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Siewert, Robert M.
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Detailed Unburned Hydrocarbon Investigations in a Highly-Dilute Diesel Low Temperature Combustion Regime

SAE International Journal of Engines

Engine Research Center, University of Wisconsin – Madison-Chad P. Koci, Youngchul Ra, Roger Krieger, Mike Andrie, David E. Foster
Powertrain Systems Research Laboratory, General Motors Research and Development Center-Robert M. Siewert, Russell P. Durrett
  • Journal Article
  • 2009-01-0928
Published 2009-04-20 by SAE International in United States
The objective of this research is a detailed investigation of unburned hydrocarbon (UHC) in a highly-dilute diesel low temperature combustion (LTC) regime. This research concentrates on understanding the mechanisms that control the formation of UHC via experiments and simulations in a 0.48L signal-cylinder light duty engine operating at 2000 r/min and 5.5 bar IMEP with multiple injections. A multi-gas FTIR along with other gas and smoke emissions instruments are used to measure exhaust UHC species and other emissions. Controlled experiments in the single-cylinder engine are then combined with three computational tools, namely heat release analysis of measured cylinder pressure, analysis of spray trajectory with a phenomenological spray model using in-cylinder thermodynamics [1], and KIVA-3V Chemkin CFD computations recently tested at LTC conditions [2]. This study looks at the effect of inlet oxygen concentration, fuel spray targeting, injection event timing, injector sac volume, rail pressure, and boost pressure which are each explored within a defined operation range in LTC. This research compliments simultaneous research which concentrates on understanding the benefits of multiple injections on engine performance…
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Multiple-Event Fuel Injection Investigations in a Highly-Dilute Diesel Low Temperature Combustion Regime

SAE International Journal of Engines

Engine Research Center, University of Wisconsin – Madison-Chad P. Koci, Youngchul Ra, Roger Krieger, Mike Andrie, David E. Foster
Powertrain Systems Research Laboratory, General Motors Research and Development Center-Robert M. Siewert, Russell P. Durrett
  • Journal Article
  • 2009-01-0925
Published 2009-04-20 by SAE International in United States
The objective of this research is a detailed investigation of multiple injections in a highly-dilute diesel low temperature combustion (LTC) regime. This research concentrates on understanding the performance and emissions benefits of multiple injections via experiments and simulations in a 0.48L signal cylinder light-duty engine operating at 2000 r/min and 5.5 bar IMEP. Controlled experiments in the single-cylinder engine are then combined with three computational tools, namely heat release analysis of measured cylinder pressure, a phenomenological spray model using in-cylinder thermodynamics [1], and KIVA-3V Chemkin CFD computations recently tested at LTC conditions [2]. This study examines the effects of fuel split distribution, injection event timing, rail pressure, and boost pressure which are each explored within a defined operation range in LTC. This research compliments simultaneous detailed unburned hydrocarbon research which concentrates on the mechanisms that control the formation of UHC during LTC engine operation [3].Engine operating conditions for low UHC/CO from previous single injection experiments are observed using split (i.e., multiple-event) injections. Fuel split is defined by the fractional percentage of total fuel injected in…
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Spray Angle and Rail Pressure Study for Low NOx Diesel Combustion

General Motors R&D Center-Robert M. Siewert
Published 2007-04-16 by SAE International in United States
The effects of varying nozzle spray angle and rail pressure on emissions and thermal efficiency each were explored using a 103-mm bore direct-injection single-cylinder diesel engine. Spray angles from 120° to 158° significantly changed the spray targeting within the 16:1 compression ratio reentrant-shaped piston bowl. At one part load operating condition injection timing was varied over a range of 15° to 30° btc to investigate pre-mixed compression ignition (PCI) combustion with 800 bar rail pressure while varying EGR to maintain a constant low NOx emission index of 0.4 g/kg. The observed trends are explained by the combined effects of spray angle and injection timing and, in particular, the calculated amount of liquid spray that misses the piston bowl is directly linked to the measured increases in HC, CO, and smoke emissions and a reduction in thermal efficiency. Rail pressure was varied from 800 to 1600 bar with a good performing narrow angle of 105° and the standard wide angle of 158°. The range of injection timing explored was expanded (0° to 30° btc) to include…
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A Phenomenological Engine Model for Direct Injection of Liquid Fuels, Spray Penetration, Vaporization, Ignition Delay, and Combustion

