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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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Studying Ignition Delay Time of Lubricant Oil Mixed with Alcohols, Water and Toluene in IQT and CVCC

King Abdullah University of Science & Technology-Sumit Maharjan, Ayman Elbaz, William Roberts
Abu Dhabi Polytechnic-Hatsari Mitsudharmadi
  • Technical Paper
  • 2020-01-1422
To be published on 2020-04-14 by SAE International in United States
The auto-ignition of liquid fuel and lubricant oil droplets is considered as one of the possible sources of pre-ignition. Researchers are continually finding new ways to form advanced lubricant oil by changing its composition and varying different oil additives to prevent the occurrence of this event. This study investigates additives for lubricants to suppress its auto-ignition tendency. Three sets of mixtures were prepared. The first set of mixtures were prepared by adding different alcohols namely ethanol, and methanol to the commercial lubricant oil (SAE 15W-40) in ratio of 1 - 5 % by vol The second set of mixtures were prepared by mixing SAE 15W-40 with aforementioned alcohols (1 % vol.) and H2O (1 % vol.). Lastly, the third set of mixtures were prepared by adding toluene to SAE 15W-40 in (1 % - 5% by vol.). Two experimental setups were used in the current work. An Ignition Quality Tester (IQT) was used to investigate the mixtures’ ignition delay time (IDT) following standard ASTM D6890 procedure, and a larger constant volume combustion chamber (CVCC) was…
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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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A path towards high efficiency SI combustion in a CFR engine: Cooling the intake to sub-zero temperatures

King Abdullah University of Science & Technology-Sufyan M. Jan, Abdulrahman Mohammed, Ali Elkhazraji, Jean-Baptiste Masurier
University of California-Robert Dibble
  • Technical Paper
  • 2020-01-0550
To be published on 2020-04-14 by SAE International in United States
Textbook engine thermodynamics predicts that SI (Spark Ignition) engine efficiency η is a function of both the compression ratio CR of the engine and the specific heat ratio γ of the working fluid. In practice the compression ratio of the SI engine is often limited due to “knock”. When this knock limit is reached, increase in heat transfer losses result in reduction in efficiency. One way to lower the end-gas temperature is to cool the intake gas before inducting it into the combustion chamber. With colder intake gases, higher CR can be deployed, resulting in higher efficiencies. In this regard, we investigated the indicated efficiency of the standard Waukesha CFR engine. The engine is operated in the SI engine mode. The engine was operated with three different mediums using the same fuel Methane (Gas). First is Air + Methane at room temperature, second was O2 + Argon + Methane gas mixture at room temperature, and lastly O2 + Argon +Methane at sub-zero conditions. We replace the Air by an Oxygen-Argon mixture to increase the specific…
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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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Numerical Investigation of the Combustion Kinetics of Partially Premixed Combustion (PPC) Fueled with Primary Reference Fuel

King Abdullah University of Science & Technology-Xinlei Liu
Tianjin University-Yuanyuan Zhao, Hu Wang, Daojian Liu, Wang Chen, Hongyan Zhu, Mingfa Yao
  • Technical Paper
  • 2020-01-0554
To be published on 2020-04-14 by SAE International in United States
This work numerically investigates the detailed combustion kinetics in a gasoline compression ignition (GCI) engine using three fuel injection strategies, including single-injection, double-injection, port fuel injection and direct injection (PFI+DI). A reduced Primary Reference Fuel (PRF) chemical kinetics mechanism was coupled with CONVERGE-SAGE CFD model to predict GCI combustion under various operating conditions. To provide insight into key reaction pathways, a post-process tool was used. The validated Converge CFD code with the PRF chemistry and the post-process tool was applied to investigate how the ignition occurs during the low-to high-temperature reaction transition and how it varies due to single- and double-injection and PFI+DI injection strategies. Three characteristic GCI combustion features were selected: (1) initial low temperature heat release (LTHR); (2) intense LTHR, where both iso-octane and n-heptane were converted to intermediates through oxygen-related reactions; (3) early stage high temperature heat release (HTHR) with CH2O as the core source species. It is found that the heat release was primarily dominated by the reaction H+O2 (+M)=HO2 (+M) and AC8H¬17+O2=AC8H17O2 during LTHR. For single- and double-injection, the high…
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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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Large Eddy Simulations of Supercritical and Transcritical Jet Flows using Real Fluid Thermophysical Properties

King Abdullah University of Science & Technology-Hong G. Im
Universidad de Oviedo-Adrian Pandal
  • Technical Paper
  • 2020-01-1153
To be published on 2020-04-14 by SAE International in United States
A satisfactory understanding of the complex phenomena of supercritical jet mixing is still lacking. When the injected fuel temperature and pressure are at supercritical conditions, the fuel spray becomes similar to gas jet situation and it leads to steady shock structures (Mach disk). The negligible effect of the interfacial surface tension force due to the supercritical conditions produces a diffuse interface. In order to understand supercritical jet flows further, well resolved large eddy simulations (LES) of a n-dodecane jet mixing with surrounding nitrogen are conducted. A real fluid thermodynamic model is used to account for the fuel compressibility and variable thermophysical properties due to the solubility of ambient gas and liquid jet using the cubic Peng-Robinson equation of state (PR-EOS). A molar averaged homogeneous mixing rule is used to calculate the mixing properties. The thermodynamic model is coupled with a pressure-based solver to simulate multispecies reacting flows. The numerical model is based on a second order accurate method implemented in the open source OpenFOAM-6 software. First, to evaluate the present numerical model of sprays, 1D…
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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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Combustion System Optimization of a Light-Duty GCI Engine Using CFD and Machine Learning

King Abdullah University of Science & Technology-Fethi khaled, Aamir Farooq
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…