The main objective of the present paper is to review the specific characteristics and performance obtaining conditions of heavy ductile iron(DI) castings,typically applied in windmills industry,such as hubs and rotor ...The main objective of the present paper is to review the specific characteristics and performance obtaining conditions of heavy ductile iron(DI) castings,typically applied in windmills industry,such as hubs and rotor housings.The requirements for high impact properties in DI at low temperatures are part of the ENGJS-400-18U-LT(SRN 1563) commonly referred to as GGG 40.3(DIN 1693).Pearlitic in-uence factor(Px) and antinodularising action factor(K1) were found to have an important in-uence on the structure and mechanical properties,as did Mn and P content,rare earth(RE) addition and inoculation power.The presence of high purity pig iron in the charge is extremely beneficial,not only to control the complex factors Px and K1,but also to improve the 'metallurgical quality' of the iron melt.A correlation of C and Si limits with section modulus is very important to limit graphite nodule flotation.Chunky and surface-degenerated graphite are the most controlled graphite morphologies in windmills castings.The paper concluded on the optimum iron chemistry and melting procedure,Mg-alloys and inoculants peculiar systems,as well as on the practical solutions to limit graphite degeneration and to ensure castings of the highest integrity,typically for this field.展开更多
Difficulties in obtaining component characteristics in the sub-idle state of rotor constrain the simulation capabilities of ground and windmill start-up processes for turbofan engines.This paper proposes a backbone fe...Difficulties in obtaining component characteristics in the sub-idle state of rotor constrain the simulation capabilities of ground and windmill start-up processes for turbofan engines.This paper proposes a backbone feature method based on conventional characteristics parameters to derive the full-state characteristics of fan.The application of the fan’s full-state characteristics in component-level model of turbofan engine enables zero-speed iterative simulation for ground start-up process and windmill simulation for windmill start-up process,thereby improving the simulation capability of sub-idle state during turbofan engine start-up.展开更多
A brief description of the windmills from the second millennium BC to the Renaissance is presented. This survey is a part of several studies conducted by the authors on technology in the ancient world. The windmills a...A brief description of the windmills from the second millennium BC to the Renaissance is presented. This survey is a part of several studies conducted by the authors on technology in the ancient world. The windmills are the first motor, other than human muscles, and are the ancestors of the modem wind turbines. Some authors' virtual reconstructions of old windmills are also presented. The paper shows that the operating principle of many modem machines had already been conceived in the ancient times by using a technology that was more advanced than expected, but with two main differences, as follows: Similar tasks were accomplished by using much less energy; and the environmental impact was nil or very low. Modem designers should sometimes consider simplicity rather than the use of a large amount of energy.展开更多
Let G be a graph. A bipartition of G is a bipartition of V (G) with V (G) = V<sub>1</sub> ∪ V<sub>2</sub> and V<sub>1</sub> ∩ V<sub>2</sub> = ∅. If a bipartition satis...Let G be a graph. A bipartition of G is a bipartition of V (G) with V (G) = V<sub>1</sub> ∪ V<sub>2</sub> and V<sub>1</sub> ∩ V<sub>2</sub> = ∅. If a bipartition satisfies ∥V<sub>1</sub>∣ - ∣V<sub>2</sub>∥ ≤ 1, we call it a bisection. The research in this paper is mainly based on a conjecture proposed by Bollobás and Scott. The conjecture is that every graph G has a bisection (V<sub>1</sub>, V<sub>2</sub>) such that ∀v ∈ V<sub>1</sub>, at least half minuses one of the neighbors of v are in the V<sub>2</sub>;∀v ∈ V<sub>2</sub>, at least half minuses one of the neighbors of v are in the V<sub>1</sub>. In this paper, we confirm this conjecture for some bipartite graphs, crown graphs and windmill graphs.展开更多
Taking the model for propeller transport aircraft as the research object,according to the transient windmill characteristics in the process of stop feathering and starting in the air,the simulation calculation of diff...Taking the model for propeller transport aircraft as the research object,according to the transient windmill characteristics in the process of stop feathering and starting in the air,the simulation calculation of different flight heights,blade angles and rotation speeds was carried out,and the transient windmill resistance of the propeller was quantitatively given.The engine torque was calculated by using the simulation model are compared and verified using the flight test data,and the maximum error was 74%.In the windmill state,the airflow works on the propeller,and the airflow velocity behind the propeller disk decreases,wrapping the entire nacelle surface.In the process of parking feathering,the blade angle decreases slightly at first,and then increases rapidly under the action of the large⁃pitch oil pressure,and the speed of rotation increases gradually.When the blade angle at 30°,the windmill resistance at-108 kgf.In the process of starting,the propeller speed increases and the propeller resistance increases first and decreases.When the propeller returns to 14°,the transient windmill resistance at-1720 kgf.展开更多
