Conventional Operating Conditions Research Articles

Water-mediated chelation dynamics of dicarboxylic acid functionalized TiO2 nanoparticles for β-nucleation enhancement in isotactic polypropylene composites

ABSTRACT Isotactic polypropylene (iPP) is the most prominent form of polypropylene, and β-phase is the most resistant to impact compared to the crystalline forms. However, β-phase is the least frequently obtained under conventional operating conditions. TiO2 nanoparticles were functionalized with dicarboxylic acids as nucleating agents to promote β-crystal formation in iPP. The effects of three dicarboxylic acids – glutaric, pimelic, and azelaic – were characterized on TiO2-modified surfaces. Additionally, the interactions between TiO2 and water molecules, crucial for the formation of chelating or bridging linkages, were analyzed using Fourier Transform Infrared spectroscopy. For pimelic and azelaic acids at the polymer processing temperature, the carboxyl group band disappeared, suggesting a transition of the acid-calcium union from a bridging to a chelating linkage due to the presence of water molecules. These molecules help maintain the stability of the chains during processing. X-ray diffraction (XRD) analysis confirmed a higher content of β-crystalline structures in iPP when modified with pimelic and azelaic acids. The research indicates that water molecules, desorbed during manufacturing, facilitate the chelating form, thereby enhancing β-nucleation and improving the surface properties of iPP composites. These β-nucleated PP composites represent a promising material solution for medical device applications, offering a compelling combination of enhanced properties and cost-effectiveness.

A novel plasma-sprayed Cr/FeCrAl dual-layer coating on Zr alloy for potential high‐temperature applications

To better meet the requirements in loss-of-coolant accidents (LOCA) and conventional operating conditions in nuclear applications, this work prepared Cr, FeCrAl, and Cr/FeCrAl composite coatings on Zr alloys using plasma spraying technology. The microstructures, hardness, and high-temperature oxidation resistance of coatings are examined. The high-temperature oxidation of coatings was conducted at 1200 °C in air for 20, 40, and 60 min. All coatings exhibited characteristic lamellar microstructures accompanied by small pores. The inner layers of the coatings, benefiting from the “compacting effect” of subsequently deposited particles, displayed lower porosity and higher hardness. The order of high-temperature oxidation resistance among the coatings was determined as follows: Cr/FeCrAl coating > Cr coating > FeCrAl coating. Notably, the Cr/FeCrAl composite coating demonstrated exceptional durability even after a 60-min exposure, with no ZrO2 formation and negligible Fe and Cr diffusion. However, oxygen could still reach the Zr substrate due to inherent pores and the lamellar structure in the as-sprayed coatings. Therefore, post-treatments are suggested to mitigate or eliminate these pores, thereby improving high-temperature oxidation resistance.

An intelligent momentum perturbed variable step-size adaptive algorithm for fast converging HNANC systems

The existing methodologies for hybrid narrow-band active noise control (HNANC) systems utilises variants of the FXLMS algorithm, which typically resulted in degraded convergence and steady-state performance. In this paper, a class of variable step size (VSS) adaptive algorithms are explicitly developed for a HNANC system analyses and the convergence as well as the steady-state performance of the proposed framework are evaluated in comparison to the existing state-of-the-art. For an HNANC system designed to operate in a multiple noise environment, the VSS filtered-x LMS (VSSFXLMS) and momentum VSS filtered- x weight accumulated least mean square (MVSS-FXWALMS) algorithms are proposed. The proposed algorithm employs a variable step size that is inspired by the variable momentum factor, and combines these two parameters to drive the FXWALMS algorithm for an HNANC system in order to accomplish maximum noise reduction. In a multiple noise environment setup for an HNANC system, the proposed algorithm surpasses the state-of-the-art in nearly all conventional operating conditions. A detailed performance analysis of the proposed algorithm has been carried out using mean noise reduction ratio, steady-state power spectra at different conditions. The results demonstrate a significant improvement in noise reduction performance compared to the counterparts.

