Effects Of Key Design Parameters Research Articles

Analysis of Transient Thermoacoustic Characteristics and Performance in Carbon Nanotube Sponge Underwater Transducers.

Recent advancements in marine technology have highlighted the urgent need for enhanced underwater acoustic applications, from sonar detection to communication and noise cancellation, driving the pursuit of innovative transducer technologies. In this paper, a new underwater thermoacoustic (TA) transducer made from carbon nanotube (CNT) sponge is designed to achieve wide bandwidth, high energy conversion efficiency, simple structure, good transient response, and stable sound response, utilizing the TA effect through electro-thermal modulation. The transducer has potential application in underwater acoustic communication. An electro-thermal-acoustic coupled simulation for the open model, sandwich model, and encapsulated model is presented to analyze the transient behaviors of CNT sponge TA transducers in liquid environments. The effects of key design parameters on the acoustic performances of both systems are revealed. The results demonstrate that a short pulse excitation with a low duty cycle could greatly improve the heat dissipation of the encapsulated transducer, especially when the thermoacoustic response time becomes comparable to thermal relaxation time.

Erratum: Optimization of Dynamic Performance of a Solenoid Actuator in a CNG Injector Based on the Effects of Key Design Parameters

Erratum: Optimization of Dynamic Performance of a Solenoid Actuator in a CNG Injector Based on the Effects of Key Design Parameters

The investigation of thermo-economic performance for dry-cooled closed Brayton cycle coupled to nuclear microreactors using different coolants

Dry-cooled closed Brayton cycle (CBC) coupled to gas-cooled nuclear microreactors offers a compact structure and can be deployed in water-deficient areas. The gas-cooled reactor utilizes coolants including supercritical carbon dioxide (S–CO2), helium, and He–Xe mixture. The choice of working fluids for CBC strongly affects its size and performance, where smaller plant sizes, higher thermal efficiency, and lower investments are preferred. This study investigates the thermo-economic performances of dry-cooled CBC coupled to nuclear microreactors using different coolants. A design method for dry-cooled CBC is developed based on the integration of thermodynamic modeling and component preliminary design. Baseline designs are first established, followed by an analysis of the effects of key design parameters. Furthermore, a multi-object optimization is conducted to compare the Pareto frontiers of CBC using different working fluids. The results demonstrate that the helium simple cycle exhibits superior efficiency and precooler size due to its higher reactor outlet temperature, though with a larger capital cost. The Pareto frontier of the He–Xe cycle is worse than that of the helium cycle. The S–CO2 recompression cycle has a comparable efficiency with a smaller capital cost at mediate reactor outlet temperatures but suffers from large precooler sizes. The findings revealed that the S–CO2 recompression cycle is a more promising choice if the reactor outlet temperature can be further elevated.

A spectral splitting CPV/T hybrid system based on wave-selecting filter coated compound parabolic concentrator and linear Fresnel reflector concentrator

Efficient full-spectrum solar energy utilization shows great potential to improve solar energy conversion efficiency. In this paper, a spectral splitting concentrated photovoltaic/thermal hybrid system based on a wave-selecting filter-coated compound parabolic concentrator and linear Fresnel reflector mirror field is developed. Optical models to simulate the linear Fresnel reflector have been developed and validated. With the wave-selecting filter coated compound parabolic concentrator, the visible and near infrared spectra transmit onto the photovoltaic cells, while the rest are reflected to the receiver tube. Furthermore, a simplified receiver indoor test prototype is designed to investigate the characteristic of solar photovoltaic module with the spectral filter in the context of the compound parabolic concentrator. The measured I–V curves are compared with the modeled results. Additionally, the thermodynamic performance of the system is analyzed. Parametric studies are performed to investigate the effect of key design parameters including the mirror width, focal length and the radius of the receiver tube on the solar flux density and the exergy efficiency. An exergy efficiency of 35.51% and an optical efficiency of 94.78% are achieved. With a preliminary techno-economic analysis, the levelized cost of the electricity of the system is $0.209/kWh with a payback period of 10 years.

