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In regions characterized by high temperature gradients, vapor compression systems often necessitate operation at very high pressure ratios resulting in a reduction in system capacity. Economized vapor injection compressors are used to avoid these issues, yet a precise predictive map for various compressor technologies with minimal data and relatively better performance remains unclear. This paper establishes a black-box compressor model to accurately predict compressor power, injection mass ratio, and evaporator mass flow rate in compressors with a single vapor injection port. This model is compared against three legacy models from literature and the ANN model, for reference. All five models are evaluated based on their ability to predict the aforementioned metrics. The proposed black-box model can predict the relevant metrics all within 5 % Mean Absolute Percentage Error (MAPE). Additionally, a refrigerant sensitivity analysis is performed with the black-box models. The model is trained using data from R410A and then used the coefficients to predict the performance of the same compressor when using R454B, and vice versa. It can estimate the evaporator mass flow rate with an accuracy within 3 %, the power within 2 %, and the injection mass ratio with MAPE less than 3 %. [ABSTRACT FROM AUTHOR]

Under off-design conditions, scroll compressors can lead to reduced efficiency, motor damage, and even cause safety problems such as leaks or explosions. To solve the above problems, this paper analyzes the influence mechanism of different voltages on the spectrum of pressure pulsation signal and modulation signal and provides theoretical support for fault diagnosis and enhances the interpretability of the model. A voltage fault diagnosis method of scroll compressor based on Time-frequency Principal component Convolutional Network (TPCN) model is proposed. By demodulation analysis of the pressure pulsation signal of the low-pressure inlet and high-pressure outlet of the refrigerant in the scroll compressor, the spectrum information of the principal component modulation signal under different voltages is obtained. The pooling strategy is used to accurately identify and extract the fault information in the modulated signal spectrum as the input data of the model. The input data is divided into the training set and the test set according to the ratio of 8:2 to complete the training and testing of the fault diagnosis model. The experimental results show that the accuracy of TPCN model for the diagnosis of 5 types of faults reaches 100 %. The average accuracy of the model is 100 %, which indicates that the model has good stability. [ABSTRACT FROM AUTHOR]

• The dynamic model of the combined algebraic spiral scroll compressor was developed. • Discrete green's theorem method can accurately calculate the working chamber volume. • The influence of various parameters on the dynamic characteristics was analyzed. The combined algebraic spiral (CAS) effectively maximizes the geometric performance of a scroll compressor; however, its dynamic behavior remains inadequately explored. Utilizing the geometric model of the CAS scroll compressor, this study derived the functional relationship between the meshing point and the rotation angle, and calculated the working chamber volume using the discrete Green's theorem method. A dynamic model of the CAS scroll compressor was developed, and the influence of various parameters on its dynamic characteristics was analyzed. The findings indicate that when the polar angle interval is <0.01π, the discrete Green's theorem method accurately computes the working chamber volume. Among the gas forces acting on the CAS scroll compressor, the axial gas force is the most significant, followed by the tangential gas force, while the radial gas force is considerably smaller. The tangential gas force predominantly influences the overturning and rotational moments. Notably, when the polar angles of the connection points between the higher-order curve and the starting and ending algebraic spirals are set at 1.5π and 3π, the gas force remains low while maintaining geometric performance. This configuration results in reduced variation in gas force and enhanced dynamic performance. The spiral coefficient and spiral index of the starting algebraic spiral should be set as intermediate values to ensure optimal geometric and dynamic performance of the CAS scroll compressor. [ABSTRACT FROM AUTHOR]

The self-lubricating linear compressor with aerostatic bearings has good prospect for the scenario which has difficulties of oil returning. This study presents a novel oil-free linear compressor and establishes a frictional damping model by using equivalent circuit approach to evaluate the mechanical performance of the compressor. The changes in friction damping characteristics of VISLLC under different piston strokes and injection pressure are analyzed. The flow resistance coefficients within the porous medium and gas gap are obtained by experimental tests and modeling analysis. Simulation results indicate that the equivalent frictional damping coefficient can be reduced by 36.1 % comparing with that of the non-injection and the efficiency can improved the by 17.2 %. The frictional damping coefficient in the porous bearing thickness of 0.9 mm at 600 kPa injection pressure is 3.64 N·s·m−1. [ABSTRACT FROM AUTHOR]

Approximate Computing (AC) have widely adopted in designing large-scale logic circuits. In particular, approximate adder and multiplier circuits have been considerably targeted in the realm of image processing due to their high energy-saving while preserving proper level of computing accuracy. Nevertheless, intensive research and development are maintained in the means of seeking more matured designs that effectively prioritize design overheads over error resilience. In this paper, low error-distance approximate 4:2 compressor circuits are proposed to construct high-speed approximate adders. The developed compressors realize high logic computing and incur competitive area and power consumption, and therefore, they were leveraged to configure an approximate 8×8 multiplier designs. To achieve a favorable trade-off between computational accuracy and hardware resource usage, we develop a simulation framework that evaluates the accuracy of the proposed multiplier designs at the gate-level (measuring error distance) and at the application-level (evaluating SNR and SSIM) of an image. The framework truncates specific propagated carry bits, i.e., least significant bits (LSBs), to realize profitable area- and power-saving. Furthermore, two main high-speed multiplier designs are proposed herein, namely High Computing Performance Approximate Multiplier (HCP-AMUL) and HCP Low Error Approximate Multiplier (HCPLE-AMUL). Matlab R2022b along with VS Code are used for running simulations and accuracy evaluation, while Vivado 2018.2 is utilized for HDL reconfigurable logic design and implementation and evaluation of area, power, and speed, configured on an FPGA Xilinx Nexys 4 Artix-7 (XC7A100T1CSG324) trainer board. The experimental results demonstrate the efficacy of the developed multipliers as the developed HCPLE-AMUL delivers 54.26%, 11.72%, and 449.85 of speedup, power saving, and Power-Delay-AreaError-Product (PDAEP) improvement, respectively. On the other hand, the presented HCP-AMUL realizes an improved saving of area and power at the expense of an acceptable lowering of computation accuracy. It achieves 9.66%, 505.40, and 53.73% of power saving, PDAEP, and speedup respectively, Thus, the proposed compressor and multiplier circuits potentially can be promising approximate computing modules for image processing applications to provide improved trade-off between computation accuracy and logic utilization complexity. [ABSTRACT FROM AUTHOR]

