperature. However, this leads to an increase in combustion instabilities, hence emissions of unburned hydrocarbons (UHC). A spark ignited stratified pre-chamber combustion system has been demonstrated to overcome the obstacles related to ultra-lean combustion. However, the ignition mechanism of the ultra-lean mixture is not well studied. For that, the turbulent jet forced out of the pre-chamber through the nozzles needs to be well understood. The turbulent jet ignition can be either flame ignition (hot active radicals) or jet ignition (hot combustion products), depending on the pressure gradient and nozzle diameter. This hot jet determines the combustion characteristics of the lean main-chamber mixture and engine performance. Converge CFD code was used in this study, and the model used were validated against the measurements performed in-house. To elucidate the main-chamber ignition mechanism, the spark plug location and the spark timing were varied, resulting in different pressure…
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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
This study aims to contribute to the development of the isobaric combustion engines by exploring multiple injection strategies, employing computational simulations using a commercial CFD code Converge. As a first attempt to achieve isobaric combustion, a multiple injection strategy using a single injector was explored with up to four consecutive injections. Considering that the computational simulations were unable to reproduce the experimental data due to several uncertainties, the present study attempted to identify the leading causes of the discrepancies through a sensitivity analysis. First, different liquid fuel properties were examined, and it was found that, while the physical properties of the fuels have a notable effect in terms of evaporation and atomization, such variations were not sufficient to reproduce the experimentally observed heat release rate. Next, the effects of the uncertainties in the kinetic mechanisms were assessed by the reaction multiplier, an artificial adjustment of the rate constants, and it was found that the reaction multiplier affected the ignition of the first injection, but not the subsequent injection events. As such, the use of reaction…
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Optical study on the fuel spray characteristics of high-pressure isobaric combustion using four consecutive injections

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 using the double compression expansion concept was proposed to obtain higher brake thermal efficiency than the conventional diesel combustion. Experiments in metal engines have shown 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 fuel-tracer planar laser-induced fluorescence (PLIF) imaging on a heavy-duty optical engine under non-reactive condition. Toluene of 2% by volume was added into the n-heptane fuel and served as the tracer. The fourth harmonic of a 10 Hz Nd:YAG laser was applied for excitation of toluene. One of the fuel sprays was bisected by the vertical laser sheet and visualized by a camera from the side view. The PLIF images of the premixed mixture formed by port fuel injection were used to normalize the direct-injection PLIF images and correct the effect of non-uniformity of the laser sheet.…
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Fuel Flexibility Study of a Compression Ignition Engine at High Loads

King Abdullah University of Science and Technology-Abdullah S. AlRamadan, Moez Ben Houidi, Gustav Nyrenstedt, Bengt Johansson
  • Technical Paper
  • 2019-01-2193
Published 2019-12-19 by SAE International in United States
Engine experiments were performed on a single-cylinder heavy-duty engine at relatively high loads to investigate the regions where the combustion characteristics are unchanged regardless of the fuel octane number. Primary Reference Fuels (PRFs) and three different commercial fuels with RON values ranging from 0 to 100 were tested in this study. A sweep of net indicated mean effective pressure (IMEPNet) of 5 to 20 bar, absolute intake pressure of 1.5 to 2.8 bar, exhaust gas recirculation (EGR) of 0 to 40%, and fuel injection pressure of 700 to 1400 bar were performed to investigate the combustion characteristics, ignition delay time, combustion duration, efficiency, and emissions. At the highest load point (IMEPNet = 20 bar), all the fuels burn as in conventional diesel combustion. Despite the wide range of octane numbers, all fuels had similar ignition delay time, combustion duration, indicated efficiency, and emissions at 10 to 20 bar IMEPNet. It follows that CI mode is the only realistic option at high load and pressure points. All fuels showed similar combustion duration and emission levels behavior…
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