Large Inlet Research Articles

Numerical study of a copper oxide-based thermochemical heat storage system

A multi-physics model is developed to investigate the performance of high-temperature thermochemical heat storage using the redox looping cycle of CuO/Cu2O. The model involved flow in free and porous domains, heat transfer in the CuO pellet-packed porous domain (i.e., convection between fluid and pellets, conduction and radiation among pellets), and the endothermic/exothermic reaction. The reaction rate was estimated using a non-parametric kinetic approach which depends on temperature and extent of the reaction. The model was validated within <10 % error margin by the experimental measurements of the temperature inside the reactor and the molar fraction of O2 at the reactor outlet. The validated model is used to determine the temperature variation and reaction evolution in the pellet-packed domain. In the end, parameter studies were implemented, including inlet mass flow rate, reduction temperature, and oxidation temperature. It was found that a large inlet mass flow brings about a high output temperature, and the reaction runs faster with the larger inlet mass flow. Similarly, increasing the furnace temperature during the reduction process (reduction temperature) also increases the output temperature and accelerates the reaction. In contrast, increasing the furnace temperature during the oxidation process (oxidation temperature) only slightly affected the reaction in the present case. This model could provide useful insights into reactor design, scale-up, and operating conditions to improve the energy storage system performance.

A novel approach to designing compact cyclones for efficient natural gas filtration

This paper presents an innovative method to design cyclone separators based on geometrical principles, and incorporates a coupling iterative algorithm to obtain crucial parameters. The proposed approach allows for simultaneous variation of multiple key parameters, including inlet velocity, inlet height, and pressure drop. Thus, effects of varying one parameter on the others are accounted for. The innovative methodology is utilized to design a novel, high-performance cyclone potentially applicable in natural gas filtration. The introduced cyclone has a uniquely large inlet length to diameter ratio and a small curved cone, making it compact and usable in clusters to handle large flow rates. The cyclone is experimentally tested to evaluate its filtration performance. The results indicate that six micron or larger particles are completely separated, and a cut point diameter of 1 μm is achieved. Finally, the introduced cyclone is numerically investigated to analyze the gas flow behavior and visualize particle trajectories.

Observation and modelling of infragravity waves at a large meso-tidal inlet and lagoon

The role of infragravity waves (IG waves) in beach and dune erosion or in flood hazard has been extensively studied on open beaches. In contrast, the detailed characterization of IG waves and their contribution to the Total Water Level (TWL) along the shore of inlets received little attention so far. In such environment, there is a real lack of in situ observations of waves and hydrodynamics conditions at appropriate spatial and temporal coverage to study the role of infragravity (IG) waves (long waves of frequency typically ranging between 0.004 Hz and 0.04–0.05 Hz) on coastal hazards. This contribution is based on field observations collected at the Arcachon Lagoon, a shallow semi-enclosed lagoon connected to the ocean by a large tidal inlet, located in southwest France. Analyses combine observations made at several locations during storm events within the inlet and the lagoon with numerical simulation with the XBeach surfbeat model to explore the spatial variability of IG waves and simulate observed, historical, and idealized storm conditions. The results show that IG waves are substantial during typical winter storms at the inlet and range from Hm0 = 0.8 to over 1 m across the ebb delta and about 0.4–0.6 m in the inner part of the inlet. At the lagoon entrance, IG waves remain substantial (about 0.1–0.2 m) and decrease to a few centimeters at the lagoon shore. The spatial variability and magnitude of IG waves along the inlet coast, simulated for the historical storms, are quite comparable to those observed during classical winter, and do not increase linearly with offshore wave energy. However, both observations and simulations reveal local amplifications of IG waves in the inner part of the inlet, especially along the sheltered coast were IG waves dominate the variance of free surface elevation, reaching about 0.6–0.7 m during common storms and more than 1 m for an extreme storm scenario. A numerical experiment indicates that IG wave reflection from one coast to the other contributes up to 35–40% of the measured IG wave height at a hot spot located along the sheltered coast. Finally, the contribution of IG waves to TWL at the shore on both sides of the inlet has been estimated to be about 0.4–0.6 m for a common storm and 0.6–0.9 m for an extreme scenario, locally peaking at 0.74 and 1.1 m respectively and overpassing the contribution of wave-induced setup. This work provides new insights into the contribution of IG waves to TWL and its implications for overtopping flooding hazard and overwash processes at large inlets, highlighting the need to consider IG waves in Early Warning Systems or hazard mapping for flood prevention plans in these environments.

