bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Fuel Spray Vapor Distribution With Large Eddy Simulation of Multiple Realizations
Authors: Senecal P. K. , Mitra S. , Pomraning E. , Xue Q. , Som S. , Banerjee S. , Hu B. , Liu K. , Rajamohan D. , Deur J. M. 
Published: December 2014

A state-of-the-art spray modeling methodology, recently presented by Senecal et al. [1, 2, 3], is applied to Large Eddy Simulations (LES) of vaporizing sprays. Simulations of non-combusting Spray H (n-heptane fuel) from the Engine Combustion Network are performed. Adaptive Mesh Refinement (AMR) cell sizes of 0.03125 mm to 0.25 mm are utilized to further demonstrate grid convergence of the Dynamic Structure LES model for diesel sprays.
Twenty-eight different realizations are simulated by changing the random number seed used in the spray submodels. Multi-realization (ensemble) averaging, which has been shown to be necessary when comparing to local spray measurements, is performed. Global quantities such as liquid and vapor penetration are compared, as well as local mean mixture fraction and mixture fraction standard deviation. The results suggest that the current model does a reasonable job predicting the major features of the n-heptane spray when appropriate grid resolution is utilized.
In-Cylinder NOx Reduction Using Different Camshaft Timings on Diesel Engines
Authors: Comitre Lucas , Lehmann Flavio G. 
Published: December 2014

Over time, environmental protection standards have become more strict and complex. Nitrogen oxides (NOx) are regulated pollutants produced by combustion in a diesel engine. In this project, camshaft timing modifications were studied as a way of reducing NOx emission levels while using low cost hardware. Different valve timing strategies were proposed and modelled using engine simulation. This project was based on two concepts. The first was to open the intake valve during the exhaust stroke, thus expelling burnt gases from the cylinder into the intake manifold and then later re-admitting these gases into the cylinder during the intake stroke of the next cycle. The second was to open the exhaust valve during the intake stroke, allowing burnt gases from the exhaust manifold to enter the cylinder at the same time as the fresh charge enters. Both technologies studied were able to recirculate the exhaust gases without an external EGR system. The EGR amount was controlled by either an intake throttle or an exhaust throttle. The amount of EGR was predicted using engine simulation. The brake-specific fuel consumption (BSFC) and brake-specific NOx (BSNOx) trade off was the main criterion used to select the best technology, although other features such as predicted manifold pressures and engine-out soot were also considered.
The results indicate that, by using increased amounts of EGR while varying the intake or exhaust throttle position, NOx emissions can be reduced with a slight BSFC penalty. These methods are thus a low cost means of reducing engine-out NOx emissions.
Partial Flow DPF System for Large Bore or High Power Applications
Authors: Hedrick John C. , Fritz Steven G. 
Published: December 2014

A number of technical challenges are faced when applying wall flow Diesel Particulate Filter (DPF) systems to large high horsepower off-highway applications, locomotives, and marine diesel engine applications due to the size of the DPF system required and the space constraints associated with these applications. Experimental results show that a new approach of adding an exhaust bypass valve, creating a partial-flow DPF system, can greatly reduce the DPF package size while continuing to offer significant PM emission reductions. The exhaust bypass valve is configured to open proportionally to maintain a pre-set maximum engine backpressure as the exhaust flow increases.
Proof-of-concept testing of an experimental partial flow DPF system was conducted on a 3MW, 4-stroke locomotive engine, following U.S. EPA locomotive certification test protocols. These tests showed that the experimental DPF system, which was approximately 40 percent smaller than what would be expected for this application, provided an 84 percent PM reduction over the US-EPA Switcher Cycle and 59 percent reduction over the Line-Haul Cycle. It was calculated that the system could provide a 91 percent PM reduction over the Switcher Cycle and 76 percent PM reduction over the Line-Haul Cycle with addition of a DOC in the bypass exhaust flow.
The Evolution of Diesel Engine Performance Prediction
Authors: Primus Roy J. 
Published: December 2014