Ground based, wind energy extraction systems have reached their maximum capability. The limitations of current de-signs are: wind instability, high cost of installations, and small power output of a single unit. The w...Ground based, wind energy extraction systems have reached their maximum capability. The limitations of current de-signs are: wind instability, high cost of installations, and small power output of a single unit. The wind energy industry needs of revolutionary ideas to increase the capabilities of wind installations. This article suggests a revolutionary innovation which produces a dramatic increase in power per unit and is independent of prevailing weather and at a lower cost per unit of energy extracted. The main innovation consists of large free-flying air rotors positioned at high altitude for power and air stream stability, and an energy cable transmission system between the air rotor and a ground based electric generator. The air rotor system flies at high altitude up to 14 km. A stability and control is provided and systems enable the changing of altitude. This article includes six examples having a high unit power output (up to 100 MW). The proposed examples provide the following main advantages: 1) Large power production capacity per unit—up to 5,000 - 10,000 times more than conventional ground-based rotor designs;2) The rotor operates at high altitude of 1 - 14 km, where the wind flow is strong and steady;3) Installation cost per unit energy is low;4) The installation is environmentally friendly (no propeller noise).展开更多
An investigation was conducted to install wind farm to supply electrical power to the village of Ras Munif, the highest elevation in Jordan. The village installed capacity load was found to be 500 kW. A 25 windmills, ...An investigation was conducted to install wind farm to supply electrical power to the village of Ras Munif, the highest elevation in Jordan. The village installed capacity load was found to be 500 kW. A 25 windmills, 20 kW each, forming the wind farm was found to be the best choice to supply the village with 100% of its needed power. The windmills will be spaced 50 meters along an unobstructed continuous wind flow location, along sloping sides of Ras Munif Mountain, alongside service road. The village load bus will be connected directly to both the output of wind farm inverter output bus and to the national grid bus. Both buses supply the needed power. The power flow was found to be supplied by the wind farm, except when the wind speed is low, the village load will be supplied partially or totally by the national grid bus.展开更多
Given the steady increase in use of alternative energy sources to supply part of the energy demand of the world, and considering that Mexico has enough wind resources to produce all the electricity required by the cou...Given the steady increase in use of alternative energy sources to supply part of the energy demand of the world, and considering that Mexico has enough wind resources to produce all the electricity required by the country, in this work, it is carried out the development of a system of wind resource assessment to determine the volume of water that a windmill pumping system can provide in a specific area. To this end, it has developed a computer program for wind resource assessment by measurements of wind speed, direction, temperature, barometric pressure and relative humidity. Measuring equipments were mounted in a wind measurement tower of 10 m high, within the premises of the University of Quintana Roo which is located along the coast. Until this day, there are records over a period of five months of the variables of wind speed, wind direction, temperature, relative humidity and atmospheric pressure. These variables were used for statistical calculations using the Weibull distributions. To give a better use of the calculated data, they were applied to the evaluation of a Pumping System.展开更多
