Compressed Air Research Articles

Alternative Energy Sources Usable in Automotive Transport

The research focuses on the methodology of preparing a concept and application scenarios for alternative sources of energy in transportation. The ideas and interpretations are not strictly limited to automobile transport but also reach into other areas of using and processing energy. The conceptual approach to the choice of sources, with the aim of securing the efficient use of energy conversion, is illustrated on the model embodiment embedded in a passenger car; the relevant presentation is centered on an experiment focusing on the linear arrangement of a driven electromagnetic generator. This involves generating and collecting energy for not only the accumulation of electrical energy using relatively independent systems, but also for direct use within driving needs. In the modeled example, the supplied energy is assumed to be in a range of constant power from p = 10 W to 50 kW (200 kW). The given example of the design of the choice of energy conversion sources and the use of generators in a passenger car shows the possibilities, limitations, and variants for demonstrating the requirements relating to a simple driving mode. The application of a linear or cylindrical internal combustion engine is considered for a specific set mode of the car. Variants of suitable uses of the accumulated energy in compressed air are proposed. The use of light and thermal forms of energy is considered for additional forms. As an experimental example, the use of generators derived from vibration harvesters is shown. The proposed energy generation arrangement can be controlled and optimized for specific transport tasks. The generation and accumulation of energy can be employed in the form of electrical energy, as kinetic energy for direct use in driving, or to accumulate in compressed air for later use. Solar energy can be used directly or can be accumulated. The combustion unit can serve as a source of kinetic energy or also to store energy for further use. The concept of alternative sources is based on known methods of use in other industries. The model combination of resources and its simple analysis in the concept of resource selection is demonstrated on an example of an application in passenger cars.

A Newly Developed Compressed Air Cannon Test Bench Designed for Multi-Impact Analysis of Composite Structures

Understanding the response and damage evolution of structures subjected to multiple impact events is essential for designing resilient structures capable of withstanding complex loading scenarios, such as impacts from hail, gravel or foreign object debris. This article presents the development and characterization of a novel test bench, the “Compressed air multi-cannon”, designed specifically for studying the multi-impact behavior of composite materials. This test bench offers advantages over traditional impact testing methods by enabling controlled and adjustable impact parameters, including number of impacts, spatial and temporal lag, energy, angle and impactor dimensions. The primary objective of this work is to provide a detailed description of the test bench design, construction, and validation procedures. Key components such as the pressurized air system, projectile launch mechanism, target mounting arrangement, and data acquisition system are discussed. Experimental methodologies for assessing multi-impact response, specimen preparation, instrumentation, and data analysis techniques are outlined. Through a series of single-impact and multi-impact tests, distinctive damage mechanisms and energy absorption characteristics were observed in composite structures, revealing significant differences in how composites respond under single- and multi-impact conditions. It was found that the single-impact configuration remains particularly critical compared to multi-impact configurations with a high number of impacts. However, further testing is required to determine whether this result holds true under varying impact parameters, highlighting the unique value of this machine for exploring new, realistic questions in the literature.

Real-time proof of concept for a hybrid magnetic bearing with improved damping and reduced control complexity

This paper presents a novel Axial Hybrid Magnetic Bearing (AHMB) and its corresponding control approach to overcome the constraints of conventional Active Magnetic Bearings (AMB) and Passive Magnetic Bearings (PMB). The HMB architecture comprises an independent magnetic circuit for the Permanent Magnet (PM) and AMB, resulting in improved damping and reduced control complexity. A Permanent Magnet Actuator Mechanism (PMAM) and its control algorithm were developed to render the HMB system suitable for counteracting diverse loads. Real-time experiments validated the efficacy of the HMB in mitigating external disturbances. Experimental results showed that when the load was added to the AHMB system, the rotor could be regulated to its nominal position within 1.5 s by the AMB. Moreover, the control currents to the AMB coil can be effectively reduced by ≥50%. The proposed hybrid magnetic bearing has potential applications including, but not limited to, cleanroom equipment, high-speed air compressors, high-speed turbomachinery, and flywheel energy storage systems.

