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Nearly a third of the fuel energy is wasted through the exhaust of a vehicle. An efficient waste heat recovery process will undoubtedly lead to improved fuel efficiency and reduced greenhouse gas (GHG) emissions. Currently, there are multiple waste heat recovery technologies that are being investigated in the auto industry. One innovative waste heat recovery approach uses Thermoacoustic Converter (TAC) technology. Thermoacoustics is the field of physics related to the interaction of acoustic waves (sonic power) with heat flows. As in a heat engine, the TAC produces electric power where a temperature differential exists, which can be generated with engine exhaust (hot side) and coolant (cold side). Essentially, the TAC converts exhaust waste heat into electricity in two steps: 1) the exhaust waste heat is converted to acoustic energy (mechanical) and 2) the acoustic energy is converted to electrical energy.

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.

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.

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.

Multiple suppliers have developed new cordierite 10.5″ OD substrates in China market. One key issue is to evaluate the feasibility of their applications to diesel SCR markets. To this end, test procedures were conceived and performed towards multiple substrate characteristics. Besides typical parameters such as product dimensions, structures, and material strength, thermo-mechanical properties were characterized by hot vibration, thermal shock and thermal cycle tests. Flow performance before and after tests was characterized by a hot flow bench. Four suppliers were selected to provide product samples which went through these developed rigorous test procedures. Comparisons of multiple properties were made. Conclusions regarding their applicability and recommendations for future work are provided at the end.

To satisfy China IV emissions regulations, diesel truck manufacturers are striving to meet increasingly stringent Oxides of Nitrogen (NOx) reduction standards. Heavy duty truck manufacturers demand compact urea SCR NOx abatement designs, which integrate injectors, NOx sensors and necessary components on SCR can in order to save packaging space and system cost. To achieve this goal, aftertreatment systems need to be engineered to achieve high conversion efficiencies, low back pressure, no urea deposit risks and good mechanical durability. Initially, a baseline Euro IV Urea SCR system is evaluated because of concerns on severe deposit formation. Systematic enhancements of the design have been performed to enable it to meet multiple performance targets, including emission reduction efficiency and low urea deposit risks via improved reagent mixing, evaporation, and distribution. Acoustic performance has been improved from the baseline system as well.

In order to satisfy China IV emissions regulations, a unique design concept was proposed with injector closely coupled with Selective Catalytic Reduction (SCR) system outer body. The benefit of this design is significant in cost reduction and installation convenience. One paper was published to describe the vertical inlet layout [1]; this work is the second part describing applications of this concept to horizontal inlet configurations. For horizontal inlet pipe, two mixing pipe designs were proposed to avoid urea deposit and meet EU IV emission regulations. Computational Fluid Dynamics (CFD) technique was used to evaluate two design concepts; experiments were performed to validate both designs. CFD computations and experiments give the same direction on ranking of the two decomposition tubes. With the straight decomposition pipe design and unique perforated baffle design, no urea deposits were found; in addition, the emission level satisfied EU IV regulations.

EPA 2015 Tier IV emission requirements pose significant challenges to large diesel engine aftertreatment system (EAS) development aimed at reducing exhaust emissions such as NOx and PM. An EAS has three primary subsystems, Aftertreatment hardware, controls and fluid delivery. Fluid delivery is the subsystem which supplies urea into exhaust stream to allow SCR catalytic reaction and/or periodic DOC diesel dosing to elevate exhaust temperatures for diesel particulate filter (DPF) soot regeneration. The purpose of this paper is to discuss various aspects of fluid delivery system development from flow and pressure perspective. It starts by giving an overview of the system requirements and outlining theoretical background; then discusses overall design considerations, injector and pump selection criteria, and three main injector layouts. Steady state system performance was studied for manifold layout.

Selective Catalytic Reduction (SCR) based on urea water solution (UWS) has become a promising technology to reduce Nitrogen Oxides (NOx) emissions for mobile applications. However, urea may undergo incomplete evaporations, resulting in formation of solid deposits on the inner surfaces including walls and mixers, limiting the transformation of urea to ammonia and chemical reaction between NOx and ammonia. Numerous design parameters of SCR system affect the formation of urea deposits [1] ; they are: exhaust condition, injector type, injector mounting angle, geometrical configurations of mixer, injection rate and etc. Research has been available in urea deposits, mixers, urea injection rates and others [2,4,5,6]. In this paper, focus is placed on improving mixing structure design from baseline design of EU IV to EU V. On-road tests indicate that deposits are highly likely to occur near locations where spray and exhaust gas interact most.

Diesel Particulate Filters (DPFs) have been successfully applied for several years to reduce Particulate Matter (PM) emissions from on-highway applications, and similar products are now also applied in off-highway markets and retrofit solutions. Most solutions are catalytically-based, necessitating minimum operating temperatures and demanding engine support strategies to reduce risks [1, 2, 3, 4, 5, 6, 7, 8]. An ignition-based thermal combustion device is applied with Cordierite and SiC filters, evaluating various DPF conditions, including effects of soot load, exhaust flow rates, catalytic coatings, and regeneration temperatures. System designs are described, including flow and temperature uniformity, as well as soot load distribution and thermal gradient response.

To meet EPA Tier IV large diesel engine emission targets, intensive development efforts are necessary to achieve NOx reduction and Particulate Matter (PM) reduction targets [1]. With respect to NOx reduction, liquid urea is typically used as the reagent to react with NOx via SCR catalyst [2]. Regarding to PM reduction, additional heat is required to raise exhaust temperature to reach DPF active / passive regeneration performance window [3]. Typically the heat can be generated by external diesel burners which allow diesel liquid droplets to react directly with oxygen in the exhaust gas [4]. Alternatively the heat can be generated by catalytic burners which enable diesel vapor to react with oxygen via DOC catalyst mostly through surface reactions [5].

Selective Catalytic Reduction (SCR) has become a mainstream approach to reduce diesel engine NOx emissions. Urea Water Solution (UWS) injection and interactions with mixers and exhaust gases affect the homogeneity of ammonia distribution at catalyst inlet and solid deposits formation on walls / mixer surfaces, therefore influencing SCR performance and durability. Computational Fluid Dynamics (CFD) is used to simulate an EU V compliant SCR system with a dual baffle mixer for heavy duty diesel engines. The modeling procedure is carried out by a multi-dimensional CFD code CONVERGE that includes transient urea transport processes in an exhaust flow configuration, detailed spray break-up, evaporation, wall-film, turbulence, and Conjugate Heat Transfer (CHT) models as well as an automated mesh generation approach. Locations of urea deposits and system pressure drop are predicted and validated against measurements, providing uniformity index (UI) predictions at the catalyst inlet.