Air System Research Articles

Can air handling equipment be beneficial to children’s health? Results from a cross-sectional survey in 2010 and 2019 in China

A growing number of studies have shown that the indoor residential environment is associated with respiratory and allergic diseases in children. This study aimed to investigate the prevalence of respiratory and allergic diseases among children in China and its correlation with using air handling equipment, based on the cross-sectional survey results of the China Children Homes Health Project in 2010 and 2019. The binary logistic regression model was used to explore the association between asthma, rhinitis, eczema and pneumonia and the use of air handling equipment in children. The prevalence of children’s respiratory and allergic diseases has decreased, and the usage rate of portable air purifiers and split air conditioners has increased in 2019 compared to 2010. The results showed that using a fresh air system with filters was negatively correlated with children’s pneumonia (adjusted odds ratio (aOR): 0.767, 95% confidence interval (95% CI): 0.704–0.835). The use of portable air purifiers was positively correlated with most diseases’ symptoms in two undertaken surveys. In 2019, the positive correlation between using split air conditioners and asthma-related symptoms decreased compared with 2010, while it was positively correlated with rhinitis, eczema and pneumonia. To avoid children’s allergic diseases and reduce respiratory symptoms, parents should choose appropriate air handling equipment.

Water Adsorption in MOFs: Structures and Applications

AbstractMetal–organic frameworks (MOFs) are superior sorbents for water adsorption‐based applications. The unique step‐like water isotherm at a MOF‐specific relative pressure allows easy loading and regeneration over a small range of temperature and pressure conditions. With good hydrothermal stability and cyclic durability, it stands out over classical sorbents used in applications for humidity control, water harvesting, and adsorption‐based heating and cooling. These are easily regenerated at moderate temperatures using “waste” heat or solar heating. The isotherm thermodynamics and adsorption mechanisms are described, and the presence of MOFs in the water–air system is explained. Based on six selection criteria ≈40 reported MOFs and one COF are identified for potential application. Trends and approaches in further synthesis optimization and production scale‐up are highlighted. No‐MOF‐fits‐all, each MOF has its own specific step location matching only with a certain application type. Most applications are technically feasible and demonstrated on the bench‐scale or small pilot. Their maturity is benchmarked by their technology readiness level. Retrofitting existing applications with MOFs replacing classical desiccants may lead to rapid demonstration. Studies on techno‐economic analysis and life cycle analysis are required for a rational evaluation of the feasibility of promising applications.

Application of a Partially Invariant Exact Solution of the Thermosolutal Convection Equations for Studying the Instability of an Evaporative Flow in a Channel Heated from Above

The characteristics of a stationary flow of a volatile liquid driven by a co-current gas flux in a flat horizontal mini-channel upon the non-zero transverse temperature drop are studied. We use an exact solution of the thermosolutal convection equations for describing the heat and mass transfer caused by the combined action of gas pumping, buoyancy, thermocapillarity and linear heating of the channel walls in a two-layer system. The influence of heating from above on the parameters of the ground state and the stability characteristics of the basic flow is explored using an example of the ethanol–air system. We evaluate the thresholds of the linear stability and select the most dangerous modes. Heating from above results in flow stabilization. Instability appears in the form of oscillatory cellular convective patterns.

Intelligent Approaches for Anomaly Detection in Compressed Air Systems: A Systematic Review

Inefficiencies within compressed air systems (CASs) call for the integration of Industry 4.0 technologies for financially viable and sustainable operations. A systematic literature review of intelligent approaches within CASs was carried out, in which the research methodology was based on the PRISMA guidelines. The search was carried out on 1 November 2022 within two databases: Scopus and Web of Science. The research methodology resulted in 37 papers eligible for a qualitative and bibliometric analysis based on a set of research questions. These aimed to identify specific characteristics of the selected publications. Thus, the review performed a comprehensive analysis on mathematical approaches, multiple machine learning (ML) methods, the implementation of neural networks (NNs), the development of time-series techniques, comparative analysis, and hybrid techniques. This systematic literature review allowed the comparison of these approaches, while widening the perspective on how such methods can be implemented within CASs for a more intelligent approach. Any limitations or challenges faced were mitigated through an unbiased procedure of involving multiple databases, search terms, and researchers. Therefore, this systematic review resulted in discussions and implications for the definition of future implementations of intelligent approaches that could result in sustainable CASs.