A new simulation strategy is proposed for the starting process of missile turbojet engine windmill. The starting process of windmill before ignition is simulated using a radial basis function neural network (RBFNN) , ...A new simulation strategy is proposed for the starting process of missile turbojet engine windmill. The starting process of windmill before ignition is simulated using a radial basis function neural network (RBFNN) , and the acceleration process after ignition which model is a set of nonlinear equations is solved using a particle swarm optimization (PSO) algorithm. The introduction of PSO helped to tackle the problem of divergence caused by traditional iteration methods. The calculated result is in a great agreement with test data, which shows that the presented model has a high accuracy. The starting processes are simulated at different ignition times, and the results are analyzed synthetically. The analysis shows how the ignition time affects the starting performance of engine windmill. The method offers a useful tool for ignition time optimization as well as engine starting performance analysis.展开更多
In the present work,an assessment of the rural water supply potential by mechanical wind pumping around the floodplains of Lake Chad has been considered.Inside the floodplains around Lake Chad,available surface water ...In the present work,an assessment of the rural water supply potential by mechanical wind pumping around the floodplains of Lake Chad has been considered.Inside the floodplains around Lake Chad,available surface water is largely contaminated and represents health hazards to populations.Access to underground and clean water has increasingly become rare.Moreover,clean water scarcity has led to conflict and territorial pressures,which are contributing factors to poverty in the considered area.Four localities,Baga,Baga-Sola,Makari and Nguigmi,respectively,in Nigeria,Chad,Cameroon and Niger have been selected inside the floodplains around Lake Chad,to evaluate the potential of wind power and prospects of windmills development to provide safe drinking-water supply,livestock watering and small-scale irrigation.Long-term satellite-derived data,obtained through the Prediction of Worldwide renewable Energy Resources have been considered suitable and viable alternative to missing site-specific data from ground stations.Windmill of Multi-blade driven piston pump is the preferred water pumping option for this study because of its higher overall system efficiency.The results of this study indicate that mean wind speeds,at 10 m height above ground level,are 4.64 m/s for Baga,4.76 m/s for Baga-Sola,4.32 m/s for Makari and 4.44 m/s for Nguigmi.In addition,wind speeds for Baga,for instance,are in the range of 2.5–10 m(working range of a wind pump),at 10,15,20 and 25 m height agl,for 79.64,82.80,84.79,and 86.19 per cent of the time.Corresponding values for Baga-Sola,Makari and Nguigmi are in the range of 80.50–87.76 per cent,76.86–85,58 per cent,77.92–86.21 per cent,respectively.For a Windmill with a 2 m-blade,a 25 m-height tower and considering a total dynamic head of 30 m,average monthly discharges for the dry season are 1,330,1,374,1,200 and 1,199 m3,respectively for Baga,Baga-Sola,Makari and Nguigmi.Furthermore,corresponding costs of water are 9.53,9.23,10.56 and 10.57 XAF/m3,for Baga,Baga-Sola,Makari and Nguigmi,in that order.展开更多
This study configures a simple wind tunnel using a blower for generating wind energy, which is equivalent to natural wind, and a test system that measures properties of power. Also, the mechanical and electrical power...This study configures a simple wind tunnel using a blower for generating wind energy, which is equivalent to natural wind, and a test system that measures properties of power. Also, the mechanical and electrical power in a small-scaled wind turbine are empirically measured to analyze the relationship between the mechanical and electrical power.展开更多
In order to reasonably explain the phenomenon of cell bioelectricity,we proposed the conservation law of cell membrane area,established the ion inequality equation,and therefore paid attention to the mystery of“θ-τ...In order to reasonably explain the phenomenon of cell bioelectricity,we proposed the conservation law of cell membrane area,established the ion inequality equation,and therefore paid attention to the mystery of“θ-τ”.We researched and analyzed the“θ-τ”mystery,discussed the parity non-conservation in weak interactions,suggested possible experiments to test the parity non-conservation in weak interactions,and gave our research and analysis conclusions:The parity non-conservation in weak interactions,is still a“conjecture”;The experimental scheme suggested in the papers by C.N.Yang et al.cannot determine whether the weak interaction can separate left and right,and it is impossible to directly answer whetherθandτin the“θ-τ”mystery are the same particle;The Co60βdecay experiment such as C.S.Wu is a pseudo-mirror experiment,whether the experimental result violates parity conservation is only based on the assumption of C.N.Yang et al.In fact,experiments such as polarized Co60 did not overturn the so-called“law of parity conservation”.The mirror image principle does not have any physical meaning,does not correspond to any physical conservation quantity,and cannot be destroyed by any physical experiment.In the process of turning“mirror symmetry”and“mirror asymmetry”into so-called physical“common sense”and scientific“facts”respectively,the methods of transformation are“stealing concepts”and“circular argumentation”.The“θ-τ”mystery is a“man-made”mystery.θandτare two different particles,which may be the result of the same precursor particle being divided into two.The work of C.N.Yang,T.D.Lee,C.S.Wu et al.has brought quantum physicists from the“small black room”to the“bigger black room”or“smaller black room”.The right and wise choice is to go back through the door that came in.With the development of science today,it is time for some contents to reform from the bottom.展开更多
