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The combustion of coal is responsible for nearly 40% of the world's electricity production, and char combustion accounts for about half of that amount. Clearly, an understanding of the combustion mechanism of carbon is of great importance not only because of its industrial significance but because it is a model heterogeneous reaction. A number of recent studies have been concerned with ab initio molecular orbital calculations on graphite including model chemistry and the reactions with molecular oxygen. This study is concerned with oxidation steps involving the attachment of oxygen to a graphene layer at high temperature leading to the formation of carbon monoxide, and particular attention is paid to the subsequent oxidation reactions. In addition, the reaction of oxygen with carbon catalyzed by metals inherent within the char matrix and the reaction of molecular oxygen with the analogous biomass char are investigated and their reaction paths are discussed.

The operation of centrifugal pumps can generate instabilities and pressure pulsations that may be detrimental to the integrity and performance of the pump. In the present study a numerical investigation of the time variation of pressure within a complete centrifugal pump was undertaken. A range of parameters and three flow rates were investigated and the pulsations were extracted at 15 different locations covering important pump regions. The transient flow results compared reasonably with experimental data obtained in a limited experimental survey and clearly indicated the pump locations experiencing the largest pulsation levels. It was also noted that monitoring pulsations at the top dead centre of the pump volute casing would provide a better indication of internal pump pulsations than monitoring at the discharge.

In the present study, Tween 80, a non-ionic surfactant, has been used for enhanced hydrogen production by crude glycerol bioconversion using co-culture of Enterobacter aerogenes and Clostridium butyricum. The purpose of introducing the surfactant was to decrease the crude glycerol viscosity, so that apparent solubility and bioavailability of glycerol could be improved at the expenses of pretreatment steps. Experiments were planned using central composite design (CCD); crude glycerol and Tween 80 concentrations were optimized whereas, hydrogen production, glycerol utilization and viscosity of the media were considered as responses. The response surface for quadratic model showed, Tween 80 concentration had significant effect (p < 0.05) on all the three responses. Using the optimized conditions at 17.5 g/L crude glycerol and 15 mg/L Tween 80, hydrogen production reached a maximum of 32.1 ± 0.03 mmol/L of medium. The increase in hydrogen production was around 1.25-fold in presence of Tween 80 in comparison to its absence with 25.56 ± 0.91 mmol/L production. Selected optimum conditions were also validated against absence of crude glycerol (4.69 ± 0.76), with pretreated crude glycerol (20.06 ± 0.51) and across mono-culture system (15.43 ± 0.79 to 22.14 ± 0.94). Introduction of Tween 80 to the fermentation medium improved the glycerol utilization rate, resulting in increased hydrogen production and eliminated pretreatment steps.

Abstract Bitumen recovery by steam-solvent coinjection involves the coupled thermal/compositional mechanisms for reduction of bitumen viscosity. Reliable design of such processes requires reservoir flow simulation based on a proper phase-behavior model so that the oleic-phase viscosity near the steam-chamber edge can be modeled reliably. However, the effect of bitumen characterization (e.g., the number of pseudo components used) on steam-solvent coinjection simulation has not been studied in detail, and can be realized only after running multiple reservoir simulations, which is time consuming. There are two main objectives in this paper. One is to develop a reliable method for bitumen characterization by improving the fluid characterization method that was recently developed based on perturbation from n-alkanes (PnA). The other is to develop a novel analytical method for assessing the sensitivity of a particular coinjection simulation to bitumen characterization without having to perform reservoir simulations. A simulation case study is given to validate this analytical method. A proper number of pseudo components for bitumen characterization cannot be determined without considering the effect of phase behavior on the oleic-phase viscosity at chamber-edge conditions in steam-solvent coinjection simulation. Results show that the analytical method developed in this research can detect the sensitivity of recovery simulation to bitumen characterization without performing multiple flow simulations using different sets of fluid models. The PnA-based method developed for bitumen characterization gives reliable predictions of phase behavior for bitumen/solvent mixtures with a small amount of experimental data.

Abstract This paper investigates the hydrodynamics of a seabed-mounted, bottom-hinged, flap-type wave energy converter in shallow water. A conceptual model of the hydrodynamics of the device has been formulated and shows that, as the motion of the flap is highly constrained, the magnitude of the wave force on the flap is the key determinant of power capture. The results from a physical modelling program have been used in conjunction with numerical data from WAMIT to validate the conceptual model. The work finds that designing the device to increase the wave force is more profitable than designing it to be tuned to the incident wave climate. As wave force is the primary driver of device performance it is shown that the flap should fill the water column and pierce the water surface to reduce decoupling due to wave overtopping. It is concluded that, in order to maximize capture factor at a typical North Atlantic site, the flap should be approximately 20–30 m wide, with large diameter rounded side edges, having its pivot close to the seabed and its top edge piercing the water surface.

