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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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Low Load Limit Extension for Gasoline Compression Ignition Using Negative Valve Overlap Strategy

King Abdullah University of Science & Technology-R. Vallinayagam, Abdullah S. AlRamadan, S Vedharaj, Yanzhao An, Bengt Johansson
Saudi Aramco-Jaeheon Sim, Junseok Chang
Published 2018-04-03 by SAE International in United States
Gasoline compression ignition (GCI) is widely studied for the benefits of simultaneous reduction in nitrogen oxide (NOX) and soot emissions without compromising the engine efficiency. Despite this advantage, the operational range for GCI is not widely expanded, as the auto-ignition of fuel at low load condition is difficult. The present study aims to extend the low load operational limit for GCI using negative valve overlap (NVO) strategy. The engine used for the current experimentation is a single cylinder diesel engine that runs at an idle speed of 800 rpm with a compression ratio of 17.3. The engine is operated at homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC) combustion modes with the corresponding start of injection (SOI) at −180 CAD (aTDC) and −30 CAD (aTDC), respectively. In the presented work, intake air temperature is used as control parameter to maintain combustion stability at idle and low load condition, while the intake air pressure is maintained at 1 bar (ambient). The engine is equipped with variable valve cam phasers that can phase both inlet and exhaust…
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Compression Ignition of Light Naphtha and Its Multicomponent Surrogate under Partially Premixed Conditions

King Abdullah Univ of Science & Tech-R. Vallinayagam, S. Vedharaj, Yanzhao An, Alaaeldin Dawood, Mani Sarathy, Bengt Johansson
Saudi Aramco-Junseok Chang
Published 2017-09-04 by SAE International in United States
Light naphtha is the light distillate from crude oil and can be used in compression ignition (CI) engines; its low boiling point and octane rating (RON = 64.5) enable adequate premixing. This study investigates the combustion characteristics of light naphtha (LN) and its multicomponent surrogate under various start of injection (SOI) conditions. LN and a five-component surrogate for LN, comprised of 43% n-pentane, 12% n-heptane, 10% 2-methylhexane, 25% iso-pentane and 10% cyclo-pentane, has been tested in a single cylinder optical diesel engine. The transition in combustion homogeneity from CI combustion to homogenized charge compression ignition (HCCI) combustion was then compared between LN and its surrogate.The engine experimental results showed good agreement in combustion phasing, ignition delay, start of combustion, in-cylinder pressure and rate of heat release between LN and its surrogate. The low temperature reaction (LTR) phase exhibited by LN and its surrogate were comparable, while ignition delay was prolonged as SOI is advanced from CI to HCCI combustion. Combustion images for LN and its surrogate were nearly similar, showing equal behaviour in both fuels.…
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Fuel Effect on Combustion Stratification in Partially Premixed Combustion

King Abdullah Univ of Science & Tech-S. Vedharaj, R. Vallinayagam, Yanzhao An, Alaaeldin Dawood, Bengt Johansson
Saudi Aramco-Junseok Chang
Published 2017-09-04 by SAE International in United States
The literature study on PPC in optical engine reveals investigations on OH chemiluminescence and combustion stratification. So far, mostly PRF fuel is studied and it is worthwhile to examine the effect of fuel properties on PPC. Therefore, in this work, fuel having different octane rating and physical properties are selected and PPC is studied in an optical engine. The fuels considered in this study are diesel, heavy naphtha, light naphtha and their corresponding surrogates such as heptane, PRF50 and PRF65 respectively. Without EGR (Intake O2 = 21%), these fuels are tested at an engine speed of 1200 rpm, fuel injection pressure of 800 bar and pressure at TDC = 35 bar. SOI is changed from late to early fuel injection timings to study PPC and the shift in combustion regime from CI to PPC is explored for all fuels. An increased understanding on the effect of fuel octane number, physical properties and chemical composition on combustion and emission formation is obtained. High-speed images of the combustion process are analyzed for each and every fuel and…
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Effect of Aromatics on Combustion Stratification and Particulate Emissions from Low Octane Gasoline Fuels in PPC and HCCI Mode

