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Isobaric Combustion at a Low Compression Ratio

Saudi Aramco-Jihad Badra
King Abdullah University of Science & Technology-Aibolat Dyuisenakhmetov, Harsh Goyal, Moez Ben Houidi, Rafig Babayev, Bengt Johansson
  • 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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Effects of Geometry on Passive Pre-Chamber Combustion Characteristics

Saudi Aramco-Emre Cenker
King Abdullah University of Science & Technology-Mickael Silva, Sangeeth Sanal, Ponnya Hlaing, Bengt Johansson, Hong G. Im
  • 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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Effect of Pre-Chamber Enrichment on Lean Burn Pre-Chamber Spark Ignition Combustion Concept with a Narrow-Throat Geometry

Saudi Aramco-Emre Cenker
King Abdullah University of Science & Technology-Ponnya Hlaing, Manuel Echeverri Marquez, Eshan Singh, Fahad Almatrafi, Moez Ben Houidi, Bengt Johansson
  • 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 efficiencies compared to conventional spark ignition combustion. Since the engine operation is typically lean, PCSI can significantly reduce engine-out NOx emissions while maintaining short combustion durations. In this study, experiments were conducted on a heavy-duty engine at lean conditions at mid to low load. Two major studies were performed. In the first study, the total fuel energy input to the engine was fixed while the intake pressure was varied, resulting in varying the global excess air ratio. In the second study, the intake pressure was fixed while the amount of fuel was changed to alter the global excess air ratio. At each global excess air ratio, the fuel injection to the pre-chamber was varied parametrically to assess the effect of pre-chamber enrichment on engine operating characteristics. Multi-chamber heat release analysis was performed to present the pre-chamber and main…
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Experimental Investigation of the Compression Ignition Process of High Reactivity Gasoline Fuels and E10 Certification Gasoline using a High-Pressure Direct Injection Gasoline Injector

Saudi Aramco-Jaeheon Sim
Aramco Services Co.-Tom Tzanetakis
  • Technical Paper
  • 2020-01-0323
To be published on 2020-04-14 by SAE International in United States
Gasoline compression ignition (GCI) technology shows the potential to obtain high thermal efficiencies while maintaining low soot and NOx emissions in light-duty engine applications. Recent experimental studies and numerical simulations have indicated that high reactivity gasoline-like fuels can further enable the benefits of GCI combustion. However, there is limited empirical data in the literature studying the gasoline compression ignition process at relevant in-cylinder conditions, which are required for further optimizing combustion system designs. This study investigates the temporal and spatial evolution of the compression ignition process of various high reactivity gasoline fuels with research octane numbers (RON) of 71, 74 and 82, as well as a conventional RON 97 E10 gasoline fuel. A ten-hole prototype gasoline injector specifically designed for GCI applications capable of injection pressures up to 450 bar was used. Vapor and liquid penetration from high speed optical visualizations, as well as combustion measurement were studied in an optically accessible constant volume spray and combustion chamber. Near simultaneous shadowgraph and Mie scattering images were captured to investigate the spray characteristics. OH* chemiluminescence and…
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A Demonstration of High Efficiency, High Reactivity Gasoline Compression Ignition Fuel in an On & Off Road Diesel Engine Application

Saudi Aramco-Jaeheon Sim, Junseok Chang
Doosan Infracore Co., Ltd.-Youngdeok Han, Dockoon Yoo, Woong Gun Lee
  • Technical Paper
  • 2020-01-1311
To be published on 2020-04-14 by SAE International in United States
The regulatory requirements to reduce both greenhouse gases and exhaust gas pollutants from heavy duty engines are driving new perspectives on the interaction between fuels and engines. Fuels that reliefs the burden on engine manufacturers to reach these goals are of particular interest. A low carbon fuel with a higher volatility and heating value than diesel is one such fuel that reduces engine-out emissions and carbon footprint from the entire hydrocarbon lifecycle (well-to-wheel) and improves fuel efficiency, which is a main enabler for gasoline compression ignition (GCI) technology. The present study investigated the potential of GCI technology by evaluating the performance of a low carbon high efficiency, high reactivity gasoline fuel in Doosan’s 6L medium duty diesel engine. In the experimental test, it was found that the fuel could provide the same performance in power and torque with the same calibration strategy as diesel, while the fuel efficiency was improved by maximum 4.3%. Overall total hydrocarbon (THC) and particulate matter (PM) emissions were decreased, but nitrogen oxides (NOx) was increased by average 6%. Computational fluid…
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Combustion System Optimization of a Light-Duty GCI Engine Using CFD and Machine Learning

