Compression System Research Articles

Dimensionless thermal performance analysis of a closed isothermal compressed air energy storage system with spray-enhanced heat transfer

The isothermal compressed air energy storage (I-CAES) technology boasts the advantages of high theoretical round-trip efficiency and zero carbon emissions. In order to rapidly and efficiently assess the thermodynamic performance of I-CAES, and addressing the limitations of the overly complex thermodynamic model for spray heat exchanged closed-loop I-CAES (CI-CAES), this paper establishes a dimensionless evaluation model related to container size and initial state a*, spray water quantity b*, start or end spraying time c*, and the ratio of liquid level to droplet velocity u*. The expressions for evaluation indicators such as round-trip efficiency, indicated efficiency, compression exergy efficiency, and expansion exergy efficiency are summarized, revealing the impact patterns of dimensionless numbers on the thermodynamic performance of CI-CAES. The results show that the relative difference in the percentage of air enthalpy change calculated using the real gas model versus the ideal gas model during the expansion stage is 88.26 %. The indicated efficiency and round-trip efficiency of CI-CAES simulated by the real gas model were 88.18 % and 60.51 %, respectively, for the design parameters, and the variable condition operation of the hydrodynamic machinery was the main reason for the lower round-trip efficiency. The larger the values of a* and b*, the closer to the isothermal process, and the greater the effect of b* on the performance of the CI-CAES system compared to the two. When b* is 50, the polytropic indices of the compression and expansion stages reach 1.03 and 1.01, respectively. The round-trip, compression exergy efficiency and expansion exergy efficiency all vary parabolically with c*, suggesting that there is an optimal c* that optimizes the system performance. The change in pressure ratio has a greater effect on round-trip efficiency and on the percentage change in air enthalpy during compression and expansion, and u* has a lesser effect on system performance. The results of the research can provide theoretical guidance for the efficient operation of CI-CAES.

Well-posedness and decay structure of a quantum hydrodynamics system with Bohm potential and linear viscosity

In this paper, a compressible viscous-dispersive Euler system in one space dimension in the context of quantum hydrodynamics is considered. The purpose of this study is twofold. First, it is shown that the system is locally well-posed. For that purpose, the existence of classical solutions which are perturbation of constant states is established. Second, it is proved that in the particular case of subsonic equilibrium states, sufficiently small perturbations decay globally in time. In order to prove this stability property, the linearized system around the subsonic state is examined. Using an appropriately constructed compensating matrix symbol in the Fourier space, it is proved that solutions to the linear system decay globally in time, underlying a dissipative mechanism of regularity gain type. These linear decay estimates, together with the local existence result, imply the global existence and the decay of perturbations to constant subsonic equilibrium states as solutions to the full nonlinear system.

Design and economic analysis of photothermal coupled compressed air energy storage system

Design and economic analysis of photothermal coupled compressed air energy storage system

Study on the effect of spray flow rate on pumped compressed air energy storage system

Study on the effect of spray flow rate on pumped compressed air energy storage system

Comparison of methods for discharging an isochoric compressed air tank in compressed air energy storage systems

Comparison of methods for discharging an isochoric compressed air tank in compressed air energy storage systems

Compressive single-pixel spectral imaging with spatial-spectral modulation optimization via coherence minimization

Compressive spectral imaging (CSI) obtains spatial-spectral information from under-sampled measurements, which solves the contradiction between imaging speed and resolution in conventional scanning-based spectral imaging systems. The spatial-spectral modulation and the corresponding sparse prior in reconstruction algorithm jointly determine the reconstruction quality of CSI systems. In this paper, a compressive single-pixel spectral imaging system with the spatial-spectral modulation and the sparse prior simultaneously optimized by coherence minimization is proposed. By formulating the modulation of the single-pixel spectral imaging system and the sensing coherence in the differentiable matrix notation, the gradients of the modulation and the sparse prior with respect to the sensing coherence are derived for both spatial and spectral dimensions. The spatial-spectral modulation and the sparse prior are optimized via gradient descent to minimize the sensing coherence, for both the decoupled CSI systems with one dimension completely sampled and the coupled CSI system with both spatial-spectral dimensions compressively sampled. For the optimized spatial-spectral modulation, high relative mutual differences in the spectral dimension as well as low redundancy patterns in the spatial dimension are achieved, and by combining with the optimized spatial-spectral sparse prior, the enhancement of 5.7 dB for PSNR compared to the unoptimized system is realized.