Thermodynamic system performance modeling has become an integral part of the engine development process. The modeling tools used for this type of analysis have evolved from fairly simple calculations of limited scope into detailed simulations with ever-increasing complexity. These analytical tools are based on the combination of basic concepts, physical phenomena and experimental correlations. As with other categories of analysis, their evolution has also been closely coupled with the advances in computer technology.
This document provides a historic view of thermodynamic system simulation and revisits some of the developments in modeling techniques, engine measurements, data acquisition systems and computer hardware that have contributed to the understanding of engine performance prediction.
Combustion Characteristics of Lean Burn and Stoichiometric With EGR Spark Ignited Natural Gas Engines
Authors: Xu Hui , LaPointe Leon A. 
Published: December 2014

Natural gas has been widely used in reciprocating engines for various applications such as automobile, electricity generation, and gas compression. It is in the public interest to burn fuels more efficiently and at lower exhaust emissions. Natural gas is very suitable to serve this purpose due to its clean combustion, small carbon footprint, and, with recent breakthroughs in drilling technologies, increased availability and low cost. Natural gas can be used in lean burn spark ignited (LBSI) or stoichiometric EGR spark ignited (SESI) engines. Selection of either LBSI or SESI requires accommodation of requirements such as power output/density, engine efficiency, emissions, knock margin, and cost. The work described in this paper investigated the feasibility of operating an engine originally built as an LBSI under SESI conditions.
Analytical tools and workflow developed by Cummins, Inc. are used in this study. The tools require fundamental combustion properties as inputs, including laminar flame speed (LFS), adiabatic flame temperature (AFT) and autoignition interval (AI). These parameters provide critical information about combustion duration, engine out NOx, and relative knock propensity. An existing LBSI engine operating at its as released lambda was selected as baseline. The amount of EGR for the SESI configuration was selected so that it would have the same combustion duration as that of the LBSI at its reference lambda. One dimensional (1D) cycle simulations were conducted under both SESI and LBSI conditions assuming constant output power, compression ratio, volumetric efficiency, heat release centroid and brake mean effective pressure (BMEP). The 1D cycle simulations provide peak cylinder pressure (PCP) and peak unburned zone temperature (PUZT) under LBSI and SESI conditions. The results show that the SESI configuration has lower PCP but higher peak unburned zone temperature than that of the LBSI for the same output power. Also, for the same combustion duration, SESI has higher AFT than that of LBSI, resulting in higher engine out NOx emissions. The SESI configuration has shorter AI than that of LBSI engine, or smaller relative knock margin. Reduction of output power and emissions aftertreatment in the form of a three way catalyst (TWC) is required to operate under SESI engine conditions.
Use of Early Exhaust Valve Opening to Improve Combustion Efficiency and Catalyst Effectiveness in a Multi-Cylinder RCCI Engine System: A Simulation Study
Authors: Bharath Anand Nageswaran , Kalva Nitya , Reitz Rolf D. , Rutland Christopher J. 
Published: December 2014

Low Temperature Combustion (LTC) strategies such as Reactivity Controlled Compression Ignition (RCCI) can result in significant improvements of fuel economy and emissions reduction. However, they can produce significant carbon monoxide and unburnt hydrocarbon emissions at low load operating conditions due to poor combustion efficiencies at these operating points, which is a consequence of the low combustion temperatures that cause the oxidation rates of these species to slow down. The exhaust gas temperature is also not high enough at low loads for effective performance of turbocharger systems and diesel oxidation catalysts (DOC). The DOC is extremely sensitive to exhaust gas temperature changes and lights off only when a certain temperature is reached, depending on the catalyst specifications. Uncooled EGR can increase combustion temperatures, thereby improving combustion efficiency, but high EGR concentrations of 50% or more are required, thereby increasing pumping work and reducing volumetric efficiency. However, with early exhaust valve opening, the exhaust gas temperature can be much higher, allowing lower EGR flow rates, and enabling activation of the DOC for more effective oxidization of unburnt hydrocarbons and CO in the exhaust.
In this paper, a multi-cylinder engine system simulation of RCCI at low load operation with early exhaust valve opening is presented, along with consideration of the exhaust aftertreatment system. The combustion process is modeled using the 3D CFD code, KIVA, and the heat release rates obtained from this combustion are used in a GT-Power model of a turbocharged, multi-cylinder light-duty RCCI engine for a full system simulation. The post-turbine exhaust gas is fed into GT-Power’s aftertreatment model of the engine’s DOC to determine the catalyst response. It is confirmed that opening the exhaust valve earlier increases the exhaust gas temperature, and hence lower EGR flow rates are needed to improve combustion efficiency. It was also found that exhaust temperatures of around 457 K are required to light off the catalyst and oxidize the unburnt hydrocarbons and CO effectively. Performance of the DOC was drastically improved and higher amounts of unburnt hydrocarbons were oxidized by increasing the exhaust gas temperature.
Conrod Bearings With an Optimized Narrow Circumferential Oil Groove: Simulated Durability Improvement for Heavy-Duty Applications
Authors: Kalogiannis Konstantinos , Merritt David , Mian Omar , Gibson Hugh 
Published: December 2014

