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Izadi Najafabadi, Mohammad
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Combustion Homogeneity and Emission Analysis during the Transition from CI to HCCI for FACE I Gasoline

Eindhoven University Of Technology-Bart Somers
King Abdullah University of Science & Tech-S. Vedharaj, R Vallinayagam, Yanzhao An, Bengt Johansson
Published 2017-10-08 by SAE International in United States
Low temperature combustion concepts are studied recently to simultaneously reduce NOX and soot emissions. Optical studies are performed to study gasoline PPC in CI engines to investigate in-cylinder combustion and stratification. It is imperative to perform emission measurements and interpret the results with combustion images. In this work, we attempt to investigate this during the transition from CI to HCCI mode for FACE I gasoline (RON = 70) and its surrogate, PRF70. The experiments are performed in a single cylinder optical engine that runs at a speed of 1200 rpm. Considering the safety of engine, testing was done at lower IMEP (3 bar) and combustion is visualized using a high-speed camera through a window in the bottom of the bowl.From the engine experiments, it is clear that intake air temperature requirement is different at various combustion modes to maintain the same combustion phasing. While a fixed intake air temperature is required at HCCI condition, it varies at PPC and CI conditions between FACE I gasoline and PRF70. Three zones are identified 1) SOI = -180…
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Analysis of Transition from HCCI to CI via PPC with Low Octane Gasoline Fuels Using Optical Diagnostics and Soot Particle Analysis

Eindhoven University of Technology-Bart Somers
King Abdullah University of Science & Tech-Yanzhao An, R Vallinayagam, S Vedharaj, Jean-Baptiste Masurier, Alaaeldin Dawood, Bengt Johansson
Published 2017-10-08 by SAE International in United States
In-cylinder visualization, combustion stratification, and engine-out particulate matter (PM) emissions were investigated in an optical engine fueled with Haltermann straight-run naphtha fuel and corresponding surrogate fuel. The combustion mode was transited from homogeneous charge compression ignition (HCCI) to conventional compression ignition (CI) via partially premixed combustion (PPC). Single injection strategy with the change of start of injection (SOI) from early to late injections was employed. The high-speed color camera was used to capture the in-cylinder combustion images. The combustion stratification was analyzed based on the natural luminosity of the combustion images. The regulated emission of unburned hydrocarbon (UHC), carbon monoxide (CO) and nitrogen oxides (NOX) were measured to evaluate the combustion efficiency together with the in-cylinder rate of heat release. Soot mass concentration was measured and linked with the combustion stratification and the integrated red channel intensity of the high-speed images for the soot emissions. The nucleation nanoscale particle number and the particle size distribution were sampled to understand the effect of combustion mode switch.
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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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Effects of Injection Timing on Fluid Flow Characteristics of Partially Premixed Combustion Based on High-Speed Particle Image Velocimetry

SAE International Journal of Engines

Dantec Dynamics A/S-Hua Wang
Eindhoven University Of Technology-Mohammad Izadi Najafabadi, Bart Somers, Nico Dam
  • Journal Article
  • 2017-01-0744
Published 2017-03-28 by SAE International in United States
Partially Premixed Combustion (PPC) is a promising combustion concept ,based on judicious tuning of the charge stratification, to meet the increasing demands of emission legislation and to improve fuel efficiency. Longer ignition delays of PPC in comparison with conventional diesel combustion provide better fuel/air mixture which decreases soot and NOx emissions. Moreover, a proper injection timing and strategy for PPC can improve the combustion stability as a result of a higher level of fuel stratification in comparison with the Homogeneous Charge Compression Ignition (HCCI) concept. Injection timing is the major parameter with which to affect the level of fuel and combustion stratification and to control the combustion phasing and the heat release behavior. The scope of the present study is to investigate the fluid flow characteristics of PPC at different injection timings. To this end, high-speed Particle Image Velocimetry (PIV) is implemented in a light-duty optical engine to measure fluid flow characteristics, including the flow fields, mean velocity and cycle-resolved turbulence, inside the piston bowl as well as the squish region with a temporal resolution…
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Numerical Investigation of PPCI Combustion at Low and High Charge Stratification Levels

