Operating Conditions Research Articles

ANALYSIS OF THE IMPACT OF CROSS-SECTION DAMAGE ON THE STRENGTH AND DEFORMABILITY OF BENT REINFORCED CONCRETE ELEMENTS

The article analyzes defects and damage in reinforced concrete structures, particularly physical, biological, and chemical, with an emphasis on the impact of prolonged operation and aggressive environmental conditions. Research shows that mechanical damage, such as spalling and potholes, significantly reduces the load-bearing capacity of structures and causes complex deformations. Relevant directions in scientific research have been identified, particularly regarding the behavior of damaged reinforced concrete beams under load, which require further development and improvement of methods for assessing residual load-bearing capacity. The article emphasizes the need for additional experimental studies and the use of modern software for more accurate methods of predicting and calculating reinforced concrete structures.

ANALYSIS OF SURFACE ROUGHNESS OF REFRIGERATIONCOMPRESSOR FRICTION NODES DUE TO INSUFFICIENTLUBRICATION

The article presents an attempt to evaluate the roughness profiles of the components of the friction nodes inrefrigeration compressors due to insufficient lubrication. The damaging impact on the compressor operationunder various unfavorable operating conditions, including with little or no lubricant at all, was analyzed for areal refrigeration system using a dedicated test stand.The Embraco Aspera NE9213GK refrigeration compressor used was originally filled in by the manufacturerwith a polyester lubricant; for the purpose of the study, the R407C lubricant was applied. An accelerateddamage-controlled procedure was carried out on the compressor by reducing the amount of lubricant insubsequent operating cycles of the system. The amount of oil was adjusted by removing lubricant duringshutdown periods using a dedicated spigot in the body of the semi-hermetic compressor casing. The testingcontinued until the refrigeration compressor seized up.The test stand was used to analyze electrical power measurements at the time of intentional damage tothe compressor caused as a result of forced absence of lubrication. Additionally, the authors analyzed surfaceroughness profiles of the compressor sliding elements prone to wear, including crankshaft journals, pistonsurface, and a cylinder surface.

Acceleration of Modeling Capability for GDI Spray by Machine-Learning Algorithms

Cold start causes a high amount of unburned hydrocarbon and particulate matter emissions in gasoline direct injection (GDI) engines. Therefore, it is necessary to understand the dynamics of spray during a cold start and develop a predictive model to form a better air-fuel mixture in the combustion chamber. In this study, an Artificial Neural Network (ANN) was designed to predict quantitative 3D liquid volume fraction, liquid penetration, and liquid width under different operating conditions. The model was trained with data derived from high-speed and Schlieren imaging experiments with a gasoline surrogate fuel, conducted in a constant volume spray vessel. A coolant circulator was used to simulate the low-temperature conditions (−7 °C) typical of cold starts. The results showed good agreement between machine learning predictions and experimental data, with an overall accuracy R2 of 0.99 for predicting liquid penetration and liquid width. In addition, the developed ANN model was able to predict detailed dynamics of spray plumes. This confirms the robustness of the ANN in predicting spray characteristics and offers a promising tool to enhance GDI engine technologies.

Research on Support Structure of Rectangular Cryogenic Infrared Lens with Large Aperture

This paper presents the design and optimization of a composite flexible support structure aimed at addressing the challenges associated with maintaining the positional accuracy and surface integrity of large-aperture cryogenic infrared lenses with long focal lengths. The primary objective of the structure is to maintain precise lens alignment while preserving the surface shape under operational conditions. The design complexities and underlying principles of the flexible support structure are systematically explored. A mechanical model of the flexible support structure was derived based on its structural characteristics, and the equilibrium equation was established to ensure the lens meets thermal deformation requirements in various directions. Optimization of key design parameters was conducted for a lens operating at 200 K, measuring 304 mm × 230 mm. The gravitational deformation of the optimized lens exhibited a root mean square (RMS) surface accuracy of 7.72 nm in the X direction, 7.08 nm in the Y direction, and 9.60 nm in the Z direction for lens surface 1. For lens surface 2, RMS values were 8.62 nm in the X direction, 8.41 nm in the Y direction, and 9.64 nm in the Z direction. At 200 K and lower temperatures, the RMS values of lens surfaces 1 and 2 were 2.41 nm and 2.74 nm, respectively, with a first-order mode frequency of 143.37 Hz.

