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The growing complexity of powertrain control strategies, software, and hardware is proving to be a significant challenge to the engineering community with regard to managing effective optimization to meet the desired performance. With an increased emphasis on shorter development time and the use of additional sensors and actuators becoming common, the increased dependence on physical models and use of complex interdependent control systems demands a thorough system understanding. This also encourages the use of process improvement tools to assist in an effective engineering process. In this paper, such a tool is discussed in its second phase of development. The Micro-HiL system will be discussed over a wide scope that focuses on the interests of the calibration and development community. The purpose of this paper is to provide an update on the Phase 2 activity of Micro-HiL development; Phase 1 was discussed in-depth at the 2011 SAE World Congress [2011-01-0703].

As demand for wall-flow Diesel Particulate Filters (DPF) increases, accurate predictions of DPF behavior, and in particular their pressure drop, under a wide range of operating conditions bears significant engineering applications. In this work, validation of a model and development of a simulator for predicting the pressure drop of clean and particulate-loaded DPFs are presented. The model, based on a previously developed theory, has been validated extensively in this work. The validation range includes utilizing a large matrix of wall-flow filters varying in their size, cell density and wall thickness, each positioned downstream of light or heavy duty Diesel engines; it also covers a wide range of engine operating conditions such as engine load, flow rate, flow temperature and filter soot loading conditions. The validated model was then incorporated into a DPF pressure drop simulator.

A unique validation method is proposed for mount designs of Lean NOx Traps (LNT's), in which characteristic curves of failure points as functions of thermal cycles and vibration amplitudes are generated. LNT's are one of the several new types of emissions control devices applied to Diesel Exhaust Systems, and they reduce the amount of NOx through chemical adsorption. Desulfation must occur nearly every hour, which involves raising the inlet gas temperature of the LNT to around 700°C to “burn off” sulfur from the catalyst, which otherwise would decrease its catalytic activity. This temperature is held for several minutes, and its cyclic occurrence has a negative effect on the long-term performance of the support mat, a major component of its mount design. As substrate temperatures increase, shell temperatures do as well, and thermal growth differences between the ceramic substrate and metallic shell cause the gap between them, which is filled by the support mat, to increase.

As Selective Catalytic Reduction (SCR) NOx abatement systems gain commercial acceptance and popularity, the need for efficiency predictive capabilities increases. To this end, a flow bench was developed capable of varying steady state inputs (temperature, flow rate and NOx concentration). The efficiencies of various SCR systems was measured and compared. This concept of a steady state flow bench approach allows for an efficient and cost effective means to evaluate comparable system designs.

The exhaust emissions standards for heavy-duty (HD) truck engines in the U.S. are facing a severe reduction of both PM and NOx emission in the year 2007, making extensive exhaust aftertreatment inevitable. Although the final emission limit values for NOx (0.20 g/bhp-hr) and NMHC (0.14 g/bhp-hr) will see a phase-in between 2007 and 2010, the PM emission limits of 0.01 g/bhp-hr will already take full effect in 2007. Engine-out emissions in the range of EURO 5 / U.S. 2002/04 will be achievable through internal measures as described in this paper. To fulfill U.S. 2007 limits, a diesel particulate filter will be necessary. The final limits taking effect in 2010 will only be fulfilled through application of NOx and particulate aftertreatment. To achieve the low engine-out emission levels, this paper will focus on both internal measures (high-EGR combustion systems and partial homogenization) and external aftertreatment systems.

As emissions regulations around the world become more stringent, emerging markets are seeking alternative strategies that align with local infrastructures and conditions. A Lean NOx Catalyst (LNC) is developed that achieves up to 60% NOx reduction with ULSD as its reductant and ≻95% with ethanol-based fuel reductants. Opportunities exist in countries that already have an ethanol-based fuel infrastructure, such as Brazil, improving emissions reduction penetration rates without costs and complexities of establishing urea infrastructures. The LNC performance competes with urea SCR NOx reduction, catalyst volume, reductant consumption, and cost, plus it is proven to be durable, passing stationary test cycles and adequately recovering from sulfur poisoning. Controls are developed and applied on a 7.2L engine, an inline 6-cylinder non-EGR turbo diesel.

Due to its high efficiency and superior durability, the diesel engine is again becoming a prime candidate for future light-duty vehicle applications within the United States. While in Europe the overall diesel share exceeds 40%, the current diesel share in the United States is 1%. Despite the current situation and the very stringent Tier 2 emission standards, efforts are being made to introduce the diesel engine back into the U.S. market. In order to succeed, these vehicles have to comply with emissions standards over a 120,000 miles distance while maintaining their excellent fuel economy. The availability of technologies-such as high-pressure, common-rail fuel systems; low-sulfur diesel fuel; oxides of nitrogen (NOx) adsorber catalysts or NACs; and diesel particle filters (DPFs)-allow the development of powertrain systems that have the potential to comply with the light-duty Tier 2 emission requirements. In support of this, the U.S.

