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Comparative Study on the Effects of Inlet Heating, Inlet Boosting, and Double-Injection Strategy on Partially Premixed Combustion

Eindhoven University Of Technology-Jinlin Han, Shuli Wang, Bart Somers
Published 2019-04-02 by SAE International in United States
Partially premixed combustion (PPC) is a low temperature combustion (LTC) concept which can relieve soot-NOx trade-off without sacrificing efficiency. However, at low load operating range, PPC with low reactivity fuel generally undergoes long ignition delay, which gives rise to high pressure rise rate, fast heat release and even misfires. To solve these problems and maintain high efficiency simultaneously, inlet heating, inlet boosting and double-injection strategy are experimentally investigated in a heavy-duty engine. BH80 (80vol% n-butanol and 20vol% n-heptane) are blended and tested at 8 bar gIMEP in PPC mode. Inlet heating (from 40oC to 100oC), inlet boosting (from 1.4 bar to 2.5 bar) and a double-injection strategy (pilot/main injection) are attempted to reduce the maximum pressure rise rate (PRRmax). The results show that all three methods can achieve negligible soot emissions. Moreover, a correlation between global temperature at TDC and ignition delay is noticed. In other words, high global temperature after compression stroke makes BH80 easier to ignite. As a consequence, the ignition delay shortens and the maximum pressure rise rate decreases. Compared to inlet…
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Performance and Emission Studies in a Heavy-Duty Diesel Engine Fueled with an N-Butanol and N-Heptane Blend

Eindhoven University of Technology-Shuli Wang, Jinlin Han, Bart Somers
Published 2019-04-02 by SAE International in United States
N-butanol, as a biomass-based renewable fuel, has many superior fuel properties. It has a higher energy content and cetane number than its alcohol competitors, methanol and ethanol. Previous studies have proved that n-butanol has the capability to achieve lower emissions without sacrifice on thermal efficiency when blended with diesel. However, most studies on n-butanol are limited to low blending ratios, which restricts the improvement of emissions. In this paper, 80% by volume of n-butanol was blended with 20% by volume of n-heptane (namely BH80). The influences of various engine parameters (combustion phasing, EGR ratio, injection timing and intake pressure, respectively) on its combustion and emission characteristics are tested at different loads. The results showed that when BH80 uses more than 40% EGR, the emitted soot and nitrogen oxides (NOx) emissions are below the EURO VI legislation. Carbon monoxide (CO) decreases and NOx emissions increase with the increase of injection pressure. It was also found that for a constant lambda (1.55) the stable operating load range of BH80 is limited to relatively high load (>8 bar…
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Effects of Different Injection Strategies and EGR on Partially Premixed Combustion

Eindhoven University of Technology-Jinlin Han, Shuli Wang, Bart Somers
Published 2018-09-10 by SAE International in United States
Premixed Charge Compression Ignition concepts are promising to reduce NOx and soot simultaneously and keeping a high thermal efficiency. Partially premixed combustion is a single fuel variant of this new combustion concepts applying a fuel with a low cetane number to achieve the necessary long ignition delay. In this study, multiple injection strategies are studied in the partially premixed combustion approach to reach stable combustion and ultra-low NOx and soot emission at 15.5 bar gross indicated mean effective pressure. Three different injection strategies (single injection, pilot-main injection, main-post injection) are experimentally investigated on a heavy duty compression ignition engine. A fuel blend (70 vol% n-butanol and 30 vol% n-heptane) was tested. The effects of different pilot and post-injection timing, as well as Exhaust-gas Recirculation rate on different injection strategies investigated. All the measurements were performed at the same load, combustion phasing, lambda and engine speed. The results show that all three injection strategies produced ultra-low soot emission, while less NOx emission was noticed for pilot-main injection because of less diffusion combustion mode. Pilot-main injection strategy…
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Investigation of Late Stage Conventional Diesel Combustion - Effect of Additives