Experimental study on disintegration of unsaturated red clay in Ca2+ solution environment

Guilin is a world-famous karst area characterized by a high concentration of Ca2+ in its groundwater. The disintegration of red clay plays a key role in the collapse of soil caves. In order to study the disintegration mechanisms of unsaturated red clay in Ca2+ solution, disintegration tests were conducted using a self-made disintegration apparatus. The soil samples are placed on the sieve plate of the disintegration apparatus, and a tensile meter records the real-time change of samples mass to calculate the disintegration rate. XRD analysis and filter paper method were employed to determine the mineral composition and matric suction of red clay, respectively. The results show that the matric suction decreases with increasing moisture content and increases with the void ratio. When the matric suction exceeds 965 kPa, disintegration is markedly intense, and the disintegration rate shows no significant correlation with Ca2+ concentration. When the matric suction is below than 965 kPa, the disintegration rate increases from 0.057 to 3.027 g/s with the increase of Ca2+ concentration. The disintegration of red clay with high matric suction is primarily attributed to the rapid ingress of water molecules and the compression of air due to matric suction, resulting in tensile stress. The disintegration of red clay with low matric suction is primarily caused by the reduction in the diffusion layer thickness of clay particles and the weakening of interparticle attraction due to Ca2+.

Visualizing filtration: a hands-on model for understanding Starling forces in glomerular filtration rate.

Understanding complex physiological processes is a cornerstone of medical education, and one such fundamental concept is the regulation of the glomerular filtration rate (GFR) by Starling forces. Therefore, developing a physiologically sound educational model to demonstrate these forces can significantly enhance the learning experience for students, providing them with a clear and comprehensive understanding of renal filtration. Starling forces include the glomerular capillary hydrostatic pressure, which drives plasma filtration; the plasma colloid osmotic pressure (also referred to as the oncotic pressure within the capillary), which opposes filtration; and the Bowman's capsule hydrostatic pressure, which resists fluid influx. Bowman's capsule oncotic pressure is typically considered negligible in healthy kidneys and, therefore, does not usually influence the glomerular filtration process. It is crucial for future clinicians to understand these Starling forces in order to monitor and manage kidney function effectively. To aid in understanding these concepts, we present a simple yet effective physical model of GFR. This model uses pressurized air and a serological pipette setup to simulate the filtration process, with a ping-pong ball's height representing GFR. Various perturbations demonstrate changes in Starling forces, allowing students to visualize the impact of different physiological and pathological conditions on GFR. This hands-on approach aims to simplify the complex interplay of factors affecting GFR, making it an invaluable educational tool for medical students.NEW & NOTEWORTHY Physical models enhance the understanding of complex physiological concepts. This Illumination introduces a hands-on model using pressurized air and a serological pipette to simulate glomerular filtration rate (GFR), with a ping-pong ball indicating filtration rate. The model demonstrates how Starling forces, glomerular capillary hydrostatic pressure, plasma colloid osmotic pressure, Bowman's capsule oncotic pressure, and Bowman's capsule hydrostatic pressure, affect GFR, providing a clear and comprehensive learning experience for students.

Experimental evaluation and artificial neural network modeling of heat transfer performance of aerosolized magnesium oxide nanoparticles flow through pipes

