Instantaneous Flow Rate Research Articles

Flow rate evaluation using water hammer equations – Reformulation of the method

The present paper aims to improve the applicability of the pressure-time method for flow rate evaluation by eliminating the necessity to cut off the machine discharge completely and taking into account the compressibility of the fluid. As a result, the flow rate determination is possible for any load changes, increase or decrease. The method uses the water hammer equations with the differential pressure measured between two cross-sections. Furthermore, the instantaneous flow rate is analytically linked to the pressure variation and the losses. The method is presented and validated against numerical results.

Effect of elevated pressure on gas-solid flow properties in a powder feeding system

Abstract In view of the powder feeding system, a multi-physical coupling model of the gas-powder-piston was established based on the Euler-Euler two-fluid model. The numerical simulation method was applied to explore the effects of dense gas-solid flow characteristics under different operating pressures. The results show that gas-solid pulsations at different operating pressures are mainly concentrated in the upper part of the powder tank. An elevated operating pressure efficiently decreases the powder layer area (εp = 0.1) fluctuation. As the operating pressure increases from 0.5 MPa to 3.0 MPa, the rising time and fluctuation rate of pressure are reduced by 71.4% and 62.3%, respectively, and the pressure in the tank has a long stabilization period. Meanwhile, the variation of the instantaneous powder flow rate is more stable and its average value is closer to the theoretical. A high-pressure environment is more conducive to the stable transportation of powder.

Measurement of Instantaneous Mass Flow Rate of Polypropylene Gasification Products in Airflow

A simple semi-empirical gas-dynamic approach for measuring the instantaneous mass flow rate of gasification products of low-melting solid material (polypropylene) in a flow-through gas generator with ambient-temperature air as gasifying agent is proposed. The approach is validated experimentally in the direct-connect facility allowing for the short-term (~0.5 s) heating of incoming air up to ~1700 K by hydrogen injection and ignition or by pyrotechnic charge activation. The application of the proposed method for processing experimental data for 9 (of over 100) selected typical test fires showed that the time-averaged total yield of polypropylene gasification products varied from 43 to 120 g/s, while the air-to-gasification product mass ratio was 2.3–2.9. The results of all conducted experiments confirm the applicability of the proposed approach for determining the mass flow rate of gasification products. The universality of the proposed approach is confirmed by applying two different schemes of gas generator: one with hydrogen ignition and another with pyro-charge ignition.

Design strategy and performance evaluation of novel miniature two-dimensional (2D) piston pump with a dual stacking mechanism

Since the traditional axial piston pumps have limitations to fulfill the development demands of hydraulic pumps under the electrification trend and maintain a high volumetric efficiency within various operating conditions, a new two-dimensional (2D) piston pump is proposed. In this study, the novel structure and working principle developed to raise the power density and achieve better performance were comprehensively introduced. As the motions of rotary and reciprocating are employed together, the new pump can achieve the purpose of compact structure, a small moment of inertia, and self-balancing of reciprocating inertial force. In addition, an accurate flow area during the oil discharge process was re-defined. A nonlinear mathematical model of the instantaneous flow rate of the new 2D pump for evaluating leakage performance and volumetric efficiency was established and studied in detail. Moreover, crucial features for further improvement of working performance were discussed. Then, a prototype pump was made to experimentally measure the output flow at various load pressures (from 1 MPa to 8 MPa) and rotational speeds (from 1000 r/min to 6000 r/min). The volumetric efficiency was in a range of 91.27% to 99.21%. The results of simulations and experiments well demonstrated the capabilities of the proposed novel 2D pump.