A Method for Constructing Health Indicators of the Engine Bleed Air System Using Multi-Level Feature Extraction

Traditional methods are unable to effectively assess the health status of engine bleed air systems. To address the limitation, this paper proposes a methodology for constructing health indicators using multi-level feature extraction. First, this approach involves data-level feature extraction from Quick Access Recorder (QAR) data and employs a method of significance compensation to process the QAR data. Second, through unsupervised learning, the ResNet Deep Autoencoder (RDAE) is utilized to do the feature-level feature extraction from the processed data. This can solve the problem of lacking annotated data and obtain the health indicators of the engine bleed air system. Third, the method was experimented on one year of QAR data from a specific airline company. The results demonstrate that the RDAE approach achieves the best performance in constructing health indicators for the system. It achieves a miss rate of 0.0523 for the duct pressure of 5th stage bleed, reducing the miss rate by 0.2810 compared to Kernel Principal Component Analysis (KPCA). It also achieves a miss rate of 0 for the pre-cooler outlet temperature, reducing the miss rate by 0.0035 compared to the Deep Autoencoder (DAE). The results indicate that the proposed method provides a more effective assessment of the health status of the engine bleed air system.

Response surface modeling and optimization scheme of an internally cooled liquid desiccant air conditioning system

Applying an internally cooled liquid desiccant air conditioning system (LDAC) is a promising energy-saving and emission-reduction scheme for hot and humid areas. This research investigates the application of an internally cooled LDAC for performance enhancement in hot and humid areas like Hong Kong. The combined system integrates liquid desiccant dehumidification (LDD) and regenerative indirect evaporative cooling (RIEC) without a power-intensive compressor. The internally cooled LDD removes latent heat from the hot and humid air before the RIEC cools it. To ensure efficient energy utilization, the LDD captures the exhaust air to assist in the dehumidification and initial cooling of the fresh air, which alleviates the efficiency deterioration of the desiccant. An all-fresh air system is used for better indoor air quality. To optimize the performance of a system with many influencing parameters, the response surface method (RSM) and multi-objective optimization are used to optimize and assess the potential and performance of the system. The system cooling capacity (C), latent heat removal rate (Qd), and dehumidification efficiency (ηd) are used as the optimization objectives. The response surface model and desirability function approach optimize six critical parameters, achieving a 7.6% improvement in dehumidification performance with low airspeed (1.5 m/s) and high desiccant concentration (40%) during high-humidity months. Increasing the extraction ratio of the RIEC by 20% in warmer months enhances the peak cooling capacity by 23.6%. This research contributes to implementing internally cooled LDAC systems and provides insights into optimizing monthly operation patterns in hot and humid regions.

Aerodynamics and Sealing Performance of the Downstream Hub Rim Seal in a High-Pressure Turbine Stage

The purpose of the paper is to characterize the aerodynamic behavior of a rotor-downstream hub cavity rim seal in a high-pressure turbine (HPT) stage. The experimental data are acquired in the Transonic Test Turbine Facility at the Graz University of Technology: the test setup includes two engine-representative turbine stages (the last HPT stage and first LPT stage), with the intermediate turbine duct in between. All stator-rotor cavities are supplied with purge flows by a secondary air system, which simulates the bleeding air from the compressor stages of the real engine. The HPT downstream hub cavity is provided with wall taps and pitot tubes at different radial and circumferential locations, which allows the performance of steady pressure and seed gas concentration measurements for different purge mass flows and HPT vanes clocking positions. Moreover, miniaturized pressure transducers are adopted to evaluate the unsteady pressure distribution, and an oil flow visualization is performed to retrieve additional information on the wheel space structures. The annulus pressure asymmetry depends on the HPT vane clocking, but this is shown to have negligible impact on the minimum purge mass flow required to seal the cavity. However, the hub pressure profile drives the distribution of the cavity egress in the turbine channel. The unsteady pressure field is dominated by blade-synchronous oscillations. No non-synchronous components with comparable intensity are detected.