Novel multi-scale experimental approach and deep learning model to optimize capillary pressure evolution in early age concrete

Early-age shrinkage of concrete can initiate pre-mature cracking, which can compromise the durability of concrete structures. Monitoring capillary pressure, the leading cause of concrete shrinkage, and understanding its evolution is crucial for the performance-based design of concrete, particularly at early-stages when it is more prone to cracking. This study deploys an innovative multi-scale experimental program using high-capacity tensiometers to monitor the capillary pressure up to 2000 kPa. This allowed investigating the effects of key design parameters, including the water-to-cement ratio, GGBS, SRA, and measurement depth, on the capillary pressure evolution in concrete. A new robust deep neural network model was developed to conduct extensive numerical experiments to predict the capillary pressure evolution of diverse mixtures. The net effect of multi-parameters on the capillary pressure can be investigated with this model, providing insights into the optimum design of more durable concrete mixtures with the lowest capillary pressure evolution, and guiding the implementation of appropriate cost-effective shrinkage-mitigating strategies.

Optimization of Dynamic Performance of a Solenoid Actuator in a CNG Injector Based on the Effects of Key Design Parameters

Optimization of Dynamic Performance of a Solenoid Actuator in a CNG Injector Based on the Effects of Key Design Parameters

Aerodynamic Analysis of a Logistics UAV with Foldable Bi-wing Configuration

Herein, a twin-boom, inverted V-tailed unmanned aerial vehicle (UAV) featuring a foldable bi-wing configuration is proposed for logistics and transportation applications. We employed the Navier–Stokes solver to numerically simulate steady, incompressible flow conditions. By examining the effects of key design parameters on aerodynamic characteristics and bypass flow fields in a two-dimensional state, we were able to suggest a more optimized foldable wing design. Building on the two-dimensional analysis, we performed aerodynamic assessments of the three-dimensional aircraft geometry. Our results indicated that appropriate wing and gap parameters can significantly enhance lift characteristics, maintaining high lift even during large-angle flights. Specifically, when compared to a mono-wing, the lift coefficient of the bi-wing increased by 27.1% at a 14° angle of attack, demonstrating the effectiveness of our wing-and-gap design. Optimal aerodynamic performance was achieved when the gap distance equalled the chord length in both flow and vertical directions. Further, the right combination of airfoil configuration, wing axes angle, and wingspan can improve flow field aerodynamic characteristics, while also enhancing the wing’s stall capacity. The lift coefficient reached its maximum value at an angle of attack of 15°, which has the potential to reduce takeoff and landing distances, thereby enhancing the UAV’s overall safety.

Wind tunnel experiments of bending-torsion and body-freedom flutter on flying wing unmanned aerial vehicles

Wind tunnel experiments are performed on a flying wing model to investigate the effects of key design parameters and their cross-interactions on the flutter speed and frequency for bending-torsion flutter (BTF) and body-freedom flutter (BFF). These design parameters include wing sweep angle, mass of tip weights, and location of weights along the wingspan. A slider and rail setup for BFF is designed to enable rigid-body pitching and plunging degrees-of-freedom, while a custom fixed clamp is used to perform the BTF experiments. BTF and BFF experiences different dominant modes while undergoing flutter, with the former's dominant mode being torsion and the latter being the rigid-body short-period mode. For BTF, flutter speeds increase as weights are moved towards the wingtip or increasing tip weights, which increases the inertia of the system to enhance stability. The effect is opposite for BFF as the movement of weights outboard or increase of tip weights result in a rearwards shift of the centre of gravity that destabilises the system. In general, a higher sweep angle leads to increased sensitivity of flutter speeds to changes in mass of tip weights or changes to spanwise location of the weights. The findings from this study provide insights to the design of flying wing unmanned aerial vehicles for increased stability margins.

