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Ramped Versus Square Injection Rate Experiments in a Heavy-Duty Diesel Engine

DAF Trucks NV-Bogdan Albrecht
Delphi Technologies-Tony Simpson
  • Technical Paper
  • 2020-01-0300
To be published on 2020-04-14 by SAE International in United States
CO2 regulations on heavy-duty transport are introduced in essentially all markets within the next decade, in most cases in several phases of increasing stringency. To cope with these mandates, developers of engines and related equipment are aiming to break new ground in the fields of combustion, fuel and hardware technologies. In this work, a novel diesel fuel injector, Delphi’s DFI7, is utilized to experimentally investigate and compare the performance of ramped injection rates versus traditional square fueling profiles. The aim is specifically to shift the efficiency and NOx tradeoff to a more favorable position. The design of experiments methodology is used in the tests, along with statistical techniques to analyze the data. Results show that ramped and square rates - after optimization of fueling parameters - produce comparable gross indicated efficiencies. For the highest engine speed tested, ramped profiles attain these efficiency values at considerably lower NOx levels. Particulate matter emissions, on the other hand, are generally lower with the use of square profiles. Heat release analysis further reveals that ignition delays in ramped rate…
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Identifying the driving processes of Diesel spray injection through mixture fraction and velocity field measurements at ECN Spray A

Eindhoven University of Technology-Bart Somers
IFP Energies Nouvelles-Louis-Marie Malbec, Gilles Bruneaux
  • Technical Paper
  • 2020-01-0831
To be published on 2020-04-14 by SAE International in United States
Diesel spray mixture formation is investigated at target conditions using multiple diagnostics and laboratories. High speed Particle Image Velocimetry (PIV) is used to measure the velocity field inside and outside the jet simultaneously with a new frame straddling synchronisation scheme. The PIV measurements are carried out in the Engine Combustion Network Spray A target conditions, enabling direct comparisons with mixture fraction measurements previously performed in the same conditions, and forming a unique database at diesel conditions. A 1D spray model, based upon mass and momentum exchange between axial control volumes and near-Gaussian velocity and mixture fraction profiles is evaluated against the data. The 1D spray model quantitatively predicts the main spray characteristics (average mixture fraction and velocity fields) within the measurement uncertainty for a wide range of parametric variations, verifying that a Diesel spray becomes momentum controlled and has a Gaussian profile. A required input to the model is the jet angle, which is obtained experimentally. Although an expected result for a gas jet, this is the first time that combined datasets of velocity and…
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Computational modeling of Diesel spray combustion with multiple injections

Eindhoven University of Technology-Noud Maes, Bart Somers
Politecnico di Milano-Qiyan Zhou, Tommaso Lucchini, Gianluca D'Errico
  • Technical Paper
  • 2020-01-1155
To be published on 2020-04-14 by SAE International in United States
Multiple injection strategies are commonly used in conventional Diesel engines due to the flexibility for optimizing heat-release timing with a consequent improvement in fuel economy and engine-out emissions, which is also desirable in low temperature combustion (LTC) engine since it offers the potential to reduce UHC and CO emissions. To better utilize these benefits and find optima calibrations of split strategies, it is imperative that the fundamental processes of multiple injection combustion are understood and CFD models accurately describe the flow dynamics and combustion characteristics between different injection events. To this end, this work is dedicated to the identification of suitable methodologies to predict the multiple injection combustion process. Two different approaches: Representative Interactive Flamelet model (RIF) employing different numbers of flamelets and Tabulated Flamelet Progress Variable (TFPV) are compared and Spray A conditions with multiple injections of Engine Combustion Network are simulated using the RANS methods with both standard k-ε and k-ω SST models. Evaluations of different turbulence and combustion models are carried out by comparing computed and measured data in terms of the…
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Effects of butanol isomers on the combustion and emission characteristics of a heavy-duty engine in RCCI mode

Eindhoven University of Technology-Jinlin Han, Bart Somers
  • Technical Paper
  • 2020-01-0307
To be published on 2020-04-14 by SAE International in United States
Butanol is one of the potential alternative biofuels due to its similarities with gasoline and low sooting tendency. In this paper, three butanol isomers (n-butanol, iso-butanol, and tert-butanol) are used as low reactive fuel while n-heptane is used as high reactive fuel in a heavy-duty engine running in RCCI mode. This work investigates the influences of butanol structure on combustion performance and emission characteristics of RCCI combustion concepts. The tested load ranges from 4 bar to 12 bar gIMEP in a step of 2 bar. Since the reactivity of the three isomers can be sequenced by n-butanol > tert-butanol> iso-butanol, different EGR rate and direct injection strategies are applied. N-butanol and tert-butanol require double direct injection and highest EGR rate to maintain a proper combustion phasing. However, iso-butanol yields in ultra-low NOx and soot emissions up to 8 bar gIMEP with single direct injection and 0% EGR due to the higher octane rating. All three butanol isomers display increased peak cylinder pressure and pressure rise rate as the load increases. Specifically, n-butanol results in 28.2…
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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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