An Improved Data-Driven Method for Steering Feedback Torque of Driving Simulator

Traditional modeling methods of steering feedback torque (SFT) widely used in driving simulator are mainly physics-based, but suffers from high model complexity and low model accuracy due to the inaccurate or unknown structure, dynamics, and related parameters of the steering system, such as backlash or dry friction. For these problems, data-driven methods were considered to have advantageous in modeling such a complex yet dynamic system. However, due to the limitation of the data collected for model training from real vehicle test, the commonly used artificial neural network (ANN) cannot fully reflect the steering dynamics, and does not work well in many cases where collected data do not cover, and thus lead to poor generalization performance. In this article, a long short-term memory (LSTM) model is proposed and proved to simulate well on the dynamics of SFT, and works well in most driving conditions. A driving simulator is developed to verify the performance of different models in terms of generalization of working conditions. Based on the driving simulator data, we found that ANN failure generally arises in the transition between conventional and unconventional operating conditions, which is recognized by the proposed driving pattern recognition method. The LSTM-based modeling method can effectively solve this problem. The comparative analysis reveals that the improved LSTM model can simulate the SFT with higher accuracy and broader adaptability to driving simulator conditions.

A study on the impact of fuel injection parameters and boost pressure on combustion characteristics in a diesel engine using alcohol/diesel blends

Engine researchers focused on alcohol fuels since the invention of diesel engines in the 1900s, and the rise in petrochemical costs in the 1970s triggered this concern. This study investigates the impacts of the injection start timing, pilot injection application, and boost air pressure increase, on combustion and exhaust emissions in a common rail diesel engine fueled with ethanol/butan-2-ol/diesel blends. The lowest combustion noise was obtained in the pilot injection application as 83.8 dB in E15B3. The results indicated that the peak point of cylinder gas pressure rose by more than 5 % in the application of pilot fuel injection and advanced injection timing, compared to conventional engine operating conditions. However, maximum CO2 and NOx were seen in the pilot injection application using FBDF as 5.7 % and 670 ppm, respectively. As alcohol rate increases in fuel blends, the average 1.3 °CA in the ignition delay period was increased, while the total combustion period was shortened more than 6 °CA. This result shows that the combustion reactions of alcohol/diesel fuels occur faster than pure diesel. However, the variation in the ignition delay and total combustion periods of the test fuels considerably reduced with pilot fuel injection application. These results indicates that pilot fuel injection may be applied very controlled according to changing engine conditions. It was calculated in statistical analysis that except for the coefficient variation of the maximum pressure increase rate, the other coefficient variation values were relatively stable and below 3 %. In addition, it was determined that the results of the finite element analysis are proportional to the pressure values obtained experimentally.

In situ amplification of spin echoes within a kinetic inductance parametric amplifier.

The use of superconducting microresonators together with quantum-limited Josephson parametric amplifiers has enhanced the sensitivity of pulsed electron spin resonance (ESR) measurements by more than four orders of magnitude. So far, the microwave resonators and amplifiers have been designed as separate components due to the incompatibility of Josephson junction-based devices with magnetic fields. This has produced complex spectrometers and raised technical barriers toward adoption of the technique. Here, we circumvent this issue by coupling an ensemble of spins directly to a weakly nonlinear and magnetic field-resilient superconducting microwave resonator. We perform pulsed ESR measurements with a 1-pL mode volume containing 6 × 107 spins and amplify the resulting signals within the device. When considering only those spins that contribute to the detected signals, we find a sensitivity of [Formula: see text] for a Hahn echo sequence at a temperature of 400 mK. In situ amplification is demonstrated at fields up to 254 mT, highlighting the technique's potential for application under conventional ESR operating conditions.

Vehicle Stability Analysis under Extreme Operating Conditions Based on LQR Control.

Under extreme working conditions such as high-speed driving on roads with a large road surface unevenness coefficient, turning on a road with a low road surface adhesion coefficient, and emergency acceleration and braking, a vehicle's stability deteriorates sharply and reduces ride comfort. There is extensive existing research on vehicle active suspension control, trajectory tracking, and control methods. However, most of these studies focus on conventional operating conditions, while vehicle stability analysis under extreme operating conditions is much less studied. In order to improve the stability of the whole vehicle under extreme operating conditions, this paper investigates the stability of a vehicle under extreme operating conditions based on linear quadratic regulator (LQR) control. First, a seven degrees of freedom (7-DOF) dynamics model of the whole vehicle is established based on the use of electromagnetic active suspension, and then an LQR controller of the electromagnetic active suspension is designed. A joint simulation platform incorporating MATLAB and CarSim was built, and the CarSim model is verified by real vehicle tests. Finally, the stability of the vehicle under four different ultimate operating conditions was analyzed. The simulation results show that the root mean square (RMS) values of body droop acceleration and pitch angle acceleration are improved by 57.48% and 28.81%, respectively, under high-speed driving conditions on Class C roads. Under the double-shift condition with a low adhesion coefficient, the RMS values of body droop acceleration, pitch acceleration, and roll angle acceleration are improved by 58.25%, 55.41%, and 31.39%, respectively. These results indicate that electromagnetic active suspension can significantly improve vehicle stability and reduce driving risk under extreme working conditions when combined with an LQR controller.