Block shear failure of austenitic stainless steel bolted connections

Austenitic stainless steel possesses very high ductility and ultimate-to-yield strength ratio, which could possibly affect the block shear failure mechanism and the corresponding ultimate capacity of bolted connections made of this material. In response to this concern, a comprehensive experimental and numerical study on the block shear behaviour of austenitic stainless steel bolted connections (ASSBCs) is conducted and reported in this paper. Based on the results of 15 experimental tests, it is found that the governing block shear mechanism of ASSBCs (for 14 out of the 15 tests) at the ultimate load corresponds to cracking of the shear sections prior to fracture of the tensile sections. This differs significantly from the conventionally accepted block shear mechanism of mild steel bolted connections, which is net section fracture of the tension area and yielding of the shear area. This observation was further confirmed by a numerical study based on validated finite element models, where three block shear mechanisms were identified for ASSBCs. A thorough parametric study was then carried out to clarify the effects of key design parameters on the block shear behaviour of ASSBCs. Finally, the experimental and numerical results are used to evaluate the applicability of existing design equations to predicting the block shear capacity of ASSBCs. An improved block shear equation is subsequently proposed based on the available data.

Experimental investigation on the hydrodynamic performance of a pile-supported OWC-type breakwater

The present study considers the design optimisation of an Oscillating Water Column (OWC) incorporated into a pile-supported breakwater structure. This has been achieved by performing a substantial number of scaled physical model tests and a methodical variation of key device parameters within multiple configurations. The key aspects that have been investigated include: (a) the geometric characteristics of the breakwater structure, (b) the pneumatic efficiency of the OWC, (c) the geometry of the OWC chamber and (d) the relative position of the OWC chamber within the breakwater. The present work considers (monochromatic) regular waves of varying steepness and effective water depth as incident wave conditions. The efficiency of the designed structure in terms of shore protection capacity and wave energy extraction was assessed by quantifying relevant transmission coefficients and the power output metrics. This has been achieved by using a combination of collocated and complementary measuring devices, such as arrays of wave gauges, pressure transducers and a high-definition video camera. The study concluded that systematic refinement of the geometrical parameters can substantially enhance the overall hydrodynamic efficiency of a pile-supported OWC breakwater. Additionally, it was found that a configuration featuring a chamber positioned in front of the breakwater, with a relative chamber breadth of 0.67, outperforms wider breadth configurations in terms of both energy extraction efficiency and reduction of the transmission coefficient. Taken together, the present study provides an in-depth analysis of the effects of key design parameters of a breakwater-integrated OWC, its efficiency and shore protection potential.

Deformation and force characteristics of double-cable suspension bridges

A double-cable suspension bridge has broad application prospects. As a kind of suspension bridge, it is a flexible structure with small overall stiffness, structural deformation induced by live loads is a major concern in the design of double-cable suspension bridges. Deformation and force characteristics of double-cable suspension bridges were studied in this paper, a theoretical analysis method is proposed for calculating the main cable’s horizontal force increment and vertical deformation under live load (concentrated and half-span uniform loads) of the double-cable system. Finite element models (FEMs) were established to verify the proposed formulas, and the comparison of formula solutions with FEM solutions revealed good agreement. The effects of key design parameters on the force and deformation were studied; and the deformation and force characteristics of double-cable suspension bridges were compared with those of traditional single-cable suspension bridges. Results showed that the ratio of the horizontal force increments of the two cables caused by the live load is mainly determined by the sag-to-span ratio of these cables. The sag-to-span ratio and the proportion of dead load distributed to the double cables affect the main cable deflection. Increasing the proportion of dead load borne by the top cable or reducing the sag-to-span ratio can increase the gravity stiffness of a double-cable system.

Design and characteristic analysis of flexible CNT film patch for potential application in ultrasonic therapy

Ultrasonic therapy has drawn increasing attention due to its noninvasiveness, great sensitivity and strong penetration capabilities. However, most of traditional rigid ultrasonic probes cannot achieve a solid interfacial contact with irregular nonplanar surfaces, which leads to unstable therapeutic effects and limitations of widespread use in practical applications. In this paper, a new flexible ultrasonic patch based on carbon nanotube (CNT) films is designed and fabricated to achieve a potential application in ultrasonic therapy. This patch is composed of a CNT film, a thermal protective layer and a heat sinking layer, and has the advantages of simple structure, soft, ultrathin and completely conforming to the treatment area. Theoretical and experimental studies are performed to investigate the acoustic and temperature fields before and after deformation. Effects of key design parameters of the patch on acoustic performances and temperature distributions are revealed. Numerical results indicate that the CNT film patch can produce ultrasounds over a wide frequency range and temperatures under the threshold of burn injury whether it is bent or not. Furthermore, it is also noted that the sound waves emitted from the bending patch are focused at the center of the bending patch, which demonstrates that the target treatment area can be controlled.

