Main Operating Conditions Research Articles

Optimisation of Operational Conditions during the Production of Arthrospira platensis Using Pilot-Scale Raceway Reactors, Protein Extraction, and Assessment of their Techno-Functional Properties.

The aim of the present study was to identify the optimum combination of dilution rate and depth of the culture to maximise the Arthrospira platensis BEA005B (Spirulina) productivity using 80 m2 raceway reactors. By varying these two main operational conditions, the areal biomass productivity of the reactors varied by over 55%. The optimum combination, optimised using a surface response methodology, was a depth of 0.10 m and a dilution rate of 0.33 day−1, which led to a biomass productivity of 30.2 g·m−2·day−1 on a dry weight basis when operating the reactors in semi-continuous mode. The composition of the produced biomass was 62.2% proteins, 42.5% carbohydrates, 11.6% ashes, and 8.1% lipids. The isolated proteins contained all the essential amino acids (except for tryptophan, which was not determined); highlighting the content of valine (6.8%), histidine (8.3%), and lysine (7.5%). The functional properties of the proteins were also assessed, demonstrating huge potential for their use in the development of innovative and sustainable foods.

Comparative study of two cold plasma technologies on apple juice antioxidant capacity, phenolic contents, and enzymatic activity

Cold plasma technologies are being developed as an alternative to thermal processes aiming toward preservation while retaining or improving several quality parameters. This research evaluates the use of dielectric barrier discharge (DBD) plasma and glow discharge plasma on browning enzyme activity, antioxidant capacity, and total phenolic content of apple juice. This work evaluated the effects of the main DBD plasma operating conditions, such as excitation frequencies (50–900 Hz), and glow plasma discharge operating conditions, such as air plasma flow rates (10–30 ml/min) and processing time (10–30 min). Both plasma systems partially inactivated the enzymes polyphenol oxidase and peroxidase and consequently increased apple juice's total phenolic content and antioxidant activity. DBD plasma technology presented better efficacy in increasing apple juice's total phenolic content and antioxidant capacity. DBD plasma and glow discharge plasma have the same effectiveness in inactivating browning enzymes in apple juice. Novelty impact statement This work compares two cold plasma technologies for apple juice processing. The results showed that different plasma technologies lead to different outcomes and that the right choice of technology should be made for a given goal.

Extensive experimental validation of a model for pneumatic drying of cassava starch

A pneumatic drying model, developed in a previous work, was tested and validated based on a series of 56 experiments of cassava starch drying conducted on a pilot-scale pneumatic dryer. After fitting two parameters, the average diameter of starch particles and a heat loss factor, the model predicted the effects of main operating conditions with a level of accuracy comparable to that of the experimental measurements. Transient phases with sudden variations of product feed rate were also successfully simulated. The model is therefore suitable for equipment design purposes. The experimental results showed that the size of starch particles considerably decreases with increasing air velocity. As a result, at high air velocity, despite the shorter residence time in the drying pipe, the overall drying performance is improved due to the smaller particle size. It is therefore possible to increase air velocity, and hence product feed rate and production capacity, without detrimental effect on the drying efficiency.

Design and Research on High Power Density Motor of Integrated Motor Drive System for Electric Vehicles

Although many PMSMs are used as the driving source for electric vehicle motor drive systems, there is still a gap compared with the power density index in the DOE roadmap. Considering that the motor occupies a large space in the motor drive system, it is of great significance for the system to increase the motor power density and thus reach the system power density index. This article starts with electrical machine basic design theory and finds the motor power density influence factors. Guided by the theory and considering motor driver influence, this article proposes a high power density motor for electric vehicle integrated motor drive system. The motor for the system is a five-phase interior permanent magnet synchronous motor (IPMSM) with a double-layer rotor structure and fractional slot distributed winding. Compared with Ver1.0 motor, Ver2.0 motor power density improves significantly. In order to prevent damage from excessive temperature, a temperature field solution model is established in this article to compare the cooling effect and pressure loss of the spiral, dial, and axial water jackets. The temperature is checked at motor main operating conditions using an optimal cooling structure. Finally, the power density of the designed Ver2.0 motor reaches 3.12 kW/kg in mass and 15.19 kW/L in volume.

