Air Feed Research Articles

Statistical optimization for preparing nanofibrous mats of polybutylene adipate co‐terephthalate/poly(vinylpyrrolidone) blends by solution blow spinning

AbstractSolution blow spinning (SBS) is used to make poly(butylene‐adipate‐co‐terephthalate) (PBAT) and poly(vinylpyrrolidone) (PVP) blend nanofibers and study the effect of process parameters on their formation. A 34–1 fractional factorial statistical model with three levels and four factors was applied. The factors included the concentration of PVP (wt%) in the PBAT polymer matrix, pressurized air pressure (psi), working distance (cm), and feed rate (ml h−1). The linear and quadratic effects were analyzed using a Pareto chart and verified in a well‐adjusted response surface model. The PVP concentration and working distance had a significant effect on the production of nanofibers. The nanofibrous mats were evaluated by scanning electron microscopy (SEM) and had a mean diameter ranging from 164 to 656 nm. A higher concentration of PVP and a shorter working distance resulted in lower mean fiber diameter. In addition, X‐ray diffraction revealed an increase in the degree of crystallinity of the nanofibrous PBAT due to a greater degree of packing among the polymer molecules. However, the addition of PVP to the polymer matrix is associated with a reduction in the degree of crystallinity of the nanofibrous mat.

On the nonlinear dynamics of biomass throated tubular gasification reactors

The problem of modeling the complex nonlinear dynamics of continuous biomass throated gasification tubular reactors is addressed. The problem is solved with first principles modeling and efficient discretization-based bifurcation analysis, yielding a systematic and tractable means to characterize: (i) steady-state (SS) multiplicity, (ii) robust stability, (iii) bifurcation behavior, and (iv) transient behavior. The approach is illustrated and tested with a commercial Imbert pilot scale reactor case example, studied before with experiments and simulation, and with multiplicity-bifurcation assessment as open problem. It was found that: (i) the nominal operation is tristable (with three stable steady-states -SSs- and two unstable ones), (ii) the reactor can bebi or tristable (with three or five SSs, respectively), depending on the within-range air feed flow-biomass moisture content value pair, (iii) there are not limit cycles (LCs), and (iv) the transient behavior agrees with the multiplicity structure found in this study and reported experimental data. The developments and results are put in perspective with previous related studies.

Si nanocone structure fabricated by a relatively high-pressure hydrogen plasma in the range of 3.3–27 kPa

In this study, we prepared a silicon nanocone structure using a relatively high-pressure H2 plasma in the range of 3.3–27 kPa. The silicon sample with the prepared nanocone structure exhibited a black surface. We investigated the dependence of the silicon nanocone formation behavior on various experimental parameters such as H2 pressure, processing time, substrate temperature, input power, and substrate bias. A small amount of air feed and a thin native oxide layer are desirable for the nanocone formation. Furthermore, the silicon temperature during plasma exposure plays an important role in increasing the silicon nanocone height. In addition, the polarity of the substrate bias drastically changes the surface structure from the nanocone in the case of a negative bias to a low-aspect-ratio pyramidal structure in that of a positive bias. This result implies that the anisotropic ion incidence is important for nanocone formation, despite the relatively high process pressure.

Using LSTM and PSO techniques for predicting moisture content of poplar fibers by Impulse-cyclone Drying.

Impulse-cyclone drying (ICD) is a new type of pretreatment method to remove the excess moisture of wood fibers (WFs) with high speed and low energy consumption. However, the process parameters are often determined by the experience of the process operators, thus the quality of WF drying lacks an objective basis and cannot be ensured. To address this issue, this study adopted the long short-term memory (LSTM) neural network, backpropagation neural network, and Central-Composite response surface method to establish a moisture content (MC) prediction model and a process parameter optimization model based on single-factor experiments. The initial MC, inlet air temperature, feed rate, and inlet air velocity were taken as the experimental factors, and the final MC was taken as the inspection index. The parameters of LSTM were optimized by particle swarm optimization (PSO) algorithm, and the predicted value of MC was fitted to the model. The PSO-optimized LSTM had higher prediction accuracy than did the typical prediction models. The optimal process for the targeted MC, which was obtained by PSO, was featured with an initial MC of 10.3%, inlet air temperature of 242°C, feed rate of 90 kg/h, and inlet air velocity of 8 m/s. PSO-LSTM could be a new approach for predicting the MC of WFs, which, in turn, could provide a theoretical basis for the application of ICD technology in the biomass composite industry.

