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Investigation of Steady-State RCCI Operation in a Light-Duty Multi-Cylinder Engine Using “Dieseline”

Univ of Wisconsin-Rolf Reitz
Engine Research Center UW Madison-Christopher W. Gross
Published 2017-03-28 by SAE International in United States
In an attempt to increase efficiency and lower critical and highly regulated emissions (i.e., NOx, PM and CO2) many advanced combustion strategies have been investigated. Most of the current strategies fall into the category of low temperature combustion (LTC), which allow emissions mandates to be met in-cylinder along with anticipated reduction in cost and complexity. These strategies, such as homogeneous charge compression ignition (HCCI), premixed charge compression ignition (PCCI), partially premixed combustion (PPC) and reactivity controlled compression ignition (RCCI), use early injection timings, resulting in a highly lean charge with increased specific heat ratios to improve thermal efficiency and reduce PM emissions. Lower combustion temperatures also avoid the activation of NOx formation reactions. However, the lean air/fuel ratio decreases fuel oxidation rates of CO and HC and, due to longer ignition delays with high peak pressure rise rate (PPRR) and heat release rates (HRR), confines the engine’s operating loads and speeds. A strategy to reduce these negative effects of LTC is RCCI, which generally uses two fuels with different reactivities in order to optimize ignitability…
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Development of a Third Generation Dynamic Intake Air Simulator for Single-Cylinder Test Engines

Univ of Wisconsin-John J. Moskwa
Sargent & Lundy-Mark B. Murphy
Published 2015-04-14 by SAE International in United States
This paper details the development of a new dynamic Intake Air Simulator (IAS) for use on single-cylinder test engines, where the gas dynamics are controlled to accurately simulate those on a multi-cylinder engine during transient or steady-state operation. The third generation of Intake Air Simulators (IAS3) continues a development of new technology in the Powertrain Control Research Laboratory (PCRL) that replicates the multi-cylinder engine instantaneous intake gas dynamics on the single-cylinder engine, as well as the control of other boundary conditions.This is accomplished by exactly replicating the intake runner geometry between the plenum and the engine intake valve, and dynamically controlling the instantaneous plenum pressure feeding that runner, to replicate the instantaneous multi-cylinder engine intake flow. The plenum pressure is controlled in this technology by means of six rotary valves, seven proportional valves, and the throttle valve system from the representative multi-cylinder engine. The proportional valves control the magnitude of flow through the rotary valves, and the rotary valves control the instantaneous wave form of the flow out of the plenum by means of their…
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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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Model Based Study of DeNOx Characteristics for Integrated DPF/SCR System over Cu-Zeolite

Univ of Wisconsin-Yangdongfang Yang, Christopher Rutland
Korea Institute of Machinery & Materials-Gyubaek Cho
Published 2015-04-14 by SAE International in United States
The SCR Filter simultaneously reduces NOx and Particle Matter (PM) in the exhaust and is considered an effective way to meet emission regulations. By combining the function of a Diesel Particulate Filtration (DPF) and a Selective Catalytic Reduction (SCR), the SCR Filter reduces the complexity and cost of aftertreatment systems in diesel vehicles. Moreover, it provides an effective reaction surface and potentially reduces backpressure by combining two devices into one. However, unlike traditional flow through type SCR, the deNOx reactions in the SCR Filter can be affected by the particulate filtration and regeneration process. Additionally, soot oxidation can be affected by the deNOx process.A 1-D kinetic model for integrated DPF and NH3-SCR system over Cu-zeolite catalysts was developed and validated with experimental data in previous work[1]. In the current work, the reaction kinetics, and interaction between soot and SCR reactions are analyzed to give a clear review on chemical and physical process inside the filter. Extensive studies on the effect of the NO2/NOx ratio, ANR (ammonia to NOx ratio), temperature, and SV (gas hourly space…
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Investigation of Pressure Oscillation Modes and Audible Noise in RCCI, HCCI, and CDC