Methyl Oleate Synthesis by TiO2Photocatalytic Esterification of Oleic Acid: Optimisation by Response Surface Quadratic Methodology, Reaction Kinetics and Thermodynamics

AbstractMethyl oleate, an example of a FAME (fatty acid methyl ester), was produced by oleic acid (OA) photoesterification with TiO2and UVA light. Different parameters were evaluated and optimised: catalyst pretreatment, temperature (25–65 °C), catalyst loading (1–30 % w/wOA) and oleic acid : alcohol molar ratio (1 : 3–1 : 55). Response surface quadratic methodology obtained by central composite rotational design (RSM‐CCRD) was used to evaluate the main operational conditions of the photoesterification process. A high conversion of 98 % (±0.8) at 55 °C, 20 % TiO2(w/wOA), and 1(OA) : 55(methanol) molar ratio was achieved. The photoesterification mechanism is furthermore proposed. The Langmuir‐Hinshelwood kinetic model considered the forward and backward reaction as first‐order fits with the best accuracy (R2of 0.997). The thermodynamic results (ΔG338.15K=−20.75 kJ/mol, ΔH=13.75 kJ/mol, and ΔS=0.47 kJ/mol.K) indicate that the operating conditions are important, both to supply the energy requirement of the reaction, but also to increase the miscibility of the reactants.

Thermodynamic approach to foresee experimental CO2 reduction to organic compounds

Anaerobic gas fermentation is a promising approach to transform carbon dioxide (CO2) into chemical building blocks. However, the main operational conditions to enhance the process and its selectivity are still unknown. The main objective of this study was to trigger chain elongation from a joint perspective of thermodynamic and experimental assessment. Thermodynamics revealed that acetic acid formation was the most spontaneous reaction, followed by n-caproic and n-butyric acids, while the doorway for alcohols production was bounded by the selected conditions. Best parameters combinations were applied in three 0.12 L fermenters. Experimentally, n-caproic acid formation was boosted at pH 7, 37 °C, Acetate:Ethanol mass ratio of 1:3 and low H2 partial pressure. Though these conditions did not match with those required to produce their main substrates, the unification of both perspectives yielded the highest n-caproic acid concentration (>11 g L−1) so far from simple substrates, accounting for 77 % of the total products.

Modeling of Vacuum Temperature Swing Adsorption for Direct Air Capture Using Aspen Adsorption

The paper evaluates the performance of an adsorption-based technology for CO2 capture directly from the air at the industrial scale. The approach is based on detailed mass and energy balance dynamic modeling of the vacuum temperature swing adsorption (VTSA) process in Aspen Adsorption software. The first step of the approach aims to validate the modeling thanks to published experimental data for a lab-scale bed module in terms of mass transfer and energy performance on a packed bed using amine-functionalized material. A parametric study on the main operating conditions, i.e., air velocity, air relative moisture, air temperature, and CO2 capture rate, is undertaken to assess the global performance and energy consumption. A method of up-scaling the lab-scale bed module to industrial module is exposed and mass transfer and energy performances of the industrial module are provided. The scale up from lab scale to the industrial size is conservative in terms of thermal energy consumption while the electrical consumption is very sensitive to the bed design. Further study related to the engineering solutions available to reach high global gas velocity are required. This could be offered by monolith-shape adsorbents.

The role of Cerium, Europium and Erbium doped TiO2 photocatalysts in water treatment: A mini-review

Heterogeneous photocatalysis is a promising environmentally friendly strategy for removing contaminants of emerging concern from water, with titanium dioxide being the most studied and exploited photocatalyst, thanks to its good optical and electrical properties. However, one of the main drawbacks linked to its use is the limited absorption of sunlight; several strategies have been explored to enhance the absorption in visible light region and, among them, the doping with elements belonging to the lanthanoid series is particularly attractive. This review focuses on these systems analysing the cases of Cerium, Europium and Erbium doped TiO2 and giving an overview on the structural, optical and electronic characteristics of these materials. Synthesis procedures, inserted dopant percentages, structural and optical properties and the main operating conditions adopted in the photodegradation studies are considered. Particular attention is devoted to unravel the effect induced by the introduction of lanthanoids on the energy gap, on the recombination rate of photogenerated electron-hole pairs and on the inhibition of phase transition from anatase to rutile.

