Supply Pressure Research Articles

Performance analysis of sodium alanate hydride reactor with different nanofluids

The thermal management of the hydride based hydrogen storage reactor is the key factor to realize the complete storing potential of hydrides. In this regards a hydride reactor filled with sodium alanate in multiple tubes is numerically analyzed for absorption process. Based on various governing equations, a mathematical model of hydride reactor is developed and validated with the help of ANSYS Fluent. The hydride reactor uses mainly water or oil for heat exchange during hydrogen sorption. In the present study conventional heat transfer fluid (HTF) is replaced with the nanofluid since it has a greater heat exchange properties. The CuO/HTF, Al2O3/HTF and MgO/HTF nanofluids are selected based on previous studies and results of numerical experiment are recorded. The outcomes are attained for various parameters such as material and concentration of nanoparticles, supply pressure of hydrogen and inlet temperature of heat exchange fluid. The CuO/HTF nanofluid with concentration of 5 vol% exhibited better rate of absorption in comparison with other vol% concentrations and other selected nanofluids. It shows improvement in hydrogen absorption time up to 14% under selected conditions. Additionally, it is observed that CuO/HTF nanofluid with 5 vol% concentration is thermodynamically superior to other selected nanofluids; as a result it enhances the rate of the heat exchange up to 10% for hydride reactor. It is realized that the performance of CuO/HTF nanofluid with 5 vol% concentration is superior among picked nanofluids. Therefore for the hydride reactor the use the nanofluid is advantageous.

Loop-seal flow characteristics of a circulating fluidized bed for 3 MWth scale chemical looping combustion system

This study aimed to provide a design and operational approach for a loop-seal, which is the heart of a circulating fluidized bed (CFB). Thousands of CFB systems use this non-mechanical valve to optimize performance by controlling the solids circulation rate while preventing gas mixing between reactors. Nevertheless, its design and operating guidance remains unclear because of its intricate flow characteristics, causing confusion in design and operation of the entire CFB. This study experimentally investigated the three most important elements while designing and operating loop-seal: conditions for initiating solids flow, the maximum obtainable solids flow rate, and quantitative control of solids flow rate. Experiments were conducted in a CFB, which simulated 3 MWth chemical looping combustion (CLC) system that is currently being developed. The onset of solids flow occurs when the gas drag force in horizontal passage overcomes the resistance force generated by the bed of particles. The maximum solids circulation rate was determined by solids height in the supply chamber and pressure around CFB loop. A correlation for quantitative control of solids flow in loop-seal was proposed by the relationship between the gas drag force and particle velocity. Finally, operational conditions for the loop-seal in 3 MWth CLC were proposed.

The Direct-Coupling Method for Analyzing the Performance of Aerostatic Bearings Considering the Fluid–Structure Interaction Effect

In the interest of analyzing the effect of the structural deformation root caused by gas pressure on the static features of aerostatic bearings, a fluid–structure interaction (FSI) model based on orifice-type aerostatic bearings is proposed that can predict the characteristics of aerostatic bearings more accurately by using the direct-coupling method (DCM). By using COMSOL Multiphysics, the governing equation matrix of the finite element model of structural deformation and gas film pressure was solved with the integral solution method, and the orifice boundary conditions were calculated with the root iteration method. At the same time, the static performance of I-shaped orifice-type aerostatic bearing with various supply pressures was analyzed theoretically and tested experimentally. The results show that in comparison with the calculation results without taking account of structural deformation, the theoretical values from the model derived in this paper considering the FSI effect are closer to the experimental values. Finally, by using the orthogonal design method, FSI simulation was carried out to analyze how the key dimension factors influence the structural stiffness of the spindle, and it is concluded that the thrust bearing’s stiffness is strongly influenced by the thickness of the thrust plate.

