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Proposed LEV-III emission level will require improvements in NMOG, CO and NOx emissions as measured over FTP and US06 emission cycles. Incremental improvements in washcoat technologies, cold start calibration and catalyst system design are required to develop a cost effective solution set. New catalyst technologies demonstrated both lower HC and NOx emissions with 25% less platinum group metals (PGM). FTP and US06 emissions were measured on a 4-cylinder 2.4L application which compares a close-coupled converter and close-coupled + underfloor converter systems. A PGM placement study was performed with the close-coupled converter system employing these new catalyst technologies. Emissions results suggest that the placement of PGM is critical in minimizing emissions and PGM costs.

Fuels in the gasoline auto-ignition range (Research Octane Number (RON) > 60) have been demonstrated to be effective alternatives to diesel fuel in compression ignition engines. Such fuels allow more time for mixing with oxygen before combustion starts, owing to longer ignition delay. Moreover, by controlling fuel injection timing, it can be ensured that the in-cylinder mixture is “premixed enough” before combustion occurs to prevent soot formation while remaining “sufficiently inhomogeneous” in order to avoid excessive heat release rates. Gasoline compression ignition (GCI) has the potential to offer diesel-like efficiency at a lower cost and can be achieved with fuels such as low-octane straight run gasoline which require significantly less processing in the refinery compared to today’s fuels.

The 3-Zones Extended Coherent Flame Model (ECFM3Z) and the Tabulated Kinetics for Ignition (TKI) auto-ignition model are widely used for RANS simulations of reactive flows in Diesel engines. ECFM3Z accounts for the turbulent mixing between one zone that contains compressed air and EGR and another zone that contains evaporated fuel. These zones mix to form a reactive zone where combustion occurs. In this mixing zone TKI is applied to predict the auto-ignition event, including the ignition delay time and the heat release rate. Because it is tabulated, TKI can model complex fuels over a wide range of engine thermodynamic conditions. However, the ECFM3Z/TKI combustion modeling approach requires an efficient predictive spray injection calculation. In a Diesel direct injection engine, the turbulent mixing and spray atomization are mainly driven by the liquid/gas coupling phenomenon that occurs at moving liquid/gas interfaces.

Meeting regulated tailpipe emission standards requires a full system approach by automotive engineers encompassing: engine design, combustion system metrics, exhaust heat management, aftertreatment design and exhaust system packaging. Engine and combustion system design targets define desired engine out exhaust constituents, exhaust gas temperatures and oil consumption rates. Protecting required catalytic converter volume in the engine bay for stricter tailpipe emission standards is becoming more difficult. Future fuel economy mandates are leading to vehicle downsizing which is affecting all aspects of vehicle component packaging. In this study, we set out to determine the potential palladium (Pd) cost penalty as a result of increased light-off time required as a catalyst is positioned further away from the engine. Two aged converter systems with different Pd loadings were considered, and EPA FTP-75 emission tested at six different catalyst positions.

Detailed chemical kinetics, although preferred due to increased accuracy, can significantly slow down CFD combustion simulations. Chemistry solutions are typically the most computationally costly step in engine simulations. The calculation time can be significantly accelerated using a multi-zone combustion model. The multi-zone model is integrated into the CONVERGE CFD code. At each time-step, the CFD cells are grouped into zones based on the cell temperature and equivalence ratio. The chemistry solver is invoked only on each zone. The zonal temperature and mass fractions are remapped onto the CFD cells, such that the temperature and composition non-uniformities are preserved. Two remapping techniques published in the literature are compared for their relative performance. The accuracy and speed-up of the multi-zone model is improved by using variable bin sizes at different temperature and equivalence ratios.

EGR systems are widely applied in modern turbocharged diesel engines to reduce engine-out emissions and will, or are being used to mitigate engine knock in SI engines for improved SI engine efficiency and power. In this paper, different EGR systems are detailed and evaluated theoretically based on the thermodynamics of a turbocharged system featuring an EGR sub-system. Turbine expansion ratio is utilized as a metric to estimate engine efficiency, i.e., pumping losses during the gas exchange process. Approaches such as compressor and turbine bypassing are evaluated as well. Based on above analysis, a new approach is put forward to expand the turbocharger work zone, particularly in the high efficiency regions by correctly utilizing EGR systems at all engine speed range: low-pressure loop EGR system at lower engine speed range and high-pressure loop EGR system at high engine speed range.

CAE tools are increasingly important in the automotive design process. In part, CAE tools can be useful in reducing the number of physical prototypes required during a product development effort. CFD tools can assess and predict cylinder charge motion for proposed designs, thereby limiting the need for prototype work. Though detailed combustion simulation results could help guide product development, the time required for such simulations limits their usefulness in the context of a production program. However equally valuable information can be obtained from gas exchange analyses which require less computation time and are run only from Intake Valve opening (IVO) to spark timing. Chemical kinetics is not included in this type of analysis. Using this approach, large numbers of configurations can be evaluated in a short period of time. Every passing year automotive engineers are challenged to attain higher fuel economy targets.

In order to assist in fast design cycle of Diesel engines selective catalytic reduction (SCR) exhaust systems, significant endeavor is currently being made to improve numerical simulation accuracy of urea thermo-hydrolysis. In this article, the achievements of a recently developed urea semi-detailed decomposition chemical scheme are assessed using three available databases from the literature. First, evaporation and thermo-hydrolysis of urea-water solution (UWS) single-droplets hanged on a thin thermocouple ring (127 μm) as well as on a thick quartz (275 μm), have been simulated at ambient temperature conditions ranging from 473K to 773K. It has been shown that the numerical results, in terms of evaporation rate and urea gasification, as well as droplet temperature history are very close to the experiments if the heat flux coming from the droplet support is properly accounted for.

To meet TierII/LEVII emissions standards, light duty diesel (LDD) vehicles require high conversion efficiencies from the Aftertreatment Systems (ATS) for the removal of both Hydrocarbon (HC) and Nitrogen Oxide (NOx) species. The most populous configuration for LDD ATS have the Selective Catalytic Reduction (SCR) catalyst positioned on the vehicle behind the close coupled Diesel Oxidation Catalyst (DOC) and Catalyzed Diesel Particulate Filter (CDPF). This SCR position may require active heating measures which rely on the DOC/CDPF to provide heat through the combustion of HC and CO in the exhaust. Although DOCs are always impacted by their aging conditions, some aging conditions are shown to be both reversible and irreversible.