Diesel burners introduce combustion of diesel fuel to raise exhaust gas temperature to Diesel Oxidization Catalyst (DOC) light-off or Diesel Particulate Filter (DPF) regeneration conditions, thereby eliminating the need of engine measures such as post-injections. Such diesel combustion requirement nevertheless poses challenges to burner development especially in combustion control and risk mitigation of DPF material failure. In particular, burner design must satisfy good soot distribution and heat distribution at DPF front face after meeting minimum requirements of ignition, heat release, and backpressure. In burner development, Computational Fluid Dynamics (CFD) models have been developed based on commercial codes for burner thermal and flow management with capability of predicting comprehensive physical and chemical phenomena including turbulence induced mixing, fuel injection, fuel droplet transport, diesel combustion, radiation, conjugate heat transfer and etc.

When considered along with Phase 2 Greenhouse Gas (GHG) requirements, the proposed Air Resource Board (ARB) nitrogen oxide (NOx) emission limit of 0.02 g/bhp-hr will be very challenging to achieve as the trade-off between fuel consumption and NOx emissions is not favorable. To meet any future ultra-low NOx emission regulation, the NOx conversion efficiency during the cold start of the emission test cycles needs to be improved. In such a scenario, apart from changes in aftertreatment layout and formulation, additional heating measures will be required. In this article, a physics-based model for an advanced aftertreatment system comprising of a diesel oxidation catalyst (DOC), an SCR-catalyzed diesel particulate filter (SDPF), a stand-alone selective catalytic reduction (SCR), and an ammonia slip catalyst (ASC) was calibrated against experimental data.

A novel Spatially Optimized Diffusion Alloy (SODA) material has been developed and applied to exhaust systems, which are an aggressive environment subject to high temperatures and loads, as well as excessive corrosion. Traditional stainless steels disperse chromium homogeneously throughout the material, with varying amounts ranging from 10% to 20% dependent upon its grade (e.g. 409, 436, 439, 441, and 304). SODA steels, however, offer layered concentrations of chromium, enabling an increased amount along the outer surface for much needed corrosion resistance and aesthetics. This outer layer, typically about 70μm thick, exceeds 20% of chromium concentration locally, but is less than 3% in bulk, offering selective placement of the chromium to minimize its overall usage. Since this layer is metallurgically bonded, it cannot delaminate or separate from its core, enabling durable protection throughout manufacturing processes and full useful life.

Diesel particulate trap regeneration is a complex process involving the interaction of phenomena at several scales. A hierarchy of models for the relevant physicochemical processes at the different scales of the problem (porous wall, filter channel, entire trap) is employed to obtain a rigorous description of the process in a multidimensional context. The final model structure is validated against experiments, resulting in a powerful tool for the computer-aided study of the regeneration behavior. In the present work we employ this tool to address the effect of various spatial non-uniformities on the regeneration characteristics of diesel particulate traps. Non-uniformities may include radial variations of flow, temperature and particulate concentration at the filter inlet, as well as variations of particulate loading. In addition, we study the influence of the distribution of catalytic activity along the filter wall.

In the present work we apply a computational simulation framework developed for square-cell shaped honeycomb Diesel Particulate Filters to study the filtration, pressure drop and soot oxidation characteristics of recently developed triangular-cell-shaped, high porosity wall-flow filters. Emphasis is placed on the evaluation of the applicability and adaptation of the previously developed models to the case of triangular channels. To this end Computational Fluid Dynamics, asymptotic analysis, multichannel and “unit-cell” calculations are employed to analyze filter behavior and the results are shown to compare very well to experiments available in the literature.

Stringent global emissions legislation demands effective NOx reduction strategies, particularly for the aftertreatment, and current typical liquid urea SCR systems achieve efficiencies greater than 90% [1]. However, with such high-performing systems comes the trade-off of requiring a tank of reductant (urea water solution) to be filled regularly, usually as soon as the fuel fillings or as far as oil changes. Advantages of solid reductants, particularly ammonium carbamate, include greater ammonia densities, enabling the reductant refill interval to be extended several multiples versus a given reductant volume of urea, or diesel exhaust fluid (DEF) [2]. An additional advantage is direct gaseous ammonia dosing, enabling reductant injection at lower exhaust temperatures to widen its operational coverage achieving greater emissions reduction potential [3], as well as eliminating deposits, reducing mixing lengths, and avoiding freeze/thaw risks and investments.