Optimizing the performance of sweeping gas membrane distillation for treating naturally heated saline groundwater

The performance of a sweeping gas membrane distillation (SGMD) was evaluated for treating naturally heated saline groundwater. The naturally heated groundwater condition is projected to be a favourable match for SGMD as it eliminates the need for thermal requirement. Further, compared to the current scenario of using reverse osmosis (RO), SGMD will enable to eliminate the cooling tower requirement to cool down the groundwater prior to RO. Detail examination on SGMD operating settings revealed the importance of feed temperature and air flow settings in enhancing the SGMD permeate flux. Meanwhile, the feed flow rate and air temperature only minimally influenced the SGMD performance. SGMD cooling conditions played a key role towards enhancing the specific energy consumption and economic viability of its performance. The air cooling (fan and fin combination) was identified to be superior over the water cooling and thermo-electric element addition air cooling combinations. At optimum operating settings, SGMD was able to treat hot saline groundwater with an average permeate flux of 3.0 kg/m2h and attain high quality fresh water with over 98% salt rejection. Under optimum operating setting and due to the opportunity to eliminate thermal heating source, SGMD is able to attain matching economic rates (both capital and operational expenditure) to that of RO for treating natural heated groundwater. In terms of treatment performance, SGMD is established to be more advantageous to RO due to its ability to attain high quality fresh water (high salt and fluoride ion rejection rate).

Electrochemical CO2 separation by a shorted membrane

Owing to the alkaline environment, anion-exchange membrane fuel cells allow employing cost-efficient components, but also suffer from the electrolyte carbonation induced by the CO₂ in the air feed. Recently in <i>Nature Energy</i>, Shi et al. introduced an anion- and electron-conductive membrane for efficient electrochemical CO₂ removal, providing a potential solution.

Preparation, Properties and Water Dissolution Behavior of Polyethylene Oxide Mats Prepared by Solution Blow Spinning.

The relationship between processing conditions, structure and morphology are key issues to understanding the final properties of materials. For instance, in the case of polymers to be used as scaffolds in tissue engineering, wound dressings and membranes, morphology tuning is essential to control mechanical and wettability behaviors. In this work, the relationship between the processing conditions of the solution blow spinning process (SBS) used to prepare nonwoven mats of polyethylene oxide (PEO), and the structure and morphology of the resulting materials are studied systematically, to account for the thermal and mechanical behaviors and dissolution in water. After finding the optimal SBS processing conditions (air pressure, feed rate, working distance and polymer concentration), the effect of the solvent composition has been considered. The structure and morphology of the blow spun fibers are studied as well as their thermal, mechanical behaviors and dissolution in water. We demonstrate that the morphology of the fibers (size and porosity) changes with the solvent composition, which is reflected in different thermal and mechanical responses and in the dissolution rates of the materials in water.

Investigate the multi-physics performance of a new fuel cell stack by a 3D large-scale model basing on realistic structures

There are great interactions between the multi-physics fields distributing characteristics and the key structure factors within the solid oxide fuel cell (SOFC) stack. Understanding these secrets are important for the development of stack technologies referring to performance and duration. In this paper, the 3D large scale multi-physics model basing on the realistic solid, space and porous structures of a special designed 24-cells stack is successful developed with 15,656,579 specially designed meshes. The research result show that: i) adopting the 3-paralleled serpentine rib channels and discrete cylindrical rib channels for the anodic and cathodic surfaces, respectively, can well ensure relevant high fuel pressure and reactants distributing uniformities over the electrolyte surfaces; ii) the even and odd numbered interconnect plates are designed to have same structures and placed in different directions, which contribute to one fuel flow path and two separated 2in3out air flow paths. Each air flow path will in charge of the air feeding for half of the stack; iii) the trapezoidal distributor will feed the sub-inlet manifolds of each air flow path with similar mass flow rates. The corresponding fuel and air flows, hydrogen and oxygen, and temperature uniformities on both stack and single cell levels are calculated and analyzed.