Численный анализ влияния относительного продольного и поперечного шагов на характеристики потока шахматного пучка труб каплевидной формы

The present work has been conducted to clarify flow behavior across staggered drop-shaped tubes bundle at various longitudinal and transversal pitch ratios (the tubes bundle configures in 18 cases). The investigation covers the effects of key design parameters of Reynolds numbers Re = (1.78--18.72) · 103, longitudinal pitch ratios (PL = 1.44, 1.54, 1.64, 1.74, 1.84 and 2.04) and transversal pitch ratios (PT = 1.24, 1.44, 1.64 and 1.82). ANSYS Fluent software package is used to predict the flow pattern around tubes. The results of this study showed that at a constant longitudinal pitch ratio, the minimum friction factor varies with the Reynolds number and transversal pitch ratio. As the Re increases, the friction factor decreases. The minimum values of the friction factor were achieved for (PL = 1.24 and PT = 1.44) at Re = 1.78 · 103, and (PT = PL = 1.64) at Re > 1.78 · 103. Correlation of the friction factor for the studied models were presented

Axial mechanical behavior of innovative inter-module connection for modular steel constructions

Modular steel construction (MSC) is a construction mode where volumetric modules are prefabricated in a factory and assembled on-site to form permanent buildings. Inter-module connections are critical to the integrity and robustness of modular steel constructions (MSCs). In this paper, the mechanical behavior of a typical corner inter-module connection under axial tensile and compressive loads was investigated. A tensile test of the inter-module connection was carried out to investigate their axial tensile behavior. The refined numerical model was established, calibrated against the test results and then used to simulate the axial tensile and compressive mechanical behaviors of the inter-module connection. The effects of key design parameters on the axial load-displacement responses of the connection, including the bolt gasket thickness, the bolt diameter and the preload were investigated. The inter-module connection was shown to exhibit excellent load-carrying capacity under axial compression and adequate performance under tension. In terms of tensile resistances, the bolt gasket thickness and the bolt diameter were shown to be the critical parameters, while the section size of the modular columns dominated the compressive load-carrying capacity. Through geometrical parameters correlation analysis, a simplified piecewise polynomial axial load-displacement model with different stiffnesses in tension and compression was employed for predicting the axial load-displacement relationship. The proposed model was shown to be capable of accurately capturing the axial resistance characteristics of the connection while maintaining simplicity, and is therefore recommended for use to represent the axial behavior of the inter-module connection in global frame modelling.

Study on the Effect of Radiant Insulation Panel in Cavity on the Thermal Performance of Broken-Bridge Aluminum Window Frame

Windows have a great impact on building energy consumption, and the thermal performance of window frames directly affects its energy-saving potential. In this paper, a novel method is proposed to optimize the thermal performance of commercially available broken-bridge aluminum window frames, by incorporating radiant insulation panels (RIPs) into the window frame cavity. A typical aluminum alloy window frame heat transfer model is theoretically analyzed and validated, and the effects of key design parameters on the equivalent thermal conductivity (ETC) of the cavity radiation heat transfer and the heat transfer coefficient (U-factor) of window frames are quantitatively analyzed by a finite element simulation method using the THERM software. Moreover, the RIP, the insulation material filling, and low surface emissivity on the thermal performance of the window frame are compared and analyzed. The results show that the RIP is better placed in the middle, the width and quantity of RIPs are negatively correlated with the U-factor, while the surface emissivity of RIPs is positively correlated with the U-factor. Adding RIPs in the cavity can reduce the U-factor of the window frame by more than 7.43%, slightly lower than 8.97% for the filling type, but significantly higher than 0.81% for the low-emissivity type. Inserting RIPs is a simple and effective way to reduce the U-factor of the window frame and have a great potential of use.

