Air Load Research Articles

Calculation of the Optimal Loading of Air Vehicles Taking Into Account the Prioritization of Aircraft

Calculation of the Optimal Loading of Air Vehicles Taking Into Account the Prioritization of Aircraft

Static and random vibration analysis of an air freight package

Due to the significant speed advantage, air freight has become the preferred long-distance transportation method for precision electronic instruments and other high-value products. In order to avoid the impact of air load conditions on the safety of cargo and aircraft, it is necessary to calculate and check the carrying capacity of cargo package. In this paper, finite element analysis has been applied on design of an air freight package. Firstly, make force analyze, and use the maximum force for static analysis to solve stress distribution. Then, make modal analysis and random vibration analysis to obtain the 3σ stress and deformation. According to static analysis, the maximum equivalent stress of the package under emergency conditions is less thanσb. According to dynamic analysis, the probability that the maximum stress of the package is greater than 56.69Mpa does not exceed 0.3%.

Should homes and workplaces purchase portable air filters to reduce the transmission of SARS-CoV-2 and other respiratory infections? A systematic review.

Respiratory infections, including SARS-CoV-2, are spread via inhalation or ingestion of airborne pathogens. Airborne transmission is difficult to control, particularly indoors. Manufacturers of high efficiency particulate air (HEPA) filters claim they remove almost all small particles including airborne bacteria and viruses. This study investigates whether modern portable, commercially available air filters reduce the incidence of respiratory infections and/or remove bacteria and viruses from indoor air. We systematically searched Medline, Embase and Cochrane for studies published between January 2000 and September 2020. Studies were eligible for inclusion if they included a portable, commercially available air filter in any indoor setting including care homes, schools or healthcare settings, investigating either associations with incidence of respiratory infections or removal and/or capture of aerosolised bacteria and viruses from the air within the filters. Dual data screening and extraction with narrative synthesis. No studies were found investigating the effects of air filters on the incidence of respiratory infections. Two studies investigated bacterial capture within filters and bacterial load in indoor air. One reported higher numbers of viable bacteria in the HEPA filter than in floor dust samples. The other reported HEPA filtration combined with ultraviolet light reduced bacterial load in the air by 41% (sampling time not reported). Neither paper investigated effects on viruses. There is an important absence of evidence regarding the effectiveness of a potentially cost-efficient intervention for indoor transmission of respiratory infections, including SARS-CoV-2. Two studies provide 'proof of principle' that air filters can capture airborne bacteria in an indoor setting. Randomised controlled trials are urgently needed to investigate effects of portable HEPA filters on incidence of respiratory infections.

Non-intrusive measurement of building cooling load components via morphological components analysis

Load components reflect the amount of contributions that different building functional elements have made to the generation of total load during building operation. It will be helpful for a more accurate load prediction, and also for indirect evaluation on the thermal performance of building envelopes if the load components can be fully made out. However, in practical engineering, the data of load components cannot be obtained by field test. In this paper, benefiting from the different morphological features of load component profiles, a method based on morphological components analysis (MCA) is proposed to disaggregate cooling load into four parts with specific physical significance: temperature difference load, TCL; solar radiation load, SRCL; fresh air load, FACL; and internal load, ICL. Firstly, non-negative dictionary learning algorithm is introduced to learn the theoretical morphological feature of each load component adaptively. Secondly, non-negative sparse coding algorithm is adopted to disaggregate the time series of total load, and finally the load components are extracted from total load. Two cases with different settings using simulated data have been implemented. The results demonstrate that the proposed method can realize the load disaggregation effectively and accurately, where the accuracy index, Accuracy, is above 85% under different day attributes.

Study on heat transfer and dehumidification performance of desiccant coated microchannel heat exchanger

The desiccant coated heat exchanger is capable of dealing with sensible load and latent load of hot and humid air. The heat and moisture transfer coefficients of the desiccant coated microchannel heat exchanger (DMHE) are derived theoretically and increase with the airflow velocity in the heat exchanger. The microchannel structure optimization is implemented. It is found that the smaller the fin pitch and flat tube pitch are, the greater the heat and moisture transfer coefficients are. The thicker the desiccant coating, the larger the moisture transfer coefficient, the smaller the heat transfer coefficient. The experimental results show that the dehumidification capacity and the thermal performance coefficient of DMHE are 1.59 kgh−1 and 2.09 respectively with the regeneration hot water at 60 °C. The Taguchi method is employed to evaluate the influence of cooling water temperature, airflow velocity, and water flow rate on the dehumidification performance of DMHE. The airflow velocity is the main factor affecting the dehumidification capacity, where lower cooling water temperatures and faster the airflow velocity increases the dehumidification performance.