Design, Multi-Point Optimization, and Analysis of Diffusive Stator Vanes to Enable Turbine Integration Into Rotating Detonation Engines

Abstract Pressure gain combustion is considered a possible path toward improved thermal cycle efficiency and reduced carbon emissions. However, ad hoc turbine designs are required to maximize the thermodynamic potential; the new turbomachinery should be suited for the oscillations in flow conditions generated by the detonation combustor, which are very different from conventional gas turbines. This paper investigates the design, optimization, and analysis of diffusive stator vanes operating under large inlet flow angles in the high-subsonic regime. First, the design methodology is outlined, focusing on the geometric requirements to ingest high Mach number flow and the parametric modeling of the endwall and the 3D vane pressure and suction sides. Then, the impact of the inlet flow angle on the flow field and vane design is studied through a multi-point, multi-objective optimization with three different inlet angles, performed using steady Reynolds-averaged Navier–Stokes simulations. Remarkable reductions in pressure loss and stator-induced rotor forcing are attained while maintaining an extensive operating envelope and high flow turning. Moreover, several design guidelines are provided based on the analysis of the optimized geometries. Finally, the effectiveness of the proposed methodology is verified with an unsteady assessment of the baseline and optimized vane designs.

Attenuation of Inlet Distortion Effects on Fans Using Asymmetric Inlet Guide Vanes

Abstract This research proposes and preliminarily analyzes a novel concept to passively reduce the negative impact of deep inlet distortion on the fan of an aero-engine. It consists of placing a row of non-axisymmetric inlet guide vanes (IGVs) just upstream of the fan rotor to induce a spatially varying swirl distribution. The swirl distribution is tailored so as to reduce flow incidence in the distorted flow region and increase it in the undistorted flow region to decrease the fluctuation in aerodynamic force on the fan blades under large inlet distortion that can lead to blade failure, as well as attenuate the negative effect of flow non-uniformity on fan/engine aerodynamic performance. A computational study is carried out on a high-speed (transonic) fan rotor (NASA Rotor 67) from a published distortion study using full-annulus unsteady 3D computational fluid dynamics (CFD) simulations. The asymmetric IGV is designed through a process of manual iterations and CFD simulations to take into account the change in flow redistribution with IGV geometry. The asymmetric IGV design, though not optimized, reduces the aerodynamic force variation amplitude by around two-thirds. Moreover, it allows the fan to recover over half of the loss in total pressure rise due to inlet distortion. The asymmetric IGV is also able to reduce the total pressure distortion at the fan rotor exit. Spanwise analysis indicates that the effectiveness of the asymmetric IGV can be improved on all three metrics if better 3D IGV shaping is performed.

Single well geothermal heating systems: Technical and economic assessment of two widely-used configurations

Benefiting from the closed wellbore space, the single well geothermal heating system (SWGHS) could avoid a large number of environmental problems compared to conventional geothermal systems. Combined with heat pump, this technology is attracting growing interest for the development of district heating based on medium-depth geothermal resources. Efforts of the scientific community and of business operators now focus on the technical optimization and commercial viability of the different SWGHS concepts already available. Here, we numerically investigate the heat extraction performance of a butted- and a vertical-well SWGHS possibly operational in a geothermal prospect area in Xi’an, central China. We addressed the performance of the two systems in terms of outlet temperature, heat production rate, heating area, and economic benefits. Sensitivity analysis suggests that large circulation rates and low inlet temperatures have beneficial effects on both thermal efficiency and economic benefits of the project. Our integrated technical and economic analysis suggests that the butted-well SWGHS configuration is particularly suitable for long-run, large-scale applications, compared to the vertical-well design. This work can provide valuable references for the applications of SWGHS, which is of criterial importance for reaching carbon peaking and carbon neutrality goals.