Aerodynamic instability evolution of a multi-stage combined compressor

Unstable operating conditions such as surge could cause damage to both aerodynamic performance and structural integrity of a compression system. This paper addresses the critical issue of aerodynamic instability in compressor design, particularly focusing on an axial-centrifugal combined compressor, a widely used yet underexplored configuration. An experimental investigation was conducted on a three-stage axial and one-stage centrifugal compressor (3A1C), using two pipe systems and employing fast-responding transducers to capture the dynamic instability process from choke condition to deep surge. Results reveal that at the design speed, 3A1C enters deep surge directly, whereas at off-design speeds, it experiences rotating stall and mild surge across a wide mass flow range. Some special instability features in the combined compressor can be found in the steady state map and dynamic process. The characteristic curve of the first axial stage keeps a positive slope during the whole mass flow range at an off-design speed. The first stage could work stably on the stall characteristic curve because the centrifugal stage has stronger pressurization and plays a dominant role in global aerodynamic instability. Besides, rotating instability occurs at the first rotor tip and disappears as the back pressure increases, which is also rarely seen in a single-axial compressor. This is also related to the strong pressurization of the centrifugal stage. The findings of this paper will contribute to the understanding of aerodynamic instabilities in combined compressors.

Pain Experience and Image Quality with Curved versus Standard Compression for Breast Cancer Screening Mammography: A Randomized Controlled Trial.

Background A curve-shaped compression paddle could reduce the pain experienced by some women at breast cancer screening. Purpose To compare curved and standard compression systems in terms of pain experience and image quality in mammography screening. Materials and Methods In this randomized controlled trial conducted between October 2021 and February 2022, participants screened at three screening sites in the Netherlands were randomized to either a curved-paddle or sham-paddle group. The sham paddle was a standard paddle that was presented as a new paddle. At a standard screening examination, one additional image was acquired with a curved or sham paddle. Pain was measured on a numerical rating scale (range, 0-10). Participants provided a pain score after compression with the standard and test paddles, resulting in two scores per participant. Differences in pain scores were compared between groups using analysis of covariance, adjusting for pain score after standard-paddle compression. Two radiographers and two radiologists performed unblinded paired comparisons of curved-paddle vs standard-paddle images, using standard image quality criteria (radiographers evaluated 1246 image pairs using 12 criteria; radiologists evaluated 320 image pairs using six criteria). The one-sample Wilcoxon signed-rank test was used to determine if there was a significant preference for either paddle. Results In total, 2499 female participants (mean age, 61.6 years ± 7.1 [SD]) were studied; 1250 in the curved-paddle group and 1249 in the sham-paddle group. The mean pain score decreased by an additional 0.19 points in the curved-paddle group compared with the sham-paddle group (95% CI: 0.09, 0.28; P < .001). In terms of image quality, the observers showed no preference or a preference for the standard paddle. Decreased image contrast (range Bonferroni-corrected P values: P < .001 to P > .99) and visibility of structures were the main concerns for curved-paddle images. Conclusion The use of the curved paddle resulted in a minimal pain reduction during mammography breast compression but image quality was reduced. © RSNA, 2024 Supplemental material is available for this article.