General Motors R&D Center-Robert M. Siewert
Published 2007-04-16 by SAE International in United States
A phenomenological engine model has been developed to study direct injection of liquid fuels in diesel and gasoline engines. Sub-models were obtained from the literature wherever possible and include those for initial drop size, droplet vaporization, and spray penetration. The progress of the injected spray, including both liquid and vapor, is visualized relative to the combustion chamber bowl boundaries and gives valuable insight on where the spray tip intersects the piston bowl surface, and whether it is in a liquid or gaseous state. The one-dimensional spray penetration used in the model is oblivious to surfaces (thus no spray-wall interactions), air motion, turbulence, and mixing with air, but is properly influenced by gas temperature and density. An ignition delay sub model, based on the sum of droplet vaporization time and reaction time, has been calibrated to experiments run at Sandia National Laboratories, and provides good results over a wide range of applications, including those for very late injection timings as used in low soot combustion (LSC), and those of very early injection where pre-mixed compression ignition…
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Investigation of Mixing and Temperature Effects on HC/CO Emissions for Highly Dilute Low Temperature Combustion in a Light Duty Diesel Engine

Powertrain Systems Research Laboratory, General Motors Research and Development Center-Russell P. Durrett, Robert M. Siewert
University of Wisconsin - Madison, Engine Research Center-Richard Opat, Youngchul Ra, Manuel A. Gonzalez D., Roger Krieger, Rolf D. Reitz, David E. Foster
Published 2007-04-16 by SAE International in United States
There is a significant global effort to study low temperature combustion (LTC) as a tool to achieve stringent emission standards with future light duty diesel engines. LTC utilizes high levels of dilution (i.e., EGR > 60% with <10%O2 in the intake charge) to reduce overall combustion temperatures and to lengthen ignition delay, This increased ignition delay provides time for fuel evaporation and reduces in-homogeneities in the reactant mixture, thus reducing NOx formation from local temperature spikes and soot formation from locally rich mixtures. However, as dilution is increased to the limits, HC and CO can significantly increase.Recent research suggests that CO emissions during LTC result from the incomplete combustion of under-mixed fuel and charge gas occurring after the premixed burn period [1, 2]1. The objective of the present work was to increase understanding of the HC/CO emission mechanisms in LTC at part-load. To do this, fluid mechanics and chemical kinetics were decoupled by selectively varying in-cylinder mixing and charge temperature to influence not only the formation of CO and HC but also their oxidation during…
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Modeling Approaches for Premixed Charge Compression Ignition Combustion

General Motors Corporation-Carl-Anders Hergart, Hardo Barths, Robert M. Siewert
Published 2005-04-11 by SAE International in United States
The Representative Interactive Flamelet (RIF) - model has established itself as a model well suited for capturing conventional non-premixed combustion in diesel engines. There are concerns about applying the concept to model combustion modes characterized by high degrees of premixing, since it is argued that the fast-chemistry assumption, on which the model is based, breaks down. However, the level of premixing at which this occurs is still not well established. In this paper the model is successfully applied to the so-called Premixed Charge Compression Ignition (PCCI) mode of combustion, characterized by relatively early injection timings, high EGR, and cooled intake air. For very advanced injection timings, an alternative modeling approach is developed. This is based on a sequential treatment of the in-cylinder processes, where the injection process and fluid dynamics are modeled using the three-dimensional CFD-code GMTEC and the chemical reactions are treated in a multi-zone chemistry code, developed at GM. The computations are compared to experiments conducted in a single-cylinder heavy-duty diesel engine.
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Evaluation of a Narrow Spray Cone Angle, Advanced Injection Timing Strategy to Achieve Partially Premixed Compression Ignition Combustion in a Diesel Engine