Under normal operating conditions, engine crankshaft bearings experience variations in oil film temperature due to shearing of the oil film. This can have a negative impact on the bearing operating life since the viscosity of the lubricant is temperature dependent.
In the current study, a thermo-elastohydrodynamic lubrication (TEHL) analysis has been conducted using an in-house specialized simulation package called SABRE-TEHL. This advanced simulation tool has been used to optimize a new bearing design feature leading to a significant temperature reduction, which in turns increases the robustness of the system.
Dynamic Identification of Thermodynamic Parameters for Turbocharger Compressor Models
Authors: Burke Richard , Olmeda Pablo , Serrano José Ramón 
Published: December 2014

A novel experimental procedure is presented which allows simultaneous identification of heat and work transfer parameters for turbocharger compressor models. The method introduces a thermally transient condition and uses temperature measurements to extract the adiabatic efficiency and internal convective heat transfer coefficient simultaneously, thus capturing the aerodynamic and thermal performance. The procedure has been implemented both in simulation and experimentally on a typical turbocharger gas stand facility.
Under ideal conditions, the new identification predicted adiabatic efficiency to within 1%point and heat transfer coefficient to within 1%. A sensitivity study subsequently showed that the method is particularly sensitive to the assumptions of heat transfer distribution pre and post compression. If 20% of the internal area of the compressor housing is exposed to the low pressure intake gas, and this is not correctly assumed in the identification process, errors of 7–15%points were observed for compressor efficiency. This distribution in heat transfer also affected the accuracy of heat transfer coefficient which increased to 20%. Thermocouple sensors affect the transient temperature measurements and in order to maintain efficiency errors below 1%, probes with diameter of less than 1.5mm should be used.
Experimentally, the method was shown to reduce the adiabatic efficiency error at 90krpm and 110krpm compared to industry standard approach from 6% to 3%. However at low speeds, where temperature differences during the identification are small, the method showed much larger errors.
Lean HCCI/Rich SACI Gasoline Combustion Cycling and Three-Way Catalyst for Fuel Efficiency and NOx Reduction
Authors: Chen Yi , Šíma Vojtěch , Lin Weiyang , Sterniak Jeff , Bohac Stanislav V. 
Published: December 2014

Multi-mode combustion (MMC) concepts using homogeneous charge compression ignition (HCCI) gasoline combustion at low loads and spark assisted compression ignition (SACI) gasoline combustion at medium loads have the potential for improved fuel efficiency relative to spark ignition (SI) gasoline combustion. Two MMC concepts are compared in this paper with respect to fuel efficiency and tailpipe NOx emissions. The first concept uses stoichiometric HCCI and SACI to allow standard three-way catalyst (TWC) operation. The second concept also uses HCCI and SACI, but cycles between lean and rich combustion and uses a TWC with increased oxygen storage capacity (OSC) for potentially even greater fuel efficiency improvement.
This paper performs a preliminary comparison of the two MMC concepts by analyzing two scenarios: 1) cycling between stoichiometric HCCI at 2 bar BMEP (brake mean effective pressure) and stoichiometric SACI at 3 bar BMEP, and 2) cycling between lean HCCI at 2 bar BMEP and rich SACI at 3 bar BMEP. The effects of excess oxygen ratio during HCCI operation and the frequency of oxygen depletion events on TWC performance and fuel efficiency are investigated.
Results show that MMC lean/rich cycling can achieve better fuel efficiency than stoichiometric HCCI/SACI cycling. NOx emissions are moderately higher, but may still be low enough to meet current and future emission regulations.
Ethanol Optimized Powertrain for Medium Duty Trucks
Authors: Perfetto Anthony , Kameshwaran Karthik , Geckler Samuel C. , Zope Rohit , Lana Carlos , Kothandaraman Govindarajan 
Published: December 2014