ABSTRACT To address the discrepancy between the steam parameters extracted by pure condensing units/combined heat and power units and those required by users, this paper introduces the design of a steam screw pressure matcher(SSPM) and determines its optimal steam supply scheme. The SSPM primarily comprises a twin‐screw expander (TSE), twin‐screw compressor(TSC), electric motor, and generator. Initially, models were developed for a 300‐MW subcritical intermediate reheat condensing steam turbine unit, an SSPM, and a desuperheater and pressure reducer(DPR). Subsequently, these models are incorporated into the Ebsilon Professional software to simulate the operational characteristics of the SSPM. The performance parameters of the two options are then compared and analyzed. Simulation results reveal that the operational characteristics of the SSPM closely correlate with the mass flow rate of the TSE. As the TSE mass flow rate varies from 47 to 91 t/h, the efficiency of the TSE declines from 66.3% to 65.3%, while the power performed by the SSPM increases from −2457.978 to 1558.469 kW. Under identical operating conditions, the SSPM scheme exhibits a 6.2%–12.4% improvement in efficiency compared to the DPR scheme. Building upon the aforementioned analysis, the SSPM demonstrates effective cascade utilization of heat steam energy and exhibits favorable regulation characteristics under variable operating conditions. Contrasted with traditional DPR, the SSPM notably mitigates constraints on steam extraction by boilers and enhances the maximum generation efficiency of a single unit. [ABSTRACT FROM AUTHOR]

This article focuses on a 300MPa ultra-high pressure liquid driven piston compressor, redesigning it with a liquid sealing structure that utilizes glycerol (C3H8O3) as the sealing liquid. A grate structure is employed to depressurize the sealing liquid in the middle, enhancing the piston sealing life and the sealing effectiveness. CFD simulations were conducted to analyze the flow field of the circulating sealing liquid and to determine the pressure distribution and circulating flow rate. The pressure reduction effect of the grate teeth was numerically simulated, considering parameters such as tooth width, tooth height, spacing, and tooth number. The pressure reduction effect of the grate teeth was numerically simulated, considering parameters such as tooth width, tooth height, spacing, and tooth number. The optimized geometric parameters of the grate teeth, as indicated by the CFD simulation, ensure that the seal design meets the design requirements, offering theoretical guidance for selecting seals in ultra-high pressure liquid driven piston compressors. [ABSTRACT FROM AUTHOR]

Aerodynamic optimization is an effective technology to improve the performance of turbomachinery. Traditional aerodynamic optimizations often focus on blade profiles and neglect the interactions between the blade and end wall, which may lead to suboptimal optimization result. To address this challenge, this study introduces an integrated optimization framework to simultaneously optimize both the blade and hub end wall aerodynamic shape. A hierarchical free form deformation (FFD) technique is employed to achieve integrated parameterization of the blade and hub, with a total of 580 design variables. To ensure efficient optimization with such a high-dimensional problem, the discrete adjoint method is used, which makes the optimization cycle less than one day. Under the framework, the blade optimization and integrated optimization of a typical compressor fan, rotor37, are conducted. With strict constraints on flow rate and total pressure ratio, the integrated optimization achieves a 2.85% improvement in isentropic efficiency—about 0.6% higher than blade optimization. The flow control mechanisms of two optimization approaches are compared, revealing that both blade optimization and integrated optimization effectively modify the blade profile to weaken the shock wave. Furthermore, by modifying the hub aerodynamic shape to improves the flow structure near the end wall, integrated optimization it is more efficient in turbomachinery aerodynamic optimization. [ABSTRACT FROM AUTHOR]

As a critical component of the variable cycle engine (VCE), the variable cycle core compression system (VCCCS) necessitates exceptional performance stability across a wide range of operating conditions. This research delves into the effects of varying the angles of variable inlet guide vanes (VIGV) on the thermodynamic characteristics and internal flow structure of the VCCCS under wide-range operational adjustments. The results reveal that modulating the VIGV significantly broadens the operating envelope of the VCCCS, extending the range of stable and efficient operation from a single curve to a surface. Moreover, adjusting the VIGV reconfigures the load distribution among VCCCS components, consequently altering the internal flow structure. The relationship between aerodynamic losses and entropy distribution in VCCCS components at different VIGV angles has been clarified. Closing the VIGV reduces the secondary flow losses and the extent of high-entropy regions within the core driven fan stage (CDFS) passage, while having a relatively minor impact on the losses in the high-pressure compressor (HPC). The evolution of the feasible domain of the bypass ratio and the mechanisms of adjustment limitation are uncovered. Notably, when the VIGV is adjusted from −20° to 50°, the sources of flow instability within the VCCCS under extreme boundary conditions exhibit three distinct changes. Additionally, a correlation has been established between the VIGV configurations and the thermodynamic characteristics of the VCCCS, thereby providing valuable insights for the design of efficient operation across a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

Parameterized optimization methods are effective approaches for achieving high aerodynamic performance in compressors. Traditional parameterized optimization methods rely on a designer's preselected control parameter layout (including control frame orientation, point density distribution, control point displacement direction, number of variables, and variable ranges), which are purely based on empirical knowledge without sufficient theoretical basis. This paper selects the free-form deformation (FFD) method and Bayesian algorithm as the parameterization method and optimization algorithm for compressor airfoil optimization and studies the influence of FFD control parameter layouts on aerodynamic optimization performance. Additionally, an adaptive optimization method for control parameters based on FFD is proposed, where the orientation and density of the control framework can be incorporated as variables into the control parameters. During the optimization process, the range of design variables is adaptively expanded. A comparison between FFD optimization results based on B-spline and Bernstein basis functions shows that the former achieves an average performance improvement of 4% relative to the latter. Furthermore, an optimization method with an infinitely expandable boundary based on Bernstein basis FFD is proposed, which improves the performance by 12% compared to general adaptive boundary expansion methods. [ABSTRACT FROM AUTHOR]