Flow Analysis of a Novel, Three-Way Cartridge Flow Control Valve

Flow control valves are designed to maintain a constant flow rate regardless of pressure changes. However, standard, two-way design may cause significant energy losses due to the need to maintain high pressure in the supply line. In contrast, the proposed three-way valve allows the required flow rate to be obtained at a supply pressure slightly above the loading pressure. This work included building mathematical and simulation models, conducting numerical simulations in Ansys/Fluent and Matlab/Simulink environments, and verifying the results by initial test bench experiments on a valve prototype. The main contribution provided by the work concerns the proposal of a new valve solution and the estimation of its operational characteristics.

Analysis of Circulation Characteristics and Heat Balance of High-Speed Rolling Bearing under Oil-Air Lubrication

Aiming to solve the problem of oil-air lubrication failure caused by the high working temperature of high-speed rolling bearings, this study proposes a method, based on the theory of gas-solid two-phase flow and bearing tribology, of predicting the dynamic temperature rise of nonlinear high-speed rolling bearings under oil-air lubrication conditions. The accuracy of the fluid–structure coupling model is verified by comparing the temperature rise test results of angular contact ball bearing at different speeds. The characteristics of oil-air lubrication circulation and the relationship between the lubrication parameters and the heat balance of the high-speed rolling bearings have been studied. The results show that the gas supply pressure of the system has a significant influence on the continuity and fluctuation of the oil film in the oil pipe nozzle. The initial rise in temperature of the inner and outer rings of the bearing and the fluid domain has a speed threshold value, and the temperature increases linearly with the bearing speed. With the increase in the oil supply and lube oil viscosity of the system, the temperature rise of the outer ring of the bearing increases first, then decreases, and finally increases again. There is an optimal oil supply 5.5 mL and optimize viscosity 68 cSt for the bearing in the work condition.

The Influences of Different Parameters on the Static and Dynamic Performances of the Aerostatic Bearing

Aerostatic bearings have been widely applied to high-rotating speed machines due to their low friction and high rotational speed advantages. The geometry parameters, supply pressure and rotational speed play important roles in the static and dynamic performances of the aerostatic bearings. In this paper, the steady state and dynamic Reynolds equations are solved by the finite difference method (FDM) and used to study the static and dynamic performances of the aerostatic bearings. Then, combined with the motion equation of the rigid rotor-aerostatic bearing system, the linear stability of the aerostatic bearing is also studied. Moreover, based on the theory mentioned above, the influences of the geometry parameters (such as orifice diameter, radial clearance and eccentricity), rotational speed and supply pressure are investigated in detail. It was found that aerostatic bearing geometries, rotational speed and supply pressure had a significant effect on the steady and dynamic performances. Under the low-speed conditions and high supple pressure, the static pressure effect plays the main role in the performances of the aerostatic bearings, while on the contrary, the rotational effect plays the main role. Furthermore, a half-speed whirl may generate under certain conditions. The results also provide useful design guidelines for aerostatic bearings in high-speed machines.

Performance optimization of metal hydride hydrogen storage reactors based on PCM thermal management

Metal hydrides (MH) are considered promising hydrogen storage materials. In applications, the heat transfer characteristics of MH hydrogen storage reactors are closely related to their storage performance. Phase change materials (PCM) were proven to integrate with MH reactors for effective thermal management. Nevertheless, the PCM based MH reactors (MH-PCM reactors) still need to overcome the heat transfer resistance and the loss of volumetric hydrogen storage capacity caused by the PCM volume proportion. The present work established a mathematical model to describe the transfer and reaction process in the MH-PCM reactor. Various parameters were discussed in the current work. It was found that the increased PCM's amount and latent heat have a restricted effect on the enhancement of heat transfer and absorption reaction rate. The higher PCM's thermal conductivity and hydrogen supply pressure effectively enhanced the heat transfer and reaction rate. Furthermore, the increased absorption pressure can improve PCM's sensible heat storage capacity, which provides a new approach for optimizing PCM consumption. Finally, the quantitative relationship among the volumetric hydrogen storage capacity, the volume fraction and thermophysical properties of PCM, and the absorption pressure were established by systematic analysis, which provides an essential theoretical basis for the optimization of MH-PCM reactors.