Biodegradable Dissolved Organic Carbon (BDOC) Removal from Micro-Polluted Water Source Using Ultrafiltration: Comparison with Conventional Processes, Operation Conditions and Membrane Fouling Control.

The biodegradable dissolved organic carbon (BDOC) in micro-polluted water sources affects the drinking water quality and safety in the urban water supply. The conventional technology of “coagulation-sedimentation-filtration” in a water plant located in the lower reaches of the Yangtze River removed dissolved organic carbon (DOC) with a molecular weight (MW) > 30 kDa effectively, but the BDOC elimination only ranged 27.4−58.1%, due to their predominant smaller MW (<1 kDa), leading to a high residual BDOC of 0.22−0.33 mg/L. To ensure the biological stability of drinking water, i.e., the inability to support microbial growth (BDOC < 0.2 mg/L), a pilot-scale ultrafiltration process (UF, made of aromatic polyamide with MW cut-off of 1 kDa) was operated to remove BDOC as an advanced treatment after sand-filtration. Results showed the membrane flux decreased with the increase in the influent BDOC concentration and decrease in operating pressure. With an operating pressure of 0.25 MPa, the BDOC removal by UF reached 80.7%, leading to a biologically stable BDOC concentration of 0.08 mg/L. The fouling of the membrane was mainly caused by organic pollution. The H2O2−HCl immersion washing method effectively cleaned the membrane surface fouling, with a recovery of membrane flux of 98%.

Carbon Capture and Storage Energy Consumption and Performance Optimization Using Metamodels and Response Surface Methodology

Abstract Oil and gas industries have high carbon dioxide (CO2) emissions, which is a great environmental concern. Monoethanolamine (MEA) is widely used as a solvent in CO2 capture and storage (CCS) systems. The challenge is that MEA–CCS itself is an energy-intensive process that requires optimum configuration and operation, and numerous design parameters and heat demands must be considered. Thus, the current work evaluates the energy distributions and CO2 removal efficiency of a CCS installed in floating production storage and offloading units under different operating conditions of a power and heat generation hub. The optimization procedures are implemented using highly accurate surrogate models for the following responses: (1) overall power consumption of CCS, (2) CCS separation performance, and (3) CCS heating and cooling demands. The input variables considered in the present research include the following: (1) the exhaust gas compositions and mass flowrate, (2) the operating pressure and temperature parameters of CCS and the injection compression unit, (3) the structural parameters of absorber and stripper columns, and (4) MEA solution parameters. The optimum CCS configuration significantly reduces the total heating and cooling demands by 62.77% (7 × 106 kW) and the overall power consumption by 8.65% (1.8 MW), and it increases the CCS separation performance by 4.46% (97.46%) and mitigates the CO2 emissions of proper CCS by 1.02 t/h compared with conventional operating conditions.

Methane potential and degradation kinetics of fresh and excavated municipal solid waste from a tropical landfill in Colombia

The optimization of degradation processes and the management of leachate and biogas produced in landfills are key aspects for the establishment of more sustainable municipal solid waste (MSW) disposal in developing countries. In this study, biochemical methane potential (BMP) tests were used to evaluate CH4 production potential and degradation kinetics of fresh waste (FW) and five-year aged excavated waste (EW) samples from a tropical controlled landfill with compositional characteristics of developing countries. BMP tests with reconstituted samples of the biodegradable fraction of both MSW types were performed at three substrate/inoculum (S/I) ratios (0.3, 0.5 and 1.0 g VS substrate g− 1 VS inoculum), and CH4 generation parameters were determined using the first-order and modified Gompertz kinetic models. After 30-d, the best BMP results were reached at S/I ratios of 0.5 and 1.0, with cumulative CH4 productions of 528 and 433 mL CH4 g− 1 VS for FW, respectively; and 151 and 135 mL CH4 g− 1 VS for EW, respectively. The first-order kinetic model provided a good fit to BMP results for FW, whereas the modified Gompertz model showed a better adjustment to the BMP data for EW. Calculated first-order CH4 generation rates for FW and EW were in the range 0.19–0.36 and 0.23–0.25 d− 1, respectively. These results evidence the high biodegradability and CH4 potential of FW disposed of in a tropical landfill in Colombia and the reduced BMP of EW despite a relatively short period after disposal under conventional landfill operation conditions.