We conduct experimental investigations of the effect of the tip air injection as a stability control method on a low-speed axial-flow compressor experiencing severe circumferential total pressure distortion. Eight Coanda-shaped injectors, uniformly distributed upstream of the rotor blade leading edge, were employed to counteract stall margin degradation caused by a flat-baffle circumferential distortion. Unsteady pressure data from the tip clearance and rotor wake regions were captured using time-resolved sensors and probes and analyzed through time-frequency transformation and proper orthogonal decomposition (POD) techniques. POD investigation under distorted inflow conditions reveals that the third-order POD mode, which characterizes unsteady tip leakage flow (TLF), plays a dominant role in triggering stall. Based on this insight, tip air injection with varying momentum ratios was applied to enhance the stall margin. The positive correlation between the injected momentum ratio and stall margin improvement was established, demonstrating the stabilizing effect of tip air injection under the circumferential distortion. The results indicate that tip air injection primarily acts on the rotor blade tip region to suppress the unsteady TLF at the center and downstream areas of the distortion, leading to an increase in tip blade load and a reduction in both the scale and number of pre-stall disturbances. However, the injection has a minimal impact on the unsteady TLF frequency band in the rotor wake region. Additionally, the POD analysis confirms that as the injection rate is increased, the energy percentage, flow field intensity, and power spectral density amplitude of the third-order POD mode are decreased, further reflecting the mitigation of unsteady TLF. The present work provides important insight into the stability control mechanisms of a tip air injection under circumferential distortion, offering design guidance for the implementation of active stability control strategies in axial-flow compressors. [ABSTRACT FROM AUTHOR]

Casing treatments are extensively utilized in engineering to significantly enhance stability. The impedance boundary-controlled casing treatment (IBCCT), based on a three-dimensional compressible stability model, is one of the examples and has demonstrated a notable stall margin improvement in a series of extensive experiments. However, the impedance model employed to characterize the perforated plates in IBCCT falls short in considering complex geometric parameters, such as dimensionless thickness and perforation edge angle. With an aim to optimize geometric parameters, the impedance of perforated plates with different vena contracta is determined by appropriate boundary conditions within an acoustic resistance model in this study. These impedance values are integrated with previous models to perform sensitivity analysis. The appropriate cross-sectional profiles for perforation are designed to achieve the desired adjustment of different vena contracta. IBCCTs with different vena contracta are subjected to experimental validation to substantiate the predictions. The results of both the experiments and the sensitivity analysis indicate that the stall margin improvement of IBCCTs increases as the vena contracta decreases. In addition, single-passage numerical simulations are performed under casing treatment conditions to determine whether the IBCCT with varying vena contracta intensifies the impact on the steady flow field. By integrating sensitivity analysis, experimental data, and numerical simulations, the impact of vena contracta on the stability enhancement performance of IBCCTs can be elucidated. [ABSTRACT FROM AUTHOR]

Precise information about the oil discharge rate (ODR) of a compressor and the oil retention rate (ORR) in the oil sump is essential for compressor design, development, and operation. An extended two-fluid model (E–TFM) is developed to study the complicated refrigerant vapor–lubricating oil two-phase flow inside a compressor. Gas–liquid bubbly, droplet, and well-mixed flows are defined on the local cell scale in the E–TFM. Numerical simulations are conducted to investigate the oil–vapor flow field and predict the ODR and ORR of a scroll compressor. The ODR predictions given by the volume-of-fluid method, the conventional Euler–Euler model, and the E–TFM are compared and validated against available measured data. The results confirm the reliability and applicability of the E–TFM. Most oil droplets escaping from the discharge pipe are found to originate from the newly generated droplets via stripping and breakage of the down-flowing thin oil film in the middle cavity. The droplet diameter significantly influences the predicted ODR, whereas the termination criterion for gas–liquid bubbly flow has little effect on the predicted ODR or flow field over the range considered in this study. To improve the ODR prediction performance of E–TFM, efforts should be made to implement a population balance equation to capture the droplet size. [ABSTRACT FROM AUTHOR]

In this study, a fish scale structure with low viscous drag was proposed and applied to the suction surface of a compressor cascade to reduce total pressure loss and suppress corner separation, a key source of compressor inefficiency. By using CFD simulations, the biomimetic structure was identified and integrated into the cascade design. To evaluate its effects, we analyzed secondary flow structures using 2D projected streamlines, axial velocity density (AVD), and vortex visualization techniques. The results show that the fish scale structure effectively reduces the volume of low-energy fluid by 18.36% and decreases total pressure loss at the outlet by 3.5%. Additionally, the AVD iso-surface proved instrumental in identifying low-energy fluid regions, which correlate closely with total pressure loss distribution. These findings highlight the potential of biomimetic-inspired designs to improve compressor performance by mitigating corner separation and reducing flow losses. [ABSTRACT FROM AUTHOR]

Transient gas network simulations can significantly assist in design and operational aspects of gas networks. Models used in these simulations require a detailed framework integrating various models of the network constituents ‐ pipes and compressor stations among others. In this context, the port‐Hamiltonian modelling framework provides an energy‐based modelling approach with a port‐based coupling mechanism. This study investigates developing compressor models in an integrated isothermal port‐Hamiltonian model for gas networks. Four different models of compressors are considered and their inclusion in a larger network model is detailed. A numerical implementation for a simple test case is provided to confirm the validity of the proposed model and to highlight their differences. [ABSTRACT FROM AUTHOR]

The micro-refrigeration system can be utilized in various fields, including personal cooling, medical applications, and other specialized fields. Compressors represent a crucial component of vapor compression refrigeration systems. A simulation model of the micro scroll compressor has been developed. The operating characteristics and leakage of scroll compressors with different capacities (10, 50, 100 cm3/rev) are compared. The effects of rotational speeds, condensing temperature, volume ratios, and clearance on the characteristics of micro scroll compressors have been analyzed. For the scroll compressor that has a suction capacity of 10 cm3/rev, the volumetric and isentropic efficiencies tend to initially rise and subsequently decrease as the rotational speed is raised. The volumetric efficiency reaches a maximum value of 86.26% at 5000 rpm, while the isentropic efficiency reaches a maximum value of 72.93% at 6000 rpm. As the volume ratio increases from 0.79 to 1.0 of the theoretical volume ratios, the volumetric efficiency remains stable, while The isentropic efficiency demonstrates a pattern of initially rising and then falling, reaching a peak of 71.63% at a volume ratio of 0.91 compared to the theoretical volume ratios. [ABSTRACT FROM AUTHOR]

