To improve the efficiency and accuracy of path planning for fan inspection tasks in thermal power plants,this paper proposes an intelligent inspection robot path planning scheme based on an improved A^(*)algorithm.The...To improve the efficiency and accuracy of path planning for fan inspection tasks in thermal power plants,this paper proposes an intelligent inspection robot path planning scheme based on an improved A^(*)algorithm.The inspection robot utilizes multiple sensors to monitor key parameters of the fans,such as vibration,noise,and bearing temperature,and upload the data to the monitoring center.The robot’s inspection path employs the improved A^(*)algorithm,incorporating obstacle penalty terms,path reconstruction,and smoothing optimization techniques,thereby achieving optimal path planning for the inspection robot in complex environments.Simulation results demonstrate that the improved A^(*)algorithm significantly outperforms the traditional A^(*)algorithm in terms of total path distance,smoothness,and detour rate,effectively improving the execution efficiency of inspection tasks.展开更多
Given two graphs G and H,the Ramsey number R(G,H)is the smallest positive integer N such that every 2-coloring of the edges of K_(N)contains either a red G or a blue H.Let K_(N-1)■K_(1,k)be the graph obtained from K_...Given two graphs G and H,the Ramsey number R(G,H)is the smallest positive integer N such that every 2-coloring of the edges of K_(N)contains either a red G or a blue H.Let K_(N-1)■K_(1,k)be the graph obtained from K_(N-1)by adding anew vertexνconnecting k vertices of K_(N-1).A graph G withχ(G)=k+1 is called edge-critical if G contains an edge e such thatχ(G-e)=k.A considerable amount of research has been conducted by previous scholars on Ramsey numbers ofgraphs.In this study,we show that for an edge-critical graph G with x(G)=k+1,when k≥2,1≥2,and n is sufficiently large,R(G,K_(1)+nK_(t))=knt+1 and r,(G,K_(1)+nK_(t))=(k-1)nt+1.展开更多
The tectonic evolution of Borneo and the affiliation between Southern and Northern Borneo remains unclear.The Rajang and Crocker Fan sediments,as one of the largest ancient submarine fans in Southeast Asia have witnes...The tectonic evolution of Borneo and the affiliation between Southern and Northern Borneo remains unclear.The Rajang and Crocker Fan sediments,as one of the largest ancient submarine fans in Southeast Asia have witnessed the tectonic evolution of Borneo since at least the late Mesozoic.In this study,we present laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)U-Pb dating and Hf isotopic results of detrital zircons from the Trusmadi and Crocker formations within the Crocker Fan of Sabah,Northern Borneo.Our results,coupled with previous data,show that the Crocker Fan sediments in Sabah of Northern Borneo display similar age spectra to the Rajang Fan sediments in Sarawak of Central Borneo,with two major age clusters at 130-80 and 280-200 Ma.Further provenance analysis based on mineral shape with a prismatic characteristic and similar detrital zircon Hf isotopes of the two formations illustrates that the Jurassic-Cretaceous and partly Triassic detrital zircons of the Crocker and Rajang Fan sediments were derived from the erosion of contemporaneous magmatic rocks;part of Permian-Triassic ones could be the recycling of the Jurassic deposits in SW Borneo.The initial provenance of these Permian-Triassic detritus could be synchronous magmatic rocks in the Tin belt of the Malay Peninsula.Combining with previous data,we propose that the entire Borneo continent,including both Southern and Northern Borneo,developed a common Mesozoic continental magmatic arc.Moreover,we postulate that the Rajang and Crocker fans formed in a fore-arc extensional rift basin related to the retreat of the subducted Paleo-Pacific Plate beneath the Northern Borneo margin.展开更多
Fan deltas are usually constructed through episodic flood event with debris flow transforming to hyper-concentrated flow during sediments proceeding. However, the role of topography in controlling the flow transformat...Fan deltas are usually constructed through episodic flood event with debris flow transforming to hyper-concentrated flow during sediments proceeding. However, the role of topography in controlling the flow transformation and sediments aggradation has been less studied. This constrain studies of sediment distribution and understanding of graded profile. For lake basin sequences, geomorphological control is much stronger than lake level rise and fall. Under extreme conditions, sediments can still prograde when the lake level rises. Therefore, describing the influence of geomorphology on the flow transformation and stacking pattern of the lobes can provide a deeper understanding of the controlling factors of the lake basin stratigraphy sequence. Xiligou lake (XLG) fan delta from Xisai Basin provides an optimal case for addressing this issue. Three lobes developed on the XLG fan delta with significant differences in their morphologies, architectures, lithofacies, sediment distributions and topographies. Through trenching, drone photography, and satellite data, we analyzed the structure of the sediments and the distribution of sedimentary facies. Based on the analysis of debris flow and hyper-concentrated flow deposits, two transformation models corresponding to different topographies were established. Sediment unloading is caused by a frictional reduction or a sudden