Wetting behavior and reactivity of liquid Si-10Zr alloy in contact with glassy carbon

In designing advanced refractory composites for highly demanding applications, reactive infiltration of liquid Si-enriched Si-Zr alloys into C-or SiC-based preforms may be a viable cost-less manufacturing process.In such cases, in view to optimize liquid assisted processes such as reactive infiltration, fundamental investigations of the interfacial phenomena occurring when the liquid Si-Zr alloys are in contact with C and SiC substrates, are key steps.For this reason, aiming to ‘‘mimic’’ the conventional operating conditions imposed within a reactive infiltration process, the contact heating sessile drop method was applied to perform a basic study concerning the interaction phenomena taking place at the interface of Si-10% at Zr alloy/Glassy Carbon substrate under an Ar atmosphere. Specifically, the contact angle values as a function of time were measured in the temperature range of 1354–1500 °C.The final contact angle values decreased slightly with an increase in temperature.Moreover, at T = 1450 °C, the contact angle increased over a larger time interval before reaching its final value. The kinetics of SiC crystal growth at the interface and the related processing parameters such as temperature and time were carefully analysed. The growth of SiC crystals and their packaging phenomenon are time and temperature-dependent phenomena.

A Model Based Analysis of Evaporative Cooling for Polymer Electrolyte Fuel Cells

Even though state-of-the-art polymer electrolyte fuel cells (PEFC) reach system efficiencies above 60 % [1], a substantial amount of heat has to be rejected to the environment. In order to facilitate the heat transfer, higher operating temperatures of PEFCs are favorable. However, the ionic conductivity of the proton exchange membrane is limiting the operating temperature substantially to about 90 °C, since it is highly dependent on a proper humidification [2]. In order to control the temperature, a dedicated cooling system is required. The state-of-the-art solution is liquid cooling which aims at transferring the waste heat to a liquid coolant that flows thru separate cooling channels in the bipolar plates. This results in high heat fluxes from the cell to the coolant and ensures a uniform temperature distribution. However, a thick and complex multi-layer design of bipolar plates is required [3] which contributes to about 75 % of stack volume and approximately 80 % of its mass [4]. The coolant is subsequently chilled in an external heat exchanger which requires a high surface area due to the small temperature gradient and thus shows a high volume demand of about 25 % of stack volume. One auspicious alternative to overcome these hindrances is evaporative cooling. In our concept, liquid water is fed to the cell through dedicated water channels in the flow field parallel to the gas channels. Consequently, the water is distributed in a specially designed gas diffusion layer (GDL) with a mixed hydrophilic and hydrophobic pattern (see Figure 1) [5]. Once in contact with the gas flow, the water in the hydrophilic lines evaporates, cools the cell by taking up the heat of evaporation and is eventually released as vapor with the exhaust gases. Concurrently, the water vapor contributes to a better humidification and thus higher ionic conductivity of the membrane, which enables higher operating temperatures. Additionally, evaporative cooling shows the potential to reduce the system volume, mass, complexity and cost up to 30 % by simplifying the design of bipolar plates and balance of plant [6]. In order to quantify the potentials and limits of evaporative cooling, a combined numerical and experimental study has been conducted in the present work. A semi-empirical zero dimensional fuel cell system model has been developed, taking into account mass and energy balances as well as electrochemistry (i.e. Nernst potential, kinetics, ohmic losses and mass transport losses). Relevant electrochemical parameters and evaporation rates have been determined experimentally from an actual evaporatively cooled differential fuel cell with an active area of 4.4 cm2 [5]. The impact of different operating conditions (i.e. temperature, pressure and stoichiometry) on the evaporation rate and thus cooling performance has been studied. Main findings show, that an increased operating temperature and stoichiometry as well as a decreased system pressure are increasing the evaporation rate and are therefore beneficial for the cooling performance. Furthermore, it is shown, that the steady state temperature which is reached when the heat of evaporation is equal to the waste heat (i.e. thermal neutrality) is dependent on system pressure, stoichiometry and current density (see Figure 2). However, the electrochemical performance is slightly decreased (-25 mV at 1 A/cm2) at operating conditions which are favorable for evaporative cooling (1.5 bara, dry gases), in comparison to conventional operating conditions. (2 bara, 80 °C, fully humidified), see Figure 3. In addition, the water balance of an evaporatively cooled fuel cell system has been investigated and it is shown, that a sufficient amount of water can be retained from the exhaust gas at condenser outlet temperatures below 60 °C to supply enough water to the stack (see Figure 4). Finally, a feasible operating window for evaporative cooling is proposed which is shifted towards higher temperatures (approx. 85 to 100 °C) and slightly lower pressures (approx. 1.5 to 2.5 bara) in comparison to conventional fuel cells.

