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The Physical and Chemical Effects of Fuel on Gasoline Compression Ignition

King Abdullah University of Science & Technology-R. Vallinayagam, Ponnya Hlaing, Abdullah S. AlRamadan, Yanzhao An, Bengt Johansson
Saudi Aramco-Jaeheon Sim, Junseok Chang
Published 2019-04-02 by SAE International in United States
In the engine community, gasoline compression ignition (GCI) engines are at the forefront of research and efforts are being taken to commercialize an optimized GCI engine in the near future. GCI engines are operated typically at Partially Premixed Combustion (PPC) mode as it offers better control of combustion with improved combustion stability. While the transition in combustion homogeneity from convectional Compression Ignition (CI) to Homogenized Charge Compression Ignition (HCCI) combustion via PPC has been comprehensively investigated, the physical and chemical effects of fuel on GCI are rarely reported at different combustion modes. Therefore, in this study, the effect of physical and chemical properties of fuels on GCI is investigated. In-order to investigate the reported problem, low octane gasoline fuels with same RON = 70 but different physical properties and sensitivity (S) are chosen. Fuels with comparable sensitivity and RON are chosen to study the impact of physical properties on GCI. On the other hand, by keeping the same RON and physical properties, the effect of sensitivity on GCI is investigated. In this regard, three test…
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Variable Compression Ratio (VCR) Piston - Design Study

King Abdullah University of Science & Technology-Hao Shi, Sultan Al Mudraa, Bengt Johansson
Published 2019-04-02 by SAE International in United States
Variable compression ratio (VCR) technology has long been recognized as a method for improving the automobile engine performance, efficiency, fuel economy with reduced emission. This paper presents a design of hydraulically actuated piston based on the VCR piston proposed by the British Internal Combustion Engine Research Institute (BICERI). In this design, the compression height of the piston automatically changes in response to engine cylinder pressure by controlling the lubrication oil flow via valves in the piston. In addition, numerical models including piston kinetic model, oil hydraulic model, compression ratio model and etc., have been established to evaluate the piston properties. The oil flow characteristics between two chambers in VCR piston have been investigated and the response behaviors of VCR engine and normal engine, such as compression pressure and peak cylinder pressure, are compared at different engine loads. Moreover, the energy losses because of VCR piston vibration at high engine loads in firing cycles have been calculated. According to the analysis results, both of energy loss and related percentage in piston work output rise with engine…
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Mechanism Triggering Pre-Ignition in a Turbo-Charged Engine

King Abdullah University of Science & Technology-Eshan Singh, Robert Dibble
Published 2019-04-02 by SAE International in United States
Pre-ignition in modern engines is largely attributed to oil-fuel mixture droplets igniting before the spark timing. Researchers have also found pre-ignition events to be triggered by high hydrocarbon emissions from the previous cycle as well as late spark timing in the previous cycle. Additionally, an ideally scavenged engine was not found to be limited by pre-ignition. These observations point to a significant role of residuals in triggering pre-ignition events. Current work studies pre-ignition in a probabilistic approach. The effect of residuals and in-cylinder thermodynamic state is studied by varying the exhaust back pressure and intake air temperature respectively. Experiments were performed with a fixed mass flow rate of air + fuel and intake air temperature while the exhaust back pressure was varied. Intake air pressure varied in response to fixed intake temperature. Pre-ignition and super-knock count increased with increasing exhaust back pressure. In the next set of experiments, mass flow rate of air + fuel and intake air pressure were fixed, while the exhaust back pressure was varied. Intake air temperature was varied to fix…
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Effect of Different Fluids on Injection Strategies to Suppress Pre-Ignition

