Search Results (1,596)

The current research is focused on the introduction of a heat pump (HP)-assisted organic Rankine cycle (ORC), which runs on the heat extracted from a high-temperature borehole thermal energy storage (BTES). By varying different source temperatures from 40 °C to 60 °C, the HP cycle works to upgrade the heat to run the ORC. Different combinations of environmentally friendly fluids are studied in comparison to match the top and bottom cycles and to make the overall system a combined heat and power (CHP) system. A power sufficiency condition is defined to compare and identify the best working fluid combination for the HP cycle and ORC. Based on the analysis, ammonia for the HP and R1234zee for the ORC emerged to be a suitable combination among all the studied combinations. As an example, for a BTES heat source of 237 kW at the source temperature of 60 °C, the BTES–HP–ORC–district heating system with the ammonia–R1234zee pair has resulted in the HP compressor work input of 21.9 kW with the coefficient of performance (COP) of 10.9 for the HP cycle and the ORC net work output and district heating supply of 10.4 kW and 209 kW, respectively, with the thermal efficiency (η) of 4.3% for the ORC at the evaporation temperature of 65 °C. A study in terms of the greenhouse gas (GHG) emissions reveals the feasibility of the system depending on the regional GHG intensity and emission factor of electricity and natural gas. Full article

Integrated thermal management system (ITMS) technology for electric vehicles (EV) has become a major industry research direction. However, R290 refrigerants are still not applied on a large scale in EVs. Therefore, we developed a suitable thermal management system for R290 in this study. This architecture adapts an unusual indirect design, which can coordinate the heat between the air conditioner, battery pack, and electric motor. We focused on heat pump air conditioning systems for EV thermal management; thus, we carried out the performance analysis of R290 under the cooling and heating conditions of our ITMS through an experimental approach. The current study explores various aspects affecting the performance of heat-pump air conditioners: refrigerant charge, electronic expansion valve (EXV) opening, compressor speed, and performance between R290 and R134a under different external temperatures. We aim to improve cooling and heating efficiencies. Among these parameters, the EXV opening and compressor speed have the greatest impact on the performance of the ITMS, as evidenced by the optimal EXV opening and lower compressor speed to maximize the coefficient of performance (COP) and increase the heat transfer rate. In addition, this study has shown that, compared to an ITMS equipped with R134a, R290 has a smaller refrigerant charge, better heat transfer rate and COP under heating conditions, and similar performance under cooling conditions. Full article

The compressor is a critical component of cryogenic separation industrial systems, and its reliable operation is essential for the stable functioning of the entire system. Existing research focuses on predicting compressor conditions using experimental or simulation data, often neglecting analysis based on actual industrial data. To address this gap, this paper presents an innovative prediction model for compressor data utilizing an LSTM–self-attention mechanism, specifically designed for real industrial systems. The proposed model combines the sequential learning capabilities of LSTM with the dynamic feature extraction strengths of self-attention, enabling highly accurate predictions by enhancing sensitivity to critical data features. The actual vibration data from a compressor spanning 12 months are analyzed and compared. The results demonstrate that the proposed model reduces prediction error by $46\%$ in MSE and $50\%$ in RMSE compared to SVR. These findings highlight the model’s potential for real-time monitoring and early fault detection, providing a robust theoretical foundation for condition-based analysis and preventive maintenance in industrial compressor applications. Full article

Permanent Magnet Linear Oscillating Motors (PMLOMs) are popular in micro-positioning systems, biomedical devices, and refrigeration compressors due to their simple structure, high efficiency, rapid response, and quiet operation. This paper proposes a method for the analysis and optimization of electromechanical systems that employs a moving magnet linear oscillating motor. A simplified magnetic circuit method model was built to derive an electromagnetic thrust formula, and the initial design parameters of the motor and the thrust at the equilibrium position were calculated. Subsequently, a finite element model was developed, and a multi-objective optimization method was applied to refine the key dimensions of the motor to enhance its thrust characteristics. Furthermore, an analysis of the resonant characteristics of the electromechanical coupled system was conducted to identify the optimal operating frequency for the optimization scheme. Finally, the experimental validation of the optimized design was performed on a prototype, with the measured data showing a general correlation with the trends observed in the simulation analysis results. The effectiveness of this system analysis method was validated through experimental data. The results demonstrate that the thrust at the initial position is linearly correlated with both the outer arc radius of the permanent magnet and its mechanical pole arc coefficient. Additionally, the axial length of the outer stator, the axial spacing between the two outer stators, and the axial length of the magnets serve as key influencing parameters for the thrust characteristics within the effective stroke range. Furthermore, when the motor operates at its mechanical resonance frequency, it can attain the maximum efficiency. Full article