The removal of lignin from natural cellulose fibers is a crucial step in preparing high-performance materials,such as compressed high-toughness composites.This process can eliminate non-cellulosic impurities,create ab...The removal of lignin from natural cellulose fibers is a crucial step in preparing high-performance materials,such as compressed high-toughness composites.This process can eliminate non-cellulosic impurities,create abundant compressible pores,and expose a greater number of active functional groups.In this study,biomass waste windmill palm fiber was used as the raw mate-rial to prepare holocellulose fibers through various chemical treatments.The structure,chemical composition,Fourier transform infrared spectroscopy analysis,X-ray diffraction analysis,ther-mal properties,and mechanical properties,particularly fatigue performance,were studied.The sodium chlorite treated fiber had the highest crystallinity index(61.3%)and the most complete appearance structure.The sodium sulfite treated fiber had the highest tensile strength(227.34±52.27)MPa.Hydroxide peroxide treatment removed most of the lignin and hemicellulose,increas-ing the cellulose content to 68.83%±0.65%.However,all the chemical treatments decreased the thermal property of the fibers.展开更多
Performance improvement of existing 200 litres capacity natural convection type domestic solar hot water system is attempted.A two-stage centrifugal pump driven by a vertical axis windmill having Savonius type rotor i...Performance improvement of existing 200 litres capacity natural convection type domestic solar hot water system is attempted.A two-stage centrifugal pump driven by a vertical axis windmill having Savonius type rotor is added to the fluid loop.The windmill driven pump circulates the water through the collector.The system with necessary instrumentation is tested over a day.Tests on Natural Circulation System(NCS)mode and Wind Assisted System(WAS)mode are carried out during January,April,July and October,2009.Test results of a clear day are reported.Daily average efficiency of 25-28% during NCS mode and 33-37% during WAS mode are obtained.With higher wind velocities,higher collector flow rates and hence higher efficiencies are obtained.In general,WAS mode provides improvements in efficiency when compared to NCS mode.展开更多
We present a discovery of an unusual unidirectionally rotating windmill scattering of electromagnetic waves by a magnetized gyromagnetic cylinder via an analytical theory for rigorous solution to fields and charges an...We present a discovery of an unusual unidirectionally rotating windmill scattering of electromagnetic waves by a magnetized gyromagnetic cylinder via an analytical theory for rigorous solution to fields and charges and an understanding of the underlying mathematical and physical mechanisms. Mathematically, the generation of nonzero off-diagonal components can break the symmetry of forward and backward scattering coefficients, producing unidirectional windmill scattering. Physically, this windmill scattering originates from the nonreciprocal unidirectional rotation of polarized magnetic charges on the surface of a magnetized gyromagnetic cylinder, which drives the scattering field to radiate outward in the radial direction and unidirectionally emit in the tangential direction. Interestingly, the unidirectional electromagnetic windmill scattering is insensitive to the excitation direction. Moreover, we also discuss the size dependence of unidirectional windmill scattering by calculating the scattering spectra of the gyromagnetic cylinder. These results are helpful for exploring and understanding novel interactions between electromagnetic waves and gyromagnetic materials or structures and offer deep insights for comprehending topological photonic states in gyromagnetic systems from the aspect of fundamental classical electrodynamics and electromagnetics.展开更多
