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Reitz, Rolf D.
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A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

SAE International Journal of Engines

Argonne National Laboratory-Yuanjiang Pei, Sibendu Som
ETH Zurich-Daniele Farrace, Sushant S. Pandurangi, Yuri M. Wright
  • Journal Article
  • 2016-01-0734
Published 2016-04-05 by SAE International in United States
The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered.
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ERRATUM: The Development of an Ignition Delay Correlation for PRF Fuel Blends from PRF0 (n-Heptane) to PRF100 (iso-Octane)

SAE International Journal of Engines

University of Wisconsin-Dan DelVescovo, Sage Kokjohn, Rolf D. Reitz
  • Journal Article
  • 2016-01-0551.01
Published 2016-04-05 by SAE International in United States
In Equation 10, there should be a plus sign between the first summation term and the quantity in brackets. The acceleration of the participant's vehicle was varied from −0.04 m/s2 to +0.06 m/s2 linearly as a function of the angle of the gas pedal with a 0.1-second delay.
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Measured and Predicted Soot Particle Emissions from Natural Gas Engines

Engine Research Center, University of Wisconsin-Rolf D. Reitz
Politecnico di Bari-Riccardo Amirante, Elia Distaso, Paolo Tamburrano
Published 2015-09-06 by SAE International in United States
Due to the new challenge of meeting number-based regulations for particulate matter (PM), a numerical and experimental study has been conducted to better understand particulate formation in engines fuelled with compressed natural gas. The study has been conducted on a Heavy-Duty, Euro VI, 4-cylinder, spark ignited engine, with multipoint sequential phased injection and stoichiometric combustion. For the experimental measurements two different instruments were used: a condensation particle counter (CPC) and a fast-response particle size spectrometer (DMS) the latter able also to provide a particle size distribution of the measured particles in the range from 5 to 1000 nm. Experimental measurements in both stationary and transient conditions were carried out. The data using the World Harmonized Transient Cycle (WHTC) were useful to detect which operating conditions lead to high numbers of particles. Then a further transient test was used for a more detailed and deeper analysis. Finally 3-D Computational Fluid Dynamics (CFD) simulations were performed and the numerical results obtained were compared to particle size distributions (PSDs) derived from the experimental measurements carried out in stationary…
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Applying Advanced CFD Analysis Tools to Study Differences between Start-of-Main and Start-of-Post Injection Flow, Temperature and Chemistry Fields Due to Combustion of Main-Injected Fuel

SAE International Journal of Engines

Pennsylvania State University-Jacqueline O'Connor
Sandia National Laboratories-Mark P. B. Musculus
  • Journal Article
  • 2015-24-2436
Published 2015-09-06 by SAE International in United States
This paper is part of a larger body of experimental and computational work devoted to studying the role of close-coupled post injections on soot reduction in a heavy-duty optical engine. It is a continuation of an earlier computational paper. The goals of the current work are to develop new CFD analysis tools and methods and apply them to gain a more in depth understanding of the different in-cylinder environments into which fuel from main- and post-injections are injected and to study how the in-cylinder flow, thermal and chemical fields are transformed between start of injection timings.The engine represented in this computational study is a single-cylinder, direct-injection, heavy-duty, low-swirl engine with optical components. It is based on the Cummins N14, has a cylindrical shaped piston bowl and an eight-hole injector that are both centered on the cylinder axis. The fuel used was n-heptane and the engine operating condition was light load at 1200 RPM.The in-cylinder processes investigated are typical and include fuel injection and the subsequent growth of a largely non-combusting fuel-rich vapor jet, pre-mixed burn…
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Numerical Study of RCCI and HCCI Combustion Processes Using Gasoline, Diesel, iso-Butanol and DTBP Cetane Improver

SAE International Journal of Engines

Tianjin Univ.-Mingfa Yao
Univ. of Wisconsin-Dan DelVescovo, Rolf D. Reitz
  • Journal Article
  • 2015-01-0850
Published 2015-04-14 by SAE International in United States
Reactivity Controlled Compression Ignition (RCCI) has been shown to be an attractive concept to achieve clean and high efficiency combustion. RCCI can be realized by applying two fuels with different reactivities, e.g., diesel and gasoline. This motivates the idea of using a single low reactivity fuel and direct injection (DI) of the same fuel blended with a small amount of cetane improver to achieve RCCI combustion. In the current study, numerical investigation was conducted to simulate RCCI and HCCI combustion and emissions with various fuels, including gasoline/diesel, iso-butanol/diesel and iso-butanol/iso-butanol+di-tert-butyl peroxide (DTBP) cetane improver. A reduced Primary Reference Fuel (PRF)-iso-butanol-DTBP mechanism was formulated and coupled with the KIVA computational fluid dynamic (CFD) code to predict the combustion and emissions of these fuels under different operating conditions in a heavy duty diesel engine. The results show that RCCI combustion is achievable by applying a single low reactivity fuel combined with small amount of DTBP cetane improver over wide operating conditions, and that the performance of the iso-butanol-DTBP fuel is comparable to that of gasoline-diesel and iso-butanol-diesel…
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Direct Dual Fuel Stratification, a Path to Combine the Benefits of RCCI and PPC