Deterministic and Probabilistic Approaches to Model and Update Dynamic Systems

Updating simulation models, based on flight test or other data, or creating a model using only experimental data is a necessary process that can be costly and laborious. Simulation updates are necessary for high-fidelity simulations used in analysis, control development, handling qualities prediction, fleet training, etc. This paper presents methods to update aircraft models based on deterministic and probabilistic approaches. The deterministic approach is based on a collection of signal processing, statistical analysis, and maximum likelihood estimators embodied in the Algorithms to Update Simulation Parameters with Experimental Data tool. Mathematically sound and statistically rigorous techniques are used to calculate updates of current model parameters and suggest new terms capturing unmodeled dynamics, thereby improving correlation with observed vehicle response. The probabilistic approach is based on generalized polynomial chaos theory included in the Algorithms for Uncertainty Representation and Analysis (AURA) tool. The AURA tool allows the user to update probabilistic models based on experimental data, formulated as a Bayesian inference problem. This paper will present the methodology for both deterministic and probabilistic approaches and provide examples of their application to different aircraft designs, including tilt-rotor and rotary-wing unmanned air system vehicles. The results for both deterministic and probabilistic modeling approaches demonstrate excellent results. The probabilistic approach is novel in its expressive power to propagate and update probabilistic models and provides users with an intuitive and powerful modeling approach.

Research on the strong transient process of the secondary air system in the Aero-engine based on the network method

A coupled model of engine mainstream way with secondary air system was established based on the network method. The change rule of engine performance, air system parameters and axial force was simulated when the aero-engine was sunk in shaft failure. The dynamic parameters of the secondary air system could be forecast accurately based on the analysis of transient algorithm, and the transient axial force also could be calculated. So the simulation data can be provided for the engineering design, and it can help the designer improve the secondary air system design. Moreover, its modular character allows integration of further detailed air-system unites and establishment of more complex air system network. The resultant modular tool is prospect in studying the complex dynamic characteristics and mechanism in Aero-engine air system.

Research on pressure dynamic characteristics of multi-cavity model in aero-engine secondary air system

An algorithm for the basic elements was established based on the physical mechanism of transient secondary air system. A simulation program was compiled by using object-oriented language. Then a multi-cavity transient model of the secondary air system was established, and the pressure dynamic characteristics of the multi-cavity model were analyzed. The transient modeling of the air system has practical engineering versatility by establishing a standard interactive interface, and the transient modeling and analysis of the air system in different engines can be realized through using each component module. Such simulation research can help engineers to improve the design flow path of the secondary air system, and provide simulation data for the airworthiness design of engine, which has certain application value.

Improving the efficiency of energy saving through the use of thermal energy

The article analyzes the problem of energy saving in the context of organizational and technical measures. One of the energy saving factors is the use of waste heat of various potential. The advantages of using waste heat in the energy sector and the scope of their application are considered. Power plants for waste processing and their parameters are described. Examples of the creation of special energy devices for the chemical industry are given. The connection of internal (by-product) energy resources (IER) with technologies using melting furnaces is noted. The boundaries of the use of heat recovery boilers (HRB) in various industries are determined. The schemes of HRB application at the wastewater disposal site with quantitative and qualitative characteristics are given. A method for improving economizers using bimetallic pipes and heat exchangers is given. The use of batteries in the disposal and consumption of waste heat is justified. The ways of increasing the efficiency of compressed air systems and the features of using arc steelmaking furnaces to reduce energy consumption are considered. The comparison of local heat supply schemes with regenerative ones is carried out and the prospects for the development of these schemes are noted.

