Filtration Efficiency Research Articles

Optimizing FIR Filter Efficiency with Advanced Hybrid Multiplier Techniques

Optimizing FIR Filter Efficiency with Advanced Hybrid Multiplier Techniques

Filtration efficiency of different protective masks against viral aerosols

Filtration efficiency of different protective masks against viral aerosols

Effect of sampling face velocity on the ultrafine particle surface collection efficiency of a cellulose membrane filter and a cellulose-glass fiber filter for environmental airborne radioactivity monitoring.

Surface collection efficiency (SCE) of a cellulose membrane filter (CMF) and a cellulose-glass fiber filter used in environmental monitoring for alpha-emitting radionuclides from nuclear facilities and natural radioactivity sources was evaluated for particles in the size range of 0.03-0.1μm at different levels of face velocity. The SCE of the CMF was higher than that of the cellulose-glass fiber filter, and only the membrane filter showed the dependence of SCE on the particle size at higher face velocity. The use of the CMF at higher face velocity in environmental radioactivity monitoring leads to measurements of the background alpha spectrum with more degradation under the changing particle size condition in the atmosphere. Consequently, that fact needs to be taken into account, along with the expected particle size distribution and concentration of the airborne radioactivity being sampled, when selecting a face velocity to achieve the best possible detection limit.

Review on need for designing sustainable and biodegradable face masks: Opportunities for nanofibrous cellulosic filters.

The surge in microbial illnesses, notably seen during the COVID-19 pandemic, has led to the global use of face masks-cloth, surgical, medical, and respirator types-to curb respiratory pathogen spread. Widely used by the public, patients, and healthcare workers, masks play a key role in reducing airborne transmission. However, synthetic, non-biodegradable materials in these masks have sparked environmental concerns due to disposal issues. Moreover, challenges like limited microbial filtration, poor fit, breathing resistance, and low reusability raise further issues, as does the failure to neutralize trapped microbes. Addressing these issues calls for high-performance, biodegradable masks crafted from renewable nanofibrous materials using advanced technology. Antimicrobial nanomaterial coatings can further reduce contamination risks for users and the environment. Nanofibrous materials, with their high surface area, enhance filtration, allow customization, and improve capture efficiency. Research is progressing on sustainable, biodegradable filters, particularly with cellulose materials. This review outlines mask types and limitations, spotlighting nanofibrous filters for their filtration efficiency, breathability, and sustainability. It also delves into nanofiber manufacturing and assesses bacterial cellulose-a promising renewable nanofibrous material suited for air filtration.

Numerical Implementation of Electrostatic Solver Within OpenFOAM for Gas Turbine Intake Filtration

Abstract Gas turbines require filtered air to preserve operability, availability, and efficiency. Fouling, corrosion, and erosion severely affect the performance of the axial compressor and it can be in part prevented by filtering the air intake. For this reason, several stages of filters can be used in series to catch pollutant particles gradually smaller and with a high level of capturing efficiency. Traditionally, the separation is obtained using cartridges of porous material, which provide a high level of filtration but at the same time generate a pressure drop increasing over time. Another common type of filter is the inertial one, whose operating principle is based on the inertial force acting on the solid particles to separate them from the mainstream. The capturing efficiency of the inertial filter is not comparable with the porous one and for this reason, it is used upstream as a pre-filter. In recent years, another technique has been developed to filter air flows thanks to an electrostatic field, that is induced inside the flow. The electrostatic force generated is able to attract and separate metallic particles. In the present work, numerical investigations are carried out to simulate the effect of the electrostatic force for gas turbine filtering systems. The computational fluid dynamics tool used is openfoam, whose official release can simulate inertial and porous filtering media, while for electrostatic one is not possible due to the absence of a library able to simulate the electrostatic force that acts on the discrete phase. A new library was developed in order to calculate the electric field, the electric potential, and the charge density of the continuous phase. Simulation results show how the calculation of these quantities allows us to predict the electrostatic force acting on particle flows in the presence of electrostatic fields.