Design and experiment of a new double needle type piezoelectric jetting dispenser

To improve the performance of piezoelectric (PZT) jetting dispensers in the electronic packaging industry and address the problems of oversized, easily fatigued elastic hinges and low repetition accuracy of conventional PZT jetting dispensers with a compliant mechanism-based lever, a new double needle PZT jetting dispenser prototype was developed. The advantage of the proposed structure over compliant mechanism-based lever was demonstrated by dynamics analysis. Firstly, the design stroke of the needle and the modal state of the dispenser body were analyzed using ANSYS. Secondly, the theoretical model of adhesive injection was established, the fluid pressure change process inside the nozzle during the working cycle of the jetting dispenser was simulated using Fluent, and the effects of the supply pressure and needle stroke on the injection speed of the droplet were investigated. Finally, a test bench was built to conduct the experiment, and the results showed that the supply pressure and the driving signal duty cycle between 20% and 80% were positively correlated with the size of droplet diameter, whereas the driving signal frequency was negatively correlated with the droplet diameter, thereby validating the proposed adhesive injection model. Under the experimental conditions, the highest operating frequency of the designed PZT jetting dispenser was 400 Hz, which is close to the high-frequency level of existing studies, and the minimum droplet diameter obtained was 0.36 mm, which is 0.1–0.2 mm less than that of the existing PZT jetting dispenser with a compliant mechanism drive, meeting the industry requirements for the working performance of a PZT jetting dispenser.

Origami-Inspired Soft Pneumatic Actuators: Generalization and Design Optimization

Soft actuators are essential to soft robots and can also be used with rigid-bodied robots. This paper is focused on methods for improving the applicability of origami-inspired soft pneumatic actuators (OSPA). Our method for rapidly fabricating OSPA is shown to be capable of making a range of actuator sizes out of different materials. The largest OSPA has a force-to-weight ratio of 124, and can lift a 44 kg mass using a −85 kPa supply pressure. Experiments with a smaller OSPA demonstrate that it can perform 150,000 contraction/extension cycles while carrying a 2 kg mass with minimal degradation due to its materials and design. Compared to other OSPAs for which fatigue tests were reported, our accordion pattern OSPA has the best values of work-to-mass ratio, max. force, and fatigue life. A computationally efficient FEA-based constrained optimization method for maximizing an OSPA’s work output is then proposed. A 55% improvement in the work output was predicted, while validation experiments with OSPA prototypes showed a 53% improvement. While these improvement percentages are very similar, the values of the predicted stroke and work output are about 16% larger than the experimental values. The optimization requires only ~5 h to run on a common laptop.

Leakage Characteristics of Proportional Directional Valve

This paper deals with the analysis of leakage characteristics of the proportional directional valve. These characteristics distinguish a real directional valve from an ideal one. The ideal directional valve is characterized by zero leakage due to its perfect geometry. The investigated element is the three-position four-way proportional directional valve with zero spool lap and feedback from the spool position. The spool position is measured by the inductive position sensor and processed by external electronics. Internal leakage occurs due to axial and radial clearances between the spool and the sleeve. The magnitude of axial clearances that occur at throttle edges and their effect on the directional valve leakage is the subject of research. The blocked-line pressure sensitivity curve, the leakage flow curve and the center flow curve are determined by experiment. Individual characteristics are determined for different working fluid temperatures and different supply pressures. The flow through internal leaks in the center position of the valve spool is determined by analytical calculations. The flow through internal leaks is also simulated using the Ansys Fluent software. Subsequently, the geometry of the flow simulation model is modified to take into account manufacturing tolerances. From simulation results, the effect of the manufacturing tolerance magnitude on the internal leakage of the directional valve is evaluated. Finally, simulated dependencies are compared with experimentally determined characteristics.