МОНИТОРИНГ КАЧЕСТВА МОТОРНОГО МАСЛА ПО НАКОПЛЕНИЮ НЕРАСТВОРИМЫХ МЕХАНИЧЕСКИХ ПРИМЕСЕЙ

The quality of the oil deteriorates during the intensive operation of agricultural machinery engines in adverse conditions, which leads to wear of the rubbing surfaces of parts, disruption of the engine and an increase in the risk of an emergency operating or emergency situation. The causes of emergencies of engine components, as well as methods for their reduction through the use of an engine oil diagnostic system, are discussed in the article. The degree of contamination of engine oil with insoluble impurities is one of the diagnostic parameters by which the operability of the entire technical system is determined. Modern methods of analysis (laser diffraction, electron X-ray microscopy) have established the main characteristics of impurities in used engine oils and their relationship with the degree of wear of engine elements of agricultural machinery. The use of this type of diagnostics allows you to assess the condition of the most important systems of the car. The diagnosed signs can show the presence of technical problems of the fuel and air systems, the cylinder piston group of the engine, and violations in operation. It is proposed to use the elementary concentration of iron in the selected samples of engine oil as a diagnostic parameter of tribomonitoring, which is an indicator of the degree of wear of parts of the piston group of the engine of agricultural machinery. The dependence of the metal concentration (CFe) in engine oil on the silicon content (CSi) obtained from the results of X-ray spectral microweighting is approximated by an exponential dependence, which increases the accuracy of predicting the engine oil resource and the technical condition of the car. The use of these control methods makes it possible to unambiguously determine the nature of equipment operation and detect the occurrence of defects in a timely manner.

АНАЛІЗ ВПЛИВУ ТЕМПЕРАТУРИ ЗОВНІШНЬОЇ СЕРЕДИ НА РОБОТУ ФОТОЕЛЕКТРИЧНИХ СТАНЦІЙ

This work is devoted to the study of the mechanism of increasing the efficiency of solar photovoltaic generation by integrating the compressed air system. The main aspects of this mechanism, its advantages and influence on the improvement of the process of converting solar energy into electrical energy are considered. The relevance of this topic is due to the constant growth of electricity consumption and the need to create efficient and sustainable solar power plants. Solar photovoltaic generation is already a promising source of renewable energy today, but it has certain limitations, in particular, related to the increase in temperature of solar panels and uneven distribution of solar radiation. This paper examines the integration of a compressed air system with solar panels to increase the efficiency of solar PV generation. The use of compressed air allows you to lower the operating temperature of the panels, which leads to an increase in the efficiency of solar energy conversion. In addition, it helps to unify the lighting of the panels and improves the performance of all photovoltaic modules. An important aspect of the work is the analysis of the influence of the integrated compressed air system on the energy characteristics of solar panels. The study includes modeling and experimental determination of changes in efficiency, energy output, and stability of solar panels when using a compressed air system. The obtained results allow us to draw conclusions about the efficiency and practical implementation of an integrated system of compressed air for solar photovoltaic generation. The identified advantages of this approach make it possible to recommend it for use in modern solar power plants in order to increase efficiency and ensure stable operation.

Condition Monitoring and Fault Diagnosis of a Marine Diesel Engine with Machine Learning Techniques

A marine engine room is a complex system in which many different subsystems are interacting with each other. At the center of this system is the main diesel engine which produces the propulsion force. Many other components such as compressed air, cooling, heating, lubricating oil, fuel, and pumping systems act as auxiliary machines to the main engine. Automation of many functions in the engine room is starting to play an important role in new generation ships to provide better control using sensors monitoring the engine and its environment. Sensors exist in the current generation ships, but engineers evaluate the sensor data for the presence of any problems. Maintenance actions are taken based on these manual analyses or regular maintenance is carried out at times determined by manufacturers, whether such actions are needed or not. With machine learning, it is possible to develop an algorithm using past evaluations made by engineers. Recent studies show that highly accurate results can be obtained using machine learning methods when there is sufficient data. In this study, we develop new learning-based algorithms and evaluate them on data obtained from a realistic ship engine room simulator. Data for a predetermined set of parameters of a high-power diesel engine were collected and analyzed for their role in a set of fault situations. These fault conditions and the associated sensor data are used to train a set of classifiers achieving fault detection up to 99% accuracy. These are promising results in preventing future damage to the engine or its supporting components by predicting failures before they occur.

