Regulation Of Airflow Research Articles

Prediction and optimization of air velocity and gas concentration under control of air flow at outlet of fully mechanized heading

Aiming at the problem that the traditional ventilation method can not control the wind speed and reduce the gas concentration, and cause the wind speed and gas concentration to exceed the limit, the new method of dynamic regulation of wind turbine outlet air flow to optimize the wind speed and gas concentration is studied. According to the actual problems, the influences of the air outlet parameters on wind speed and gas are simulated. The correlation mechanism between the air outlet and the wind speed and gas concentration and the regression prediction model are established. In the NingTiao Mine of Shaanxi Coal Group, the underground installation test and verification were carried out by using the self-developed control device, and the optimal wind field control plan for the Ningtiao Mine was determined. The results showed that the wind speed was too large or too small, and the parameters such as the diameter of the air outlet were adopted. The adjustment can control the wind speed to reach the 0.25m/s to 4m/s range required by the regulations, and the gas concentration is significantly reduced.

Low temperature co-fired ceramics technology for active eddy current turbocharger speed sensors

PurposeThe purpose of this paper is to analyze a presentation of eddy current sensing coils for the turbo charger speed measurement, which were manufactured with the low temperature co-fired ceramic (LTCC) technology. The goal is to be able to manufacture small robust coils with complex geometries and improved signal output.Design/methodology/approachA crucial element for its performance is the quality factor of the embedded coil. Thanks to the use of the developed LTCC manufacturing processes, the lateral wounding distance of the printed coils can be reduced to 30 µm, and simultaneously, the aspect ratio should be enlarged compared to standard LTCC technologies. By the use of a novel printed double-D coil design, the overall sensor characteristics will be improved.FindingsThe metallization thickness can be simultaneously enhanced that results in the internal resistance being reduced. Thus, the inductivity and the ohmic resistance achieve an obvious optimization that results in significant improvement of the quality factor of the novel coils when compared to standard technologies. Embedded micro coils have a sintered metallization aspect ratio of more than one and thus an optimal performance differing clearly from prior art. Their reliability was proven through temperature cycle tests of over more than 1,300 h.Research limitations/implicationsThe developed LTCC coil technology will be introduced in the JAQUET sensor portfolio of TE Connectivity for the measurement of turbocharger speed on both passenger cars and trucks. The measurement and control of turbochargers speed enables the optimal regulation of airflow into the engine thereby improving the fuel economy and leading to a reduction of engine emissions.Originality/valueThis paper shows fabrication and performance of the original manufactured LTCC coil for turbocharger speed sensors and its optimized signal output by the novel design.

Application of VENTSIM 3D and mathematical programming to optimize underground mine ventilation network: A case study

Ventilation is a vital component of an underground mining operation, used to guarantee a safe atmosphere for workers and survive them from the hazardous and toxic gases. In the recent years, engineers have begun to apply new operation research techniques in order to optimize the ventilation systems to assist in achieving a regulatory compliance, reduce ventilation costs, and improve its efficiency. Airflow regulation optimization in mine ventilation networks is described as a minimization model whose objective function is a minimum number of regulators and energy consumption. In this work, all the previously accomplished works were first reviewed. Then a ventilation system was designed for the Western-Razmja coal mine by a manual method, and an axial fan was proposed. Subsequently, the same ventilation system was simulated using the VENTSIM 3D software. The results obtained by computer simulation showed that there was a reliable relation between the manual method and the simulation approach. In the final step, the GAMS software was used to solve a Mathematical Programming (MP) problem to minimize the overall cost of ventilation by determination of the optimum location for the fan and regulators. The final results of this work illustrated that not only the number of regulators were reduced through solving the MP model but also the total resistance of the Western-Razmja coal mine was reduced by 14% from 1.6 to 1.3. Furthermore, it was observed that the total efficiency of the proposed fan was increased.