Dynamics of water adsorption on SAPO-34: Comparison of three adsorbent bed configurations of adsorption chillers

Intensification of the adsorption dynamics is a strategic way to make adsorption chillers and heat pumps more competitive with conventional vapour compression systems. This can be achieved by consolidating the adsorbent bed with a heat exchanger to enhance heat transfer. This work investigates the dynamics of water adsorption on a commercial adsorbent SAPO-34 for three bed configurations, namely, a reference bed consisting of a monolayer of loose beads located on an aluminium plate, and two consolidated beds – a monolayer of beads glued to the plate, and a homogeneous coating of the plate prepared with binder. The morphology and texture of the prepared beds were studied by optical and scanning electron microscope techniques as well as by low temperature nitrogen adsorption. Six binders involved, both organic (hydroxyethyl cellulose, polyvinylpyrrolidone, polyaniline) and inorganic (heat-conductive compound CPTD, bentonite clay, colloidal silica sol), produced varying effects. It was found that the most preferred configuration involves SAPO beads glued to the plate with bentonite for which the heat transfer was enhanced by a factor of 1.2–1.7 while maintaining sufficient mass transfer. The effective heat transfer coefficient was measured for the most promising binders and selected configurations, and varied between 120 and 248 W/(m2 K). The heat transfer acceleration permitted the specific cooling power (at a conversion of 0.8) to increase from 2.7 kW/kg for loose beads of 0.8–0.9 mm size to 3.5 kW/kg for the same beads bound with bentonite. Thus, gluing pre-made commercial adsorbent beads with heat-exchanger with suitable binders presents a simple and promising method to enhance the adsorption dynamics, resulting in a more compact design of adsorption chillers.

Cylinder-piston application for surge prevention and energy efficiency in an industrial compression unit

Compressions are prevalent in industrial applications and are notable for their substantial energy consumption. Therefore, the simulation and analysis of the compression process are essential for maintenance and energy conservation efforts. These systems are prone to potentially unstable surge conditions, necessitating the use of traditional anti-surge valves that result in considerable energy losses. Ensuring the near-optimal operation of these systems is critical to minimizing energy consumption.In this article, a conceptual framework for a cylinder-piston mechanism is delineated, intended for design and operation as an active surge control system. Additionally, a modular quasi-one-dimensional model is articulated for the transient simulation of an industrial compression system, which integrates models for both the anti-surge and active control systems. The manuscript presents a novel design, featured by a cylinder-piston system integrated with a robust controller, posited as a potential alternative to traditional anti-surge systems. The effectiveness of this design in expanding the operational envelope of the compression system and surge prevention is rigorously examined. Moreover, a thermodynamic model, grounded in the fundamental laws of mass, momentum, and energy conservation, is applied to each component of the system. Furthermore, the manuscript explores the benefits of the innovative design in achieving a marked decrease in energy wastage. Simulation results from a test scenario reveals that the implementation of the cylinder-piston design, as opposed to the conventional anti-surge system, can diminish energy losses and associated pollutant emissions by approximately 33 percent.

Compressible fluid limit for smooth solutions to the Landau equation

Although the compressible fluid limit of the Boltzmann equation with cutoff has been extensively investigated in Caflisch [Comm. Pure Appl. Math. 33 (1980), 651–666] and Guo, Jang, and Jiang [Comm. Pure Appl. Math. 63 (2010), 337–361], obtaining analogous results in the case of the angular non-cutoff or even in the grazing limit which gives the Landau equation, still remains largely open, essentially due to the velocity diffusion effect of the collision operator such that L^{\infty} estimates are hard to obtain without using Sobolev embeddings. In this paper, we are concerned with the compressible Euler and acoustic limits of the Landau equation for Coulomb potentials in the whole space. Specifically, over any finite time interval where the full compressible Euler system admits a smooth solution around constant states, we construct a unique solution in a high-order weighted Sobolev space for the Landau equation with suitable initial data and also show the uniform estimates independent of the small Knudsen number \varepsilon&gt;0 , yielding the O(\varepsilon) convergence of the Landau solution to the local Maxwellian whose fluid quantities are the given Euler solution. Moreover, the acoustic limit for smooth solutions to the Landau equation in an optimal scaling is also established. For the proof, by using the macro-micro decomposition around local Maxwellians, together with techniques for viscous compressible fluid and properties of Burnett functions, we design an \varepsilon -dependent energy functional to capture the dissipation in the compressible fluid limit with the feature that only the highest-order derivatives are most singular.