Application of an Improved State Feedback Control in the Selective Catalytic Reduction Denitrification Systems of Coal Power Units Under Variable Load Conditions

Selective catalytic reduction (SCR) flue gas denitrification systems are inherently complex, typically embodying characteristics of non-linearity, significant time delays, and susceptibility to multiple disturbances. In the context of coal power units engaging in deep load cycling and rapid frequency adjustment, conventional proportional-integral-derivative (PID) control struggles to meet the demands of effective control. This study introduces a control strategy that incorporates a “state observer + Linear Quadratic Regulator (LQR) state feedback + Improved Quantum Genetic Algorithm (IQGA) optimized PID”. Initially, local linear mathematical models of an SCR denitrification system at 340 MW, 450 MW, and 540 MW loads were used to design state observer and LQR state feedback control parameters for each operational condition. At a single load point, the IQGA was employed to optimize the outer loop PID parameters, followed by simulation experiments of load increases and decreases between 340 MW and 540 MW. The results demonstrated that, compared to two other strategies, the proposed approach reduced the overshoot by a minimum of 1.5% and shortened the adjustment time by 31.7% under conditions of step disturbances and internal perturbations. Throughout variable operational conditions, the strategy consistently exhibited minimal output fluctuations, rapid adjustment capabilities, strong disturbance rejection, and robust stability. This algorithm proves to be an effective method for controlling NOx concentrations, offering insights for precise ammonia injection control in future applications.

SSO optimized FOFPID regulator design for performance enhancement of doubly fed induction generator based wind turbine system.

A wind turbine system (WTS) is a highly coupled and nonlinear system where the output power depends upon highly uncertain wind speed. Therefore, the quality of produced power becomes a challenging problem for researchers. Direct Vector Control (DVC) is a powerful and widely utilized power control strategy to deal with winds that vary rapidly and randomly. As a result, this article employed the newly developed Social Spider Optimization (SSO) technique to optimize the design parameters of Fractional-Order Fuzzy Proportional-Integral with Derivative (FOFPID) regulator to maintain the output power of the studied DFIG-based WTS at the rated value under dynamic wind conditions. The suggested FOFPID controller integrates the capabilities of the Fuzzy intelligent regulator and the Fractional-Order controller, enhancing DFIG current control while allowing independent control of active and reactive power. The approach is incorporated within the DVC strategy of the DFIG's rotor-side converter (RSC), replacing the conventional Proportional-Integral (PI) regulator in the internal current loops. Extensive performance evaluations are conducted under various operating conditions, including active power reference changes, parameter uncertainties, and rapid wind speed variations. Comparative analyses with SSO-optimized PID and Fuzzy regulators show that the FOFPID regulator performs better in terms of maximum overshoot, extreme undershoot, settling time, Total Harmonic Distortion (THD), and Weighted Total Harmonic Distortion (WTHD). The suggested FOFPID regulator also displays stronger robustness against parameters mismatch and weather change than other regulator architectures.

Low capacitor stress reconfigurable quadratic boost converter with fault tolerant capability for rooftop solar PV application.

Recently, many high-gain topologies have been derived. However, there is a need for a high-gain converter with fault-tolerant features. In this paper, a fault-tolerant reconfigurable quadratic boost converter is proposed for DC microgrid application. In this novel topology, 2-level redundancy is achieved by addressing the fault in the switch and capacitors. The operation of the converter in normal operating conditions and reconfiguration mode is discussed. The derived topology can achieve the same voltage gain even in the reconfiguration mode. The proposed topology exhibits better performance in the reconfiguration state. The voltage stress across the input and output capacitor is reduced in that state. The reliability analysis of capacitors in both states is carried out and compared with the aid of the reliability handbook. Finally, the topology operation in a normal and reconfiguration state is validated by building a 1-kW hardware setup. The results show that the quadratic boost converter in a reconfiguration state operates without altering the voltage gain of the converter and with reduced voltage stress across the capacitors.