Eindhoven University of Technology-Mohammad Izadi Najafabadi, Bart Somers
Politecnico di Milano-Amin Maghbouli, Tommaso Lucchini, Gianluca D'Errico
Published 2017-03-28 by SAE International in United States
Partially premixed compression ignition combustion is one of the low temperature combustion techniques which is being actively investigated. This approach provides a significant reduction of both soot and NOx emissions. Comparing to the homogeneous charge compression ignition mode, PPCI combustion provides better control on ignition timing and noise reduction through air-fuel mixture stratification which lowers heat release rate compared to other advanced combustion modes. In this work, CFD simulations were conducted for a low and a high air-fuel mixture stratification cases on a light-duty optical engine operating in PPCI mode. Such conditions for PRF70 as fuel were experimentally achieved by injection timing and spray targeting at similar thermodynamic conditions. After validating the computed results of cylinder pressure, apparent heat release rate, and OH* spatial distributions, differences in engine thermal load and mixture fraction distributions at first stage and second stage ignition were compared. Assuming similar second stage ignition timing which is provided by intake air heating, experimental and simulation results reveal that the time between first and second stage ignition shortens and combustion phases to…
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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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Ignition Sensitivity Study of Partially Premixed Combustion by Using Shadowgraphy and OH* Chemiluminescence Methods

Eindhoven University of Technology-Mohammad Izadi Najafabadi, Nico Dam, Bart Somers
Lund University-Bengt Johansson
Published 2016-04-05 by SAE International in United States
Partially Premixed Combustion (PPC) is a promising combustion concept for future IC engines. However, controllability of PPC is still a challenge and needs more investigation. The scope of the present study is to investigate the ignition sensitivity of PPC to the injection timing at different injection pressures. To better understand this, high-speed shadowgraphy is used to visualize fuel injection and evaporation at different Start of Injections (SOI). Spray penetration and injection targeting are derived from shadowgraphy movies. OH* chemiluminescence is used to comprehensively study the stratification level of combustion which is helpful for interpretation of ignition sensitivity behavior. Shadowgraphy results confirm that SOI strongly affects the spray penetration and evaporation of fuel. However, spray penetration and ignition sensitivity are barely affected by the injection pressure. There is a critical SOI range, in which a significant amount of fuel is trapped in the crevice volume. Injection in this critical range has a negative influence on the combustion efficiency and ignition sensitivity. Impingement of liquid fuel on the piston crown advances the combustion phasing by providing higher…
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Validation of a Reduced Chemical Mechanism Coupled to CFD Model in a 2-Stroke HCCI Engine

Eindhoven University of Technology-Mohammad Izadi Najafabadi, Bart Somers
Universiti Putra Malaysia-Abdul Aziz Nuraini
Published 2015-04-14 by SAE International in United States
Homogeneous Charge Compression Ignition (HCCI) combustion technology has demonstrated a profound potential to decrease both emissions and fuel consumption. In this way, the significance of the 2-stroke HCCI engine has been underestimated as it can provide more power stroke in comparison to a 4-stroke engine. Moreover, the mass of trapped residual gases is much larger in a 2-stroke engine, causing higher initial charge temperatures, which leads to easier auto-ignition. For controlling 2-stroke HCCI engines, it is vital to find optimized simulation approaches of HCCI combustion with a focus on ignition timing. In this study, a Computational Fluid Dynamic (CFD) model for a 2-stroke gasoline engine was developed coupled to a semi-detailed chemical mechanism of iso-octane to investigate the simulation capability of the considered chemical mechanism and the effects of different simulation parameters such as the turbulence model, grid density and time step size. The validation of numerical results was carried using an experimental study on the 2-stroke engine that was modified to operate in HCCI mode. Results confirm that the considered iso-octane chemical mechanism is…
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