SAE International Journal of Engines

University of Wisconsin-Martin Wissink, Rolf D. Reitz
  • Journal Article
  • 2015-01-0856
Published 2015-04-14 by SAE International in United States
Control of the timing and magnitude of heat release is one of the biggest challenges for premixed compression ignition, especially when attempting to operate at high load. Single-fuel strategies such as partially premixed combustion (PPC) use direct injection of gasoline to stratify equivalence ratio and retard heat release, thereby reducing pressure rise rate and enabling high load operation. However, retarding the heat release also reduces the maximum work extraction, effectively creating a tradeoff between efficiency and noise. Dual-fuel strategies such as reactivity controlled compression ignition (RCCI) use premixed gasoline and direct injection of diesel to stratify both equivalence ratio and fuel reactivity, which allows for greater control over the timing and duration of heat release. This enables combustion phasing closer to top dead center (TDC), which is thermodynamically favorable. However, the main control mechanism in RCCI is the ratio of the two fuels, and the diesel fraction typically reaches zero before full load is achieved. We propose a new strategy that effectively combines the benefits of RCCI and PPC by injecting both gasoline and diesel…
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Load Limit Extension in Pre-Mixed Compression Ignition Using a 2-Zone Combustion System

SAE International Journal of Engines

Oak Ridge National Laboratory-Adam Dempsey, Scott Curran
Wisconsin Engine Research Consultants, LLC-Michael Bergin, Rolf D. Reitz, Christopher Rutland
  • Journal Article
  • 2015-01-0860
Published 2015-04-14 by SAE International in United States
A novel 2-zone combustion system was examined at medium load operation consistent with loads in the light duty vehicle drive cycle (7.6 bar BMEP and 2600 rev/min). Pressure rise rate and noise can limit the part of the engine map where pre-mixed combustion strategies such as HCCI or RCCI can be used. The present 2-zone pistons have an axial projection that divides the near TDC volume into two regions (inner and outer) joined by a narrow communication channel defined by the squish height. Dividing the near TDC volume provides a means to prepare two fuel-air mixtures with different ignition characteristics. Depending on the fuel injection timing, the reactivity of the inner or outer volume can be raised to provide an ignition source for the fuel-air mixture in the other, less reactive volume.Multi-dimensional CFD modeling was used to design the 2-zone piston geometry examined in this study. For experimental evaluation of the design, the geometry was applied to a GM 1.9L ZDTH in-line 4-cylinder engine equipped for dual fuel RCCI operation. The intake system was modified…
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Use of Multiple Injection Strategies to Reduce Emission and Noise in Low Temperature Diesel Combustion

Ford Forschungszentrum Aachen GmbH-Werner Willems
Ford Motor Co-Eric Kurtz
Published 2015-04-14 by SAE International in United States
The low temperature combustion concept is very attractive for reducing NOx and soot emissions in diesel engines. However, it has potential limitations due to higher combustion noise, CO and HC emissions. A multiple injection strategy is an effective way to reduce unburned emissions and noise in LTC. In this paper, the effect of multiple injection strategies was investigated to reduce combustion noise and unburned emissions in LTC conditions. A hybrid surrogate fuel model was developed and validated, and was used to improve LTC predictions. Triple injection strategies were considered to find the role of each pulse and then optimized. The split ratio of the 1st and 2nd pulses fuel was found to determine the ignition delay. Increasing mass of the 1st pulse reduced unburned emissions and an increase of the 3rd pulse fuel amount reduced noise. It is concluded that the pulse distribution can be used as a control factor for emissions and noise.
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CFD Study of Soot Reduction Mechanisms of Post-Injection in Spray Combustion

Univ of Wisconsin-Zongyu Yue, Randy Hessel, Rolf D. Reitz
Published 2015-04-14 by SAE International in United States
The application of close-coupled post injections in diesel engines has been proven to be an effective in-cylinder strategy for soot reduction, without much fuel efficiency penalty. But due to the complexity of in-cylinder combustion, the soot reduction mechanism of post-injections is difficult to explain. Accordingly, a simulation study using a three dimensional computational fluid dynamics (CFD) model, coupled with the SpeedChem chemistry solver and a semi-detailed soot model, was carried out to investigate post-injection in a constant volume combustion chamber, which is more simple and controllable with respect to the boundary conditions than an engine.A 2-D axisymmetric mesh of radius 2 cm and height 5 cm was used to model the spray. Post-injection durations and initial oxygen concentrations were swept to study the efficacy of post-injection under different combustion conditions. Several factors that influence the evolution of soot were analyzed, including the distribution of temperature, oxygen concentration, and OH radicals. Additionally, newly developed analysis methods, which can quantify and visualize soot formation, soot oxidation, soot from the main-injection and soot from post-injections individually, were also…
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Isobutanol as Both Low Reactivity and High Reactivity Fuels with Addition of Di-Tert Butyl Peroxide (DTBP) in RCCI Combustion

SAE International Journal of Fuels and Lubricants

University of Wisconsin-Dan DelVescovo, Hu Wang, Martin Wissink, Rolf D. Reitz
  • Journal Article
  • 2015-01-0839
Published 2015-04-14 by SAE International in United States
Engine experiments and multi-dimensional modeling were used to explore the effects of isobutanol as both the high and low reactivity fuels in Reactivity Controlled Compression Ignition (RCCI) Combustion. Three fuel combinations were examined; EEE/diesel, isobutanol/diesel, and isobutanol/isobutanol+DTBP (di-tert butyl peroxide). In order to assess the relative performance of the fuel combinations of interest under RCCI operation, the engine was operated under conditions representative of typical low temperature combustion (LTC). A net load of 6 bar indicated mean effective pressure (IMEP) was chosen because it provides a wide operable range of equivalence ratios and combustion phasings without excessively high peak pressure rise rates (PPRR). The engine was operated under various intake pressures with global equivalence ratios from 0.28-0.36, and various combustion phasings (defined by 50% mass fraction burned-CA50) from about 1.5 to about 10 deg after top dead center (ATDC). Combustion phasing was varied by scaling the direct-injected fuel quantity appropriately.Due to isobutanol's high octane number, a significantly larger quantity of direct-injected fuel was required to match combustion phasing, resulting in higher NOx emissions and decreased…
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