A One-Dimensional Model for Particulate Deposition and Hydrocarbon Condensation in Exhaust Gas Recirculation Coolers

Cooled exhaust gas recirculation (EGR) is widely used in diesel engines to control engine out NO_x (oxides of nitrogen) emissions. A portion of the exhaust gases is recirculated into the intake manifold of the engine after cooling it through a heat exchanger. EGR cooler heat exchangers, however, tend to lose efficiency and have increased pressure drop as deposit forms on the heat exchanger surface. This adversely affects the combustion process, engine durability, and emissions. In this study, a 1-D model was developed to simulate soot deposition, soot removal, and condensation of several hydrocarbon (HC) species in a circular tube with turbulent gas flow at constant wall temperature. The circular tube, which makes up the computational domain in the model, represents a single channel from any EGR cooler geometry. The model takes into account soot particle deposition due to thermophoresis, diffusion, turbulent impaction, and gravitational drift. However, thermophoresis was found to be the most dominant deposition mechanism for boundary conditions at which EGR coolers typically operate. Soot removal was modeled by considering a force balance between the drag and van der Waals forces. A lognormal distribution of particles was assumed at the tube inlet. The evolution of the particle distribution in the bulk flow along the tube as well as the mass distribution in the deposit layer on the tube walls is predicted by the model. Condensation of six HC species between C₁₅-C₂₄ alkanes was also modeled. Predictions made by the model are in reasonably good agreement with experimental data obtained from a laboratory reactor under the same boundary conditions. There are several assumptions and simplifications built into the model, which can be refined further to improve it.

Copyright 2012 American Association for Aerosol Research     

An Innovative Tree Gradient Boosting Method Based Image Object detection from a Uniform Background Scene

Object detection is a wide area problem domain in the field of computer and machine vision. Complex background adds challenge and error margin as well to the problem significantly lot algorithms for object detection are hard to comply with occlusion and pixel bending moment affect. In this paper a highly robust algorithm ORBTRIAN for a less resolution image has been proposed and implemented using ORB detection with gradient boosting machine learning algorithm. The work has been compared with Adaboost and Surf based technology. The analysis shows 3.8% increase in performance of earlier model. The feature points extracted from ORB method are further processed to reduce the processing further. Only those points are selected which are triangularly farthest from centroid of it and only 1 point of feature selected. Thus the result is around 28%, much faster than earlier computation. The tree based GB has been implemented in this algorithm. With more number of feature points more classes need to be recognized and hence the computations performed is required an unreasonable amount of effort and time. So some nearby classes are assigned at same level using our algorithm to reduce the number of tree nodes. Overall performance of the proposed algorithm shows a significant increase in efficiency in computation time.     

Rippled and Helical MoS<Subscript>2</Subscript> Nanowire Catalysts: An Aberration Corrected STEM Study

Abstract  

Aberration corrected (C_s) scanning transmission electron microscopy (STEM) has been used for the first time to characterize MoS₂ catalysts (supported on Al₂O₃ substrates) to provide detailed information of its shape and structure. The high-resolution imaging reveals unprecedented morphologies present in the MoS₂ catalyst that have never been observed before with other experimental techniques because of the insufficient image contrast and/or resolution. High angle annular dark field (HAADF)-STEM images shows very clearly that the catalyst is formed by elongated chains with a twisted and helical structure. Based on the HAADF-STEM images, we built three atomic models to illustrate the different morphologies found in the MoS₂ catalyst. The existence of these nanostructures opens the posibility for novel catalyticaly active edge morphologies in MoS₂-based nanocatalysts.     

Synthesis of Sulfonated Carbon Nanocage and Its Performance as Solid Acid Catalyst

Abstract  

A carbon nanocage material (CKT) was first successfully sulfonated by introducing sulfophenyl groups on the surface of pore channels through benzenesulfonic acid-containing aryl radical in situ generated from the reaction of 4-aminobenzenesulfonic acid and isoamyl nitrite in water. The sulfonated carbon nanocage material (S-CKT) was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, powder small-angle X-ray diffraction and nitrogen sorption measurements. The results showed that the S-CKT still possess the high specific surface area (787 m²/g) and uniform mesoporous (pore diameter 4.7 nm) structures, although the structure of S-CKT is slightly disorder, compared with its unsulfonated precursor. S-CKT, as a carbon-based solid acid catalyst, showed good catalytic performance and reusability in the cross-Aldol condensation of ketones with aromatic aldehydes under solvent-free condition.     

Nanosized Mn(acac)<Subscript>3</Subscript> Anchored on Amino Functionalized Silica for the Selective Oxidative Synthesis of 2-arylbenzimidazoles, 2-arylbenzothiazoles and Aerobic Oxidation of Benzoins in Water

Abstract  

Silica functionalized Mn(acac)₃ was prepared and employed for the one-pot oxidative synthesis of 2-arylbenzimidazoles, 2-arylbenzothiazoles; and oxidation of benzoins to benzils under air atmosphere using water as the reaction medium. Environmentally friendly procedure, chemoselectivity and excellent yields are main advantages of this procedure. In all the cases, the catalyst was found to be highly active and selective; passes hot filtration test successfully; and could be recycled several times with a slight loss of activity.     

Selective Oxidation of Glycerol Catalyzed by Rh/Activated Carbon: Importance of Support Surface Chemistry

Abstract  

Noble metal catalysts (Pt, Ir, Pd, Rh, Au) supported on activated carbon were assessed for glycerol oxidation. Rhodium is a highly efficient catalyst when the support has neutral or basic properties. The surface chemistry of activated carbon plays a key role in the performance.     

Gas-phase Photocatalytic Oxidation of Acrylonitrile on Sulphated TiO<Subscript>2</Subscript>: Continuous Flow and Transient Study

Abstract  

The gaseous products of photocatalytic oxidation (PCO) of acrylonitrile on sulphated P25 in concentrations from 10 to 100 ppm at 60 to 130 °C were CO₂, HCN and HNCO. This photocatalyst showed disproportionally improved performance at higher temperature and longer retention times. The temperature-programmed oxidation (TPO) after PCO disclosed possible reaction routes.