Operator exposure and cabin protection in plant protection product application

AbstractTightly sealed driver's cabs can effectively protect the user from exposure when applying crop protection products. Therefore, under certain conditions, users in such cabins can avoid wearing personal protective equipment for skin and eyes. The protective effect depends on the technical design and handling of the different cabin types and can be divided into categories with different levels of protection. Since the level of protection of the different types of cabins and the associated possibility of not wearing personal protective equipment has not been sufficiently scientifically verified in the past, the present study was carried out to close this gap. Field and laboratory test methods were developed and used to assess exposure levels. External contamination of the cabin was measured using various dosimeters. Exposure inside the cabins was measured on coveralls and gloves to measure dermal exposure and with aerosol sampling pumps to determine inhalation exposure. Tests were conducted on tractors with different cab categories using an air-assisted orchard sprayer as a worst-case scenario for exposure to spray drift. Additionally, an alternative laboratory test method was developed and conducted to evaluate filter efficiency under controlled conditions and compare it with the field tests. The results showed that exposure inside closed cabins was generally low and was not notably correlated with the cabin category. All types of cabins tested were found to provide significant protection from dermal and inhalation exposure.

Effects of carrier structure parameters on diesel particulate filter capture performance based on grey relational analysis

To reduce the pressure drop of diesel particulate filter (DPF) as well as improve its collection efficiency. A mathematical model of DPF pressure drop and capture efficiency was established. This research systematically investigates the effects of channels per square inch (CPSI), wall thickness, and carrier ratio on DPF performance through grey relational analysis (GRA) and polynomial approximation algorithm (PAA). The findings reveal that DPF exhibits lower pressure drop and higher collection efficiency in the case where the carrier ratio, wall thickness, and CPSI are within the ranges of 1.40 to 1.53, 9.8 to 10.5 mil, and 200 to 300, respectively. Particularly, at a carrier ratio of 1.52 and a wall thickness of 10.38 mil, the pressure drop reaches a minimum value of 4.23 kPa, with a collection efficiency of 90.28%. Meanwhile, at a carrier ratio of 1.52 and a CPSI of 200, the pressure drop reaches a minimum value of 4.17 kPa, with a collection efficiency of 90.21%. The model expressions for pressure drop and collection efficiency derived from the PAA are: y 1 = 51.19 + 3.815 x 1 − 8.726 x 2 + 3.794 x 1 2 − 1.735 x 1 x 2 + 0.524 x 2 2 , and y 2 = 0.383 + 0.105 x 1 + 0.085 x 2 + 0.032 x 1 2 − 0.016 x 1 x 2 − 0.0032 x 2 2 . The foregoing models exhibit excellent predictive accuracy and goodness of fit for the DPF performance. Under the interactive influence of carrier ratio and wall thickness, the root mean square errors (RMSE) for pressure drop and collection efficiency are 0.0110 and 0.0002, respectively, with corresponding goodness of fit values of 0.9996 and 0.9985. As revealed by the GRA results, wall thickness exerts the most significant impact on DPF performance, presenting a GRG of 0.84 for filtration efficiency and 0.79 for pressure drop. The overall influence on both collection efficiency and pressure drop follows the descending order: wall thickness > carrier ratio > CPSI. This work has important engineering significance for optimizing the DPF capture performance and extending its working time.

The efficacy and safety of aerosol therapy in rhinology

Abstract Aerosol drug administration has a long history as an important part of the treatment for different respiratory disorders in both adult and paediatric patients. The nebulization process permits the drug delivery directly to the upper and lower airways tracts, allowing increased local effectiveness, and avoids systemic side effects. The aerosol therapy is mainly used in pneumology for lower respiratory tract disorders, a series of drugs having a proven efficacy. Few publications present the efficacy and safety of ENT nebulization, despite its worldwide utilization. Topical drug delivery to the nasal cavities and paranasal sinuses via aerosols appears to be an interesting, but also a challenging alternative. The transport and deposition of drugs and aerosol particles into the sinuses is debatable due to several factors: sinuses are poorly perfused and virtually non-ventilated cavities; they are protected by the efficient particle filtration function of the nasal cavities. The review evaluates the efficacy and safety of aerosol therapy in rhinologic pathology.