Modeling and Simulation of Multipumping Photovoltaic Irrigation Systems

The growing market of large-power photovoltaic irrigation systems (PVISs)—made of systems with different and several motor pumps working in parallel—needs simulation tools capable to estimate their energy and water productivity. The objective of this paper is to present the simulation models developed for parallel multipump PVISs fed by a single PV generator. These models seek to maximize the instantaneous water flow rate according to the available PV power and were developed for the typical configurations of large-power irrigation facilities. The models present some advantages when compared with the current state of the art (in which a single motor pump connected to a 1/N fraction of the PV generator is simulated and the result is multiplied by N): in the case of negligible hydraulic friction losses, the use of the multipump model shows gains with respect to the state of the art; in the case of appreciable friction losses, the current state of the art overestimates the productivity of the systems. Then, the ability of these models to compare different multipump designs is shown: two groups of pumps working at variable frequencies show better performance than a group working at a variable frequency and a group at a nominal frequency—an 8% increase in the water pumped is seen.

Large-Eddy Simulations of Wind-Driven Cross Ventilation, Part 2: Comparison of Ventilation Performance Under Different Ventilation Configurations

Natural ventilation can contribute to a sustainable and healthy built environment, but the flow can be highly dependent on the ventilation configuration and the outdoor turbulent wind conditions. As a result, quantifying natural ventilation flow rates can be a challenging task. Wind tunnel experiments offer one approach for studying natural ventilation, but measurements are often restricted to a few points or planes in the building, and the data can have limitations due to the intrusive nature of measurement techniques or due to challenges with optical access. Large-eddy simulations (LES) can offer an effective alternative for analyzing natural ventilation flow, since they can provide a precise prediction of turbulent flow at any point in the computational domain and enable accurate estimates of different ventilation measures. The objective of this study is to use a validated LES set-up to investigate the effect of the opening size, opening location and wind direction on the ventilation flow through an isolated building. The effects are quantified in terms of time-averaged and instantaneous ventilation flow rates, age of air, and ventilation efficiency. The LES results indicate that, for this isolated building case, the effect of the wind direction is more pronounced than the effect of the size and position of the ventilation openings. Importantly, when ventilation is primarily driven by turbulent fluctuations, e.g. for the 90° wind direction, an accurate estimation of the ventilation rate requires knowledge of the instantaneous velocity field.

Periodic Flow Through Regenerator Fillers Made from Packed Spherical Microparticles

Periodic flow of gases at cryogenic temperatures through microporous structures occur in the regenerators of Stirling-type cryocoolers. For computational fluid dynamics simulation of such flows using the Darcy–Brinkman–Forchheimer model, permeability and inertial coefficients are needed. Experimental pore-level characterization of such regenerators is difficult due to their microporous structure, and the occurrence of near-zero instantaneous flow rates and extraction of these parameters from experimental data can involve significant uncertainty. In this work, by three-dimensional direct simulation, the hydrodynamic parameters are found for flow through a metallic fill powder common to some recent cryocooler regenerators that operate at very low temperatures. The intrinsic permeability and the Forchheimer coefficients are found for parameter ranges of interest to pulse-tube cryocoolers and are compared with reported extracted experimental values. The permeability and Forchheimer coefficients are correlated to be suitable for application in computational fluid dynamics codes.

