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Ammonia/urea-SCR is a mature technology, applied worldwide for the control of NOx emissions in combustion exhausts from thermal power plants, cogeneration units, incinerators and stationary diesel engines and more recently also from mobile sources. However a greater DeNOx activity at low temperatures is desired in order to meet more and more restrictive legislations. In this paper we report transient and steady state data collected over commercial Fe-ZSM-5 and V₂O₅-WO₃/TiO₂ catalysts showing high NOx reduction efficiencies in the 200 - 350°C T-range when NO and ammonia react with nitrates, e.g., in the form of an aqueous solution of ammonium nitrate. Under such conditions a new reaction occurs, the so-called "Enhanced SCR" reaction, 2 NH₃ + 2 NO + NH₄NO₃ → 3 N₂ + 5 H₂O.

Fatigue behavior of aluminum alloys under multiaxial loading was investigated with both cast aluminum A356-T6 and wrought alloy 6063-T6. The dominant multiaxial fatigue crack preferentially nucleates from flaws like porosity and oxide films located near the free surface of the material. In the absence of the flaws, the cracking/debonding of the second phase particles dominates the crack initiation and propagation. The number of cracked/debonded particles increases with the number of cycles, but the damage rate depends on loading paths. Among various loading paths studied, the circle loading path shows the shortest fatigue life due to the development of complex dislocation substructures and severe stress concentration near grain/cell boundaries and second phase particles.

Detailed chemistry and turbulence-chemistry interaction need to be properly taken into account for a realistic combustion simulation of IC engines where advanced combustion modes, multiple injections and stratified combustion involve a wide range of combustion regimes and require a proper description of several phenomena such as auto-ignition, flame stabilization, diffusive combustion and lean premixed flame propagation. To this end, different approaches are applied and the most used ones rely on the well-stirred reactor or flamelet assumption. However, well-mixed models do not describe correctly flame structure, while unsteady flamelet models cannot easily predict premixed flame propagation and triple flames. A possible alternative for them is represented by transported probability density functions (PDF) methods, which have been applied widely and effectively for modeling turbulent reacting flows under a wide range of combustion regimes.

Schlieren/shadowgraphy has been adopted in the combustion research as a standard technique for tip penetration analysis of sprays under diesel-like engine conditions. When dealing with schlieren images of reacting sprays, the combustion process and the subsequent light emission from the soot within the flame have revealed both limitations as well as considerations that deserve further investigation. Seeking for answers to such concerns, the current work reports an experimental study with this imaging technique where, besides spatial filtering at the Fourier plane, both short exposure time and chromatic filtering were performed to improve the resulting schlieren image, as well as the reliability of the subsequent tip penetration measurement. The proposed methodology has reduced uncertainties caused by artificial pixel saturation (blooming).

Emissions regulations for engine and vehicle manufacturers are bound to become more limiting to prevent greenhouse gas emissions and mitigate the negative effects that potentiate global warming. To fulfill the energy demand necessary in the transportation sector for the short-to-medium term, a parallel optimization of the internal combustion engine, powertrain and fuels is necessary. The combination of novel combustion modes like the reactivity-controlled compression ignition (RCCI), that seeks the benefits of both compression ignition and spark ignition engines, with the so-called e-fuels, that reduce the carbon footprint from well-to-wheel, is worth exploring. This work investigates the potential of the RCCI concept using OMEx-gasoline to reduce the engine-out emissions beyond the current EURO VI legislation. To do so, eight representative operating conditions from several driving cycles for heavy-duty vehicles will be explored experimentally.

In the next years, the upcoming emission legislations are expected to introduce further restrictions on the admittable level of pollutants from vehicles measured on homologation cycles and real drive tests. In this context, the strict control of pollutant emissions at the cold start will become a crucial point to comply with the new regulation standards. This will necessarily require the implementation of novel strategies to speed-up the light-off of the reactions occurring in the after-treatment system, since the cold start conditions are the most critical one for cumulative emissions. Among the different possible technological solutions, this paper focuses on the evaluation of the potential of a burner system, which is activated before the engine start. The hypothetical burner exploits the lean combustion of an air-gasoline mixture to generate a high temperature gas stream which is directed to the catalyst section promoting a fast heating of the substrate.