Tier 4 emissions legislation is emerging as a clear pre-cursor for widespread adoption of exhaust aftertreatment in off-highway applications. Large bore engine manufacturers are faced with the significant challenge of packaging a multitude of catalyst technologies in essentially the same design envelope as their pre-Tier 4 manifestations, while contending with the fuel consumption consequences of the increased back pressure, as well as the incremental cost and weight associated with the aftertreatment equipment. This paper discusses the use of robust metallic catalysts upstream of the exhaust gas turbine, as an effective means to reduce catalyst volume and hence the weight and cost of the entire aftertreatment package. The primarily steady-state operation of many large bore engine applications reduces the complication of overcoming pre-turbine catalyst thermal inertia under transient operation.

Current progress in the development of diesel engines substantially contributes to the reduction of NOx and Particulate Matter (PM) emissions but will not succeed to eliminate the application of Diesel Particulate Filters (DPFs) in the future. In the past we have introduced a Multi-Functional Reactor (MFR) prototype, suitable for the abatement of the gaseous and PM emissions of the Low Temperature Combustion (LTC) engine operation. In this work the performance of MFR prototypes under both conventional and advanced combustion engine operating conditions is presented. The effect of the MFR on the fuel penalty associated to the filter regeneration is assessed via simulation. Special focus is placed on presenting the performance assessment in combination with the existing differences in the morphology and reactivity of the soot particles between the different modes of diesel engine operation (conventional and advanced). The effect of aging on the MFR performance is also presented.

This study investigates the passive regeneration behavior of diesel particulate filters (DPFS) with various PGM loadings under different engine operating conditions. Four wall-flow DPFs are used; one uncoated and three wash-coated with low, medium, and high PGM loadings, with and without an upstream diesel oxidation catalyst (DOC). DPFs with variable pre-soot loads are evaluated at two steady state temperatures (300°C and 400°C), as well as across three levels of transients based on the 13-mode ESC cycle. Passive regeneration rates are calculated based on pre and post soot gravimetric measurements along with accumulated soot mass rates for specified exhaust mass flow rates and temperatures. Results illustrate the effect of temperature, NO₂ content, and soot loading on passive regeneration without upstream DOCs or DPF wash coatings.

In order to satisfy tightening global emissions regulations, diesel truck manufacturers are striving to meet increasingly stringent Oxides of Nitrogen (NOx) reduction standards. The majority of heavy duty diesel trucks have integrated urea SCR NOx abatement strategies. To this end, aftertreatment systems need to be properly engineered to achieve high conversion efficiencies. A EuroV intent urea SCR system is evaluated and failed to meet NOx conversion targets with severe urea deposit formation. Systematic enhancements of the design have been performed to enable it to meet targets, including emission reduction efficiency via improved reagent mixing, evaporation, distribution, back pressure, and removing of urea deposits. Multiple urea mixers, injector mounting positions and various system layouts are developed and evaluated, including both CFD analysis and full scale laboratory tests.

The definition of vehicle and powertrain level targets is one of the first tasks toward establishing where a vehicle will reside with respect to the current or future state of industry. Though development of sound quality metrics is ongoing to better correlate objective data with subjective assessments, target setting at the vehicle level is relatively straightforward. However, realization of these targets depends on effective cascading to system and component levels. Often, component level targets are derived based on experience from earlier development programs, or based on selected characteristics observed during component level benchmarking. An approach is presented here to complement current strategies for component level target definition. This approach involves a systematic concept for definition of component NVH targets based on desired vehicle level performance and a consequent target break down.

In recent years advanced computational tools of Diesel Particulate Filter (DPF) regeneration have been developed to assist in the systematic and cost-effective optimization of next generation particulate trap systems. In the present study we employ an experimentally validated, state-of-the-art multichannel DPF simulator to study the regeneration process over the entire spatial domain of the filter. Particular attention is placed on identifying the effect of inlet cones and boundary conditions, filter can insulation and the dynamics of “hot spots” induced by localized external energy deposition. Comparison of the simulator output to experiment establishes its utility for describing the thermal history of the entire filter during regeneration. For effective regeneration it is recommended to maintain the filter can Nusselt number at less than 5.

As different Diesel Particulate Filter (DPF) designs and media are becoming widely adopted, research efforts in the characterization of their influence on particle emissions intensify. In the present work the influence of a Diesel Oxidation Catalyst (DOC) and five different Diesel Particulate Filters (DPFs) under steady state and transient engine operating conditions on the particulate and gaseous emissions of a common-rail diesel engine are studied. An array of particle measuring instrumentation is employed, in which all instruments simultaneously measure from the engine exhaust. Each instrument measures a different characteristic/metric of the diesel particles (mobility size distribution, aerodynamic size distribution, total number, total surface, active surface, etc.) and their combination assists in building a complete characterization of the particle emissions at various measurement locations: engine-out, DOC-out and DPF-out.