Rotary thermal desorption technology for treatment of oil-based drilling cuttings in shale gas industry

Oil-based drilling cuttings are hazardous wastes in shale gas exploitation and need careful treatments to reduce environmental pollution and waste of resources. One of most widely employed waste-treatment technologies is the thermal desorption due to its high oil recovery efficiency. However, it usually suffers low heat exchange efficiency, thus leveraging operation costs and equipment instability. Toward the end of alleviating limitation, this study rationally designs the structure of the heating component under the guidance of the flat wall heat conduction theory, and uses numerical simulation to analyze the heat transfer of the structure. A rotary thermal desorption technology was thus developed and evaluated. The simulation results showed that given a short time of 800 s the temperature difference between device and cuttings became less than 5 K, indicating good heat exchange efficiency. Large inlet radius of device and high inlet velocity of heat transfer oil were critical parameters to maintain high heat transfer rate. Through industrial experiments verification, the 0.14–0.2 % oil content of treated cuttings qualified the environmental standards. The components of the recovered oil were recyclable C9-C23 alkanes, and the dichromate oxidizability of recovered water was less than 500 mg/L limit. Comparing with other technologies, the scores suggested that this technology was a promising candidate for treating oil-based drilling cuttings.

Study on air-side performance of air-cooled heat exchangers under large air velocity and wet conditions

Humidity condensation and carryover from air-cooled heat exchanger affects human comfort and equipment security in the working environment. Surface treatment with a hydrophilic coating is an effective water drainage and carryover resistance solution. In present study, the condensation carryover and air-side performances of a fin-and-tube heat exchanger (FTHX) and microchannel heat exchanger (MCHX) with different fin pitches and surface treatments were experimentally investigated under large air velocities and different inlet humidity conditions. Hydrophilic treatment of FTHX improved heat transfer and condensation drainage, and reduced air pressure loss. In contrast, with MCHX, hydrophilic treatment did not improve heat transfer and rather increased the air pressure loss. For FTHX, the results showed that, compared with the bare fin, the hydrophilic surface treated fin enhanced the Colburn j factor by 20–60 and 10–40% at inlet air dry/wet bulb temperature of 26.7/19.4 °C (normal humidity condition) and 26.7/23.9 °C (high humidity condition), respectively. The air friction factor f was reduced by namely by 10–40 and 20–40% under normal- and high-humidity conditions, respectively. Condensing water flowed or retained over the fin surface in film, which suppressed the formation of a water bridge among fins, improved water carry-over, and increased the critical air velocity by 50%. However, water film formation over the MCHX enlarged the water stagnant around the fin corner, which increased the air resistance by 5–10%, and increased the probability of the continuous water bridge formation and carryover.

Hurricane Irma: an unprecedented event over the last 3700 years? Geomorphological changes and sedimentological record in Codrington Lagoon, Barbuda

Abstract. Low-lying coasts and small islands, such as in the Lesser Antilles, are particularly vulnerable to hurricane-induced marine floods. In September 2017, category 5 Hurricane Irma, with winds up to 360 km h−1, hit the northern Caribbean islands and caused the destruction of 95 % of the structures on Barbuda Island. We investigated the geomorphological impacts and the sedimentological record related to the storm surge of this hurricane in Barbuda's Codrington Lagoon. Following Hurricane Irma, two wide inlets developed across the Codrington sandy barrier. One of these inlets was enlarged and was still open 4 years later. From available data, it seems that this barrier remained continuous for the last 250 years before Hurricane Irma. At a longer timescale, very high-resolution seismic exploration combined with sediment cores sampled in Codrington Lagoon were used to investigate Irma deposits and environmental changes for the last 3700 years. The evolution from a low-energy small and shallow lagoon to the modern wide and high-energy lagoon recorded by the lagoon sediment fill was related to both long-term sea level rise and subsidence. The top of the lagoon fill consists of a thick and extensive sand sheet recording an abrupt increase in energy. Given its location at the top of the cores and its very recent age, supported by short-lived radionuclide data, together with large inlets opening and barrier erosion after Irma that imply a large sand supply to the lagoon, this sand sheet was attributed to Hurricane Irma. From our cores, it appears that this deposit is unique over more than 3700 years. Both the opening of a new inlet and the thick upper sand sheet support the exceptional character of Irma at the scale of centuries to millennia. Our study reinforces the idea that Hurricane Irma was exceptional in terms of intensity and may be associated with global warming.