Methane abatement in the exhaust gas of natural gas engines is much more challenging in respect to the oxidation of other higher order hydrocarbons. Under steady state λ sweep, the methane conversion efficiency is high at exact stoichiometric, and decreases steeply under both slightly rich and slightly lean conditions. Transient lean to rich transitions can improve methane conversion at the rich side. Previous experimental work has attributed the enhanced methane conversion to activation of methane steam reforming. The steam reforming rate, however, attenuates over time and the methane conversion rate gradually converges to the low steady state values. In this work, a reactor model is established to predict steady state and transient transition characteristics of a three-way catalyst (TWC) mounted in the exhaust of a natural gas heavy-duty engine.

Modeling combustion of transportation fuels remains a difficult task due to the extremely large number of species constituting commercial gasoline and diesel. However, for this purpose, multi-component surrogate fuel models with a reduced number of key species and dedicated reaction subsets can be used to reproduce the physical and chemical traits of diesel and gasoline, also allowing to perform CFD calculations. Recently, a detailed surrogate fuel kinetic model, named C3 mechanism, was developed by merging high-fidelity sub-mechanisms from different research groups, i.e. C0-C4 chemistry (NUI Galway), linear C6-C7 and iso-octane chemistry (Lawrence Livermore National Laboratory), and monocyclic aromatic hydrocarbons (MAHs) and polycyclic aromatic hydrocarbons (PAHs) (ITV-RWTH Aachen and CRECK modelling Lab-Politecnico di Milano).

CO2 is a greenhouse gas that is believed to be one of the main contributors to global warming. Recent studies show that a combination of methanol as a renewable fuel and advanced combustion concepts could be a promising future solution to alleviate this problem. However, high unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions can be stated as the main drawback in low load operations when using methanol under advanced combustion concepts. This issue can be mitigated by modifying the stratification of the local equivalence ratio to achieve a favorable level. The stratifications evolved, and the regimes that can simultaneously produce low emissions, and high combustion efficiency can be identified by sweeping the injection timing from homogeneous charge compression ignition (HCCI) to partially premixed combustion (PPC). Understanding how the stratification of the local equivalence ratio for methanol evolves during the sweep is essential to gain these benefits.

This investigation utilizes energy analysis and statistical methods to optimize step gear automatic transmissions gear selection for fuel consumption. A full factorial matrix of simulations using energy analysis was performed to determine the optimal number of gears and gear ratios that provide the best fuel consumption performance for a particular vehicle - engine application. The full factorial matrix setup as a design of experiment (DOE) was applied to five vehicle applications, each with two engines to examine the potential differences that variations in road load and engine characteristics might have on optimal transmission gearing selection. The transmission gearing options considered in the DOE were number of gears, launch gear ratio and top gear ratio. Final drive ratio was also included due to its global influence on vehicle performance and powertrain operating speeds and torque.

With ever-demanding emission legislations in Compression Ignition (CI) engines, new premixed combustion strategies have been developed in recent years seeking both, emissions and performance improvements. Since it has been shown that in-cylinder air flow affects the combustion process, and hence the overall engine performance, the study of swirling structures and its interaction with fuel injection are of great interest. In this regard, possible Turbulent Kinetic Energy (TKE) distribution changes after fuel injection may be a key parameter for achieving performance improvements by reducing in-cylinder heat transfer. Consequently, this paper aims to gain an insight into spray-swirl interaction through the analysis of in-cylinder velocity fields measured by Particle Image Velocimetry (PIV) when PCCI conditions are proposed. Experiments are carried out in a single cylinder optical Diesel engine with bowl-in-piston geometry.

Fuel lean combustion and exhaust gas dilution are known to increase the thermal efficiency and reduce NOx emissions. In this study, experiments are performed to understand the effect of equivalence ratio on flame kernel formation and flame propagation around the spark plug for different low turbulent velocities. A series of experiments are carried out for propane-air mixtures to simulate engine-like conditions. For these experiments, equivalence ratios of 0.7 and 0.9 are tested with 20 percent mass-based exhaust gas recirculation (EGR). Turbulence is generated by a shrouded fan design in the vicinity of J-spark plug. A closed loop feedback control system is used for the fan to generate a consistent flow field. The flow profile is characterized by using Particle Image Velocimetry (PIV) technique. High-speed Schlieren visualization is used for the spark formation and flame propagation.

The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered.

Pursuing a sustainable energy scenario for transportation requires the blending of renewable oxygenated fuels such as alcohols into commercial hydrocarbon fuels. From a chemical kinetic perspective, this requires the accurate description of both hydrocarbon reference fuels (n-heptane, iso-octane, toluene, etc.) and oxygenated fuels chemistry. A recent systematic investigation of linear C2-C5 alcohols ignition in a rapid compression machine at p = 10-30 bar and T = 650- 900 K has extended the scarcity of fundamental data at such conditions, allowing for a revision of the low temperature chemistry for alcohol fuels in the POLIMI mechanism. Heavier alcohols such as n-butanol and n-pentanol present ignition characteristic of interest for application in HCCI engines, due to the presence of the hydroxyl moiety reducing their low temperature reactivity compared to the parent linear alkanes (i.e. higher octane number).