Numerical study on efficiency and robustness of wave energy converter-power take-off system for compressed air energy storage

The unpredictable fluctuations of wave lead to an imbalance between energy supply and demand. This article proposes a wave-driven compressed air energy storage system, which uses wave mechanical energy instead of electrical energy as the direct driving force for the compressors. Compressed air energy storage solves the problem of stability of wave energy output by accumulating and storing wave energy and then releasing it in a centralized manner. Due to the significant change in load damping compared to the generator, the damping force of the power take-off with compressed air energy storage load is analyzed. And a robust strategy with adjustable buoy draft and load compressor number is proposed, and the highest capture width ratio of 26.71 % and wave energy to compressed air energy conversion efficiency of 13.00 % are achieved under regular wave conditions. Surface seawater is used for heat supplementation in the expansion phase, and a closed-loop system is designed to avoid the damage of low-temperature condensation, the round-trip efficiency of the system is 11.26 %. This research provides a potential power generation path for wave energy and surface seawater heat. And it may beneficial to provide stable and relatively cheap power supply for coastal and offshore users.

Comparison of dynamic compression system versus multiple cancellous screws in the treatment of femoral neck fractures in young adults

IntroductionFemoral neck fractures have posed a significant global healthcare challenge and had notable impacts on the quality of life. Current treatment strategies for femoral neck fractures in young individuals have varied, emphasizing the need for optimal fixation methods. This study compared the clinical and radiological outcomes of the dynamic compression system (DCS) and multiple cancellous screws (MCS) methods.MethodsThis retrospective study included a total of 275 young adults with fresh femoral neck fractures treated with DCS and MCS. A matching analysis with a 1:1 ratio based on age, gender, fracture classification, and reduction quality was conducted. Demographic data were recorded, and comparisons were made according to follow-up time (FUT), hospitalization period, operation duration, femoral neck shortening, caput-collum-diaphysis (CCD) angle, Harris Hip Score (HHS), and post-operative complications.ResultsA total of 42 fractures were matched with a median age of 42 years (range, 22–48). In the DCS group, vertical neck shortening (median 1.92) was significantly lower than that in the MCS group (median 4.53) (P < 0.05). In the DCS group, horizontal femoral neck shortening, resultant femoral neck shortening, the amount of change in CCD angle, and HHS were 0.57 mm (0.43, 4.74 mm), 1.82 mm (0.40, 3.53 mm), 0.13° (-0.78°, 1.80°), and 91 (85–93), respectively. They were all non-significant than 1.00 mm (0.56, 6.23 mm), 2.74 mm (1.59, 6.71 mm), -0.18° (-1.11°,1.85°), and 91 (75, 93) in the MCS group, respectively (P > 0.05). There was no statistical difference in FUT, hospitalization period, operation time, and post-operative complications at the latest follow-up (P > 0.05). There were no complications such as pulmonary embolism, deep vein thrombosis, and incision infection reported.ConclusionDCS and MCS demonstrated effectiveness in treating femoral neck fractures in young adults. The DCS implant provides additional stability in the vertical axis. A prospective randomized controlled study with a large sample size was needed to validate these findings.

AI-driven automatic compression system for colorectal anastomosis.