Numerical study of a novel SMA-based self-centering beam-to-column connection

As an alternative option for conventional rigid beam-to-column welded connections, self-centering steel beam-to-column connections were developed to reduce or eliminate the residual deformation of the structure and mitigate or avoid structural damages. This paper presents a finite element analysis of a novel self-centering beam-to-column connection with shape memory alloy (SMA) tendons as recentering and energy dissipation elements and comb-teeth dampers (CTDs) as supplementary energy dissipation devices. Firstly, the configuration and structural behavior of the proposed connection is depicted and explained; then, with the aid of previous experimental models, the validation of finite element modeling methods is examined. In the following, detailed numerical models are established and analyzed to assess the effects of key design parameters on the cyclic behavior of the proposed connection. Finally, an analytical model is formulated to predict the whole cyclic behavior of the proposed system. The results indicate a great recentering and energy dissipation capacity for the proposed connection. It is shown that incorporating CTDs in the proposed connection can significantly enhance the cyclic response of the connection with roughly no adverse impact on self-centering ability. It is also concluded that there must be an adequate initial prestress in SMA tendons to exploit the maximum recentering ability of the proposed connection. Furthermore, comparing the structural performance metrics of the proposed connection reveals that the connections with higher damper geometric shape coefficients own higher ultimate strength and better energy dissipation capacity with almost unchanged recentering capability. Conversely, the longer the damper teeth height is, the lower performance parameters in the connections could be observed. Results also show reasonable concordances between the analytical model predictions and finite element analysis results. The results of this study can serve as tools to facilitate the practical design of SMA-based self-centering connections.

Efficient Sensitivity Analysis for Enhanced Heat Transfer Performance of Heat Sink with Swirl Flow Structure under One-Side Heating

Excellent heat transfer performance has increasingly become a key issue that needs to be solved urgently in the development process of large-scale fusion equipment. The study of heat transfer performance improvement to scientifically and reasonably determine the design parameters of the high heat flow (HHF) components of fusion reactors based on the efficient in-depth analysis of the heat transfer mechanism and its sensitive factors is of great significance. In this paper, a liquid-vapor two-phase flow model with subcooled boiling for a large length-diameter ratio swirl tube structure in the HHF calorimeter component is proposed to analyze the effects of key design parameters (such as inlet temperature of cooling water flow, swirl tube structure parameters, etc.) on its heat transfer performance. Then, considering the high computational cost of the liquid-vapor two-phase flow model, and in order to improve the efficiency of the sensitivity analysis of these design parameters, the polynomial response surface surrogate model of heat transfer performance function was constructed based on Latin hypercube sampling. On this basis, by combining the proposed surrogate model, the sensitivity index of each design parameter could be obtained efficiently using the Sobol global sensitivity analysis method. This method could greatly improve the calculation efficiency of the design parameter sensitivity analysis of HHF components in the fusion reactor, which provides vital guidance for the subsequent rapid design optimization of related components.

Влияние относительного продольного и поперечного шага на характеристики потока шахматного пучка каплевидных труб

The present work has been conducted to clarify flow behavior across staggered drop-shaped tubes bundle at various longitudinal and transversal pitch ratios (the tubes bundle configures in 18 cases). The investigation covers the effects of key design parameters of Reynolds numbers Re = (1,78–18,72)  103, longitudinal pitch ratios (PL = 1,44, 1,54, 1,64, 1,74, 1,84 and 2.04) and transversal pitch ratios (PT =1,24, 1,44, 1,64 and 1,82). ANSYS Fluent software package is used to predict the flow pattern around tubes. The results of this study showed that at a constant longitudinal pitch ratio, the minimum friction factor varies with the Reynolds number and transversal pitch ratio. As the Re increases, the friction factor decreases. The minimum values of the friction factor were achieved for (PL = 1,24 and PT = 1,44) at Re = 1,78  103, and (PT = PL = 1,64) at Re > 1,78  103. Correlation of the friction factor for the studied models were presented.