momentum loss in the sediments flow's carrying capacity, allowing the debris flow transforms to hyper-concentrated flow and then to stream flow during the movement. The role of topography in controlling sediment flow transformation and sediment distribution is clarified through forces analysis of sediment grain. The topographic gradient of the linear slope is constant, so the direction of fluid movement is consistent with the topographic direction. Therefore, sediment flows move on linear slope without collision with the bed and there is no sudden loss of momentum. The gradual or sudden reduction in topographic gradient of concave slopes forces a constant or sudden change in the direction of fluid movement, which facilitates the unloading of sediments and the transformation of flow. The sudden change of topography forces unloading of viscous component, and the non-viscous component pass over to form hyper-concentrated flow, often accompanied by remobilized large gravels. The graded profile was an equilibrium between the dynamics and resistance of sediment transport. Changes in lake level affect the graded profile by changing the elevation of sediment transport, which is the total gravitational potential energy. The instantaneous graded profile and temporary graded profile are different scales of equilibrium corresponding to hydrodynamic equilibrium and depositional trend respectively. This study reveals the role of geomorphological dynamics in controlling sedimentary body progradation, thus providing a new perspective on the analysis of lake basin stratigraphy sequence.展开更多
Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of...Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of integrating ceiling fans with higher air conditioning setpoints on thermal comfort and energy efficiency in office environments.Field measurements and questionnaire surveys were conducted to evaluate thermal comfort and energysaving potential under varying conditions.Results show that increasing the AC setpoint from 25○C to 27○C,combined with ceiling fan operation,reduced power consumption by 10%,achieving significant energy savings.Survey data confirmed that 85%of participants reported consistent thermal sensations across all conditions,with ceiling fans effectively compensating for higher setpoints through enhanced air circulation.CFDsimulations revealed that mediumspeed ceiling fan operation produced the most uniformairflowdistribution,with an average air velocity of 0.45 m/s,and minimized temperature variations,ensuring balanced thermal conditions.Temperature analysis showed a reduction in hotspots and cold zones,maintaining an average temperature deviation of less than±0.5○C.Predicted Mean Vote(PMV)evaluations at a 27○C setpoint indicated improved thermal comfort,with average PMV values around−0.3,corresponding to a“neutral”thermal sensation.These findings demonstrate the effectiveness of integrating ceiling fans with HVAC systems in achieving energy efficiency and occupant comfort,offering a sustainable approach to reducing AC energy consumption in office environments.展开更多
As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The...As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration.A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed.The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation.The lift and drag characteristics of the aero-propulsion coupling configuration are simulated.The results indicate that the coupling configuration has the most obvious lift augmentation at 12°angle of attack,which can provide an 11.11%increase in lift for the airfoil.At 0°angle of attack,the pressure difference on the lip parts provides the thrust component,which results in a lower drag coefficient.Additionally,the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated.For the two failure conditions,the lift of the coupling configuration is decreased significantly by 27.85%and 26.14%respectively,and the lip thrust is decreased by 70.74%and 56.48%respectively.展开更多
1. Introduction Research on the ground effect of rotor can be traced back to the 1930s1.However, few studies have been conducted on the aerodynamic characteristics of rotors and ducted fans when hovering near a water ...1. Introduction Research on the ground effect of rotor can be traced back to the 1930s1.However, few studies have been conducted on the aerodynamic characteristics of rotors and ducted fans when hovering near a water surface for an extended period.With the emergence of cross-media rotorcraft, rotor wakes interact violently with the water surface to generate large-scale,air–water droplet mixed flows (hereafter referred to as mixed air–water flows). Rotors operating in mixed air–water flows always have aerodynamic performances that are different from those owing to the In-Ground Effect (IGE) and Out-of Ground Effect (OGE). Accordingly, this effect is called the Near-Water Effect (NWE) of the rotor2,and it usually causes thrust loss and torque increase.展开更多
