Search Results (33)

Air pollution represents a critical environmental challenge in stressed riverine cities, particularly in regions experiencing rapid urbanization and inadequate emission management infrastructure. This study investigates the spatio-temporal dynamics of atmospheric pollution in Baghdad, Iraq, during 2012–2023, analyzing seven key pollutants (CO, CO₂, SO₂, SO₄, O₃, CH₄, and AOD) using NASA’s Giovanni platform coupled with Google Earth Engine analytics. Monthly time-series data were processed through advanced statistical techniques, including Seasonal Autoregressive Integrated Moving Average (SARIMA) modeling and correlation analysis with meteorological parameters, to identify temporal trends, seasonal variations, and driving mechanisms. The analysis revealed three distinct pollutant trajectory categories reflecting complex emission–atmosphere interactions. Carbon monoxide exhibited dramatic decline (60–70% reduction from 2021), attributed to COVID-19 pandemic restrictions and demonstrating rapid responsiveness to activity modifications. Conversely, greenhouse gases showed persistent accumulation, with CO₂ increasing from 400.5 to 417.5 ppm and CH₄ rising 5.9% over the study period, indicating insufficient mitigation efforts. Sulfur compounds and ozone displayed stable concentrations with pronounced seasonal oscillations (winter peaks 2–3 times summer levels), while aerosol optical depth showed high temporal variability linked to dust storm events. Spatial analysis identified pronounced urban–rural concentration gradients, with central Baghdad CO levels exceeding 0.40 ppm compared to peripheral regions below 0.20 ppm. Linear concentration patterns along transportation corridors and industrial zones confirmed anthropogenic source dominance. Correlation analysis revealed strong relationships between meteorological factors and pollutant concentrations (atmospheric pressure: r = 0.62–0.70 with NO₂), providing insights for integrated climate–air quality management strategies. The study demonstrates substantial contributions to Sustainable Development Goals across four dimensions (Environmental Health 30%, Sustainable Cities and Climate Action 25%, Economic Development 25%, and Institutional Development 20%) while providing transferable methodological frameworks for evidence-based policy interventions and environmental monitoring in similar stressed urban environments globally. Full article

The aviation sector significantly contributes to environmental challenges, including global warming and greenhouse gas emissions, due to its reliance on fossil fuels. Fuel cells present a viable alternative to conventional propulsion systems. In the context of light aircraft applications, proton exchange membrane fuel cells (PEMFCs) have recently attracted growing interest as a substitute for internal combustion engines (ICEs). However, their performance is highly sensitive to altitude variations, primarily due to limitations in compressor efficiency and instability in cathode pressure. To address these challenges, this research presents a comprehensive numerical model that couples a PEMFC system with a dynamic air compressor model under altitude-dependent conditions ranging from 0 to 3000 m. Iso-efficiency lines were integrated into the compressor map to evaluate its behavior across varying environmental parameters. The study examines key fuel cell stack characteristics, including voltage, current, and net power output. The results indicate that, as altitude increases, ambient pressure and air density decrease, causing the compressor to work harder to maintain the required compression ratio at the cathode of the fuel cell module. This research provides a detailed prediction of compressor efficiency trends by implementing iso-efficiency lines into the compressor map, contributing to sustainable aviation and aligning with global goals for low-emission energy systems by supporting cleaner propulsion technologies for lightweight aircraft. Full article

As China’s largest peninsula, the Shandong Peninsula faces recurrent threats from both tropical and extratropical cyclone-induced storm surges. Understanding the distinct mechanisms governing these surge types is critical for developing targeted coastal hazard mitigation strategies. This investigation employs the FVCOM-SWAVE coupled wave–current model to conduct numerical simulations and comparative analyses of two 2022 surge events, Typhoon Muifa (tropical) and the “221003” extratropical surge. The results demonstrate that hydrodynamic responses exhibit strong dependence on surge-generating meteorological regimes. Tropical surge dynamics correlate closely with typhoon track geometry, intensity gradients, and asymmetric wind field structures, manifesting rightward-biased energy intensification relative to storm motion. Conversely, extratropical surge variations align with evolving wind-pressure configurations during cold air advection, driven by synoptic-scale atmospheric reorganization. The hydrodynamic environmental response in the sea areas surrounding Jiaodong and Laizhou Bay is particularly pronounced, influenced by the intensity of wind stress on the sea surface, as well as the bathymetry and coastal geometry. Full article