This paper includes a detailed description of an optimized E85 concept engine developed for medium duty applications (Class 4-6 trucks) targeting ultra-low carbon emissions while maintaining power and delivering competitive cost of ownership. The engine is a light weight, downsized and boosted in-line 4 cylinder with air handling, fuel, and combustion systems designed specifically for E85 capability, producing high brake mean effective pressure (BMEP) at high thermal efficiency. It is integrated with a 12V start/stop system including a smart alternator for improved energy management.
The present work demonstrates that even with the relative difference in the cost per heating value of fuel, using E85 can be upwards of 20% lower in cost while running middle to high loads. Combining high BMEP capability and a highly downsized engine displacement can ensure operation at high specific load where engine thermal efficiency is very good even in pickup-and-delivery type drive cycles.
The performance characteristics of this engine were mapped using stoichiometric combustion and a three way catalyst for emissions control. The ability to perform at or close to Maximum Brake Torque (MBT) spark timing throughout the torque curve has been facilitated by an optimized combustion system design along with direct injection. The high engine thermal efficiency and knock tolerance of this combustion system eliminates the need for fuel enrichment anywhere in the engine map.
Fuel Sensitive Ignition Delay Models for a Local and Global Description of Direct Injection Internal Combustion Engines
Authors: Kwak Kyoung Hyun , Borgnakke Claus , Jung Dohoy 
Published: December 2014

Models for ignition delay in a direct injection compression ignition engine are investigated and fuel specific properties are included to predict the effects of different fuels on the ignition delay. These models follow the Arrhenius type expression for the ignition delay modified with the oxygen concentration and Cetane number to extend the range of validity. In this investigation two fuel-sensitive spray ignition delay models are developed: a global model and a local model. The global model is based on the global combustion chamber charge properties including temperature, pressure and oxygen/fuel content. The local model is developed to account for temporal and spatial variations in properties of separated spray zones such as local temperature, oxidizer and fuel concentrations obtained by a quasi-dimensional multi-zone fuel spray model. These variations are integrated in time to predict the ignition delay. An ignition delay model is typically re-calibrated for a specific fuel being used. In this study, the global ignition delay model includes the Cetane number to capture ignition delay of various fuels. The local model uses Cetane number and local stoichiometric oxygen to fuel molar ratio. Due to those variables, the model is capable of predicting spray ignition delays for a set of fuels with a single calibration step. Experimental dataset of spray ignition delay in a constant volume chamber is used for model development and calibration. The models show a good accuracy for the predicted ignition delay of four different fuels: JP8, DF2, n-heptane and n-dodecane. The investigation revealed that the most accurate form of the models is from a calibration done for each individual fuel with only a slight decrease in accuracy when a single calibration is done for all fuels. The single calibration case is the more desirable outcome as it leads to general models that cover all the fuels. Of the two proposed models the local model has a slightly better accuracy compared to the global model. Results for both models demonstrate the improvements that can be obtained for the ignition delay model when additional fuel specific properties are included in the spray ignition model.
Other alternative fuels like synthetic oxygenated fuels were included in the investigation. These fuels behave differently such that the Cetane number does not provide the same explanation for the trend in ignition delay. Though of lower accuracy, the new models do improve the predictive capability when compared with existing types of ignition delay models applied to this kind of fuels.
The Observation of Cyclic Variation in Engine Simulations When Using RANS Turbulence Modeling
Authors: Richards Keith , Probst Daniel , Pomraning Eric , Senecal P. K. , Scarcelli Riccardo 
Published: December 2014