The study on sand body connectivity and distribution patterns is of great significance for well emplacement and injection-production pattern analysis in the A oilfield of the Weixi?nan Sag currently at a pre-developme...The study on sand body connectivity and distribution patterns is of great significance for well emplacement and injection-production pattern analysis in the A oilfield of the Weixi?nan Sag currently at a pre-development stage.Based on the current drilling data,seismic data,and fault development characteristics,this study investigates the connectivity,geometric morphology,planar distribution,and vertical evolution of composite sand bodies(multi-stage superimposed channel sand bodies)within the fault block using seismic forward and inversion modeling.The El3I oil layer group in the third member of the Liushagang Formation is developed in the fan delta-front sub-facies,which mainly consists of subaqueous distributary channels.The thickness of single-stage subaqueous distributary channel sand bodies ranges from 2 to 6 m,and the width of composite channel sand bodies varies from 50 to 100 m.Under the long-term transgression background,the subaqueous distributary channels in the El3I oil layer group are relatively narrow,forming superimposed and continuous composite channel sand bodies through lateral migration and vertical stacking.The long-term base-level cycles control the width of subaqueous distributary channels,while the mid-term base-level cycles control the thickness of these channels.The subaqueous distributary channels developed during the late stage of mid-term base-level fall are thicker than those formed during the early stage.Accordingly,quantitative relationships between channel thickness and width are established for the early and late stages of mid-term base-level fall,to finely depict the evolution patterns of channel sand body geometry and stacking styles across different stages.These findings provide important guidance for accurately predicting the planar distribution and channel width of composite subaqueous distributary channels at different stages of the mid-term baselevel cycles.展开更多
An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(...An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(CT)on the stall margin recovery.An operating cycle is proposed based on the hysteresis effect of harmonic flap oscillation of airfoils and parallel compressor theory to explain the pressure characteristic of the fan under twin swirl inlets.Twin swirls are observed to reduce the stall margin of the fan,and the circumferential location where the spike is detected turns to the intersection area of the twin swirl.The IBC CT is proven to extend the stall margin of the fan for 12.7%–22.3%when subjected to inlet swirls with an efficiency loss of around 1%.The IBC CT helps to reduce the size of the operating cycle of the fan by redistributing the blade loading and adding the system damping to dissipate the perturbation energy.展开更多
Acquiring acoustic modes with high quality data in larg e-scale nacelles is quite challenging in the engine industry because of the complex configuration,high flow speed,tremendous number of acoustic modes,and some ot...Acquiring acoustic modes with high quality data in larg e-scale nacelles is quite challenging in the engine industry because of the complex configuration,high flow speed,tremendous number of acoustic modes,and some other extraordinary interference.A complete procedure for mode detection in the engine industry that is applicable to full-size situations is proposed.Two diffe rent array patterns are adopted:a circular array for azimuthal modes in both the intake and bypass ducts,and a rotating linear array for radial modes only in the bypass duct.The azimuthal locations of sensors in the circumferential array are non-uniformly distributed to get more modes than the Nyquist limit.For each individual channel signal,an adaptive resampling method is adopted to reduce the components incoherent with source rotation and frequency shifts caused by shaft speed variation.At high flow speeds,boundary turbulence contaminates acoustic signals of wall-flush mounted sensors.A wavenumber decomposition method is used to separate the acoustic part and the dynamic pressure part in the bypass duct during radial mode detection.Finally,both the azimuthal and radial acoustic modes in bypass and intake ducts are acquired successfully.展开更多
This study explores the influence of rotor blade angle on stall inception in an axial fan by means of numerical simulations grounded in the Reynolds-Averaged Navier-Stokes(RANS)equations and the Realizable k-εturbule...This study explores the influence of rotor blade angle on stall inception in an axial fan by means of numerical simulations grounded in the Reynolds-Averaged Navier-Stokes(RANS)equations and the Realizable k-εturbulence model.By analyzing the temporal behavior of the outlet static pressure,along with the propagation velocity of stall inception,the research identifies distinct patterns in the development of stall.The results reveal that stall inception originates in the second rotor impeller.At a blade angle of 27°,the stall inception follows a modal wave pattern,while in all other cases,it assumes the form of spike-type stall.The flow field associated with spike stall inception demonstrates a relatively uniform gradient in the radial direction,whereas the modal wave stall case displays a distinctive“L”-shaped propagation feature.At blade angles of multiple stall inceptions are observed.-9°and-18°,These phenomena initiate at the blade’s leading edge,propagate along both axial and radial directions,and transition dynamically between single and multiple inception states.展开更多