The Roman to medieval landscape transformation at Aardenburg (southern The Netherlands) based on palynology and diatom analysis

The region of Bruges (Flanders, Belgium) was an economic and cultural centre during the Late Middle Ages because it was connected to the North Sea via a large tidal inlet called the Zwin, along which smaller towns developed. One of these towns was Aardenburg (Zeeland, The Netherlands), which developed from a Roman castellum to become one of the important medieval towns in the hinterland of Bruges. Unfortunately, archaeological, historical and (palaeo)environmental data about the Roman to medieval evolution of the Zwin area are scarce. However, the continuous occupation of Aardenburg during the first millennium AD and its location on a Pleistocene sand ridge bordering the coastal plain provide a unique opportunity to investigate the natural dynamics of the coastal evolution and the interplay with the human impact that shaped the Zwin region before its heyday. The variable character of the depositional environments on the dynamic coastal plain makes local environmental studies essential for understanding larger patterns, which were previously reduced to a simplistic outdated model over the entire region. Palynological and diatom assemblages of two sequences in Aardenburg allow the reconstruction of the terrestrial and aquatic palaeoenvironments from the Middle Holocene to the high Middle Ages. The results reveal landscape evolution in relation to woodlands, peat bogs, coastal environments and human presence, consistent with previous regional landscape evolution. A distinct increase in marine influence during the Roman and early medieval periods, when human activities played a significant role, was followed by an increase in inland indicators from the high medieval period onwards. This evolution is in accordance with the expansion of the town and the reclamation of the coastal landscape as it evolved to become a cultural centre in the Late Middle Ages.

Gravity currents from a constant inflow on unbounded uniform slopes

In this study we conducted laboratory experiments to examine the gravity currents produced from a constant inflow propagating on unbounded uniform slopes in the range 0∘≤θ≤15∘. In the experiments, the inlet Reynolds number and the slope angle were varied systematically. The study carried out dimensional analysis and quantified five dimensionless parameters, thereby characterizing the development of gravity currents. Top-view images shown in the experiments exhibited gravity currents in an elongated shape when propagating on steeper slopes larger than 6∘ but a round shape on milder slopes less than 3∘. The study finds that the five dimensionless parameters, which are functions of the slope angle, have near constant values for sufficiently large inlet Reynolds number, suggesting that the flow is approaching the regime of Reynolds number independence. The results from our experiments are expected to be applicable to gravity currents produced from a constant inflow on unbounded uniform slopes in larger scale natural or man-made environments.

Experimental Study of the Influence of the Geometrical Parameters of the Radial Labyrinth Pump on the Pump’s Operating Parameters and Performance

Centrifugal pumps are the most common machines responsible for the increase in hydraulic energy in a piping system. Their proper design, operation, and maintenance have a strong influence on the performance of technological processes carried out in many industrial units. For the ultra-low specific speed (nq &lt; 10) application, there is no economical reason for these pumps to be used. This is caused by an increase in internal losses in the pump. The article concerns the problem of the hydraulic operation of a new type of labyrinth pump—the radial labyrinth pump (RLP), which is a developed axial unit. The main research method involves the experimental research of hydraulic sets consisting of passive and active discs. The analyses were preceded by dimensional analysis and experimental planning. The study investigates the influence of a chosen structural parameter of both discs on the process of energy conversion obtained in the pump. The influence of parameters such as number, depth and width of the grooves, as well as inlet angle and diameter on the properties of the pump was studied and discussed in detail. The essential novelty of the article is the recognition of the hydraulic performance of the RLP with grooved discs. To extend the scope of the conducted research for the chosen hydraulic sets, a comparison of the mutual cooperation of an active disc with a smooth and grooved passive one was conducted. It was identified that not every geometric relationship of the parameters of the active and passive discs results in an increase in head with respect to cooperation with a smooth passive disc (motionless). The highest head and high efficiencies were obtained for sets with short channels with large inlet diameters—zk12 and zk13—ratios for zk12 d1ap/d2ap = 0.78, and for zk13 zk12 d1ap/d2ap = 0.81. Based on the obtained results, preliminary recommendations for the construction were made.