Eindhoven University of Technology-P.C. Bakker, Robbert Willems, Nico Dam, Bart Somers
Shell Global Solutions (UK)-Caroline Wakefield, Mark Brewer, Roger Cracknell
Published 2018-09-10 by SAE International in United States
The accepted model of conventional diesel combustion [1] assumes a rich premixed flame slightly downstream of the maximum liquid penetration. The soot generated by this rich premixed flame is burnt out by a subsequent diffusion flame at the head of the jet. Even in situations in which the centre of combustion (CA50) is phased optimally to maximize efficiency, slow late stage combustion can still have a significant detrimental impact on thermal efficiency.Data is presented on potential late-stage combustion improvers in a EURO VI compliant HD engine at a range of speed and load points. The operating conditions (e.g. injection timings, EGR levels) were based on a EURO VI calibration which targets 3 g/kWh of engine-out NOx. Rates of heat release were determined from the pressure sensor data. To investigate late stage combustion, focus was made on the position in the cycle at which 90% of the fuel had combusted (CA90).An EN590 compliant fuel was tested. To this fuel was added an organic compound, commonly encountered in sunscreen products, that was designed to absorb ultraviolet light.…
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Heavy-Duty Diesel Engine Spray Combustion Processes: Experiments and Numerical Simulations

Eindhoven University of Technology-Noud Maes, Nico Dam, Bart Somers
FPT Motorenforschung AG-Gilles Hardy
Published 2018-09-10 by SAE International in United States
A contemporary approach for improving and developing the understanding of heavy-duty Diesel engine combustion processes is to use a concerted effort between experiments at well-characterized boundary conditions and detailed, high-fidelity models. In this paper, combustion processes of n-dodecane fuel sprays under heavy-duty Diesel engine conditions are investigated using this approach. Reacting fuel sprays are studied in a constant-volume pre-burn vessel at an ambient temperature of 900 K with three reference cases having specific combinations of injection pressure, ambient density and ambient oxygen concentration (80, 150 & 160 MPa - 22.8 & 40 kg/m3-15 & 20.5% O2). In addition to a free jet, two different walls were placed inside the combustion vessel to study flame-wall interaction. Experimentally, low- and high-temperature reaction product distributions are imaged simultaneously using single-shot planar laser-induced fluorescence (PLIF) of formaldehyde and high-speed line-of-sight imaging of the chemically-excited hydroxyl radical (OH*). Interference of soot incandescence in experimental OH* recordings is assessed to improve interpretation of the results. Interference by poly-cyclic aromatic hydrocarbon (PAH) LIF and soot radiation is mostly evaded by evaluating flame…
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The Impact of Operating Conditions on Post-Injection Efficacy; a Study Using Design-of-Experiments

Eindhoven University of Technology-Robbert Willems, P.C. Bakker, Bart Somers
Toyota Motorsport GmbH-Robbert Dreezen
Published 2018-04-03 by SAE International in United States
Post-injection strategies prove to be a valuable option for reducing soot emission, but experimental results often differ from publication to publication. These discrepancies are likely caused by the selected operating conditions and engine hardware in separate studies. Efforts to optimize not only engine-out soot, but simultaneously fuel economy and emissions of nitrogen oxides (NOx) complicate the understanding of post-injection effects even more. Still, the large amount of published work on the topic is gradually forming a consensus. In the current work, a Design-of-Experiments (DoE) procedure and regression analysis are used to investigate the influence of various operating conditions on post-injection scheduling and efficacy. The study targets emission reductions of soot and NOx, as well as fuel economy improvements. Experiments are conducted on a heavy-duty compression ignition engine at three load-speed combinations. Regression analysis shows that the eventual decrease in engine-out soot heavily depends on the air-excess ratio. This observation supports the suggestion that enhanced late-cycle mixing of fuel and oxidizer is an important contributor to observed soot reductions. Furthermore, simultaneous reductions in emissions of NOx…
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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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