Jet ventilation is widely used in the ventilation design of highway and railway tunnels as an important air supply method during tunnel operation and disaster periods.This ventilation method has also been applied for ...Jet ventilation is widely used in the ventilation design of highway and railway tunnels as an important air supply method during tunnel operation and disaster periods.This ventilation method has also been applied for fire control in immersed tunnels.We conduct numerical simulations using computational fluid dynamics(CFD)to study positive ventilation in the upstream and reverse ventilation in the downstream(P-R)for an extra-wide immersed tunnel.The effects of fire source location and jet fan air velocity response strategy on the ceiling temperature decay,carbon monoxide(CO)distribution,and smoke exhaust efficiency were investigated for varying fire source locations.The results show that flames will be tilted to the side of the jet fan with a smaller air velocity.Additionally,the jet fan air velocity should be adjusted based on the relative distance between the fire source and the smoke vent.Among the studied scenarios,the most effective outcome was achieved when the air velocity was adjusted to 25 m/s on the side near the smoke vent.Also in this scenario,the phenomenon of smoke deposition was effectively mitigated and the average smoke exhaust efficiency reached 87%.Moreover,we found that the temperature decay of the tunnel follows an exponential decay law.The temperature decay rate is significantly higher on the side closest to the smoke vent compared to the farther side.This research provides a theoretical basis for smoke control strategies for fires that occur in immersed tunnels.展开更多
Rotating Instability (RI) is a typical unsteady flow phenomenon in compressors and may cause severe aerodynamic noise and even potential nonsynchronous vibration. Most studies of RI are based on the uniform inflow, ig...Rotating Instability (RI) is a typical unsteady flow phenomenon in compressors and may cause severe aerodynamic noise and even potential nonsynchronous vibration. Most studies of RI are based on the uniform inflow, ignoring the influence of inlet distortions. This study investigates the mechanism of RI in a transonic rotor through full-annulus unsteady simulations, with a particular focus on the effects of boundary layer ingesting distortions. The results show that at the uniform inflow, the RI fluctuations with the broadband hump can be observed over a relatively wide mass flow rate range, and its origin can be attributed to the coupling effect between the tip leakage flow and shear layer instability. At the inlet distortions, the broadband hump only occurs with partial circumferential locations. This kind of flow phenomenon is defined as Partial Rotating Instability (PRI). The PRI only occurs in a narrower mass flow rate range in which the circumferential range of strong shear is sufficiently large and the self-induced unsteady effects are strong enough. Further, this study confirms that the averaged tip leakage flow axial momentum at the onset of RI or PRI is close, so it can be used as the parameter to determine whether RI or PRI occurs.展开更多
Bird impact is one of the most dangerous threats to flight safety. The consequences of bird impact can be severe and, therefore, the aircraft components have to be certified for a proven level of bird impact resistanc...Bird impact is one of the most dangerous threats to flight safety. The consequences of bird impact can be severe and, therefore, the aircraft components have to be certified for a proven level of bird impact resistance before being put into service. The fan rotor blades of aeroengine are the components being easily impacted by birds. It is necessary to ensure that the fan rotor blades should have adequate resistance against the bird impact, to reduce the flying accidents caused by bird impacts. Using the contacting-impacting algorithm, the numerical simulation is carded out to simulate bird impact. A three-blade computational model is set up for the fan rotor blade having shrouds. The transient response curves of the points corresponding to measured points in experiments, displacements and equivalent stresses on the blades are obtained during the simulation. From the comparison of the transient response curves obtained from numerical simulation with that obtained from experiments, it can be found that the variations in measured points and the corresponding points of simulation are basically the same. The deforming process, the maximum displacements and the maximum equivalent stresses on blades are analyzed. The numerical simulation verifies and complements the experiment results.展开更多
文摘To improve the efficiency and accuracy of path planning for fan inspection tasks in thermal power plants,this paper proposes an intelligent inspection robot path planning scheme based on an improved A^(*)algorithm.The inspection robot utilizes multiple sensors to monitor key parameters of the fans,such as vibration,noise,and bearing temperature,and upload the data to the monitoring center.The robot’s inspection path employs the improved A^(*)algorithm,incorporating obstacle penalty terms,path reconstruction,and smoothing optimization techniques,thereby achieving optimal path planning for the inspection robot in complex environments.Simulation results demonstrate that the improved A^(*)algorithm significantly outperforms the traditional A^(*)algorithm in terms of total path distance,smoothness,and detour rate,effectively improving the execution efficiency of inspection tasks.
