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2011-04-12
Technical Paper
2011-01-1421
Yashodeep Lonari, Christopher Polonowski, Jeffrey Naber, Bo Chen
This paper presents the development of a Stochastic Knock Detection (SKD) method for combustion knock detection in a spark-ignition engine using a model based design approach. The SKD set consists of a Knock Signal Simulator (KSS) as the plant model for the engine and a Knock Detection Module (KDM). The KSS as the plant model for the engine generates cycle-to-cycle accelerometer knock intensities following a stochastic approach with intensities that are generated using a Monte Carlo method from a lognormal distribution whose parameters have been predetermined from engine tests and dependent upon spark-timing, engine speed and load. The lognormal distribution has been shown to be a good approximation to the distribution of measured knock intensities over a range of engine conditions and spark-timings for multiple engines in previous studies.
2011-04-12
Journal Article
2011-01-0238
Vicente Romero
This paper1 explores some of the important considerations in devising a practical and consistent framework and methodology for working with experiments and experimental data in connection with modeling and prediction. The paper outlines a pragmatic and versatile “real-space” approach within which experimental and modeling uncertainties (correlated and uncorrelated, systematic and random, aleatory and epistemic) are treated to mitigate risk in modeling and prediction. The elements of data conditioning, model conditioning, model validation, hierarchical modeling, and extrapolative prediction under uncertainty are examined. An appreciation can be gained for the constraints and difficulties at play in devising a viable end-to-end methodology. The considerations and options are many, and a large variety of viewpoints and precedents exist in the literature, as surveyed here. Rationale is given for the various choices taken in assembling the novel real-space end-to-end framework.
2011-04-12
Technical Paper
2011-01-0829
Bao-Lin Wang, Paul C. Miles, Rolf D. Reitz, Zhiyu Han, Benjamin Petersen
RNG k-ε closure turbulence dissipation equations are evaluated employing the CFD code KIVA-3V Release 2. The numerical evaluations start by considering simple jet flows, including incompressible air jets and compressible helium jets. The results show that the RNG closure turbulence model predicts lower jet tip penetration than the "standard" k-ε model, as well as being lower than experimental data. The reason is found to be that the turbulence kinetic energy is dissipated too slowly in the downstream region near the jet nozzle exit. In this case, the over-predicted R term in RNG model becomes a sink of dissipation in the ε-equation. As a second step, the RNG turbulence closure dissipation models are further tested in complex engine flows to compare against the measured evolution of turbulence kinetic energy, and an estimate of its dissipation rate, during both the compression and expansion processes.
2005-10-24
Technical Paper
2005-01-3748
Shane De Zilwa, Richard Steeper
Optical engines are often skip-fired to maintain optical components at acceptable temperatures and to reduce window fouling. Although many different skip-fired sequences are possible, if exhaust emissions data are required, the skip-firing sequence ought to consist of a single fired cycle followed by a series of motored cycles (referred to here as singleton skip-firing). This paper compares a singleton skip-firing sequence with continuous firing at the same inlet conditions, and shows that combustion performance trends with equivalence ratio are similar. However, as expected, reactant temperatures are lower with skip-firing, resulting in retarded combustion phasing, and lower pressures and combustion efficiency. LIF practitioners often employ a homogeneous charge of known composition to create calibration images for converting raw signal to equivalence ratio.
2005-10-24
Technical Paper
2005-01-3705
Charles J. Mueller
The accurate quantification and control of mixture stoichiometry is critical in many applications using new combustion strategies and fuels (e.g., homogeneous charge compression ignition, gasoline direct injection, and oxygenated fuels). The parameter typically used to quantify mixture stoichiometry (i.e., the proximity of a reactant mixture to its stoichiometric condition) is the equivalence ratio, ϕ. The traditional definition of ϕ is based on the relative amounts of fuel and oxidizer molecules in a mixture. This definition provides an accurate measure of mixture stoichiometry when the fuel molecule does not contain oxidizer elements and when the oxidizer molecule does not contain fuel elements. However, the traditional definition of ϕ leads to problems when the fuel molecule contains an oxidizer element, as is the case when an oxygenated fuel is used, or once reactions have started and the fuel has begun to oxidize.