Although circular staplers offer technical advancements over traditional hand-sewn techniques, their use remains challenging for unskilled users, necessitating substantial time and experience for mastery. In particular, it is challenging to apply a consistent pressure of an appropriate magnitude. We developed an automated circular anastomosis device using artificial intelligence (AI) to solve this problem. Automation through AI reduces experiential factors during the anastomosis process. We defined damage occurring during the anastomosis process, noting that a greater depth of damage indicated a more severe injury. For automated anastomosis, data at a tissue strain of 40% were used for the AI model, as this strain level showed optimal performance based on the accuracy and cost matrix. We compared the outcomes of automated anastomosis using a trained AI with those of unskilled users. The results were validated using the Shapiro-Wilk test and t tests. Compression damage was verified on collagen sheets. The AI-driven automatic compression system resulted in less damage compared to unskilled users. In particular, a more significant difference in damage was observed in poor-condition collagen than in good-condition collagen. Damage to the collagen under poor conditions was 54.8% when handled by unskilled users, while the AI-driven automatic compression system resulted in 38.9% damage. This study confirmed that novices' use of AI for automated anastomosis reduces the risk of damage, especially for tissues in poor condition.

Thermodynamic and Exergoeconomic Analysis of a Novel Compressed Carbon Dioxide Phase-Change Energy Storage System

As an advanced energy storage technology, the compressed CO2 energy storage system (CCES) has been widely studied for its advantages of high efficiency and low investment cost. However, the current literature has been mainly focused on the TC-CCES and SC-CCES, which operate in high-pressure conditions, increasing investment costs and bringing operation risks. Meanwhile, some studies based on the phase-change CO2 energy storage system also have had the disadvantages of low efficiency and the extra necessity of heat or cooling sources. To overcome the above problems, this paper proposes an innovative compressed CO2 phase-change energy storage system. During the energy charge process, molten salt and water are used to store heat with a smaller temperature difference in heat exchangers, and high-pressure CO2 is reserved in liquid form. During the energy discharge process, throttle expansion is applied to realize the evaporation at room temperature, and CO2 absorbs the reserved heat to improve the power capacity in the turbine and the system energy storage efficiency. The thermodynamic and exergoeconomic studies are performed firstly by using MATLAB. Then, the parametric study based on energy storage efficiency, system unit product cost, and exergy destruction is analyzed. The results show that energy storage efficiency can be improved by lifting liquid CO2 pressure as well as compressor and turbine isentropic efficiencies, and CO2 evaporation pressure has the optimal pressure point. The system unit product cost can be reduced by decreasing liquid CO2 pressure and compressor isentropic efficiency, while CO2 evaporation pressure and turbine isentropic efficiency both have optimal points. Finally, the optimization of two performances is performed by NSGA-II, and they can reach 75.30% and 41.17 $/GJ, respectively. Moreover, the optimal energy storage efficiency is obviously higher than that of other energy storage technologies, indicating the great advantage of the proposed system. This study provides an innovative research method for a new type of large-scale energy storage system.

Off-design behavior investigation of hydrogen blending-fueled compressed air energy storage system

Nowadays, the integration of compressed air energy storage with hydrogen energy is seen as a promising approach to reduce carbon emissions and enhance commercial feasibility. This paper aims to uncover energy conversion mechanisms, comprehend the irreversible loss in components to enhance system performance in the compressed air energy storage system using hydrogen-blended natural gas as fuel. The detailed thermodynamic analysis for the proposed system under off-design condition, considering scenarios with constant and variable turbine inlet pressure modes, is conducted. The research results indicate that adopting a variable turbine inlet pressure mode and increasing the hydrogen blending ratio are beneficial for enhancing system performance. The most superior system can achieve a roundtrip efficiency of 62.28 %, an exergy efficiency of 61.39 %, and an energy density of 7.77 kWh/m3. Increasing the hydrogen blending ratio alleviates the decrease in isentropic efficiency of the turbine, thereby maintaining a higher output power level. The influence of increasing the hydrogen blending ratio on CO2 emissions is significant across various load rates, surpassing the impact of corrected speeds. Additionally, hydrogen blending demonstrates a remarkable enhancement in system performance under high load and corrected speed conditions, particularly in exergy efficiency, with precise percentage increases of ∼1.42 % and ∼1.49 %, respectively.