Partial oxy-combustion technology for energy efficient CO2 capture process

Partial oxy-combustion is considered a promising carbon capture and storage technology that can lead to further energy penalty reductions. The presence of large amounts of CO2 in the flue gas should enhance the driven force in the bulk gas and hence the absorption performance. A novel concept known as Shift to Low Temperature configuration has been developed in order to strengthen the potentialities of partial oxy-combustion. This novel configuration aims at relaxing the operating conditions in the stripper based on the benefits – kinetics and driven force – observed in the absorption unit by means of shifting the operational CO2 cyclic capacity of the solvents towards lower energy requirements for solvent regeneration. In this work, three partial oxy-combustion operating conditions were tested in an experimental bench-scale CO2 capture facility. Results from the test campaign were further compared with both post-combustion and partial oxy-combustion at conventional operating conditions. The energy requirements were further improved as this novel configuration was applied, particularly using 118 °C as stripping temperature in combination with 60%v/v CO2 in the flue gas. Under these operating conditions, the energy penalty was reduced by 11% with respect to conventional partial oxy-combustion operation using the same flue gas composition – from 4.55 to 4.05 GJ/t CO2 using MEA 30 wt% as solvent. The energy penalty was further decreased by up to 64% in comparison with the post-combustion test. The results endorse the use of large CO2 cyclic capacity solvents to enhance the potentialities of the Shift to Low Temperature configuration for carbon capture applications.

The role of copper oxidation state in Cu/ZnO/Al2O3 catalysts in CO2 hydrogenation and methanol productivity

CO2 hydrogenation was carried out over a series of Cu/ZnO/Al2O3 catalysts, which were prepared by different synthesis methods (co-precipitation, ultrasound-assisted, sol-gel and solid-state). The applicative physicochemical properties of the materials and their catalytic performance were investigated. Subsequently, the preparation methodology influence on the average Cu particle size, the interactions of metals, the exposed copper phases surface area and the ratio of Cu0/Cu+, as well as its specific effect on reactions, were assessed in detail. The ultrasonic synthetic route provided increased basic active sites' number and significant methanol selectivity, compared to the conventional precipitation procedure, while it also improved the dispersion of separate Cu metallic particles, which ultimately changed the intrinsic reactive activity of CuO–ZnO. The trend of apparent CH3OH productivity rate was consistent with the Cu+/Cu0 ratio or content as well. The presence of Cu+ species at high concentration levels is thus crucial for high methanol selectivity and an extremely low selectivity towards CO at the conventional industrial operating conditions analysed. The dependence of the selective methanol production on the fraction of determined alkaline moieties was found analogous to all catalysts studied. Cu+/Cu0 oxidation state role and distribution may, therefore, aid in CO2 conversion catalyst design and optimisation.

Performance of a conventional diesel aftertreatment system used in a medium-duty multi-cylinder dual-mode dual-fuel engine