The compressor in the heat pump is crucial for efficient geothermal energy utilization, but faces challenges in optimizing energy efficiency, especially under variable working conditions. This paper investigates the complex energy characteristics of the R134a refrigerant in centrifugal compressors using CFD, combining entropy generation and relative energy rotor enthalpy to analyze energy conversion theory. Key factors such as temperature and pressure are fully considered. The results indicate that energy loss in centrifugal compressors mainly occurs in the gap between the blade top and near the tongue, with a vortex tendency at the impeller’s tail edge. As the flow rate increases from 1.2 kg/s to 1.45 kg/s, the maximum total entropy generation in the impeller decreases by 161%, and the rotor enthalpy minimum value increases by about 90%. This energy conversion analysis method can identify changes in the location and extent of energy loss, offering a new perspective for optimizing the structure and energy-saving design of centrifugal impellers. Full article

Integrating machine learning algorithms leveraged by advanced data acquisition systems is emerging as a pivotal approach in predictive maintenance. This paper presents the deployment of such an integration on an industrial air compressor unit. This research combines updated concepts from the Internet of Things, machine learning, multi-sensor data collection, structured data mining, and cloud-based data analysis. To this end, temperature, pressure, and flow rate data were acquired from sensors in contact with the compressor. The observed data were sent to the Structured Query Language database. Then, a Linear Regression model was fitted to the training data, and the optimized model was stored for real-time inference. Afterward, structured data were passed through the model, and if the data exceeded the determined threshold, a warning email was sent to an operator. Adopting the Internet of Things enhances surveillance for specialists, decreasing the failure and damage probabilities. The model achieved 98% accuracy in the Mean Squared Error metric for our regression model. By analyzing the gathered data, the implemented system demonstrates the capabilities to predict potential equipment failures with promising accuracy, facilitating a shift from reactive to proactive maintenance strategies. The findings reveal substantial potential for improvements in maintenance efficiency, equipment uptime, and cost savings. Full article

Gas turbines are widely used in power generation due to their efficiency, flexibility, and low environmental impact. Modeling, especially in thermodynamics, is crucial for the designer and operator of a gas turbine. An advanced and rigorous thermodynamic model is essential to accurately predict the performance of a gas turbine under on-design operating conditions, off-design or failure. Such models not only improve understanding of internal processes but also optimize performance and reliability in a wide variety of operational scenarios. This article presents the development of a thermodynamic model simulating the off-design performance of a gas turbine. The mathematical relationships established in this model allow for quick calculations while requiring a limited amount of data. Only nominal data are required, and some additional data are needed to calibrate the model on the turbine under study. A key feature of this model is the development of an innovative relationship that allows direct calculation of the mass flow of air entering the turbine and, thus, the performances of the turbine according to atmospheric conditions (such as pressure, temperature, and relative humidity) and the position of the compressor inlet guide vanes (IGV). The results of the simulations, obtained using code implemented in MATLAB (R2014a), demonstrate the efficiency of the model compared to experimental data. Indeed, the model relationships exhibit high determination coefficients (R² > 0.95) and low root mean square errors (RMSE). Specifically, the simulation results for the air mass flow rate demonstrate a very high determination coefficient (R² = 0.9796) and a low root mean square error (RMSE = 0.0213). Full article

In this study, mono- and bimetallic platinum (Pt), palladium (Pd) and Pt-Pd nanoparticles were synthesized using the wet sol–gel method, employing a carbon-based XC72R as catalytic carrier. The overall metal content was set at 40 wt.% at varying Pt:Pd ratios. Characterization of the morphology and surface structure was conducted through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD) analyses. The electrochemical performance and catalytic activity against the hydrogen evolution reaction (HER) were assessed in a three-electrode cell for screening purposes, as well as in a prototype cell of an electrochemical hydrogen pump/compressor (EHP/C) where the catalysts served as cathodes, while the anode was Pt/XC72 40% wt. with 0.38 mg_Pt·cm⁻² within a membrane electrode assembly (MEA) with a 180 µm thick Nafion 117 proton-conductive membrane. The results obtained indicated superior catalytic activity of the bimetallic catalysts in comparison to the pure metal samples. Further electrochemical tests in an EHP/C cell at varying differential pressures in the range of 0–3 bar revealed stable behavior and high current density, reaching approximately 0.7 A cm⁻² at 60 °C. The accelerated durability tests performed demonstrated excellent stability of the synthesized composite catalysts. These findings underscore the potential of Pt-Pd nanoparticles as efficient catalysts with sustainable performance for electrochemical hydrogen pumping/compressing applications. Full article