King Abdullah University of Science & Technology-Eshan Singh, Ponnya Hlaing, Hao Shi, Robert Dibble
Published 2019-04-02 by SAE International in United States
Pre-ignition is an abnormal engine combustion phenomenon where the inducted fuel-air charge ignites before the spark ignition. This premature combustion phenomenon often leads to heavy knocking events. The mixture preparation plays a critical role in pre-ignition tendency for a given load. Literature shows efforts made towards improving pre-ignition-limited-IMEP by splitting the injection pulse into multiple pulses. In this study, two direct injectors are used in a single cylinder research engine. A centrally mounted direct injector was used to inject Coryton Gasoline (RON 95) fuel early in the intake stroke. A second fluid was injected late in the compression stroke to suppress pre-ignition. The fluids used in the second direct injector was varied to see the effects of the molecule and its physical and chemical property on pre-ignition suppression tendency. Methanol, ethanol, water, and gasoline were tested as second fluid. Engine tests were conducted at 2000 rpm and at an intake pressure of 2.1 bar (abs). Although alcohols show high pre-ignition tendency as fuels, they were most effective at pre-ignition suppression when injected later in the…
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Combustion Stratification and Dynamic Flame Tracing Analysis of Partially Premixed Combustion in a Compression Ignition Engine Fueled with Low-Octane Fuel

King Abdullah University of Science & Technology-Yanzhao An, Hao Shi, R Vallinayagam, Bengt Johansson
Saudi Aramco-Jaeheon Sim, Junseok Chang
Published 2019-04-02 by SAE International in United States
Partially premixed combustion (PPC) is a low-temperature combustion concept, which is between conventional diesel compression ignition (CI) and homogeneous charge compression ignition (HCCI). In PPC mode, the start of injection timing (SOI) is earlier than that of CI and later than that of HCCI and stratified in-cylinder fuel/air mixture can be formed to control the auto-ignition by the fuel injection timing. Gasoline fuel is beneficial for PPC mode because of its superior resistance to auto-ignition, which can enhance fuel-air charge mixing process with longer ignition delay time. The scope of this study is to investigate in-cylinder auto-ignition, combustion evolution, combustion stratification, and engine-out emissions at PPC operating mode under lean and low load engine conditions with different injection timings. Primary reference fuel PRF77, was selected as the low-octane test fuel. Fuel-tracer planar laser-induced fluorescence (PLIF) imaging and high-speed color imaging based on natural flame luminosity were performed to visualize fuel injection, spray-wall interaction, and subsequent combustion evolution. Based on the intensity of high sped combustion images, combustion stratification and dynamic flame tracing were evaluated to…
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Novel Geometry Reaching High Efficiency for Multiple Injector Concepts

King Abdullah University of Science & Technology-Gustav Nyrenstedt, Hong Im, Bengt Johansson
Volvo Global Truck Tech Powertrain Eng-Arne Andersson
Published 2019-04-02 by SAE International in United States
Heat losses are known to decrease the efficiency of CI engines largely. Here, multiple injectors have been suggested to shrink these losses through reduction of spray wall impingement. Studies on multiple injectors have proven the concept’s heat transfer reduction but also highlighted the difficulty of using a standard piston bowl. This study proposes a two-injector concept combined with a flat bowl to reduce heat losses further. To change the spray pattern, the two injectors are injecting in a swirling motion while placed at the rim of the bowl. Four injection timings have been investigated using Reynolds-Averaged Navier-Stokes simulations. This computational method quantified the amount of heat loss reduction possible. A conventional single injector concept is compared to two injector concepts with a standard and flat bowl. A Double Compression Expansion Engine (DCEE) concept, based on a modified Volvo D13 single-cylinder engine, was the base for all simulations. The DCEE can re-use the residual exhaust energy for a second expansion meaning increased importance of reduced heat losses. Heat release effects were discarded in the evaluation as…
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Large-Eddy Simulation of Turbulent Dispersion Effects in Direct Injection Diesel and Gasoline Sprays