Prediction of the Potential Trade Relationship of Lithium-Ion Battery’s Main Element Raw Material Minerals Combined with the Local Characteristics of the Trade Network

In recent years, with the rapid development of the lithium-ion battery industry, the massive upstream consumption of mineral raw materials has led to great crises and challenges in balancing global supply and demand. A diversity of trading partners can effectively alleviate the pressure of supply and demand for raw materials; so, it is particularly important for trading countries to find suitable trading partners. This study takes nine important minerals contained in the main element raw materials of lithium-ion batteries as the research object, and the international trade data range from 2011 to 2020. The study combines complex networks and motifs and links prediction methods to predict the potential international trade relations of the nine minerals based on the actual network topology. We summarize three trade link rules as follows. (1) The predicted links have a timeliness requirement, and they generally turn into actual trade links within 3 years. (2) When looking for trading partners, trading countries tend to establish long-term and stable trade relations. (3) The existing trade relations will promote the establishment of predicted trade relations. In addition, we find that successfully predicted links will promote the formation of important motifs in the network. This study can provide a theoretical basis for trading countries to find suitable trading partners and can strengthen the safety of trading countries in the trade of the main element minerals for lithium-ion batteries.

Physiological Demands of a Self-Paced Firefighter Air-Management Course and Determination of Work Efficiency

To assess the physiological demands of an AMC and examine differences across BMI categories. A secondary aim was to develop an equation to assess work efficiency in firefighters. Fifty-seven firefighters (Women, n = 4; age: 37.2 ± 8.4 yr.; height: 182.0 ± 6.9 cm; body mass: 90.8 ± 13.1 kg; BMI: 27.8 ± 3.6 kg·m-2) completed an AMC per routine evaluation while wearing a department issued self-contained breathing apparatus and full protective gear. Course completion time, starting pounds per square inch (PSI) on the air cylinder, changes in PSI, and distance traveled were recorded. All firefighters were equipped with a wearable sensor integrated with a triaxial accelerometer and telemetry to assess movement kinematics, heart rate, energy expenditure, and training impulse. The AMC consisted of an initial section involving a hose line advance, rescue (body drag), stair climb, ladder raise, and forcible entry. This section was followed by a repeating loop, which consisted of a stair climb, search, hoist, and recovery walk. Firefighters repeated the course loop until the self-contained breathing apparatus air supply pressure reached 200 PSI, at which time they were instructed to lay down until the PSI reached zero. Average completion time was 22.8 ± 1.4 min, with a mean distance of 1.4 ± 0.3 km and an average velocity of 2.4 ± 1.2 m·s-1. Throughout the AMC, the mean heart rate was 158.7 ± 11.5 bpm equating to 86.8 ± 6.3% of the age-predicted max heart rate and a training impulse of 55 ± 3 AU. Mean energy expenditure was 464 ± 86 kcals and work efficiency was 49.8 ± 14.9 km·PSI-1·s. Regression analysis determined that fat-free mass index (R2 = 0.315; β = -5.069), body fat percentage (R2 = 0.139; β = -0.853), fat-free mass (R2 = 0.176; β = -0.744), weight (R2 = 0.329; β = -0.681), and age (R2 = 0.096; β = -0.571) were significant predictors of work efficiency. The AMC is a highly aerobic task with near-maximal heart rates reached throughout the course. Smaller and leaner individuals achieved a higher degree of work efficiency during the AMC.

Study on the Effect of Pressurized Air Supply Outlet Setting on the Effect of Anteroom Smoke Control

In the selection of smoke control system, the Technical standard for smoke management systems in buildings (GB51251-2017), Article 3.1.1, paragraph 2, makes strict requirements for the setting of mechanical pressurized air supply outlets in anterooms, in order to study the influence of different setting methods of supply outlets on the smoke control effect of anterooms, the wind speed of the anteroom doorway section and the smoke flow in the anteroom are researched for different settings of the location of outlet and air supply angle with the help of Pyrosim. The results show that the effect of anteroom smoke control is not only related to the wind speed of the doorway section, but also related to the air velocity distribution at each point of the doorway section; at the same time, the air supply angle also has some influence on it.