Effect of key design parameters on high temperature performance of asphalt mixtures

• Four key design parameters were selected to study their effect on the high temperature performance of asphalt mixtures. • The uniaxial penetration shear test was applied to analyze the variation of high temperature performance of asphalt mixtures. • The multi-way (one way and two-way) ANOVA was adopted to understand the role of factors on the high temperature performance of asphalt mixtures. Rutting is one of the main distresses for asphalt pavements and it has adverse effect on service life. It is associated with the high temperature performance of asphalt mixtures. The paper attempts to investigate the effect of key design parameters on high temperature performance of asphalt mixtures. Initially, the factors consisting of air void ratio, compaction effort, maximum nominal particle size and asphalt binder grade were selected and then the uniaxial penetration shear test was applied to analyze the variation of high temperature performance of asphalt mixtures. Accordingly, the maximum penetration load and the shear strength were used as evaluating indicators. Eventually, the multi-way (one way and two-way) ANOVA was adopted to understand the role of factors on the high temperature performance. The results indicate that the high temperature performance increases an average of 30 % when compaction effort and maximum nominal particle size rise. In contrast, the raise of asphalt grade and air void ratio decrease of 10 %∼30 % of high temperature performance. At the same time, the increase of compaction effort improves the high temperature performance about 20 %∼50 % at two variables condition. In one-way ANOVA, there is no statistically significant difference in the maximum penetration load when changing the air void ratio levels. The compaction effort, maximum nominal particle size, asphalt binder grade significantly influence the change of maximum penetration load. In terms of two-way ANOVA, any combined two factors significantly affect the high temperature results. This provides some guidance for design of asphalt mixtures to elevate high temperature performance.

Techno-economic assessment of integrated spectral-beam-splitting photovoltaic-thermal (PV-T) and organic Rankine cycle (ORC) systems

Promising solar-based combined heating and power (CHP) systems are attracting increasing attention thanks to the favourable characteristics and flexible operation. For the first time, this study explores the potential of integrating a novel spectral-beam-splitting (SBS), hybrid photovoltaic-thermal (PVT) collector and organic Rankine cycle (ORC) technologies to maximise solar energy utilisation for electricity generation, while also providing hot water/space heating to buildings. In the proposed collector design, a parabolic trough concentrator (PTC) directs light to a SBS filter. The filter reflects long wavelengths to an evacuated tube absorber (ETA), which is thermally decoupled from the cells in the PVT tube, subsequently enabling a high-temperature fluid stream to be provided by the ETA to an ORC sub-system for secondary power generation. The SBS filter’s optical properties are a key determinant of the system’s performance, with maximum electricity generation attained when the filter transmits wavelengths between 485 and 860 nm onto the PVT tube, while the light outside this range is reflected onto the ETA. The effect of key design parameters and system capacity on techno-economic performance is investigated, considering Spain (Sevilla), the UK (London) and Oman (Muscat) as locations to capture climate and economic impacts. When operated for maximum electricity generation, the combined system achieves a ratio of heat to power of ∼1.3, which is comparable to conventional CHP systems. Of the total incident solar energy, 24% and 31% is respectively converted to useful electricity and heat, with 54% of the electricity being generated by the PV cells. In Spain, the UK and Oman, respective electricity generation of 1.8, 0.9 and 2.1 kWhel/day per m2 of PTC area is achieved. Energy prices are found to be pivotal for ensuring viable payback times, with attractive payback times as low as 4–5 years obtained in the case of Spain at system capacities over 2.7kWel. Integrating the ORC sub-system with the concentrating SBS-PVT collector design reduced the levelised cost of electricity (LCOEel). A LCOEel of 0.10 £/kWh is attained in Spain at an electrical capacity of only 4 kWel, demonstrating the significant potential of exploiting the proposed systems in practical applications, as highly competitive with established combustion-based CHP systems.