Over-compression of scroll compressor in variable refrigerant flow (VRF) system is a common problem in improving system efficiency because it operates in part load conditions for most of the year. By introducing intermediate discharge valves (IDVs) to allow gas bypass from compression chamber to discharge side during compression process, the over-compression loss can be eliminated. In this study, the characteristics of compression process in IDV compressor are analysed and the effects of IDV port location and port size on compressor efficiency are discussed based on the validated high fidelity scroll compressor model. It is found that the IDVs could be able to adjust gas bypass process in different compression ratio conditions and maintain high efficiency over wider compression ratio range than that of non-IDV compressor. In addition, the VRF system model is integrated to verify the system performance improvement by IDV compressor. It is found that VRF system performance is significantly improved in cooling conditions with the IEER enhanced by 23.9 %, while limited improvement is obtained in heating conditions as the operating compression ratios are relatively higher. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the effects of a decreasing refrigerant charge on the performance and operating conditions of an R513A water-to-water heat pump equipped with a large liquid receiver, an electronic expansion valve, and a vapor accumulator at the compressor inlet. The mass of the refrigerant inside the machine is progressively extracted to simulate refrigerant leakages occurring during the normal operation or in case of failures. The results show that the subcooling is the parameter mostly affected by a refrigerant charge variation since it rapidly collapses to 0 K with the charge reduction. Furthermore, it is possible to identify three different zones in which almost all the properties analyzed (COP, heating capacity, operating pressures and expansion valve opening) exhibit peculiar trends with the charge decrease: subcooling sensitivity zone, constant parameters zone, and compressor failure risk zone. The extension of these zones is determined by the size of the liquid receiver which is installed in the system and, for the heat pump under consideration, is between 100% and 95% of the initial charge for the first zone, between 95% and 40% for the second zone, and below 40% for the third zone. [ABSTRACT FROM AUTHOR]

Due to long lifetime, low level vibration and negligible electromagnetic interference, the Joule-Thomson (JT) cryocooler working at liquid helium temperature has been used in space. However, its cooling capacity and thermodynamic efficiency still need to be further improved under a certain mass limit, which is an essential improvement for space-efficient application of the JT cryocooler. Therefore, in this study, optimization design is carried out for a JT cryocooler working at liquid helium temperature. Based on the modification of Stirling cryocooler, pulse tube cryocooler and JT compressor, the developed JT cryocooler can provide a cooling capacity of 0.36 W at 4.18 K while the total input power and the total mass (without cryostat) are 1157 W and 26.8 kg, respectively. Compared with the literature research, it can be found that the developed JT cryocooler is suitable for space applications. [ABSTRACT FROM AUTHOR]

Vaned diffusers are widely used in centrifugal compressors due to their higher pressure-recovery coefficients compared to vaneless diffusers. In this study, the effects of the diffuser vanes' wrap angle and number of vanes on the aerodynamic performance of an industrial Methane centrifugal compressor with a pressure-ratio of 1.288 are studied using high fidelity steady-RANS numerical simulations. Three wrap angles (WA = 19.3o, 22.3o and 25.3°) and three number of vanes (NDiff. = 16, 20 and 24) are examined, while all the other geometrical and operational parameters are kept constant. Results showed that decreasing the wrap angle can enhance the choke flow rate of the compressor, with slight reduction in pressure ratio at low flow rates. However, increasing the diffuser wrap angle, intensifies the flow separation over the diffuser vanes. On average, the best aerodynamic performance of the compressor occurred at WA=22.3°. Results also showed that reducing the number of diffuser vanes enlarges the operating range of the compressor, however, the pressure ratio will be lower at the flow rates less than the design point. Conversely, higher pressure ratios will be achieved at the flow rates greater than the design flow rate. The optimal aerodynamic efficiency of the diffuser, considering both the pressure ratio and the total-to-total efficiency, was achieved when the NDiff value was set to 20. [ABSTRACT FROM AUTHOR]

This research aims to design an algorithm for optimizing clay 3DP. The algorithm's inputs are defined by combining the results of previous research and specific clay information selected from different regions of Anatolia, utilizing the design of experiment methodology. The design parameters include angle, profile and height; printing parameters include compressor pressure, speed, and layer height; and material parameters are assessed through drop spike, tube pressure, and flow rate tests. Once the inputs and their computation ranges were defined, the algorithm was tested with various inputs and corresponding physical prints to evaluate its recommendation capability. The test prints demonstrated that the printing suggestions made by the algorithm for design, printing and material parameters were suitable for the given parameter inputs. With its current state, the research is not an expert tool for recommendation but a base of a more complex framework for further research. [ABSTRACT FROM AUTHOR]

Recent advancements in computational fluid dynamics (CFD) enable new and more complex analysis methods to be developed for early design stages. One such method is the isolated unsteady diffuser model, which seeks to reduce the computational cost of unsteady CFD when modeling diffusion systems in centrifugal compressors with vaned diffusers by isolating the diffuser from the computational domain and prescribing an unsteady and periodic inlet boundary condition. An initial iteration of this computational methodology was developed and validated for the Centrifugal Stage for Aerodynamic Research (CSTAR) at the High-Speed Compressor Laboratory at Purdue University. However, that work showed discrepancies in flow structure predictions between full-stage and isolated unsteady CFD models, and it also presented a narrow scope of only a single loading condition. Thus, this work addresses the need for improvement in the modeling fidelity. The original methodology was expanded by including a more accurate, non-uniform definition of turbulence at the diffuser inlet and modeling several loading conditions ranging from choke to surge. Results from isolated unsteady diffuser models with non-uniform turbulence modeling were compared with uniform turbulence isolated unsteady diffuser models and full-stage unsteady models at four loading conditions along a speedline. Flow structure predictions by the three methodologies were compared using 1D parameters and outlet total pressure and midspan velocity contours. The comparisons indicate a significant improvement in 1D parameter and flow structure predictions by the isolated unsteady diffuser models at all four loading conditions when including more accurate non-uniform turbulence, without a corresponding increase in computational cost. Additionally, both isolated diffuser methodologies accurately track trends in 3D flow structures along the speedline. [ABSTRACT FROM AUTHOR]