Design, Computational Modelling and Experimental Characterization of Bistable Hybrid Soft Actuators for a Controllable-Compliance Joint of an Exoskeleton Rehabilitation Robot

This paper presents the mechatronic design of a biorobotic joint with controllable compliance, for innovative applications of “assist-as-needed” robotic rehabilitation mediated by a wearable and soft exoskeleton. The soft actuation of robotic exoskeletons can provide some relevant advantages in terms of controllable compliance, adaptivity and intrinsic safety of the control performance of the robot during the interaction with the patient. Pneumatic Artificial Muscles (PAMs), which belong to the class of soft actuators, can be arranged in antagonistic configuration in order to exploit the variability of their mechanical compliance for the optimal adaptation of the robot performance during therapy. The coupling of an antagonistic configuration of PAMs with a regulation mechanism can achieve, under a customized control strategy, the optimal tuning of the mechanical compliance of the exoskeleton joint over full ranges of actuation pressure and joint rotation. This work presents a novel mechanism, for the optimal regulation of the compliance of the biorobotic joint, which is characterized by a soft and hybrid actuation exploiting the storage/release of the elastic energy by bistable Von Mises elastic trusses. The contribution from elastic Von Mises structure can improve both the mechanical response of the soft pneumatic bellows actuating the regulation mechanism and the intrinsic safety of the whole mechanism. A comprehensive set of design steps is presented here, including the optimization of the geometry of the pneumatic bellows, the fabrication process through 3D printing of the mechanism and some experimental tests devoted to the characterization of the hybrid soft actuation. The experimental tests replicated the main operating conditions of the regulation mechanism; the advantages arising from the bistable hybrid soft actuation were evaluated in terms of static and dynamic performance, e.g., pressure and force transition thresholds of the bistable mechanism, linearity and hysteresis of the actuator response.

A mathematical model for the virtual simulator of the power unit electrical part

The mathematical model is developed for a virtual training system (simulator) of the power unit electrical part operators of a thermal (nuclear) power plant. The model is used to simulating the main operating conditions of the power unit electrical part: generator idling, generator synchronization with the power system, excitation shifting from the main unit to the backup one and vice versa, switching in the power unit auxiliary system, and others. Furthermore, it has been implemented modelling some probable emergency conditions within a power plant: incomplete phase switching, damage to standard power unit equipment, synchronous oscillations, asynchronous mode, etc. The model of the power unit electrical part consists of two interacting software units: models of power equipment (turbine, generator with excitation systems, auxiliary system) and models of its control systems, automation, relay protection and signalling. The models are represented by the corresponding algebraic-differential equations that provide real-time mapping power unit processes at the operator’s request. The developed model uses optimal solving algebraic-differential equations to ensure the virtual process behaviour in real-time. In particular, the implicit Euler method is used to solve differential equations, which is stable when simulating processes in significant disturbances, such as accidental disconnection of the unit from the power system, tripping and energizing loads, generator excitation loss, etc.

JUSTIFICATION OF FILLERS USING IN THE BEARING STRUCTURES COMPONENTS OF FREIGHT CARS

To reduce the load on the freight cars frames under operational conditions, it has been suggested that to use fillers in their components. Fillers using is advisable in the most loaded elements of the bearing structure, namely, the spine beam. Therefore, a necessary condition for filler using in the spine beam is the creation of its closed structure. The dynamic load of railcars was carried out, taking into account the proposed provisions. Calculations have shown with filler using, the maximum accelerations acting on the bearing structures of wagons are 4% lower than those accelerations obtained for bearing structures without fillers. The results of determining the main strength indicators of bearing structures of freight cars are presented, taking into account the fillers using in their components. It has been established that the strength of the frames of the considered types of wagons under the main operating conditions is ensured. At the same time, the maximum equivalent stresses in the bearing structures of wagons are 4-9% lower than those in typical frame structures. The conducted research will contribute to the creation of innovative structures of rolling stock and reduce the cost of its maintenance work in operation.

Modeling and experimental validation of a triple-screw pump for internal combustion engine cooling