Pressure drop of structured packing in pilot column and comparison to common correlations

Packed columns are widely used in the chemical industry such as absorption, stripping, distillation, and extraction in the production of e.g. organic chemicals, and pharmaceuticals. Pressure loss and pressure drop correlations are of special interest when it comes to the hydrodynamic properties of a column. The pressure loss across the column is of interest in the design phase when the size of the blower to drive the gas stream through the column has to be decided. The loading point and flooding point are also influenced by the pressure loss and the area of operation is determined from these points. This work examines four different correlations on pressure drop. The correlations are (i) Ergun’s equation (1952), (ii) an improved version of Ergun’s equation by Stichlmair, Bravo, and Fair (1989), (iii) an equation developed by Billet and Schultes (1999), and (iv) an equation by Rocha, Bravo, and Fair (1993). The complexity of the correlations is increasing in the mentioned order, Ergun’s equation being the simplest one. This study investigates if the more complicated correlations give better predictions to pressure drop in packed columns. This is determined by comparing the correlations to experimental data for pressure drop in a packed column with 8.2 m of structured packing using water as the liquid and atmospheric air as the gas. Seven experiments were carried out for determining the pressure drop in the column with liquid flows varying from 0 to 500 kg·h−1. At constant liquid flow, the gas flow was varied from approximately 10 to 70 kg·h−1. The pressure drop across the non-wetted column was best described by the correlation by Rocha et al. while the pressure drop for liquid flows from 100 to 500 kg·h−1 was, in general, best described by Stichlmair’s equation. For an irrigated column, the highest deviation was a predicted pressure drop 69.6% lower than measured. The best prediction was 0.1% higher than the measured. This study shows, surprisingly, that for a system of water and atmospheric air, complicated correlations on pressure drop determination do not provide better estimates than simple equations.

Auxiliary ventilation systems in mining and tunnelling: Air leakage prediction and system design to optimize the energy efficiency and operation costs

The excavation of tunnels and mining roadways requires auxiliary ventilation systems to dilute the noxious gases from blasting and diesel engines and provide a safe environment for workers. Therefore, axial fans and ducting systems are generally installed to supply the required airflow rate to the working face. Due to the air leakage, the airflow rate varies along the ventilation duct and the design of the ventilation system is complex when leaky ducts are used. Thus, to ensure the required airflow rate at the working face, a proper sizing of the ducting system and auxiliary fan must be carried out. In this paper, analytical and CFD numerical models have been conducted to investigate auxiliary ventilation systems considering different qualities of the ventilation ducts. A forced duct of 0.6 m in diameter and 200 m long in a 14 m2 cross section mining roadway has been selected to predict the pressure drop and the air leakage along the duct. In addition, the power of the fan and the energy consumption have also been studied in the analytical models to optimize the energy efficiency and ventilation costs. The results obtained show that the power of the fan can be reduced by 74% if a duct 0.8 m in diameter is installed. Good agreements were obtained between the numerical approach and the analytical results. Finally, novel nomograms have been developed to design the ducting system and the auxiliary fans and estimate the energy consumption as a function of non-dimensional variables. Duct diameters between 600 and 2400 mm and tunnel lengths up to 4000 m can be selected to design the auxiliary ventilation circuits optimizing the operation costs.

Thermodynamic Consideration of the Solid Saponin Extract Drop-Air System.