The objective of this study is to understand how each variable impacts the optimal configuration of a marine diesel engine equipped with an electric hybrid air-charging system that allows energy assistance and recovery. The aim is to minimize CO2 emissions by reducing fuel consumption. The hybrid system offers flexibility in adjusting parameters from both the engine and air-charging system. It is compared with the baseline engine, which uses a free-floating turbocharger. The results show a significant improvement at low engine loads, where the baseline engine struggles to provide sufficient air. While turbine speed has little influence, compressor power reduces fuel consumption at low loads. However, at mid loads, resizing the turbomachine is necessary for further improvements. At high loads, full optimization of all variables is required to reduce fuel consumption. The electric hybrid system is particularly effective in tugboat-like conditions, where low loads dominate, but less impactful for ro-pax ferries. Despite the potential of the hybrid system, a fully optimized turbocharger could provide greater benefits due to reduced losses. Future studies could explore combining the adaptability of the hybrid system with a highly efficient turbocharger to reduce emissions across all load conditions. [ABSTRACT FROM AUTHOR]

The accurate prediction of the aeroelastic behavior of turbomachinery for aircraft propulsion poses a difficult yet fundamental challenge, since modern aircraft engines tend to adopt increasingly slender blades to achieve a higher aerodynamic efficiency, incurring an increased aeroelastic interaction as a drawback. In the present work, we present a reduced order model for flutter prediction in axial compressors. The model exploits the aerodynamic influence coefficients technique with the adoption of a broadband frequency signal to compute the aerodynamic damping for multiple reduced frequencies using a single training simulation. The normalized aerodynamic work is computed for a single oscillation mode at three different vibration frequencies, comparing the outputs of aerodynamic input/output models trained with a chirp signal to those from single-frequency harmonic simulations. The results demonstrate the ability of the adopted model to accurately and efficiently reproduce the aerodynamic damping at multiple frequencies and arbitrary nodal diameters with a single simulation. [ABSTRACT FROM AUTHOR]

Waste rock backfilled into a goaf can function as the main load-bearing carrier to support the overlying strata, so the compressive behavior of backfill materials plays a critical role in the effectiveness of strata control. However, in the laboratory, the specimen size also significantly influences on the accurate prediction of compressive deformation in waste rock backfill materials. To assess the influence of the specimen size on compressive behavior in waste rock backfill materials, a WAW-1000D (Changchun Xinte Testing Machine Co., Ltd., Changchun, Jilin Province, China) electric servo-motor testing machine and self-made compressors of different sizes were used to characterize the compressive deformation of waste rock backfill materials with different specimen sizes. The stress–strain relationships and changes in the void ratio of specimens were analyzed, revealing the influence of the specimen size on the compressive behavior. The research found that when the ratio of the inner diameter of compressors to the maximum particle size of specimens is 15:1 and above, the inner diameter of compressors only has a slight influence. Taking a backfill panel in Xinjulong Coal Mine as the engineering context, waste rock with particle sizes in the range of 0~20 mm was backfilled. The measured roof subsidence was 568 mm, matching the measured experimental value. The results provide data to support roof subsidence predictions following waste rock backfill mining. [ABSTRACT FROM AUTHOR]

Energy-efficient designs are the need of the hour for signal and image processing applications that are error-tolerant. The paper proposes a new 4:1 approximate arithmetic-based compressor developed by analyzing the probability-based tactics that have a higher degree of precision when implemented. Approximate $ n \times n $ n × n multiplier is designed using the proposed varying probability-based compressors. To validate the effectiveness of the new compressor, a $ 16 \times 16 $ 16 × 16 multiplier is designed. The $ n \times n $ n × n bit multiplier will have $ 2n $ 2 n columns of partial products(PP), in which the least significant n−1 columns are designed using the novel approximate 4:1 compressor and most n + 1 columns are designed with the exact compressor. The results of the 16-bit multiplier are superior to the performance of the exact multiplier in terms of power, area, power-delay-product (PDP), and area-delay-product (ADP) typically by $ 39\% $ 39 % , $ 20\% $ 20 % , $ 44\% $ 44 % , and $ 26\% $ 26 % respectively for Design 1 and $ 14\% $ 14 % , $ 24\% $ 24 % , $ 30\% $ 30 % , and $ 21\% $ 21 % , respectively for Design 2. The Peak Signal to Noise Ratio(PSNR), Mean Square Error(MSE), and Structural Similarity Index Measure(SSIM) for the output images processed by new approximate multipliers are acceptable when compared with precision and energy. [ABSTRACT FROM AUTHOR]

In axial compressors, control of the secondary flow is crucial for enhancing aerodynamic performance. Among various control strategies, vortex generators (VGs) are an effective passive method combining simplicity, cost-effectiveness, and reliability. This study investigates the VG evaluation model to assess VG effectiveness in reducing total pressure loss (ω) and controlling secondary flows. The impact of parameters such as the VG placement, stagger angle α, height, and length on the flow field and underlying flow mechanisms is analyzed, and methods for selecting the design parameters are examined. The findings reveal that positioning VGs near regions with high velocity differentials and away from the suction surface significantly reduces secondary flows. Achieving a balance between reducing total pressure loss ω and controlling secondary flows requires careful selection of the stagger angle α, as well as the height and length of VG. This study presents the design characteristic curve and identifies two key VG operation mechanisms that depend on the stagger angle α. The results of this study advance the development of more efficient VG designs and deepen our understanding of their operational mechanisms. [ABSTRACT FROM AUTHOR]

With the increasing scale of cloud computing applications of next-generation embedded systems, a major challenge that domain scientists are facing is how to efficiently store and analyze the vast volume of output data. Compression can reduce the amount of data that needs to be transferred and stored. However, most of the large datasets are in floating-point format, which exhibits high entropy. As a result, existing lossless compressors cannot provide enough performance for such applications. To address this problem, we propose a total variation reduction method for improving the compression ratio of lossless compressors (namely, FPC+ and FPZIP+), which employs a median-based hyperplane to precondition the data. In particular, we first try to exploit the space-filling curve (SFC), a well-known technique to preserve data locality for a multi-dimensional dataset. We show and explain why a raw SFC, such as Hilbert and Z-order curves, cannot improve the compression ratio. Then, we explore the opportunity and theoretical feasibility of the proposed total variation reduction-based algorithm. The experiment results show the effectiveness of the proposed method. The compression ratios are improved up to 48.2% (20.6% on average) for FPZIP and 42.4% (18.4% on average) for FPC. Moreover, through observing the time composition of the proposed method, it is found that the median finding holds a high percentage of the execution time. Hence, we further introduce an approximate median finding algorithm, providing a linear-time overhead reduction scheme. The experiment results clearly demonstrate that this algorithm reduces execution time by an average of 56.7% and 40.7% compared to FPC+ and FPZIP+, respectively. [ABSTRACT FROM AUTHOR]