State-of-the art engine technologies are susceptible to high cycle-to-cycle variability. Researchers have successfully used Large Eddy Simulations (LES) to capture this cyclic variation with CFD. However, LES is computationally expensive. The current work demonstrates that using RANS turbulence models can also exhibit cyclic variation if the simulation approach minimizes numerical viscosity. This is accomplished by using fine mesh resolution, non-morphing mesh motion, higher-order accurate numerical schemes, and small timesteps.
RANS turbulence models act to destroy time-varying smaller eddies and replace the mixing effects of these eddies with enhanced viscosity. In an IC engine, larger-scale eddies can change from cycle to cycle, and may not be small enough to be dampened out by the RANS turbulence viscosity. By minimizing the numerical viscosity, the length scale at which eddies are destroyed is reduced and more structure is seen in the simulated flowfield. If the injection and combustion strategy in an engine is susceptible to cyclic changes in these large-scale eddies, then cyclic variation will be apparent in the simulation when using a RANS model.
This work will also demonstrate that perturbations in initial conditions, boundary conditions, or numerical settings can give run-to-run variability in simulation consistent with cycle-to-cycle variability in an actual engine.
For the current work, three studies are performed to show that the use of a RANS turbulence model does not always yield an ensemble average result. One of the studies is a basic cylinder-in-cross-flow case. The other two studies are for engines. One of the engine studies focuses on global mixing parameters and compares to TCC (Transparent Combustion Chamber) experimental data. The other engine study looks at cycle-to-cycle variation in combustion predictions.
Numerical and Experimental Analysis of Ignition and Combustion Stability in EGR Dilute GDI Operation
Authors: Scarcelli Riccardo , Matthias Nicholas S. , Wallner Thomas 
Published: December 2014

This paper discusses the characteristics of EGR dilute GDI engines in terms of combustion stability. A combined approach consisting of RANS numerical simulations integrated with experimental engine testing is used to analyze the effect of the ignition source on flame propagation under dilute operating conditions.
A programmable spark-based ignition system is compared to a production spark system in terms of cyclic variability and ultimately indicated efficiency. 3D-CFD simulations are carried out for multiple cycles with the goal of establishing correlations between the characteristics of the ignition system and flame propagation as well as cycle-to-cycle variations. Numerical results are compared to engine data in terms of in-cylinder pressure traces.
The results show that an improved control over the energy released to the fluid surrounding the spark domain during the ignition process has beneficial effects on combustion stability. This allows extending the dilution tolerance for fuel/air mixtures. Although affected by cyclic variability, numerical results show good qualitative agreement with experimental data. The result is a simple but promising approach for relatively quick assessment of stability improvements from advanced and alternative ignition strategies.
A Computational Study of the Mixture Preparation in a Direct Injection Hydrogen Engine
Authors: Le Moine Jerome , Senecal P. K. , Kaiser Sebastian A. , Salazar Victor M. , Anders Jon W. , Svensson K. I. , Gehrke C. R. 
Published: December 2014

This paper reports the validation of a three-dimensional numerical simulation of the mixture preparation in a direct-injection hydrogen-fueled engine. Computational results from the commercial code CONVERGE are compared to the experimental data obtained from an optically accessible engine. The geometry used in the simulation is a passenger-car sized, four-stroke, spark-ignited engine. The simulation includes the geometry of the combustion chamber as well as the intake and exhaust ports. The hydrogen is supplied at 100 bar from a centrally located injector with a single-hole nozzle.
The comparison between the simulation and experimental data is made on the central vertical plane. The fuel mole concentration and flow field are compared during the compression stroke at different crank angles. The comparison shows good agreement between the numerical and experimental results during the early stage of the compression stroke. The penetration of the jet and the interaction with the cylinder walls are correctly predicted. The fuel spreading is under predicted which results in differences in flow field and fuel mixture during the injection between experimental and numerical results. At the end of the injection, the fuel distribution shows some disagreement which gradually increases during the rest of the simulation.