Energy-Efficient Hydraulic Pump Control for Legged Robots Using Model Predictive Control

Hydraulic actuating system exhibits potential for legged robots to achieve highly agile dynamic movement because of their high power-to-weight ratio. However, the low energy efficiency of the hydraulic system can reduce the operating time and cause heat dissipation. In this article, an optimal control framework based on the model predictive control (MPC) is proposed to improve energy efficiency and provide robust supply of pressure required for robot tasks. The MPC includes the power loss function and supply pressure regularization term as the cost function and limitation on the pump speed and acceleration as the constraints. When implemented to the hydraulic biped robot, LIGHT, the proposed method allows legged robots to achieve the commanded motion without losing balance while minimizing energy consumption. The energy saving performance of the proposed method with MPC is also validated via simulation and experiment.

The Squeeze Film Effect with a High-Pressure Boundary in Aerostatic Bearings

The squeeze film effect was discussed in several fields, but mostly under the same pressure boundary conditions. However, pressures at the inlet and outlet are different for aerostatic bearings. In this paper, the dynamic Reynolds equation group, with the stiffness and damping pressure written separately, is deducted and numerically solved with a high-pressure boundary for a parallel flat and circular thin film. The circular thin film considers the two results of the supply pressure boundary inside and outside. All dynamic pressure distribution and stiffness curves are given in a dimensionless form, and a comparative analysis of squeeze film characteristics with and without external pressure is conducted. From the calculation results, it can be concluded that the squeeze effect shows damping for zero-frequency and stiffness for infinite-frequency for compressible lubricants. The dynamic pressure in the static high pressure region is also high at high frequencies affected by gas compressibility. Based on these analytical results, the transfer functions of the thin film are given to further analyze the dynamic performance of aerostatic bearings, and the shape of the response curve approximates an exponential decay form, even when the amplitude increases to 10% of the gas film thickness.

On cavitation in the radial flow of a thin lubricating film between two overlying disks

This study is focused on the characterization and modeling of aviation fuel cavitation physics in radial flow in a thin layer between two disks—a geometry highly relevant to aviation fuel pump systems. This involves a lower circular disk with a centrally located fuel injection port and a matching disk resting on top of the lower disk. In the described experiments, we have quantified and compared cavitating disk behavior for distilled water and JP-5 fuel at various inlet supply pressures via high-speed imaging and radial pressure measurements. High-speed imaging data were used to quantify the radial collapse location of cavitation voids. An enhanced gradient shadowgraphy method was employed to obtain the spatial–temporal evolution of propagating bubbly shock waves. This technique revealed unsteady shock waves propagating in a spiral motion in JP-5 fuel, while a standing bubbly shock was observed in water. In our modeling efforts, the Rayleigh–Plesset equation was adapted to a spatial form in order to predict the radial location of cavitation bubble collapse. Further work incorporated the spatial Rayleigh–Plesset equation into the barotropic model that has been used previously for cavitating nozzle flows and generalized it to radial flow geometry in order to reproduce radial pressure profiles obtained from the experiment. The model predictions of the radial location of bubble collapse and the radial pressure profiles are shown to be in excellent agreement with the experiments. This approach will be valuable for predicting aviation fuel cavitation in complex fuel system geometries.

Research on the influence of a micro-groove-orifice structure and its layout form on the static characteristics of aerostatic journal bearings under a high gas supply pressure

To solve the problems of a low gas supply pressure and low load capacity of traditional orifice-compensated aerostatic journal bearings (OCAJBs), this paper presents the design of a double-row gas supply micro-groove-orifice aerostatic journal bearing (MGOAJB). By establishing new governing equations and introducing the SST k- ω turbulence model, the influence of the micro-groove-orifice (MGO) structure and its layout form on the static characteristics of aerostatic journal bearings under a high gas supply pressure are studied. It is found that under high gas supply pressure, the MGO structure can significantly improve the load capacity and stiffness and reduce the gas consumption of the MGOAJB compared with the OCAJB. With additional MGO structures in the eccentric direction of the spindle, the load capacity and stiffness of the bearing increase substantially, and the gas flow also increases. The layout direction of the MGO has a prominent influence on the static characteristics of the MGOAJB. Axial MGOs have a higher load capacity and stiffness and lower gas flow. The accuracy of the simulation method is verified by experiments. This study provides a theoretical basis and method for the design of aerostatic journal bearings under a high gas supply pressure.