Short cellulose acetate nanofibers: A novel and scalable coating for enhancing nanoparticles filtration efficiency of filter media

This study introduces a novel and scalable approach to significantly enhance the filtration efficiency of automotive cabin air filters using short cellulose acetate nanofibers applied via a spray coating method. The short nanofibers, produced through the mechanical fragmentation of electrospun mats, enable uniform dispersion and application onto microfibrous filter media, addressing a key limitation in nanofiber technology. This innovative process enhances the capture of ultrafine particles (7.4 to 250 nm), which are critical for improving air quality in confined environments such as vehicle cabins. The filters, coated with nanofiber weights ranging from 1 to 13 mg, showed a prominent improvement in filtration efficiency, achieving quality factors (Qf) from 0.01 to 0.0221 Pa−1, outperforming both uncoated filters (0.0025 Pa−1) and commercial HEPA filters (0.0212 Pa−1). Filtration efficiency increased from 18 % to 99.8 %, with corresponding pressure drops between 44.5 and 620 Pa. Remarkably, a filter with 9 mg of nanofibers achieved a superior quality factor of 0.0221 Pa−1, effectively optimizing both efficiency and pressure drop while outperforming HEPA filters. This method addresses the common challenge in conventional filters of balancing filtration efficiency with pressure drop. The scalable spray coating process, combined with the advantages of electrospinning, offers a practical, industrially viable solution to improve air filtration in automotive HVAC systems and other environments requiring high filtration efficiency and low-pressure drop.

A Review of the Challenges of Adaptive Filtering Technology in High-fidelity Audio Signal Processing

Abstract. High-fidelity audio signal processing plays an important role in modern audio technology. With the increasing demand for this technology in various audio application scenarios, the optimization of adaptive filters has emerged as a significant challenge in this field. This paper focuses on improving the performance of adaptive filters in high-fidelity audio signal processing which aims to improve the adaptability and efficiency of filters in complex audio environments by improving algorithms. In this study, the adaptive filtering algorithm based on wavelet transform and particle swarm optimization is used to verify the audio data processing by simulation and real data processing. The research data was collected using the standard audio signal database and the actual collected high-fidelity audio samples. The results show that the improved adaptive filter can significantly improve the performance of complex audio environments, improve the clarity and fidelity of audio signals and reduce the computational complexity. It is also suitable for real-time processing scenarios with limited resources. The conclusion shows that this method provides an efficient solution for high-fidelity audio signal processing and has a wide application prospect.

Beyond inhalation protection: Assessing cloth mask effectiveness as source control devices

This study investigates the effectiveness of cloth masks as source control devices during violent respiratory events such as coughing and sneezing. Utilizing a novel experimental platform integrating a mechanical cough simulator and high-speed laser visualization, we quantitatively assess the filtration efficiency of various cloth mask materials. Our results reveal significant variability in the cumulative escaped droplet volume across different fabrics, challenging the assumption that fabrics with similar porosity yield comparable performance. We introduce the concept of active porosity, highlighting its critical role in mask performance for source control, and demonstrate that masks with lower active porosity more effectively mitigate droplet transmission. Furthermore, our findings suggest that a mask's performance in inhalation protection does not directly correlate with its efficacy in source control, emphasizing the need for tailored testing standards. The study also explores the impact of water content on mask performance, revealing that moisture accumulation can significantly alter the filtration efficiency and pressure dynamics of the mask, potentially compromising its protective seal. These insights provide a foundation for improving cloth mask design and standards to better address the challenges of airborne transmission during pandemics.