Prediction Equations for Spirometry in Adults from Northern India

Most of the Indian studies on prediction equations for spirometry in adults are several decades old and may have lost their utility as these were carried out with equipment and standardisation protocols that have since changed. Their validity is further questionable as the lung health of the population is likely to have changed over time. To develop prediction equations for spirometry in adults of north Indian origin using the 2005 American Thoracic Society/European Respiratory Society (ATS/ERS) recommendations on standardisation. Normal healthy non-smoker subjects, both males and females, aged 18 years and above underwent spirometry using a non-heated Fleisch Pneumotach spirometer calibrated daily. The dataset was randomly divided into training (70%) and test (30%) sets and the former was used to develop the equations. These were validated on the test data set. Prediction equations were developed separately for males and females for forced vital capacity (FVC), forced expiratory volume in first second (FEV1), FEV1/FVC ratio, and instantaneous expiratory flow rates using multiple linear regression procedure with different transformations of dependent and/or independent variables to achieve the best-fitting models for the data. The equations were compared with the previous ones developed in the same population in the 1960s. In all, 685 (489 males, 196 females) subjects performed spirometry that was technically acceptable and repeatable. All the spirometry parameters were significantly higher among males except the FEV1/FVC ratio that was significantly higher in females. Overall, age had a negative relationship with the spirometry parameters while height was positively correlated with each, except for the FEV1/FVC ratio that was related only to age. Weight was included in the models for FVC, forced expiratory flow (FEF75) and FEV1/FVC ratio in males, but its contribution was very small. Standard errors of estimate were provided to enable calculation of the lower limits of normal and standardised residuals for these parameters. The equations were found to be valid on the test dataset, and therefore, may be extended to general population. Comparison with the 1960s equations revealed lack of good agreement, and substantially higher predicted FVC with the current equations, especially in the forty-years-plus age group, in both males and females. Even in the age group upto 40 years, the level of agreement was clinically not acceptable. Validated prediction equations have been developed for spirometry variables in adults of north Indian origin using the current ATS/ERS spirometry standardisation recommendations. The equations suggest an improvement in the lung health of the population over time in the middle-aged and the elderly. These equations should address a long-felt unmet need and enable a more appropriate evaluation of spirometry data in different chest diseases in Indian subjects.

CARD21: In Vitro Investigation Of The Timing Of The LVAD Pulsatility Event On Intraventricular Hemodynamics

Background: To reduce in-pump thrombosis and potentially improve left ventricular (LV) washout, pulsatility events (i.e., periodic LVAD speed modulation) have been introduced in 3rd generation LVADs. However, this pseudo-pulsatility of the centrifugal continuous flow pumps is not synchronized with native LV residual contractility. This study investigates the effect of timing of pulsatility events, with respect to LV pressure variations along the cardiac cycle, on intraventricular hemodynamics. Methods: Time-resolved stereo particle image velocimetry measurements were performed in a patient-derived quasirigid LV silicon model implanted with an LVAD. The residual LV contractility was modelled as a periodic variation in intraventricular pressure (IVP). Velocity fields in two orthogonal planes were measured for 7.5 cardiac cycles (including 3 occurrences of the pulsatility events, which happen every two seconds), for 3 LVAD speeds and 4 different synchronicities of pulsatility: at maximum/ minimum IVP and during increasing/decreasing IVP. Instantaneous measurements of the flowrate through the LVAD, with a time-resolution of 1 ms, were collected during the entire experiment. Ventricle stagnation index (VSI) was computed for each measurement plane and all experimental conditions studied. Results: Despite maintaining a constant average flowrate, the synchronicity of the LVAD pulsatility with the oscillatory IVP strongly influenced the flow rate waveforms, especially the peak and minimum instantaneous flow rates. A strong effect of the timing of pulsatility was also observed on intraventricular hemodynamics: pulsatility events taking place during decreasing IVP (diastole) resulted in higher VSI than other timing of pulsatility. Overall, these high resolution, instantaneous measurements of LVAD flow rate and pressure also highlighted the complex interrelations between LVAD speed, peripheral resistance, IVP and flow rate. Conclusion: This in vitro study elucidates the effect of LVAD pulsatility event synchronicity with the cardiac cycle on flowrate and LV flow patterns.

Numerical studies on interactions between a centrifugal compressor and the back-propagated pressure waves originated from a pulse detonation combustor

In order to investigate the influence of the back-propagated pressure waves originated from a pulse detonation combustor on the operating characteristics of the compressor in the pulse detonation turbine engine, a model consist of a centrifugal compressor and an isolation section which was usually utilized to decrease the peak value of the back-propagated pressure waves was set up. Numerical simulations were carried out to study the interactions between the centrifugal compressor and the back-propagated pressure waves under different operating conditions. The matching characteristics of the compressor under the influence of the back-propagated pressure waves were analyzed in a detonation cycle. The results showed that the back-propagated pressure waves would push the shock wave in the isolator towards the throat position, but the shock wave did not pass through the throat for the compressor corrected speed of n = 100% and n = 105%. For these two cases, the back-propagated pressure waves were completely isolated and the operating characteristics of the compressor were the same as those under the steady outlet conditions. For the corrected speed of n = 50% and n = 90%, the shock wave in the isolator section was pushed out of the throat and the supersonic flow in the isolator section was destroyed under the influence of the back-propagated pressure waves. The back-propagated pressure waves would propagate upstream into the compressor. Consequently, the instantaneous mass flow rate and the torque acting on the centrifugal impeller was decreased. The work required by the compressor was also reduced. The equivalent isentropic efficiency of the compressor was decreased. The separation or backflow in the compressor caused by the back-propagated pressure waves would results in an equivalent isentropic efficiency loss of 3.2% points for the case of n = 90% and 15.6% points for the case of n = 50%.