2006-04-03
Technical Paper
2006-01-0457
Angel Urbina, T. Paez, T. Hinnerichs, C. O'Gorman, P. Hunter, B. Rutherford
As technical and non-technical constraints make testing of complex physical systems more restrictive, an increased reliance on modeling and simulation of large systems has arisen. Time and/or frequency domain analyzes of finite element models are performed on massively parallel computers. Due to the high consequence of these analyses, there is a need to quantitatively assess the predictive accuracy of finite element models used to simulate these complex physical systems relative to any available experimental results. In this paper we outline our understanding of model validation and the process followed to make a determination of the validity of a model. An example will be used to demonstrate the process.
2005-04-11
Technical Paper
2005-01-1775
David G. Robinson, Christopher B. Atcitty
In the process of conducting a reliability analysis of a system, quite often the population of interest is not homogenous; consisting of sub-populations which arise as production operations are adjusted, component suppliers are changed, etc. While these sub-populations are each unique in many ways, they also have much in common. It is also common for data to be available from a variety of different test regimes, e.g. environmental testing and fleet maintenance observations. Hierarchical Bayesian methods provide an organized, objective means of estimating the reliability of the individual systems, the sub-population reliability as well as the reliability of the entire population. This paper provides an introduction to a Bayesian approach that can be extended for more complicated situations.
2015-04-14
Journal Article
2015-01-0818
Brian Peterson, Isaac Ekoto, William Northrop
Abstract Negative valve overlap (NVO) is a viable control strategy that enables low-temperature gasoline combustion (LTGC) at low loads. Thermal effects of NVO fueling on main combustion are well understood, but fuel reforming chemistry during NVO has not been extensively studied. The objective of this work is to analyze the impact of global equivalence ratio and available oxidizer on NVO product concentrations. Experiments were performed in a LTGC single-cylinder engine under a sweep of NVO oxygen concentration and NVO fueling rates. Gas sampling at the start and end of the NVO period was performed via a custom dump-valve apparatus with detailed sample speciation by gas chromatography. Single-zone reactor models using detailed chemistry at relevant mixing and thermodynamic conditions were used in parallel to the experiments to evaluate expected yields of partially oxidized species under representative engine time scales.
2010-04-12
Technical Paper
2010-01-0361
Siddhartha Banerjee, Ting Liang, Christopher Rutland, Bing Hu
Diesel engine combustion is simulated using Large Eddy Simulation (LES) with a multi-mode combustion (MMC) model. The MMC model is based on the combination of chemical kinetics, chemical equilibrium, and quasi-steady flamelet calculations in different local combustion regimes. The local combustion regime is identified by two combustion indices based on the local temperature and the extent of mixture homogeneity. The LES turbulence model uses the dynamic structure model (DSM) for sub-grid stresses. A new spray model in the LES context is used, and the Reynolds-averaged Navier-Stokes (RANS) based wall model is retained with the LES derived scales. These models are incorporated in the KIVA3V-ERC-Release 2 code for engine combustion simulations. A wide range of diesel engine operating conditions were chosen to validate the combustion model.
2009-11-02
Journal Article
2009-01-2699
Caroline L. Genzale, Rolf D. Reitz, Mark P. B. Musculus
The effects of spray targeting on mixing, combustion, and pollutant formation under a low-load, late-injection, low-temperature combustion (LTC) diesel operating condition are investigated by optical engine measurements and multi-dimensional modeling. Three common spray-targeting strategies are examined: conventional piston-bowl-wall targeting (152° included angle); narrow-angle floor targeting (124° included angle); and wide-angle piston-bowl-lip targeting (160° included angle). Planar laser-induced fluorescence diagnostics in a heavy-duty direct-injection optical diesel engine provide two-dimensional images of fuel-vapor, low-temperature ignition (H2CO), high-temperature ignition (OH) and soot-formation species (PAH) to characterize the LTC combustion process.