Control of PEM Fuel Cell Systems Using Interval Type‐2 Fuzzy PID Approach

AbstractIn this study, an interval type‐2 fuzzy proportional–integral–derivative (IT2FPID) controller is designed to be used in the air flow regulation of polymer electrolyte membrane fuel cell (PEMFC) systems. The proposed controller is able to handle the effect of external disturbances and fix the oxygen excess ratio at an appropriate set‐point. Three crisp singletons for the output and two interval type‐2 membership functions for the inputs are defined for the suggested controller. Two conventional controllers including type‐1 fuzzy PID (T1FPID) and ordinary proportional–integral–derivative (PID) are also investigated to evaluate the performance and efficiency of this technique. The results of various simulations indicate that the IT2FPID controller has a better performance and transient response compared to the other approaches.

Fuel composition effect on cathode airflow control in fuel cell gas turbine hybrid systems

Cathode airflow regulation is considered an effective means for thermal management in solid oxide fuel cell gas turbine (SOFC-GT) hybrid system. However, performance and controllability are observed to vary significantly with different fuel compositions. Because a complete system characterization with any possible fuel composition is not feasible, the need arises for robust controllers. The sufficiency of robust control is dictated by the effective change of operating state given the new composition used. It is possible that controller response could become unstable without a change in the gains from one state to the other.In this paper, cathode airflow transients are analyzed in a SOFC-GT system using syngas as fuel composition, comparing with previous work which used humidified hydrogen. Transfer functions are developed to map the relationship between the airflow bypass and several key variables. The impact of fuel composition on system control is quantified by evaluating the difference between gains and poles in transfer functions. Significant variations in the gains and the poles, more than 20% in most cases, are found in turbine rotational speed and cathode airflow. The results of this work provide a guideline for the development of future control strategies to face fuel composition changes.

Assessment of air passive sampling uptakes for volatile organic compounds using VERAM devices

A calibration chamber has been designed and employed for the simple and easy determination of uptake sampling rate (RS) of volatile organic compounds (VOCs) from air using passive samplers. A flow of clean air was continuously spiked, at a constant VOC concentration, by the microinjection of a standard solution by means of a T-type tube. The developed system allowed the complete evaporation at room temperature of the standard solution in acetone and the air concentration of VOCs was easily controlled by the regulation of the clean air flow, the standard solution concentration and its flow. Active sampling was employed for monitoring the true concentration of the evaluated compounds inside the calibration chamber, using Tenax-filled desorption tubes and a low flow personal air sampling pump. Versatile, easy and rapid atmospheric monitor (VERAM) devices were employed for the passive sampling of benzene, toluene, ethylbenzene, xylenes, α-pinene, camphene, myrcene, p-cymene, and limonene from air. The RS values obtained for the passive sampling of VOCs, using the developed calibration chamber, were in the range of 1.3–16.0m3day−1 in accordance to previous calibration studies performed for VERAM samplers. The developed calibration chamber provided a continuous flow with a constant concentration of the evaluated compounds that allowed the simultaneous deployment of several samplers for a rapid establishment of RS for a passive sampler type and the easy comparison between different devices.

The extension of the operational range of combined-cycle power plant with a triple-pressure heat recovery steam generator

In the article, the issues of operational flexibility improvement for CCGT with a triple-pressure heat recovery steam generator are described. The factors limiting the operational range of CCGT were identified and analyzed. Analytical dependences for the minimum and maximum load of the CCGT on the ambient air temperature were obtained. The ways of expanding an operational range due to water spray into air-intake path, supplementary firing before the heat recovery steam generator, intensifying regulation of compressor airflow using the IGV and its pre-heating are described.