The interaction mechanism of multi-physical fields in a 330 MW tangentially fired boiler is explored by coupling the CFD (computational fluid dynamics) model and the working fluid side hydrodynamic model under steady-state conditions. The research focuses on the flue gas flow field, the hydrodynamic safety of the water wall, the variation of the working fluid parameters and the formation and distribution characteristics of sulfide (SO₂, H₂S) under different steady loads (35%, 50%, 75%, 100% Boiler Maximum Continuous Rating). The results show that under high load, the flue gas attaches to the wall. The overall stagnation differential pressure ratio (1.85–2.07) and reversal differential pressure ratio (1.22–1.30) of the G1 tube group with the lowest heat flux are higher than the safety threshold (1.05), proving reliable operational safety under equilibrium conditions. The temperature distribution of the furnace center obtained by numerical simulation is consistent with the actual situation. The mass fraction of sulfide increases significantly with the increase in load. SO₂ is mainly distributed in the wall area of the middle and upper burners, while H₂S is mainly distributed in the wall area between the secondary air and the main burner. The maximum mass fractions of SO₂ and H₂S at 330 MW are 0.120% and 0.0524%, respectively. It is suggested that a wall-attached air system be added to inhibit the enrichment of corrosive gases. This work may provide theoretical support and engineering guidance for multi-objective optimization design and high temperature corrosion prevention and control of tangentially fired boilers. Full article

The use of supercritical carbon dioxide (SC-CO₂) coiled tubing drilling technology for developing heavy oil and other special reservoirs offers significant advantages, including non-pollution of oil layers, prevention of clay swelling, avoidance of reservoir damage, compact footprint, and enhanced oil recovery, making it a highly promising innovative drilling technology. The thermo-hydraulic coupling characteristics of SC-CO₂ in helical coiled tubes are critical to the design of SC-CO₂ coiled tubing drilling systems. However, existing models often neglect thermal conduction, variable thermophysical properties, and friction-compression coupling effects, leading to significant deviations in the prediction of temperature and pressure variations. Considering heat transmission and fluid dynamics, a coiled tube heat-transfer model which considers varying properties of both pressure and temperature has been developed based on an optimized convective heat-transfer coefficient. Then, the physical parameters of the carbon dioxide in the helical coiled tubing were researched. Results indicated that the temperature change of carbon dioxide in helical coiled tubing was small due to the low temperature difference between the carbon dioxide and the air as well as the existence of an air interlayer and low natural convective heat-transfer efficiency. The drop in pressure of the carbon dioxide increased with increasing coiled tubing length, and the pressure was half that of the conventional drilling fluid in the same condition due to its low viscosity. The density of carbon dioxide in the helical coiled tubing changed from 1078 kg/m³ to 1047 kg/m³ with increasing coiled tubing length under the conditions stated herein, and the carbon dioxide remained liquid throughout the whole process. Full article