• Development of the mathematical model of a triple-screw pump. • Idler screws without a dedicated support determine complex friction phenomena. • Experimental assessment of volumetric and mechanical performances. • Maximum global efficiency achieved equal to 70% • 8.2% efficiency improvement on ICE cooling application compared to centrifugal pump. Internal Combustion Engine (ICE) cooling system is receiving a new technological interest for the influence it has on primary harmful and CO2 emissions reduction. Improvements on pump efficiency are requested to reduce its required energy during real on-the-road operation. Present technology always considers centrifugal pumps whose efficiency is highly dependent on rotational speed: consequently, pumps designed to have a very high efficiency at design point, show poor performances during usual operation, wasting energy. This study aims to assess the screws pumps potentiality to substitute the traditional centrifugal pumps for engine cooling. The main advantage is that positive displacement pumps have an efficiency ideally non-dependent on rotational speed, flow rate and head delivered, so having requirements that can fit more the engine cooling features. A novel comprehensive zero-dimensional mathematical model has been formulated to predict the performances of triple-screw pumps, in terms of volumetric, indicated and mechanical efficiency as a function of main operating conditions of the pump. A wide experimental activity has been done, resulting in a good agreement with predictions in spite of the manufacture of the pump, which privileges a low-cost solution as it is requested for the specific sectors of application. The model, once experimentally validated, demonstrates a high validity as virtual platform for a model-based design, thus offering the possibility to include design aspects particularly suitable for engine cooling systems. At last, by simulating the World Harmonized Transient Cycle on an F1C IVECO 3l engine, the triple-screw pump shows an average efficiency about 8% greater than that of the centrifugal pump, leading to an energy saving equal to 18.5%. This result leads the way to the use of screws pumps also in the engine cooling system of an on-the-road vehicle, which could represent a new potential application, never considered before.

Anaerobic Digestion Process Control Using a Data-Driven Internal Model Control Method

Anaerobic digestion processes offer the possibility for wastewater treatment while obtaining a benefit through the obtained biogas. This paper aims to continue the effort to adopt data-driven control methods in the case of anaerobic digestion processes. The paper proposes a data-based Internal Model Control approach applied to an anaerobic digestion process. The paper deals extensively with the issue of choosing the reference model and proposing an engineering approach to this issue. The paper also addresses the issue of verifying robust stability, a very important aspect considering the uncertainties that characterize bioprocesses in general. The approach proposed in the paper is validated through a numerical simulation using the Anaerobic Digestion Model No. 1. During the validation of the proposed control solution, the main operating conditions were analyzed, such as the setpoint tracking performance, the rejection of disturbance generated by variations in the influent concentration, and the effect of the measurement noise on the controlled variable.

Chemoresistive metal oxide gas sensor: Working principles and applications

The aim of this paper is to explain to young students why chemoresistive metal oxide semiconductors (MOS) gas sensors are important and widely employed in many applications. The paper deals with the fundamentals principles of these devices and their continuous improvement, due to high level of compatibility with microelectronics technology and the employment of nanostructured materials as sensing interfaces. The main operating conditions and mechanisms are also described, in order to better understand the guidelines followed to improve these devices in terms of sensing performances (sensitivity, selectivity, fast response/recovery time, repeatability, and reliability) finalized to their practical applicability. Finally, we suggest a possible brief activity on how to explore gas <sensor employment and operating features in a classroom.

Analytical model for thermal efficiency of organic Rankine cycles, considering superheating, heat recovery, pump and expander efficiencies

This article proposes a new analytical model that calculates the thermal efficiency of subcritical Organic Rankine Cycles (ORCs) and integrates the main cycle components and parameters in a single analytical solution accounting the effect of turbine and pump isentropic efficiencies, heat recuperation, superheating, fluid type, and hot and cold reservoir temperatures. Previous analytical models for ORCs covered neither heat recuperation, nor pump isentropic efficiency, which are important features for improving the cycle thermal efficiency. The analytical solution was compared with numerical solutions of ORCs for 22 fluids, and the model showed highly accurate for wet and isentropic fluids. The highest percentage divergences were verified for both dry fluids of heavier molecular weight and evaporation temperatures close to the fluid́s critical temperature. The model can be applied to most fluids and for the main operation conditions of ORC applications.

The Dynamic and Strength Analysis of an Articulated Covered Wagon with the Circular Pipe Design

An articulated covered wagon design was developed. The wagon feature is that the body-bearing elements are made of circular pipes. This technical solution made it possible to reduce the tare weight of the wagon while ensuring the strength conditions. Mathematical simulation of the dynamic loading of the developed articulated covered wagon design was carried out under the main operating conditions. In the calculations of the observed quantities, an application of symmetry with regard to the longitudinal axis of the wagon was used. The accelerations, as the components of the dynamic load acting on the wagon, were determined. The dynamic loading computer simulation results of the developed wagon design are also presented. The strength analysis of the articulated covered wagon supporting structure made it possible to conclude that the strength indexes were within the allowed limits. The wagon bearing structure was analyzed for fatigue strength. The weld strength analysis results of the most loaded part of the wagon-bearing structure are presented. The results obtained for the desired quantities revealed their symmetrical distribution in the wagon structure. This research will contribute to improving the efficiency of railway transport operation.