Few universities in the world conduct experimental research on high-speed, high-power turbomachinery. The Purdue High-Speed Compressor Research Laboratory has a longstanding tradition of partnering with industry sponsors to perform high-TRL (technology readiness level) experiments on axial and radial compressors for aerospace applications. Early work in the laboratory with Professor Sanford Fleeter and Professor Patrick Lawless involved aeromechanics and the addition of a multistage axial compressor facility to support compressor performance studies. This work continues today under the guidance of Professor Nicole Key. While other universities may operate a single-stage transonic compressor or a low-speed multistage compressor, the Purdue 3-Stage (P3S) Axial Compressor Research Facility provides a unique environment to understand multistage effects at speeds where compressibility is important. Over the last two decades, several areas of important research within the gas-turbine engine industry have been explored: vane clocking, stall/surge inception, tip-leakage/stator-leakage (cavity leakage) flow characterization, and forced response, to name a few. This paper addresses the different configurations of the facility chronologically so that existing datasets can be matched with correct boundary conditions and provides an overview of the different upgrades in the facility as it has developed in preparation for the next generation of small-core compressor research. [ABSTRACT FROM AUTHOR]

One of the primary parts of a closed Brayton cycle that uses a helium–xenon mixture as the working medium is a centrifugal compressor. Nowadays, there has been minimal research on the theoretical underpinnings and design procedures of a helium–xenon mixture centrifugal compressors, and the internal flow mechanisms remain poorly understood. In this study, we present a redesign of the 15 g/mol helium–xenon centrifugal compressor originally developed by Bruno M, utilizing a helium–xenon mixture as the working fluid to enhance compressor performance and facilitate an in-depth analysis of the internal flow dynamics. The findings indicate a significant expansion of the stable operating range of the redesigned compressor under identical outlet conditions, with a 33.27% increase in flow margin and substantial improvements in the pressure ratio. Furthermore, under consistent inlet conditions, at an operational flow rate of 0.8657 kg/s, the redesigned compressor exhibits a pressure ratio that is 2.11% greater than that of the original design, along with a variable efficiency increase of 1.1%. [ABSTRACT FROM AUTHOR]

Natural gas-doped hydrogen transportation has been widely used in industrial engineering. The change of the physical parameters of the conveying medium affects the working performance of the centrifugal compressor. This study aims to explore the aerodynamic performance of centrifugal compressors for hydrogen mixed natural gas, including the effects of hydrogen blending ratio (HBR) and inlet temperature on the pressure ratio and isentropic efficiency of compressors. The numerical simulation method is used and the results are compared with the experimental results to determine the reliability of the numerical simulation method. The results show that the pressure ratio decreases with the increase of HBR where the inlet temperature and rotation speed are constant. The pressure ratio and efficiency of the compressor are the highest when the conveying medium is pure natural gas (HBR = 0). The maximum pressure ratio reduction is 4.8% when the HBR is 5% and the inlet temperature is increased by 20 K. In summary, when the conveying medium of the compressor changes from pure natural gas to hydrogen-mixed natural gas, the working range and efficiency of the compressor will be reduced. Therefore, it is necessary to increase the rotation speed of the compressor or redesign the centrifugal compressor for hydrogen-mixed natural gas in order to achieve a constant flow rate at the outlet of the compressor. [ABSTRACT FROM AUTHOR]

This paper proposes two novel approaches: a signed–unsigned modified Booth decoder/encoder that is used for the production of partial products and a 5-2 compressor for the addition stage of partial products. The improvement of a circuit can be done at the transistor level and the gate level. To improve the circuits at the gate level for the modified Booth decoder/encoder, a new table was designed and also the 5-2 compressor was obtained by changing the truth table. Speed, power consumption and area were improved in the proposed structures. In this paper, at the transistor level, the gate diffusion input (GDI) technique was used to implement logical gates and the gate-level delay of the GDI structures was also calculated. The results indicated that the proposed 5-2 compressor had a delay of 119 ps with a power consumption of 65μW, which shows a 23.5% improvement in power delay product (PDP) compared to the best structure in the comparison table, whereas the proposed Booth decoder/encoder had a delay of 257 ps with a power consumption of 61.74μW and shows a 63.7% improvement in PDP compared to previous studies. By using the proposed structures in the multiplier, a 22% improvement in PDP was observed. To simulate the obtained structures, the TSMC 0.18 and 0.09μm technologies and the HSPICE software were used. Cadence software was used to implement the layouts of the proposed structures. [ABSTRACT FROM AUTHOR]

The energy-efficient error-tolerant circuits have paved the way for a whole new area in low-power consumption applications with approximate computing. The approximate computing fulfills the trade-off requirement of exact computation and provides efficient performance. In this paper, a novel energy-efficient multiplier has been proposed for image processing applications. In the multiplication process, compressors are used as an important component for the reduction of partial products. Higher-order approximate 5:2 and 6:2 compressors are also designed and simulated in VIVADO using Verilog coding. The proposed higher-order compressors result in less area and low-power consumption in comparison with the existing state-of-the-art technique. These high-performance compressors are used at the multipliers’ reduction stage, resulting in an energy-efficient circuit for error-tolerant applications. All the simulations were carried out in VIVADO considering 8-bit inputs. Multiplication performance shows 37.77 % (8-bit) improvement in terms of power consumption in comparison to the conventional multiplier. The multiplication process has been done on the original, negative, and sharpened images using their masks. The proposed multiplier shows 51.36% (original image), 6.04% (negative image), and 22.44% (sharpened image) PSNR improvement in comparison to state-of-the-art work. [ABSTRACT FROM AUTHOR]

This study investigates the implementation of a cryogenic chiller utilizing a mixed-refrigerant cascade refrigeration cycle (MRCRC). In this setup, R-404A is employed in the high-temperature circuit (HTC), while a mixture of refrigerants is utilized in the low-temperature circuit (LTC). Unlike a conventional MRCRC that operates without a receiver to maintain the composition ratio, this research explores the impact of receiver installation on system performance. Experiments were conducted with and without a receiver to assess performance improvements and device behavior. With a fixed refrigerant charge of 4 kg, the suction and discharge pressures of the LTC compressor remained low and stable after the receiver's installation. The addition of a receiver significantly reduced the cooling time, with further reductions observed as the refrigerant charge increased. The system achieved evaporative heat capacities of 0.59, 1.76, and 2 kW for refrigerant charges of 4, 7, and 9 kg, respectively. Notably, at the maximum refrigerant charge of 11 kg, the evaporative heat capacity peaked at 3.3 kW. These findings indicate that incorporating a receiver is crucial for enhancing the cooling performance of cryogenic coolers using mixed refrigerants and stabilizing device operation. This contrasts with previous studies that omitted receivers due to concerns over potential alterations in the composition ratio of the mixed refrigerant. [ABSTRACT FROM AUTHOR]

