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An experimental study was performed to develop a more fundamental understanding of the effects of secondary air injection (SAI) on exhaust gas emissions and catalyst light-off characteristics during cold start of a modern SI engine. The effects of engine operating parameters and various secondary air injection strategies such as spark retardation, fuel enrichment, secondary air injection location and air flow rate were investigated to understand the mixing, heat loss, and thermal and catalytic oxidation processes associated with SAI. Time-resolved HC, CO and CO₂ concentrations were tracked from the cylinder exit to the catalytic converter outlet and converted to time-resolved mass emissions by applying an instantaneous exhaust mass flow rate model. A phenomenological model of exhaust heat transfer combined with the gas composition analysis was also developed to define the thermal and chemical energy state of the exhaust gas with SAI.

Engine-out HC emissions from a PFI spark ignition engine were measured using a gas chromatograph and a flame ionization detector (FID). Two port fuel injectors were used respectively for ethanol and gasoline so that the delivered fuel was comprised of 0, 25, 50, 75 and 100% (by volume) of ethanol. Tests were run at 1.5, 3.8 and 7.5 bar NIMEP and two speeds (1500 and 2500 rpm). The main species identified with pure gasoline were partial reaction products (e.g. methane and ethyne) and aromatics, whereas with ethanol/gasoline mixtures, substantial amounts of ethanol and acetaldehyde were detected. Indeed, using pure ethanol, 74% of total HC moles were oxygenates. In addition, the molar ratio of ethanol to acetaldehyde was determined to be 5.5 to 1. The amount (as mole fraction of total HC moles) of exhaust aromatics decreased linearly with increasing ethanol in the fuel, while oxygenate species correspondingly increased.

Vehicle target setting is an evolving process based on continually changing internal (management, standards) and external (competitive and legal) requirements. In addition to evolving requirements, the process for establishing and documenting targets may not be clear. The objective of this paper is to detail the overall process of target setting, the critical factors to consider, and key definitions for each stage of the process. It will describe the complete process from early competitive benchmarking to final verification testing. Setting targets for a vehicle requires definition and thorough benchmarking of the competition, an understanding of the key attributes used to describe the vehicles' performance, and a clearly defined set of requirements. These requirements will be regulatory, corporate and competitively based and grouped by clearly defined, customer perceived attributes which can be cascaded to specific vehicle systems.

The high load limit of a boosted homogeneous-charge-compression-ignition (HCCI) engine operating on negative-valve-overlap (NVO) was assessed. When operating under stoichiometric condition with no external dilution, the load, as measured by the net indicated mean effective pressure (NIMEP), increased with increase in manifold absolute pressure (MAP), and with decrease in trapped amount of residual gas. The maximum pressure rise rate (MPRR), however, also increased correspondingly. When the MAP and the amount of residual gas were adjusted so that the engine operating point could be held at a constant MPRR value, the NIMEP increased with the simultaneous decrease in MAP and residual until the misfire limit was reached. Therefore if a MPRR ceiling is imposed, the high load limit of an HCCI engine is at the intersection of the constraining MPRR line and the misfire line.

A laboratory study was performed to assess the effects of sulfur poisoning and desulfation temperature on the NO conversion of a LNT+(Cu/SCR) in-situ system. Four LNT+(Cu/SCR) systems were aged for 4.5 hours without sulfur at 600, 700, 750, and 800°C using A/F ratio modulations to represent 23K miles of desulfations at different temperatures. NO conversion tests were performed on the LNT alone and on the LNT+SCR system using a 60 s lean/5 s rich cycle. The catalysts were then sulfur-poisoned at 400°C and desulfated four times and re-evaluated on the 60/5 tests. This test sequence was repeated 3 more times to represent 100K miles of desulfations. After simulating 23K miles of desulfations, the Cu-based SCR catalysts improved the NO conversion of the LNT at low temperatures (e.g., 300°C), although the benefit decreased as the desulfation temperature increased from 600°C to 800°C.

In this paper a diagnostic design process is proposed for developmental vehicles where mainstream design process is not well-suited. First a review of current practice in on-board vehicle fault diagnostics design is presented with particular focus on the application of this process to the development of the Ford Escape Hybrid Electric Vehicle (HEV) program and a demonstration Fuel Cell Electric Vehicle (FCEV) program. Based on the review and evaluation of these experiences, a new tool for diagnostics design is proposed that promises to make the design more traceable, to reduce the repetition of work, and to improve understandability and reuse.