Micro turbine engine (MTE) is an important kind of propulsion system for miniature unmanned aircraft or missiles, because of its better high-speed performance (than propeller propulsion) and higher propulsion effi...Micro turbine engine (MTE) is an important kind of propulsion system for miniature unmanned aircraft or missiles, because of its better high-speed performance (than propeller propulsion) and higher propulsion efficiency (obviously than rockets). Windmill start is a common air-starting mode used in micro turbine engine. The windmill starting characteristics are important to the practical use of micro turbine engine. In this paper, the windmill starting characteristics research for a 12 cm diameter (MTE-D) micro turbine engine is carried out by experiment and numerical simulation. The characteristic of rotor mechanical losses at low-speed condition is stud- ied, and the engine common working line of windmill starting process is obtained. Based on the engine windmill characteristics, the propane ignition characteristics under different inflow conditions are researched, and the envelope of propane ignition and propane flameout is determined. The experimental research of fuel supply and ignition characteristics is completed, and the envelope of fuel supply and ignition is obtained. The windmill stage, propane ignition stage, fuel ignition stage and acceleration process from idling-speed to 80% full speed of MTE-D micro turbine engine is optimized, and the optimization windmill starting parameters are collected. The successful wind-mill starting experiment under this condition with engine speed up to 80% full speed indicates that these starting parameters are reasonable. All the starting parameters of MTE-D micro turbine engine obtained in this work are dimensionless parameters, and the conclusions obtained in this study have some reference to other micro turbine engines with the similar structural form and starting process.展开更多
文摘The main objective of the present paper is to review the specific characteristics and performance obtaining conditions of heavy ductile iron(DI) castings,typically applied in windmills industry,such as hubs and rotor housings.The requirements for high impact properties in DI at low temperatures are part of the ENGJS-400-18U-LT(SRN 1563) commonly referred to as GGG 40.3(DIN 1693).Pearlitic in-uence factor(Px) and antinodularising action factor(K1) were found to have an important in-uence on the structure and mechanical properties,as did Mn and P content,rare earth(RE) addition and inoculation power.The presence of high purity pig iron in the charge is extremely beneficial,not only to control the complex factors Px and K1,but also to improve the 'metallurgical quality' of the iron melt.A correlation of C and Si limits with section modulus is very important to limit graphite nodule flotation.Chunky and surface-degenerated graphite are the most controlled graphite morphologies in windmills castings.The paper concluded on the optimum iron chemistry and melting procedure,Mg-alloys and inoculants peculiar systems,as well as on the practical solutions to limit graphite degeneration and to ensure castings of the highest integrity,typically for this field.
文摘Difficulties in obtaining component characteristics in the sub-idle state of rotor constrain the simulation capabilities of ground and windmill start-up processes for turbofan engines.This paper proposes a backbone feature method based on conventional characteristics parameters to derive the full-state characteristics of fan.The application of the fan’s full-state characteristics in component-level model of turbofan engine enables zero-speed iterative simulation for ground start-up process and windmill simulation for windmill start-up process,thereby improving the simulation capability of sub-idle state during turbofan engine start-up.
文摘A brief description of the windmills from the second millennium BC to the Renaissance is presented. This survey is a part of several studies conducted by the authors on technology in the ancient world. The windmills are the first motor, other than human muscles, and are the ancestors of the modem wind turbines. Some authors' virtual reconstructions of old windmills are also presented. The paper shows that the operating principle of many modem machines had already been conceived in the ancient times by using a technology that was more advanced than expected, but with two main differences, as follows: Similar tasks were accomplished by using much less energy; and the environmental impact was nil or very low. Modem designers should sometimes consider simplicity rather than the use of a large amount of energy.
文摘Let G be a graph. A bipartition of G is a bipartition of V (G) with V (G) = V<sub>1</sub> ∪ V<sub>2</sub> and V<sub>1</sub> ∩ V<sub>2</sub> = ∅. If a bipartition satisfies ∥V<sub>1</sub>∣ - ∣V<sub>2</sub>∥ ≤ 1, we call it a bisection. The research in this paper is mainly based on a conjecture proposed by Bollobás and Scott. The conjecture is that every graph G has a bisection (V<sub>1</sub>, V<sub>2</sub>) such that ∀v ∈ V<sub>1</sub>, at least half minuses one of the neighbors of v are in the V<sub>2</sub>;∀v ∈ V<sub>2</sub>, at least half minuses one of the neighbors of v are in the V<sub>1</sub>. In this paper, we confirm this conjecture for some bipartite graphs, crown graphs and windmill graphs.
