Preliminary study on the performance of biomorphic silicon carbide as substrate for diesel particulate filters

This paper presents the results of a preliminary experimental study to assess the performance of biomorphic silicon carbide when used for the abatement of soot particles in the exhaust of Diesel engines. Given its optimal thermal and mechanical properties, silicon carbide is one of the most popular substrates in commercial diesel particulate filters. Biomorphic silicon carbide is known for having, besides, a hierarchical porous microstructure and the possibility of tailoring that microstructure through the selection of a suitable wood precursor. An experimental rig was designed and built to be integrated within an engine test bench that allowed to characterizing small lab-scale biomorphic silicon carbide filter samples. A particle counter was used to measure the particles distribution before and after the samples, while a differential pressure sensor was used to measure their pressure drop during the soot loading process. The experimental campaign yielded promising results: for the flow rate conditions that the measuring devices imposed (1 litre per minute; space velocity = 42,000 L/h), the samples showed initial efficiencies above 80%, pressure drops below 20 mbar, and a low increase in the pressure drop with the soot load which allows to reach almost 100% efficiency with an increase in pressure drop lower than 15%, when the soot load is still less than 0.01 g/L. It shows the potential of this material and the interest for advancing in more complex diesel particle filter designs based on the results of this workMinisterio de Economía y Competitividad (España) MAT2013-41233-R DPI2013-46485-C3-3-RFondos FEDER MAT2013-41233-R DPI2013-46485-C3-3-RUniversidad de Sevilla VI Plan Propio I.3B - C.I. 24/05/2017 MAT2016-76526-

Optimization of micropillar sequences for fluid flow sculpting

Inertial fluid flow deformation around pillars in a microchannel is a new method for controlling fluid flow. Sequences of pillars have been shown to produce a rich phase space with a wide variety of flow transformations. Previous work has successfully demonstrated manual design of pillar sequences to achieve desired transformations of the flow cross-section, with experimental validation. However, such a method is not ideal for seeking out complex sculpted shapes as the search space quickly becomes too large for efficient manual discovery. We explore fast, automated optimization methods to solve this problem. We formulate the inertial flow physics in microchannels with different micropillar configurations as a set of state transition matrix operations. These state transition matrices are constructed from experimentally validated streamtraces. This facilitates modeling the effect of a sequence of micropillars as nested matrix-matrix products, which have very efficient numerical implementations. With this new forward model, arbitrary micropillar sequences can be rapidly simulated with various inlet configurations, allowing optimization routines quick access to a large search space. We integrate this framework with the genetic algorithm and showcase its applicability by designing micropillar sequences for various useful transformations. We computationally discover micropillar sequences for complex transformations that are substantially shorter than manually designed sequences. We also determine sequences for novel transformations that were difficult to manually design. Finally, we experimentally validate these computational designs by fabricating devices and comparing predictions with the results from confocal microscopy

Practical design considerations for secondary air injection in wood-burning cookstoves: An experimental study

Billions of households worldwide cook using biomass fires and suffer from the toxic smoke emitted into their homes. Laboratory studies of wood-burning cookstoves demonstrate that secondary air injection can greatly reduce the emission of harmful air pollution, but these experimental advancements are not easily translated into practical cookstove designs that can be widely adopted. In this study, we use a modular cookstove platform to experimentally quantify the practical secondary air injection design requirements (e.g., flow rate, pressure, and temperature) to reduce mass emissions of particulate matter (PM), carbon monoxide (CO), and black carbon (BC) by at least 90% relative to a traditional cooking fire. Over the course of 111 experimental trials, we illuminate the physical mechanisms that drive emission reductions, and outline fundamental design principles to optimize cookstove performance. Using the experimental data, we demonstrate that low-cost (<$10) fans and blowers are available to drive the secondary flow, and can be independently powered using an inexpensive thermoelectric generator mounted nearby. Furthermore, size-resolved PM measurements show that secondary air injection inhibits particle growth, but the total number of particles generated remains relatively unaffected. We discuss the potential impacts for human health and investigate methods to mitigate the PM formation mechanisms that persist

Two-phase flow patterns in turbulent flow through a dose diffusion pipe

A numerical investigation is carried out for turbulent particle-laden flow through a dose diffusion pipe for a model reactor system. A Lagrangian Stochastic Monte-Carlo particle-tracking approach and the averaged Reynolds equations with a k-e turbulence model, with a two-layer zonal method in the boundary layer, are used for the disperse and continuous phases. The flow patterns coupled with the particle dynamics are predicted. It is observed that the coupling of the continuous phase with the particle dynamics is important in this case. It was found that the geometry of the throat significantly influences the particle distribution, flow patterns and length of the recirculation region. The accuracy of the simulations depends on the numerical prediction and correction of the fluid phase velocity during a characteristic time interval of the particles. A numerical solution strategy for the computation of two-way momentum coupled flow is discussed. The three test cases show different flow features in the formation of a recirculation region behind the throat. The method will be useful for the qualitative analysis of conceptual designs and their optimisation