This study presents a novel approach to modeling the convective heat transfer coefficient (CHTC) of aerosolized magnesium oxide (MgO) nanoparticles in a circular pipe using artificial neural network (ANN) technique, by leveraging experimental data. The work addresses a gap in existing research on the heat transfer characteristics of nanoaerosols under varying thermal and flow conditions. MgO nanoparticles (30-50 nm) were dispersed in compressed air at volume fractions of 0.005, 0.01, and 0.05 to generate the nanoaerosol. This aerosol was then driven through the pipe at volumetric flow rates between 10 and 50 liters per minute (lpm). The pipe was subjected to controlled heat fluxes of 4546.83 W/m², 9093.66 W/m², and 13640.49 W/m² to evaluate the aerosol heat transfer coefficient (AHTC). Experimental results demonstrated that incorporating MgO nanoparticles significantly enhanced the heat transfer coefficient by up to 1.4 %, 111 %, and 89.7 % at the specified heat flux values, corresponding to increases in the volumetric flow rate from 10 lpm to 50 lpm, respectively. An ANN-based correlation was developed to model the heat transfer coefficient in relation to heat flux, particle volume fraction, and volumetric flow rate. This model accurately predicted the experimental data, achieving a mean absolute percentage error (MAPE) of 9.9 × 10-5, a mean square error (MSE) of 0.038433, and a coefficient of determination (R²) of 0.99. These findings confirm the ANN model's efficacy in predicting the enhancement of the nanoaerosol heat transfer coefficient and provide a robust tool for future thermal management applications involving nanofluids.

Predesign of a Radial Inflow Turbine That Uses Supercritical Methane for a Mid-Scale Thruster for Upper Stage Application

The worldwide concern regarding the harmful effects of old polluting and toxic propellants has led to increased interest in new, green propellants and higher efficiency thrusters. This fact requires that a new generation of turbopumps, fit for these propellants, is developed. This paper focuses on the design of a radial inflow turbine, which was developed to power a single-shaft turbopump system for a 30 kN upper stage expander cycle thruster engine. The objective was to create a high-efficiency, compact, cheap-to-manufacture, 3D-printable turbine suitable to simultaneously power the methane and Oxygen pumps that feed the thruster. The total power consumed by the pumps for which this turbine was designed is 152 kW. The solution proposed in this paper includes measures such as elimination of the bladed diffuser, which was carried out to reduce the weight and the overall dimensions of the turbine. Comparing it with an axial turbine with the same power output, it has lower overall dimensions because it does not require a direction change at the inlet to the turbine bladed components, it does not require a stator to work, and its casing has a conical shape and is not cylindrical like the axial construction one. The proposed design has been analysed by CFD, which revealed that it can power the pumps. Analysis performed in off-design conditions indicated that the turbine has the best efficiency if the rotation speed and mass flow are varied at the same time. A breadboard model of the turbopump for which the turbine in this paper has been designed has been built using plastic and tested at pressures up to 6 bars using compressed air. The results indicate that above 1.5 bars of inlet pressure the turbine can overcome the internal resistances of the components and the rotor starts to spin. No indication of imbalance of the rotor was observed at maximum test pressure. Two configurations of the seals between the turbine and the adjacent pump have been tested, indicating that labyrinth seals must be doubled by floating ring seals.

Optimizing Energy Efficiency and Emission Reduction: Leveraging the Power of Machine Learning in an Integrated Compressed Air Energy Storage-Solid Oxide Fuel Cell System

This research introduces a cutting-edge energy system that combines a solid oxide fuel cell (SOFC) with compressed air energy storage (CAES) to generate compressed air, electrical power, and heat. The system's performance was assessed and enhanced using regression-based machine learning models, concentrating on three main process variables: temperature, current density, and utilization factor. The machine learning models achieved impressive accuracy, with R-squared values greater than 98%, demonstrating their effectiveness in predicting system performance. The results from multi-objective optimization indicated that the ideal conditions for maximizing energy storage, efficiency, and minimizing emissions include a temperature of 973 K, a current density of 6,000 A/m2, and a utilization factor of 0.74. At these optimal parameters, the system reached an energy storage capacity of 28.12 cm3, an efficiency of 64.19%, and emissions of 274.04 kg/MWh. These results underscore the potential of the integrated SOFC-CAES system to tackle significant energy and environmental issues by enhancing energy efficiency, lowering emissions, and offering a sustainable approach to power generation. The findings from this study contribute to the development of hybrid energy systems and facilitate the transition to more sustainable and resilient energy frameworks.