Dual-mode dual-fuel combustion stands as one of the promising techniques to allow the dual-fuel operation along the whole engine map. This concept relies on using different combustion strategies as reactivity controlled compression ignition up to medium load, then migrating to diffusive dual-fuel combustion to reach full load. With this strategy, it is possible to obtain sensible reductions in NOx and soot while providing improvements in fuel consumption and CO2 emissions. However, the excessive quantities of HC and CO together with the low exhaust temperature can compromise the diesel oxidation catalyst (DOC) efficiency. In addition, the diffusive dual-fuel combustion applied at high engine load produces considerable soot amounts that should be reduced within the diesel particulate filter (DPF).Based on these facts, this work intends to evaluate the efficiency of a commercial aftertreatment system (DOC + DPF) while operating in dual-mode dual-fuel combustion. Additionally, fundamental studies where developed to understand the impact of the combination of fuels on the exhaust hydrocarbon species. First, the DOC performance was evaluated at steady-state and transient conditions under different operating conditions fulfilling the EUVI NOx and soot limits. In parallel, the different engine-out hydrocarbon species were measured by means of a Fourier-transform infrared spectroscopy (FTIR) gas analyzer. Finally, the passive and active regeneration processes were assessed by means of different methodologies aiming to evaluate the low NOx-low soot interaction and the capability of the active regeneration in dual-fuel dual-mode (DMDF) operating conditions. The DOC results showed an improper conversion efficiency at low load operating condition, where the exhaust temperature is low. By contrast, the thermal inertia at transient conditions allowed to improve the DOC behavior at low load, reaching DOC-out emissions one order of magnitude lower than those from the steady-state tests. Concerning the DPF, it was demonstrated that the low concentration of NOx and soot produced during the combustion does not lead to sensible changes in the NO2/NOx ratio before and after the DPF, indicating a low level/absence of passive regeneration. In the case of the active regeneration, both conventional diesel combustion (CDC) and DMDF operating conditions can obtain satisfactory reduction in the total soot trapped, being the increase in the exhaust temperature consequence of the HC and CO conversion the supporting mechanism for the active regeneration in the DMDF concept.

Analytical Heat Transfer Correlation for a Multistage Steam Turbine in Warm-Keeping Operation With Air

Due to the growing share of volatile renewable power generation, conventional power plants with a high flexibility are required. This leads to high thermal stresses inside the heavy components which reduces the lifetime. To improve the ability for fast start-ups, information about the metal temperature inside the rotor and the casing are crucial. Thus, an efficient calculation approach is required which enables the prediction of the temperature distribution in a whole multistage steam turbine. Considerable improvements of the computing power and numerical simulation tools today allow detailed investigations of the heat transfer and the flow phenomena by conjugate-heat-transfer (CHT) simulations. However, these simulations are still restricted to smaller geometries mostly by the number of elements. This leads to coarser numerical meshes for larger geometries, and thus, to a reduced accuracy. A highly accurate three-dimensional-CHT simulation of a whole multistage steam turbine can only be conducted with huge computational expense. Therefore, a simplified calculation approach is required. Heat transfer correlations are a commonly used tool for the calculation of the heat exchange between fluid and solid. Heat transfer correlations for steam turbines have been developed in a multitude of investigations. However, these investigations were based on design or to some extent on part-load operations with steam as the working fluid. The present paper deals with the theoretical investigation of steam turbine warm-keeping operation with hot air. This operation is totally different from the conventional operation conditions, due to a different working fluid with low mass flow rates and a slow rotation. Based on quasi-steady transient multistage CHT simulations, an analytical heat transfer correlation has been developed, since the commonly known calculation approaches from the literature are not suitable for this case. The presented heat transfer correlations describe the convective heat transfer separately at vane and blade as well as the seal surfaces. The correlations are based on a CHT model of three repetitive steam turbine stages. The simulations show a similar behavior of the Nusselt-number in consecutive stages. Hence, the developed area related heat transfer correlations are independent of the position of the stage. Finally, the correlations are implemented into a solid body finite element model and compared to the fluid-dynamic simulations.

Physico–chemical Characteristics and Dewatering Aptitude of sMBR Sludge

Biomass concentrations 2 to 5 times higher than in a conventional activated sludge (CAS) process can be achieved in a membrane bioreactor system (MBR). These non–conventional operating conditions, i.e. high sludge concentration, can induce different sludge characteristics and dewatering aptitude, essential parameters for the optimization of the sludge post–treatment, like mechanical dewatering. The objective of this work is to study the dewatering behavior of MBR sludge, and particularly the influence of high total suspended solids concentration, on viscosity and on the key dewaterability indicators. Operating conditions are chosen to obtain MBR sludge with constant characteristics, except TSS concentration. The results confirm that the sludge viscosity is dependent on the TSS concentration. The high viscosity obtained for high TSS concentration can be unfavorable to an efficient mixing in the MBR unit, as well as to acceptable membrane permeability. However, good settleability is obtained with high TSS concentration although the sludge presents high compressibility property and a large part of bound water. This large part of bound water seems to not disturb the sludge filterability, which stays relatively good in comparison with CAS. Consequently, high–TSS concentration in MBR system can be coherent with an efficient sludge post–treatment.