Model Test on Thermomechanical Behavior of Deeply Buried Pipe Energy Pile Under Different Temperature Loads and Mechanical Loads

Deeply buried pipe energy pile (DBP-EP) offers the capability to harness geothermal energy from significantly deeper subterranean layers than those available inside buried pipe energy pile (IBP-EP). Despite its potential, there is a notable scarcity of research on the thermomechanical behavior of DBP-EP. This study meticulously observed the thermal variations in the soil surrounding the DBP-EP, the mechanical response of the pile itself, the earth pressure at the pile toe, and the displacement occurring at the pile’s top during the heating phase across various operational conditions. The findings show that for every 1 °C increase in inlet temperature, the temperature difference between the inlet and outlet increases by about 0.27 °C. The method of load application at the pile top during heating markedly influences the frictional resistance along the pile’s sides. Furthermore, When the pile top load rises from 0.26 kN to 0.78 kN, the observed vertical load at the pile foot decreases by 2.2–8.51%. This indicates that the increase in the pile top load reduces the downdrag effect on the sandy soil near the pile toe. This reduction subsequently diminishes the impact of vertical loads on the pile toe. Notably, after continuous operation for 8 h, the rate of increase in pile top displacement for DBP-EP shows a decline. Additionally, for every 1 °C rise in the inlet water temperature, the final displacement at the pile top diminishes by approximately 0.03‰D. This research endeavors to furnish a robust theoretical foundation for the structural design and practical engineering applications for DBP-EP.

A Ni4O4-cubane-squarate coordination framework for molecular recognition.

Molecular recognition is a fundamental function of natural systems that ensures biological activity. This is achieved through the sieving effect, host-guest interactions, or both in biological environments. Recent advancements in multifunctional proteins reveal a new dimension of functional organization that goes beyond single-function molecular recognition, emphasizing the need for artificial multifunctional materials in industrial applications. Herein, we have designed a porous Ni4O4-cubane squarate coordination polymer as an artificial molecular recognition host, drawing inspiration from the structural and functional features of natural enzymes. A comprehensive assessment of the material's ability to distinguish target species under different operating conditions was carried out. The results confirm its sieving function through hexane isomers separation, host-guest interaction function via xenon/krypton separation, and dual presence of sieving and interaction through carbon dioxide/nitrogen separation. Additionally, the material demonstrates good stability and feasibility for large-scale production, indicating its practical potential. Our findings provide a bio-inspired multifunctional recognition material for chemical separations as proof-of-concept while offering solutions to advance artificial multifunctional materials adaptable to other applications beyond chemical separations.

Centrifugal Compressor Surge in Innovative Heat Pump: Fluid Dynamic and Vibrational Analysis

Abstract In the current energy scenario, it is necessary to reduce fossil fuel consumption to achieve the far-sighted and stringent decarbonization goals. To date, heat is mainly produced through fossil fuels. Alternatively, electrically driven heat pumps can exploit renewable power to recover environmental and waste heat, offering energy efficient and environmentally friendly heating and cooling for applications ranging from domestic and commercial buildings to process industries. For this reason, they are expected to play a primary role in complementing or displacing natural gas boilers in the residential and industrial sectors in the near future. Centrifugal compressors are already used as prime movers of the working fluid in heat pumps, thanks to their industrial replicability, compact size, affordable costs, and good performance in terms of efficiency and low noise. However, they are subject to instabilities such as surge and stall like any other dynamic compressor and these phenomena develop quite differently than in classic open-loop systems such as gas turbines. In fact, such peculiarity is mainly due to the closed-loop configuration with real gases in two-phase conditions, occurring in typical heat pump cycles. In addition, heat exchangers also contribute to make these phenomena different from what is commonly studied. Compressor surge in closed-loop heat pump systems has received lower attention than other applications by the engineering community, lacking dedicated experimental characterization, and clear exposition of the phenomenon. The aim of this paper is to experimentally investigate the behavior of a centrifugal compressor installed into an innovative close loop heat pump system under stable and unstable conditions from both vibrational and fluid-dynamic points of view. The impact of the main process parameters on the evolution of the instability is shown, highlighting how surge cycles change by varying system operating conditions. The energy contents of surge cycles and pressure fluctuations are highlighted, using data postprocessing techniques such as fast Fourier transform and phase locked average. The vibro-acoustic analysis enrich the comprehension of the phenomena. The experimental results shown in this paper can be a basis for the future development of validated mathematical models of closed-loop heat pumps systems equipped with dynamic compressors operating under stable and unstable operating conditions.