Comparative in vitro toxicity of compositionally distinct thermal spray particulates in human bronchial cells

Thermal spray, in general, is a process that involves forcing a melted substance, such as metal or ceramic in the form of wire or powder, onto the surface of a targeted object to enhance its desired surface properties. In this paper, the melted substance is metal wire generated by an electric arc and forcibly coated on a rotary iron substrate using compressed air. This thermal process is referred to as double-wire arc thermal spray. The particles generated through these methods fall within the nanometer to micrometer agglomerate size range. There is concern regarding potential human health outcomes as these particles exhibit a similarity in particle morphology to welding fumes. Thermal spray wires with zinc (PMET540), iron and chromium (PMET731), and nickel (PMET885) as primary metal compositions were used to generate particulate via an electric arc wire thermal spray generator for exposure to human bronchial cells (BEAS-2B) to examine comparative toxicity ranging from 0-200µg/mL. Resulting cellular viability was assessed through live cell counts, and percent cytotoxicity was measured as a function of LDH release. Oxidative stress, genotoxicity, and alteration in total antioxidant capacity were evaluated through DNA damage (COMET analysis) and antioxidant concentration at 0, 3.125, 25, and 100µg/mL. Protein markers for endothelin-1 (ET-1), interleukin-6 (IL-6), and interleukin-8 (IL-8) were also assessed to determine inflammation and endothelial alteration. Resultsindicate modulation of oxidative stress response in a material and dose dependent manner. PMET540 exhibited the greatest cytotoxic effect between wires and across doses. DNA damage and antioxidant concentration induced by PMET540 were significantly higher than other wires at higher doses (DNA damage increased at 25 and 100µg/mL; Antioxidant concentration increased at 100µg/mL). However, ET-1 concentration significantly increased only after application of 100µg/mL PMET885. IL-6 and IL-8 were most highly expressed in BEAS2B culture after 25µg/mL exposure to PMET540 (99.4% Zn). This data suggests that metal composition of thermal spray wires dictates the diverse response in human bronchial cells.

Investigating the thermal performance of a subsea liquid piston air compressor pipeline operating at very high pressure ratios

Abstract Liquid piston air compression is presently gaining significant interest as a means for long duration energy storage at large scale. However, various aspects attributed to the thermal performance of liquid piston air compressors at high operating pressure ratios remain yet unanswered. This paper presents a transient thermal analysis of a novel, subsea liquid piston air compressor pipeline operating at pressure ratios up to 200. A thermal model implementing different empirical correlations for the convective heat transfer phenomena is presented. The study reveals a major knowledge gap in terms of Nusselt number correlations available to define the internal heat transfer coefficients explicit to liquid piston pipelines. Results from a parametric study suggest that the internal heat transfer inside a liquid piston having a very large length-to-diameter ratio was characterised by natural convection effects. Furthermore, it was found that to attain a thermal efficiency higher than 0.90, the power density had to be limited to not more that 0.22 kW/m3, with a compression time required per stroke being at least 25minutes.

Optimization of laser engraving labeling conditions using response surface methodology and its impact on quality characteristics of dragon fruit (Hylocereus undatus) peels

Establishing a traceability system ensures safety and improves food quality and transparency. A reliable traceability system is in high demand, especially for fresh produce like fruits and vegetables to control various food-borne outbreaks. They are conventionally labeled with plastic/paper stickers, which are not reliable, as they are easy to remove and counterfeit. Laser engraving is a novel technology that provides anti-counterfeiting and ecologically friendly labels. In the current study, a laser system was optimized for etching alphanumeric codes on dragon fruit peel. The input variables for laser engraving were input power (14.3–18.2 W), air compressor pressure (2.8–5.6 kPa) and marking speed (30–200 mm/s), and the response variables involving visibility of mark, depth of penetration, damage to the skin and shrinkage of the peel have been investigated. At the optimized conditions of 15.39 W input power, 3.27 kPa compressor pressure, and 161 mm/s marking speed, the label was clearly visible with 0.31 mm depth of penetration, 2.28 kPa skin strength, 0.22 % weight loss and 1.5 % shrinkage in macroscopic volume. Laser marking reached only 15 % depth, affecting 8 % of the total surface area and not even impacting the edible pulp portion of dragon fruit. The phytochemical and FTIR analysis showed no substantial effect on the laser-treated peel.