This paper presents a low-order three-dimensional approach for predicting the inviscid flow around low-pressure compressors. The method is suitable for early design stages and allows a broad exploration of design possibilities at minimal cost. It combines the vortex lattice method with the panel method by using a mixed boundary condition. In addition, it models the tip-leakage flow using an iterative algorithm. First, the verification of the approach is carried out on a low-pressure compressor configuration. The wake length is a decisive parameter for ensuring correct flow deflection in ducted applications. A periodicity condition is introduced and validated, which reduces the computational and memory requirements. On average, the calculations take less than one minute in real time. The approach is validated on the same low-pressure compressor configuration. A good agreement is obtained with RANS concerning the mean flow and the tip-leakage flow characteristics. Sensitivity to the mass flow rate is also fairly well predicted, although discrepancies develop at lower mass flow rates. Full article

Flexure-based Stirling cryocooler compressors are a critical technology in providing cryogenic temperatures in various advanced engineering fields, such as aerospace, defense, and medical imaging. The most challenging problem in the design of this type of compressor is achieving a precise alignment that preserves small gaps between the components moving relative to each other and avoids severe friction and wear. This paper introduces a novel experimental procedure for designing Stirling cryocooler compressors, leveraging a recently developed nonlinear experimental modal analysis method known as response-controlled stepped-sine testing (RCT). The alignment in a compressor prototype was significantly improved in light of a series of RCT with base excitation. The enhanced compressor design was subsequently validated though a series of constant-current tests, which confirmed the elimination of the sticking/locking phenomenon observed in the initial design. Furthermore, an indirect harmonic force surface (HFS)-based approach proposed for weakly nonlinear systems was extended to identify the high and nonlinear damping (up to a 65% hysteretic modal damping ratio) observed in the enhanced compressor design due to excessive friction. As another contribution, it was shown that the extrapolation of the HFS gives accurate results in the prediction of the nonlinear modal parameters at response levels where no experimental data are available. In light of these findings, it was concluded that the enhanced design needs further design modifications to further decrease the friction and wear between the moving parts. Overall, this study provides valuable insights for designing cryocooler compressors, with implications for aerospace and medical applications. Full article

Recent methane emissions regulations present a challenge for the large-bore, natural-gas-fueled engines used at over 1700 compression stations across the US. Poor air–fuel mixing in the main combustion chamber of these engines results in low combustion efficiency and the resulting methane emissions. High-pressure fuel injection is believed to be a significant development in improving air–fuel mixing in natural-gas engine combustion chambers. This study aims to determine the sensitivity of in-cylinder mixing to injection pressures using Computational Fluid Dynamics (CFD) simulations, determine the limits of high-pressure fuel injection, and explore high-momentum low-pressure fuel injection. The engine, modeled using Converge Studio for CFD, was a Cooper-Bessemer large-bore, four-cylinder, GMV-4TF spark-ignited natural-gas engine with direct injection. The model was simulated for four sets of configured cases—baseline; ideal mixing; injection pressure variation; and low-pressure, high-momentum injection. The results show that fuel injection at 700 psi and −115 degrees BTDC gives the best in-cylinder mixing and improved mixing, potentially reducing methane emissions by half. The optimal timing for the injection at different injection pressures was determined. The level of mixing in low-pressure fuel-injection systems was also improved by the high-momentum fuel injector design. It was concluded that mixing can be further improved in integral gas compressor engines through fuel injection optimization. Full article

Waste heat recovery is one of the most investigated solutions for increasing the efficiency of powertrains in the transportation sector. A major portion of thermal energy is wasted via exhaust gases. Almost one third of fuel energy is lost, and its recovery as propulsion energy is a promising goal. Moreover, this enables the increased electrification or hybridization of powertrains, assuming the energy recovered is converted into electrical form and used to fulfill different vehicles’ needs. The present study focuses on a dual-stage energy recovery system designed to enhance the efficiency of internal combustion engines (ICEs) in heavy-duty vehicles (HDVs). The system combines a turbocompound unit for direct heat recovery (DHR) and an organic Rankine cycle (ORC) for indirect heat recovery (IHR). These technologies aim to exploit waste heat from exhaust gases, converting it into electrical energy. In this regard, electrical energy can be stored in a battery for it to be available for the energy needs of powertrains that use hybrid propulsion and for driving pumps and compressors on board, following recent technologies of auxiliaries on demand. The proposed setup was modeled and analyzed under off-design conditions to evaluate energy recovery potential and engine performance impacts. From this point of view, in fact, any device that operates on exhaust gas introduces a pressure loss, increasing engine backpressure, whose effect is an increase in specific fuel consumption. An estimate of this negative effect is presented in this paper based on experimental data measured in a F1C IVECO™ engine. An average net recovery of 5–6% of engine power has been demonstrated, with an important prevalence of the turbocompound with respect to the ORC section. The results demonstrate the viability of integrating DHR and IHR stages, with implications for advancing sustainable transportation technologies. Full article