基金supported by the National Key Research and Development Program of China(2023YFA1010200,2020YFA0713100)the National Natural Science Foundation of China(12071453)the Innovation Program for Quantum Science and Technology(2021ZD0302902).
文摘Given two graphs G and H,the Ramsey number R(G,H)is the smallest positive integer N such that every 2-coloring of the edges of K_(N)contains either a red G or a blue H.Let K_(N-1)■K_(1,k)be the graph obtained from K_(N-1)by adding anew vertexνconnecting k vertices of K_(N-1).A graph G withχ(G)=k+1 is called edge-critical if G contains an edge e such thatχ(G-e)=k.A considerable amount of research has been conducted by previous scholars on Ramsey numbers ofgraphs.In this study,we show that for an edge-critical graph G with x(G)=k+1,when k≥2,1≥2,and n is sufficiently large,R(G,K_(1)+nK_(t))=knt+1 and r,(G,K_(1)+nK_(t))=(k-1)nt+1.
基金jointly supported by the Scientific Research Foundation of Third Institute of Oceanography,Ministry of Natural Resources,Xiamen(No.2018002)the Guangxi Natural Science Fundation(No.2022GXNSFBA035588)+1 种基金the National Natural Science Foundation of China(Nos.41506050,41402193)the Scientific Research Foundation of Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration(No.19-185-17-09)。
文摘The tectonic evolution of Borneo and the affiliation between Southern and Northern Borneo remains unclear.The Rajang and Crocker Fan sediments,as one of the largest ancient submarine fans in Southeast Asia have witnessed the tectonic evolution of Borneo since at least the late Mesozoic.In this study,we present laser ablation inductively coupled plasma mass spectrometer(LA-ICP-MS)U-Pb dating and Hf isotopic results of detrital zircons from the Trusmadi and Crocker formations within the Crocker Fan of Sabah,Northern Borneo.Our results,coupled with previous data,show that the Crocker Fan sediments in Sabah of Northern Borneo display similar age spectra to the Rajang Fan sediments in Sarawak of Central Borneo,with two major age clusters at 130-80 and 280-200 Ma.Further provenance analysis based on mineral shape with a prismatic characteristic and similar detrital zircon Hf isotopes of the two formations illustrates that the Jurassic-Cretaceous and partly Triassic detrital zircons of the Crocker and Rajang Fan sediments were derived from the erosion of contemporaneous magmatic rocks;part of Permian-Triassic ones could be the recycling of the Jurassic deposits in SW Borneo.The initial provenance of these Permian-Triassic detritus could be synchronous magmatic rocks in the Tin belt of the Malay Peninsula.Combining with previous data,we propose that the entire Borneo continent,including both Southern and Northern Borneo,developed a common Mesozoic continental magmatic arc.Moreover,we postulate that the Rajang and Crocker fans formed in a fore-arc extensional rift basin related to the retreat of the subducted Paleo-Pacific Plate beneath the Northern Borneo margin.
基金the Natural Science Foundation of China(42272124)the National Key R&D Program of China(2023YFF0804302)Quantitative anatomy of shallow fan deltas in western China project directed by Research Institute of Petroleum Exploration and Development(2020D-5008-03).