King Abdullah Univ of Science & Tech-Yanzhao An, S. Vedharaj, R. Vallinayagam, Alaaeldin Dawood, Jean-Baptiste MASURIER, Bengt Johansson
Saudi Aramco-Junseok Chang
Published 2017-09-04 by SAE International in United States
The objective of this study was to investigate the effect of aromatic on combustion stratification and particulate emissions for PRF60. Experiments were performed in an optical CI engine at a speed of 1200 rpm for TPRF0 (100% v/v PRF60), TPRF20 (20% v/v toluene + 80% PRF60) and TPRF40 (40% v/v toluene + 60% PRF60). TPRF mixtures were prepared in such a way that the RON of all test blends was same (RON = 60). Single injection strategy with a fuel injection pressure of 800 bar was adopted for all test fuels. Start of injection (SOI) was changed from early to late fuel injection timings, representing various modes of combustion viz HCCI, PPC and CDC. High-speed video of the in-cylinder combustion process was captured and one-dimensional stratification analysis was performed from the intensity of images. Particle size, distribution and concentration were measured and linked with the in-cylinder combustion images. Results showed that combustion advanced from CDC to PPC and then attained a constant value in HCCI mode. In PPC and HCCI region, the soot mass concentration…
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Effect of Timing and Location of Hotspot on Super Knock during Pre-ignition

King Abdullah University of Science and Technology-Mohammed Jaasim Mubarak Ali, Francisco Hernandez Perez, S. Vedharaj, R. Vallinayagam, Robert Dibble, Hong Im
Published 2017-03-28 by SAE International in United States
Pre-ignition in SI engine is a critical issue that needs addressing as it may lead to super knock event. It is widely accepted that pre-ignition event emanates from hot spot(s) that can be anywhere inside the combustion chamber. The location and timing of hotspot is expected to influence the knock intensity from a pre-ignition event. In this study, we study the effect of location and timing of hot spot inside the combustion chamber using numerical simulations. The simulation is performed using a three-dimensional computational fluid dynamics (CFD) code, CONVERGE™. We simulate 3-D engine geometry coupled with chemistry, turbulence and moving structures (valves, piston). G-equation model for flame tracking coupled with multi-zone model is utilized to capture auto-ignition (knock) and solve gas phase kinetics. A parametric study on the effect of hot spot timing and location inside the combustion chamber is performed. The hot spot timing considered are -180 CAD, -90 CAD and -30 CAD and the locations of the hot spots are in the center and two edges of the piston surfaces. Simulation results for…
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Combustion Stratification for Naphtha from CI Combustion to PPC

Eindhoven University Of Technology-Mohammad Izadi Najafabadi, Bart Somers
King Abdullah University of Science and Technology-R. Vallinayagam, S. Vedharaj, Yanzhao An, Alaaeldin Dawood, Bengt Johansson
Published 2017-03-28 by SAE International in United States
This study demonstrates the combustion stratification from conventional compression ignition (CI) combustion to partially premixed combustion (PPC). Experiments are performed in an optical CI engine at a speed of 1200 rpm for diesel and naphtha (RON = 46). The motored pressure at TDC is maintained at 35 bar and fuelMEP is kept constant at 5.1 bar to account for the difference in fuel properties between naphtha and diesel. Single injection strategy is employed and the fuel is injected at a pressure of 800 bar. Photron FASTCAM SA4 that captures in-cylinder combustion at the rate of 10000 frames per second is employed. The captured high speed video is processed to study the combustion homogeneity based on an algorithm reported in previous studies.Starting from late fuel injection timings, combustion stratification is investigated by advancing the fuel injection timings. For late start of injection (SOI), a direct link between SOI and combustion phasing is noticed. At early SOI, combustion phasing depends on both intake air temperature and SOI. In order to match the combustion phasing (CA50) of diesel,…
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