Performance study of a compressed air energy storage system incorporating abandoned oil wells as air storage tank

With the rapid development of intermittent renewable energy, large-scale compressed air energy storage technology represented by Adiabatic Compressed Air Energy Storage (A-CAES) has attracted much attention. In order to simultaneously solve the problems of reuse of decommissioned oil wells and low efficiency of A-CAES system, a compressed air energy storage system incorporating abandoned oil wells as Air Storage Tank (AST) is proposed in this paper. The system performance of underground Oil Well CAES (OW-CAES), aboveground Steel Pipeline CAES (SP-CAES), and aboveground Storage Tank CAES (ST-CAES) is comparatively analyzed based on a thermodynamic model, focusing on the impact of heat transfer characteristic parameters of the AST wall on the system performance. The results show that recoverable heat and round-trip efficiency are significantly affected by the heat transfer characteristics of the AST wall. More recoverable heat and higher round-trip efficiency can be achieved by increasing the wall temperature and the surface area of the AST, respectively. The round-trip efficiency and energy storage density of the OW-CAES system are higher than those of the ST-CAES system, which are increased by 8.3 % and 18.45 % respectively. This study provides theoretical support for the feasibility of the OW-CAES system and has certain engineering guiding significance.

Research and Implementation of FPGA Image Compression Parallel Algorithm Based on CCSDS

High-pixel, high-resolution spectral images are an important source of key graphical information obtained from space remote sensing, however, with the dramatically expanding amount of graphical information, the limited transmission bandwidth and hardware resources are difficult to meet the demand for massive data, which makes real-time image lossless compression and transmission technology an important solution. For this reason, this paper is based on the CCSDS image lossless compression algorithm, using FPGA for the construction of image compression system, and proposes a method strategy based on parallel acceleration algorithm to realize the real time processing of large-capacity hyperspectral images. The simulation results show that hyperspectral river and mountain range images can be compressed with greatly improved compression efficiency while maintaining real time performance and accuracy.

DESIGN OF A NOVEL DEW POINT INDERECT EVAPORATVE COOLER: PRELIMINARY EXPERIMENTAL INVESTIGATIONS

Evaporative coolers may represent a promising alternative to conventional cooling technologies based on vapor compression systems. Indeed, they present lower production and operative costs, as well as lower environmental impact. The present study aims to develop a novel Dew Point Indirect Evaporative Cooler (DPIEC), by combining simplicity, hence low production costs, and higher cooling performance. The design proposed has mixed flow configuration and is made of polycarbonate plate covered with cotton cloth as wicking material. Two prototypes with different length are experimentally tested for two different water distributors. The performance of the novel DPIEC is evaluated and compared in terms of temperature drop, dew-point effectiveness, cooling capacity and compactness. The results show that the long prototype performs better in terms of temperature drop and dew point effectiveness, but yields lower cooling capacity and is less compact. In addition, it is observed that the distributor that supplies water over the system performs better, independently on the prototype. These results can serve as reference for future designs of mixed-flow DPIEC.

Numerical Investigation of Flow Evolution in Centrifugal Compressors During Surge

Abstract Surge can lead to violent flow fluctuations in the compression system and damage to the blade structures. In this article, a fully three-dimensional numerical model of the centrifugal compressor surge is developed, and the accurate transient flow evolutions in different components during the surge are studied in detail. The results show that in the surge initiation, the pressure distortion caused by the asymmetric geometry of the volute at the diffuser outlet transfers along blade passages to the impeller inlet, which induces two types of stall cells with different rotating speeds and sizes developing independently in two isolated circumferential positions at the impeller inlet. With the surge development, the two types of stall cells come into contact and are mixed, which causes the asymmetric local reverse flow near the casing of the impeller leading edge. Subsequently, the reverse flow extends to the full annuls at the impeller inlet, and the compressor pressure ratio falls abruptly. At the same time, several expansion waves arise in the impeller and travel downstream along the volute and the outlet pipe. As reflected by the nozzle, these expansion waves travel back upstream into the impeller. The findings of this research have great implications for the asymmetric flow control methods, which develop novel asymmetric geometries to counteract the influence of the volute and extend the compressor stable operation range.