Fixed-bed column dynamics of ultrasound and Na-functionalized diatomite to remove phosphate from water.

A continuous fixed-bed column study was used to evaluate phosphate adsorption performance of U-D-Na which was functionalized by the cheap NaCl reagent after simple ultrasonic purification of diatomite. In this work, various effect factors, including flow rate, initial phosphate concentration, and the bed height, on breakthrough performance of fixed column were investigated. Experimental results demonstrated that the breakthrough time declined with the increase of inlet phosphate concentration and feed rate, whereas the increase of bed height turned out to significantly extend the breakthrough time. The dynamic adsorption process could be well fitted by the Thomas model, with a correlation coefficient R2 > 0.9000 under main operating conditions. A thrice loop of effective regeneration was achieved with 0.1 M hydrochloric acid eluent and deionized water. The maximum removal rate for phosphate was more than 95% in the column adsorption process. The results proved that U-D-Na could be used as a better alternative phosphate adsorbent for wastewater in a continuous column sorption process.

Francis 99 CFD through RapidCFD accelerated GPU code

Francis turbines research and development (R&D) requires performance assessment through hydraulic laboratory model testing which can be assisted by auxiliary tools like computational fluid dynamics (CFD), widely used recently. CFD has a history of seeking and requiring ever higher computational performance (HPC) because of the parallelism where Graphics Processor Units (GPUs) have emerged as a major paradigm for solving complex computational problems. However, their implementation to CFD solvers is still a challenge and the tremendous computational power of the GPUs has been wasted. This work presents how the open source RapidCFD code, based on OpenFOAM and ported to Nvidia CUDA, enabled GPUs to be able of running almost entire simulations in thousands of parallel stream cores packed in small form factor hardware in order to solve the incompressible Reynolds-Average-Navier-Stokes (RANS) equations. The simulations were based on a full 3D Francis turbine case which consisted of a grid domain of 23 million cells, including spiral case with stay vanes, distributor, runner and draft tube. CFD results of shaft torque, static pressure and velocity components in steady state deploying a multiple reference frame (MRF) motion approach were compared with available experimental data for main operation conditions at different distributor opening angles: best efficiency operation point (BEP), part load operation point (PL) and full load operation point (HL). The obtained data showed that by transferring directly all the computations to the GPUs, it is possible to make CFD simulations faster compared with central processing units (CPUs). Thus, it is expected to obtain an affordable low computational cost in optimization processes or full range performance evaluations.

Non-Energetic Chemical Products by Fermentation of Hydrolyzed Sewage Sludge

Hydrolysis and the solubilization of sewage sludge processes are important tools to obtain small and medium molecules with different application perspectives. Although the production of biomethane and other products such as biohydrogen from sludge as biofuel alternatives has been profusely studied, the current perspectives are mainly focused on the use of the sludge hydrolysate to produce non-energy bioproducts and biomaterials. In this review, the most recent bibliography dealing with the use of sludge hydrolysates as fermentation media for the bioproduction of new non-energetic products with industrial interest is here revised and discussed. In this regard, the main research effort has been focused on the bioproduction of short-chain fatty acids due to their direct use in industrial applications or as a carbon source for polyhydroxyalkanoates-producing microorganisms. The use of sludge hydrolysates as fermentation media using pure cultures to produce more complex biomolecules, such as enzymes or lipids, is gaining interest, but it remains an undervalued topic. The literature has been divided into processes where hydrolysis and fermentation stages took place simultaneously or separately, centering them on the effect of the main operational conditions on the yields and properties of the corresponding metabolites produced. In general, the main limiting step of these kinds of processes is the proper solubilization and hydrolysis of the sludge, which can improve the bioassimilation of nutrients and, subsequently, the productivities and compositions of the metabolites obtained. Biological and/or thermal pretreaments are the options more profusely employed, which are frequently assisted by different promoters such as oxidants, surfactants, or cation exchange resins.

Optimization and statistical analysis of the effect of main operation conditions on the physical characteristics of solid and hollow cylindrical pellets

Optimization and statistical analysis of the effect of main operation conditions on the physical characteristics of solid and hollow cylindrical pellets