Saudi Aramco-Jihad Badra, Jaeheon Sim, Yoann Viollet, Junseok Chang
Aramco Research Center-Yuanjiang Pei
  • 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

Saudi Aramco-Jihad Badra, Emre Cenker
King Abdullah University of Science & Technology-Gustav Nyrenstedt, Abdullah Al Ramadan, Qinglong Tang, Moez Ben Houidi, Bengt Johansson
  • 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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A Numerical Study on the Ignition of Lean CH4/Air Mixture by a Pre-Chamber-Initiated Turbulent Jet

Saudi Aramco-Emre Cenker
King Abdullah University of Science & Technology-Sangeeth Sanal, Mickael Silva, Ponnya Hlaing, Bengt Johansson, Hong G. Im
  • Technical Paper
  • 2020-01-0820
To be published on 2020-04-14 by SAE International in United States
To provide insights into the fundamental characteristics of pre-chamber combustion engines, the ignition of lean premixed CH4/air due to hot gas jets initiated by a passive narrow throated pre-chamber in a heavy-duty engine was studied computationally. A twelve-hole pre-chamber geometry was investigated using CONVERGETM software. The numerical model was validated against the experimental results. To elucidate the main-chamber ignition mechanism, the spark plug location and spark timing were varied, resulting in different pressure gradient during turbulent jet formation. Different ignition mechanisms were observed for turbulent jet ignition of lean premixed CH4/air, based on the geometry effect. Ignition behavior was classified into the flame and jet ignition depending on the significant presence of hot active radicals. The jet ignition, mainly due to hot product gases was found to be advanced by the addition of a small concentration of radicals. In turbulent conditions, the ignition behavior falls between the flame and jet ignition, depending on the pressure gradient and geometry of the pre-chamber. An ignition Damkohler number is identified and used to characterize different ignition behavior. The…
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Validation of Computational Models for Isobaric Combustion Engines

Saudi Aramco-Jihad Badra
King Abdullah University of Science & Technology-Hammam H. Aljabri, Rafig Babayev, Xinlei Liu, Bengt Johansson, Hong G. Im
  • 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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Development of Fast Idle Catalyst Light-Off Strategy for Gasoline Compression Ignition Engine - Part 2

Saudi Aramco-Yoann Viollet, Junseok Chang
Engine Fuel & Emissions Engineering Inc.-Vallinayagam Raman
  • Technical Paper
  • 2020-01-0314
To be published on 2020-04-14 by SAE International in United States
The present investigation expands on our previous work on development of fast idle catalyst light-off strategy for a light duty gasoline compression ignition (GCI) engine. In part 1, the steady state experimental investigation in a single cylinder GCI engine indicate an optimum strategy for effective catalyst light off during cold start fast idle operation. According to this strategy, the strategy includes (1) dispersing a first fuel injection during the intake stroke, (2) dispersing a second fuel injection during the expansion stroke, and (3) igniting a spark during the expansion stroke. This strategy increases the exhaust temperature during cold starts thereby assisting in lighting the oxidation catalyst, and reduce emissions and provide greater combustion stability as compared to other injection and spark strategies. In this study, based on the reported optimum strategy, a strategic sensitivity study was performed to investigate the impact of lambda, load, speed, spark plug design and injector spray pattern on effective cold start catalyst light off. The strategy, hereby specifically termed as tailed injection strategy, is as follows: 1) start of first…