This paper establishes a simulation model for the performance of an R290 variable frequency compressor in automotive air conditioning and sets up a compressor performance testing system. It investigates the effects of different evaporation temperatures, condensation temperatures, compressor speeds, and pressure ratios on the oil circulation rate (OCR), as well as the impact of various oil circulation rates on the performance of the R290 compressor. As the comparison between simulation and experimental data shows, compressor performance predictions from the simulation model align with experimental results when the OCR is not taken into consideration. Experimental results indicate that the OCR increases with a rising evaporation temperature, decreases with a lowering condensation temperature, and increases with higher compressor speeds. The simulation model shows a minor deviation when predicting volumetric efficiency, while errors are larger when predicting isentropic efficiency and the discharge temperature. Isentropic efficiency and the discharge temperature show a notable impact from the OCR. Additionally, for system cooling capacity, power, and COP predictions, when the OCR is within the range of 2~10%, the accuracy of the simulation model proves satisfactory, with deviations within 5%. Full article

In Portugal, cheese holds a prominent position as a major dairy product, with traditional varieties enjoying widespread acclaim. A number of these cheeses have earned Protected Designations of Origin status, showcasing their unique qualities and regional significance. Notable examples include “Serra da Estrela”, “Serpa”, and “Terrincho”. The production of cheese relies heavily on heating and cooling processes, which account for a substantial portion of the total energy consumed. This research endeavour undertakes a detailed description and analysis of traditional cheesemaking practices within Portugal’s interior central region, with a particular emphasis on the economic and energetic efficiency of refrigeration systems. For this purpose, thirty-one traditional cheese production facilities were examined and classified into two distinct groups: Traditional Industrial Producers and Traditional Handmade Producers. The analysis was conducted through two separate case studies. The findings reveal that a significant 58% of the energy consumed by these facilities is attributed to electrically powered cooling systems, encompassing components such as fans, compressed air systems, and illumination. Within the production processes, fuel combustion, primarily naphtha or propane, serves the purpose of water heating and steam generation. Based on energy consumption reports, the Specific Energy Consumption of electricity was determined to be 0.283 kWh/lRM for TIP and 0.169 kWh/lRM for THP. Furthermore, several linear regression models were developed to explore the relationships between parameters such as cold room volume, compressor power, and raw material quantity. The study also identified key factors contributing to reduced energy efficiency within the facilities. These factors include inadequate insulation of buildings and cold rooms, outdated and poorly maintained refrigeration equipment situated in suboptimal locations, and cold rooms and compressors that are oversized and not optimised for efficient operation. Full article

For a special bilaterally symmetric airfoil (BSA), this paper designs an active flow control scheme based on the Co-Flow Jet (CFJ) and adaptive morphing technology, and establishes a numerical simulation method which is suitable for simulating aerodynamic characteristics. The accuracy and effectiveness of the numerical method has been verified through benchmark cases. This study investigates the effects of jet intensity, suction slot position and angle, and deflection angles of the leading and TE flap on the aerodynamic performance parameters and flow field structure of the bilaterally symmetric airfoil. The results show that the adaptive morphing technology can significantly improve the equivalent lift coefficient and equivalent lift-to-drag ratio of the bilaterally symmetric airfoil, without obviously increasing the CFJ power consumption coefficient. Selecting an appropriate CFJ intensity can achieve a relatively high equivalent lift-to-drag ratio with a low compressor power requirement. Moving the suction slot rearward can increase the lift coefficient, and placing it on the trailing edge (TE) flap can more efficiently delay flow separation, reduce power consumption, and increase the equivalent lift-to-drag ratio. The suction slot angle has little effect on the lift coefficient, but a larger suction slot angle can enhance the equivalent lift-to-drag ratio. Increasing the TE flap deflection angle enhances both the lift coefficient and drag coefficient, as well as the power consumption coefficient at high angles of attack. But it has little effect on the maximum equivalent lift-to-drag ratio. Increasing the leading edge flap deflection angle can improve the maximum equivalent lift-to-drag ratio while increasing the angle of attack corresponding to it. Overall, choosing a CFJ and adaptive morphing parameters by considering different factors can enhance the aerodynamic performance of the bilaterally symmetric airfoil. Full article