The wind loading test serves as a critical validation experiment for the Passive Air-Cooling System (PAS) ACP100. However, it remains unclear how the highly scaled-down experimental setup can accurately account for the influence of the steel shell wall heating conditions on the airflow dynamics within the PAS flow channel. This study employs both numerical simulations and experimental investigations to compare and analyze variations in pressure and temperature within the PAS flow channel under the different heating temperatures of a steel shell wall, considering scenarios with and without environmental wind field effects. The objective is to assess the influence and necessity of heating conditions. In this study, ANSYS Fluent 18.2 was utilized to conduct numerical simulations of the 1:126 scale model of ACP100. Subsequently, the 1:126-scale ACP100 test model was placed on a wind tunnel platform to investigate various experimental conditions. Key parameters, including pressure, temperature, and wind velocity, were meticulously measured at critical locations to obtain detailed insights into the model’s performance under different scenarios. The results indicate that the numerical calculations are consistent with the findings from experimental research. When the environmental wind velocity is 0 m/s, the pressure deviation (∆P_max) at each measurement position within the PAS flow channel, under varying heating wall temperatures of 55.8 °C, 93.5 °C and 126.8 °C, remains below 1.8 Pa. Furthermore, the inlet and outlet pressure difference (∆P_io) is less than 3.9 Pa, which is insufficient to establish natural circulation. Additionally, it was observed that the air temperature increases continuously from the PAS inlet to the top outlet; notably, the air temperature at the top outlet approaches that of the heating wall temperature, nearly reaching equilibrium. When examining the coupling effect of the environmental wind field, it is observed that the pressure difference (∆P_io) between the inlet and top outlet of the PAS flow channel increases significantly. However, the pressure deviation at each measurement position within the PAS flow channel remains within acceptable limits, satisfying ∆P_max < 3 Pa. Furthermore, the temperature deviation (∆T_max ≤ 2.8 °C) at each measuring position in the PAS channel indicates that the influence of the environmental wind field on both pressure and temperature distribution is relatively minor and can be safely neglected. In summary, it can be concluded that when utilizing the ACP100 scaled-down model for research on a PAS wind loading performance test, there is no necessity to establish heating conditions as their effects can be disregarded. Full article

In this study of constructing gross primary production (GPP) based on solar-induced chlorophyll fluorescence (SIF) and analyzing its spatial–temporal characteristics and influencing factors, numerous challenges are encountered, especially in arid regions with fragile ecologies. Coupling SIF with other factors to construct the GPP and elucidating the influencing mechanisms of environmental factors could offer a novel theoretical method for the comprehensive analysis of GPP in arid regions. Therefore, we used the GPP station data from three different ecosystems (grasslands, farmlands, and desert vegetation) as well as the station and satellite data of environmental factors (including photosynthetically active radiation (PAR), a vapor pressure deficit (VPD), the air temperature (Tair), soil temperature (Tsoil), and soil moisture content (SWC)), and combined these with the TROPOMI SIF (RTSIF, generated through the reconstruction of SIF from the Sentinel-5P sensor), whose spatiotemporal precision was improved, the mechanistic light reaction model (MLR model), and different weather conditions. Then, we explored the spatiotemporal characteristics of GPP and its driving factors in local areas of Xinjiang. The results indicated that the intra-annual variation of GPP showed an inverted “U” shape, with the peak from June to July. The spatial attributes were positively correlated with vegetation coverage and sun radiation. Moreover, inverting GPP referred to the process of estimating the GPP of an ecosystem through models and remote sensing data. Based on the MLR model and RTSIF, the inverted GPP could capture more than 80% of the GPP changes in the three ecosystems. Furthermore, in farmland areas, PAR, VPD, Tair, and Tsoil jointly dominate GPP under sunny, cloudy, and overcast conditions. In grassland areas, PAR was the main influencing factor of GPP under all weather conditions. In desert vegetation areas, the dominant influencing factor of GPP was PAR on sunny days, VPD and Tair on cloudy days, and Tair on overcast days. Regarding the spatial correlation, the high spatial correlation between PAR, VPD, Tair, Tsoil, and GPP was observed in regions with dense vegetation coverage and low radiation. Similarly, the strong spatial correlation between SWC and GPP was found in irrigated farmland areas. The characteristics of a low spatial correlation between GPP and environmental factors were the opposite. In addition, it was worth noting that the impact of various environmental factors on GPP in farmland areas was comprehensively expressed based on a linear pattern. However, in grassland and desert vegetation areas, the impact of VPD on GPP was expressed based on a linear pattern, while the impact of other factors was more accurately represented through a non-linear pattern. This study demonstrated that SIF data combined with the MLR model effectively estimated GPP and revealed its spatial patterns and driving factors. These findings may serve as a foundation for developing targeted carbon reduction strategies in arid regions, contributing to improved regional carbon management. Full article