Experimental research of the surfactant effect on seepage law in coal seam water injection

Coal seam water injection is one of the important means of mine disaster prevention, which helps to restrain the production of dust and reduce gas concentration. Ionic surfactant can change the capillary force of water in coal pore fissures, so as to enhance the wetting effect of coal seam water injection. However, the research on the effect of surfactant on the seepage process is still relatively weak. In order to explore the influence of surfactant on the seepage of coal seam water injection, the bituminous coal of Daliuta Coal Mine was used as the experimental coal sample to carry out wettability test and triaxial seepage experiment. The influence mechanism of capillary effect in the wetting and seepage stage of coal seam water injection is analyzed. The results show that the water injection process of cylindrical coal core goes through the unsaturated seepage stage and the steady seepage stage. In the process of unsaturated seepage, the increase rate of cumulative flow at the entrance of coal sample changes from fast to slow. And the instantaneous flow rate of surfactant is higher than that of water with a range of 0.1∼4 mL/min in the unsaturated seepage stage. The cumulative flow rate of water injection increased by 40%–60%. The instantaneous flow rate of water injection increases with the increase of capillary rising factor, and the correlation coefficients is 0.977. While in the stable seepage stage, the cumulative flow basically shows a linear increasing trend, and the increasing percentage of cumulative flow of water injection is lower than that of unsaturated seepage. It indicates that the surfactant can significantly improve the wetting rate at the stage of unsaturated seepage, and surfactants enhance the ability of liquid-solid interface to replace gas-solid interface.

New Method to Determine the Dynamic Fluid Flow Rate at the Gear Pump Outlet

External gear pumps are among the most popular fluid power positive displacement pumps; however, they often suffer from excessive flow pulsation transmitted to the downstream circuit. To meet the increasing demand of quiet operation for modern fluid power systems, it is necessary to give a physically sound method of analyzing the operation of a volumetric pump. The analysis of the basic approach used by the majority of researchers for calculating the flow rate of a gear pump by E.M. Yudin is presented. The article presents a new method for analyzing the operation of volumetric pumps. The method is suitable for the pumps whose dynamic characteristics should be considered according to the model of an equivalent source of flow fluctuations by V.P. Shorin. The method is based on wave theory, the method of hydrodynamic analogies and the impedance method, where the pump is considered according to the model in lumped parameters. The method consists in determining the pressure pulsations at the pump output in bench systems with known dynamic characteristics and recalculating the pump flow rate in pulsations. Computational dynamic models of bench systems in lumped parameters are proposed for subsequent use in dynamic tests of pumps in the form of equivalent sources of fluid flow fluctuations. We give recommendations for the formation of test bench systems with a throttle, a cavity and a pipeline at the pump output. Using the example of an external gear pump with a working volume of 14 cm3/rev, the implementation of the proposed method is considered. The pump’s own pulsation characteristic of the flow rate in a bench system with an “infinitely long” pipeline along two harmonic components of the spectrum is determined, and a test of the method based on the method of determining the instantaneous flow rate by R.N. Starobinskiy is proposed. It is shown that, according to the proposed method and the method of R.N. Starobinskiy, the divergence of the amplitudes of flow pulsations does not exceed (5–10)%. The high degree of coincidence of the results confirms that the external gear pump in question should be considered according to the equivalent source of flow fluctuations model.