GM R&D and Planning-Robert M. Siewert
University of Michigan-Guntram A. Lechner, Timothy J. Jacobs, Christos A. Chryssakis, Dennis N. Assanis
Published 2005-04-11 by SAE International in United States
Simultaneous reduction of nitric oxides (NOx) and particulate matter (PM) emissions is possible in a diesel engine by employing a Partially Premixed Compression Ignition (PPCI) strategy. PPCI combustion is attainable with advanced injection timings and heavy exhaust gas recirculation rates. However, over-advanced injection timing can result in the fuel spray missing the combustion bowl, thus dramatically elevating PM emissions. The present study investigates whether the use of narrow spray cone angle injector nozzles can extend the limits of early injection timings, allowing for PPCI combustion realization. It is shown that a low flow rate, 60-degree spray cone angle injector nozzle, along with optimized EGR rate and split injection strategy, can reduce engine-out NOx by 82% and PM by 39%, at the expense of a modest increase (4.5%) in fuel consumption. This PPCI strategy has the potential for meeting upcoming stringent fuel specific NOx emission levels of less than 1 g/kg-fuel and fuel specific PM levels less than 0.25 g/kg-fuel.
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Modifying an Intake Manifold to Improve Cylinder-to-Cylinder EGR Distribution in a DI Diesel Engine Using Combined CFD and Engine Experiments

GM R&D and Planning-Robert M. Siewert, Roger B. Krieger, Mark S. Huebler, Prafulla C. Baruah, Bahram Khalighi
Opel Powertrain GmbH-Markus Wesslau
Published 2001-09-24 by SAE International in United States
Improved cylinder-to-cylinder distribution of EGR in a 2-L Direct-Injection (DI) Diesel engine has been identified as one enabler to help reach more stringent emission standards. Through a combined effort of modeling, design, and experiment, two manifolds were developed that improve EGR distribution over the original manifold while minimizing design changes to engine components or interfering with the many varied vehicle platform installations.One of the modified manifolds, an elevated EGR entry (EEE) approach, provided a useful improvement over the original design that meet Euro-II emission standards, and has been put into production as it enabled meeting the Euro III emissions requirements a year early. The second revision, the distributed EGR entry (DEE) design, showed potential for further improvement in EGR distribution. This design has two EGR outlets rather than the one used in the original and EEE manifolds, and was first identified by modeling to be a promising concept. Using rapid prototype parts with variable geometry, over 40 variations of the DEE concept were studied experimentally in an attempt to identify an improved configuration. Parallel CFD…
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Diesel Engines: One Option to Power Future Personal Transportation Vehicles

General Motors Research and Development Center-Roger B. Krieger, Robert M. Siewert, John A. Pinson, Nicholas E. Gallopoulos, David L. Hilden, David R. Monroe, Rodney B. Rask, Arun S. P. Solomon
General Motors Technical Development Center Europe-Peter Zima
Published 1997-08-06 by SAE International in United States
In the twenty-first century, exhaust emission control will remain a major technical challenge especially as additional pressures for fuel and energy conservation mount. To address these needs, a wide variety of engine and powertrain options must be considered. For many reasons, the piston engine will remain the predominant engine choice in the twenty-first century, especially for conventional and/or parallel hybrid drive trains. Emissions constraints favor the conventional port fuel-injected gasoline engine with 3-way exhaust catalyst, while energy conservation favors direct-injection gasoline and diesel engines. As a result of recent technological progress from a competitive European market, diesels, and most recently, direct-injection (DI) diesels now offer driveability and performance characteristics competitive with those of gasoline engines. In addition, DI diesels offer the highest fuel efficiency. However, DI diesels will be strongly challenged by the emissions standards expected in the 2004-2005 period (e.g., Tier 2/ULEV and EC Stage IV). The technologies under development to enable compliance with these standards include optimized combustion chambers, high-pressure fuel-injection with electronic rate-shape control, and highly optimized systems to maintain high levels…
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Engine Emissions and Emissions Measurement

Robert M. Siewert
  • Special Publication (SP)
  • SP-1161
Published 1996-02-01 by SAE International in United States
This publication provides a basis for new and exciting knowledge and techniques for meeting complex measurement challenges. Application of such techniques is essential for measuring understanding, and meeting the ever-tightening levels legislated for non-gaseous emissions from diesel engines. Contents include: emission system upgrades for older vehicles; mixture formation during cold starting and warm-up in spark ignition engines; improved control of EGR during speed/load transients; white smoke emissions under cold start of diesel engines; feasibility of remote sensing of particulate emissions from heavy duty vehicles; off-cycle exhaust emissions from modern passenger cars with properly-functioning emissions controls; and emissions from modern passenger cars with malfunctioning emissions controls.