Bacterial Contamination in Health Care Centers: Differences between Urban and Rural Settings

This study aims to assess the airborne bioburden of rural and urban Portuguese Primary Health Care Centers (PHCC) using active and passive sampling methods and identify the potential differences in airborne microbiota between both environments. The highest total aerobic mesophilic bacterial load in indoor air were found in the Vaccination Room (448 CFU.m−3) in the Rural PHCC and in the Waiting Room (420 CFU.m−3) for Urban PHCC. The total coliforms contamination level in indoor air was detected only in the Cleaning Supplies Room (4 CFU.m−3) in the Urban PHCC. The most frequent bacteria genera identified was Micrococcus (21% Rural PHCC; 31% Urban PHCC). The surface samples showed a highest total aerobic mesophilic bacterial contamination in the Treatment Room (86 × 103 CFU.m−2) from the Rural PHCC and in the Front Office (200 × 103 CFU.m−2) from the Urban PHCC. The electrostatic dust cloth (EDC) samples showed a highest bacterial load in the Urban PHCC. Total aerobic mesophilic bacterial load in settled dust and in the Heating, Ventilating and Air Conditioning (HVAC) filter samples in the Urban PHCC (8 CFU.g−1 and 6 × 103 CFU.m−2) presented higher values compared with the Rural PHCC (1 CFU.g−1 and 2.5 × 103 CFU.m−2). Urban PHCC presented higher bacterial airborne contamination compared with the Rural PHCC for the majority of sampling sites, and when compared with the indoor air quality (IAQ) Portuguese legislation it was the Rural PHCC in two sampling places who did not comply with the established criteria.

Monitoring of porcine circovirus type 2 infection through air and surface samples in vaccinated and unvaccinated fattening farms.

Air and surfaces of swine farms are the two alternative samples to obtain information about the health status of the herd. The aim of this study was to assess air and surface sampling for the detection of porcine circovirus type 2 (PCV2) in vaccinated and unvaccinated fattening farms, studying the relationship between the viral load in these samples with the viremia at herd level. Three swine fattening batches (one unvaccinated; two vaccinated) were monitored at 10, 12, 14, 16 and 18weeks old; at each stage, blood, air and different surfaces were sampled and analysed by qPCR. In all herds, PCV2 was detected in all types of samples. Whenever viremia was detected, PCV2 was also detected in air and surface samples, even in those cases with a low estimated prevalence (1.6%); moreover, in two out of the three herds, PCV2 was detected in air and surface samples earlier than in the blood of the sampled population. In addition, a good correlation between the viremia of pig population and the PCV2 load in air and surface samples was found in both cases (τ=0.672 and 0.746, respectively; p<0.05). These results show that air and surface samples could be useful tools to monitor PCV2 infection, being suitable for detecting the virus in cases of low prevalence and even before pigs develop viremia; therefore, these sampling techniques would speed up the implementation of the required measures to prevent productive and economic losses due to PCV2 infection.

Strain-Aging-Assisted Localized Corrosion of a Mill-Scaled X-65 Pipeline Steel

This investigation was designed to study whether strain aging could assist localized corrosion of pipeline steels under realistic conditions, which is an unsolved problem in the evaluation of strain-aging-induced stress corrosion cracking of pipeline steels in the field. It was found that the corrosion severity was significantly aggravated after strain aging because of the increase in yield strength and the transformation of oxide scales on the steel surface. These variations caused by strain aging lead to lesser exfoliation and longer life of the oxide scales under cyclic loading in air and during subsequent corrosion exposure, which enhances the galvanic corrosion between oxide scales and the steel substrate. The composition of oxide scales, mechanical properties of steels, and magnitude of the stress cycles, which could all impact localized corrosion, were studied. The findings of this investigation suggest that the severe localized corrosion leading to crack initiation is a vital factor for the higher SCC susceptibility of pipeline steels associated with strain aging, in addition to the enhanced hydrogen embrittlement as usually believed.