A decoupling control of air supply for the PEM fuel cell with slide mode-active disturbance rejection controller

The air supply subsystem is crucial for optimizing proton exchange membrane fuel cells (PEMFCs). This study develops a transient model for the air subsystem and proposes a control strategy that decouples air pressure and flow using sliding mode-active disturbance rejection control (SM-ADRC). In this study, adjustments to the air compressor speed and the opening of the back-pressure valve are utilized to achieve this control strategy. The sliding mode-extended state observer (SM-ESO) is employed to estimate and compensate for uncertainties within the system, while the sliding mode-nonlinear state error feedback (SM-NLSEF) is used to simultaneously control air flow and pressure. The study evaluates the performance of the SM-ADRC controller across various scenarios and environmental pressures. Evaluations show that the SM-ADRC controller significantly outperforms traditional methods like Fuzzy-ADRC, ADRC, SMC, and PID, with overshoot reductions of 18.2%, 34.1%, 42.5%, and 63.7%, respectively, and adjustment time under 1 s. Additionally, SM-ADRC achieves a 4.1% and 1.8% improvement in efficiency compared to PID and ADRC.

Investigating the thermal performance of a pipe-encapsulated movable PCM wall and its impact on reducing indoor heat gain during summer

The utilization of phase change materials (PCM) in building envelopes is considered to be an effective technology for reducing energy consumption during building operations. In this study, a novel approach is presented for integrating PCM into walls by encapsulating it using pipes, allowing for its mobility through the use of compressed air. Four experimentally validated thermal models, pipe-encapsulated movable PCM (PEM-PCM) wall (Model 1), wall with PCM fixed to the exterior (Model 2), wall with PCM fixed to the interior (Model 3), and wall without PCM (Model 4), were proposed to compare their energy efficiency in summer. Different upper threshold limits (Ttr,up) and lower threshold limits (Ttr,low) were employed to explore the impact of various threshold combinations control strategies on the thermal performance of the wall. The results show that the most effective operating scheme is Ttr,up of 27 °C and Ttr,low of 25 °C. In terms of long-term operation, cumulative summer indoor heat gain of Model 1 is 10.65 %, 10.85 % and 11.4% lower than that of Model 2,3 and 4. Notably, September demonstrates the greatest potential for energy savings, with Model 1 reducing the monthly cumulative indoor heat gain by 54.12% compared to Model 4.

Gas storage in low-permeability rocks

Low-permeability, dense sandstone formations are ideal for underground gas storage in compressed air energy storage. To examine the gas permeability of fine sandstone under high pressure, a self-developed triaxial high-pressure gas permeameter was used for experiments under varying confining and axial pressures. The study identified unsteady seepage variations and stress dependence in porous media represented by fine sandstone and developed a gas leakage model. Results indicate that the seepage process includes rapid, slow, and cessation stages. Fine sandstone shows excellent storage capacity, with a daily leakage rate of 0.0463%, below required thresholds. This study guides high-pressure gas permeability theories and modeling.

The performance analysis of a compressed air energy storage (CAES) for peak moving with cooling, Heating, and power production