Open Experimental Data-Sets to Reveal Behavioural Insights of High-Deck Coach Evacuations

Numerous evacuation performance data for the utilization in evacuation modelling and simulations have been established for the conventional/widely studied scenarios, such as building evacuation scenarios. However, such data are typically scarce for a new scenario in literature — evacuation from high-deck coaches. This paper fulfills this gap by presenting empirical high-deck coach evacuation data-sets that can be used for model configuration and validation. To this end, firstly, five essential and commonly used performance metrics, i.e., evacuation time, flow rate, alighting time gap, velocity on stairways and exit choice, were collected and derived from two series of controlled experiments with 7 and 22 runs that involved 44 and 96 participants respectively. Then, all these datasets were structured in the distribution form, based on which three critical behavioural insights are revealed regardless of the evacuation conditions (the types of high-deck coaches, lighting conditions, and age groups). First, the evacuation behaviour in normal (experimental) conditions conforms to a multi-stage pattern (a modified four-stage pattern, i.e., reaction, acceleration, fluctuation and saturation stages). Second, the instantaneous flow rate can be well captured by the Burr, Loglogistic and Lognormal distributions, and the alighting time gap can be represented by the Burr distribution. Third, more than 50% of passengers evacuate through the rear door in the front-and-rear-door evacuations. The frequency of choosing the front door is found to shift towards the direction of the rear door compared to the ideal results (based on the shortest distance calculation) with a magnitude of approximately 1.95 seat rows. The presented data-sets are valuable resources for the development of high-deck coach evacuation models. The empirical findings promote the understanding upon the evacuation behaviour of high-deck coach passengers.

Low sap flow of Picea crassifolia and its influencing factors in Qilian Mountains, China

As an important part of ecological hydrology, transpiration is the basis for analyzing forest water cycle and healthy growth, and important for forest protection and scientific management. We used thermal diffusion probes (TDP) to continuously monitor sap flow of Picea crassifolia in the Qilian Mountains from 2017 to 2018 to explore water consumption of P. crassifolia, and analyze the main controlling factors for the growth and transpiration of spruce. The results showed that the instantaneous change of P. crassifolia sap flow showed a single-peak curve in sunny days, a multi-peak or double-peak curve in cloudy days, and basically no obvious regularity in rainy days. The sap flow density of Qinghai spruce was consistent with the dynamics of solar radiation. The sap flow started earlier and ended later on sunny days, and lasted for 12 to 14 hours. Due to the high altitude (2700 m), low air temperature, and low vapor pressure difference (VPD) in this area, the overall sap flow density was low, with an average of (0.86±0.49) kg·d-1. On the hourly scale, the instantaneous rate of sap flow was significantly affected by solar radiation and VPD. On the daily scale, soil temperature and soil moisture content of the 0-40 cm layer were significantly related to sap flow density. The spruce sap flow density decreased with the decreases of solar radiation, air temperature, and VPD. In the high-altitude forest area of Qilian Mountains, lower soil and air temperature as well as lower VPD and solar radiation were the causes of low sap flow in Picea crassifolia in this area.

On the effect of boundary vibration on mucus mobilization

In this study, we investigate the mobilization of mucus in a cylindrical tube of constant cross-section subjected to a Small Amplitude Oscillatory Shear (SAOS) assuming the viscoelastic behavior of mucus is governed by the Oldroyd-B constitutive equation. The Laplace transform method was adopted to derive expressions for the velocity profile, average velocity, instantaneous flowrate and mean flowrate (i.e., mobilization) of the mucus within the tube. Additionally, a 2D finite element model (FEM) was developed using COMSOL Multiphysics software to verify the accuracy of the derived analytical solution considering both a Newtonian and an Oldroyd-B fluid. Furthermore, sensitivity studies were performed to evaluate the influence of the vibration frequency, vibration amplitude, mean relaxation time, and zero-shear viscosity on mucus mobilization. Results prove that the analytical and numerical results are within acceptable error tolerance and thus in excellent agreement. Besides, the parametric studies indicate a 48%, 57%, and 343% improvement in mucus mobilization when the mean relaxation time, vibration amplitude, and vibration frequency, respectively were each increased by a factor of 6 from the assumed nominal values. Conversely, the mucus mobilization decreased by 25% when the zero-shear viscosity was increased by a factor of 6 from the assumed reference value. In general, this study confirms that mucus mobilization in a tube can be improved by increasing the magnitude of vibration amplitude and vibration frequency. Similarly, the larger the magnitude of mucus mean relaxation time the better the mucus mobilization when the tube is subjected to boundary vibrations. Finally, mucus mobilization decreases as the magnitude of mucus viscosity increases.