2010-04-12
Technical Paper
2010-01-0625
Yuxin Zhang, Jaal Ghandhi, Benjamin Petersen, Christopher Rutland
A novel algebraic similarity model for subgrid scalar dissipation rate has been developed as part of the Large Eddy Simulation (LES) package KIVA3V-LES for diesel engine study. The model is proposed from an a priori study using Direct Numerical Simulation (DNS) of forced isotropic turbulence. In the a posteriori test, fully resolved turbulent passive scalar field measurements are used to validate the model in actual engine flows. For reason of the length limit by SAE and the specific interest in engine applications, only a prior test and a posteriori test in engine flows are included in this paper. A posteriori tests in isotropic cube flow, turbulent round jet and flame cases will be presented in separate papers. An engine LES simulation of multi consecutive cycles was performed in this study.
2009-09-13
Journal Article
2009-24-0083
Riccardo Scarcelli, Thomas Wallner, Victor M. Salazar, Sebastian A. Kaiser
Direct injection offers a large number of degrees of freedom, as it strongly influences the mixture stratification process. Experiments on a single cylinder research engine fuelled by H2, carried out at Argonne National Laboratory, showed the influence of injection parameters (timing and geometry) on engine efficiency and combustion stability. At low load, when a late injection strategy was performed, an unstable engine behavior was detected varying the injection direction. In order to optimize the mixture stratification process in DI H2 engines, it is important to understand the physics underlying the experimental results. A spatially resolved representation of the in-cylinder processes is a useful tool to properly set the injection parameters. Also, the knowledge of the pre-injection flow field is of added value in optimizing the injection process.
2014-04-01
Journal Article
2014-01-1423
Shaoping Quan, Meizhong Dai, Eric Pomraning, P. K. Senecal, Keith Richards, Sibendu Som, Scott Skeen, Julien Manin, Lyle M. Pickett
Shock waves have been recently observed in high-pressure diesel sprays. In this paper, three-dimensional numerical simulations of supersonic diesel spray injection have been performed to investigate the underlying dynamics of the induced shock waves and their interactions with the spray. A Volume-of-Fluid based method in the CFD software (CONVERGE) is used to model this multiphase phenomena. An adaptive Mesh Refinement (AMR) scheme is employed to capture the front of the spray and the shock waves with high fidelity. Simulation results are compared to the available experimental observations to validate the numerical procedure. Parametric studies with different injection and ambient conditions are conducted to examine the effect of these factors on the generation of shock waves and their dynamics.
2013-09-08
Technical Paper
2013-24-0001
Lyle M. Pickett, Julien Manin, Raul Payri, Michele Bardi, Jaime Gimeno
Transients in the rate of injection (ROI) with respect to time are ever-present in direct-injection engines, even with common-rail fueling. The shape of the injection ramp-up and ramp-down affects spray penetration and mixing, particularly with multiple-injection schedules currently in practice. Ultimately, the accuracy of CFD model predictions used to optimize the combustion process depends upon the accuracy of the ROI utilized as fuel input boundary conditions. But experimental difficulties in the measurement of ROI, as well as real-world affects that change the ROI from the bench to the engine, add uncertainty that may be mistaken for weaknesses in spray modeling instead of errors in boundary conditions. In this work we use detailed, time-resolved measurements of penetration at the Spray A conditions of the Engine Combustion Network to rigorously guide the necessary ROI shape required to match penetration in jet models that allow variable rate of injection.
2013-04-08
Technical Paper
2013-01-1105
Federico Perini, Adam Dempsey, Rolf D. Reitz, Dipankar Sahoo, Benjamin Petersen, Paul C. Miles
In a recent study, quantitative measurements were presented of in-cylinder spatial distributions of mixture equivalence ratio in a single-cylinder light-duty optical diesel engine, operated with a non-reactive mixture at conditions similar to an early injection low-temperature combustion mode. In the experiments a planar laser-induced fluorescence (PLIF) methodology was used to obtain local mixture equivalence ratio values based on a diesel fuel surrogate (75% n-heptane, 25% iso-octane), with a small fraction of toluene as fluorescing tracer (0.5% by mass). Significant changes in the mixture's structure and composition at the walls were observed due to increased charge motion at high swirl and injection pressure levels. This suggested a non-negligible impact on wall heat transfer and, ultimately, on efficiency and engine-out emissions.