Abstract Stable aqueous TiO2 nanofluids with different particle (agglomerate) sizes and concentrations are formulated and measured for their static thermal conductivity and rheological behaviour. The nanofluids are then measured for their heat transfer and flow behaviour upon flowing upward through a vertical pipe in both the laminar and turbulent flow regimes. Addition of nanoparticles into the base liquid enhances the thermal conduction and the enhancement increases with increasing particle concentration and decreasing particle (agglomerate) size. Rheological measurements show that the shear viscosity of nanofluids decreases first with increasing shear rate (the shear thinning behaviour), and then approaches a constant at a shear rate greater than ∼100 s−1. The constant viscosity increases with increasing particle (agglomerate) size and particle concentration. Given the flow Reynolds number and particle size, the convective heat transfer coefficient increases with nanoparticle concentration in both the laminar and turbulent flow regimes and the effect of particle concentration seems to be more considerable in the turbulent flow regime. Given the particle concentration and flow Reynolds number, the convective heat transfer coefficient does not seem to be sensitive to the average particle size under the conditions of this work. The results also show that the pressure drop of the nanofluid flows is very close to that of the base liquid flows for a given Reynolds number.

Abstract Communication between vehicles and road infrastructure can enable more efficient use of the road network and hence reduce congestion in urban areas. This improvement can be enhanced by distributed control due to its lighter computational load and higher reliability. Despite favourable impacts on traffic, little is known about the effects of such systems on near-road air quality. In this study, an End-To-End (E2E) dynamic distributed routing algorithm in Connected and Automated Vehicles (CAVs) was applied in downtown Toronto, to identify whether benefits to network throughput were associated with lower near-road NO2 concentrations. We observe significant reductions in the emissions of Greenhouse Gases (GHGs) with increased penetration of CAVs. Nonetheless, at times, the emissions of nitrogen oxides (NOx) increased with higher CAVs. Besides, a higher frequency and severity of NO2 hot-spots were observed under a 100% CAV scenario. Impacts of the proposed system on electric energy consumption in a full electric vehicle network were also investigated, indicating that the addition of CAVs that are electric did not contribute to high energy savings. We propose that such new transformative technologies in transportation should be designed with air pollution and public health goals.

Abstract Conversion of carbon contained in the solid residues (tars + biochar) derived from urban biomass gasification named herein TC would allow enhancing the yield of carbon species (CO/CO2) in synthetic gas. For this purpose, three low cost materials have been tested as possible catalysts: iron species (reduced Fe), bone meal (BM), and ashes (ash) recovered from biochar complete oxidation. The parametric study used the following as variables: air GHSV, onset of reaction temperature, reaction time to optimize CO/CO2 molar ratio and tar content in the produced gas. Results showed an autocatalytic effect of biochar leading to the catalytic conversion of approximately 78% of tars by the native metals contained in TC. The catalytic effect was further enhanced by adding Fe, BM, and extra ash. Addition of Fe catalyst resulted in significant heat generation (temperature increase of ca. 500 °C) and a twofold decrease in reaction time to consume all the carbon. Use of ash and BM as catalysts exhibit heat generation comparable to Fe, along with an improved reaction time, complete tars conversion and a CO/CO2 molar ratio to above 1.3 in the produced gas.

This paper reports on a methodology developed for studying the effects of various types of prosthetic feet on the gait of trans-femoral amputees. It is shown that an analysis in three planes of motion of not only the prosthetic, but also the sound limb provides important information on the performance of prosthetic feet. Two male trans-femoral amputees were tested with four different prosthetic feet; the Springlite II, Carbon Copy III, Seattle LightFoot and the Multiflex foot. A detailed analysis of the results of one amputee and a summary of the most important results of a second subject is presented. The tests were carried out at normal (1.16 m s(-1)) and fast (1.56 m s(-1)) walking speeds. Three dimensional gait analysis was carried out to derive the time curves of the joint angles, intersegmental moments and power at the ankle, knee and hip joints at both the prosthetic and sound sides. A higher first peak of the ground reaction force at the sound side with the Seattle LightFoot compared to that with the Springlite II, may be the result of the lower late stance dorsiflexion angle with the former. Compared to the other two feet, the Carbon Copy III and the Springlite II showed higher prosthetic dorsiflexing moments and positive power at late stance, which could assist in the push-off. The 3D intersegmental loads at the ankle and knee can be used as a guide for design and for compilation of standards for testing of lower limb prostheses incorporating flexible feet.