Automated over-tree sprinkler irrigation systems were developed and tested in two orchards located in two separate locations in southern Iran （a 0.17 ha peach orchard and a 0.24 ha orange orchard） to protect peach b...Automated over-tree sprinkler irrigation systems were developed and tested in two orchards located in two separate locations in southern Iran （a 0.17 ha peach orchard and a 0.24 ha orange orchard） to protect peach blossoms and orange trees leaves and fruits from low temperature damage. The experiment used a system that monitored the trees and air temperatures using two thermistors. The water application rate by the irrigation system was determined by an energy balance as implemented by the software FROSTPRO, In the peach orchard, the system was tested during three frost events during the spring of 2003 and three other events during the spring of 2004. The system successfully kept peach flowers above the critical temperature, i.e., -4.0℃ in spring 2004 （control block -4.12℃, and sprinkled block ＋0.5℃） during all events. Similar results were obtained in the orange orchard during three frost events in the winter of 2004, during which the tree temperatures were at least 2.5℃ above the critical temperature. Results from field tests show that the system can effectively protect the peach blossoms from damage. Determination done after the frost events showed a 12% blossom kill in the sprinkled blocks while in the unsprinkled control block a 41.5% blossom kill. Calculations indicated that when using variable application rates, the amount of water used can be reduced by 54.3%. Spatial distribution of minimum temperatures during the three frosts was also studied in Jahrom, Iran. Results showed a significant temperature control in the experimental block, especially in the central part of the orchard, but the block margins （about 3.6% of the total area） were at the risk of low temperature due to the wind drift effects.展开更多
To determine proper flight parameters of an unmanned helicopter for tea plantation frost protection,field experiments were conducted to study the impact of flight height,speed and interval on airflow disturbance and t...To determine proper flight parameters of an unmanned helicopter for tea plantation frost protection,field experiments were conducted to study the impact of flight height,speed and interval on airflow disturbance and temperature rise around tea canopies based on the analysis and simulation of frost protection with a certain helicopter.The relationship between temperature rise after flight and the above flight parameters was established through a regression orthogonal experiment,based on which the optimal combination of flight parameters was obtained through the single-factor golden section method.The results showed that wind speed around tea canopies decreased with the increase of flight height when flight speed was constant.There was a multivariate linear relationship between temperature rise and flight parameters,and the sequence of flight parameters’influence on frost protection effect was flight interval,flight height,flight speed.The optimal combination of flight parameters were flight height of 4.0 m,flight speed of 6.0 m/s and flight interval of 20 min.After the flight with the above parameters air temperature around tea canopies increased 1.6℃ when background thermal inversion strength was 3.8℃.展开更多
Confronted with severe frost damage to plants,methods,technologies and equipment have been developed and applied during the past century.The paper presents a comprehensive review on the most effective and active techn...Confronted with severe frost damage to plants,methods,technologies and equipment have been developed and applied during the past century.The paper presents a comprehensive review on the most effective and active technology to protect plants from radiation frost based on air disturbance technology.The working principle of the technology was elaborated with frost protection mechanism,structures and applicability of three types of working patterns:conventional wind machines,selective inverted sink and portable vertical blowing.As an automatic mechanized technology,control strategy,applicable occasion and proper parameters are introduced for each type of working pattern.The operation of the technology and equipment depends on plant critical temperature,prevailing climatic conditions,thermal inversions strength,as well as costs.The frost protection performance and effectiveness of conventional horizontal wind machines,selective inverted sinks and helicopters are discussed and compared from the cost-effectiveness and application aspects,and the feasibility of selective inverted sinks is still controversial.Therefore,conventional wind machines are the best choice for plant frost protection and consequently are widely used in temperate and subtropical areas throughout the world.The frost protection application with helicopters is not easy to use during the frost nights with high cost.The paper also provides researchers with some perspectives on improving air disturbance technology and its equipment,and some practice recommendations for growers.展开更多
Wind machines have been increasingly applied to prevent frost damage through airflow disturbance in tea fields and orchards.An impeller is the most important component of the machine.However,there are few studies on c...Wind machines have been increasingly applied to prevent frost damage through airflow disturbance in tea fields and orchards.An impeller is the most important component of the machine.However,there are few studies on customized impeller design or airflow disturbance performance.The objective of this study was to design a new impeller for frost protection wind machines based on reverse engineering and CFD simulation.The characteristic parameters of an impeller include blade cross-section shape,installation angle,sweep angle,hub ratio and blade number.The optimal combination of the above parameters was obtained through the simulation of the impeller’s aerodynamic performance.Field tests were conducted in a tea field to evaluate airflow disturbance performance of the designed impeller.The result shows that at a certain rotation speed and rotation diameter,the optimal combination of impeller parameters was:single arc cross-section ofϕ2400 mm,installation angle of 15°,sweep angle of 87°,hub ratio of 0.3 and blade number of 4,of which the impeller could achieve the highest usage of 0.56,the least consumed power of 1.363 kW and more uniform distribution of surface pressure on the windward side.Compared with other commercial frost protection wind machines,the maximum airflow velocity of the developed impeller was higher at 12 m in front of it.The probability of airflow velocity above 3.0 m/s within 30 min was the highest(71.7%),indicating its improvement of airflow stability.Without swing the new impeller could cover an effective area of 300 m2,which was similar to that of the commercial ones.展开更多
文摘Automated over-tree sprinkler irrigation systems were developed and tested in two orchards located in two separate locations in southern Iran （a 0.17 ha peach orchard and a 0.24 ha orange orchard） to protect peach blossoms and orange trees leaves and fruits from low temperature damage. The experiment used a system that monitored the trees and air temperatures using two thermistors. The water application rate by the irrigation system was determined by an energy balance as implemented by the software FROSTPRO, In the peach orchard, the system was tested during three frost events during the spring of 2003 and three other events during the spring of 2004. The system successfully kept peach flowers above the critical temperature, i.e., -4.0℃ in spring 2004 （control block -4.12℃, and sprinkled block ＋0.5℃） during all events. Similar results were obtained in the orange orchard during three frost events in the winter of 2004, during which the tree temperatures were at least 2.5℃ above the critical temperature. Results from field tests show that the system can effectively protect the peach blossoms from damage. Determination done after the frost events showed a 12% blossom kill in the sprinkled blocks while in the unsprinkled control block a 41.5% blossom kill. Calculations indicated that when using variable application rates, the amount of water used can be reduced by 54.3%. Spatial distribution of minimum temperatures during the three frosts was also studied in Jahrom, Iran. Results showed a significant temperature control in the experimental block, especially in the central part of the orchard, but the block margins （about 3.6% of the total area） were at the risk of low temperature due to the wind drift effects.