The impacts of the wetness–dryness encountering of the upstream inflow and downstream salt intrusion on water supply in coastal urban agglomeration

Abstract In the current study, to investigate the impacts of the wetness–dryness encountering of the upstream inflow and downstream salt intrusion on the water supply of the Pearl River Delta, we developed a water evaluation and planning (WEAP)-based water resources allocation model to calculate water supply schemes for the Pearl River Delta under 10 different scenarios. The impact of the scenarios on the water supply scheme of the Pearl River Delta was investigated. The results showed that (1) the water shortage of the Pearl River Delta is highly dependent upon the dryness combination of the upstream runoff during the dry period, in particular to the cities at the Pearl River Delta estuary, the water shortages are seriously influenced by saltwater intrusion; and (2) the water transfer projects could alleviate the water supply pressure of the Pearl River Delta when there is an extreme or more dryness encounter of upstream runoff. However, when extreme dryness events are impacting the upstream runoff of the West River, the impact of the water transfer projects is weakened and much of the critical upstream runoff for saltwater suppression cannot be satisfied, which largely impacts water withdrawals at the downstream cities in the Pearl River Delta estuary.

Numerical modelling and heat transfer optimization of large-scale multi-tubular metal hydride reactors

Heat management during the absorption/desorption process is a key aspect in improving the performance of large-scale hydrogen storage systems. In this article, the absorption and desorption performance of a multi-tubular hydride reactor is numerically investigated and optimized for 60 kg mass of LaNi5 alloy. The 90% absorption with 7, 14, and 19 tubes is achieved in 985, 404, and 317 s with an overall reactor weight of 78.46, 88, and 88.2 kg, respectively. The 14-tube reactor performance is investigated by introducing the longitudinal fins inside the tubes. The reactor performance is enhanced by allocating fins into different pairs of half and full fins constrained by overall fin volume. A thermal resistance network model is presented to investigate the effect of fin distribution and coolant velocity on equivalent resistance of the metal hydride reactor. Storage performance obtained from numerical model validates the thermal resistance analysis from heat transfer viewpoint. With six full fins, 90% hydrogen absorption is achieved in 76 s. However, tubes with 6, 8, and 12 pairs of half and full fins require 74, 58, and 54 s, respectively. The 14-tube reactor with 8 pairs of half and full fins is used for quantifying the augmentation in the absorption performance in response to operating conditions (supply pressure and heat transfer fluid temperature). A design methodology is outlined for the development of a large-scale multi-tubular hydride reactor based on a heat transfer optimization strategy.

Mathematical modeling of pressure characteristics of the deflector-jet pilot stage considering boundary layer flow

The performance of a deflector-jet servo valve significantly depends on the pressure characteristics of its pilot stage. The complex flow field within the deflector-jet pilot stage presents enormous difficulty and challenge in establishing its mathematical model. In this work, according to the energy conversion characteristics of the flow field, the flow process within the pilot stage is divided into five phases for modeling: inside-pipe flow, first jet, first pressure recovery, secondary jet, and secondary pressure recovery. To better reveal the intrinsic operating mechanism of a deflector-jet pilot stage, the boundary layer is introduced into the model. Computational fluid dynamic (CFD) simulation and experiment are conducted to validate the developed mathematical model at different supply pressures. The result demonstrates that the velocity distribution of the jets and the pressure characteristics of the pilot stage are significantly influenced by the boundary layer. The boundary layer flow within the V-groove has a greater impact on the pressure characteristics than that within the nozzle. Verified by the CFD simulation and experiment, the developed model can accurately predict the velocity distribution of the jets and pressure characteristics. At different supply pressures, the maximum relative error between the theoretical and experimental results of the dimensionless pressure characteristic is 5.36%.