文摘Fan deltas are usually constructed through episodic flood event with debris flow transforming to hyper-concentrated flow during sediments proceeding. However, the role of topography in controlling the flow transformation and sediments aggradation has been less studied. This constrain studies of sediment distribution and understanding of graded profile. For lake basin sequences, geomorphological control is much stronger than lake level rise and fall. Under extreme conditions, sediments can still prograde when the lake level rises. Therefore, describing the influence of geomorphology on the flow transformation and stacking pattern of the lobes can provide a deeper understanding of the controlling factors of the lake basin stratigraphy sequence. Xiligou lake (XLG) fan delta from Xisai Basin provides an optimal case for addressing this issue. Three lobes developed on the XLG fan delta with significant differences in their morphologies, architectures, lithofacies, sediment distributions and topographies. Through trenching, drone photography, and satellite data, we analyzed the structure of the sediments and the distribution of sedimentary facies. Based on the analysis of debris flow and hyper-concentrated flow deposits, two transformation models corresponding to different topographies were established. Sediment unloading is caused by a frictional reduction or a sudden momentum loss in the sediments flow's carrying capacity, allowing the debris flow transforms to hyper-concentrated flow and then to stream flow during the movement. The role of topography in controlling sediment flow transformation and sediment distribution is clarified through forces analysis of sediment grain. The topographic gradient of the linear slope is constant, so the direction of fluid movement is consistent with the topographic direction. Therefore, sediment flows move on linear slope without collision with the bed and there is no sudden loss of momentum. The gradual or sudden reduction in topographic gradient of concave slopes forces a constant or sudden change in the direction of fluid movement, which facilitates the unloading of sediments and the transformation of flow. The sudden change of topography forces unloading of viscous component, and the non-viscous component pass over to form hyper-concentrated flow, often accompanied by remobilized large gravels. The graded profile was an equilibrium between the dynamics and resistance of sediment transport. Changes in lake level affect the graded profile by changing the elevation of sediment transport, which is the total gravitational potential energy. The instantaneous graded profile and temporary graded profile are different scales of equilibrium corresponding to hydrodynamic equilibrium and depositional trend respectively. This study reveals the role of geomorphological dynamics in controlling sedimentary body progradation, thus providing a new perspective on the analysis of lake basin stratigraphy sequence.
基金support by the National Science and Technology Council under Grant No.NSTC 112-2221-E-167-017-MY3.
文摘Heating,Ventilation,andAir Conditioning(HVAC)systems are critical formaintaining thermal comfort in office environments which also crucial for occupant well-being and productivity.This study investigates the impact of integrating ceiling fans with higher air conditioning setpoints on thermal comfort and energy efficiency in office environments.Field measurements and questionnaire surveys were conducted to evaluate thermal comfort and energysaving potential under varying conditions.Results show that increasing the AC setpoint from 25○C to 27○C,combined with ceiling fan operation,reduced power consumption by 10%,achieving significant energy savings.Survey data confirmed that 85%of participants reported consistent thermal sensations across all conditions,with ceiling fans effectively compensating for higher setpoints through enhanced air circulation.CFDsimulations revealed that mediumspeed ceiling fan operation produced the most uniformairflowdistribution,with an average air velocity of 0.45 m/s,and minimized temperature variations,ensuring balanced thermal conditions.Temperature analysis showed a reduction in hotspots and cold zones,maintaining an average temperature deviation of less than±0.5○C.Predicted Mean Vote(PMV)evaluations at a 27○C setpoint indicated improved thermal comfort,with average PMV values around−0.3,corresponding to a“neutral”thermal sensation.These findings demonstrate the effectiveness of integrating ceiling fans with HVAC systems in achieving energy efficiency and occupant comfort,offering a sustainable approach to reducing AC energy consumption in office environments.
基金the funding support from the Taihang Laboratory,China(No.D2024-1-0201).
文摘As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration.A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed.The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation.The lift and drag characteristics of the aero-propulsion coupling configuration are simulated.The results indicate that the coupling configuration has the most obvious lift augmentation at 12°angle of attack,which can provide an 11.11%increase in lift for the airfoil.At 0°angle of attack,the pressure difference on the lip parts provides the thrust component,which results in a lower drag coefficient.Additionally,the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated.For the two failure conditions,the lift of the coupling configuration is decreased significantly by 27.85%and 26.14%respectively,and the lip thrust is decreased by 70.74%and 56.48%respectively.
文摘1. Introduction Research on the ground effect of rotor can be traced back to the 1930s1.However, few studies have been conducted on the aerodynamic characteristics of rotors and ducted fans when hovering near a water surface for an extended period.With the emergence of cross-media rotorcraft, rotor wakes interact violently with the water surface to generate large-scale,air–water droplet mixed flows (hereafter referred to as mixed air–water flows). Rotors operating in mixed air–water flows always have aerodynamic performances that are different from those owing to the In-Ground Effect (IGE) and Out-of Ground Effect (OGE). Accordingly, this effect is called the Near-Water Effect (NWE) of the rotor2,and it usually causes thrust loss and torque increase.