Univ of Wisconsin-Martin Wissink, Derek Splitter, Arsham Shahlari, Rolf D. Reitz
Tsinghua Univ-Zhi Wang
Published 2013-04-08 by SAE International in United States
This study uses Fourier analysis to investigate the relationship between the heat release event and the frequency composition of pressure oscillations in a variety of combustion modes. While kinetically-controlled combustion strategies such as HCCI and RCCI offer advantages over CDC in terms of efficiency and NOX emissions, their operational range is limited by audible knock and the possibility of engine damage stemming from high pressure rise rates and oscillations. Several criteria such as peak pressure rise rate, ringing intensity, and various knock indices have been developed to quantify these effects, but they fail to capture all of the dynamics required to form direct comparisons between different engines or combustion strategies. Experiments were performed with RCCI, HCCI, and CDC on a 2.44 L heavy-duty engine at 1300 RPM, generating a significant diversity of heat release profiles. Fourier and statistical analyses were used to examine the effect of both the average heat release as well as cyclic variations on the frequency and amplitude of pressure oscillations, and these were compared to existing knocking criteria. The results indicate…
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A Comprehensive Combustion Model for Biodiesel-Fueled Engine Simulations

Jessica Brakora
Univ of Wisconsin-Rolf D. Reitz
Published 2013-04-08 by SAE International in United States
A comprehensive biodiesel combustion model is presented for use in multi-dimensional engine simulations. The model incorporates realistic physical properties in a vaporization model developed for multi-component fuel sprays and applies an improved mechanism for biodiesel combustion chemistry.Previously, a detailed mechanism for methyl decanoate and methyl-9-decenoate was reduced from 3299 species to 85 species to represent the components of biodiesel fuel. In this work, a second reduction was performed to further reduce the mechanism to 69 species. Steady and unsteady spray simulations confirmed that the model adequately reproduced liquid penetration observed in biodiesel spray experiments. Additionally, the new model was able to capture expected fuel composition effects with low-volatility components and fuel blend sprays penetrating further.A new biodiesel chemistry modeling strategy was implemented that utilizes n-heptane to improve ignition behavior and two biodiesel experiments were chosen to validate the model under engine operating conditions. First, a low-speed, high-load, conventional combustion experiment was simulated and the model was able to predict the performance and NOx formation seen in the experiment. Second, high-speed, low-load, low-temperature combustion conditions were…
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RCCI Engine Operation Towards 60% Thermal Efficiency

Univ of Wisconsin-Derek Splitter, Martin Wissink, Dan DelVescovo, Rolf D. Reitz
Published 2013-04-08 by SAE International in United States
The present experimental study explored methods to obtain the maximum practical cycle efficiency with Reactivity Controlled Compression Ignition (RCCI). The study used both zero-dimensional computational cycle simulations and engine experiments. The experiments were conducted using a single-cylinder heavy-duty research diesel engine adapted for dual fuel operation, with and without piston oil gallery cooling. In previous studies, RCCI combustion with in-cylinder fuel blending using port-fuel-injection of a low reactivity fuel and optimized direct-injections of higher reactivity fuels was demonstrated to permit near-zero levels of NOx and PM emissions in-cylinder, while simultaneously realizing gross indicated thermal efficiencies in excess of 56%.The present study considered RCCI operation at a fixed load condition of 6.5 bar IMEP an engine speed of 1,300 [r/min]. The experiments used a piston with a flat profile with 18.7:1 compression ratio. The results demonstrated that the indicated gross thermal efficiency could be increased by not cooling the piston, by using high dilution, and by optimizing in-cylinder fuel stratification with two fuels of large reactivity differences. The best results achieved gross indicated thermal efficiencies near…
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Effects of Biofuel Blends on RCCI Combustion in a Light-Duty, Multi-Cylinder Diesel Engine