This study seeks to improve the performance of a low-temperature differential free-piston Stirling air conditioner (FPSAC). To achieve this, a novel approach is proposed, which replaces the conventional simple harmonic drive with a multi-harmonic drive. This modification aims to optimize the motion of the driving piston, bringing it closer to the ideal movement pattern. The research involves both thermodynamic and dynamic coupling simulations of the FPSAC, complemented by experimental verification of its key performance parameters. A thermodynamic model for the gas medium, employing a quasi-one-dimensional dynamic approach for compressible fluids, and a nonlinear two-dimensional vibration dynamic model for the solid piston are developed, focusing on the low-temperature differential FPSAC physical model. The finite difference method is employed to numerically simulate the entire system, including the electromagnetic thrust of the multi-harmonic-driven linear oscillating motor, fluid transport equations, and the nonlinear dynamic equations of the power and gas control pistons. Variations in displacement, velocity, and pressure for each control volume at any given time are obtained, along with the indicator and temperature–entropy diagrams after the system stabilizes. The simulation results show that, in cooling mode, assuming no heat loss or mechanical friction, the Stirling cooler operates at a frequency of 80 Hz. Using the COP_sin value for the simple harmonic drive as a baseline, performance is improved by altering the driving method. Under the multi-harmonic drive, the COP_c5 increased by 10.03% and COP_c7 by 14.23%. In heating mode, the COP under the multi-harmonic drive improved by 0.51% for COP_h5 and 2.61% for COP_h7. Performance experiments were conducted on the low-temperature differential FPSAC, and the key parameter test results showed good agreement with the simulation outcomes. The maximum deviation at the trough was found to be less than 2.45%, while at the peak, the maximum error did not exceed 3.61%. When compared to the simple harmonic drive, the application of the multi-harmonic drive significantly enhances the overall efficiency of the FPSAC, demonstrating its superior performance. The simulation analysis and experimental results indicate a significant improvement in the coefficient of performance of the Stirling cooler under the multi-harmonic drive at the same power level, demonstrating that the multi-harmonic drive is an effective approach for enhancing FPSAC performance. Furthermore, it should be noted that the method proposed in this study is applicable to other types of low-temperature differential free-piston Stirling air conditioners. Full article

Unlike traditional free-piston Stirling heat engines or heat pumps, the free piston Stirling air conditioning (FPSAC) is specifically designed for electric vehicle air conditioning under ambient room temperature conditions. In the FPSAC system, the displacer and the power piston are coupled through gas forces, emphasizing the importance of investing the thermodynamic–kinetic coupling characteristics. This study analyzed the damping terms within the dynamic equations of the FPSAC model and solved these equations to reveal system dynamics. By linearizing the working chamber’s pressure, the study examined the machine’s dynamic behavior, presenting solutions for amplitude and phase angle. Derived expressions for the displacement and acceleration of both the power piston and the displacer further support this analysis. The research evaluates the influence of driving force on amplitude and phase angle, alongside the impact of damping coefficients, thereby isolating thermodynamic–dynamic coupling characteristics. Control equations integrating dynamics and thermodynamics were developed, and a comprehensive system model was constructed using MATLAB(2020a)/Simulink to simulate acceleration and displacement variation in the pistons. Key findings include: (1) a positive correlation between driving force and displacer, where increased force leads to higher amplitudes; (2) a frequency of 65 Hz reveals a singularity occurs in displacer amplitude, resulting in system instability; (3) phase angle between pistons reduces to below 10° when the driving force exceeds 150 N; and (4) the power piston’s amplitude decreases with an increase in damping C_1, while changes in damping C₂ primarily affect the displacer’s singularity position around 65 Hz, with higher C₂ values shifting the singularity to lower frequencies. Full article