文摘Taking the model for propeller transport aircraft as the research object,according to the transient windmill characteristics in the process of stop feathering and starting in the air,the simulation calculation of different flight heights,blade angles and rotation speeds was carried out,and the transient windmill resistance of the propeller was quantitatively given.The engine torque was calculated by using the simulation model are compared and verified using the flight test data,and the maximum error was 74%.In the windmill state,the airflow works on the propeller,and the airflow velocity behind the propeller disk decreases,wrapping the entire nacelle surface.In the process of parking feathering,the blade angle decreases slightly at first,and then increases rapidly under the action of the large⁃pitch oil pressure,and the speed of rotation increases gradually.When the blade angle at 30°,the windmill resistance at-108 kgf.In the process of starting,the propeller speed increases and the propeller resistance increases first and decreases.When the propeller returns to 14°,the transient windmill resistance at-1720 kgf.
文摘Ground based, wind energy extraction systems have reached their maximum capability. The limitations of current de-signs are: wind instability, high cost of installations, and small power output of a single unit. The wind energy industry needs of revolutionary ideas to increase the capabilities of wind installations. This article suggests a revolutionary innovation which produces a dramatic increase in power per unit and is independent of prevailing weather and at a lower cost per unit of energy extracted. The main innovation consists of large free-flying air rotors positioned at high altitude for power and air stream stability, and an energy cable transmission system between the air rotor and a ground based electric generator. The air rotor system flies at high altitude up to 14 km. A stability and control is provided and systems enable the changing of altitude. This article includes six examples having a high unit power output (up to 100 MW). The proposed examples provide the following main advantages: 1) Large power production capacity per unit—up to 5,000 - 10,000 times more than conventional ground-based rotor designs;2) The rotor operates at high altitude of 1 - 14 km, where the wind flow is strong and steady;3) Installation cost per unit energy is low;4) The installation is environmentally friendly (no propeller noise).
文摘An investigation was conducted to install wind farm to supply electrical power to the village of Ras Munif, the highest elevation in Jordan. The village installed capacity load was found to be 500 kW. A 25 windmills, 20 kW each, forming the wind farm was found to be the best choice to supply the village with 100% of its needed power. The windmills will be spaced 50 meters along an unobstructed continuous wind flow location, along sloping sides of Ras Munif Mountain, alongside service road. The village load bus will be connected directly to both the output of wind farm inverter output bus and to the national grid bus. Both buses supply the needed power. The power flow was found to be supplied by the wind farm, except when the wind speed is low, the village load will be supplied partially or totally by the national grid bus.
文摘Given the steady increase in use of alternative energy sources to supply part of the energy demand of the world, and considering that Mexico has enough wind resources to produce all the electricity required by the country, in this work, it is carried out the development of a system of wind resource assessment to determine the volume of water that a windmill pumping system can provide in a specific area. To this end, it has developed a computer program for wind resource assessment by measurements of wind speed, direction, temperature, barometric pressure and relative humidity. Measuring equipments were mounted in a wind measurement tower of 10 m high, within the premises of the University of Quintana Roo which is located along the coast. Until this day, there are records over a period of five months of the variables of wind speed, wind direction, temperature, relative humidity and atmospheric pressure. These variables were used for statistical calculations using the Weibull distributions. To give a better use of the calculated data, they were applied to the evaluation of a Pumping System.
基金Sponsored by the National Aeronautical Science Foundation of China(20095584006)
文摘A new simulation strategy is proposed for the starting process of missile turbojet engine windmill. The starting process of windmill before ignition is simulated using a radial basis function neural network (RBFNN) , and the acceleration process after ignition which model is a set of nonlinear equations is solved using a particle swarm optimization (PSO) algorithm. The introduction of PSO helped to tackle the problem of divergence caused by traditional iteration methods. The calculated result is in a great agreement with test data, which shows that the presented model has a high accuracy. The starting processes are simulated at different ignition times, and the results are analyzed synthetically. The analysis shows how the ignition time affects the starting performance of engine windmill. The method offers a useful tool for ignition time optimization as well as engine starting performance analysis.