A simulation-based, system reliability-based design optimization (RBDO) method is presented that can handle problems with multiple failure regions and correlated random variables. Copulas are used to represent the correlation. The method uses a Probabilistic Re-Analysis (PRRA) approach in conjunction with a trust-region optimization approach and local metamodels covering each trust region. PRRA calculates very efficiently the system reliability of a design by performing a single Monte Carlo (MC) simulation per trust region. Although PRRA is based on MC simulation, it calculates “smooth” sensitivity derivatives, allowing therefore, the use of a gradient-based optimizer. The PRRA method is based on importance sampling. It provides accurate results, if the support of the sampling PDF contains the support of the joint PDF of the input random variables. The sequential, trust-region optimization approach satisfies this requirement.

Having, by now, introduced several new vehicles that comply with FMVSS 202a, manufacturers are reporting an increased number of complaints from consumers who find that the head restraint is too close; negatively affecting their posture. It is speculated that one of the reasons that head restraints meeting the new requirement are problematic is that the FMVSS backset measurement is performed at a back angle that is more reclined than the back angle most drivers choose and the back angle at which the seat / vehicle was designed. The objective of this paper is to confirm this hypothesis and elaborate on implications for regulatory compliance in FMVSS 202a.

A detailed study is undertaken to examine how 2010+ diesel engine exhaust emissions change when a soybean-derived B20 biodiesel fuel is used instead of a conventional ultra-low sulfur diesel fuel and to investigate how these changes impact the aftertreatment system. Particulate matter (PM) emissions for each fuel are characterized in terms of mass emissions, size distributions, organic versus soot fraction, metals content, and particle morphology. PM mass recorded by Dekati Mass Monitor, thermal analysis of quartz filters, and calculated from particle size distributions consistently shows a 2 - 3 fold decrease in engine-out soot emissions over a wide mid-load range when changing from ULSD to B20 fuel. This is partly due to a decrease in particle number and partly to a decrease in average size. HC and NO emissions, in contrast, exhibit little change with fuel type.

New European emissions legislation (Euro5) specifies a limit for Particle Number (PN) emissions and therefore drives measurement of PN during vehicle development and homologation. Concurrently, the use of biofuel is increasing in the marketplace, and Euro5 specifies that reference fuel must contain a bio-derived portion. Work was carried out to test the effect of fuels containing different levels of Fatty Acid Methyl Ester (FAME) on particle number, size, mass and composition. Measurements were conducted with a Cambustion Differential Mobility Spectrometer (DMS) to time-resolve sub-micron particles (5-1000nm), and a Horiba Solid Particle Counting System (SPCS) providing PN data from a Euro5-compliant measurement system. To ensure the findings are relevant to the modern automotive business, testing was carried out on a Euro4 compliant passenger car fitted with a high-pressure common-rail diesel engine and using standard homologation procedures.

Ash, primarily derived from diesel engine lubricants, accumulates in diesel particulate filters directly affecting the filter's pressure drop sensitivity to soot accumulation, thus impacting regeneration frequency and fuel economy. After approximately 33,000 miles of equivalent on-road aging, ash comprises more than half of the material accumulated in a typical cordierite filter. Ash accumulation reduces the effective filtration area, resulting in higher local soot loads toward the front of the filter. At a typical ash cleaning interval of 150,000 miles, ash more than doubles the filter's pressure drop sensitivity to soot, in addition to raising the pressure drop level itself. In order to evaluate the effects of lubricant-derived ash on DPF pressure drop performance, a novel accelerated ash loading system was employed to generate the ash and load the DPFs under carefully-controlled exhaust conditions.

Effects of fuel cell material properties on water management were numerically investigated using Volume of Fluid (VOF) method in the FLUENT. The results show that the channel surface wettability is an important design variable for both serpentine and interdigitated flow channel configurations. In a serpentine air flow channel, hydrophilic surfaces could benefit the reactant transport to reaction sites by facilitating water transport along channel edges or on channel surfaces; however, the hydrophilic surfaces would also introduce significantly pressure drop as a penalty. For interdigitated air flow channel design, it is observable that liquid water exists only in the outlet channel; it is also observable that water distribution inside GDL is uneven due to the pressure distribution caused by interdigitated structure. An in-situ water measurement method, neutron imaging technique, was used to investigate the water behavior in a PEM fuel cell.

A uniaxial stress-strain curve obtained from a conventional tensile test is only valid up to the point of uniform elongation, beyond which a diffuse neck begins to develop, followed by localized necking and eventual fracture. However Finite Element Analysis for sheet metal forming requires an effective stress-strain curve that extends well beyond the diffuse necking point. Such an extension is usually accomplished by analytical curve fitting and extrapolation. Recent advancement in Digital Image Correlation (DIC) techniques allows direct measurement of full-range stress-strain curves by continuously analyzing the deformation within the diffuse neck zone until the material ruptures. However the stress-strain curve obtained this way is still approximate in nature. Its accuracy depends on the specimen size, the gage size for analysis, and the material response itself.