Emissions Performance of Staged Premixed and Diffusion Combustor Concepts for an NH3/Air Flame With and Without Reactant Humidification

Abstract Renewably generated ammonia offers a form of carbon-free chemical energy storage to meet the differences between uncertain supply and fluctuating demand and has the potential to support future energy requirements. The storage/transportation characteristics of NH3 are favorable compared with H2; however, there are combustion research challenges to enhance fuel reactivity while reducing harmful emissions production. The purpose of this work was to evaluate different fuel delivery concepts for a representative gas turbine combustor. An experimental and numerical comparison was made between swirl-stabilized premixed and diffusion NH3–air flames at elevated inlet temperature (473 K). The exhaust NOx and NH3 emissions generated from each concept were quantified to optimize combustor performance. High-speed OH* and NH2* chemiluminescence was employed to characterize the change in flame topology with variation in fuel–air equivalence ratio, and the resultant influence on measured emission concentrations. Chemiluminescence intensities were shown to elucidate changes in sampled exhaust emissions, enabling detailed analysis of intermediate chemistry. A comparison was made between experimental data and kinetic simulations, demonstrating the sensitivity of NOx emissions to premixed fuel–air equivalence ratio. A comparison was also made between exclusive primary airflow, and the staged introduction of secondary air, to quantify the change in NOx production between each configuration and improve fuel burnout. Secondary air loadings were incrementally increased through the combustor. Finally, reactant humidification was employed as a secondary process for NOx reduction, having shown favorable performance with NH3–H2 mixtures, with the efficacy compared for both premixed and diffusion configurations.

Modeling and simulation of forces applied to the horizontal axis wind turbine rotors by the vortex method coupled with the method of the blade element

This work focuses on the study of the forces applied to the rotors of horizontal axis wind turbines. The aerodynamics of a wind turbine is regulated by the flow around the rotor, where the prediction of air loads on the rotor blades in various operational conditions and its relationship with the structural dynamics of the rotor is crucial for design purposes. One of the most important challenges in the aerodynamics of wind turbines therefore to accurately predict the forces on the blade when the blade and the wake are modeled by different approaches such as the theory of the blade element (BEM) the vortex method and CFD method which involves solving the Navier-Stokes equations. In our article, the model is used for modeling and simulate the forces applied to the rotors of wind turbines horizontal axis use the application of the method of the blade element for modeling the rotor and the vortex method of free wake modeling in order to develop a model of the rotor, which can be used to study wind farms. This model is intended to speed up the calculation, guaranteeing a good representation of aerodynamic loads exerted by the flow of wind.

An MDO-based methodology for static aeroelastic scaling of wings under non-similar flow

The classical aeroelastic scaling theory used to design scaled models is based on the assumption that complete flow similarity exists between the full aircraft and the scaled model. When this condition is satisfied, the scaling problem of the model can be treated as a structural design problem only, where the scaled aerodynamic shape is preserved. If, on the other hand, this hypothesis no longer holds—if the scaled model is constrained to fly at low speed and low altitude, for example—and both the aerodynamic shape and the flexibility of the structure are exactly scaled, then the static response exhibits significant discrepancies in the aerodynamic loads and structural displacement. To design a flying demonstrator with scaled static response when flow similarity cannot be fulfilled, we present a multidisciplinary optimization-based method that allows some freedom in the design of the wing shape (while keeping the scaled wingspan) to update the wing geometry and structural properties to ensure equivalent scaled loads and overall wing displacement. To illustrate this method, we apply it to a 1:5 version of the uCRM wing at subsonic flight condition. While the errors in air loads using the classical theory are around 16%, the presented method achieves errors lower than 1%, with a good agreement for the wingtip displacement.