Retrofit of a wet cooling tower in order to reduce water and fan power consumption using a wet/dry approach

A Parallel Path Wet/Dry configuration and a high-precision airflow regulation method are implemented in order to retrofit an existing wet cooling tower. The modifications are intended to reduce water requirements and fan power consumption of a 12-cell wet tower. The proposed method of airflow control takes advantage of fans with variable frequency drive to regulate airflow with high accuracy. A number of simulations are carried out to predict different operating factors of the wet and hybrid towers. Experimentally obtained values of water consumption demonstrate the validity of those obtained using the computer simulations. According to the results, the accurate airflow control prevents sudden fluctuations in requisite fan power and water consumption rate and causes up to 64.6% decrease in fan power consumption. The results reveal that using the proposed wet/dry approach results in an average 9.4% decrease in water consumption. Given the relatively low degree of modifications made to the original wet tower and preserving the condenser operating condition, the accomplished amount of water conservation is satisfactory.

Is sexual dimorphism in singing behavior related to syringeal muscle composition?

The avian vocal organ, the syrinx, is located at the base of the trachea and is controlled by 4 intrinsic pairs of muscles, ventral and dorsal tracheobronchial and ventral and dorsal syringeal muscles. These muscles facilitate active regulation of airflow and sound features, and show exceptionally fast contraction kinetics, stemming from superfast and fast oxidative fiber type composition. Here we investigated to what degree fiber type composition varies across songbird species and whether or not singing ability is related to fiber type composition. In all 10 species studied, syringeal muscles are composed of fast and superfast muscle fibers in males and females. Syrinx size and muscle fiber diameter show some dependence on body size. Content of superfast fibers in the syrinx does not appear to be correlated with singing ability, because non-singing females do not consistently show lower superfast fiber content. Instead, the percentage of superfast fibers in syringeal muscles may be connected to the involvement of neuromuscular control in the generation of the acoustic structure and the entire vocal repertoire of a species.

A Theoretical Framework for the Evaluation from the Traditional Mashrabiya to Modern Mashrabiya

Finding a favorable trade-off between saving the architectural heritage, and assuring the development of modern architecture is a delicate and precise task, due to the lack of knowledge in the original criteria for the re-thinking of traditional architecture. As a tentative answer to this challenge, this paper attempts to shed light on Mashrabiya (traditional Arab oriel window) as a powerful environmental element in modern architecture, with regard to the important functions that it provides, such as light control, airflow regulation, humidity control, temperature regulation and visual privacy. Due to these functions, Mashrabiya achieved widespread popularity around the old world and it has been revived again in many contemporary projects by different modern versions. The objective of this study also is presenting a general evaluation for the modern Mashrabiya to observe the misconceptions of using the Mashrabiya and to call for stop ignoring of the proper standards of Mashrabiya design and to preserve the original name of this element Mashrabiya.

A Disposable Multi-Functional Air Filter: Paper Towel/Protein Nanofibers with Gradient Porous Structures for Capturing Pollutants of Broad Species and Sizes

Highly polluted air is usually concentrated with particles of broad sizes and species of gaseous toxic chemicals. Filtration of these pollutants simply relying on size effects is not sufficient; instead, strong interactions between filtering materials and pollutants are in critical need. Moreover, to reduce or even avoid further pollution to the environment from disposing of the massive amount of used air filters demands the development of “green” air filtering materials. Here, we report a high-performance hybrid cellulose/protein air filter with nanofiber structures. Interestingly, it was discovered that textured cellulose paper towel can not only act as a flexible mechanical support but also as a type of air flow regulator that can improve pollutant–nanofilter interactions. Therefore, the high-performance natural protein-based nanofabrics are promoted both mechanically and functionally by textured cellulose paper towel. Study results indicate that this hybrid filtering material possesses excellent remov...