This work investigates the particulates size distribution of reactivity controlled compression ignition combustion, a dual-fuel concept which combines the port fuel injection of low-reactive/gasoline-like fuels with direct injection of highly reactive/diesel-like fuels. The particulates size distributions from 5-250 nm were measured using a scanning mobility particle sizer at six engine speeds, from 950 to 2200 rpm, and 25% engine load. The same procedure was followed for conventional diesel combustion. The study was performed in a single-cylinder engine derived from a stock medium-duty multi-cylinder diesel engine of 15.3:1 compression ratio. The combustion strategy proposed during the tests campaign was limited to accomplish both mechanical and emissions constraints. The results confirms that reactivity controlled compression ignition promotes ultra-low levels of nitrogen oxides and smoke emissions in the points tested.

Gas engines (fuelled with CNG, LNG or Biogas) for generation of power and heat are, to this date, taking up larger shares of the market with respect to diesel engines. In order to meet the limit imposed by the TA-Luft regulations on stationary engines, lean combustion represents a viable solution for achieving lower emissions as well as efficiency levels comparable with diesel engines. Leaner mixtures however affect the combustion stability as the flame propagation velocity and consequently heat release rate are slowed down. As a strategy to deliver higher ignition energy, an active pre-chamber may be used. This work focuses on assessing the performance of a pre-chamber combustion configuration in a stationary heavy-duty engine for power generation, operating at different loads, air-to-fuel ratios and spark timings.

Selective Catalytic Reduction (SCR) systems are nowadays widely applied for the reduction of NOx emitted from Diesel engines. The typical process is based on the injection of aqueous urea in the exhaust gases before the SCR catalyst, which determines the production of the ammonia needed for the catalytic reduction of NOx. However, this technology is affected by two main limitations: a) the evaporation of the urea water solution (UWS) requires a sufficiently high temperature of the exhaust gases and b) the formation of solid deposits during the UWS evaporation is a frequent phenomenon which compromise the correct operation of the system. In this context, to overcome these issues, a technology based on the injection of gaseous ammonia has been recently proposed: in this case, ammonia is stored at the solid state in a cartridge containing a Strontium Chloride salt and it is desorbed by means of electrical heating.

There is growing global interest in using renewable alcohols to reduce the greenhouse gases and the reliance on conventional fossil fuels. Recent studies show that methanol combined with partially premixed combustion provide clear performance and emission benefits compared to conventional diesel diffusion combustion. Nonetheless, high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions can be stated as the main PPC drawback in light load condition when using high octane fuel such as Methanol with single injection strategy. Thus, the present experimental study has been carried out to investigate the influence of multiple injection strategies on the performance and emissions with methanol fuel in partially premixed combustion. Specifically, the main objective is to reduce HC, CO and simultaneously increase the gross indicated efficiency compared to single injection strategy.

Nowadays the combination of strict regulations for pollutant and CO2 emissions, together with the irruption of electric vehicles in the automotive market, is arising many concerns for internal combustion engine community. For this purpose, many research efforts are being devoted to the development of a new generation of high-performance spark-ignition (SI) engines for passenger car applications. Particularly, the PC ignition concept, also known as Turbulent Jet Ignition (TJI), is the focus of several investigations for its benefits in terms of engine thermal efficiency. The passive or un-scavenged version of this ignition strategy does not require an auxiliary fuel supply inside the PC; therefore, it becomes a promising solution for passenger car applications as packaging and installation are simple and straightforward.

A computational, three-dimensional approach to investigate the behavior of diesel soot particles in the micro-channels of wall-flow Diesel Particulate Filters is presented. The KIVA3V CFD code, already extended to solve the 2D conservation equations for porous media materials [1], has been enhanced to solve in 2-D and 3-D the governing equations for reacting and compressible flows through porous media in non axes-symmetric geometries. With respect to previous work [1], a different mathematical approach has been followed in the implementation of the numerical solver for porous media, in order to achieve a faster convergency as source terms were added to the governing equations. The Darcy pressure drop has been included in the Navier-Stokes equations and the energy equation has been extended to account for the thermal exchange between the gas flow and the porous wall.