SAE International Journal of Engines

Univ of Wisconsin-Rolf D. Reitz
Oak Ridge National Laboratory-Reed Hanson, Scott Curran, Robert Wagner
  • Journal Article
  • 2013-01-1653
Published 2013-04-08 by SAE International in United States
Reactivity Controlled Compression Ignition (RCCI) is an engine combustion strategy that utilizes in-cylinder fuel blending to produce low NOx and PM emissions while maintaining high thermal efficiency. Previous RCCI research has been investigated in single-cylinder heavy-duty engines [1, 2, 3, 4, 5, 6]. The current study investigates RCCI operation in a light-duty multi-cylinder engine over a wide number of operating points representing vehicle operation over the US EPA FTP test. Similarly, previous RCCI engine experiments have used petroleum based fuels such as ultra-low sulfur diesel fuel (ULSD) and gasoline, with some work done using high percentages of biofuels, namely E85 [7]. The current study was conducted to examine RCCI performance with moderate biofuel blends, such as E20 and B20, as compared to conventional gasoline and ULSD. The engine experiments consisted of in-cylinder fuel blending using port fuel-injection (PFI) of gasoline or E20 and early-cycle, direct-injection (DI) of ultra-low sulfur diesel (ULSD) or B20 fuel. At the selected load points, the results from RCCI combustion using biofuels and petroleum fuels are compared. Preliminary results show that…
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Particle Size and Number Emissions from RCCI with Direct Injections of Two Fuels

Univ of Wisconsin-Martin Wissink, Derek Splitter, Reed Hanson, Rolf D. Reitz
Argonne National Laboratory-Christopher Kolodziej
Published 2013-04-08 by SAE International in United States
Many concepts of premixed diesel combustion at reduced temperatures have been investigated over the last decade as a means to simultaneously decrease engine-out particle and oxide of nitrogen (NO) emissions. To overcome the trade-off between simultaneously low particle and NO emissions versus high "diesel-like" combustion efficiency, a new dual-fuel technique called Reactivity Controlled Compression Ignition (RCCI) has been researched. In the present study, particle size distributions were measured from RCCI for four gasoline:diesel compositions from 65%:35% to 84%:16%, respectively. Previously, fuel blending (reactivity control) had been carried out by a port fuel injection of the higher volatility fuel and a direct in-cylinder injection of the lower volatility fuel. With a recent mechanical upgrade, it was possible to perform injections of both fuels directly into the combustion chamber. Particle size distributions were measured at four different gasoline injection timings for each gasoline:diesel fuel reactivity blend, while the ignition-controlling diesel injection timings remained constant. Increased particle mass and number emissions were measured for increased diesel fueling and advanced in-cylinder gasoline injection timing (especially from -340 to -360°…
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Compaction-Based Deformable Terrain Model as an Interface for Real-Time Vehicle Dynamics Simulations

Univ of Wisconsin-Andrew Seidl, Dan Negrut
University of Wisconsin - Madison-Justin Madsen
Published 2013-04-08 by SAE International in United States
This paper discusses the development of a novel deformable terrain database and its use in a co-simulation environment with a multibody dynamics vehicle model. The implementation of the model includes a general tire-terrain traction model which is modular to allow for any type of tire model that supports the Standard Tire Interface[1] to operate on the terrain. This allows arbitrarily complex tire geometry to be used, which typically has a large impact on the mobility performance of vehicles operating on deformable terrains. However, this gain in generality comes at the cost that popular analytical pressure-sinkage terramechanics models cannot be used to find the normal pressure and shear stress of the contact patch. Pressure and shear stress are approximated by combining the contributions from tire normal forces, shear stresses and bulldozing forces due to soil rutting. The governing equations of the terrain are based on a soil compaction model that includes both the propagation of subsoil stresses due to vehicular loads, and the resulting visco-elastic-plastic stress/strain on the affected soil volume. Pedo transfer functions allow for…
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