Feedforward fuzzy-PID control for air flow regulation of PEM fuel cell system

Oxygen excess ratio is one of the most crucial parameters for proton exchange membrane (PEM) fuel cell system protection and performance improvement. In this study, a new fuzzy-PID controller based on feedforward approach is proposed to regulate oxygen excess ratio. To implement a feedforward fuzzy-PID (FFPID) control, a control-oriented dynamic model of PEM fuel cell is developed in MATLAB/Simulink platform including cathode and anode mass flow transients and membrane hydration dynamics model. Moreover, PEM fuel cell balance-of-plant (BOP), comprised of air compressor, humidifier, cooler, and purge valve, is also integrated into the system modeling. In order to optimize PEM fuel cell operation, such as preventing oxygen starvation and/or optimizing output power by trade-off compressor parasitic power, a FFPID controller is developed to adapt PID parameters to regulate air flow rate using on-line fuzzy logic optimization loop. A FFPID controller utilizes the reference feedforward input and the errors. Conventional PID and conventional fuzzy-PID (CFPID) are compared to validate the performance of the FFPID control method. Simulation results reveal that the efficacy of the proposed feedforward fuzzy-PID approach is proved in regulating the oxygen excess ratio and in reducing parasitic power loss.

Performance of oxidation-reduction potential-based hydrolysis and acidification process for high-strength antibiotic wastewater treatment

This study used hydrolysis and acidification process under appropriate oxidation-reduction potential (ORP) condition to treat high-strength antibiotic wastewater. ORP was controlled at approximately −100 mV through air-flow regulation. Results showed that the appropriate ORP condition enhanced the physiological metabolic function of facultative hydrolytic and acidogenic bacteria, and aerated stirring improved the hydraulic condition. Acidification degree (AD) and effluent volatile fatty acid (VFA) reached 58.64% and 4,825 mg/L, respectively, at the shortest hydraulic retention time of 10 h and the maximum organic loading rate (OLR) of 20 kg COD/(m3 d). Wastewater biodegradability was improved by approximately 17%, thus providing good substrate for post-aerobic treatment. Relatively stable effluent was achieved with the fluctuant influent, and COD and SS removal efficiencies were 15–30% and 90–95%, respectively. The change in VFA lagged behind the AD in the effluent, indicating that AD could better represent the effects of hydrolysis and acidification process. The height of the reactor for stable VFA production increased as the OLR increased.

Regulation of glottal closure and airflow in a three-dimensional phonation model: implications for vocal intensity control.

Maintaining a small glottal opening across a large range of voice conditions is critical to normal voice production. This study investigated the effectiveness of vocal fold approximation and stiffening in regulating glottal opening and airflow during phonation, using a three-dimensional numerical model of phonation. The results showed that with increasing subglottal pressure the vocal folds were gradually pushed open, leading to increased mean glottal opening and flow rate. A small glottal opening and a mean glottal flow rate typical of human phonation can be maintained against increasing subglottal pressure by proportionally increasing the degree of vocal fold approximation for low to medium subglottal pressures and vocal fold stiffening at high subglottal pressures. Although sound intensity was primarily determined by the subglottal pressure, the results suggest that, to maintain small glottal opening as the sound intensity increases, one has to simultaneously tighten vocal fold approximation and/or stiffen the vocal folds, resulting in increased glottal resistance, vocal efficiency, and fundamental frequency.

Should otolaryngologists pay more attention to nasal swell bodies?

Should otolaryngologists pay more attention to nasal swell bodies?