2013-04-08
Journal Article
2013-01-0946
Vicente Romero, Joshua Mullins, Laura Swiler, Angel Urbina
This paper discusses the treatment of uncertainties corresponding to relatively few samples of random-variable quantities. The importance of this topic extends beyond experimental data uncertainty to situations involving uncertainty in model calibration, validation, and prediction. With very sparse samples it is not practical to have a goal of accurately estimating the underlying variability distribution (probability density function, PDF). Rather, a pragmatic goal is that the uncertainty representation should be conservative so as to bound a desired percentage of the actual PDF, say 95% included probability, with reasonable reliability. A second, opposing objective is that the representation not be overly conservative; that it minimally over-estimate the random-variable range corresponding to the desired percentage of the actual PDF. The presence of the two opposing objectives makes the sparse-data uncertainty representation problem an interesting and difficult one.
2012-04-16
Technical Paper
2012-01-1109
Marco Mehl, William Pitz, Mani Sarathy, Yi Yang, John E. Dec
The combustion behavior of conventional gasoline has been numerically investigated by means of detailed chemical-kinetic modeling simulations, with particular emphasis on analyzing the chemistry of the intermediate temperature heat release (ITHR). Previous experimental work on highly boosted (up to 325 kPa absolute) HCCI combustion of gasoline (SAE 2020-01-1086) showed a steady increase in the charge temperature up to the point of hot ignition, even for conditions where the ignition point was retarded well after top dead center (TDC). Thus, sufficient energy was being released by early pre-ignition reactions resulting in temperature rise during the early part of the expansion stroke This behavior is associated with a slow pre-ignition heat release (ITHR), which is critical to keep the engine from misfiring at the very late combustion phasings required to prevent knock at high-load boosted conditions.
2012-04-16
Journal Article
2012-01-1258
Joseph Oefelein, Rainer Dahms, Guilhem Lacaze
This paper provides an analysis of high-pressure phenomena and its potential effects on the fundamental physics of fuel injection in Diesel engines. In particular, we focus on conditions when cylinder pressures exceed the thermodynamic critical pressure of the injected fuel and describe the major differences that occur in the jet dynamics compared to that described by classical spray theory. To facilitate the analysis, we present a detailed model framework based on the Large Eddy Simulation (LES) technique that is designed to account for key high-pressure phenomena. This framework is then used to perform a thermodynamic analysis of the flow. We focus on the experiments being conducted in the high-pressure combustion vessel at Sandia National Laboratories using n-heptane as a reference fuel. The calculations are performed by rigorously treating the experimental geometry and operating conditions, with detailed treatment of relevant thermophysical mixture properties.
2012-04-16
Technical Paper
2012-01-0140
Bao-Lin Wang, Michael J. Bergin, Benjamin R. Petersen, Paul C. Miles, Rolf D. Reitz, Zhiyu Han
A generalized re-normalization group (RNG) turbulence model based on the local "dimensionality" of the flow field is proposed. In this modeling approach the model coefficients C₁, C₂, and C₃ are all constructed as functions of flow strain rate. In order to further validate the proposed turbulence model, the generalized RNG closure model was applied to model the backward facing step flow (a classic test case for turbulence models). The results indicated that the modeling of C₂ in the generalized RNG closure model is reasonable, and furthermore, the predictions of the generalized RNG model were in better agreement with experimental data than the standard RNG turbulence model. As a second step, the performance of the generalized RNG closure was investigated for a complex engine flow.
1998-05-04
Technical Paper
981428
Paul C. Miles, P. C. Hinze
Spontaneous Raman scattering with broadband signal collection is used to simultaneously measure the mole fractions of CO2, H2O, N2, O2, and fuel (C3H8) in a spark-ignition engine operating at low load. Both cycle-averaged and single-shot, cycle-resolved measurements of the mixing between residual and fresh charge are made from the beginning of the intake stroke to TDC compression. The measurements are made at twelve locations simultaneously with sub-millimeter spatial precision, which is sufficient to resolve the characteristic scales of inhomogeneity in most cases. Analysis of the spatial covariance functions provides a measure of the noise contribution to the measured mole fractions and, in certain instances, allows the determination of whether the measured composition fluctuations are associated with spatial inhomogeneities or with cyclic variations in overall charge composition.