文摘The study on sand body connectivity and distribution patterns is of great significance for well emplacement and injection-production pattern analysis in the A oilfield of the Weixi?nan Sag currently at a pre-development stage.Based on the current drilling data,seismic data,and fault development characteristics,this study investigates the connectivity,geometric morphology,planar distribution,and vertical evolution of composite sand bodies(multi-stage superimposed channel sand bodies)within the fault block using seismic forward and inversion modeling.The El3I oil layer group in the third member of the Liushagang Formation is developed in the fan delta-front sub-facies,which mainly consists of subaqueous distributary channels.The thickness of single-stage subaqueous distributary channel sand bodies ranges from 2 to 6 m,and the width of composite channel sand bodies varies from 50 to 100 m.Under the long-term transgression background,the subaqueous distributary channels in the El3I oil layer group are relatively narrow,forming superimposed and continuous composite channel sand bodies through lateral migration and vertical stacking.The long-term base-level cycles control the width of subaqueous distributary channels,while the mid-term base-level cycles control the thickness of these channels.The subaqueous distributary channels developed during the late stage of mid-term base-level fall are thicker than those formed during the early stage.Accordingly,quantitative relationships between channel thickness and width are established for the early and late stages of mid-term base-level fall,to finely depict the evolution patterns of channel sand body geometry and stacking styles across different stages.These findings provide important guidance for accurately predicting the planar distribution and channel width of composite subaqueous distributary channels at different stages of the mid-term baselevel cycles.
基金supported by the National Natural Science Foundation of China(Nos.52306035 and 52325602)the Science Center for Gas Turbine Project,China(Nos.P2022-A-II-002-001 and P2022-C-II-003-001)+1 种基金the National Science and Technology Major Project,China(Nos.Y2022-II-0002-0005 and Y2022-II-0003-0006)the Key Laboratory of Pre-Research Management Centre,China(No.6142702200101)。
文摘An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(CT)on the stall margin recovery.An operating cycle is proposed based on the hysteresis effect of harmonic flap oscillation of airfoils and parallel compressor theory to explain the pressure characteristic of the fan under twin swirl inlets.Twin swirls are observed to reduce the stall margin of the fan,and the circumferential location where the spike is detected turns to the intersection area of the twin swirl.The IBC CT is proven to extend the stall margin of the fan for 12.7%–22.3%when subjected to inlet swirls with an efficiency loss of around 1%.The IBC CT helps to reduce the size of the operating cycle of the fan by redistributing the blade loading and adding the system damping to dissipate the perturbation energy.
基金supported by the National Key R&D Program of China(2021YFB3703900)。
文摘Acquiring acoustic modes with high quality data in larg e-scale nacelles is quite challenging in the engine industry because of the complex configuration,high flow speed,tremendous number of acoustic modes,and some other extraordinary interference.A complete procedure for mode detection in the engine industry that is applicable to full-size situations is proposed.Two diffe rent array patterns are adopted:a circular array for azimuthal modes in both the intake and bypass ducts,and a rotating linear array for radial modes only in the bypass duct.The azimuthal locations of sensors in the circumferential array are non-uniformly distributed to get more modes than the Nyquist limit.For each individual channel signal,an adaptive resampling method is adopted to reduce the components incoherent with source rotation and frequency shifts caused by shaft speed variation.At high flow speeds,boundary turbulence contaminates acoustic signals of wall-flush mounted sensors.A wavenumber decomposition method is used to separate the acoustic part and the dynamic pressure part in the bypass duct during radial mode detection.Finally,both the azimuthal and radial acoustic modes in bypass and intake ducts are acquired successfully.
基金the Natural Science Foundation of Hebei Province,China(Grant No.E2022502052)Fundamental Research Funds for the Central Universities,China(Grant No.2022MS081)Fundamental Research Funds for the Central Universities,China(Grant No.2023MS121).