Multi-objective optimization of laser perforated fuel filter parameters based on artificial neural network and genetic algorithm

In precise fuel circuit systems, the filtration of particulate impurities seriously affects the efficiency and service life of various components. For filtration process intensification of high-pressure fuel laser perforated filters, the two-phase flow characteristics in filters is studied. The size, position and number of filtration holes are taken as optimization variables, and take the filtration efficiency and flow pressure drop as optimization objectives. Computational fluid dynamics (CFD) is used to simulate the two-phase motion of continuous phase and discrete particles in a periodic unit. Artificial neural networks (ANN) are utilized for objectives prediction, and the NSGA-II genetic algorithm is employed for multi-objective optimization, resulting in the Pareto front solution set. Furtherly, the reasonable solution is selected by introducing TOPSIS to ensure that two optimization indexes are relatively smaller and balanced. The optimized filter element scheme allows the filter to have a pressure drop of less than 3.2 MPa under high pressure and a filtration efficiency of over 80% for spherical particle impurities with a diameter of 5 microns or more.

Improving separation efficiency of various micropollutants from water by polymer-enhanced ultrafiltration using oxidized alginate featuring less viscous and low filtration resistance

Polymer-enhanced ultrafiltration (PEUF) is an economical and energy-efficient alternative using a versatile water-soluble polymer (WSP) to remove micropollutants by electrostatic interactions, allowing size exclusion through ultrafiltration (UF) membranes due to the WSP being bigger than the pores of UF membranes. However, the WSP used in PEUF is so viscous that it inevitably causes significant filtration resistance and membrane fouling, reducing filtration and energy efficiency. To overcome this problem, in this study, sodium alginate (Alg), which significantly performs in removing cationic pollutants, was oxidized using sodium periodate to produce oxidized alginate (OxAlg). The retention and water flux profiles of OxAlg for three micropollutants, methylene blue (MB), ciprofloxacin, and tetramethylammonium hydroxide, using the PEUF method were investigated in terms of pH, ionic strength, polymer and pollutant amount. A comparison between Alg and OxAlg demonstrated 1.19% to 1.8% higher MB retention rates (99.31%-99.97%) and up to 4.07 times higher water flux depending on the amount of polymer added. Furthermore, OxAlg displayed excellent retention rates of the NF level and 20-60 times higher water flux than typical NF. This outstanding OxAlg performance was mainly due to OxAlg’s properties, such as the low viscosity, flexibility and the resulting accessibility, and appropriate size from the perspective of filtration. Lastly, OxAlg was found to have the potential to surpass the existing WSP in that it showed a higher maximum retention capacity than about 560 to 1250mg/g in the real-world pH enrichment test even before the saturation.

PET nano-woven luminescent fibers for efficient air filtration and fluorescence indication of particulate matter

Inhalable particulate matter poses significant health risks, and current air filtration materials often struggle with efficiently capturing particles smaller than 300 nm and providing real-time feedback on filtration performance. We present the synthesis and characterization of polyethylene terephthalate (PET) nano-woven luminescent fibers (PNWLFs), created through a positive and negative dual high-voltage electrospinning method. The PNWLFs feature a unique nano-woven structure composed of backbone fibers (200–1000 nm) and nanofibers (20–160 nm), which endow them with remarkable mechanical strength, maintaining a breaking force of 117.5 cN and structural integrity under a 138 mm water column. The fibers exhibit excellent breathability and waterproof performance, with a water vapor transmission rate of 4.69 kg/m2/day. More importantly, the PNWLFs demonstrate exceptional air filtration capabilities, achieving filtration efficiencies of 99.77 % for PM5.0, 99.76 % for PM2.5, 99.72 % for PM1.0, 99.53 % for PM0.5, and 99.40 % for PM0.3, with minimal pressure drop of 106 Pa. Additionally, these fibers possess a unique fluorescence-indicating function: the fluorescence intensity decreases in response to increasing particulate matter concentration and the number of filtration cycles, allowing for intuitive visual monitoring of filter performance and particulate levels. These attributes underscore the significant potential of PNWLFs synthesized by this work for advanced air filtration applications and effective air quality monitoring.