SAE International Journal of Advances and Current Practices in Mobility

King Abdullah University of Science & Technology-Hong Im, Francisco Hernandez Perez
University of Wisconsin Madison-Hongjiang Li, Christopher Rutland
  • Journal Article
  • 2019-01-0285
Published 2019-04-02 by SAE International in United States
In most large-eddy simulation (LES) applications to two-phase engine flows, the liquid-air interactions need to be accounted for as source terms in the respective governing equations. Accurate calculation of these source terms requires the relative velocity “seen” by liquid droplets as they move across the flow, which generally needs to be estimated using a turbulent dispersion model. Turbulent dispersion modeling in LES is very scarce in the literature. In most studies on engine spray flows, sub-grid scale (SGS) models for the turbulent dispersion still follow the same stochastic approach originally proposed for Reynolds-averaged Navier-Stokes (RANS). In this study, an SGS dispersion model is formulated in which the instantaneous gas velocity is decomposed into a deterministic part and a stochastic part. The deterministic part is reconstructed using the approximate deconvolution method (ADM), in which the large-scale flow can be readily calculated. The stochastic part, which represents the impact of the SGS flow field, is assumed to be locally homogeneous and isotropic and, therefore, governed by a Langevin-type equation. The model is applied to the spray G…
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A Path towards High Efficiency Using Argon in an HCCI Engine

King Abdullah University of Science & Technology-Abdulrahman Magdy Mohammed, Jean-Baptiste Masurier, Ali Elkhazraji, Robert Dibble, Bengt Johansson
Published 2019-04-02 by SAE International in United States
Argon replacing Nitrogen has been examined as a novel engine cycle reaching higher efficiency. Experiments were carried out under Homogeneous Charge Compression Ignition (HCCI) conditions using a single cylinder variable compression ratio Cooperative Fuel Research (CFR) engine. Isooctane has been used as the fuel for this study. All the parameters were kept fixed but the compression ratio to make the combustion phasing constant. Typical engine outputs and emissions were compared to conventional cycles with both air and synthetic air. It has been found that the compression ratio of the engine must be significantly reduced while using Argon due to its higher specific heat ratio. The resulting in-cylinder pressure was lower but combustion remains aggressive. However, greater in-cylinder temperatures were reached. To an end, Argon allows gains in fuel efficiency, in unburned hydrocarbon and carbon monoxide, as well as in indicated efficiency.
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Should We Walk or Take a Car for Minimum Greenhouse Gas Emissions?

King Abdullah University of Science & Technology-Rafig Babayev, Bengt Johansson
Published 2019-04-02 by SAE International in United States
This paper compares the greenhouse gas (GHG) emissions attributed to driving a popular production vehicle powered by an internal combustion engine (ICE), as well as a hybrid electric vehicle (HEV), with GHG emissions associated with walking, running and bicycling. The purpose of this study is to offer a different perspective on the problem of global warming due to anthropogenic causes, specifically on transportation and eating patterns. In order to accurately estimate emissions, a full life cycle of food has been considered coupled with energy expenditures of the aforementioned activities obtained from several different sources and averaged for more reliable results. The GHG emissions were calculated for Sweden, the UK, and the US. Depending on the availability of certain data, the methodology for different countries was altered slightly. The question whether walking, running or taking a bicycle is better for the environment than driving a car cannot be answered uniquely. This study demonstrates that the answer depends on several factors, such as diet composition, the number of people commuting, vehicle powertrain, as well as the country…
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HCCI Octane Number Scale in a Pressure-Temperature Diagram

King Abdullah University of Science & Technology-Jean-Baptiste Masurier, Ali Elkhazraji, Abdulrahman Mohammed, Bengt Johansson
Published 2019-04-02 by SAE International in United States
A new approach for investigating combustion behavior of practical fuels under homogeneous charge compression ignition (HCCI) conditions was developed with the help of a cooperative fuel research (CFR) engine. The method uses a set of two pressure-temperature diagrams and two charts, each with an octane number scale based on primary reference fuels (PRF), created from experimental results by sweeping the intake temperature. The two pressure-temperature diagrams report conditions leading to the start of the low temperature combustion and the start of the main combustion, respectively. Additional two charts -- required compression ratio and fraction of low temperature heat release charts -- describe global combustion behavior and the importance of the low temperature combustion. Each diagram and chart, together with their respective octane number scale, allow to examine the combustion behavior of practical fuels by comparing their combustion behavior with those of the PRFs. Finally, octane numbers representing the various combustion behaviors of a practical fuel can be rated. Application of the method with two low-octane number surrogate fuels led to the following main results. The…
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