Design and Assessment of a Small-Scale Machine for Cleaning Wheat Grains

Abstract A small-scale wheat cleaning machine was designed to winnow and separate grains from materials-other-than-grains (MOG), such as premature grains and chaff, in order to enhance the quality of grains. It was evaluated technically with respect to assessment criteria: cleanliness, grain loss, chaff rejection, and cleaning efficiency. Experiments were carried out at three levels of sieve slopes (5, 10, and 15°), two sieve reciprocating speeds (0.48 and 0.95 m·s−1), two levels of feed rates (1 and 1.5 kg·min−1), and three air velocities (5, 6 and 7 m·s−1). The results showed that, at sieve reciprocating speed of 0.95 m·s−1, the maximum cleanliness value was – 96.25% – observed at 1.5 kg·min−1 feed rate, 5 m·s−1 air velocity and 5° sieve slope. The minimum cleanliness value – 76.82% – was observed at a feed rate of 1 kg·min−1, 15° sieve slope, 7 m·s−1 air velocity, and 0.48 m·s−1 sieve reciprocating speed. The results showed that the use of either a very low, or a very high sieve slope angle and sieve reciprocating speed while using different air velocities and feed rates is not recommended.

Design a novel air to water pressure amplifier powered by PV system for reverse osmosis desalination

This work aims to design a novel standalone small-size air-to-water pressure amplifier (ATWPA) for RO desalination system with low energy consumption. A small DC PV system, pneumatic system, and solar water heater were designed and used to operate the ATWPA at different air pressure (1–5 bar) and heating water (30–45 °C), hence avoiding using a high-pressure and high-energy water pump. The ATWPA has a smart electronic circuit with a feedback system and controls the IR to synchronize the piston movement with pressure and water discharge. The feed air pressure was maximized from 5 bar to 27.9 bar, i.e. the pressure has amplified by 458% where it creates enough pressure to overcome the membrane resistance. The power consumption of ATWPA varied from 0.0 to 3.5 W in compression and suction strokes, respectively and maximum energy consumption was 105 Wh. Increasing feed water temperature and operating air pressure led to increasing freshwater productivity. The preheating of saline water to 45 °C and increasing pressure to 5 bar increased freshwater productivity to 58.8 L/h and decreased energy consumption.

Wire-free electrochemical CO2 scrubbing

Anion-exchange membrane fuel cells offer the prospect of low-cost components thanks to their alkaline environment, yet they are plagued by carbonation of the electrolyte caused by the CO2 present in the feed air. Now, an electrochemical method for CO2 scrubbing using a membrane with mixed ionic–electronic conductivity offers a potential remedy.

Design of PSO-tuned FOPI & Smith predictor controller for nonlinear polymer electrolyte membrane fuel cell