Actuator Surface Model with Computational-Fluid-Dynamics-Convected Wake Model for Rotorcraft Applications

An actuator surface model has been developed that couples an aerodynamics model to a computational fluid dynamics solver. The model is designed for simulation of rotors in complex operating environments, and it advances a recently developed actuator surface model through the addition of two new elements: a computational fluid dynamics (CFD)-convected wake model, and an improved coupling algorithm. The wake model uses Lagrangian particle tracking to determine the geometry of the rotor wake from the CFD solution. Prior study of the influence of the maximum wake age in the model led to the conclusion that only 45 deg of wake is required for accurate resolution of air loads. The S-76 rotor in hover and the UH-60A rotor in forward flight are used for validation. Thrust coefficients, torque coefficients, and figures of merit over a range of collective settings agree well with experimental data for the S-76 rotor. Sectional normal force coefficients in forward flight are compared with experimental data, results from resolved-blade simulations, and other rotor models: again showing good agreement. These results suggest the new actuator surface model can predict time-accurate rotor loads where accurate resolution of the near-blade flowfield and high-frequency loads, such as blade–vortex interactions, are not critical.

A Comparative Overview of Accident Forecasting Approaches for Aviation Safety

The demand of air transportation is expected to be doubled over the next two decades as per the recommendations of the International Air Transport Association. This would prompt more aviation safety issues with increased air traffic congestion and load on the air transportation system. To estimate the level of risk and improve the forecasting ability, various methodologies have been proposed by the research community. As each methodology has its pros and cons, this manuscript provides a comparative study of various Data mining, Time series, Artificial Neural Networks, and ensemble Techniques on the aviation safety and forecasting complication. This paper concludes that different methods dealing with different information may be combined to have an outstanding prospective in aviation accident forecasting and to come up with a number of ways of enhancement and their assistance in decision making.

Performance characteristics of modified turbocharger for a two wheeler engine

Single-cylinder SI enginenormally supply air to operate above ambient pressure. Pressurized air is necessary to scavenge the exhaust gas cylinder and the load of air was delivered to the next power stroke by mechanical air compressors or by reciprocating compressors using the space beneath the piston. The engine provided the air-pressure capacity, which reduces the useful work obtained by the engine by the same quantity. In order to operate efficiently, the turbo charge uses between 7 and 8% of total power, i.e. 20 to 25%. A spinning compressor is powered by the rotor shaft. Owing to compression, the intake temperature changes. If the compressed air is chilled in a refrigerator, it would be cheaper to maximise the air density. The engine's output is increasing with the turbocharger being implemented.

Evaluation of Wave-induced Coupled Dynamics Between Multi-purpose Offshore Supply Vessel and Suspended Load During Crane Lifting Operation

As crane lifting operation in ocean is vital to construct offshore structures and install subsea facilities on the seafloor, evaluation of safety and availability for the crane lifting operation is needed before the construction. For these analyses, it's fundamental to predict wave-induced coupled dynamics between a vessel and a suspended load. The coupled dynamics makes the each mechanics more complex. In the case of using the multi purpose offshore supply vessel to the crane lifting operation, deep understanding about the mechanics is required because it offers various crane operations. In our previous paper, we propsed the numerical method to estimate the swirling of the suspended load in air and considered the impact of the suspended load's location on the coupled dynamics using the both numerical calculation and estimation method. To expand our knowledge and numerical method for the crane operation, we inestigated the coupled dynamics right after the suspended load entry into the sea surface. In such the situation, it's possible that the hydrodynamics on the suspended load change the coupled dynamics and produce unexpected risk for the crane lifting operation. In this paper both experiments and numerical simulation we conducted are shown to consider the coupled dynamics between the vessel and the suspended load. Furthermore we indicated the results of sensitivity analysis by numerical simulation to put the point of focus on the natural period of the vessel's roll motion. As results, we made clear the inversion of the natural period could be occured depending on where the location of the suspended load is.