Determination of Time-Evolving interfacial tension and ionic surfactant adsorption kinetics in microfluidic droplet formation process

Surfactant adsorption plays an important role in microfluidics, which can be investigated by the dynamic evolution of interfacial tension. A differential pressure-based method is proposed to understand the basic laws of time-evolving interfacial tension and adsorption kinetics of ionic surfactants during the microfluidic droplet formation processes. Instantaneous flow rates and flow resistances are precisely analyzed based on auto-recognized microscopic images and the waveform of differential pressure, and the interfacial tension is determined from the Young-Laplace equation with a time resolution of 1/60 s. The concentration of surfactant at the liquid–liquid interface is obtained according to the Frumkin adsorption model, leading to an in-depth understanding of the adsorption rates and the apparent mass transfer rates of surfactants. The surfactant adsorption is demonstrated to obey the kinetic-controlled adsorption mechanism and therefore a measurement method for the adsorption rate constant is created to understand the kinetic characteristics of small-molecule ionic surfactants.

Generation of Ions from Aqueous Taylor Cones near the Minimum Flow Rate: "True Nanoelectrospray" without Narrow Capillary.

Generating ultrafine charged droplets using electrospray is crucial for attaining high ionization efficiency for mass spectrometry. The size of the precursor charged droplets depends on the spray flow rate, and conventional wisdom holds that an electrospray of a nL/min flow rate (nanoelectrospray) is only possible using narrow capillaries with an inner diameter of ∼1 μm or smaller. Here, the electrospray of aqueous solutions with high electric conductivities generated from a large off-line capillary of 0.4 mm i.d. has been performed using a high-pressure ion source. The electric discharge is avoided by operating the ion source at 2.5 bar gauge pressure. The highly stable Taylor cone can be tuned to a near-hydrostatic state that exhibits the "true nanoelectrospray" properties, i.e., high salt tolerance and minimal ion suppression. The Q1/2 scaling law describing the electrospray current I and flow rate Q is found to be valid down to the nanoflow regime under a condition that is free of electric discharge. For a given solution, the flow rate and the size of the initial droplets and ionization species can be controlled with the spray current as the indicator for the instantaneous flow rate without changing the emitter capillary of different sizes. In regard to the application, the nanoelectrospray with a large micropipette tip is easy to use, free of clogging when dealing with viscous and high-salt buffer solutions, and with reduced surface interaction with the emitter inner surface. An acquisition of very clean mass spectra of proteins from concentrated solutions of nonvolatile salts such as phosphate-buffered saline is demonstrated.

An in-vitro model of stiffened aortic valves to develop an iso-stiffness-lines graph for aortic stenosis classification