ABSTRACT The polymer electrolyte membrane (PEM) fuel cell or proton exchange membrane fuel cell (PEMFC) has sparked a lot of interest in renewable electricity generation due to high efficiency, quick start up time, and low operating temperature. However, they exhibit highly nonlinear behavior with degraded power quality under uncertain input conditions. The hydrogen, oxygen, and air feed determine the PEMFC system’s performance. Controlling the manifold pressure at the cathode side is essential in preventing the problem of oxygen starvation. In this paper, a nonlinear dynamic model of the PEMFC is considered to control the supply manifold pressure. The performance of the nonlinear PEMFC with various classical controllers (PI, PD, PID, and PID with filter derivative), Smithpredictor, and Fractional Order PI (FOPI) controllers are compared. The optimization of classical controllers is performed by PID tuner. On the other hand, Smith predictor and FOPI controller are tuned by artificial intelligence technique, namely, Particle Swarm Optimization (PSO). The FOPI controller is also tuned with Genetic Algorithm (GA). The PEMFC output is compared in terms of performance evaluation parameters, i.e. settling time, overshoot, and steady state error. The computer simulations suggest that in comparison with GA-FOPI [settling time (ts) = 1.374 s, overshoot (Mp) = 18.452%, steady state error (ess) = 0.1%] and PSO-Smith predictor (ts = 1.262 s, Mp = 5.581%, ess = 0%), the PSO-FOPI controller results in much better settling time (ts = 1.008 s), overshoot (Mp = 2.577%), and steady state error (ess = 0%). Thus, PSO-optimized FOPI controller with nonlinear PEMFC outperforms the classical, PSO-Smith predictor, and GA-FOPI control schemes.

Spray dried extract of Callophyllum brasiliense Cambés produces a potent hypoglycemic effect and improves total serum cholesterol and triglycerides in diabetic rats

The species Calophyllum brasiliense Cambés (Calophyllaceae) is widespread throughout Central and South America. The stem bark infusion is used for lowering blood glucose. Aim: To optimize the spray dry extract of this plant using a D-optimal experimental design. Materials and methods: As factors were used the air-drying speed (3.5-4.5 m3/h), the feed flow rate of the suspension (5-11 mL/min), and the inlet air temperature (90-130 °C). The dried extract was character-ized by measuring the phenolics and flavonoids content, moisture, the water activity, apparent densities, flowability, and compressibility. The antioxidant activity, the inhibitory activity of lipase and alpha-glycosidase, and the antiglycant activity of the spray dried extract (SDE) were evaluated. Subsequently, the hypoglycemic activity was evaluated in rats by monitoring the blood glucose level, triglycerides, and choles-terol. Results: Inlet air temperature and feed flow rate were the factors that most affected the yield and phenolic content. SDE showed a potent antioxidant effect (IC50 1.83 μg/mL), a potent α-glycosidase (IC50 74.45 μg/mL) and pancreatic lipase (IC50 27.33 μg/mL) inhibition. A potent antiglycation effect (IC50 9.45μg/mL) was also observed. Conclusion: the SDE showed a potent hypoglycemic effect at 100 mg/kg. These results suggest that SDE could activate four important pathways that can contribute to diabetes control.

A shorted membrane electrochemical cell powered by hydrogen to remove CO2 from the air feed of hydroxide exchange membrane fuel cells

A shorted membrane electrochemical cell powered by hydrogen to remove CO2 from the air feed of hydroxide exchange membrane fuel cells

Three-dimensional modelling and optimization of an industrial dual fluidized bed biomass gasification decoupling combustion reactor

Dual fluidized bed biomass gasification decoupling combustion technology, as a promising technology to realizing the highly efficient and stable combustion for high-water-containing biomass fuel and lower NOx emission, has drawn worldwide attention from researchers in recent years. In this work, a three-dimensional industrial dual fluidized bed biomass gasification decoupling combustion reactor was modelled using the reactive multiphase particle-in-cell approach, and the secondary air operating parameters concerning total secondary air ratio, upper secondary air ratio, upper secondary air height, and upper secondary air injection models of the biomass gasification combustion reactor were optimized to enhance its performance further. Results show that the biomass gasification combustion model, established and comprehensively verified by comparing the simulated values with measured data in this work, shows a good prediction accuracy of gas–solid flow, heat transfer, and biomass combustion processes. With the total secondary air ratio, the upper secondary air ratio and the upper secondary air height increase, the gas-phase entrainment effects on the axial particle concentration distribution below the upper secondary air feed port in the dense zone weakens, and the overall biomass combustion efficiency decreases. Compared with the single injection model for the upper secondary air injection, the gas-phase entrainment effects on the axial particle concentration distribution were enhanced, and the overall biomass combustion efficiency was improved when adopting the opposite injection or circular injection model. Finally, the optimal secondary air operating parameters for the biomass gasification combustion reactor were obtained from the combustion and gasification views, providing an essential theoretical reference for industrial-scale dual fluidized bed biomass gasification decoupling combustion reactor optimization, biomass gasification decoupling combustion process enhancement, and efficient biomass energy utilization.