As an electric multiple unit (EMU) train passes through an extreme tunnel characterized by high altitude, steep gradient, and extended lengths, the pressure waves generated by the train–tunnel aerodynamic coupling combine with the baseline pressure variations within the tunnel. This interaction results in rapid fluctuations and extreme external pressure with higher amplitudes, which are transmitted into the carriage, causing pressure fluctuations that can adversely affect passenger comfort. These waves interact with multiple factors within the carriage, such as air ducts, airtight gaps, carbody deformation, oxygen supply systems, and temperature, creating a highly nonlinear internal pressure transmission system. This study first establishes a single-factor internal pressure fluctuation model. Subsequently, a multi-factor coupled internal pressure fluctuation model is constructed based on the ideal gas polytropic process assumption and the law of mass conservation. The model parameters are corrected and the model’s effectiveness and accuracy are validated using experimental data to predict and summarize the internal pressure variation patterns of the EMU train during dynamic operation in such tunnels, ensuring safe train operation and meeting the pressure comfort requirements of passengers. Finally, to address the challenges of maintaining and regulating multi-physical variable comfort under extreme tunnel conditions, this study investigates the impact of partial oxygen pressure and temperature on pressure fluctuations and comfort. The study finds that higher oxygen pressure and temperature significantly increase internal pressure fluctuation amplitude, with the oxygen supply system contributing 18.11% and temperature 5.74% of total variation. Thus, setting appropriate standards for oxygen supply, temperature, and valve operation is crucial for mitigating internal pressure fluctuations and enhancing safety and comfort. This research provides a theoretical foundation for developing a comprehensive comfort evaluation and regulation system under harsh environments. Full article

The accurate prediction of tire and brake thermomechanical behavior is crucial for various applications in the automotive industry, including vehicle dynamics analysis, racing performance optimization, and driver assistance system development. The temperature of the brakes plays a crucial role in determining the performance of rubber by altering its temperature. This change impacts the rim and the air within the tire, leading to variations in temperature and tire pressure, which consequently affect the vehicle’s overall performance. Traditionally, these components have been modeled separately, neglecting the crucial thermal interaction between them, thereby losing a lot of important information from the outside that influences the tire. This paper presents a novel method that overcomes this limitation by coupling the thermomechanical models of the tire and brake, enabling a more comprehensive understanding of their combined behavior. Therefore, the present work could be an interesting starting point to understand how a control system can be influenced by the thermodynamic of the wheel–brake system. Full article

Diesel engine combustion is dependent mainly on the fuel injection characteristics, particularly the injection pressure and rate, which directly affect the engine efficiency and emissions. Herein, an electrically controlled supercharger is added to a traditional high-pressure common rail system to form an ultrahigh-pressure common rail system. Then, the variations in the spray, combustion, and emission characteristics of a diesel engine with a variable fuel injection rate are analyzed. Moreover, a simulation model for a diesel engine combustion chamber is built and verified by experimental results for numerical analysis. The results reveal that the injection rate can be flexibly adjusted via regulation when the solenoid valves are opened on the electrically controlled supercharger. Specifically, (1) the boot-shaped injection rate has greater potential than the traditional rectangular injection rate in terms of combustion and emission; (2) the main injection advance angle at the boot-shaped injection rate can be properly increased to improve combustion; and (3) the pilot injection quantity and advance angle are strongly coupled with the boot-shaped injection rate, potentially enhancing the mixing efficiency of fuel and air in the cylinder to achieve favorable emission results. This paper provides good guidance for the reliable design and optimization of noble-metal-based diesel engines. Full article