Experimental Analysis of Long-Term Fuel Trim Performance in a Gasoline Engine Under Various Operating Conditions

This paper analyzes the effect of operating conditions on the enrichment of the fuel-air mixture in a car engine due to a decrease in air mass with increasing altitude above sea level. This study focuses on fuel trim, particularly long-term fuel trim, in optimizing the composition of the fuel-air mixture before it enters the engine's combustion chamber. Experimental studies were conducted on the Bishkek–Osh highway in the Kyrgyz Republic, a road characterized by flat, mountainous, and high-altitude sections with complex terrain. Based on the research objectives, experimental results were obtained, and graphs of long-term fuel trim as a percentage of terrain altitude were constructed and analyzed for flat, mountainous, and high-altitude sections of the Bishkek–Osh highway. The study established that fuel trim indicators can be used to analyze changes in the air-fuel mixture's air excess coefficient (λ = 1, stoichiometric ratio). The reduction in long-term fuel trim was observed in flat, mountainous, and high-altitude sections as air density and pressure decreased with increasing altitude above sea level. The results show that with a reduction in long-term fuel trim to -6.25% to -7.81% at altitudes between 1500 and 3000 meters above sea level, the air excess coefficient (λ) drops to 0.92–0.94. At an altitude of 770 meters (flat terrain), λ was measured at 0.97. The difference in λ (0.03–0.05) indicates that an increase in altitude significantly affects the air-fuel ratio (AFR), impacting mixture formation during vehicle operation in mountainous and high-altitude conditions.

Investigating the Reliability of Heating, Ventilation, and Air Conditioning Systems Utilized in Passenger Vehicles

A Heating, Ventilation, and Air Conditioning (HVAC) system is often utilized in passenger vehicles to enhance the comfort of both the driver and the passengers. The reliability of an HVAC system refers to the probability that a component within the system will fulfil its intended function during a specified timeframe while operating according to the predefined operational and environmental conditions. Conducting a reliability analysis for the HVAC system of a passenger vehicle is crucial to ensure safety, comfort, cost-effectiveness, and a positive standing. A methodology for analyzing the reliability analysis of a HVAC system using field failure data were developed to identify the critical failure modes, components, and subsystems. A detailed Pareto analysis was applied at subsystem and failure mode levels in order to prioritize them accordingly to their failure frequency. The analysis showed that the A/C evaporator and blower front sides were observed to be the most critical subsystems, contributing to approximately 50% of all failures. Furthermore, the leakages at the joints and vibrations are the primary failure modes of the HVAC system. The Weibull++ software package (version 2021) was used to estimate the best-fit probability distributions for each subsystem and system reliability modelling using a Reliability Block Diagram. The results show that the exponential distribution fits well for several subsystem’s Time-To-Failure (TTF) data and show that the failures were random and due to external reasons.

Mechanisms to support changeability during sustainment: Modularity, excess, and operations

AbstractComplex engineered systems face protracted design cycles and indefinite lifetimes, leading to discrepancies between expected and actual operating conditions. The field of design for changeability has focused on developing strategies to cope with these discrepancies. Literature has implicitly assumed that future changes can be predicted by system designers, but this assumption does not match observed reality. Often, systems must be modified in unexpected ways to maintain value, limiting the usefulness of standard change mechanisms. To understand how unexpected changes are implemented in practice, we studied the C‐130, a setting where one platform performed many missions, and close air support in Desert Storm, a setting where many platforms performed one mission. Through this examination, we find that excess and operator change are key mechanisms for changeability that have been largely ignored by literature. Excess can enable additions to systems without having to remove or swap subsystems out. It is also a critical enabler of modular changes during the operational phase. Operator changes are non‐form changes driven by system users who change how their systems are used to gain new capabilities rather than relying on changes to the form of the system. This paper also studies the relationship between these mechanisms to shed light on how changeability is achieved in practice, building the foundation for future work to study tradeoffs of implementing valuable excess during design.

Classical Batch Distillation of Anaerobic Digestate to Isolate Ammonium Bicarbonate: Membrane Not Necessary!