2006-04-03
Technical Paper
2006-01-1160
Kevin L. Conrad, John R. Galloway, William P. Irwin, Walter H. Delashmit, James T. Jack, Govindaraj Kuntimad, Maritza R. Muguira, Charles Q. Little, Ralph R. Peters
Autonomous Navigation for military unmanned ground vehicles requires the ability to act without human intervention in increasingly difficult environments such as off-road terrain and military operations in urban terrain (MOUT). One method to accomplish this is through the combination of a local perception sensor suite with an a priori route planner and a local guidance algorithm that provides an automated obstacle detection, classification, and avoidance capability. This paper will detail the feasibility of this approach based on preliminary test results.
2005-11-01
Technical Paper
2005-01-3511
Rose McCallen, Kambiz Salari, Jason Ortega, Paul Castellucci, John Paschkewitz, Craig Eastwood, Larry Dechant, Basil Hassan, W. David Pointer, Fred Browand, Charles Radovich, Tai Merzel, Dennis Plocher, Anthony Leonard, Mike Rubel, James Ross, J. T. Heineck, Stephen Walker, Bruce Storms, Christopher Roy, David Whitfield, Ramesh Pankajakshan, Lafayette Taylor, Kidambi Sreenivas, Robert Englar
At 70 miles per hour, overcoming aerodynamic drag represents about 65% of the total energy expenditure for a typical heavy truck vehicle. The goal of this US Department of Energy supported consortium is to establish a clear understanding of the drag producing flow phenomena. This is being accomplished through joint experiments and computations, leading to the intelligent design of drag reducing devices. This paper will describe our objective and approach, provide an overview of our efforts and accomplishments related to drag reduction devices, and offer a brief discussion of our future direction.
2005-10-24
Technical Paper
2005-01-3791
Peter O. Witze, Michael Gershenzon, Hope A. Michelsen
Double-pulse laser-induced desorption with elastic laser scattering (LIDELS) is a diagnostic technique capable of making time-resolved, in situ measurements of the volatile fraction of diesel particulate matter (PM). The technique uses two laser pulses of comparable energy, separated in time by an interval sufficiently short to freeze the flow field, to measure the change in PM volume caused by laser-induced desorption of the volatile fraction. The first laser pulse of a pulse-pair produces elastic laser scattering (ELS) that gives the total PM volume, and also deposits the energy to desorb the volatiles. ELS from the second pulse gives the volume of the remaining solid portion of the PM, and the ratio of these two measurements is the quantitative solid volume fraction. In an earlier study, we used a single laser to make real-time LIDELS measurements during steady-state operation of a diesel engine.
2006-10-16
Technical Paper
2006-01-3436
R. Yu, X.S. Bai, L. Hildingsson, A. Hultqvist, Paul C. Miles
This paper presents a study of the turbulence field in an optical diesel engine operated under motored conditions using both large eddy simulation (LES) and Particle Image Velocimetry (PIV). The study was performed in a laboratory optical diesel engine based on a recent production engine from VOLVO Car. PIV is used to study the flow field in the cylinder, particularly inside the piston bowl that is also optical accessible. LES is used to investigate in detail the structure of the turbulence, the vortex cores, and the temperature field in the entire engine, all within a single engine cycle. The LES results are compared with the PIV measurements in a 40 × 28 mm domain ranging from the nozzle tip to the cylinder wall. The LES grid consists of 1283 cells. The grid dynamically adjusts itself as the piston moves in the cylinder so that the engine cylinder, including the piston bowl, is described by the grid.
2007-04-16
Technical Paper
2007-01-0647
Cherian A. Idicheria, Lyle M. Pickett
This paper details the development and application of a Rayleigh imaging technique for quantitative mixing measurements in a vaporizing diesel spray under engine conditions. Experiments were performed in an optically accessible constant-volume combustion vessel that simulated the ambient conditions in a diesel engine. Two-dimensional imaging of Rayleigh scattering from a diesel spray of n-heptane and well-characterized ambient was accomplished by using a 532 nm Nd:YAG laser sheet and a low-noise back-illuminated CCD camera. Methods to minimize interference from unwanted elastic scattering sources (e.g. windows, particles) were investigated and are discussed in detail. The simultaneous measurement of Rayleigh scattering signal from the ambient and from the diesel spray provides important benefits towards making the technique quantitative and accurate.