文摘In the present work,an assessment of the rural water supply potential by mechanical wind pumping around the floodplains of Lake Chad has been considered.Inside the floodplains around Lake Chad,available surface water is largely contaminated and represents health hazards to populations.Access to underground and clean water has increasingly become rare.Moreover,clean water scarcity has led to conflict and territorial pressures,which are contributing factors to poverty in the considered area.Four localities,Baga,Baga-Sola,Makari and Nguigmi,respectively,in Nigeria,Chad,Cameroon and Niger have been selected inside the floodplains around Lake Chad,to evaluate the potential of wind power and prospects of windmills development to provide safe drinking-water supply,livestock watering and small-scale irrigation.Long-term satellite-derived data,obtained through the Prediction of Worldwide renewable Energy Resources have been considered suitable and viable alternative to missing site-specific data from ground stations.Windmill of Multi-blade driven piston pump is the preferred water pumping option for this study because of its higher overall system efficiency.The results of this study indicate that mean wind speeds,at 10 m height above ground level,are 4.64 m/s for Baga,4.76 m/s for Baga-Sola,4.32 m/s for Makari and 4.44 m/s for Nguigmi.In addition,wind speeds for Baga,for instance,are in the range of 2.5–10 m(working range of a wind pump),at 10,15,20 and 25 m height agl,for 79.64,82.80,84.79,and 86.19 per cent of the time.Corresponding values for Baga-Sola,Makari and Nguigmi are in the range of 80.50–87.76 per cent,76.86–85,58 per cent,77.92–86.21 per cent,respectively.For a Windmill with a 2 m-blade,a 25 m-height tower and considering a total dynamic head of 30 m,average monthly discharges for the dry season are 1,330,1,374,1,200 and 1,199 m3,respectively for Baga,Baga-Sola,Makari and Nguigmi.Furthermore,corresponding costs of water are 9.53,9.23,10.56 and 10.57 XAF/m3,for Baga,Baga-Sola,Makari and Nguigmi,in that order.
文摘This study configures a simple wind tunnel using a blower for generating wind energy, which is equivalent to natural wind, and a test system that measures properties of power. Also, the mechanical and electrical power in a small-scaled wind turbine are empirically measured to analyze the relationship between the mechanical and electrical power.
文摘In order to reasonably explain the phenomenon of cell bioelectricity,we proposed the conservation law of cell membrane area,established the ion inequality equation,and therefore paid attention to the mystery of“θ-τ”.We researched and analyzed the“θ-τ”mystery,discussed the parity non-conservation in weak interactions,suggested possible experiments to test the parity non-conservation in weak interactions,and gave our research and analysis conclusions:The parity non-conservation in weak interactions,is still a“conjecture”;The experimental scheme suggested in the papers by C.N.Yang et al.cannot determine whether the weak interaction can separate left and right,and it is impossible to directly answer whetherθandτin the“θ-τ”mystery are the same particle;The Co60βdecay experiment such as C.S.Wu is a pseudo-mirror experiment,whether the experimental result violates parity conservation is only based on the assumption of C.N.Yang et al.In fact,experiments such as polarized Co60 did not overturn the so-called“law of parity conservation”.The mirror image principle does not have any physical meaning,does not correspond to any physical conservation quantity,and cannot be destroyed by any physical experiment.In the process of turning“mirror symmetry”and“mirror asymmetry”into so-called physical“common sense”and scientific“facts”respectively,the methods of transformation are“stealing concepts”and“circular argumentation”.The“θ-τ”mystery is a“man-made”mystery.θandτare two different particles,which may be the result of the same precursor particle being divided into two.The work of C.N.Yang,T.D.Lee,C.S.Wu et al.has brought quantum physicists from the“small black room”to the“bigger black room”or“smaller black room”.The right and wise choice is to go back through the door that came in.With the development of science today,it is time for some contents to reform from the bottom.
基金funded by the special fund support for basic scientific research business expenses of central universities (no.2232023G-01)the basalt fiber and composite key laboratory of Sichuan province Dazhou Research Institute of Basalt Fiber Industry (no.XXFC-2201)the Opening Project of National Engineering Laboratory for Modern Silk,Soochow University (no.SDGC2244).