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Background: Chromosome organization plays an important role in biological processes such as replication, regulation, and transcription. One way to study the relationship between chromosome structure and its biological functions is through Hi-C studies, a genome-wide method for capturing chromosome conformation. Such studies generate vast amounts of data. The problem is exacerbated by the fact that chromosome organization is dynamic, requiring snapshots at different points in time, further increasing the amount of data to be stored. We present a novel approach called the High-Efficiency Contact Matrix Compressor (HiCMC) for efficient compression of Hi-C data. Results: By modeling the underlying structures found in the contact matrix, such as compartments and domains, HiCMC outperforms the state-of-the-art method CMC by approximately 8% and the other state-of-the-art methods cooler, LZMA, and bzip2 by over 50% across multiple cell lines and contact matrix resolutions. In addition, HiCMC integrates domain-specific information into the compressed bitstreams that it generates, and this information can be used to speed up downstream analyses. Conclusion: HiCMC is a novel compression approach that utilizes intrinsic properties of contact matrix, such as compartments and domains. It allows for a better compression in comparison to the state-of-the-art methods. HiCMC is available at https://github.com/sXperfect/hicmc. [ABSTRACT FROM AUTHOR]

For compressor cascade flow field modeling, there exists strong velocity shear in the leading edge separation flow, boundary layer, and wake, which leads to increased modeling errors. To improve the accuracy of the flow field modeling method, this paper introduces the concept of numerical flux from the finite volume method into the loss function to implement Euler equation physics-informed learning, and a finite volume flux-informed neural network (FVFI-net) is constructed. Selecting a high-load, large-turning-angle compressor cascade as the study object, a comparative analysis is conducted on the advantages and disadvantages of purely data-driven, weak physical constraint, and finite volume flux-informed methods in compressor cascade flow field modeling. The study found that compared to purely data-driven and weak physical constraint methods, FVFI-net can reduce the average error of aerodynamic parameters in the flow field by approximately 45.6% and 29.5%, respectively, at a 0° angle of attack. For the flow separation problem occurring at the suction side leading edge and the blade wake area caused by a 5° angle of attack, FVFI-net can effectively reduce modeling errors near the leading edge, in the wake region, and near the periodic boundaries, thus reducing the average error of the aerodynamic parameters of the flow field by about 49.2%and 31.3%, respectively, compared to pure data-driven and weak physical constraint methods. [ABSTRACT FROM AUTHOR]

Compressors are inevitably exposed to diverse geometric deviations from manufacturing errors and in-service degradation. Consequently, the evaluation of performance uncertainties becomes of utmost importance for compressors in engineering application. However, the presence of high-dimensional and strongly nonlinear geometric deviations poses significant challenges in efficiently and accurately assessing the performance uncertainties of compressors. This study proposes an active subspace-based dimensionality-reduction method for high-dimensional uncertainty quantification (UQ) of compressors. Based on the active subspace (AS) method, a dimensionality-reduction high-precision artificial neural network is raised to solve the dimension disaster problem for high-dimensional UQ. Additionally, a data-driven approach is used to calculate the gradient of the quantity of interest, addressing the issue of high computational cost during the AS dimensionality reduction process. Furthermore, the Shapley method is applied to explore the influence mechanism of geometric uncertainties on performance deviations of compressors. The UQ of one transonic compressor stage at design point and near stall point is conducted by the proposed method. The findings show that the original 24-dimensional uncertainties are reduced to three-dimensional uncertainties by using this method. Consequently, the required sample size is reduced by 75% while maintaining almost unchanged model accuracy. The findings reveal that the sweep and stagger deviation of the rotor are key uncertainties on the performance of the compressor. The dispersion in efficiency is attributed to variations in shock wave position and intensity, while the dispersion in total pressure ratio is primarily affected by changes in rotor work capacity. Moreover, the dispersion at near stall is 50% higher than that at design point. Therefore, when studying UQ, it is important to pay closer attention to the performance dispersion at near stall conditions. [ABSTRACT FROM AUTHOR]

We report the development of a seeded diode-pumped 1338-nm Nd:YAG amplifier which delivers 400-ps, 6-mJ, single-frequency pulses every half second with a fluctuation of ∼ 0.7%. A highly stable pulsed current controller is constructed to drive an 808-nm diode laser array that ensures the high stability of the laser. Numerical calculations show that 9.2 μm or 10.2-μm picosecond (<10 ps) pulses with 100-μJ energy can be generated by mixing the 1338-nm 6-mJ pulses with 1540-nm chirped pulses in a BGGSe nonlinear crystal and compressing the pulse with a grating compressor. [ABSTRACT FROM AUTHOR]

Seasonal-based energy storage is expected to be one of the main options for the decarbonization of the space heating sector by increasing the renewables dispatchability. Technologies available today are mainly based on hot water and can only partially fulfill the efficiency, energy density and affordability requirements. This work analyzes a novel system based on pumped thermal energy storage (PTES) concept to maximize renewables and waste heat exploitation during summer and make them available during winter. Organic fluid-based cycles are adopted for the heat upgrade during hot season (heat pump (HP)) and to produce electricity and hot water during cold season (power unit (PU)). Upgraded thermal energy drives an endothermic reaction producing dehydrated solid salts, which can be stored for months using inexpensive and high energy density solutions. This paper focuses on thermodynamic cycles design, comparing the performance attainable with several working fluids. Two different configurations are investigated: coupled systems, sharing the fluid and heat exchangers in both operating modes, and decoupled systems. A preliminary economic assessment completes the study, including a sensitivity analysis on electricity and heat prices. Cyclopentane is identified as a promising working fluid for coupled systems, reaching competitive round trip efficiencies (RTEs), maximizing the ratio between performance and HX surfaces, without excessive turbomachinery volume ratios and volumetric flows. Economic analysis shows that solutions with lower efficiency, but also lower capital cost, can achieve competitive payback times (PBT). On the contrary, decoupled systems are less attractive, as they reach slightly higher thermodynamic performance, but require higher capital costs, possibly being of interest only in specific applications. [ABSTRACT FROM AUTHOR]