文摘This study explores the influence of rotor blade angle on stall inception in an axial fan by means of numerical simulations grounded in the Reynolds-Averaged Navier-Stokes(RANS)equations and the Realizable k-εturbulence model.By analyzing the temporal behavior of the outlet static pressure,along with the propagation velocity of stall inception,the research identifies distinct patterns in the development of stall.The results reveal that stall inception originates in the second rotor impeller.At a blade angle of 27°,the stall inception follows a modal wave pattern,while in all other cases,it assumes the form of spike-type stall.The flow field associated with spike stall inception demonstrates a relatively uniform gradient in the radial direction,whereas the modal wave stall case displays a distinctive“L”-shaped propagation feature.At blade angles of multiple stall inceptions are observed.-9°and-18°,These phenomena initiate at the blade’s leading edge,propagate along both axial and radial directions,and transition dynamically between single and multiple inception states.
文摘Jet ventilation is widely used in the ventilation design of highway and railway tunnels as an important air supply method during tunnel operation and disaster periods.This ventilation method has also been applied for fire control in immersed tunnels.We conduct numerical simulations using computational fluid dynamics(CFD)to study positive ventilation in the upstream and reverse ventilation in the downstream(P-R)for an extra-wide immersed tunnel.The effects of fire source location and jet fan air velocity response strategy on the ceiling temperature decay,carbon monoxide(CO)distribution,and smoke exhaust efficiency were investigated for varying fire source locations.The results show that flames will be tilted to the side of the jet fan with a smaller air velocity.Additionally,the jet fan air velocity should be adjusted based on the relative distance between the fire source and the smoke vent.Among the studied scenarios,the most effective outcome was achieved when the air velocity was adjusted to 25 m/s on the side near the smoke vent.Also in this scenario,the phenomenon of smoke deposition was effectively mitigated and the average smoke exhaust efficiency reached 87%.Moreover,we found that the temperature decay of the tunnel follows an exponential decay law.The temperature decay rate is significantly higher on the side closest to the smoke vent compared to the farther side.This research provides a theoretical basis for smoke control strategies for fires that occur in immersed tunnels.
基金supports of the National Natural Science Foundation of China(Nos.52076129,92360308,52376027)the Shanghai Municipal Education Commission of China(No.2023-02-4)+1 种基金the Fundamental Research Funds for the Central Universities of Chinathe United Innovation Center(UIC)of Aerothermal Technologies for Turbomachinery of China.
文摘Rotating Instability (RI) is a typical unsteady flow phenomenon in compressors and may cause severe aerodynamic noise and even potential nonsynchronous vibration. Most studies of RI are based on the uniform inflow, ignoring the influence of inlet distortions. This study investigates the mechanism of RI in a transonic rotor through full-annulus unsteady simulations, with a particular focus on the effects of boundary layer ingesting distortions. The results show that at the uniform inflow, the RI fluctuations with the broadband hump can be observed over a relatively wide mass flow rate range, and its origin can be attributed to the coupling effect between the tip leakage flow and shear layer instability. At the inlet distortions, the broadband hump only occurs with partial circumferential locations. This kind of flow phenomenon is defined as Partial Rotating Instability (PRI). The PRI only occurs in a narrower mass flow rate range in which the circumferential range of strong shear is sufficiently large and the self-induced unsteady effects are strong enough. Further, this study confirms that the averaged tip leakage flow axial momentum at the onset of RI or PRI is close, so it can be used as the parameter to determine whether RI or PRI occurs.
文摘Bird impact is one of the most dangerous threats to flight safety. The consequences of bird impact can be severe and, therefore, the aircraft components have to be certified for a proven level of bird impact resistance before being put into service. The fan rotor blades of aeroengine are the components being easily impacted by birds. It is necessary to ensure that the fan rotor blades should have adequate resistance against the bird impact, to reduce the flying accidents caused by bird impacts. Using the contacting-impacting algorithm, the numerical simulation is carded out to simulate bird impact. A three-blade computational model is set up for the fan rotor blade having shrouds. The transient response curves of the points corresponding to measured points in experiments, displacements and equivalent stresses on the blades are obtained during the simulation. From the comparison of the transient response curves obtained from numerical simulation with that obtained from experiments, it can be found that the variations in measured points and the corresponding points of simulation are basically the same. The deforming process, the maximum displacements and the maximum equivalent stresses on blades are analyzed. The numerical simulation verifies and complements the experiment results.
基金Supported by the Science Foundation of Fujian Educational Department (JA03159) the Science ResearchFoundation of Putian University(2004Q003 2004Q002)