The excessive mineralization of organic molecules during anaerobic fermentation increases the availability of nitrogen and carbon. For this reason, the development of downstream processing technologies is required to better manage ammonia and carbon dioxide emissions during the storage and land application of the resulting soil organic amendment. The present work investigated classical distillation as a technology for valorizing ammoniacal nitrogen (NH4+-N) in anaerobic digestate. The results implied that the direct isolation of ammonium bicarbonate (NH4HCO3) was possible when applying the reactive distillation to the food waste digestate (FWD) with a high content of NH4+-N, while the addition of antifoam to the agrowaste digestate (AWD) was necessary to be able to produce an aqueous solution of NH4HCO3 as the distillate. The reason was that the extraction of NH4HCO3 from the AWD required a higher temperature (>95 °C) and duration (i.e., steady state in batch operation) than the recovery of the inorganic fertilizer from the FWD. The titration method, when applied to the depleted digestate, offered the quickest way of monitoring the reactive distillation because the buffer capacity of the distillate was much higher. The isolation of NH4HCO3 from the FWD was attained in a transient mode at a temperature below 90 °C (i.e., while heating up to reach the desired distillation temperature or cooling down once the batch distillation was finished). For the operating conditions to be regarded as techno-economically feasible, they should be attained in the anaerobic digestion plant by integrating the heat harvested from the engines, which convert the biogas into electricity.

Thermodynamic properties of non-azeotropic refrigerant heat pumps under full operating conditions with non-phase-change heat sinks and heat soucres

ABSTRACT When using pure refrigerants in heat pump, a significant temperature mismatch arises between hot and cold fluids within the evaporator and condenser, adversely impacting the thermal efficiency of system. To mitigate this issue, we incorporated non-azeotropic refrigerant blends such as R1233zd(e)/R152a, 1224 yd(z)/R152a and 1234ze(z)/R152a into heat pumps devoid of phase-change heat sinks and sources. Through rigorous examination of the temperature glide characteristics of these refrigerants, we determined an optimal R152a composition of 0.3, resulting in COPs of 3.326, 3.36, and 3.605 for the respective heat pumps. Our analysis further delved into heat pump configurations, revealing that the COP of the regenerative configuration could be substantially elevated from 3.36 (in the simple configuration) to 3.79. Additionally, the maximum temperature observed in the two-stage compression configuration was significantly lower compared to the regenerative setup. A comprehensive thermodynamic assessment = across all operating conditions indicated that COP of all configurations decreases markedly as heat production diminishes below 50% of full load. Conversely, when heat production exceeds 50% of full load, the COP remains relatively stable across different heat production levels. Notably, the COP of the regenerative configuration closely approximates that of the two-stage configuration. Considering factors such as investment cost, system complexity and operational efficiency, the regenerative configuration stands out as the optimal choice across all operating conditions.

Leakage prediction approach and influencing factor analysis from seal test

Purpose Leakage serves as a core indicator of sealing performance degradation, particularly under high-speed and heavy-duty operational where increased leakage is common. Within heavy-duty vehicle transmissions, the leakage can lead to excessive pressure loss and eventual transmission failure. This study aims to introduce a predictive method for assessing sealing ring leakage in vehicle transmissions based on operating conditions. Design/methodology/approach Seal test was carried out using a specialized seal test rig. Various data points were collected during this test, including leakage, friction torque, oil temperature, oil pressure and rotating speed. The collected data underwent noise separation and reconstruction using the complete ensemble empirical mode decomposition with adaptive noise method. Subsequently, a leakage prediction model is developed using the random forest regression with parameter optimization. A quantitative evaluation for influencing factors in leakage prediction process is investigated. Findings The results achieve a mean accuracy index exceeding 95%, demonstrating close alignment between predicted and actual leakage values. Feature contribution results highlight that the trends of the oil temperature, friction torque and oil pressure significantly affect the leakage prediction, with the oil temperature trend exerting the most substantial influence. Originality/value This work sheds light on the interplay between operating conditions and sealing performance degradation, offering valuable insights for understanding and addressing sealing issues effectively. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2024-0271/