Investigation of flame acoustic excitation of a gas burner

Combustion in ultrasonic field is a promising combustion technology as it provides high combustion efficiency and low pollutant emission. Imposing acoustic oscillations on flame front enhances the turbulent mixing, resulting in reduced NOx and CO emissions and reduced flame length. The acoustic field can be generated by using two types of devices: the piezoelectric devices and the sonic nozzle. In this paper, the combustion characteristics in ultrasonic field generated by a sonic nozzle attached to a gas burner have been experimentally and numerically studied. The acoustic intensity can be adjusted by modifying the pressure of feeding air or the nozzle size. The numerical model was validated against experimental data on CO concentration and temperature and was used to study the burner performance for different operation conditions (different air pressures and different nozzle sizes). For a given air pressure and nozzle size, the NOx emissions drop from 200 mg/Nm3 to 150 mg/Nm3, the CO emissions decrease from 125 mg/Nm3 to 100 mg/Nm3 and combustion efficiency increases from 94% to about 96%. The temperature field, with slightly lower temperatures, has more uniform distribution in the flame.

Sustainable production of oxalic acid from waste cane sugar molasses via systemic recycling of nitrogen oxide

An effective and environmentally benign method of producing oxalic acid from nitric acid oxidation of waste cane sugar was conducted via a sequence of reactors. Nitrogen oxides (NOx) formed within the first batch of reactor were reused in the subsequent reactor to prevent the wastage of oxidizer. In addition, the excess nitrogen oxides from the second reactor were channeled into a last reactor comprising of ammonia (NH3) solution to consume the remaining NOx gas into ammonium nitrate (NH4NOx), to be used as fertilizer. Inclusion of vanadium pentoxide (V2O5) as the catalyst improved the yield from 34.8% to 55.6% in the first reactor. This value was further improved to 57.8% upon incorporation of titanium dioxide (TiO2) as catalyst promoter with V2O5 at 2:10 M ratio. In addition, various reaction parameters such as air flow rate, time, temperature, feed concentration and solvent to feed ratio were optimized to produce a maximum yield of 60.2%. To investigate the possibility of maximum number of reactors that can be catered by the initial nitrogen oxide composition, the batch of reactors were extended up to four. Maximum yield of 60.2% was obtained for the first stage, and 55.3%, 39.5%, 18.7% were obtained for the 2nd, 3rd, and 4th stages respectively. Kinetic analysis was performed to determine the reaction order and activation energy.

The Effectiveness of Neem Cake (Azadirachta indica) Water Extract against Aphids (Aphis gossypii) on Red Chili Plant

Aphis gossypii is one of the factors that reduce chili production which acts as a pest and virus vector. This research aimed to determine the effectiveness of the application of neem cake water extract to A. gossypii on red chili plants. This research consisted of 2 experimental stages, namely in the laboratory and the greenhouse trials. The experimental design in the laboratory used a completely randomized design of neem cake water extract with treatments is A (Control), B (0.3%), C (0.6%), D (1.2%), E (2.4%), F (4.8%). Each treatment replicate 4 times. Aplication of water neem cake extract by dipping method of chilli leaf. After the leaf feed air dried, then the leaf put into plastic box and invested with 10 nymph of A. gossypii. While the experiments in the greenhouse used a randomized block design of neem cake water extract treatments were A (Control), B (LC50), C (1.5xLC50), D (2xLC50), E (2.5xLC50), F (3xLC50). The concentration of neem extract in the greenhouse experiment based on result of experiment at laboratory. Adults of A. gossypii as much as 20 were invested on every red chili plant. Application of neem cake water extract on red chili plants once every 4 days. The results showed that neem cake water extract effective to A. Gossypii with 0.14% as LC50. Neem cake water extract at concentration of 1.5xLC50 (0.21%) was effective suppressing A. gossypii population on red chili plants.