Owing to their high specific energy capabilities, ultramicrogas turbines (UMGT) are a high-potential technology to provide portable electric power supply for applications with demand of less than 1 kW. UMGT conceptual design is challenged by small-scale effects augmenting interdisciplinary dependencies leading to highly coupled, nonlinear component interactions. This work provides a novel approach to conceptual UMGT design by combining reduced order component and system modeling with constrained multi-objective optimization. Hereby, Part I presents integrated design and performance modeling of compressor, turbine, combustor, and generator. In Part II, the heat engine and generator modules are merged into a system framework by establishing conceptual UMGT rotor geometry and engine design. Following bearing selection and lifetime assessment, experimentally validated reduced order models are developed for heat transfer and rotordynamic analysis. Using the elaborated framework, a constrained multi-objective system optimization of a 300 W engine is performed based on ten design parameters and comparing SiAlON and Inconel 718 as potential rotor materials available for additive manufacturing. Hereby, bearing lifetime, system efficiency, and specific power are maximized while meeting rotordynamic, structural, and thermal requirements. Evaluating the results, interdisciplinary effects are highlighted, and two optimum engine configurations are suggested. [ABSTRACT FROM AUTHOR]

Ultramicrogas turbines (UMGTs) for electric power generation up to 1 kW are a viable replacement technology for lithium batteries in drones due to their high energy density. Previous research has shown that small-scale effects disqualify conceptual design practices applied to larger gas turbines owing to highly coupled, nonlinear component interactions. To fill this gap, we propose an interdisciplinary conceptual design and analysis framework based on reduced order models. To this end, the current work is divided into two parts covering component design and system integration, analysis, and optimization. In Part I, automated conceptual design of all engine subcomponents is elaborated facilitating interdependent reduced order models for compressor, turbine, combustor and high-speed generator while also considering additive manufacturing constraints. In a second step, the reduced order performance models are compared to computational fluid dynamics (CFD) Reynolds-averaged-Navier-Stokes (RANS) simulations of various turbomachinery geometries as well as experimental data of combustor and high-speed generator prototypes, showing good agreement and thus validating the component modules. In conclusion, the first part of this work elaborates an automated and efficient method to conceptual design of all components required for a functional UMGT. Since the strategy is applicable independent of component arrangement and engine layout, the proposed methods offer a universal framework for small gas turbine generators. [ABSTRACT FROM AUTHOR]

• Visualization experiment using a high-speed camera of a vertical sliding vane rotary engine. • Investigate the effect of compressor rotational speed on vane contact. • Effect of oil supply amount and temperature on vane chattering. • Influences of ratio of compressor discharge pressure and supply pressure on vane and cylinder contact. In this study, the impacts of various factors on the chattering phenomenon in sliding vane compressors, which is a crucial aspect that influences their performance and efficiency were explored. The analysis focused on the compressor rotational speed, pressure ratio, and operating temperature, considering both ambient and heated conditions. The aim was to provide a comprehensive understanding of the relationship between these factors and the occurrence of chattering at different operational intervals, as well as the vane sealing performance and adherence to the chamber wall. The methodology involved examining vane behavior and the chattering occurrence across three intervals under various conditions, specifically looking at oil films formation and sealing performance degradation. The experimental results provided notable insights into the chattering phenomenon. It was shown that as the pressure ratio increased and the compressor rotational speed decreased, the sealing performance deteriorated. Moreover, when operating under heated conditions, a decrease in oil viscosity leads to reduced friction between the vane and bearing, improving vane adherence compared to ambient conditions. The methodology and findings of this study provide insights into the chattering phenomenon in vane compressors by considering the interplay between various factors. The results emphasize the importance of optimizing the compressor oil refueling flow, rotational speed, pressure ratio, and operating temperature, to ensure proper lubrication and efficient interaction between the vanes and compression chamber walls for improved compressor performance and reduced operational challenges. [ABSTRACT FROM AUTHOR]

Miniature scroll compressors (MSCs) are recognized for their superior characteristics—compact design, silent operation and energy-saving performance. One of its main challenges is to maintain dynamic sealing between the fixed and orbiting scrolls during the operation. This paper adopts a passive magnet mechanism (PMM) to balance the axial gas force in MSCs. The PMM with an integral magnet configuration (IMC) is investigated first, and the dimensions of the magnet and fixed ring are found as the paramount factors to determine the magnitude of axial magnetic force. However, the IMC is unable to follow the unsteady characteristics of the target axial gas force, so the scrolls will experience a large period of over-sealing during its operation. To overcome this limitation, an innovative modular magnet configuration (MMC) is proposed and investigated. The height of each magnet segment is treated as individual design variable, and genetic algorithm optimization is carried out to seek for the best force balance performance according to two indices—maximum force difference (MFD) and integral-average force difference (IAFD). With precise design of each magnet segment, the MMC is able to provide unsteady magnetic force and thus better balance performance. Compared with the IMC, the improvements are up to 52 % reduction of MFD and 66 % reduction of IAFD. The derived superior MMC designs reveal a common characteristic that the "N" and "E" magnets have short segments at their outer fringe and the "S" and "W" magnets have short segments at their inner fringe. The axial magnetic force characteristics of the IMC and MMC are validated by prototype experiments. [ABSTRACT FROM AUTHOR]

• Semi-empirical models for suction flow rate, injection flow rate, input power consumption, and discharge temperature are proposed for scroll compressors with vapor injection. • The modeling approach can be consistently applied to fixed-speed and variable-speed compressors. • The models were fit and evaluated using a data set containing four compressors. The prediction accuracy is similar to other proposed models and the model requires relatively low testing effort to fit the empirical parameters. • The models were applied to one compressor for operation with and without vapor injection. The prediction errors for both modes of operation are similar, while only using one set of model parameters. Semi-empirical models for predicting the suction flow rate, injection flow rate, input power consumption, and discharge temperature are proposed for scroll compressors with vapor injection. A data set containing four compressors wherein each compressor was tested over a range of operating conditions is used to evaluate the models. The fitted parameters of the models and the prediction errors of each data set are discussed. The accuracy and generalizability of applying the models to the same compressor with and without vapor injection are also discussed. [ABSTRACT FROM AUTHOR]