Performance analysis of a Superconducting Fault Current Limiter in a power distribution substation

All substations that make up an electric energy distribution system are vulnerable to unwanted voltage or current surges, with negative implications for the affected facilities. The consequence are economic losses for the companies which operate them as well as interruption of energy delivery. This paper presents the implementation of an advanced fault current limiting device based on second generation superconducting. The purpose of the system is to avoid the negative effects of network incidents. The research analyses the performance under the conventional operating conditions of a distribution substation in Spain. The results show a reduction of peak short-circuit currents, low operating losses and the correct operation of substation with interconnected busbars. The implemented system not only prevents economic losses due to the destruction or shortening of useful life of the equipment, but also increases the quality of energy supply to customers. The conclusion from the economic analysis is that the benefit-to-cost ratio of the technology would be positive with the estimated series-produced price for the system of 100000€.

Effects of blending a heavy alcohol (C20H40O with diesel in a heavy-duty compression-ignition engine

There is an extensive worldwide search for alternate fuels that can displace fossil-based resources, yet still fit within existing infrastructure. At Argonne National Laboratory, strains of fuel have been designed that are generated by photosynthetic bacteria, eventually producing a heavy alcohol called phytol (C20H40O). Phytol’s physical and chemical properties (cetane number, heat of combustion, heat of vaporization, density, surface tension, etc.) correspond in magnitude to those of diesel fuel, suggesting that phytol might be a good blending agent in compression ignition (CI) engine applications. The main objective of this study is to investigate the feasibility of using phytol as a blending agent with diesel. Three phytol–diesel blends were chosen for evaluation: P5, P10, and P20 (5%, 10%, and 20% phytol by volume). The fuel blends were extensively analyzed to determine their chemical and physical properties, with mostly comparable values, excepting viscosity and vapor pressure. In order to understand the effects of higher viscosity phytol in the fuel injector, three-dimensional simulations of transient, turbulent nozzle flow compared the injection and cavitation characteristics of the various blends. Specifically, area and discharge coefficients and mass flow rates of diesel and phytol blends were compared under corresponding engine operating conditions. Experimental research was performed using a single-cylinder engine under conventional operating conditions to gather comparative performance and emissions characteristics of the various blends of phytol and diesel. The influence of the fuel’s chemical composition on performance and emission characteristics was captured by executing an injection timing sweep. Combustion characteristics such as the in-cylinder pressure trace were comparable for the diesel and all the blends with phytol at each of the injection timings. The diesel/phytol blends show similar emissions characteristics as the diesel. The combustion event was depicted by performing high-speed, natural luminosity endoscopic imaging. The conclusion is that phytol may be a suitable blending agent with diesel fuel for CI applications.

Assessment of the Role of Micropore Size and N-Doping in CO2 Capture by Porous Carbons

The role of micropore size and N-doping in CO2 capture by microporous carbons has been investigated by analyzing the CO2 adsorption properties of two types of activated carbons with analogous textural properties: (a) N-free carbon microspheres and (b) N-doped carbon microspheres. Both materials exhibit a porosity made up exclusively of micropores ranging in size between <0.6 nm in the case of the pristine materials and up to 1.6 nm for the highly activated carbons (47% burnoff). The N-doped carbons possess ~3 wt % of N heteroatoms that are incorporated into several types of functional groups (i.e., pyrrole/pyridone, pyridine, quaternary, and pyridine-N-oxide). Under conventional operation conditions (i.e., T ~ 0-25 °C and P(CO2) ~ 0-1 bar), CO2 adsorption proceeds via a volume-filling mechanism, the size limit for volume-filling being ~0.7-0.8 nm. Under these circumstances, the adsorption of CO2 by nonfunctionalized porous carbons is mainly determined by the volume of the micropores with a size below 0.8 nm. It was also observed that the CO2 capture capacities of undoped and N-doped carbons are analogous which shows that the nitrogen functionalities present in these N-doped samples do not influence CO2 adsorption. Taking into account the temperature invariance of the characteristic curve postulated by the Dubinin theory, we show that CO2 uptakes can be accurately predicted by using the adsorption data measured at just one temperature.