The aim of this research was to elucidate the surface active properties of Saponaria officinalis (soapwort) extract containing the plant surfactants saponins. To this end, the advancing contact angle (θ) of water, formamide and diiodomethane on the glass, as well as θ of the aqueous solution of S. officinalis extract fractions on PTFE, PMMA and glass, were studied. Based on the obtained results, the wetting behaviour of saponins was considered with regard to the surface tension components and parameters of the solutions and solids. The investigations also involved the description of the θ isotherms, the dependences between the cosine of contact angle and/or the adhesion of the solution to the solid surfaces and solution surface tension, as well as the critical surface tension of PTFE, PMMA and glass wetting. These dependences were studied based on the saponin adsorption at the different interfaces, which was deduced from the dependence between the adhesion and surface tension of the solution, as well as using the Gibbs and Frumkin isotherm equations. This proved that the saponins are poor wetting agents and that the contact angle isotherm can be described by the exponential function of the second order as well as the Szyszkowski equation, but only for PTFE.

A novel combined model for energy consumption performance prediction in the secondary air system of gas turbine engines based on flow resistance network

Predicting the comprehensive energy consumption is challenging for the complicated secondary air system. To solve this problem, a universal flow resistance element has been constructed to describe different components more accurately. And a novel flow resistance network is proposed to calculate the system's energy consumption. This network can be analyzed by the flow resistance characteristics of its components to estimate the energy consumption of each component and the energy loss of the system. Furthermore, a flow resistance parameter is defined as a unique factor to determine the magnitude of flow resistance for each component. Compared to experimental and numerical results, both models demonstrate sufficient accuracy in calculating mass flow rates and entropy increments, with the maximum deviation less than 1.2%. The above two models are also applied to predict flow losses of elements with changes in pressure and inlet total temperature, with the maximum deviation less than 4.5%. Based on the flow resistance network, the aerodynamic performance of each element can be easily computed by the inlet and outlet boundary of this system, regardless of whether the elements are arranged in series or parallel.

Enabling off-highway diesel engine downsizing and performance improvement using electrically assisted turbocharging

Internal combustion engine (ICE) downsizing through various turbocharging configurations is generally known by the powertrain design community as an effective means to reduce frictional losses, increase waste heat recovery, and improve fuel efficiency while increasing engine power density. However, often is the case that turbocharging strategies, including variable geometry turbochargers, and regulated two-stage turbochargers, incur the performance tradeoff between transient response and fuel economy (pumping losses) at high engine speeds. For off-highway vehicles having particularly transient and high-powered duty cycles, efforts to improve this tradeoff and increase operational flexibility have turned to evaluating various electrified air system architectures. In this study, a 4.5 L diesel-ICE configured with an electrically driven compressor (eBooster®) is placed in series with a conventional turbocharger and integrated into a 48 V mild-hybrid powertrain architecture. The objective of this powertrain configuration is to enable engine downsizing by 34%, replacing the current 6.8 L ICE platform with the hybridized 4.5 L ICE concept. The commercial 1-D simulation software GT-SUITE is used for powertrain system development and system optimization. Development and validation of the GT-SUITE model and air system controls is concurrently supported through experimental data collection. The simulation model development includes using machine learning methods for optimizing exhaust gas dilution, injection timing, and eBooster® power to improve steady-state and transient brake-specific fuel consumption while minimizing criteria pollutant emissions. It was found that total specific fluid consumption over the standardized non-road transient engine duty cycle could be reduced by 18% over the current 6.8 L engine by using an optimized eBoosted 4.5 L engine. The hybridized 4.5 L engine concept concurrently showed sufficient transient response capability and nearly an order of magnitude reduction in duty cycle total soot production.

Application of unmanned air systems in agriculture

The purpose of this article is to consider the use of unmanned aerial systems (UAS) in agriculture. UAVs have great potential in many agricultural tasks. This article summarizes the current state of drone technology and its applications in agriculture, including plant health monitoring, weed control, spraying, and other agricultural operations.