In this study, we present an innovative, fully automated, and digitalized methodology to optimize the energy efficiency and cost effectiveness of Li-ion battery modules. Advancing on from today’s optimization schemes that rely on user experience and other limitations, the mechanical and thermal designs are optimized simultaneously in this study by coupling 3D multi-physical behavior models to multi-objective heuristic optimization algorithms. Heat generation at various loading and ambient conditions are estimated with a physics-based, fractional-order battery cell-level model, which is extrapolated to a module that further accounts for the interconnected cells’ heat transfer phenomena. Several key performance indicators such as the surface temperature increase, the temperature variations on the cells, and heat uniformity within the module are recorded. For the air-cooled study case, the proposed coupled framework performs more than 250 module evaluations in a relatively short time for the whole available electro-thermal-mechanical design space, thereby ensuring global optimal results in the final design. The optimal module design proposed by this method is built in this work, and it is experimentally evaluated with a module composed of 12 series-connected Li-ion NMC/C 43Ah prismatic battery cells. The performance is validated at various conditions, which is achieved by accounting the thermal efficiency and pressure drop with regard to power consumption improvements. The validations presented in this study verify the applicability and overall efficiency of the proposed methodology, as well as paves the way toward better energy and cost-efficient battery systems. Full article

This study focusses on the energy efficiency of compressed air storage tanks (CASTs), which are used as small-scale compressed air energy storage (CAES) and renewable energy sources (RES). The objectives of this study are to develop a mathematical model of the CAST system and its original numerical solutions using experimental parameters that consider polytropic charging and discharging processes, changes in the time of the temperature, flow parameters of the inlet and outlet valves under choked and subsonic conditions, and the characteristics of the air motor. This model is used to select CAST as an energy storage system for compressed air generated by compressors and recycling, as well as an energy source to drive DC generators and a pneumatic propulsion system (PPS). A measuring test rig is built to verify the polytropic pressure and temperature variations during CAST charging and discharging obtained from numerical solutions. The topic of discussion is the functional model of a high-pressure air system (HPAS) that contains a CAST connected to an air motor coupled to a mechanical drive for a DC generator or PPS. Such a system is used in small-scale CASTs, which currently respond to socio-economic demands. The presented CAST energy efficiency indicators are used to justify the storage of compressed air energy on a small scale. Small-scale compressed air storage in CASTs is currently important and relevant due to the balance between peak electricity demand and the development of wind energy, photovoltaics, and other renewable energy sources. Full article

In the recent past, Andhra Pradesh (AP) has experienced increasing trends in surface air mean temperature (SAT at a height of 2 m) because of climate change. In this paper, we attempt to estimate the SAT using the GFDL-ESM2G (Geophysical Fluid Dynamics Laboratory Earth System Model version 2G), available from the Coupled Model Intercomparison Project Phase-5 (CMIP5). This model has a mismatch with the India Meteorological Department (IMD)’s observations during April and May, which are the most heat-prone months in the state. Hence, in addition to the SAT from the model, the present paper considers other parameters, such as mean sea level pressure, surface winds, surface relative humidity, and surface solar radiation downwards, that have influenced the SAT. Since all five meteorological parameters from the GFDL-ESM2G model influence the IMD’s SAT, an artificial neural network (ANN) technique has been used to predict the SAT using the above five meteorological parameters as predictors (input) and the IMD’s SAT as the predictand (output). The model was developed using 1981–2020 data with different time lags, and results were tested for 2021 and 2022 in addition to the random testing conducted for 1981–2020. The statistical parameters between the IMD observations and the ANN estimations using GFDL-ESM2G predictions as input confirm that the SAT can be estimated accurately as described in the analysis section. The analysis conducted for different regions of AP reveals that the diurnal variations of SAT in the IMD observations and the ANN predictions over three regions (North, Central, and South AP) and overall AP compare well, with root mean square error varying between 0.97 °C and 1.33 °C. Thus, the SAT predictions provided in the GFDL-ESM2G model simulations could be improved statistically by using the ANN technique over the AP region. Full article