A Case of Antenatal Diagnosis of Ectopia Cordis with Cardiac Disease

Ectopic cordis is a rare anomaly with incidence of 5.5 to 7.9 per one million. In this anomaly, fetal heart is displayed towards outside of the thoracic cavity partially or completely. We describe a case of antenatal diagnosis of Thoracic Ectopia Cordis (EC) with CongenitalHeartDisease (CHD) without any other extracardiac malformations. The mother was referred to our center at 18 weeks of gestation due to abnormal sonography. Fetal Echocardiographic examination showed isolated thoracic ectopia cordis with Double Outlet Right Ventricle (DORV), large inlet to outlet Ventricular Septal Defect (VSD), malposition of Aorta, Pulmonary Atresia with retrograde flow, narrow Pulmonary Artery (PA) and PA branches. Amniocentesis and sonography revealed no other anomaly or chromosomal derangement. Because the diagnosis of Ectopia cordis may be difficult in the fetal period due to multiple factors, meticulous attention should be paid for true diagnosis.

Investigation of the Liquid Cooling and Heating of a Lithium-Ion Battery Package for an Electric Vehicle

The temperature of an electric vehicle battery system influences its performance and usage life. In order to prolong the lifecycle of power batteries and improve the safety of electric vehicles, this paper designs a liquid cooling and heating device for the battery package. On the device designed, we carry out liquid cooling experiments and preheating experiments. Then, a three-dimensional numerical model for the battery package is built, and its effectiveness is validated by comparing the simulation results with the experimental outcomes in terms of battery surface temperature and temperature difference. Furthermore, we investigate the influences of the liquid flow rate and the inlet temperature on the maximum temperature and temperature difference of batteries by the cooling models and preheating models. Results show that: at the cooling stage, it is able to keep each battery working at an optimal temperature under different discharge conditions by changing the flow and the inlet temperature of liquid; at the heating stage, large flow rates and high inlet temperatures are able to speed up the preheating process, thereby saving time of the drivers.

Multiobjective and multicondition optimization for a gas–liquid mixed-flow pump based on a three-dimensional inverse design

The mixed-flow pump performs well in transporting gas–liquid mixtures with large flow rates and high inlet gas volume fractions. However, its extensive development is still limited by the operating range and poor overall performance. In this study, a multiobjective and multicondition optimization methodology for improving the gas–liquid flow performance of a mixed-flow pump based on the inverse design is proposed. The impeller blade load is taken as the optimization variable. Moreover, the Euclidean distances of the pressure increment, efficiency, and gas volume fraction in the diffuser are adopted as optimization objectives. Results show that the numerical methodology is verified by the pressure increment and gas distribution obtained in the tests of the original pump. Optimized results demonstrate that the slope of the straight line, the stacking angle at the hub, and the intersection point of the rear parabola and the straight line significantly affect the objectives. The increased load of the first half of the impeller and the reduced load of the second half may improve the comprehensive performance of mixed-flow pumps. The blade length and wrap angle are reduced after optimization, which changes the inlet and outlet angles and deflection of the blade, thereby helping to enhance the cognition of mixed-flow pump performance optimization.

CaptiveSpray Differential Ion Mobility Spectrometry Device with Enhanced Ion Transmission and Improved Resolving Power

A performance enhanced CaptiveSpray differential ion mobility device was designed and constructed by incorporating a circular channel and a gas flow homogenizing channel (GFHC) between the CaptiveSpray ion source and planar differential ion mobility spectrometry (DMS). The GFHC was used to reduce gas flow heterogeneity prior to the entrance of the DMS device. The optimal flared entrance greatly reduces gas flow velocity at the inlet region owing to its relatively large gas inlet interface, which assists in reducing disparities between the minimum and maximum gas velocity along the x-axis. The circular electrode was machined with channels along the x- and y-axis for the passage of auxiliary gas and was applied with a potential to focus the incoming ions from the CaptiveSpray source into the DMS channel. Using reserpine as a reference standard, substantial signal enhancement was achieved with a concomitant reduction of the peak width in the ionogram.