Application of Molecular Dynamics Calculations to Elucidation of the Mechanism of Hydrogen-Induced Crack Initiation in Fracture Toughness Tests Using Tempered Martensitic Steels

It is well known that the presence of hydrogen deteriorates mechanical properties of steels, that appears as reduced fracture toughness, shorter fatigue lifetime, etc.; these phenomena are recognized as hydrogen embrittlement. The effect of hydrogen on crack initiation of fracture toughness test has been investigated using a combination of experimental and computational approaches. Tempered lath martensitic steel was subjected to fracture toughness test with monotonically rising load in air and high-pressure hydrogen gas. While crack propagated continuously within grains in air, cracking in hydrogen grew by linking isolated interface failure ahead of a main crack tip. Then, to understand the nucleation mechanism of isolated failure in the presence of hydrogen, the tensile simulations of twist grain boundaries (TGBs) rotated along <110> axis at various angles were conducted using molecular dynamics calculations. While the dislocation emission from TGB rotated 70° is dominant deformation mode in the absence of hydrogen, the rupture along TGB rotated 110° and 170° without stress relaxation due to dislocation emission is dominant deformation mode in the presence of hydrogen. As a consequence, it is indicated that the origin of hydrogen-induced isolated crack initiation in the vicinity of fatigue pre-crack is the rupture along the block boundaries within martensitic structure due to hydrogen-induced inhibition of dislocation emission from GBs.

Design and Control Method of Combined Air Conditioning System Considering the Sharing of Outdoor Air and Room Load Processing

Design and Control Method of Combined Air Conditioning System Considering the Sharing of Outdoor Air and Room Load Processing

A theoretical design method for the nozzle pitch of air-flotation system to reduce large liquid crystal display glass substrate\u2019s deformation

The deformation of large glass substrate in air-flotation system affects detection accuracy of inspection instrument. According to the gas lubrication theory, Timoshenko’s thin film theory and the simulation figure of the pressure distribution of the air film flow field, the air load distribution model of the air film is established, and the deformation expression of the large liquid crystal glass substrate in air-flotation system is given. On this basis, a theoretical design method for designing nozzle pitch of orifice throttling air-flotation system was proposed. Combined with examples, the results of theories and simulation are compared. An experiment on the deformation of the glass substrate was carried out on an experimental prototype. The difference between the experimental results and the theoretical results does not exceed 10%.

Vacuum retarding and air accelerating effect on the high-cycle and very-high-cycle fatigue behavior of a ZK60 magnesium alloy

It is suspected early that the ultra-slow crack propagation in fine-granular-area (FGA) may be sensitive to the internal vacuum-like environment. In other words, fatigue failure in the very-high-cycle regime may be related to the internal vacuum-like environment. Since magnesium alloy is more susceptible to the environmental effect, it is selected as the research carrier in this study. A magnesium alloy is investigated in ambient air and vacuum environments comparatively, and the vacuum loading environment offers a valuable reference to investigate the possible environmental effect. The results show that plastic deformation mechanism in different loading environments keeps the same at crack initiation site. However, the different loading environments not only change the fatigue life, but also the failure mode. At higher stress levels, surface failure dominates in air loading environment, whereas internal failure dominates in vacuum loading environment and presents longer fatigue life. It is considered that failure mode in vacuum loading environment is mainly affected by the critical grains, whereas that in air loading environment is mainly affected by the competition between the surface air acceleration effect and the critical grains. Fatigue life is mainly affected by the internal vacuum retarding effect and the surface air accelerating effect.

Comparison on failure behavior of three-dimensional woven carbon/carbon composites joints subjected to out-of-plane loading at room and high temperature

In the present work, an experimental investigation on the failure of 3D woven carbon/carbon all-composites mechanically fastened bolted joints with protruding-head and countersunk-head bolts has been implemented under out-of-plane loading in air at room temperature and up to 1100 °C for the first time. The load-displacement curves and main damage mechanisms for the required temperature points were determined and evaluated, respectively. It follows that, for room temperature, the global mechanical response was characterized by pseudoplastic, and the failure was dominated by the damage mechanisms including matrix cracking, interface debonding and threads fracture, especially, edge bending to breakage occurring for countersunk fastener. For 1100 °C, silicon carbide ceramic anti-oxidation coating was applied to prevent from oxidizing. Due to the relief of the thermal stresses, joints bearing capacity was enhanced by fiber/matrix interface performance improvement accompanying with a brittleness tendency of mechanical response, and the dominating failure mechanisms were carbon/carbon substrate oxidation caused by air entering through the cracks in SiC coating.