Design of a Bubbling Fluidized Bed Reactor for Bio-oil Production from Sawdust

Due to the ever increase in energy demand, it becomes imperative to design appropriate reactor for the conversion of available raw materials to energy source such as bio oil. A fluidized bed reactor is one the most promising reactor for the conversion of biomass to bio-oil via pyrolysis. This work take into consideration the design of fluidized bed reactor and its subsidiaries (cyclone, filter, condenser and feed hopper) to be used for bio-oil production using sawdust as the feedstock. The operating conditions were temperature between 400-6000C, pressure 9.9atm and flow rate 1.86m/s. From the design calculations, it was found that the volume of the reactor, area, height, diameter and minimum fluidized velocity were 15.0796mm3, 5026mm2, 300mm, 80mm and 1.86m/s respectively. The material for construction for the reactor is stainless steel because of its high thermal conductivity and resistance to corrosion.

Enhancing Fuel Economy in Heavy-Duty Trucks: A Contemporary Approach

This article reviews the effect of load-based speed control (LBSC) and gear-down protection (GDP) features on fuel consumption in heavy-duty trucks. These two electronic features, developed by Cummins Inc., are major developments in the field of engine management for optimum fuel economy. LBSC controls engine speed based on operating conditions, while GDP encourages operation in top gear for maximum fuel economy. Their mechanisms, benefits, and combined impact on fuel consumption and driver behavior are discussed. The discussion also involves challenges and future developments in this field. Research indicates that LBSC and GDP can offer significant improvements in fuel savings, up to 7% improvement in fuel efficiency. LBSC and GDP contribute to cutting fuel consumption and serve as virtual driver trainers, contributing to more efficient driving behavior. This article concludes that LBSC and GDP are important tools that help fleet managers reduce operation costs and environmental impact within the trucking industry.

Assessment of the impact of intensification of heat exchange processes in heaters on power unit efficiency

In various spheres of modern industry, including power engineering, the issue of low efficiency of operation of heatexchange equipment, where condensation of vapour-gas media occurs, is a significant concern. It is known that one of the effective ways of solving this problem is intensification of heat exchange processes by transitioning from the traditional film condensation mode to the droplet condensation mode. A promising and technically straightforward way to achieve the droplet mode of condensation is a method based on the treatment of heat-exchange surfaces using a surfactant – octadecylamine (ODA). The analysis of studies, in which results of experimental research and industrial implementation are given, has shown that application of the specified method in conditions of condensation of water steam promotes formation of a stable droplet mode of condensation; as a result, the heat transfer coefficient on the steam side can more than double.Equally important and interesting is the question of how the efficiency of heat exchangers impacts the overall efficiency of complex systems, in which they operate. In this study, we examined the effect of the operational efficiency of network and regenerative heaters on the energy efficiency and economic performance of a power unit based on steam turbine unit T-110-12,8-3 operating in the heat recovery mode. To this end, we calculated the thermal scheme under various operating conditions of these heat exchangers and determined several key efficiency indicators, including the fuel heat utilisation factor (HUF) and electrical efficiency (EE). It is revealed that intensification of heat-exchange processes by a factor of 2 in horizontal delivery water heaters (HDWH) or in low-pressure heaters (LPH) significantly enhances the efficiency indicators of the power unit as a whole. At the same time, as the analysis of calculation results showed, the greatest benefits are realized when this measure is implemented in HDWH.

Behavior of plasma parameters under mirror and cusp magnetic fields in DC glow discharge – a numerical study

Abstract The plasma parameters in DC glow discharge can easily be controlled by externally applied magnetic field without disturbing internal / built-in process parameters. Though several works have been carried out to study the influence of the magnetic field at different configurations on the plasma parameters, a complete understanding on the behaviour of the plasma discharge under the mirror and cusp fields could not be achieved. Further studies on the same are needed to improve the efficiency of the DC glow discharge system for existing applications and to find the new applications. In this work, a 2D axis-symmetric non-equilibrium plasma model with drift-diffusion approach is developed to study the characteristics of the plasma in DC glow discharge through various plasma parameters under mirror and cusp fields. The effects of current and position of magnetic coils on electric potential, ionization rate, electron temperature and electron number density are predicted and discussed. The distribution of electron number density at various coil currents and positions under both mirror and cusp fields are presented and the operating conditions favorable for applications in surface modification are suggested.