Dilemma of Inferior Turbinate Surgery

Background and objectives: Inferiorturbinate surgery is considered as one of most commonly performed surgery in rhinology. It is usually done to reduce the bulk of inferior turbinates. It can be conducted for different indications such as relieving the mechanical nasal obstruction due to hypertrophied inferior turbinates, or to achieving a sufficient nasal surgical access during endoscopic sinus surgery, or removing the inferior turbinates as a part of wide and complete resection of rhino-sinus neoplastic lesions. The inferior turbinates have important role in the maintenance of nasal breathing function by providing the nasal valve mechanism necessary for the regulation of air flow through the nose. In spite of availability of well-established variable techniques for this surgery, the main goal of this surgery is yet not completely achieved. This could bean effect of different factors that are difficult to be predicted and controlled. Hence this pattern of surgery has become dilemmas in rhinology which need to be deeply evaluated and subsequently resolved. In order to evaluate and resolve this dilemma, this serial study was conducted prospectively. Patients and methods: 1337 patients aged 3 to -65 years suffering from hypertrophied inferior turbinates, presented with clinical pictures of mechanical nasal obstruction at ENT department – of Althowra central hospital and Al-tarahom private center Elbyda city- Libya between September 2005 to September 2014 they were operated by variable techniques of inferior turbinate surgery, namely sub-mucosal diathermy (SMD) (n=864 ), partial inferior turbinectomy (PIT) (n=427), CO2 laser vaporization of inferior turbinate (n=21), and turbinoplasty (n=25) . Post-operative atrophic rhinitis, and persistence, or recurrence of mechanical nasal obstruction the outcomes are that were studied in relation to different factors to shed-light on existing dilemma. Results and Conclusion: Proper selection of patient for this pattern of surgery is considered one of the main aspects of this issue and one of significant steps towards resolving of this dilemma. On the other hand, type of the technique for this surgery is an important selection criterion. In addition the amount of the inferior turbinate needed to be resected must be decided.

Transfer function development for control of cathode airflow transients in fuel cell gas turbine hybrid systems

Direct-fired fuel cell gas turbine hybrid power system responses to open-loop transients were evaluated using a hardware-based simulation of an integrated solid oxide fuel cell gas turbine (SOFC/GT) hybrid system, implemented through the Hybrid Performance (Hyper) facility at the U.S. Department of Energy, National Energy Technology Laboratory (NETL). A disturbance in the cathode inlet air mass flow was performed by manipulating a hot-air bypass valve implemented in the hardware component. Two tests were performed; the fuel cell stack subsystem numerical simulation model was both decoupled and fully coupled with the gas turbine hardware component. The dynamic responses of the entire SOFC/GT hybrid system were studied in this paper. The reduction of cathode airflow resulted in a sharp decrease and partial recovery of the fuel cell thermal effluent in 10 s. In contrast, the turbine rotational speed did not exhibit a similar trend. The transfer functions of several important variables in the fuel cell stack subsystem and gas turbine subsystem were developed to be used in the future control method development. The importance of the cathode airflow regulation was quantified through transfer functions. The management of cathode airflow was also suggested to be a potential strategy to increase the life of fuel cells by reducing the thermal impact of operational transients on the fuel cell subsystem.

Extraorbital lacrimal gland excision: a reproducible model of severe aqueous tear-deficient dry eye disease.

The aim of this study was to establish and characterize extraorbital lacrimal gland excision (LGE) as a model of aqueous tear-deficient dry eye disease in mice. Female C57BL/6 mice at 6 to 8 weeks of age were randomized to extraorbital LGE, sham surgery, or scopolamine groups. Mice that underwent extraorbital LGE or sham surgery were housed in the standard vivarium. Scopolamine-treated mice were housed in a controlled environment chamber that allowed for the continuous regulation of airflow (15 L/min), relative humidity (30%), and temperature (21-23°C). Clinical disease severity was assessed over the course of 14 days using the phenol red thread test and corneal fluorescein staining. Real-time polymerase chain reaction was performed to assess corneal mRNA expression of interleukin 1β, tumor necrosis factor α, and matrix metalloproteinase 9. Flow cytometry was used to assess T helper cell frequencies in the conjunctivae and draining lymph nodes. Extraorbital LGE markedly reduced aqueous tear secretion as compared with the sham procedure and induced a more consistent decrease in aqueous tear secretion than was observed in mice that received scopolamine while housed in the controlled environment chamber. Extraorbital LGE significantly increased corneal fluorescein staining scores as compared with those of both the sham surgery and scopolamine-treated groups. Extraorbital LGE significantly increased the corneal expression of interleukin 1β, tumor necrosis factor α, and matrix metalloproteinase 9. Further, extraorbital LGE increased T helper 17-cell frequencies in the conjunctivae and draining lymph nodes. Extraorbital LGE induces aqueous tear-deficient dry eye disease in mice as evidenced by decreased aqueous tear secretion, increased corneal epitheliopathy, and induced ocular surface inflammation and immunity.