Natural filter: Adjustable hydrophobicity from biodegradable zein nanofiber membrane for high efficiency air purification

Faced with the fact that air filtration materials prepared from traditional petroleum-based materials do not have good biodegradability and have the risk of causing secondary pollution to the environment, a kind of nanofiber membrane with biodegradable polylactic acid (PLA) and zein was prepared by electrospinning method. The morphology of as-prepared membrane was carried out along with filtration performance and degradation performance both experimentally and theoretically. The results showed that the hydrophobicity of nanofiber membrane can be adjusted by changing the ratio of PLA and zein. In addition, the highest filtration efficiency for PM2.5 and PM10 was achieved when the ratio of PLA to zein was 1:1, and it could be stabilized at 98.14 % and 97.39 %, and had the highest quality factor (QF) of 0.00738 Pa−1. Moreover, the fiber membrane has excellent adsorption effect on aqueous particles as well as oily particles. Notably, the as-prepared composite filter can be easily biodegraded thus contributing to green ecological environment.

Preparation and properties of lightweight aluminum silicate-based fibrous ceramic membranes with different binder contents for high-temperature dust removal

Fibrous ceramic membranes are widely regarded as ideal hot-gas filtration media due to their unique three-dimensional network structure. In this work, deionized water and sodium lignosulfonate (NaLS) were respectively introduced into the preparation of fibrous ceramic membranes, with aluminum silicate fibers used as the matrix skeleton and silica sol used as the high-temperature binder. Their effects on the binder content, morphology, structural parameters, and mechanical properties were investigated and compared, and then the application performance of the preferred sample was evaluated. The results indicated that the addition of both significantly reduced the binder content, resulting in decreased bulk density and increased apparent porosity. Notably, compared to the addition of water, the addition of NaLS effectively preserved the binder content at the junctions between fibers so that the flexural strength and stiffness were barely affected, which benefits from the decrease in the viscosity of the binder liquid under the action of electrostatic repulsion and steric hindrance. Moreover, the preferred prepared fibrous ceramic membrane exhibited high-performance characteristics, such as superior thermal shock resistance, low pressure drop, and high filtration efficiency and pulse-jet cleaning efficiency, thereby offering considerable prospects for practical applications.

A closed-loop sustainable method for the fabrication of electrospun nanofiber using food waste for filtration of particulate matters (PMs) and volatile organic matter (VOCs) from air

Indoor air pollution significantly impacts human health and the environment. Humans suffer the greatest health burden due to inefficient combustion technologies and polluted fuels. Therefore, air filtration is essential for a healthy and prosperous household. This study aims to develop a sustainable approach for the fabrication of biodegradable electrospun nanofibers (ENs) as air filters from food waste materials and offer a closed-loop circular solution and potential replacement for non-biodegradable HEPA air filters. We have tested banana peel extract (BPE), eggshell membrane, chitosan, and starch blended with polyvinyl alcohol (PVA) for fabricating ENs. Among the nanofibers investigated for air filtration application, BPE/PVA nanofiber shows the best performance in terms of maximum particulate matter (PM) removal efficiency and minimum pressure drop while incorporating > 50 % of the food waste into the electrospinning solution. Adding BPE into a 10 % PVA solution leads to a reduction in the hydrophilic behavior of the BPE/PVA nanofiber as compared to neat 10 % PVA ENs. The BPE/PVA nanofiber shows minimum pressure drop (156–160 Pa) and highest quality factor (Qf) in comparison with other waste-derived nanofibers with > 98 % filtration efficiency of PM2.5. Further, BPE/PVA nanofiber shows the highest adsorption of xylene vapor among other food waste derived nanofibers studied. Based on the above results, it can be concluded that BPE based nanofiber shows the best performance as air filter media among all other food waste-based ENs. The study demonstrates a successful regeneration and reuse of the BPE/PVA filter up to 3 cycles. The leftover material from banana peels after BPE extraction was utilized as a soil ameliorant. It showed 55 % soil water retention (SWR) capacity, making it possible to apply in arid regions or crops with high water requirements.