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Bern Center for Precision Medicine (BCPM) Introduction The echocardiographic diagnosis of aortic stenosis (AS) is established by assessing its maximal opening area (OA). The behavior of OA is dependent on transvalvular flow which can be low in case of low-flow, low-gradient AS. However, the complicated decision tree of the current guidelines for the assessment of AS does not consider flow but rather a stroke volume and does not take into account the size of the valve. This experiment was designed to create a graphical representation of the OA versus flow for various valve stiffness values to eventually build a model with iso-stiffness lines and simplify the assessment of aortic stenosis Methods We filmed a harvested porcine aortic valve mounted in a pulsatile flow loop during the ejection time with a high speed camera (2000Hz), measured for each time point OA and the instantaneous flow through the aortic valve at 10 different mean flow rates (ranging from 0.5 to 5.0 liters/min). We stiffened the valve by treating it with a protein cross-linking agent (formaldehyde) to yield a total of three stiffness grades (a, b, c) and repeated the procedure for each of those grades. We divided both OA and flow, by the area of left ventricular outflow tract (LVOT) in order to account for different valve sizes. We plotted each OA against its corresponding flow after correcting for the intersignal delay. In order to analyze the cycle portion corresponding to the most steady flow, we only included the 5% highest instantaneous flow rates (for each of the 10 mean flow rates). We then measured the relative stiffness by measuring the relative pump work between stiffness grades, 1 being defined as the native stiffness grade. We predicted relative stiffness grade of each valve in a k-fold validation algorithm (each valve being sequentially taken as the test set and all the other remaining valves in the training set), taking a sigmoid function model. Finally we performed a linear regression of each measured and predicted stiffness grade of each valve to assess the accuracy of the model. Results We could analyze 11 valves and performed an 11-fold cross validation. We could predict the relative stiffness of each of the valve with a good slope value (slope = 0.898) and a modest accuracy (r = 0.639). Conclusions We could predict with modest accuracy the inherent stiffness of the valve only with valve size, flow and opening area, all information available with echocardiography. This will allow to create iso-stiffness line to better classify valve stenosis and compare any patient on one single graph at any flow or valve" size, potentially simplifying the grading system of aortic stenosis, especially for patient with low-flow, low-gradient AS. Abstract Figure. Combination of Flow and OA Abstract Figure. 3 stiffness stages and Cross-validation

Universal Digital Twin: Integration of national-scale energy systems and climate data

Abstract This article applies a knowledge graph-based approach to unify multiple heterogeneous domains inherent in climate and energy supply research. Existing approaches that rely on bespoke models with spreadsheet-type inputs are noninterpretable, static and make it difficult to combine existing domain specific models. The difficulties inherent to this approach become increasingly prevalent as energy supply models gain complexity while society pursues a net-zero future. In this work, we develop new ontologies to extend the World Avatar knowledge graph to represent gas grids, gas consumption statistics, and climate data. Using a combination of the new and existing ontologies we construct a Universal Digital Twin that integrates data describing the systems of interest and specifies respective links between domains. We represent the UK gas transmission system, and HadUK-Grid climate data set as linked data for the first time, formally associating the data with the statistical output areas used to report governmental administrative data throughout the UK. We demonstrate how computational agents contained within the World Avatar can operate on the knowledge graph, incorporating live feeds of data such as instantaneous gas flow rates, as well as parsing information into interpretable forms such as interactive visualizations. Through this approach, we enable a dynamic, interpretable, modular, and cross-domain representation of the UK that enables domain specific experts to contribute toward a national-scale digital twin.

A time-varying reliability-based robust design method considering overall efficiency of axial piston pump

Axial piston pumps (APPs) are the core energy conversion components in a hydraulic transmission system. Energy conversion efficiency is critically important for the performance and energy-saving of the pumps. In this paper, a time-varying reliability design method for the overall efficiency of APPs was established. The theoretical and practical instantaneous torque and flow rate of the whole APP were derived through comprehensive analysis of a single piston-slipper group. Moreover, as a case study, the developed model for the instantaneous overall efficiency was verified with a PPV103-10 pump from HYDAC. The time-variation of reliability for the pump was revealed by a fourth-order moment technique considering the randomness of working conditions and structure parameters, and the proposed reliability method was validated by Monte Carlo simulation. The effects of the mean values and variance sensitivity of random variables on the overall efficiency reliability were analyzed. Furthermore, the optimized time point and design variables were selected. The optimal structure parameters were obtained to meet the reliability requirement and the sensitivity of design variables was significantly reduced through the reliability-based robust design. The proposed method provides a theoretical basis for designers to improve the overall efficiency of APPs in the design stage.