2007-04-16
Technical Paper
2007-01-0433
C. San Marchi, B. P. Somerday
Unlike other gases, hydrogen can promote embrittlement of structural metals at ambient temperature. The effects of high-pressure hydrogen gas on structural metals vary significantly depending on material, environmental, and mechanical variables as well as the metric used to evaluate performance. In this short review, we provide basic guidance on selection of materials for hydrogen gas service emphasizing the need for performing tests in relevant environments and using appropriate methods. Fracture mechanics and fitness-for-service type design approaches are highly recommended for ensuring robust yet efficient high-pressure designs for hydrogen gas service.
2007-04-16
Technical Paper
2007-01-0432
William G. Houf, Robert W. Schefer
Knowledge of the concentration field and flammability envelope from a small-scale hydrogen leak is an issue of importance for the safe use of hydrogen. A combined experimental and modeling program is being carried out by Sandia National Laboratories to characterize and predict the behavior of small-scale hydrogen releases. In contrast to the previous work performed by Sandia on large, momentum-dominated hydrogen leaks, these studies are focusing on small leaks in the Froude number range where both buoyant and inertial forces are important or, in the limit, where buoyancy dominates leak behavior. In the slow leak regime buoyant forces affect the trajectory and rate of air entrainment of the hydrogen jet leak and significant curvature can occur in the jet trajectory. Slow leaks may occur from leaky fittings or o-ring seals on hydrogen vehicles or other hydrogen-based systems where large amounts of pressure drop occur across the leak path.
2005-10-24
Technical Paper
2005-01-3837
Sanghoon Kook, Choongsik Bae, Paul C. Miles, Dae Choi, Lyle M. Pickett
The effects of charge dilution on low-temperature diesel combustion and emissions were investigated in a small-bore single-cylinder diesel engine over a wide range of injection timing. The fresh air was diluted with additional N2 and CO2, simulating 0 to 65% exhaust gas recirculation in an engine. Diluting the intake charge lowers the flame temperature T due to the reactant being replaced by inert gases with increased heat capacity. In addition, charge dilution is anticipated to influence the local charge equivalence ratio ϕ prior to ignition due to the lower O2 concentration and longer ignition delay periods. By influencing both ϕ and T, charge dilution impacts the path representing the progress of the combustion process in the ϕ-T plane, and offers the potential of avoiding both soot and NOx formation.
2004-03-08
Technical Paper
2004-01-1399
Lyle M. Pickett, Dennis L. Siebers
Methods of producing non-sooting, low flame temperature diesel combustion were investigated in an optically-accessible, quiescent constant-volume combustion vessel. Combustion and soot formation processes of single, isolated fuel jets were studied after autoignition and transient premixed combustion and while the injector needle was fully open (i.e., during the quasi-steady mixing-controlled phase of heat-release for diesel combustion).The investigation showed that fuel jets that do not undergo soot formation in any region of the reacting jet and that also have a low flame temperature could be produced in at least three different ways during mixing-controlled combustion: First, using a #2 diesel fuel and an injector tip with a 50 micron orifice, a fuel jet was non-sooting in ambient oxygen concentrations as low as 10% (simulating the use of EGR) for typical diesel ambient temperatures (1000 K) and densities.
2004-03-08
Technical Paper
2004-01-1678
Paul C. Miles, Dae Choi, Marcus Megerle, Bret RempelEwert, Rolf D. Reitz, Ming-Chia Lai, Volker Sick
Simultaneous two-component measurements of gas velocity and multi-dimensional numerical simulation are employed to characterize the evolution of the in-cylinder turbulent flow structure in a re-entrant bowl-in-piston engine under motored operation. The evolution of the mean flow field, turbulence energy, turbulent length scales, and the various terms contributing to the production of the turbulence energy are correlated and compared, with the objectives of clarifying the physical mechanisms and flow structures that dominate the turbulence production and of identifying the source of discrepancies between the measured and simulated turbulence fields. Additionally, the applicability of the linear turbulent stress modeling hypothesis employed in the k-ε model is assessed using the experimental mean flow gradients, turbulence energy, and length scales.
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