This study focuses on modeling and optimizing a multifaceted geothermal-based energy production system within the context of Denmark. The primary objectives revolve around enhancing system efficiency and reducing operational costs. The system under investigation comprises geothermal components, an organic Rankine cycle, a compressed air energy storage facility, and an absorption chiller. The organic Rankine cycle operates using refrigerants R123 and ammonia, effectively converting thermal energy into electricity and thermal energy for various applications. Optimization was carried out employing the Response Surface Method in tandem with Design-Expert software, facilitating the fine-tuning of objective functions. Two key objectives were selected: Exergy Round Trip Efficiency and cost rate, aimed at improving technical performance and curbing economic expenditure. A range of design variables were considered for optimization, including turbine and pump inlet temperatures, geothermal mass flow rate, turbine and pump efficiencies, compressor and gas turbine efficiency, inlet pressure to the compressed air energy storage tank, and evaporator pinch point temperature. The system reached an impressive exergy efficiency peak of 77.98%, accompanied by a modest cost rate of 5.48 $/h. The costliest components in the system were the compressed air energy storage unit, followed closely by organic Rankine cycle 1 and organic Rankine cycle 2. In contemplating the practical implementation of this innovative energy system, ten cities in Denmark underwent rigorous analysis, accounting for technical and economic factors. Subsequent assessments identified Aarhus as the optimal location to initiate the system. The environmental results showed that by producing 13981.9 megawatts of electricity annually in Arhus City, it is possible to help reduce CO2 emissions by 2853.2 tons of CO2/year and avoid environmental costs of 68455.3 $/year. The environmental assessment also highlighted the potential for substantial green space expansion, estimating an additional 13 hectares of green areas in the city of Aarhus, Denmark.

Experimental validation of the design and control of a compressed air energy storage system

Experimental validation of the design and control of a compressed air energy storage system

Thermodynamic and Economic Analysis of a Trigenerative Adiabatic Compressed Air Energy Storage

Abstract Energy storage is indispensable for decarbonising power systems with high penetration of fluctuating renewable generation (e.g., wind, solar). In this study, an innovative trigeneration adiabatic compressed air energy storage (Tri-ACAES) system that produces heating, cooling, and electricity is proposed. The Tri-ACAES system can absorb more wind power than an ACAES system. The Tri-ACAES can work in heating and cooling mode when renewable generation is too low to charge the ACAES system due to the off-design characteristics of the compressor. The results reveal that the round-trip efficiency and turbine power output of the proposed Tri-ACAES system are enhanced by up to 5.8% and 33%, respectively than conventional ACAES system. Further, the proposed system reduced the cost of thermal energy storage by up to 60% than conventional ACAES system.

Experimental Analysis and Cost Assessment of a Novel Variable-Volume Air Storage Device Designed for Compressed Air Energy Storage

One significant reason limiting the widespread application of compressed air energy storage is the high cost of ground-level air storage devices. Previous work by the authors’ team proposed a novel variable-volume air storage (VVAS) device based on working fluid phase change, effectively increasing the air storage capacity. However, the early study only focused on thermodynamic performance analysis. Therefore, this study established an experimental platform for the VVAS device to test its feasibility and developed a cost assessment model to analyze its economic performance. The results demonstrate that the VVAS device allows the air in the storage tank to continue near-isobaric release under the displacement of gaseous R134a at the other side of the bladder when the air pressure in the storage tank decreases to equal the air pressure at the throttle valve outlet. The effective air storage density of the VVAS device can be increased by over 50% under the different air storage pressures. The efficient utilization of the air storage device can significantly reduce its volume and lower storage costs. The cost analysis indicates that the unit air storage cost for the VVAS device is 50.20 $/kg, which is significantly lower than the conventional device (80.34 $/kg).

Comparing the Pressure Containment Requirements of Three Subsea Hydro-Pneumatic Energy Storage Concepts

Abstract Hydro-pneumatic energy storage has significant potential for being deployed subsea and co-located with offshore wind farms. The pressure containment storing the compressed air is the bulkiest and most expensive component of such a storage technology. This paper evaluates three different subsea hydro-pneumatic energy storage concepts, comparing their volumetric storage densities, the steel and concrete anchoring requirements and cost of the pressure containment. The pressure variation experienced by the pressure containment across the storage cycle for the three variants, which would impact the efficiency of energy conversion machinery, is also compared. It is shown that having separate accumulators, each designed for a different operating pressure, offers the potential of reducing the cost of the pressure containment by up to 40% as compared to that for the simple concept having a single accumulator. A novel approach is presented to achieve such cost reduction without constraining the energy conversion machinery to operate over a wider operating pressure range.

Quantification of air compressibility on large wind turbine blades using Computational Fluid Dynamics

Quantification of air compressibility on large wind turbine blades using Computational Fluid Dynamics