Performance characteristics of a divergent vortex tube

In this paper performance characteristics for a Ranque-Hilsch vortex tube are presented. The vortex tube was of divergent design and optimised for both size and performance, to be used to supply cold air to turbomachinery experiments with feed air in the supply pressure range 3.0–7.0 bar, and with overall feed mass flow rates in the range 0.05–0.14 kg/s. Optimum fixed parameters selected from the literature were: the ratio of cold-exit diameter to tube inlet internal diameter (0.50); the ratio of combined inlet-nozzle throat area to the tube inlet internal cross-sectional area (0.22); the vortex tube half-angle (3°); the number of inlet nozzles (6); the half-angle of the hot exhaust conical splitter (45°) and the ratio of tube length to tube inlet internal diameter (20). Free parameters that were investigated were: the overall total-to-static pressure ratio between inlet and cold-exit conditions (3.0, 5.0, and 7.0) and the cold-gas mass fraction (0.0–1.0). Comprehensive experiments were performed to characterise the vortex tube performance in terms of the following parameters: non-dimensional cold and hot-outlet temperatures; non-dimensional cold and hot-gas energy separation; isentropic efficiency referenced to cold-gas expansion; and coefficient of performance (COP). A transient heat flux correction technique was implemented to correct for unsteady heat flux terms from the working gas to the vortex chamber walls. Joule-Thomson effects were accounted for by introducing a corrected inlet total temperature. Cold-exit and hot-exit temperature separations were found to increase with pressure ratio. Non-dimensional cold-exit temperature had a minimum at cold-gas mass fraction of approximately 0.40. Non-dimensional hot-exit temperature increased approximately linearly with cold-gas mass fraction. COP decreased with increasing pressure ratio and had a peak value at cold-gas mass fraction approximately 0.60. Isentropic efficiency was relatively insensitive to pressure ratio and had a peak value at cold-gas mass fraction approximately 0.23. In the range investigated the lowest non-dimensional cold-exit temperature (normalised by inlet temperature) was 0.91, the highest coefficient of performance was 0.097, and the highest isentropic efficiency was 0.23. Full details of the design are given, allowing implementation by other researchers.

Observer-based interval type-2 fuzzy PID controller for PEMFC air feeding system using novel hybrid neural network algorithm-differential evolution optimizer

In this paper, a novel hybrid Neural Network Algorithm-Differential Evolution (NNA-DE) optimizer which integrates both NNA and DE is proposed. The proposed hybrid NNA-DE optimizer demonstrates better performance compared to the standard NNA and the other state-of-the-art optimization algorithms. The proposed hybrid NNA-DE algorithm is then employed for optimizing an observer-based interval type-2 fuzzy PID (OB-IT2FPID) controller applied to the proton exchange membrane fuel cell (PEMFC) air feeding system. The whole design parameters of the OB-IT2FPID controller including the scaling factors, interval type-2 membership function parameters and the footprint-of-uncertainty (FOU) are optimized using the proposed hybrid NNA-DE algorithm. The results show that the proposed NNA-DE optimized OB-IT2FPID controller achieves better performance in terms of set-point tracking, disturbance rejection and the time-domain performance indices. The robustness of the proposed NNA-DE optimized OB-IT2FPID controller against parametric uncertainty in the PEMFC air-feeding system is tested. The proposed controller demonstrated better robustness against parameter uncertainty in the system. Processor-in-the-Loop (PIL) approach is adopted to validate the performance of the proposed controller on embedded control hardware.