Техніка та технологія дезінтеграції й гравітаційного збагачення рідкіснометалічних руд

On the base of the analysis of centrifugal concentrators designs there has been justified the selection of apparatus for the rare-metal ores beneficiation. Process of pyrochlore ore grinding in mills of different types has been investigated and the expediency of use of impact centrifugal action mills to ensure selectivity of minerals disclosure has been founded. Efficient technical and technological parameters of the centrifugal action mills have been justified on the base of active experimental method. The influence of disintegration methods on technological indication of rare-metal ore beneficiation of Mazurovske deposits in centrifugal Nelson concentrator has been analyzed.На основі аналізу конструкцій відцентрових концентраторів обґрунтовано вибір апарату для збагачення рідкіснометалічних руд. Виконано дослідження процесу подрібнення пірохлорової руди в млинах різного типу та встановлено доцільність застосування млинів ударно-відцентової дії для забезпечення селективності розкриття мінералів. Методом активного експерименту обґрунтовано раціональні технічні та технологічні параметри млина ударно-відцентрової дії. Проаналізовано вплив способів дезінтеграції на технологічні показники збагачення рідкіснометалевої руди Мазурівського родовища у відцентровому концентраторі Нельсона

Supercritical Water Gasification: Practical Design Strategies and Operational Challenges for Lab-Scale, Continuous Flow Reactors

Optimizing an industrial-scale supercritical water gasification process requires detailed knowledge of chemical reaction pathways, rates, and product yields. Laboratory-scale reactors are employed to develop this knowledge base. The rationale behind designs and component selection of continuous flow, laboratory-scale supercritical water gasification reactors is analyzed. Some design challenges have standard solutions, such as pressurization and preheating, but issues with solid precipitation and feedstock pretreatment still present open questions. Strategies for reactant mixing must be evaluated on a system-by-system basis, depending on feedstock and experimental goals, as mixing can affect product yields, char formation, and reaction pathways. In-situ Raman spectroscopic monitoring of reaction chemistry promises to further fundamental knowledge of gasification and decrease experimentation time. High-temperature, high-pressure spectroscopy in supercritical water conditions is performed, however, long-term operation flow cell operation is challenging. Comparison of Raman spectra for decomposition of formic acid in the supercritical region and cold section of the reactor demonstrates the difficulty in performing quantitative spectroscopy in the hot zone. Future designs and optimization of SCWG reactors should consider well-established solutions for pressurization, heating, and process monitoring, and effective strategies for mixing and solids handling for long-term reactor operation and data collection

Surface Modification of a PCB Substrate for Better Adhesion of Inkjet Printed Circuit Structures

The robustness and service life of inkjet printed electronic circuit structures are highly influenced by the state of the interface between these structures and the substrate. In the case of polymeric substrate materials, surface modification is necessary to realise a favourable interface, as these materials are generally not very receptive to chemical bond formation with the deposited ink. This paper deals with the surface modification of a high frequency laminate (substrate) using two different techniques to improve interfacial adhesion. The techniques deployed are CF4/O2 based plasma treatment and micro structuring using pulsed laser. The plasma treatment parameters were varied systematically using a statistical design of experiments. Substrates with varying surface characteristics, resulting from different plasma treatment parameters, were subjected to post-processing steps including surface energy and surface roughness measurements. Similarly, the influence of laser treatment parameters on surface characteristics of the substrate was also studied in detail. The outcomes of these two surface modification techniques are discussed in this paper

MEMS flow sensors for nano-fluidic applications

This paper presents micromachined thermal sensors for measuring liquid flow rates in the nanoliter-per-minute range. The sensors use a boron-doped polysilicon thinfilm heater that is embedded in the silicon nitride wall of a microchannel. The boron doping is chosen to increase the heater’s temperature coefficient of resistance within tolerable noise limits, and the microchannel is suspended from the substrate to improve thermal isolation. The sensors have demonstrated a flow rate resolution below 10 nL/min, as well as the capability for detecting micro bubbles in the liquid. Heat transfer simulation has also been performed to explain the sensor operation and yielded good agreement with experimental data