Characterization of Air Profiles Impeded by Plant Canopies for a Variable-Rate Air-Assisted Sprayer

<abstract> <bold><sc>Abstract.</sc></bold> The preferential design for variable-rate orchard and nursery sprayers requires that the sprayers are able to control the liquid and air flow rates based on the canopy structure in real time. Demand for this advanced feature has increased rapidly with the public demand for reductions in pesticide use. A variable-rate, air-assisted, five-port sprayer had been in development to achieve variable discharge rates of both liquid and air. To verify the capability of varying the airflow rate by changing the fan inlet diameter of the sprayer, air jet velocities impeded by plant canopies were measured at various locations inside tree canopies of three different sizes and foliage densities. Air jet velocities were adjusted by changing the sprayer fan inlet diameter with an airflow regulator and measured with a constant-temperature anemometer coupled with hot-wire probes. Peak air velocity and airflow pressure decreased with foliage density and canopy depth. For the 0.34 m fan inlet diameter, the airflow pressure ratio of the front portion to the back portion of the canopies was 2.45 for a 1.65 m tall and 13.4 leaf area index (LAI) Tsuga canadensis (Tree 1), 1.43 for a 2.35 m tall and 2.5 LAI Ficus benjamina (Tree 2), and 1.64 for a 3.0 m tall and 1.5 LAI Acer rubrum (Tree 3). Similarly, the front-to-back peak air velocity ratios were 8.55, 1.59, and 1.89 for Tree 1, Tree 2, and Tree 3, respectively. Variations were significant for peak air velocities and airflow pressures among the three different tree volumes and foliage densities. Increasing the fan inlet diameter from 0.13 to 0.34 m increased average airflow pressure from 2.84 to 4.01 kg m^-2, from 3.88 to 5.82 kg m^-2, and from 2.46 to 3.75 kg m^-2 inside the canopies of Tree 1, Tree 2, and Tree 3, respectively, while it also increased average peak air velocity from 2.6 to 4.5 m s^-1, from 5.5 to 9.1 m s^-1, and from 3.0 to 5.2 m s^-1 inside the three tree canopies. Therefore, the new sprayer design with an airflow regulator to alter the fan inlet diameter was able to provide variable airflow for different canopy sizes and foliage densities and offered a potentially effective approach to discharge uniform airflow profiles to carry droplets with efficient spray penetration into plant canopies.

Mitigation studies of sulfur contaminated electrodes for PEMFC

Abstract The performance of Polymer Electrolyte Membrane Fuel Cell (PEMFC) is highly influenced by the contaminants present in the air, like sulfur compounds, nitrogen compounds, carbon oxides, chlorides etc. In particular, sulfur dioxide (SO2) on the cathode side has a severe effect on the performance of PEMFC. In the present paper we have attempted to mitigate the effect of SO2 poisoned catalyst layer of the fuel cell for both half cell and for single cell using a novel catalyst support. The mitigation strategies for the contaminated MEAs were studied by three different methods viz., electrochemical cycling, increased air stoichiometry and by successive polarization. The platinum on graphene as a catalyst support was found to have a better tolerance towards SO2 contamination when compared with the conventional platinum supported on Vulcan XC carbon catalyst. Electrochemical and single cell contamination tests were done to study the extent of SO2 poisoning on both the catalysts. The sulfur coverage was found to be less for Pt/G based catalyst, around 54% compared with Pt/C. The recovery by successive polarization was found to be better compared to air flow regulation. This may be attributed to the indirect removal of sulfur ions from Pt through scavenged OH− ions.