文摘The removal of lignin from natural cellulose fibers is a crucial step in preparing high-performance materials,such as compressed high-toughness composites.This process can eliminate non-cellulosic impurities,create abundant compressible pores,and expose a greater number of active functional groups.In this study,biomass waste windmill palm fiber was used as the raw mate-rial to prepare holocellulose fibers through various chemical treatments.The structure,chemical composition,Fourier transform infrared spectroscopy analysis,X-ray diffraction analysis,ther-mal properties,and mechanical properties,particularly fatigue performance,were studied.The sodium chlorite treated fiber had the highest crystallinity index(61.3%)and the most complete appearance structure.The sodium sulfite treated fiber had the highest tensile strength(227.34±52.27)MPa.Hydroxide peroxide treatment removed most of the lignin and hemicellulose,increas-ing the cellulose content to 68.83%±0.65%.However,all the chemical treatments decreased the thermal property of the fibers.
文摘Performance improvement of existing 200 litres capacity natural convection type domestic solar hot water system is attempted.A two-stage centrifugal pump driven by a vertical axis windmill having Savonius type rotor is added to the fluid loop.The windmill driven pump circulates the water through the collector.The system with necessary instrumentation is tested over a day.Tests on Natural Circulation System(NCS)mode and Wind Assisted System(WAS)mode are carried out during January,April,July and October,2009.Test results of a clear day are reported.Daily average efficiency of 25-28% during NCS mode and 33-37% during WAS mode are obtained.With higher wind velocities,higher collector flow rates and hence higher efficiencies are obtained.In general,WAS mode provides improvements in efficiency when compared to NCS mode.
基金This work was supported by the National Natural Science Foundation of China(Nos.11974119 and 12074127)Science and Technology Project of Guangdong(No.2020B010190001)+2 种基金Science and Technology Program of Guangzhou(No.201904010105)Guangdong Innovative and Entrepreneurial Research Team Program(No.2016ZT06C594)National Key R&D Program of China(No.2018YFA0306200).
文摘We present a discovery of an unusual unidirectionally rotating windmill scattering of electromagnetic waves by a magnetized gyromagnetic cylinder via an analytical theory for rigorous solution to fields and charges and an understanding of the underlying mathematical and physical mechanisms. Mathematically, the generation of nonzero off-diagonal components can break the symmetry of forward and backward scattering coefficients, producing unidirectional windmill scattering. Physically, this windmill scattering originates from the nonreciprocal unidirectional rotation of polarized magnetic charges on the surface of a magnetized gyromagnetic cylinder, which drives the scattering field to radiate outward in the radial direction and unidirectionally emit in the tangential direction. Interestingly, the unidirectional electromagnetic windmill scattering is insensitive to the excitation direction. Moreover, we also discuss the size dependence of unidirectional windmill scattering by calculating the scattering spectra of the gyromagnetic cylinder. These results are helpful for exploring and understanding novel interactions between electromagnetic waves and gyromagnetic materials or structures and offer deep insights for comprehending topological photonic states in gyromagnetic systems from the aspect of fundamental classical electrodynamics and electromagnetics.
文摘Micro turbine engine (MTE) is an important kind of propulsion system for miniature unmanned aircraft or missiles, because of its better high-speed performance (than propeller propulsion) and higher propulsion efficiency (obviously than rockets). Windmill start is a common air-starting mode used in micro turbine engine. The windmill starting characteristics are important to the practical use of micro turbine engine. In this paper, the windmill starting characteristics research for a 12 cm diameter (MTE-D) micro turbine engine is carried out by experiment and numerical simulation. The characteristic of rotor mechanical losses at low-speed condition is stud- ied, and the engine common working line of windmill starting process is obtained. Based on the engine windmill characteristics, the propane ignition characteristics under different inflow conditions are researched, and the envelope of propane ignition and propane flameout is determined. The experimental research of fuel supply and ignition characteristics is completed, and the envelope of fuel supply and ignition is obtained. The windmill stage, propane ignition stage, fuel ignition stage and acceleration process from idling-speed to 80% full speed of MTE-D micro turbine engine is optimized, and the optimization windmill starting parameters are collected. The successful wind-mill starting experiment under this condition with engine speed up to 80% full speed indicates that these starting parameters are reasonable. All the starting parameters of MTE-D micro turbine engine obtained in this work are dimensionless parameters, and the conclusions obtained in this study have some reference to other micro turbine engines with the similar structural form and starting process.