基金The authors are grateful to the financial support by National High Technology Research and Development Program of China(2012AA10A508)National Natural Science Foundation of China(31101089)Priority Academic Program Development of Jiangsu Higher Education Institutions(2014-37)。
文摘To determine proper flight parameters of an unmanned helicopter for tea plantation frost protection,field experiments were conducted to study the impact of flight height,speed and interval on airflow disturbance and temperature rise around tea canopies based on the analysis and simulation of frost protection with a certain helicopter.The relationship between temperature rise after flight and the above flight parameters was established through a regression orthogonal experiment,based on which the optimal combination of flight parameters was obtained through the single-factor golden section method.The results showed that wind speed around tea canopies decreased with the increase of flight height when flight speed was constant.There was a multivariate linear relationship between temperature rise and flight parameters,and the sequence of flight parameters’influence on frost protection effect was flight interval,flight height,flight speed.The optimal combination of flight parameters were flight height of 4.0 m,flight speed of 6.0 m/s and flight interval of 20 min.After the flight with the above parameters air temperature around tea canopies increased 1.6℃ when background thermal inversion strength was 3.8℃.
基金The authors are grateful to the financial support by Jiangsu Agriculture Science and Technology Innovation Fund(CX(16)1045)Key R&D programs of Jiangsu Province and Zhenjiang(BE2016354,NY20160120037)+1 种基金China and Jiangsu postdoctoral science foundations(2016M600376,1601032C)Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Confronted with severe frost damage to plants,methods,technologies and equipment have been developed and applied during the past century.The paper presents a comprehensive review on the most effective and active technology to protect plants from radiation frost based on air disturbance technology.The working principle of the technology was elaborated with frost protection mechanism,structures and applicability of three types of working patterns:conventional wind machines,selective inverted sink and portable vertical blowing.As an automatic mechanized technology,control strategy,applicable occasion and proper parameters are introduced for each type of working pattern.The operation of the technology and equipment depends on plant critical temperature,prevailing climatic conditions,thermal inversions strength,as well as costs.The frost protection performance and effectiveness of conventional horizontal wind machines,selective inverted sinks and helicopters are discussed and compared from the cost-effectiveness and application aspects,and the feasibility of selective inverted sinks is still controversial.Therefore,conventional wind machines are the best choice for plant frost protection and consequently are widely used in temperate and subtropical areas throughout the world.The frost protection application with helicopters is not easy to use during the frost nights with high cost.The paper also provides researchers with some perspectives on improving air disturbance technology and its equipment,and some practice recommendations for growers.
基金The authors are grateful to the financial support by National High Technology Research and Development Program of China(2012AA10A508)Special Fund of Non-profit Scientific Research for Agriculture(201303012)Priority Academic Program Development of Jiangsu Higher Education Institutions(2014-37).
文摘Wind machines have been increasingly applied to prevent frost damage through airflow disturbance in tea fields and orchards.An impeller is the most important component of the machine.However,there are few studies on customized impeller design or airflow disturbance performance.The objective of this study was to design a new impeller for frost protection wind machines based on reverse engineering and CFD simulation.The characteristic parameters of an impeller include blade cross-section shape,installation angle,sweep angle,hub ratio and blade number.The optimal combination of the above parameters was obtained through the simulation of the impeller’s aerodynamic performance.Field tests were conducted in a tea field to evaluate airflow disturbance performance of the designed impeller.The result shows that at a certain rotation speed and rotation diameter,the optimal combination of impeller parameters was:single arc cross-section ofϕ2400 mm,installation angle of 15°,sweep angle of 87°,hub ratio of 0.3 and blade number of 4,of which the impeller could achieve the highest usage of 0.56,the least consumed power of 1.363 kW and more uniform distribution of surface pressure on the windward side.Compared with other commercial frost protection wind machines,the maximum airflow velocity of the developed impeller was higher at 12 m in front of it.The probability of airflow velocity above 3.0 m/s within 30 min was the highest(71.7%),indicating its improvement of airflow stability.Without swing the new impeller could cover an effective area of 300 m2,which was similar to that of the commercial ones.