The conventional forming limit curve (FLC) has been widely and successfully used as a failure criterion to detect localized necking in stamping. However, in stamping advanced high strength steels (AHSS), under certain circumstances such as stretching-bending over a small die radius, the sheet metal fails much earlier than predicted by the FLC. This type of failure on the die radius is commonly called “shear fracture.” In this paper, the laboratory Stretch-Forming Simulator (SFS) and the Bending under Tension (BUT) tester are used to study shear fracture occurring during both early and later stages of stamping. Results demonstrate that the occurrence of shear fracture depends on the combination of the radius-to-thickness (R/T) ratio and the tension/stretch level applied to the sheet during stretching or drawing. Based on numerous experimental results, an empirical shear fracture limit curve or criterion is obtained.

Piston design is a challenging engineering problem which involves complex physics and requires satisfying multiple performance objectives. Uncertainty in piston operating conditions and variability in piston design variables are inevitable and must be accounted for. The piston assembly can be a major source of engine mechanical friction and cold start noise, if not designed properly. In this paper, an analytical piston model is used in a deterministic and probabilistic (reliability-based) multi-objective design optimization process to obtain an optimal piston design. The model predicts piston performance in terms of scuffing, friction and noise, In order to keep the computational cost low, efficient and accurate metamodels of the piston performance metrics are used. The Pareto set of all optimal solutions is calculated allowing the designer to choose the “best” solution according to trade-offs among the multiple objectives.

A detailed investigation of the influence of anisotropic hardening models on drawbead restraining force is presented in this paper. The recently modified Yoshida model is adopted to characterize the anisotropic hardening behavior for steels. A two-dimensional drawbead model is used and the restraining forces corresponding to several different bead penetrations are obtained and compared against experimental results. The comparison of the predicted results for the Modified Yoshida Model with isotropic hardening models indicates that the anisotropic hardening gives lower drawbead restraining forces in general. The impact of hardening models on springback is also presented, and it's demonstrated that the springback amount predicted by the modified Yoshida model is much closer to the experimental data than that predicted by conventional isotropic hardening model.

One of the issues in stamping of advanced high strength steels (AHSS) is the stretch bending fracture on a sharp radius (commonly referred to as shear fracture). Shear fracture typically occurs at a strain level below the conventional forming limit curve (FLC). Therefore it is difficult to predict in computer simulations using the FLC as the failure criterion. A modified Mohr-Coulomb (M-C) fracture criterion has been developed to predict shear fracture. The model parameters for several AHSS have been calibrated using various tests including the butter-fly shaped shear test. In this paper, validation simulations are conducted using the modified (M-C) fracture criterion for a dual phase (DP) 780 steel to predict fracture in the stretch forming simulator (SFS) test and the bending under tension (BUT) test. Various deformation fracture modes are analyzed, and the range of usability of the criterion is identified.

Incremental Sheet Forming (ISF) is an emerging sheet metal prototyping technology where a part is formed as one or more stylus tools are moving in a pre-determined path and deforming the sheet metal locally while the sheet blank is clamped along its periphery. A deformation analysis of incremental forming process is presented in this paper. The analysis includes the development of an analytical model for strain distributions based on part geometry and tool paths; and numerical simulations of the forming process with LS-DYNA. A skew cone is constructed and used as an example for the study. Analytical and numerical results are compared, and excellent correlations are found. It is demonstrated that the analytical model developed in this paper is reliable and efficient in the prediction of strain distributions for incremental forming process.

Mechanisms of NH₃ generation using LNT-like catalysts have been studied in a bench reactor over a wide range of temperatures, flow rates, reformer catalyst types and synthetic exhaust-gas compositions. The experiments showed that the on board production of sufficient quantities of ammonia on board for SCR operation appeared feasible, and the results identified the range of conditions for the efficient generation of ammonia. In addition, the effects of reformer catalysts using the water-gas-shift reaction as an in-situ source of the required hydrogen for the reactions are also illustrated. Computations of the NH₃ and NOx kinetics have also been carried out and are presented. Design and impregnation of the SCR catalyst in proximity to the ammonia source is the next logical step. A heated synthetic-exhaust gas flow bench was used for the experiments under carefully controlled simulated exhaust compositions.

Ash accumulation in diesel particulate filters, mostly from essential lubricant additives, decreases the filter's soot storage capacity, adversely affects fuel economy, and negatively impacts the filter's service life. While the adverse effects of ash accumulation on DPF performance are well known, the underlying mechanisms controlling these effects are not. To address these issues, results of detailed measurements with specially formulated lubricants, correlating ash properties to individual lubricant additives and their effects on DPF pressure drop, are presented. Investigations using the specially-formulated lubricants showed ash consisting primarily of calcium sulfates to exhibit significantly increased flow resistance as opposed to ash primarily composed of zinc phosphates. Furthermore, ash accumulated along the filer walls was found to be packed approximately 25% denser than ash accumulated in the channel end-plugs.