Deciphering the Physical Characteristics of Ophthalmic Filters Used in Optometric Vision Therapy.

This paper aimed to measure and characterize eleven monochromatic filters and twenty-two combinations used empirically to treat patients with visual dysfunctions to propose enhanced protocols based on solid evidence. Their wavelength, transmittance, and relative sensitivity were defined on the retinal cone cells. A double-beam UV-VIS-NIR spectrophotometer, VARIAN brand, Cary 5000 model, owned by the National Center of Metrology, with high precision and accuracy, was used to characterize all filters. Filters were purchased from Optomatters Corporation, Belgium. When two or three filters are combined, their transmittance and relative sensitivity on the retinal cone cells decrease regardless of wavelength. As a result, the efficiency of combined filters may decrease during treatments. Additionally, most filters and combinations, regardless of the wavelength, transmit a considerable percentage of light from the red spectrum. A depressant is the best monochromatic filter, and Upsilon-Neurasthenic is the strongest combination to stimulate blue cone cells. In contrast, Stimulant and Delta-Theta are best for red and green cone cells. Mu-Delta and Mu-Theta can be interchangeable, as well as Alpha-Delta and Alpha-Theta. Results suggest that the current phototherapy treatment protocol must be deeply revised, and the number of filters and combinations should be reduced to reduce costs and time and boost efficiency.

Unraveling the impact of operational parameters and environmental conditions on the quality of viable bacterial aerosols.

Viable pathogen-laden droplets of consistent quality are essential for reliably assessing the protection offered by facemasks against airborne infections. We identified a significant gap in guidance within standardized tests for evaluating the filtration efficiencies of facemask materials using viable bacteria-laden aerosol droplets. An aerosol platform, built according to the American Society for Testing and Materials standard F2101-19, was used to validate and standardize facemask filtration test procedures. We utilized this platform to investigate the impact of varying five operating parameters, namely suspension media composition, relative humidity, pathogen concentration, and atomizer airflow and feed flow rates, on the aerosol quality of viable bacteria-laden aerosols. We achieved consistent generation of 1,700 to 3,000 viable bacteria-laden droplets sized between 2.7 and 3.3 µm under the following optimized test conditions: 1.5% w/v peptone water concentration, ≥80% relative humidity at 24 ± 2 °C, 1 × 105 CFU/mL bacterial concentration, 1.5 L/min atomizer airflow rate, and 170 μL/min feed flow rate. We also explored the consequence of deviating from these optimized test parameters on viable bacteria-laden aerosol quality. These results highlight the importance of controlling these parameters when studying airborne transmission and control.

Numerical Verification of a Polarization-Insensitive Electrically Tunable Far Infrared Band-Stop Meta-Surface Filter

Tunable filters have many potential applications in diverse fields, including high-capacity communications, dynamic beam shaping and spectral imaging. Although providing a high-performance solution for actively tunable devices, metasurface combined with tunable materials faces the great challenges of limited tuning range and modulation depth. Here, we propose a far-infrared tunable band-stop filter based on Fabry-Perot (FP) resonators and graphene surface plasmons. By switching the wavelength of the critical coupling condition of the filter via the gate voltage applied on graphene, achieving the dynamically tunable band-stop filtering at the central wavelengths from 12.4 μm to 14.1 μm with a modulation depth of more than 99%. Due to the symmetry of the proposed meta-atoms, the filter is insensitive to the polarization direction of the incident light. And it can realize more than 85% filtering efficiency within 60° angle of incidence around the vertical direction. By adjusting the geometry of the meta-atoms structure, it is feasible to move the operational range from the near-infrared to terahertz bands.