On the importance of fluidic manifold design and orientation on flow boiling instability in microchannel heat sinks

This study proposes simple modifications in the design of inlet and outlet plenum and inlet and outlet port orientations to suppress the instabilities in two-phase microchannel heat sinks. We investigate three designs which include small-volume inlet and outlet plenums, large-inlet small-outlet volume plenums, and small-inlet large-outlet volume plenums, at four orientations, i.e., upward facing horizontal flow (+0°), downward facing horizontal flow (-0°), and vertically aligned upward (+90°) and downward flows (-90°). The inlet-outlet port orientation is perpendicular to the plane of the microchannel footprint area. It is found that the large inlet plenum decreases the backflow of vapour for all orientations. An increase in the size of the outlet plenum in the upward facing horizontal flow configuration helps to accommodate sudden volume increase due to vapour to minimise the fluctuations/instability. Conversely, the opposite directions of flow and buoyancy force in the case of a large volume outlet manifold significantly increase the tendency of backflow of vapour for the case of downward facing horizontal flow and vertically aligned downward flow orientations. The study uses these insights to propose simple guidelines for the design of inlet and outlet plenum and port orientations to suppress the instability in two-phase microchannel heat sinks at high heat fluxes and under unfavourable orientations.

Phenology of harbor seal pupping and the influence of weather on pup counts, investigated by UAV

AbstractSurveys of harbor seals to assess pup production in Denmark are conducted at the assumed breeding season peak between 9 and 15 hr at winds &lt;10 m/s, with no precipitation at least 6 hr before observations and at low tide in areas with a significant tidal range. Harbor seal pups can swim immediately after birth, so the fraction available for counting likely varies according to conditions. In the Limfjord, a separate harbor seal population is living in a large inlet in northern Denmark where &gt;95% of pups are born at two haul‐out sites situated 4 km apart. Drone surveys of these two haul‐outs were conducted throughout the breeding seasons during 2017–2019. The effects of weather conditions and timing of surveys on counts were analyzed by generalized additive mixed models. The best‐performing model included date and wind speed. Pup counts grew from the onset of the observation period and were predicted to peak on June 22. Wind speed had a linear relationship with pup counts and &gt; 50% more pups were counted at 5 m/s than at 1 m/s. To achieve representative pup counts careful consideration of survey conditions and possibly correction for these effects are necessary.

Spinal anesthesia for a neonate with complex congenital heart disease for lower limb surgery

A neonate with complex congenital heart disease was referred for patent ductus arteriosus (PDA) stenting, who had an ulceration of the dorsum of the foot secondary to extravasation injury. Echo showed situs solitus, levocardia, atrioventricular concordance, double-outlet right ventricle, large inlet with conoventricular ventricular septal defect, bidirectional shunt, D-posed aorta, pulmonary atresia, confluent good-sized branch pulmonary arteries, left arch, no coarctation, and tortuous PDA arising from the base of arch supplying the branch pulmonary artery confluence. Three days later, PDA stenting was done. As limb ulceration progressed to cellulitis, he was posted for debridement and VAC application 6 days after PDA stenting. It was performed under subarachnoid block with 0.5% bupivacaine heavy 0.6 ml through L4-L5 interspace using a 24G needle. Intraoperatively, saturation and hemodynamic variables remained stable. Skin grafting was performed 3 days later under spinal anesthesia with an unremarkable intraoperative and postoperative period.

Vortex structure control based bleed in axial compressor cascade with tip clearance using large eddy simulation

Abstract As an essential component, the bleed system plays a critical role in supplying turbine cooling air, guaranteeing stage matching, pressurizing the cabin, and de-icing at the wing and engine inlet. However, the extraction of the bleeding air from the compressor causes the engine efficiency degradation and thrust deficit. Therefore, flow control based on bleed is conducted to compensate the bleed induced disadvantages. The influence of the circumferential bleeding slot location on the tip leakage vortex and passage vortex controlling in a compressor cascade with the tip clearance is numerically studied using large eddy simulation. Three bleed configurations and the smooth casing configuration are investigated. 17.11% loss reduction is obtained through bleeding at 10% c x upstream of the blade leading edge with a bleeding rate of 2.76%. The vortex structures and flow patterns are compared and analyzed to reveal the controlling mechanism. Subsequently, the axial vorticity and loss evolution is discussed, and the interaction between the primary flow and bleeding air is revealed. It’s found that bleeding slot placed within the blade passage is exposed into a highly static pressure gradient, and this causes the bleeding air flows into and spills out the bleeding slot and leads to unnecessary loss. Moreover, the influence of large bleeding rate and inlet boundary layer is assessed.